Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
203 PM EDT Wed Oct 28 2026

Valid 00Z Thu Oct 29 2026 - 00Z Sat Oct 31 2026

...Heavy rainfall and flash flooding threats to expand across the Southern
High Plains and Southwest through Friday...

...A progressive cold front will bring showers and thunderstorms from the
Mississippi Valley to parts of the Northeast...

...Accumulating mountain snow in the Cascades and Northern Rockies while
unseasonable warmth dominates the East...

A multi-day heavy rainfall and flash flooding threat will unfold across
portions of the Southern High Plains and Southwest through the end of the
week. An upper-level trough anchored over the Western U.S. will allow for
favorable large-scale ascent across the southern tier, while a
southern-stream jet streak provides divergence aloft. Concurrently, a
southerly low-level jet will bring abundant moisture from the Gulf,
driving high precipitable water across western Texas. Favorable lift and a
concomitant influx of deep moisture will support widespread showers and
thunderstorms across West and Central Texas into the Southern High Plains
on Thursday. Convective rain rates reaching 1.5 to 2.5 inches per hour
will be capable of producing localized to scattered flash flooding,
particularly across urban drainages, low-lying areas, and sensitive
terrain. As such, there is a high-end Slight Risk (level 2/4) of excessive
rainfall across portions of West and Central Texas on Thursday, with a
Marginal Risk (level 1/4) extending into southern New Mexico. By Friday, a
secondary surge of moisture originating from the Gulf of California will
overspread the Desert Southwest ahead of the advancing upper trough. Heavy
showers and thunderstorms will focus across central and southern Arizona,
where terrain-induced lift and saturated soils will heighten runoff
potential. Consequently, a Slight Risk (level 2/4) of excessive rainfall
is in effect for central and southern Arizona on Friday, where repeated
rounds of rainfall will carry a risk of scattered flash flooding across
steep terrain, narrow canyons, and recent burn scars.

Farther north and east, an advancing surface cold front will progress
across the eastern half of the nation from Thursday into Friday. Supported
by a mid-level shortwave trough tracking along the international border,
the front will push across the Mid-Mississippi Valley and Central Plains
early Thursday morning before entering the Great Lakes and Ohio Valley
Thursday afternoon. The cold front will then press into the Lower Great
Lakes and interior Northeast by Thursday evening. The boundary will
gradually decelerate as it approaches the Atlantic coast by Friday night,
maintaining scattered showers along coastal sectors while high pressure
building across the northern midsection ushers in a noticeably drier air
mass.

Across the Northwest, persistent onshore flow associated with a
slow-moving surface frontal system will bring widespread precipitation
into the Pacific Northwest, Northern Great Basin, and Northern Rockies
through Friday. Accumulating snow is expected across the higher elevations
of the Washington and Oregon Cascades, where several inches of wet snow
will create slick travel over mountain passes. High-elevation snow and a
wintry mix will also extend into portions of the Northern Rockies.

In terms of temperatures, an amplified upper-level ridge positioned along
the East Coast will bring unseasonable warmth, driving afternoon highs 10
to 20 degrees above seasonal averages. Highs in the 70s and lower 80s are
expected from the Ohio Valley through the Mid-Atlantic and Southeast. In
sharp contrast, a Canadian air mass settling behind the departing cold
front will hold daytime maximums in the 40s and 50s across the Northern
Plains and Upper Midwest. Meanwhile, extensive cloud cover and
precipitation will suppress daytime temperatures across the Great Basin
and Southwest, keeping conditions well below late October averages.


Blanco-Alcala


Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
347 PM EDT Wed Oct 28 2026

Valid 12Z Sat Oct 31 2026 - 12Z Wed Nov 04 2026


...Storm system will bring precipitation across the West this
weekend and into the central U.S. Monday-Tuesday...


...Overview...

Over the weekend, a shortwave or two will push through a warm mean
upper ridge in the eastern half of the U.S., combining with
Pacific tropical and Gulf moisture. This will spread rain and
thunderstorms across the Mississippi Valley and East, with moderate
to heavy rain totals possible in the southern tier. Meanwhile, a
large upper trough is forecast to move through the West and bring
widespread precipitation to include heavy rain/runoff and elevation
heavy snow threats there over the weekend. Forecast models
indicate the upper trough should make its way east and likely
become a closed low when it reaches the Plains by Monday-Tuesday.
This should carry a surface low/frontal system and bring widespread
rain to the central U.S. early next week.


