Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
244 AM EDT Sat Mar 15 2025

Valid 12Z Tue Mar 18 2025 - 12Z Sat Mar 22 2025


...Another Rockies to Great Lakes Snowstorm Threat next week...


...Guidance/Predictability Assessment...

Recent GFS/ECMWF/UKMET models and GEFS/ECMWF/Canadian ensemble
mean
solutions through the current latest 00 UTC guidance cycle seem
best clustered with main systems and the mid-larger scale pattern
evolution in active flow through much of next week. However,
lingering smaller scale timing differences, without resolution,
seem to favor preference for a composite guidance forecast plan.
Leaned blend weights somewhat more on the models for early-mid
next week for details before shading later next week toward
compatible ensemble means amid forecast spread growth. This plan
seems generally in line with the National Blend of Models guidance
and acts to maintain good WPC product continuity.

...Weather/Hazards Highlights...

The weather story for next week will highlight an emerging signal
for a main winter storm set to spread organized precipitation
including terrain enhanced heavy snows across the Interior West to
the Rockies Tuesday. Downstream cyclogenesis over the Plains
Tuesday will follow with a windy low track over the Midwest/Great
Lakes midweek and to eastern Canada by Thursday. This will combine
with secondary cold frontal cooling to enhance upslope in an
emerging wrap-around heavy snow threat from the north-central
Rockies/Plains to the Upper Midwest and northern Great
Lakes/Northeast Tuesday-Thursday. A wavy trailing cold front will
have less moisture than an earlier next week system, but will align
and sweep an axis of showers and thunderstorms through the central
to eastern U.S. Thursday/Friday. Most activity exits the East
Coast by next weekend. Meanwhile well upstream, steadily
progressive and moderately amplified Pacific systems will pool
moisture to spread precipitation inland from the West/Northwest
through the Rockies. Moderately heavy rains and terrain focusing
snows
are most likely via channeled moisture into the Pacific Northwest
in this pattern. Subsequent downstream rain chances may emerge next
weekend with uncertain system details and return flow developments.

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