Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 PM EDT Mon Apr 7 2025

Valid 12Z Thu Apr 10 2025 - 12Z Mon Apr 14 2025


...General Overview...

The 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, to 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 cold front crossing the Intermountain West
to the central/northern Plains through next Monday.


...Guidance/Predictability Assessment...

The latest models and ensembles remain in good agreement at least
through the first half of the period, showing a departing Eastern
trough only to be replaced with an amplifying shortwave established
over the East by Saturday. Models suggest a brief closed low over
the East this weekend and then some increased uncertainty in timing
and placement of the main energy as it exits the Northeast early
next week. The next trough enters the Northwest by Saturday, and
the past several runs of the CMC has been notably slower with this.
By Monday, the CMC has a closed low still over the interior West,
while the GFS and ECMWF (with support from the ensemble means) is
well east into the Upper Midwest by that point.

The WPC blend for today utilized a deterministic model blend for
Days 3 and 4, bringing in the ensemble means in place of the CMC by
Day 5. Gradually increased contributions of the ensemble means for
late period, but still maintained a 50/50 deterministic (GFS and
ECMWF)/ensemble mean blend. This maintained good agreement with the
previous shift as well.


...Weather/Hazards Highlights...

The low pressure system crossing the Ohio Valley and then reaching
the East Coast to close out the week will be the next event to
monitor, with widespread showers expected from the Deep South to
the Great Lakes on Thursday. Even though forecast rainfall totals
are not expected to be heavy, the ground will likely still be quite
saturated for many of those areas affected by the prolific recent
rainfall, so that is something that will continue to be monitored,
but for now no risk areas appear warranted for the Day 4/Thursday
excessive rainfall outlook. Colder high pressure held over the
Northeast interior in advance of the system may allow for some
terrain focusing snow chances. A deepening coastal low near the
Mid- Atlantic Coast on Friday and into early Saturday should bring
higher rain chances and breezy conditions from Virginia to New
England into next weekend. A Marginal Risk area continues for Day
5/Friday from NJ/PA northward to southern New England with more of
an enhanced QPF signal in the deterministic guidance, with perhaps
1-2 inches of rainfall.

Elsewhere across the country, periods of moderate rain and
mountain snow return to western Washington and Oregon courtesy of
onshore flow and a shortwave passage Thursday, but this does not
look like a major event at this time. Light snow then reaches the
higher elevations of the northern Rockies by next weekend as the
moisture moves inland. Dry conditions are forecast from the
Southwestern U.S. to the central/southern Plains during the entire
forecast period.

In terms of temperatures, a moderating trend commences by the end
of the week across the Eastern U.S. as the upper trough lifts out
of New England. Looking ahead to next weekend, lows should be near
average while daytime highs remain slightly below average with
increased cloud cover. 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 on Friday. These milder
conditions then reach the central and northern Plains by next
weekend as the ridge shifts eastward.

Santorelli/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