...Guidance/Predictability Assessment...

Model guidance is generally agreeable with the large scale pattern
described above, though with differences in the details that will
affect sensible weather. There is typical model spread with the
shortwaves moving through the central and eastern U.S. this
weekend. Recent GFS and to a lesser degree GEFS runs track the
resulting QPF faster across the Southeast and more northeastward up
the East Coast in contrast to non-NCEP guidance and even the AI-
GFS, so this was not favored by WPC after collaboration with
selected Southeast U.S. WFOs. The lastest 12 UTC GFS has trended
toward the favored concensus, bolstering forecast confidence.

Farther west, it remains questionable how exactly northern and
southern streams interact and combine within the eastern
Pacific/West trough over the weekend. However, guidance remains
overall agreeable that the trough should track east across the
Intermountain West Monday and develop a closed low later Monday
into Tuesday as it reaches the Plains. There is some model spread
in the exact position in this upper low position and deepening
surface low Monday-Tuesday, but clustering is better than normal.

The WPC forecast favored a multi-model, ensemble mean and
dynamical/AI blend through the medium range period, albeit
accordingly discounting recent runs of the GFS/GEFS.


...Weather/Hazards Highlights...

Rain and thunderstorms are likely across the Lower Mississippi
Valley to Southeast over the weekend, and locally heavy rainfall is
possible as ample moisture combines with the shortwave aloft.A WPC
Excessive Rainfall Outlook Marginal Risk threat area shows focus
over the central Gulf Coast states with system genesis and slow
passage. Rain could also spread across the Midwest to Ohio Valley
and eventually into the dammed high pressure cooled East, with
generally modest amounts.

Ample moisture will spread into California/Southwest and the
Intermountain West ahead of the upper trough over the weekend. This
system offers quite anomalous fueling moisture. Accordingly, heavy
rain is possible especially across the Southwest, while heavy snow
is possible in the higher elevations, particularly the San Juans
and central Rockies in Colorado. WPC Excessive Rainfall Outlook
Marginal and embedded Slight Risk areas are in place over the
weekend. However, the details of precipitation timing and
placement, type (including snow levels), and amounts are all
somewhat uncertain dependent on upper-level and surface flow model
differences, so continue to monitor future forecasts as the details
could change. Some rain should overspread much of the central U.S.
later on Sunday and especially Monday as the low strengthens,
including possibly heavy convective amounts. Some northern/central
High Plains snow or rain/snow mix cannot be ruled out on the
backside of the low. Additionally, gusty winds may be possible in
the Plains behind the reasonably strong surface low. Moderate to
heavy rain may persist into Tuesday with some shift east, with
continued uncertainty in the details.

Above average temperatures are expected for much of the central
and eastern U.S. under mean upper ridging (albeit with occasional
shortwaves) over the weekend into early next week. Highs in the 70s
are forecast as far north as the Ohio Valley at times, as broad
areas reach around 10-20 degrees above normal. Temperatures should
be somewhat below average in the western U.S. underneath the upper
trough, especially for highs. By Tuesday-Wednesday, the Plains
should moderate to near normal temperatures as that upper
trough/low moves eastward.


Tate/Schichtel


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast, excessive rainfall outlook,
winter weather outlook probabilities, heat indices and Key Messages
are at:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw

Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
533 AM EDT Wed Oct 28 2026

Valid 00Z Thu 29 Oct 2026 - 00Z Thu 05 Nov 2026

Impactful weather will impact portions of the state the next
couple of days. There are several favorable ingredients for heavy
rainfall with this system. A weak wave of low pressure moving
across today will locally enhance convergence and low level
southwesterly moisture transport. Synoptic forcing will be strong
with favorable right entrance region upper jet dynamics. An axis
of PWs around 2.5" will move towards the state, values that are
near record values for the time of year. Up to around 1000 J/kg of
CAPE is forecast at times, which given the dynamics and strong
low level convergence, is plenty to support at least some
thunderstorm development. One round of more concentrated rain and
embedded thunderstorms will impact the state through this morning.
Additional showers and embedded thunderstorms are likely to
increase in coverage again by later today into early Thursday.
Periods of heavier convective rainfall rates of 1-2"/hr are
likely, with areas of locally significant flash flooding possible.
The heaviest rainfall axis still looks to generally align from
Oahu to Maui.

