Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
242 AM EDT Sun Oct 18 2026

Valid 12Z Sun Oct 18 2026 - 12Z Tue Oct 20 2026

...Nor'easter develops along the Carolina coast this weekend, bringing
potential coastal flooding and beach erosion along portions of the
Mid-Atlantic coast into early next week...

...Flash flooding risk for portions of South Florida for Sunday...


A non-tropical coastal low (Nor'easter) off the North Carolina coast is
expected to track further offshore, limiting inland showers. However,
persistent onshore flow will continue to bring coastal impacts along
portions of the Mid-Atlantic coast. Persistent and strong onshore winds
can result in coastal flooding and beach erosion into Tuesday. Across
southern Florida, a lingering frontal boundary will renew showers and
thunderstorms through Monday. Slow-moving storms may produce heavy
downpours, leading to localized flash flooding across portions of South
Florida on Sunday.

Across the Southwest, moisture will continue to stream northward from
northwestern Mexico and will support scattered showers and thunderstorms
across portions of the Southwest through Monday. Rainfall coverage and
amounts will depend on the northward extent of the moisture plume and the
persistence of convective development. Further north, a approaching low
pressure system over the eastern Pacific will bring increasing
precipitation chances along the coast. Otherwise, daytime highs begin to
moderate to seasonal temperatures through Monday.


Oudit


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
346 AM EDT Sun Oct 18 2026

Valid 12Z Tue Oct 20 2026 - 12Z Sat Oct 24 2026


...Potent Nor'easter to bring maritime and East Coastal impacts...

...Southern California/Southwest/Rockies Heavy Precipitation...


...Overview...

A developing Nor'easter is expected to bring wind and coastal
flooding impacts to the East Coast mid-to-late week. A cutoff low
will bring excessive rainfall concerns from Southern California to
the Four Corners states mid-to-late week as well.


...Guidance/Predictability Assessment...

There's good agreement on the amplification of a mid-level cut-off
low in the East Pacific mid-week, followed by the weakening of it
as it enters the Western U.S. by late week. The exact speed of the
disturbance remains in question but has improved over the last few
runs. The amplitude and location of a downstream upper ridge over
the Central U.S. is captured very well by most of the available
guidance. Models continue to trend farther away from the East
Coast with the location of the Nor'easter mid-week.

The ECAIFS and Euro mean were favored in the blend between days 4
and 7 due to notable run-to-run inconsistencies in the
deterministic Euro and GFS.


...Weather/Hazards Highlights...

A slow moving Nor'easter offers a protracted threat for strong
winds, potentially heavy rain and coastal flooding/stormy maritime
conditions from the coastal Mid-Atlantic to along/off the
Northeast. The mid-latitude cyclone responsible for these hazards
is forecast to intensify off the Carolinas late this weekend
before drifting back toward the mainland early in the week.
Persistent onshore flow should generate strong winds with gusts
exceeding 40 kts possible along the immediate coastline. Beach
erosion is also likely from the aforementioned strong onshore flow.
This developing storm also offers potential subtropical transition
to monitor next week as per NHC. Overall, please refer to WPC's
Key Messages on our website for more information:
www.wpc.ncep.noaa.gov.

A shortwave passing south of the Gulf of Alaska is forecast to
dig/amplify into a cut-off low over the Eastern Pacific just off
the West Coast midweek. The depth and speed of this system will
determine how much moisture it can pull into the region. The latest
trends suggest an increasing likelihood for anomalous moisture to
be pulled into the West. This moisture will then interact with a
frontal system and produce scattered to isolated thunderstorms over
portions of the Four Corners. Heavy rainfall may occur as well
with some Extreme Forecast Index shift of tail signals showing up
across Southern California through the Southwest. Some high
elevation snowfall is also likely for the Sierra through parts of
the Intermountain West to the Rockies with slow progression. System
emergence through the Rockies into the Plains will favor the
spread of the rainfall shield and emerging Plains convection late
period.

Another shortwave diving south through British Columbia will send a
cold front into the Northwest mid-to-late week. This system could
generate high elevation snow for portions of the Northern
Rockies/Intermountain West late week.

Temperatures will be around average for the East Coast, above
average over the Plains and Mississippi Valley/Midwest, and
generally below average in the West beneath persistent upper
troughing.


Kebede/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
414 AM EDT Sun Oct 18 2026

Valid 00Z Mon 19 Oct 2026 - 00Z Mon 26 Oct 2026

The guidance agrees on brisk trade winds in association with a
high pressure system that becomes increasingly warm core, building
to the north of the Islands through Monday. Disturbances in the
Easterlies bring slightly enhanced moisture (precipitable water
values of 1.25-1.5") during this time frame which should lead to
a rainfall uptick in the Mauka shower regime. Meanwhile, directly
over Hawai'i, a strongly positively tilted upper trough remains
across the state, with the guidance generally agreeing on a mid-
level low forming midweek just north of the main islands.

Late next week into next weekend, the guidance is moving a new
cold low to the north of Hawai'i which lifts the mid- level low
previously north of Hawai'i northeast (a compromise of the 00z
ECMWF/GFS splits the difference seen in the guidance with this
second mid- to upper-level feature). It dramatically weakens the
trades and starts to shift/buckle the ITCZ/monsoon trough to the
southeast of the state. There remains a heavy rainfall signal late
next week into next weekend east of Hawai'i near this wave in the
ITCZ/monsoon trough, though it has weakened a bit from the
guidance seen this time yesterday.

Roth

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 AM EDT Sun Oct 18 2026
Day 1
Valid 12Z Sun Oct 18 2026 - 12Z Mon Oct 19 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR A PORTION OF
SOUTH FLORIDA...

South Florida...
A secondary cold front will make its way southward across south
Florida today resulting in redevelopment of thunderstorms. Some of
the storms will be capable of producing localized downpours over
urbanized areas. After the rainfall in the period prior to the
start of the Day 1 period...the area may be more prone to flash
ponding and excessive rain, Hence the Marginal Risk is maintained.

Bann


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 AM EDT Sun Oct 18 2026
Day 2
Valid 12Z Mon Oct 19 2026 - 12Z Tue Oct 20 2026

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Most of the guidance from the 18/00Z cycle continues to keep the
system far enough away from the east coast to keep the excessive
rainfall threat off-shore. Even so...it should be acknowledged
that the probability of excessive rainfall is probably not zero
percent but not to the level of re-introducing a Marginal risk
area.

Bann


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 AM EDT Sun Oct 18 2026
Day 3
Valid 12Z Tue Oct 20 2026 - 12Z Wed Oct 21 2026

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

...Southwest...
The atmosphere still doesn't appear to be sufficiently saturated
with 0.75 inches to 1 inch nor terribly unstable with only a few
hundred J/kg of CAPE forecast by the 00Z GFS. As a result...did not
outlook a Marginal Risk in this part of the country.

Bann

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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 AM EDT Sun Oct 18 2026
Day 4 and Day 5

Valid 12Z Wed Oct 21 2026 - 12Z Fri Oct 23 2026

...Southwest...
On Wednesday/Wednesday night, a deep layer cyclone approaches
SoCal and scoops up moisture from a dying Trudy and flings it into
the Southwest. Near the cold low itself, MU CAPE of 250-500 J/kg
and precipitable water values of 1-1.3" with up to 30 kts of
onshore flow at 850 hPa is forecast. There's enough of a heavy rain
signal for a Marginal Risk for the Transverse and Peninsular
Ranges, which is there to help cover burn scar concerns. In and
near the Four Corners, MU CAPE is forecast to rise to 500-750
J/kg, precipitable water values of 0.75-1.25" are anticipated. The
ingredients available along with deterministic guidance QPF output remain
wet enough for a Marginal Risk, though the higher totals seen
24 hours ago have come down a bit, possibly due to a ~6 hour slow
down/westward shift of the overall system when compared to this
time yesterday. Hourly rain amounts to 2" would be possible across
portions of AZ, NM, and the Four Corners in isolated to widely
scattered spots.

For Thursday/Thursday night, the system shifts eastward across
Southwest and Great Basin/Intermountain West into portions of the
Southern High Plains, with similar moisture and instability in
tow. The guidance advertises local totals in the 2-3" range, and
hourly rain amounts to 2" remain possible. The mountains of SoCal
appear to have enough moisture/instability left and guidance QPF
signal to introduce a Marginal Risk there with the Marginal Risk
across the interior West shifting eastward. It is possible that
the risk levels could increase as we move closer to this weather
setup -- particularly if instability trends reverse/increase
-- but the slowing trend in the guidance with this system
introduces enough uncertainty not to do go with a risk level
beyond Marginal either day at the present time.

Roth

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 AM EDT Sun Oct 18 2026
Day 4 and Day 5

Valid 12Z Wed Oct 21 2026 - 12Z Fri Oct 23 2026

...Southwest...
On Wednesday/Wednesday night, a deep layer cyclone approaches
SoCal and scoops up moisture from a dying Trudy and flings it into
the Southwest. Near the cold low itself, MU CAPE of 250-500 J/kg
and precipitable water values of 1-1.3" with up to 30 kts of
onshore flow at 850 hPa is forecast. There's enough of a heavy rain
signal for a Marginal Risk for the Transverse and Peninsular
Ranges, which is there to help cover burn scar concerns. In and
near the Four Corners, MU CAPE is forecast to rise to 500-750
J/kg, precipitable water values of 0.75-1.25" are anticipated. The
ingredients available along with deterministic guidance QPF output remain
wet enough for a Marginal Risk, though the higher totals seen
24 hours ago have come down a bit, possibly due to a ~6 hour slow
down/westward shift of the overall system when compared to this
time yesterday. Hourly rain amounts to 2" would be possible across
portions of AZ, NM, and the Four Corners in isolated to widely
scattered spots.

For Thursday/Thursday night, the system shifts eastward across
Southwest and Great Basin/Intermountain West into portions of the
Southern High Plains, with similar moisture and instability in
tow. The guidance advertises local totals in the 2-3" range, and
hourly rain amounts to 2" remain possible. The mountains of SoCal
appear to have enough moisture/instability left and guidance QPF
signal to introduce a Marginal Risk there with the Marginal Risk
across the interior West shifting eastward. It is possible that
the risk levels could increase as we move closer to this weather
setup -- particularly if instability trends reverse/increase
-- but the slowing trend in the guidance with this system
introduces enough uncertainty not to do go with a risk level
beyond Marginal either day at the present time.

Roth

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
446 AM EDT Sun Oct 18 2026

Valid 12Z Sun Oct 18 2026 - 12Z Wed Oct 21 2026

The probability of significant snow and ice across the CONUS is
less than ten percent through Tuesday.


Mullinax

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
346 AM EDT Sun Oct 18 2026

Valid 12Z Tue Oct 20 2026 - 12Z Sat Oct 24 2026


...Potent Nor'easter to bring maritime and East Coastal impacts...

...Southern California/Southwest/Rockies Heavy Precipitation...


...Overview...

A developing Nor'easter is expected to bring wind and coastal
flooding impacts to the East Coast mid-to-late week. A cutoff low
will bring excessive rainfall concerns from Southern California to
the Four Corners states mid-to-late week as well.


...Guidance/Predictability Assessment...

There's good agreement on the amplification of a mid-level cut-off
low in the East Pacific mid-week, followed by the weakening of it
as it enters the Western U.S. by late week. The exact speed of the
disturbance remains in question but has improved over the last few
runs. The amplitude and location of a downstream upper ridge over
the Central U.S. is captured very well by most of the available
guidance. Models continue to trend farther away from the East
Coast with the location of the Nor'easter mid-week.

The ECAIFS and Euro mean were favored in the blend between days 4
and 7 due to notable run-to-run inconsistencies in the
deterministic Euro and GFS.


...Weather/Hazards Highlights...

A slow moving Nor'easter offers a protracted threat for strong
winds, potentially heavy rain and coastal flooding/stormy maritime
conditions from the coastal Mid-Atlantic to along/off the
Northeast. The mid-latitude cyclone responsible for these hazards
is forecast to intensify off the Carolinas late this weekend
before drifting back toward the mainland early in the week.
Persistent onshore flow should generate strong winds with gusts
exceeding 40 kts possible along the immediate coastline. Beach
erosion is also likely from the aforementioned strong onshore flow.
This developing storm also offers potential subtropical transition
to monitor next week as per NHC. Overall, please refer to WPC's
Key Messages on our website for more information:
www.wpc.ncep.noaa.gov.

A shortwave passing south of the Gulf of Alaska is forecast to
dig/amplify into a cut-off low over the Eastern Pacific just off
the West Coast midweek. The depth and speed of this system will
determine how much moisture it can pull into the region. The latest
trends suggest an increasing likelihood for anomalous moisture to
be pulled into the West. This moisture will then interact with a
frontal system and produce scattered to isolated thunderstorms over
portions of the Four Corners. Heavy rainfall may occur as well
with some Extreme Forecast Index shift of tail signals showing up
across Southern California through the Southwest. Some high
elevation snowfall is also likely for the Sierra through parts of
the Intermountain West to the Rockies with slow progression. System
emergence through the Rockies into the Plains will favor the
spread of the rainfall shield and emerging Plains convection late
period.

Another shortwave diving south through British Columbia will send a
cold front into the Northwest mid-to-late week. This system could
generate high elevation snow for portions of the Northern
Rockies/Intermountain West late week.

Temperatures will be around average for the East Coast, above
average over the Plains and Mississippi Valley/Midwest, and
generally below average in the West beneath persistent upper
troughing.


Kebede/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