Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
301 PM EDT Thu Mar 20 2025

Valid 12Z Sun Mar 23 2025 - 12Z Thu Mar 27 2025


...Overview and Guidance/Predictability Assessment...

Progressive upper flow into the weekend in two streams will
amplify into next week with the development of a warming/building
West Coast ridge and a cooling/deepening and unsettling east-
central U.S. trough.

Operational and ML models capture the evolution of the overall
synoptic pattern across the lower 48 for next week. All models are
in reasonably good agreement on the day 3 pattern, save for
several
00z GEFS members which depict a slower Central U.S. trough. This
trend continues through the rest of the period. Deterministic
guidance are more progressive than the ensembles and operational
AIFS with the upper low propagating through the Great Lakes region
on day 4. The upper pattern simplifies into mean troughing in the
East and mean ridging in the West beginning on day 5. A Euro-
centric general model blend is used from day 5 through 7.


...Weather/Hazards Highlights...

Shortwave troughs riding a Western ridge will shift from the
northeast Pacific into BC Sunday with a potent moisture plume to
the south that pushes across western WA. A Marginal Risk for
excessive rainfall is maintained only into Day 4/Sunday for
coastal Washington as compounding effects of multiple preceding
bouts of precipitation may lead to local runoff issues. Amplified
upper trough development and deep system genesis early-mid next
week should prove slow to approach the West Coast, but should
spread organized precipitation back into the Northwest in about a
week.

The amplifying low over the northern Plains into the Great Lakes
Sunday will draw broad scale Gulf moisture up the MS Valley and
support a heavy rain and a severe weather threat for parts of Mid-
South and lower MS Valley into the TN Valley. The Day 4/Sunday ERO
Marginal Risk area is maintained for the Lower Mississippi and
Tennessee Valleys. Enhanced rains then spread as a wavy cold front
sweeps across the Southeast/Eastern Seaboard Monday into Tuesday. A
WPC Day 5/Monday ERO Marginal Risk area was maintained to cover
lingering and training cell potential over the eastern Gulf Coast.

Meanwhile on the northern periphery of the expanding precipitation
shield, reinforcing cold air wrapping around the main deep low
appears to support a heavy snow threat for the Great Lakes region
Sunday into Monday, spreading over the northern and interior
Northeast into Monday and Tuesday with closed upper low/trough
approach and with coastal New England triple-point low development.

An amplifying ridge in the West will support an early return of
spring-like temperatures in the West next week. Highs are expected
to be between 15-30 degrees above average for much of the region.
There's increasing potential for widespread high/low records to be
tied/broken next Tuesday/Wednesday. This includes much of the
Desert Southwest, where some places may experience daytime highs
over 100 degrees.

Kebede/Schichtel


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