The coverage of rainfall should decrease some by later Thursday
into Friday, however elevated PWs and some instability will
persist. By Thursday night into Friday the main focus for periods
of heavy rainfall should shift to the typically favored windward
areas of Maui and the Big Island.

Model trends favor a lowering of PWs from north to south by late
this weekend into next week. This should result in a decrease in
rainfall coverage and intensity although windward showers will
likely continue with northeasterly trade winds enhanced by a
frontal passage Sunday into Monday.

Chenard

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
346 PM EDT Wed Oct 28 2026
Day 1
Valid 16Z Wed Oct 28 2026 - 12Z Thu Oct 29 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR EAST-CENTRAL
FLORIDA...

...East Coast of Florida...

16Z Update:

Inherited forecast and outlook area is in excellent shape with no
significant adjustments needed.

Taylor

---previous discussion---

An area of low pressure near the Bahamas will shift southeast
towards the Straights of Florida while the upper level energy with
the system splits off to the northeast. This will result in another
day of northeasterly flow with embedded showers and storms moving
onshore along the Florida East Coast. Moisture wrapping around the
northern side of the low circulation will shift north and increase
PWATs to around 2 inches across East-Central Florida. The
environment will also become unstable as the surface low shifts
southeast and MUCAPE values rise to 800-1200 J/kg in Central and
South Florida, which will support deeper convection capable of
producing high rainfall rates (1.5-2.5 inches per hour) at times.
Hi-res and global models are in agreement that the highest rainfall
totals should materialize near the East-Central Florida Coast,
with some earlier convection capable of producing locally heavy
rainfall over portions of Southeast Florida as well. Given the
prolonged period of northeasterly flow with coastal showers and the
sensitivity of the urban I-95 corridor, there is a Marginal Risk
of excessive rainfall for portions of East-Central Florida where
isolated instances of flash flooding will be possible.

Dolan


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
346 PM EDT Wed Oct 28 2026
Day 2
Valid 12Z Thu Oct 29 2026 - 12Z Fri Oct 30 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
WEST AND CENTRAL TEXAS...

...Texas and New Mexico...

Conditions will be favorable for widespread convection across
portions of Texas and New Mexico on Thursday as mid-level energy
associated with the remnants of TC Vance move into the region. As
the wave approaches, southeasterly low-level flow will bring
anomalous Gulf moisture into the south-central U.S., increasing
PWATs across Texas to 1.5-2 inches, which is well above normal for
this time of year. In addition to mid-level destabilization from
the wave, enhanced upper level divergence in the right entrance
region of a southern stream jet will support a broad region of
ascent across Texas. These ingredients combined with at least
modest CAPE (slightly limited due to widespread cloud cover) are
expected to support an organized heavy rainfall event.

Model guidance continues to trend north and west with the QPF
footprint of this event, which has resulted in a northward
expansion of the preexisting Slight Risk area across portions of
West and Central Texas. There is good agreement from model guidance
showing the heaviest precipitation totals (2-4 inches, locally
higher) focusing between the Stockton and Edwards Plateaus and the
Midland area. This cycle's HREF guidance pointed to at least
moderate probabilities for 3 inches in this area but dropped off
to less than 15 percent for 5 inches. Rainfall rates of 1 to 2
inches per hour (locally higher) will be possible within the Slight
Risk area. There was not enough of a signal to introduce a
Moderate Risk this cycle, moreso due to the general lower
confidence in more extreme rainfall totals or rates.

Surrounding the Slight Risk area, there is a broader Marginal Risk
area that covers much of the western half of Texas to account for
locally heavy rainfall potential extending further north and west.
The Marginal Risk also includes southern New Mexico where the
combination of Gulf and Pacific moisture will allow for scattered
to widespread convection, and there should be sufficient CAPE to
allow for locally heavy rainfall rates. Locally heavy rainfall over
sensitive terrain and burn scars could cause flash flooding,
especially considering how saturated soils are after recent heavy
rains in this region.

