Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
232 PM EDT Sun Apr 6 2025

Valid 12Z Wed Apr 09 2025 - 12Z Sun Apr 13 2025

...General Overview...

It remains well evident in guidance that a large upper trough that
will be in place across the Northeast U.S. early in the week is
forecast to lift out of the region by Thursday. An amplifying
shortwave trough originating from south- central Canada is expected
to amplify as it drops southeast across the Ohio Valley, and thus
support a surface low from the Midwest to the Mid-Atlantic coast to
close out the work week and emerging off the coast next Saturday.
Meanwhile, an upper level ridge builds across the Intermountain
West and Rockies Thursday into Friday, and then shifts eastward to
the Plains by next weekend. With the ridge departing the West, an
upper trough approaches from the Pacific Northwest and supports a
slow moving frontal boundary across the Intermountain West.

...Guidance/Predictability Assessment...

The WPC medium range guidance suite was primarily derived from a
composite blend of seemingly reasonable and best clustered
guidance from the 00 UTC ECMWF/UKMET/Canadian models and WPC
continuity valid for Wednesday into Friday morning. Forecast
spread increases heading into next weekend and a composite of
the overall compatible GEFS/ECMWF/Canadian means and WPC continuity
offers a good forecast basis while tending to mitigate much of
numerous smaller scale system details as consistent with individual
system predictability. Latest 12 UTC guidance seems in line,
including some reasonably favorable trends from the GFS.

...Weather/Hazards Highlights...

The weather pattern continues to look uneventful in terms of heavy
rainfall prospects for the middle of the week, with no risk areas
currently needed for the excessive rainfall outlooks for both days
4 and 5. Having said that, a swath of mainly light to moderate
rainfall is expected from the Midwest to the Ohio Valley, and
perhaps a second area of rainfall developing across the Tennessee
River Valley on Thursday as the surface low and front moves
through. Even though forecast rainfall totals are not expected to
be heavy, the ground will likely still be quite saturated for many
of those areas after the prolific rainfall lately, so that is
something that will continue to be monitored. Colder high pressure
held over the Northeast interior in advance of the system may
allow for some terrain focusing snow chances. A surface low to
deepening coastal low may begin to develop near the Mid- Atlantic
Coast by Friday night and result in higher rain chances and breezy
conditions from Virginia to New England into next weekend. Given
flow amplitude and trends, the system offers potential for
enhanced rain up the coast and to be a maritime hazard to monitor.

Elsewhere across the country, periods of moderate rain and
mountain snow return to western Washington and Oregon courtesy of
onshore flow and a couple of shortwave trough passages mid to late
week, but these don't look like major events at this time. Light
snow then reaches the higher elevations of the northern Rockies by
next weekend as the moisture moves inland.

In terms of temperatures, the coldest day of the forecast period
is expected on Wednesday with high temperatures running about
10-20 degrees below average. A moderating trend commences by the
end of the week as the upper trough lifts out of the Northeast
states. Looking ahead to next weekend, lows should be near average
while daytime highs remain slightly below average. Meanwhile, a
warm pattern is expected for the Western U.S. through the end of
the week with both daytime highs and overnight lows about 10-20
degrees above average, with the greatest anomalies over the Great
Basin. These milder conditions then reach the central and northern
Plains by next weekend as the ridge shifts eastward.

Hamrick/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