Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
156 AM EST Thu Mar 6 2025

Valid 12Z Sun Mar 09 2025 - 12Z Thu Mar 13 2025


...Overview...

A moderately active pattern with three significant systems of
note. An upper low ejecting from the Southern Rockies/High Plains
early Saturday may produce a small area of High Plains snow and
then open up and develop a surface wave along with Southeast U.S.
enhanced rainfall. A trailing upper ridge building into the West
should weaken as it reaches the eastern states. A couple lows
developing over the East Pacific, one nearing the West Coast next
Monday (reaching the central U.S. Wednesday) and the second around
Wednesday. Both will likely bring some focused rain/mountain snow
to the West with the latter storm expected to bring the potential
for heavier totals. Meanwhile, Great Lakes/Northeast upper
troughing should flatten after Monday while a wavy mean frontal
boundary over southern Canada and the Northeast may dip into the
northern tier as the first Pacific system moves inland.

...Guidance/Predictability Assessment...

Overall guidance has had run-to-run agreement with the large scale
pattern and evolution of multiple systems, but there continues to
be some medium to smaller scale details that are up for debate.
While the the latest ECMWF has trended a bit closer to the CMC
solution for the low exiting the Southern Rockies out into the
Plains, it remains on the slower side of the envelope. The
amplifying eastern Pacific trough once again has good agreement
with a low closing off as it approaches the West Coast. The UKMET
has trended toward the notion of closing off a low however it does
so more than a half a day behind and still moving faster than the
other guidance.

The upper system should reach the Rockies/Plains by next
Wednesday, with typical spread for exact timing. A model/mean blend
yields a Plains/Midwest surface low depth close to the average of
ML models. There is still a decent amount of spread for the
potential Wednesday system near the West Coast. Some dynamical
models show a rather vigorous surface low, while CMC runs are a few
hours later to develop their strongest low.

Initial blend consisted of the 12Z ECMWF, 18Z GFS and 12Z UKMET.
By mid-period the UKMET was dropped and replaced with the 12Z GFS
along with increased weighting of the GEFS and EC ensemble means
through the end of the extended period.

...Weather/Hazards Highlights...

Guidance remains split whether training convection/heavy rain will
continue over northern Florida/southern Georgia for Sunday so opted
to maintain no risk areas for the Day 4 period. If the ECMWF/UKMET
solutions come to fruition those areas could receive 2 to 4 inches
with locally higher maximums.

Waves along a front may bring one or more episodes of mostly light
snow to the northern Great Lakes/Northeast from the weekend into
next week.

The West Coast will be ramping up for a multi-day wet period. Over
the weekend an eastern Pacific trough will direct an atmospheric
river into Vancouver Island with some precipitation extending into
northwestern Washington state. With an upper low possibly closing
off near California by early Monday (with associated surface
development), it may take until early next week for an atmospheric
river event to bring heavier rain to portions of central and
southern California, along with heavy snow for the Sierra and
eventually moving inland across the higher terrain of the
Intermountain West. Additionally, this pattern will favor gusty
winds. Another system is anticipated impact the West Coast by
midweek with heavier and more widespread precipitation and locally
strong winds; however the details remain uncertain.

Above average temperatures will expand southward/eastward from the
Northern Plains into next week. The Northern Plains should return
closer to normal by next Wednesday as a front sags south from
Canada. Locations from the northern-central Plains through the
Midwest and eventually into the northern Mid-Atlantic should see
one or more days with highs reaching 15-30F above early March
averages. This warmth may push highs well into the 60s from the
Dakotas into Iowa and into the 70s as far north as the Middle
Mississippi Valley and parts of the Mid-Atlantic.

Campbell/Rausch

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