Dolan/Taylor


Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
346 PM EDT Wed Oct 28 2026
Day 3
Valid 12Z Fri Oct 30 2026 - 12Z Sat Oct 31 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL AND SOUTHERN ARIZONA...

...Southwest...

Broad troughing will move into the western U.S. with embedded
shortwave energy moving across portions of the Southwest on Friday.
Meanwhile, a strong southern stream jet will approach Baja
California, placing Arizona under the favorable left exit region
with enhanced upper level divergence. Southerly low-level flow will
direct Pacific moisture into the area as well, bringing PWATs up
to 1-1.4 inches across the southern half of Arizona (2-3 standard
deviations above normal). This warm, moist air mass will also
increase instability, with MUCAPE values potentially exceeding 1000
J/kg across much of southern Arizona. With favorable conditions
throughout the atmospheric column, scattered to widespread
convection is expected to develop with the passing of the upper
shortwave.

Model guidance has been consistently showing elevated
precipitation totals along and south of the Mogollon Rim, and there
is a Slight Risk of excessive rainfall in place that includes most
of central and southern Arizona. The Slight Risk also includes
some of the terrain in southwestern New Mexico that should also see
scattered convection. Persistent showers/storms with moderate to
locally heavy rainfall rates could result in scattered instances of
flash flooding, especially near steep terrain and burn scars. The
risk of flash flooding is also slightly heightened across portions
of Arizona and New Mexico where an anomalously wet pattern has
resulted in increased soil moisture. Much of the southwestern U.S.
is included in a broader Marginal Risk area due to increased
moisture and support for at least isolated to scattered convection,
but the flash flood risk is a bit lower since the best moisture
and instability will be limited to southern Arizona.

...Texas and Oklahoma...

The mid-level circulation associated with the remnants of TC Vance
will continue to move north across the southern and central Plains
on Friday while becoming more organized, which could support a
continued heavy rainfall threat for portions of Texas and Oklahoma.
The southern stream jet should shift north, maintaining favorable
conditions for convection over the area through Friday afternoon.
Anomalous moisture will remain in place across the southern Plains,
but instability may become the limiting factor for heavy rainfall.
The best instability looks to be displaced to the north across the
central Plains and into the Midwest while cloud cover limits
instability to the south. If convection can tap into enough
instability, there will still be at least an isolated risk of flash
flooding across Texas and Oklahoma and even into southern Kansas,
and there is a Marginal Risk in place for isolated to widely
scattered instances of flash flooding.

Dolan/Taylor

Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
346 PM EDT Wed Oct 28 2026
Day 4 and Day 5

Valid 12Z Sat Oct 31 2026 - 12Z Mon Nov 02 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHWEST THIS WEEKEND...

...Southwest...

20Z Update: The general synoptic pattern for the Southwest into
Southern California remains consistent in its presentation with the
latest 12z NWP suite and ML outputs. A high-end scenario for flash
flooding in the D5 time frame (12z Sun - 12z Mon) is increasingly
likely given the progged upper level evolution and anomalous
moisture advection regime slated to impact the region during the
middle to late part of the weekend, extending a bit into early
next week. Recent QPF trends label much of AZ through southern UT
and the Four Corners area as the primary impact points for this
coming event with the greatest PWAT anomalies and positive
vorticity advection moving directly into the region allowing for
widespread heavy rainfall, especially into the terrain with
prevailing upslope flow likely. Ensemble mean QPF is currently
robust at such leads with area wide 1-2" markers showing up in
Mogollon Rim, northern AZ mountains, and the Canyon areas of both
northwest AZ into southern UT. The area out by the Four Corners
towards the San Juans will see another bout of heavy rainfall with
the expansion likely into areas further south towards Navajo
Nation. These areas have already seen multiple moderate to high
impact events the past 2-3 months with one recently causing
significant flash flooding across the above areas. This setup will
likely spur another threat for such a scenario leading to a
heightened risk for upgrades in the coming forecast updates. So
long as the signal remains consistent, the threat will likely trend
towards a more impactful scenario with plenty of guidance leaning
in that direction as of the 12z global deterministic and ensemble
suite.

Kleebauer

..Previous Discussion..

