Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
253 AM EDT Fri Apr 25 2025

Valid 12Z Mon Apr 28 2025 - 12Z Fri May 02 2025


...Potent Rockies to Central U.S. Spring Storm expected early next
week...

...Overview...

The primary focus early next week will be on ejecting Rockies
upper trough energy and associated northern Plains through Upper
Great Lakes surface system, bringing some heavy rain potential to
the northern tier and possible severe weather to central/east-
central U.S. The northern part of this system will continue onward
but the trailing part of the front should stall and develop some
waviness ahead of weaker southwestern shortwave energy, providing a
focus for enhanced central U.S. rainfall around midweek. Upstream
energy should push the evolving system and rainfall eastward
thereafter, with an upper trough axis reaching the east-central
states by Friday. A trailing upper ridge should move into the West
after early Wednesday, likely followed by a trough/cold front
nearing the West Coast by Friday.

...Guidance/Predictability Assessment...

A 12Z/18Z operational model composite provided a reasonable
depiction of significant features during the first half of the
period. There is decent clustering with only typical detail
variations for northern Plains low pressure that should track
across the Upper Great Lakes and then eastern Canada, with the
trailing front ultimately stalling over the Plains as weak
shortwave energy lingers over the southwestern U.S. By the latter
half of the week there is still better than average agreement among
model/ensemble guidance that incoming shortwave energy should
eject the southwestern shortwave, leading to a surface wave
reaching the vicinity of the eastern Great Lakes by early Friday.
However shortwave detail uncertainties increase at that time and
machine learning (ML) models show more spread for the eastern U.S.
surface pattern, so confidence is a bit lower than what might be
suggested by the dynamical model/ensemble clustering.

Meanwhile there are also developing differences with the upper
trough nearing the West Coast by next Friday. The most prominent
difference is that GFS runs are faster and less amplified than the
dynamical/ML model consensus for a majority of the trough. The GEFS
mean is closer to the majority scenario. While a leading mean
ridge moves over the West late in the week, there may be weak
trough/upper low energy that reaches the Southeast/Great Basin but
with very low confidence for specifics. Late week preferences sided
mostly with the 12Z ECMWF and the 18Z GEFS/00Z ECens means given
comparisons along the West Coast, while this solution represented
consensus over the East.

...Weather/Hazards Highlights...

The early week Rockies into central U.S. storm will bring high
elevation snow to the north-central Rockies along with a heavy
rainfall threat farther east along the northern tier in association
with anomalous moisture and favorable dynamics/surface focus. The
Day 4/Monday Excessive Rainfall Outlook depicts a Marginal Risk
area that includes portions of the northern High Plains into Upper
Midwest. Some locally heavy rain may fall farther south over the
Mississippi Valley and vicinity but without a sufficiently clear
signal to merit a risk area for now. By Tuesday into early
Wednesday the Plains part of the system's trailing front should
stall and provide a focus for trailing/repeat convection. The Day
5/Tuesday ERO reflects the runoff threats with a Marginal Risk area
from central Texas into the Lower Ohio Valley. Meanwhile the Storm
Prediction Center continues to monitor for severe weather threats
over central/east-central U.S. Monday-Tuesday.

The central U.S. heavy rain potential will likely continue through
the rest of Wednesday before upper dynamics and surface
waviness/fronts progress into the East with somewhat lesser rain
totals. Farther west, shortwave energy pushing through the West
should spread rain and some high elevation snow from the Northwest
through the northern and central Rockies over the course of the
week.

Very warm temperatures over the Plains/Mississippi Valley on
Monday will progress into the East ahead of an advancing cold
front, with highs up to 10-20F above normal and morning lows even a
little more anomalous. The wavy front may not reach parts of the
Southeast/Mid-Atlantic, where temperatures could remain somewhat
above normal through Friday. Cool readings from the Southwest to
northern High Plains on Monday should moderate as the air mass
continues eastward. Then expect a trend to above normal
temperatures over the West mid-late week as an upper ridge builds
in. Highs may reach 10-15F above normal from the Pacific Northwest
into northern Rockies.

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