Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
255 AM EDT Tue Mar 18 2025

Valid 12Z Fri Mar 21 2025 - 12Z Tue Mar 25 2025


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

Progressive upper flow with multiple embedded systems this week in
two main streams will amplify into next week with the development
of a warming West Coast ridge and a cooling and unsettling east-
central U.S. trough.

Models and ensembles again show good agreement on the weather
pattern through the medium range period, with reasonably good
agreement on individual storm systems as well. Forecast confidence
remains above average overall with a guidance blend, albeit with
more uncertainty in details late in the period. However, these
seem mitigated consistent with predictability by the blending
process. The WPC forecast mainly comprised of near even parts of
the GFS/ECMWF/CMC/UKMET and GEFS/ECMWF/Canadian ensembles seems in
line with the National Blend of Models and WPC product continuity.

...Weather/Hazards Highlights...

Lead New England coastal storm genesis into Friday offers a windy
heavy snow threat for northern/interior Northeast before departure
as a maritimes hazard into the weekend.

Well upstream, a series of Pacific systems and moisture feeds will
fuel periods of unsettled wet weather to the West/Northwest, with
an enhanced moisture/rain focus for the Pacific Northwest and
terrain enhanced heavy snows inland to the Rockies. The WPC Day
4/Friday Excessive Rainfall Outlook maintains a Marginal Risk area
for coastal northwest Oregon and Washington, with renewed focus to
monitor later weekend into early next week. Compounding effects of
multiple days of precipitation may lead to local runoff issues.

Well downstream, less defined rainy periods over the central to
eastern U.S. this week are expected to become much better
organized Sunday into early next week with cyclogenesis and
emerging return inflow. A deepening system track will also offer a
Midwest/Great Lakes/Northeast wrapping snow threat on the colder
northern portion of an expanding area of precipitation.

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