An anomalous and potentially high impact setup is taking shape for
the Southwest as a longwave trough moves into the West Coast this
weekend. The depth of the trough over the eastern Pacific may drop
below the climatological 1st percentile for the time of year. Deep,
broad southwesterly flow downstream of the trough will tap into
subtropical and tropical moisture, driving PW values to near or
even above record values for the time of year. The combination of
strong dynamic forcing and wind fields, and near record caliber
moisture will support a broad swath of moderate to heavy
precipitation, maximized across orographically favored slopes.
Given lingering hydrologic sensitivity from preceding rainfall
across the region, runoff issues and some flooding appears likely
even without significant convective enhancement. Widespread cloud
cover should generally limit destabilization, but if and where
pockets of CAPE are able to develop, a more pronounced flash flood
threat could evolve. Forecast guidance exhibits some convergence,
with the 00z ECMWF and AIGFS tending towards the consistent AIFS
solution. Our preference is in this direction, with less weight
given to the GFS. This model preference paints an overall wetter
and more impactful scenario for the Southwest.

While Saturday (day 4) sits ahead of the strongest synoptic scale
forcing, the anomalous moisture axis will be established. A Slight
risk has been introduced centered across central AZ into southern
NV. Many of these areas will have seen heavy rain and convection
on Friday (day 3), leaving hydrologic conditions more primed.
Although large scale forcing and instability may dip compared to
Friday, persistent 850mb moisture transport and modest instability
should be sufficient to sustain some convection and a continued
isolated to scattered flash flood risk.

Stronger large scale forcing overspreads the region on Sunday (day
5) as the main trough axis approaches, resulting in more widespread
precipitation. While cloud cover will hinder destabilization,
cooling aloft and some cloud breaks should support some
destabilization as the trough axis approaches. The greatest
overlap of forcing, moisture and instability is forecast across
portions of AZ into southern NV and southern UT, where a day 5
Slight risk has been issued. An expansive Marginal risk surrounds
this corridor to account for the broad stratiform rain and lower
rain rates falling over a saturated region. Given the magnitude of
moisture, dynamics and terrain enhancement, the setup has the
potential to produce Moderate risk level impacts if adequate
instability materializes. Trends will be closely monitored over
the coming days.

Confidence is a bit lower over southern CA. Model guidance
indicates that an area of low pressure could enhance the
convective threat and rain rates late Saturday night into Sunday
morning. Because this straddles the day 4 and 5 forecast periods
and mesoscale details remain fluid, southern CA will remain within
a Marginal risk for now. However, an upgrade to a Slight risk on
day 4 and/or day 5 remains a distinct possibility on subsequent
forecast updates.

Chenard

...Central Gulf Coast into the Lower MS Valley...

20Z Update: The only change to the previous forecast was to expand
the MRGL risk further east, mainly for areas south of I-20 through
MS/AL as ensembles continue to depict heavier rain chances
downstream despite spread within the deterministic. ML guidance is
more correlated to the heaviest rainfall in-of the Lower
Mississippi Valley which matches the previous forecast. Considering
the spread in both the D4 and D5 time frames, refrained from much
change and any upgrade opportunities. Believe the setup is
conducive for localized 3+ inch totals in spots, but not as keen on
the widespread nature of the heavier totals as indicated via the
ensemble bias corrected guidance. FFG's remain elevated in this
area of the country to begin with, so that will also thwart more
appreciable impacts with most of the flash flooding potentially
relegated to those urbanized zones where the run off potential is
more common given the impervious surfaces present. Maintained the
MRGL risk as a result.

Kleebauer

..Previous Discussion..

The system responsible for the Southern Plains heavy rainfall on
day 2 and 3 will shift into the lower and mid MS Valley on day 4
(Sat). The mid level shortwave and left exit of an impressive jet
will provide synoptic ascent for convection. Limiting factors for
flooding will be a fairly quick progression of the system,
questionable instability, and very dry antecedent conditions.
Overall, the model signal for flash flooding is not as robust as
it was yesterday and considerable model spread remains. We
continue to not prefer the quicker GFS solution, instead favoring
something closer to a consensus of the ECMWF/AIFS/AIGFS. Given the
dry antecedent conditions, any flash flood threat will likely be
high rain rate driven over urban areas or other sensitive basins.
Based on our model preferences mentioned above, the best chance of
this occurring is pretty far south, from the central Gulf Coast
into portions of the lower MS Valley. Thus the Marginal risk was
confined to just these areas with this update.

