626
FXUS02 KWBC 120736
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
336 AM EDT Mon Oct 12 2026

Valid 12Z Thu Oct 15 2026 - 12Z Mon Oct 19 2026

...Heavy rainfall threat for the south-central U.S. into Thursday...

...Record heat for the Mid-South and Southeast through Thursday...


...Overview...

An upper low lingering over the Intermountain West will allow for
moisture from ex- Simon to stream northward, continuing to bring an
expansive area of rain and thunderstorms across the central U.S.
into Thursday. The energy from this trough will split after
Thursday, with part of it moving into the Southwest U.S. and the
rest combining with strong northern stream energy from Canada. This
results in a deep trough into the eastern half of the U.S. late
week, shifting offshore next weekend. Before then, strong upper
ridging over the south- central to southeastern U.S. early in the
period should allow for much above normal to record- setting warm
temperatures broadly into Thursday before modifying.


...Guidance/Predictability Assessment...

Model guidance continues to show good agreement on the evolution
of the upper low over the West on Thursday, with most solutions now
showing a splitting of energy. Some uncertainty remains with how
much energy gets left back in the Southwest, but most of the energy
should get scooped up by a shortwave into the north-central U.S.
with now only minor timing differences on the progression of an
amplified trough through the Great Lakes and Northeast Friday and
Saturday. After this, additional energy slides through south-
central Canada ahead of a deeper trough into the West early next
week. There is some uncertainty with the timing of this trough.

With sufficient model agreement, was able to use a blend of the
deterministic/AIFS guidance through Day 5. After that, increased
the ensemble means to 60 percent of the total blend by Day 7 to
help smooth out some of the smaller scale late period details.
Overall, this approach is consistent with WPC continuity and the
National Blend of Models.


...Weather/Hazards Highlights...

Associated with the upper low over the West, a Plains lee low
pressure system plus moisture from what is leftover from Simon
streaming northward will continue to bring rain in the south-
central U.S. into Thursday. Thunderstorms and heavy rain/flooding
potential are likely in the Southern/Central Plains ahead of a cold
front, with a WPC Slight Risk area in place for the Thursday
Excessive Rainfall Outlook. Farther north, areas of rain are
forecast to stretch from the north-central U.S. into the Northeast
Thursday and Friday. The pattern will be favorable for lake
effect/enhanced rain and possibly snow across the Great Lakes to
Interior Northeast through Friday- Saturday. Gusty winds are
possible especially behind the surface low track through the north-
central U.S. and Great Lakes. Showers and storms could accompany
the front as it pushes through Florida late week as well.

Ahead of the front, temperatures in the Lower Mississippi Valley,
Mid-South, and the Southeast will be well above normal and likely
continue to set new daily high temperature records (upper 80s to
the mid 90s) into Thursday. The trough moving into the East on
Friday will moderate temperatures back towards normal. Meanwhile,
the upper trough in the West will bring broadly below average
temperatures there for midweek. Canadian high pressure is forecast
to gradually track across the country behind the cold front late
week into the weekend, cooling temperatures and providing
potentially fairly broad frost/freeze threats. Meanwhile, the West
Coast could see above normal temperatures, including some highs
near 90 for parts of coastal California again by late week.


Santorelli/Tate


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







$$