Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
422 AM EDT Wed Oct 28 2026
Day 1
Valid 12Z 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...
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
422 AM 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, but there is still some uncertainty in the rainfall
distribution within this area. For now, there is high-end Slight
Risk potential for this area, but a targeted Moderate Risk might
not be out of the question for portions of the Stockton and Edwards
Plateaus in future updates. However, that decision may not be able
to be made until model guidance becomes a bit more clear and when
the entire period is within range of the hi-res models.
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
Day 2 threat area:
www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
422 AM 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. Another question will be the
speed of the system. There is quite a bit of uncertainty among the
models on how fast this system will progress, resulting in
location and magnitude differences in the QPF. A smaller Slight
Risk area may eventually be needed across portions of Texas and
Oklahoma if conditions align and rain falls over areas that are
forecast to receive heavy rainfall on Thursday.
Dolan
Day 3 threat area:
www.wpc.ncep.noaa.gov/qpf/99epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
422 AM 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...
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.
...Central Gulf Coast into the Lower MS Valley...
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
422 AM 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...
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.
...Central Gulf Coast into the Lower MS Valley...
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