Too much model spread to introduce a risk on day 5. The GFS is an
outlier and not preferred. If there is a flash flood risk this day
it is probably centered over FL, where the EC/AIFS/AIGFS show an
axis of more concentrated convective potential.

Chenard

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
346 PM EDT Wed Oct 28 2026
Day 4 and Day 5

Valid 12Z Sat Oct 31 2026 - 12Z Mon Nov 02 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
SOUTHWEST THIS WEEKEND...

...Southwest...

20Z Update: The general synoptic pattern for the Southwest into
Southern California remains consistent in its presentation with the
latest 12z NWP suite and ML outputs. A high-end scenario for flash
flooding in the D5 time frame (12z Sun - 12z Mon) is increasingly
likely given the progged upper level evolution and anomalous
moisture advection regime slated to impact the region during the
middle to late part of the weekend, extending a bit into early
next week. Recent QPF trends label much of AZ through southern UT
and the Four Corners area as the primary impact points for this
coming event with the greatest PWAT anomalies and positive
vorticity advection moving directly into the region allowing for
widespread heavy rainfall, especially into the terrain with
prevailing upslope flow likely. Ensemble mean QPF is currently
robust at such leads with area wide 1-2" markers showing up in
Mogollon Rim, northern AZ mountains, and the Canyon areas of both
northwest AZ into southern UT. The area out by the Four Corners
towards the San Juans will see another bout of heavy rainfall with
the expansion likely into areas further south towards Navajo
Nation. These areas have already seen multiple moderate to high
impact events the past 2-3 months with one recently causing
significant flash flooding across the above areas. This setup will
likely spur another threat for such a scenario leading to a
heightened risk for upgrades in the coming forecast updates. So
long as the signal remains consistent, the threat will likely trend
towards a more impactful scenario with plenty of guidance leaning
in that direction as of the 12z global deterministic and ensemble
suite.

Kleebauer

..Previous Discussion..

An anomalous and potentially high impact setup is taking shape for
the Southwest as a longwave trough moves into the West Coast this
weekend. The depth of the trough over the eastern Pacific may drop
below the climatological 1st percentile for the time of year. Deep,
broad southwesterly flow downstream of the trough will tap into
subtropical and tropical moisture, driving PW values to near or
even above record values for the time of year. The combination of
strong dynamic forcing and wind fields, and near record caliber
moisture will support a broad swath of moderate to heavy
precipitation, maximized across orographically favored slopes.
Given lingering hydrologic sensitivity from preceding rainfall
across the region, runoff issues and some flooding appears likely
even without significant convective enhancement. Widespread cloud
cover should generally limit destabilization, but if and where
pockets of CAPE are able to develop, a more pronounced flash flood
threat could evolve. Forecast guidance exhibits some convergence,
with the 00z ECMWF and AIGFS tending towards the consistent AIFS
solution. Our preference is in this direction, with less weight
given to the GFS. This model preference paints an overall wetter
and more impactful scenario for the Southwest.

While Saturday (day 4) sits ahead of the strongest synoptic scale
forcing, the anomalous moisture axis will be established. A Slight
risk has been introduced centered across central AZ into southern
NV. Many of these areas will have seen heavy rain and convection
on Friday (day 3), leaving hydrologic conditions more primed.
Although large scale forcing and instability may dip compared to
Friday, persistent 850mb moisture transport and modest instability
should be sufficient to sustain some convection and a continued
isolated to scattered flash flood risk.

Stronger large scale forcing overspreads the region on Sunday (day
5) as the main trough axis approaches, resulting in more widespread
precipitation. While cloud cover will hinder destabilization,
cooling aloft and some cloud breaks should support some
destabilization as the trough axis approaches. The greatest
overlap of forcing, moisture and instability is forecast across
portions of AZ into southern NV and southern UT, where a day 5
Slight risk has been issued. An expansive Marginal risk surrounds
this corridor to account for the broad stratiform rain and lower
rain rates falling over a saturated region. Given the magnitude of
moisture, dynamics and terrain enhancement, the setup has the
potential to produce Moderate risk level impacts if adequate
instability materializes. Trends will be closely monitored over
the coming days.

