Weather Prediction Center

National Oceanic and Atmospheric Administration

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

Valid 00Z Mon Oct 19 2026 - 00Z Wed Oct 21 2026

...Norâ€easter moving north just off the Mid-Atlantic Coast will produce
rain showers along parts of the Mid-Atlantic and Northeast Coast through
Tuesday...

...Low pressure moving southward along the West Coast will develop
scattered rain over parts of California through Tuesday...

Low pressure off the North Carolina coast will slowly retrograde westward
towards the Mid-Atlantic Coast before moving eastward out over the
Atlantic by Tuesday evening. Moisture circulating around the low will
produce rain over parts of the Northeast and Mid-Atlantic Coast through
Tuesday.

The non-tropical area of low pressure will develop and intensify well off
the North Carolina coast early this week before slowly tracking north and
exiting the region by Thursday. As it strengthens, the storm will likely
bring long-duration coastal impacts to portions of the Mid-Atlantic,
especially for the North Carolina Outer Banks.

Persistent, strong onshore winds will bring moderate coastal flooding,
dangerous marine conditions, and beach erosion, especially during high
tides, into mid-week from southern New Jersey through the North Carolina
coast. Moreover, the storm is likely to bring wind gusts in excess of 45
mph across the Outer Banks region and the Virginia Tidewater. Furthermore,
details on the magnitude and location of impacts are still evolving as
conditions deteriorate. Check weather.gov regularly for the latest
updates.

Elsewhere, a second area of low pressure over the Eastern Pacific will
move southward along the West Coast, bringing scattered rain to parts of
the Northern California coast late Monday morning. Overnight Monday into
Tuesday, the rain will move southward to Central/Southern California with
scattered showers and thunderstorms over parts of the Central/Northern
Great Basin and Southwest. Lastly, a weak stationary front and easterly
flow off the Atlantic will produce scattered rain and embedded
thunderstorms over the eastern coast of Florida through Tuesday evening.


Ziegenfelder


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
328 PM EDT Sun Oct 18 2026

Valid 12Z Wed Oct 21 2026 - 12Z Sun Oct 25 2026


...Lingering Nor'easter offers East Coast Maritime Impacts...

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


...Overview...

A lingering Nor'easter will bring wind and coastal flooding
impacts to the East Coast into mid-late week. A cutoff low will
support heavy rainfall from Southern California to the Four
Corners states mid-to-late week along with some mountain snows.
Associated activity will spread through the West Rockies and then
work downstream with PLains system genesis. There is also an
emerging onshore wet pattern for Florida to monitor late period.


...Guidance/Predictability Assessment...

Guidance forecast clustering seems reasonably good for mid-later
this week and a broad blend with focus on the models seems to
provide a solid base forecast and messaging, bolstering forecast
confidence. Model differences increase more significantly heading
into next weekend, especially for stream separation with handling
of ample Pacific energies set to work into a western U.S. mean
upper trough. The 12 UTC models remain mixed. Instead, favor a
solution trending more in line with better compatible GEFS/ECMWF
ensemble means for max cycle-cycle consistency and NBM continuity.


...Weather/Hazards Highlights...

A Nor'easter will offer threats for high winds and coastal
flooding with stormy maritime conditions from the coastal Mid-
Atlantic to off the Northeast. The storm will intensify off the
Carolinas over the next few days and bring strong winds back
to the coastline into mid-late week to protract a threat for beach
erosion. The storm offers potential subtropical transition to
monitor later week per NHC. 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 into midweek and work inland into California and
the Southwest later week. Lead anomalous moisture will feed into
the West to support increasingly widespread rain/thunderstorms
over the region and through the Great Basin/Rockies. WPC Excessive
Rainfall Outlook Marginal Risk areas are in place for local runoff
concerns, but rainfall should also aide lingering fire concerns.
Some high elevation snowfall is likely for the Sierra through parts
of the Intermountain West to the Rockies. The slow moving system
will then eject downstream and lead cyclo/fronto genesis and return
flow should support emerging showers/thunderstorms over the Plains
by next weekend, albeit still with timing uncertainty to navigate.

Upstream, a closed low with ample upper troughing will dig from
the Gulf of Alaska to approach the Northwest and/or offshore late
week. This system could generate moderate precipitation including
high elevation snows into the Northwest as dependent on ultimate
inland penetration to monitor with upcoming guidance.

Meanwhile, mean upper trough development and lingering down though
the Southeast U.S. may lead into a wet onshore flow period for
especially southern Florida late period into next week.

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
504 PM EDT Sun Oct 18 2026
Day 1
Valid 211Z Mon Oct 19 2026 - 12Z Mon Oct 19 2026

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

Chenard


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

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

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHWEST...

Introduced a Marginal Risk for portions of the southwest (SE AZ/SW
NM). Remnant energy from a lingering upper-trough just to the west
will spread eastward over the region later tonight and into the
day Monday helping to trigger scattered storms. An influx of
modestly anomalous moisture from the Pacific will lead to
sufficient instability (1000 J/KG CAPE) by Monday afternoon to
support locally heavy downpours. The now available hi-res
guidance, particularly the HRRR, is rather bullish on the potential
for rain rates of 1-2" per hour, more than enough to lead to
isolated flash flooding. Both the HREF and RRFS ensembles also have
moderate to high probabilities of rainfall exceeding 1" and low-
end probabilities for 2".

Putnam


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
504 PM 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...

Modestly anomalous moisture will remain in place Tuesday ahead of
the more potent upper-trough beginning to dig southward along the
West Coast. However, overall instability remains low and with the
bulk of upper-energy still remaining to the west of the region, the
risk for heavy rainfall and flash flooding should remain very low.

