798
FXUS02 KWBC 280735
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
335 AM EDT Wed Oct 28 2026

Valid 12Z Sat Oct 31 2026 - 12Z Wed Nov 04 2026


...Storm system will bring precipitation across the West this
weekend and into the central U.S. Monday-Tuesday...


...Overview...

Over the weekend, a shortwave or two will push through a warm mean
upper ridge in the eastern half of the U.S., combining with
Pacific and Gulf moisture. This will spread rain and thunderstorms
across the Mississippi Valley and East, with moderate to heavy rain
totals possible in the southern tier. Meanwhile, a large upper
trough is forecast to move through the West and bring widespread
precipitation there over the weekend. Forecast models indicate the
upper trough should make its way east and likely become a closed
low when it reaches the Plains by Monday-Tuesday. This should carry
a surface low/frontal system and bring widespread rain to the
central U.S. early next week.


...Guidance/Predictability Assessment...

Model guidance is generally agreeable with the large scale pattern
described above, though with differences in the details that will
affect sensible weather. There is typical model spread with the
shortwaves moving through the central and eastern U.S. this
weekend. GFS runs track the resulting QPF faster across the
Southeast faster than the non-NCEP guidance and even the AI-GFS, so
this was not favored.

Farther west, it remains questionable how exactly northern and
southern streams interact and combine within the eastern
Pacific/West trough over the weekend. The AIFS runs have been
persistent in showing more of a digging northern stream, which
brings the southern stream shortwave (carrying an interestingly far
south non-tropical surface low) farther east into southern
California/northern Mexico more quickly than most other guidance.
However, the recent 00Z AIGFS and ECMWF are starting to show this
pattern too. Regardless, models are agreeable that the trough
should track east across the Intermountain West Monday and develop
a closed low later Monday into Tuesday as it reaches the Plains.
There is some model spread in the exact position in this upper low
position and thus the deepening surface low Monday-Tuesday, but 00Z
models are not too dissimilar. The 00Z GFS does seem to be on the
strong side of the envelope showing the surface low in the 990s on
Tuesday. The upper/surface lows generally look to stall or move
slowly east into midweek.

The WPC forecast favored a multi-model dynamical/AI blend at the
start of the medium range period, incorporating increasing
proportions of the ensemble means to half by Day 7 to mitigate
individual model differences.


...Weather/Hazards Highlights...

Rain and thunderstorms are likely across the Lower Mississippi
Valley to Southeast over the weekend, and locally heavy rainfall is
possible as ample moisture combines with the shortwave aloft. Rain
could also spread across the Midwest to Ohio Valley and eventually
into the East, with generally modest amounts.

Ample moisture will spread into California and the Intermountain
West ahead of the upper trough over the weekend. Heavy rain is
possible especially across the Southwest, while heavy snow is
possible in the higher elevations, particularly the San Juans and
central Rockies in Colorado. However, the details of precipitation
timing and placement, type (including snow levels), and amounts are
all somewhat uncertain dependent on upper-level and surface flow
model differences, so continue to monitor future forecasts as the
details could change. Some rain should overspread much of the
central U.S. later on Sunday and especially Monday as the low
strengthens, including possibly heavy amounts. Some
northern/central High Plains snow or rain/snow mix cannot be ruled
out on the backside of the low. Additionally, gusty winds may be
possible in the Plains behind the reasonably strong surface low.
Moderate to heavy rain may persist into Tuesday with some shift
east, with continued uncertainty in the details.

Above average temperatures are expected for much of the central
and eastern U.S. under mean upper ridging (albeit with occasional
shortwaves) over the weekend into early next week. Highs in the 70s
are forecast as far north as the Ohio Valley at times, as broad
areas reach around 10-20 degrees above normal. Temperatures should
be somewhat below average in the western U.S. underneath the upper
trough, especially for highs. By Tuesday-Wednesday, the Plains
should moderate to near normal temperatures as that upper
trough/low moves eastward.


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



$$