Confidence is a bit lower over southern CA. Model guidance
indicates that an area of low pressure could enhance the
convective threat and rain rates late Saturday night into Sunday
morning. Because this straddles the day 4 and 5 forecast periods
and mesoscale details remain fluid, southern CA will remain within
a Marginal risk for now. However, an upgrade to a Slight risk on
day 4 and/or day 5 remains a distinct possibility on subsequent
forecast updates.

Chenard

...Central Gulf Coast into the Lower MS Valley...

20Z Update: The only change to the previous forecast was to expand
the MRGL risk further east, mainly for areas south of I-20 through
MS/AL as ensembles continue to depict heavier rain chances
downstream despite spread within the deterministic. ML guidance is
more correlated to the heaviest rainfall in-of the Lower
Mississippi Valley which matches the previous forecast. Considering
the spread in both the D4 and D5 time frames, refrained from much
change and any upgrade opportunities. Believe the setup is
conducive for localized 3+ inch totals in spots, but not as keen on
the widespread nature of the heavier totals as indicated via the
ensemble bias corrected guidance. FFG's remain elevated in this
area of the country to begin with, so that will also thwart more
appreciable impacts with most of the flash flooding potentially
relegated to those urbanized zones where the run off potential is
more common given the impervious surfaces present. Maintained the
MRGL risk as a result.

Kleebauer

..Previous Discussion..

The system responsible for the Southern Plains heavy rainfall on
day 2 and 3 will shift into the lower and mid MS Valley on day 4
(Sat). The mid level shortwave and left exit of an impressive jet
will provide synoptic ascent for convection. Limiting factors for
flooding will be a fairly quick progression of the system,
questionable instability, and very dry antecedent conditions.
Overall, the model signal for flash flooding is not as robust as
it was yesterday and considerable model spread remains. We
continue to not prefer the quicker GFS solution, instead favoring
something closer to a consensus of the ECMWF/AIFS/AIGFS. Given the
dry antecedent conditions, any flash flood threat will likely be
high rain rate driven over urban areas or other sensitive basins.
Based on our model preferences mentioned above, the best chance of
this occurring is pretty far south, from the central Gulf Coast
into portions of the lower MS Valley. Thus the Marginal risk was
confined to just these areas with this update.

Too much model spread to introduce a risk on day 5. The GFS is an
outlier and not preferred. If there is a flash flood risk this day
it is probably centered over FL, where the EC/AIFS/AIGFS show an
axis of more concentrated convective potential.

Chenard

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
150 PM EDT Wed Oct 28 2026

Valid 00Z Thu Oct 29 2026 - 00Z Sun Nov 01 2026


...Northern Cascades and Northern Rockies...
Days 1-2...

Closed mid-level low will spin just offshore the WA coast into
Friday, with modest downstream divergence and shedding spokes of
vorticity driving ascent into the Pacific and Interior Northwest
from the Olympics through the Northern Rockies. Although moisture
will spread eastward within pinched flow SE of this mid-level
feature, PWs will be generally near normal, and the most intense
ascent (through synoptic forcing and upslope enhancement) will be
waning early D1, so total additional snowfall is likely to be
modest. Waves of precipitation falling as snow above generally 4000
ft will continue into at least Friday, but with intensity waning
outside of pockets of convectively-enhanced precipitation driven by
mid-level instability and steepening lapse rates beneath the upper
low. Still, additional snowfall is likely to be modest, as
reflected by just small pockets of 50%+ probabilities of 4 inches
or more in the highest Olympics, northern Cascades, and Northern
Rockies in the vicinity of Glacier NP.


...Sierra into the Four Corners...
Day 3...

Although most of the winter precipitation associated with the next
system will occur beyond this current forecast period (mostly D4+),
some high-elevation snow will spread across the Sierra and into the
San Juans above 9000 ft before 00Z Sunday. This will be associated
with an impressive wave of low pressure lifting northeast from the
eastern Pacific with anomalous PW/IVT surging into the Southwest.
While snowfall D3 will likely be minimal, the extremely moist
column will support anomalously low SLR with a 10-30% chance of at
least minor impacts due to snow load developing before expanding
into D4.


