Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
256 PM EDT Wed Apr 9 2025

Valid 12Z Sat Apr 12 2025 - 12Z Wed Apr 16 2025


...General Overview...

An amplified upper level trough will be in place across the East
Coast for the upcoming weekend, with a surface low off the Mid-
Atlantic coast likely tracking a little south of Nova Scotia by
early next week. Meanwhile, an upper ridge crossing the central
U.S. during the weekend will support very warm conditions for this
time of year. An incoming upper trough across the northern Rockies
will then spur surface cyclogenesis across the central/northern
Plains by Sunday with a cold front crossing the Intermountain West.
The cold front should then reach the south-central and eastern
U.S. by Tuesday as the leading upper ridge continues eastward. The
front's supporting upper trough should reach the East by next
Wednesday. Another trough is likely to reach the West Coast region
during the Tuesday to Wednesday time period, but its evolution has
higher uncertainty.

...Guidance/Predictability Assessment...

By Sunday the latest models still develop some spread for the
finer details of the upper trough/possible embedded upper low
crossing the northern Rockies, though the envelope has been
gradually narrowing toward an intermediate solution. The
GFS/ICON/CMC still lean toward a slightly farther south upper low
crossing Montana into the Dakotas while other dynamical and machine
learning (ML) guidance either tracks the upper low near the
northern Montana border or waits to close off an upper low farther
to the east. By Monday the ML models offer reasonable support for
the upper low and occluded surface system to reach near or just
west of Lake Superior. Latest GFS runs stray to the slower side of
the spread as this system continues into Canada. However there is
good large scale agreement for the overall upper trough reaching
the East by next Wednesday.

Over the eastern Pacific into the West, there is continued spread
for a leading upper low (composed of energy from the southern
periphery of the weekend shortwave) that may reach the Southwest
around Tuesday. The GFS/CMC lean on the slower side of the spectrum
for this feature. Then guidance continues to signal that flow
within the next upper shortwave should split, but with some
differences in the exact proportion that digs southward versus
continuing into the West. GEFS/ECens means and along with the
latest ECMWF/GFS runs have support from one ML model cluster, with
a shortwave reaching western Canada and the Northwest U.S. while
the remaining energy reaches offshore California. A couple 00Z ML
models had more ridging over the Northwest though.

For the system affecting the East this coming weekend, guidance
continues to show various detail differences. In particular the GFS
has been leaning to the northwest/north side of the spread for the
surface system and moisture extent while CMC runs show a more open
trough versus the closed low in most other solutions.

Based on guidance comparisons and continuity, an early-mid period
forecast consisting of 40 percent 00Z ECMWF and 20 percent each 06Z
GFS, 00Z UKMET, and 00Z CMC provided a good starting point to
reflect majority themes or an intermediate scenario as appropriate.
20-40 percent inclusion of the 06Z GEFS/00Z ECens means helped to
downplay less confident details by next Tuesday-Wednesday.

...Weather/Hazards Highlights...

The low pressure system emerging off the southern New England
coast this weekend will likely keep widespread light to moderate
rainfall across the Northeast U.S., especially on Saturday with the
heaviest rainfall beginning to exit the Cape Cod region. Higher
elevation snow is likely for the northern Appalachians through the
weekend with several inches of accumulation possible. With most of
the heaviest rainfall expected on Friday and guidance showing a lot
of spread for where any locally enhanced rain could fall on
Saturday/Day 4, that day's Excessive Rainfall Outlook depicts no
risk areas. The Sunday/Day 5 ERO also has no risk areas, though
there will likely be a swath of moderate rainfall across the
northern tier states with the surface low moving through. Flow
behind this system will support a broad area of strong and gusty
winds across the eastern Rockies into parts of the Plains on
Sunday.

Elsewhere across the Continental U.S., expect several inches of
snowfall across the higher terrain of the Northern Rockies through
the weekend as the upper trough/possible embedded low moves across
the region. As the northern Plains system tracks into Canada, the
front moving across the central Plains and Midwest into the East
Monday-Tuesday will not have much moisture or instability to work
with, so rainfall associated with it should be mainly light. There
may be an increase in shower coverage across portions of the
southern Plains by the middle of next week as a potential wave of
low pressure develops along the front, but this activity does not
look impressive at this time. Portions of the East may see brisk
winds next Tuesday-Wednesday.

The mid-upper level ridge crossing the central U.S. this weekend
will support widespread above normal temperatures from the Desert
Southwest to the central and northern Plains. Some highs may reach
20-25 or so degrees above normal, corresponding to temperatures
into the 90s from western Texas to eastern Colorado and western
Kansas, before the cold front brings readings closer to climatology
for Monday. Some daily records will be possible, especially on
Saturday. The warmth will encompass the Midwest to the Deep South
to start the week and then reach the East Coast by Tuesday, with
highs about 5-15 degrees above average. Before then, widespread
cloud cover over the weekend will maintain cooler than average
highs across the Eastern U.S. before moderating. The next upper
trough reaching the East by Wednesday may bring another cool day
then, with the central Appalachians/eastern Great Lakes possibly
seeing highs at least 10 degrees below normal. To the west, another
upper ridge should spread above normal readings from the West
Coast into the northern and central Plains during early-mid week
with decent coverage of plus 10-15 degree anomalies for highs.

Rausch/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