Putnam

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

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

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

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHWEST WEDNESDAY INTO THURSDAY...

20z Update: Introduced a broad Slight risk across portions of the
Southwest on both days 4 and 5. This is a favorable setup for heavy
rainfall and at least scattered flash flooding with anomalous
moisture and a deep mid/upper level low pushing across the region.
Deep southerly flow ahead of the approaching trough will advect
tropical moisture northward, with a PW plume of near record values
for mid/late October. As is typical with these events, instability
will be the key factor in determining the magnitude and extent of
flash flooding...as these broad moisture plumes can often bring
abundant cloud cover limiting destabilization. However, both the
ECMWF and AIFS depict CAPE over 1000 J/kg on both Wednesday and
Thursday across portions of AZ/NM and over 500 J/kg even into
portions of NV/UT/CO. There is an initial moisture/instability
surge on Wednesday over AZ well ahead of the upper low, and then
the steepening lapse rates with the upper low on Thursday should
also produce some destabilization.

So while confidence on the exact details remain low given we are 4
to 5 days out, there is growing confidence in a heavy rain and
flash flood threat over the Southwest region Wednesday into
Thursday. The ingredients in place also suggest that at least
locally significant impacts are a possibility. Trends will continue
to be monitored and can not rule out the need for embedded MDT
risk area(s) if/where enough instability materializes.

Chenard

...Previous Discussion...

...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
504 PM EDT Sun Oct 18 2026
Day 4 and Day 5

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

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHWEST WEDNESDAY INTO THURSDAY...

20z Update: Introduced a broad Slight risk across portions of the
Southwest on both days 4 and 5. This is a favorable setup for heavy
rainfall and at least scattered flash flooding with anomalous
moisture and a deep mid/upper level low pushing across the region.
Deep southerly flow ahead of the approaching trough will advect
tropical moisture northward, with a PW plume of near record values
for mid/late October. As is typical with these events, instability
will be the key factor in determining the magnitude and extent of
flash flooding...as these broad moisture plumes can often bring
abundant cloud cover limiting destabilization. However, both the
ECMWF and AIFS depict CAPE over 1000 J/kg on both Wednesday and
Thursday across portions of AZ/NM and over 500 J/kg even into
portions of NV/UT/CO. There is an initial moisture/instability
surge on Wednesday over AZ well ahead of the upper low, and then
the steepening lapse rates with the upper low on Thursday should
also produce some destabilization.

So while confidence on the exact details remain low given we are 4
to 5 days out, there is growing confidence in a heavy rain and
flash flood threat over the Southwest region Wednesday into
Thursday. The ingredients in place also suggest that at least
locally significant impacts are a possibility. Trends will continue
to be monitored and can not rule out the need for embedded MDT
risk area(s) if/where enough instability materializes.

Chenard

...Previous Discussion...

...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
141 PM EDT Sun Oct 18 2026

Valid 00Z Mon Oct 19 2026 - 00Z Thu Oct 22 2026

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


Snell

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
328 PM EDT Sun Oct 18 2026

Valid 12Z Wed Oct 21 2026 - 12Z Sun Oct 25 2026


...Lingering Nor'easter offers East Coast Maritime Impacts...

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


...Overview...

A lingering Nor'easter will bring wind and coastal flooding
impacts to the East Coast into mid-late week. A cutoff low will
support heavy rainfall from Southern California to the Four
Corners states mid-to-late week along with some mountain snows.
Associated activity will spread through the West Rockies and then
work downstream with PLains system genesis. There is also an
emerging onshore wet pattern for Florida to monitor late period.


...Guidance/Predictability Assessment...

Guidance forecast clustering seems reasonably good for mid-later
this week and a broad blend with focus on the models seems to
provide a solid base forecast and messaging, bolstering forecast
confidence. Model differences increase more significantly heading
into next weekend, especially for stream separation with handling
of ample Pacific energies set to work into a western U.S. mean
upper trough. The 12 UTC models remain mixed. Instead, favor a
solution trending more in line with better compatible GEFS/ECMWF
ensemble means for max cycle-cycle consistency and NBM continuity.


...Weather/Hazards Highlights...

A Nor'easter will offer threats for high winds and coastal
flooding with stormy maritime conditions from the coastal Mid-
Atlantic to off the Northeast. The storm will intensify off the
Carolinas over the next few days and bring strong winds back
to the coastline into mid-late week to protract a threat for beach
erosion. The storm offers potential subtropical transition to
monitor later week per NHC. 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 into midweek and work inland into California and
the Southwest later week. Lead anomalous moisture will feed into
the West to support increasingly widespread rain/thunderstorms
over the region and through the Great Basin/Rockies. WPC Excessive
Rainfall Outlook Marginal Risk areas are in place for local runoff
concerns, but rainfall should also aide lingering fire concerns.
Some high elevation snowfall is likely for the Sierra through parts
of the Intermountain West to the Rockies. The slow moving system
will then eject downstream and lead cyclo/fronto genesis and return
flow should support emerging showers/thunderstorms over the Plains
by next weekend, albeit still with timing uncertainty to navigate.

Upstream, a closed low with ample upper troughing will dig from
the Gulf of Alaska to approach the Northwest and/or offshore late
week. This system could generate moderate precipitation including
high elevation snows into the Northwest as dependent on ultimate
inland penetration to monitor with upcoming guidance.

Meanwhile, mean upper trough development and lingering down though
the Southeast U.S. may lead into a wet onshore flow period for
especially southern Florida late period into next week.

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