The probability of significant ice across the CONUS is less than
10 percent.


Weiss

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
347 PM EDT Wed Oct 28 2026

Valid 12Z Sat Oct 31 2026 - 12Z Wed Nov 04 2026


...Storm system will bring precipitation across the West this
weekend and into the central U.S. Monday-Tuesday...


...Overview...

Over the weekend, a shortwave or two will push through a warm mean
upper ridge in the eastern half of the U.S., combining with
Pacific tropical and Gulf moisture. This will spread rain and
thunderstorms across the Mississippi Valley and East, with moderate
to heavy rain totals possible in the southern tier. Meanwhile, a
large upper trough is forecast to move through the West and bring
widespread precipitation to include heavy rain/runoff and elevation
heavy snow threats there over the weekend. Forecast models
indicate the upper trough should make its way east and likely
become a closed low when it reaches the Plains by Monday-Tuesday.
This should carry a surface low/frontal system and bring widespread
rain to the central U.S. early next week.


...Guidance/Predictability Assessment...

Model guidance is generally agreeable with the large scale pattern
described above, though with differences in the details that will
affect sensible weather. There is typical model spread with the
shortwaves moving through the central and eastern U.S. this
weekend. Recent GFS and to a lesser degree GEFS runs track the
resulting QPF faster across the Southeast and more northeastward up
the East Coast in contrast to non-NCEP guidance and even the AI-
GFS, so this was not favored by WPC after collaboration with
selected Southeast U.S. WFOs. The lastest 12 UTC GFS has trended
toward the favored concensus, bolstering forecast confidence.

Farther west, it remains questionable how exactly northern and
southern streams interact and combine within the eastern
Pacific/West trough over the weekend. However, guidance remains
overall agreeable that the trough should track east across the
Intermountain West Monday and develop a closed low later Monday
into Tuesday as it reaches the Plains. There is some model spread
in the exact position in this upper low position and deepening
surface low Monday-Tuesday, but clustering is better than normal.

The WPC forecast favored a multi-model, ensemble mean and
dynamical/AI blend through the medium range period, albeit
accordingly discounting recent runs of the GFS/GEFS.


...Weather/Hazards Highlights...

Rain and thunderstorms are likely across the Lower Mississippi
Valley to Southeast over the weekend, and locally heavy rainfall is
possible as ample moisture combines with the shortwave aloft.A WPC
Excessive Rainfall Outlook Marginal Risk threat area shows focus
over the central Gulf Coast states with system genesis and slow
passage. Rain could also spread across the Midwest to Ohio Valley
and eventually into the dammed high pressure cooled East, with
generally modest amounts.

Ample moisture will spread into California/Southwest and the
Intermountain West ahead of the upper trough over the weekend. This
system offers quite anomalous fueling moisture. Accordingly, heavy
rain is possible especially across the Southwest, while heavy snow
is possible in the higher elevations, particularly the San Juans
and central Rockies in Colorado. WPC Excessive Rainfall Outlook
Marginal and embedded Slight Risk areas are in place over the
weekend. However, the details of precipitation timing and
placement, type (including snow levels), and amounts are all
somewhat uncertain dependent on upper-level and surface flow model
differences, so continue to monitor future forecasts as the details
could change. Some rain should overspread much of the central U.S.
later on Sunday and especially Monday as the low strengthens,
including possibly heavy convective amounts. Some northern/central
High Plains snow or rain/snow mix cannot be ruled out on the
backside of the low. Additionally, gusty winds may be possible in
the Plains behind the reasonably strong surface low. Moderate to
heavy rain may persist into Tuesday with some shift east, with
continued uncertainty in the details.

Above average temperatures are expected for much of the central
and eastern U.S. under mean upper ridging (albeit with occasional
shortwaves) over the weekend into early next week. Highs in the 70s
are forecast as far north as the Ohio Valley at times, as broad
areas reach around 10-20 degrees above normal. Temperatures should
be somewhat below average in the western U.S. underneath the upper
trough, especially for highs. By Tuesday-Wednesday, the Plains
should moderate to near normal temperatures as that upper
trough/low moves eastward.


Tate/Schichtel


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast, excessive rainfall outlook,
winter weather outlook probabilities, heat indices and Key Messages
are at:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw