Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
157 AM EST Mon Mar 3 2025

Valid 12Z Thu Mar 6 2025 - 12Z Mon Mar 10 2025


...General Overview...

The strong low pressure system crossing the Central U.S. early this
week is expected to be over southern Quebec by Thursday morning,
with the cold front exiting the East Coast, followed by cooler
conditions to close out the work week. Out West, a broad upper
trough over the Intermountain West will likely evolve into two
separate shortwaves, with one more progressive and merging with the
northern stream flow, and the other lingering longer over the
southern Rockies, progressing eastward as a positively tilted
trough that will likely support a surface low near the Gulf Coast
through Sunday. Meanwhile, a Pacific cold front will likely
approach the West Coast Sunday night into Monday with rain and
mountain snow returning to the region.

...Guidance/Predictability Assessment...

The 00Z model guidance suite has come into better agreement
regarding the expected overall evolution of the Western U.S. upper
trough compared to the past few model cycles. It appears likely
that two separate surface lows will develop, with the first one
over the central Plains on Friday, and a second one near the Gulf
Coast on Saturday. The UKMET is a little slower with the first low
across the Ohio Valley on Saturday and farther to the north with
the Gulf Coast low over the weekend. The CMC holds the upper trough
back to the west more so than the better clustered GFS/ECMWF and
their respective means going into Sunday, so the blend favored more
of those solutions instead of the CMC by that time. The ensemble
means were gradually increased to about 40-60% by Sunday-Monday.


...Weather/Hazards Highlights...

An amplified upper level trough reaches the Northeast U.S. by
Thursday afternoon, along with a strong surface low that will
track across Quebec, with secondary surface cyclogenesis near Nova
Scotia Thursday night. Most of the significant rainfall should
already be off the coast by this time, with some lingering showers
over Maine and snow across the higher terrain of New England and
Upstate New York. 

The large upper trough over the Western U.S. late in the week, in
combination with embedded shortwave energy, will result in numerous
snow showers across the Intermountain West and central/northern
Rockies, with heavy snow likely for the southern Sierra, the
Wasatch Range, and the higher terrain of Wyoming and western
Colorado. Mainly moderate heavy rain is expected for southern
California and the Peninsular and Transverse mountain ranges, and
given recent burn scar sensitivities for portions of this region, a
Marginal Risk remains valid for the new Day 4 period Thursday. The
overall QPF signal is not as impressive going into Friday (Day 5)
across the Rockies and the central Plains, and therefore no risk
areas are necessary for the Day 5 period. Looking ahead to next
weekend, showers and some thunderstorms are expected to develop
near the Gulf Coast as the surface low evolves, and the next round
of rain and mountain snow reaches the West Coast by Sunday.

Cooler than average readings are likely from the Intermountain
West to the western High Plains in conjunction with the upper
trough situated across the southern Rockies for the end of the
week.
Looking ahead to next Sunday/Monday, there will likely be a warm-
up across the north-central U.S., with daytime highs potentially
10-20+ degrees above early March averages, with highs potentially
reaching well into the 60s from the Dakotas into portions of the
Upper Midwest.

Hamrick


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