713
FXUS02 KWBC 230656
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
156 AM EST Sun Feb 23 2025

Valid 12Z Wed Feb 26 2025 - 12Z Sun Mar 02 2025


...Overview...

The upper flow pattern should remain rather progressive through
much of the medium range period. At the start of the period on
Wednesday, a shortwave through the north-central U.S. should
eventually deepen over the East Thursday into Friday, with
secondary reinforcing energy by Saturday. This should help an
amplifying ridge out West late this week, with a southern stream
cutoff low moving inland across Southern California and the
Southwest this weekend. Another deep and elongated upper trough
looks to move into the West Coast next Sunday.


...Guidance/Predictability Assessment...

There continues to be reasonable agreement on the large scale
pattern during the medium range period, but still plenty of
uncertainty in the details, some of which could have notable
sensible weather impacts. The shortwave into the East shows some
timing uncertainty still, with the CMC quite a bit slower than the
GFS and ECMWF late week into the weekend. There is also some
question on whether southern stream energy hangs back across the
southern Plains as well. The reinforcing shortwave into the East
next weekend also shows timing and amplitude differences. The upper
low into southern California has become better clustered compared
to a day or two ago, but still with plenty of run to run and model
to model variability in timing as it moves into the Southwest. Also
timing uncertainty with the next trough into the West next
weekend.

The WPC progs for tonight utilized a general model blend, slightly
favoring the GFS and ECMWF for the first half of the period.
Leaned more heavily on the ensemble means later in the period,
amidst more uncertainty, but still maintaining half deterministic
guidance by Day 7 for additional system definition.


...Weather/Hazards Highlights...

A cold front shifting across the Ohio Valley into the East will
spread generally light to moderate precipitation across this region
Wednesday into Thursday. Some precipitation could be snow in the
northern part of the precipitation shield across northern New
England. A clipper system should bring an additional round of
precipitation to the Great Lakes and Northeast Friday into
Saturday.

A building ridge should keep conditions quiet and dry across the
West Wednesday to Friday. The exception might be parts of the
Pacific Northwest which could see some light precipitation. The
upper trough towards the coast next weekend though should bring
increased precipitation back into the forecast for much of the
Northwest into northern California. To the south, the model
variability with the southern stream upper low approaching
California and moving inland late next week/weekend leads to
uncertainty in the precipitation forecast for California to the
Southwest and the south-central U.S. for the late period, but there
is general agreement in at least some light precipitation.

By the start of the period on Wednesday, much of the lower 48 will
be much above normal in terms of temperatures, with decent
coverage of plus 10-20 degree anomalies. The northern/central
Plains can expect the highest anomalies of 20 to locally 25 degrees
above normal, with 60s for highs as far north as Nebraska or
perhaps even South Dakota at times. The Southwest and Great Basin
can also expect warmer than average conditions underneath the
building upper ridge. Parts of the Desert Southwest could reach
into the 90s especially Tuesday- Thursday, and some sites could set
daily record high max/min temperatures in the vicinity. Areas east
of the Mississippi should also see warm conditions into Wednesday,
but should cool back to near normal (or slightly below in spots)
by late week underneath upper troughing.


Santorelli


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





$$