020
FXUS02 KWBC 261920
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
320 PM EDT Mon Oct 26 2026

Valid 12Z Thu Oct 29 2026 - 12Z Mon Nov 02 2026


...Heavy rainfall likely for portions of Texas especially on
Thursday...


...Overview...

At the start of the medium range period Thursday, an upper low will
be in place atop the Northwest, while shortwaves farther south
serve to deepen the trough across the West. Tropical moisture will
stream ahead of the trough and bring potentially heavy rainfall to
Texas on Thursday and Friday, shifting across the Lower Mississippi
Valley and Southeast over the weekend as shortwaves move through a
warm mean upper ridge. Meanwhile, moisture is forecast to funnel
into the West and bring broadening precipitation chances there over
the weekend.


...Guidance/Predictability Assessment...

Model agreement remains very good with the overall pattern through
at least Saturday, including the upper low over the Northwest,
deepening troughing overall in the West, and downstream mean
ridging. A multi-model blend of the dynamical and AI individual
guidance worked well to depict the pattern.

More notable model differences start to arise over the weekend
with the evolution of the western trough. Though spread has
generally decreased over the past few model cycles, models still
vary with the distribution of energy within the initially positively
tilted trough, affecting its movement and timing eastward. The
trend including the new 00Z guidance has generally been for an
elongated trough/upper low rather than splitting energy, so the
trough (especially the southern end) looks to steadily shift east
over the weekend into early next week. There did not seem to be any
true outliers in the guidance at this point. At the surface, an
unusually far south (~25N latitude) non-tropical low will move east
through the Pacific into southern California/northern Mexico and
bring an atmospheric river with it. There is a fair amount of
spread in the timing, with the AIFS reaching the coast late
Saturday, the AIGFS Sunday, and the GFS/ECMWF later Sunday. Farther
east, there are some shortwave differences moving through the
central/eastern U.S., but nothing too egregious. Because of the
increasing model spread, used the ensemble means in the forecast
blend to half Day 6 and more Day 7 to mitigate the individual model
differences. If there has been any notable trend with the latest
12Z guidance, it was to slow and flatten the far southern shortwave
in the eastern Pacific expected to impact the Southwest this
weekend. This would lead to precipitation beginning on Sunday and
QPF leaning towards the lighter end of the ensemble distribution
across southern CA and the Sierra, but still moderate to heavy
across the Intermountain West and southern/central Rockies.
Downstream, surface cyclogenesis is likely across the central U.S.
on Monday ahead of the approaching deep upper trough. However, the
timing and orientation of this trough leads to uncertainty
regarding the depth of this low and latitudinal placement.



...Weather/Hazards Highlights...

Rain and thunderstorms are forecast for the southern Plains later
this week, including potentially heavy rainfall particularly in
south-central and west-central Texas as moisture from current
Tropical Storm Vance streams in. A Slight Risk (level 2/4) of
Excessive Rainfall has been issued for parts of the TX Hill Country
into the eastern Big Bend on Thursday. This rainy and stormy
pattern will move east across the southeastern U.S. into the
weekend. Farther north, rounds of rain are also forecast across the
north- central U.S., with generally modest amounts. Florida could
also see diurnally driven scattered showers and thunderstorms.

Precipitation is expected across the Pacific Northwest Thursday
underneath the upper low. Increasing coverage is likely in the
Intermountain West by Friday, including localized heavy rain
possible in the Southwest. Then over the weekend, Pacific moisture
will increase across the West and bring broadening precipitation
chances to California and across the Intermountain West. The
details of where/when precipitation occurs and could be heavy are
dependent on the uncertain upper-level flow, so expect changing
forecast details. Mountain snow is also expected across the high
elevations of the West, although specifics in regards to amounts
and snow levels remain uncertain as well.

Well above average temperatures are expected for portions of the
central and eastern U.S. from day to day under mean upper ridging.
Highs in the 70s are forecast as far north as the Upper Great Lakes
region, with 80s reaching the Mid-Mississippi Valley on Thursday,
broadly around 15-20 degrees above normal. Temperatures should
remain above normal from the Plains eastward through early next
week. Temperatures should be somewhat below average in the western
U.S. underneath the upper trough, especially for highs.


Tate/Snell


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





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