Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
257 AM EDT Mon Mar 17 2025

Valid 12Z Thu Mar 20 2025 - 12Z Mon Mar 24 2025


...Winter Storm to impact Upper Midwest/Great Lakes to northern
Northeast as an unsettled/wet pattern works over the Northwest...


...Overview...

Guidance overall agrees that a few different low pressure systems
will move generally west to east across the lower 48 this week.
A potent low pressure system will strengthen significantly to the
lee of the Rockies and track towards the Upper Midwest midweek,
then move across the Great Lakes and Northeast later week. A
wrapback swath of heavy snow and gusty winds are expected on the
northern side of the storm track from the Central Plains to the
Upper Midwest, with expected blizzard conditions in some areas.
Some wintry weather is also expected in the Northeast, with the
highest chances in northern/interior New England given coastal low
development. Two other main low pressure systems are forecast to
then move west to east across the nation, but will be quite a bit
weaker than the first lead system. This pattern favors multi- day
unsettled and wet weather for the West/Northwest this week, with an
enhanced moisture/rain focus into the Pacific Northwest and
terrain enhanced heavy snow potential inland across the Northwest
to the Rockies. Expect less defined rainy periods for the Central
to Eastern U.S. may become better organized later period contingent
on emerging return inflow with expected upper flow amplification.

...Guidance/Predictability Assessment...

Models and ensembles again show good agreement on the overall
weather pattern through the medium range period, with reasonably
good agreement on individual storm systems as well. Forecast
confidence is above average overall with a guidance composite,
albeit with more uncertainty in details late in the period that
seem well mitigated consistent with predictability by the blending
process. The WPC forecast blend 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...

A big weather story surrounds a late season winter storm expected
to produce blizzard conditions for parts of the north-central U.S.
into midweek. A deepened low pressure system will track from the
Central Plains to the Upper Midwest and reach the Great Lakes by
Thursday. The storm will have a wrap-around heavy snow threat on
the northern side of the low track, and the tight pressure
gradient around the system will likely produce strong gusty winds
that could create blizzard conditions. This windy system will push
east across the Northeast Thursday into Friday, and some wintry
weather can be expected in northern/interior New England. Some
wintry weather may also be possible in the Central Appalachians.
Showers and thunderstorms with a trailing/wavy cold front of this
system will work across and sweep offshore the East Coast Thursday.

Upstream, a series of Pacific low pressure/frontal systems will
move into the West/Northwest and trigger repeating rounds of
precipitation through next weekend. Moderately heavy rain and
mountain snow are likely in the Pacific Northwest where moderate
moisture will be channeled onshore. The WPC Day 5/Friday Excessive
Rainfall Outlook initiated a near coastal Marginal threat area
given compounding effects of multiple days of precipitation may
lead to local runoff issues. There will also be periodic heavy snow
threats inland as enhanced by terrain across the Northwest to the
north-central Rockies. These Pacific systems are forecast to move
east across the Central and Eastern U.S. Friday through the weekend
and may produce mainly modest precipitation chances this week, but
activity may intensify into next week given potential system
organization with expected upper flow amplification.

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