Valid Wednesday April 09, 2025 to Tuesday April 15, 2025
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM
EDT April 01 2025
Synopsis: Mid-level low pressure is favored
over eastern portions of Canada and the U.S, with surface high pressure
overspreading much of the central and eastern CONUS early in week-2. While this
is expected to bring a period of welcomed dryness for areas affected by heavy
precipitation in week-1, the synoptic setup favors elevated chances for much
below normal temperatures which may adversely impact emerging springtime
vegetation following a very warm March for much of the southeastern CONUS.
Upstream, mean mid-level high pressure forecast is expected to keep much of the
western CONUS free of weather related hazards, with any enhanced onshore flow
limited to the higher elevations of western North America.
Hazards - Moderate risk of much below normal temperatures
for portions of the Southern Plains, Lower and Middle Mississippi, Tennessee,
and Ohio Valleys, Appalachians, Mid-Atlantic, and Southeast, Wed, Apr 9.
- Slight risk of much below normal temperatures for much of the south-central
and eastern CONUS, Wed-Thu, Apr 9-10.
- Slight risk of high winds for the northeastern CONUS, Wed, Apr 9.
Detailed SummaryFor Friday April 04 - Tuesday April
08:
WPC Days 3-7 U.S. Hazards For Wednesday April 09 - Tuesday
April 15: There continues to be good consistency in the dynamical models
advertising a large-scale pattern change, with amplified mean ridging
(troughing) becoming established over western (eastern) North America by early
next week. Tied to this latter mid-level feature, both the GEFS and ECWMF
ensembles show the mean surface high pressure center shifting over the
Tennessee Valley and the Appalachians behind a departing low pressure system
over the Canadian Maritimes. Although the troughing is favored to deamplify by
the middle of next week, a slight risk of high winds remains posted for
portions of the Great Lakes, Ohio Valley, Mid-Atlantic and Northeast for Apr 9
based on lingering signals in the Probabilistic Extreme Tools (PETs). Any
residual moisture being wrapped in the deepening low may lead to accumulating
snowfall over parts of the Northeast and Appalachians, though models are
unsupportive of any amounts exceeding heavy snow thresholds.
Accompanying the mean surface high pressure, the GEFS and ECMWF ensembles
continue to show elevated chances (>50%) for negative temperature anomalies in
the double digits, with the strongest cold signals now focused over the
southeastern CONUS. This is well reflected in the GEFS and ECMWF PETs,
depicting >30% chances for minimum temperatures falling below the 10th
percentile and below 40 degrees F on day 8 (Apr 9). One key difference between
the raw and calibrated tools is the ECMWF maintains more of a westerly
extension of the cold signal into Texas than the GEFS before temperatures begin
to moderate. As a result, a moderate risk of much below temperatures remains
issued for Apr 9, with much of its coverage mainly confined to areas east of
the Mississippi, and a broader slight risk area of much below normal
temperatures (Apr 9-10) with more coverage in the Southern Plains and Lower
Mississippi Valley out of deference to the ECMWF. While the anomalous cold is
well out of reach of wintertime hazard criteria, such cold temperatures could
be quite a shock following a very warm March in the lee of the Rockies, and
potentially bring adverse impacts to emerging springtime vegetation across many
parts of the southcentral and southeastern CONUS
Later in week-2, ensembles continue to feature a reloading mean trough by
days 10 and 11, implying a renewed hazardous cold risk for the eastern CONUS.
In addition, there is increased support in guidance favoring surface low
formation along the lower Eastern Seaboard at this lead. However, both raw and
calibrated tools are not yet supportive of including any additional temperature
and/or precipitation related hazards, but this potential will continue to be
monitored in upcoming outlooks. While less supported in the ECMWF and Canadian
ensembles, additional lee cyclogenesis is also possible later in week-2, which
could bring elevated winds to parts of the Southern High Plains where there
remains dry fuels that could enhance the risk of wildfire activity.
With the development of strong mid-level ridging favored over the western
CONUS, unseasonably warmer and drier conditions are forecast compared to
week-1, resulting in no weather related hazards for the western CONUS for
week-2. Any enhanced onshore flow to promote above-normal and possibly heavy
precipitation would most likely be limited to the higher latitudes of North
America extending from the upper Pacific Northwest to the southern Alaska
Mainland. This is reflected in the PETs which depict increased chances for
3-day precipitation amounts exceeding the 85th percentile. However, forecast
actual totals do not presently meet hazard criteria, as heavy precipitation
potential remains tenuous due to the favored weakening of mid-level troughing
over the northeastern Pacific during week-2.
Forecaster: Nick
Novella
$$
Please consult local NWS Forecast Offices for short range forecasts and region-specific information.
Resources
Week-2 Probabilistic Extremes Tool
GFS Ensemble Forecasts