534
FXUS02 KWNH 190622
PREEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
221 AM EDT Sat Oct 19 2024

Valid 12Z Tue Oct 22 2024 - 12Z Sat Oct 26 2024

...General Overview...

The weather pattern across the continental U.S. on Tuesday will be
featured with an upper ridge and surface high over the Eastern
U.S., accompanied by above average temperatures. An incoming trough
from the Midwest will then dislodge this ridge and the associated
cold front will herald the arrival of cooler weather towards the
end of the week, but it will have limited moisture to work with so
rainfall amounts from the Great Lakes to the Northeast will be
generally light. Meanwhile, the next Pacific storm system is
expected to approach the Pacific Northwest by late Thursday and
into Friday, bringing a return to rain and high mountain snow from
northern California to Washington state. An upper ridge and milder
temperatures are likely ahead of this Pacific storm system.

...Guidance/Predictability Assessment...

The latest model guidance features reasonably good agreement
across the continental U.S. to begin the forecast period Tuesday,
and a blend of the GFS/ECMWF/CMC along with some previous WPC
continuity served as a good starting point in the forecast process.
There is still quite a bit of uncertainty across the Western U.S.
in regards to the placement of the upper ridge axis ahead of the
approaching Pacific low, which also has considerable model
uncertainty. There is more confidence in the forecast across the
South and the Eastern U.S. with the large scale surface high that
is progged to be in place. The ensemble means accounted for about
60% of the forecast blend by next Saturday.

...Weather/Hazards Highlights...

The cold front crossing the Great Lakes and into the Northeast for
the middle of the week will likely have just enough moisture and
lift to produce some mainly light to moderate showers for the
middle of the week, mainly north of the Interstate 70 corridor. It
should continue to remain dry and mostly sunny for areas farther to
the south across the Mid-Atlantic and the Southeast U.S., where
the very pleasant fall weather will continue for a while. There are
no risk areas in the Day 4 and Day 5 excessive rainfall outlooks.

Out West, showers are expected to return to the Pacific Northwest
coast by Thursday and become heavier going into Friday as the cold
front from the Pacific low moves ashore. This currently does not
look like an atmospheric river event, but some areas could get 1 to
locally 2 inches of rainfall by Saturday morning. Lighter
precipitation is possible for the Northern Rockies by this time.
Snow
is likely for the highest terrain of the Cascades.

In terms of temperatures, it will feel more like September across
much of the east-central U.S. for the middle of the week, with
highs running 10-20 degrees above average for late October. The
cold front will bring a return to more typical conditions for this
time of year, but still quite pleasant. A warming trend then
commences for the western High Plains and the Rockies by the end of
the week and into next weekend as the upper ridge rebuilds ahead of
the Pacific storm system.


Hamrick


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 (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

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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