Prognostic Meteorological Discussion
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FXUS21 KWNC 271757
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT March 27 2024

SYNOPSIS: An area of departing surface low pressure across the northeastern
contiguous U.S. (CONUS) may bring periods of high winds and heavy snow to
portions of the Northeast at the start of the week-2 period. Meanwhile, a
digging trough and associated lee-side cyclogenesis will bring chances for
heavy snow to parts of the northern and central Plains and Rocky Mountains.
More broadly, periods of high winds may occur in conjunction with the robust
trough and a series of surface lows across the West.

HAZARDS

Slight risk of heavy snow across the interior Northeast, Thu-Fri, Apr 4-5.

Slight risk of high winds for the northeastern CONUS, Thu-Fri, Apr 4-5.

Slight risk of heavy snow for portions of the northern and central Plains and
Rocky Mountains, Thu-Sun, Apr 4-7.

Slight risk of episodic high winds for the Great Plains and Interior West,
Thu-Wed, Apr 4-10.



DETAILED SUMMARY

FOR SATURDAY MARCH 30 - WEDNESDAY APRIL 03:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR THURSDAY APRIL 04 - WEDNESDAY APRIL 10: Mid-level troughing and associated
surface low-pressure will be progressing northeast over the Northeast at end of
week-1 and into early week-2. Models are in fair agreement with this system
bringing chances for high winds to much of the northeastern CONUS. The GEFS and
ECENS have many members forecasting the mean sea level pressure (MSLP) to fall
towards 990mb. Along the northern side of this system and across the higher
elevations of the interior Northeast, a period of heavy snow may occur as well
as the low-pressure pulls in colder air from Canada. Therefore, a slight risk
of heavy snow and high winds is posted for Apr 4-5 for portions of the interior
Northeast and the broader northeastern CONUS respectively.



A slight risk of episodic high winds is designated for the Great Plains,
Interior West and portions of the Four Corners, Apr 4-10, associated with a
digging mid-level trough and a series of surface lows potentially forming over
the Interior West. The ECENS Probabilistic Extremes Tool (PET) shows at least a
20% chance of wind speeds exceeding the 85th percentile and 20 mph (25 mph,
locally) across the highlighted risk area. The GEFS PET indicates these
thresholds for Nevada and the Southwest. The National Interagency Fire Center
(NIFC) indicates low to moderate fire potential across parts of the eastern
Four Corners region and Central and Southern Plains by the end of week-1.
Little to no precipitation anticipated during week-1 combined with increased
high wind risk during week-2 may support enhanced wildfire risk in these
regions. There is, however, above normal precipitation anticipated across this
region albeit low probabilities, decreasing the certainty for potential
wildfire risk. Localized areas may have higher risk of wildfires depending on
where precipitation occurs during week-2.



The digging mid-level trough and cyclogenesis in the lee of the Rockies
increases chances for heavy snow across portions of the Plains and Rockies. The
GEFS Snow Water Equivalent (SWE) PET indicates chances for SWE to exceed the
85th climatological percentile across portions of the Plains. Meanwhile, the
ECENS PET indicates precipitation to exceed the 85th percentile across a broad
area in the north-central CONUS. Correspondingly, the raw ECENS indicates
30-40% chances for snow to exceed four inches across this region during the
early to middle of the period. Therefore, a slight risk of heavy snow is posted
for the northern and central Rockies and Plains for April 4-7.



In the southeastern CONUS, early in the period, briefly colder temperatures
(falling below the 15th climatological percentile) are forecast by the GEFS and
ECENS reforecast tools. The most anomalously  cold temperatures are forecast to
be along the Gulf Coast states. However, these temperatures are likely to fall
only to around 40 deg F. Further North, chances for a freeze are not forecast
by the dynamical models until the Ohio River Valley. In these areas, the
Midwest Regional Climate Center (MRCC) is indicating there is only mixed
susceptibility for vegetation and more than a month until the median last
freeze. Recent cooler temperatures have likely slowed the progression of spring
in these regions as well. Therefore, no corresponding much-below normal
temperature hazard is posted. Following the initial cold snap across the
Southeast, return flow off the Gulf of Mexico may develop. The ECENS is the
strongest and fastest to develop this potential and brings chances for heavy
precipitation (exceeding the 85th percentile) into the Southeast by the middle
of the period. The GEFS PET is not supportive of this solution, with limited
chances for exceeding the 85th climatological percentile in the eastern CONUS
throughout the period. Therefore, no corresponding heavy precipitation shape is
posted today but the pattern bears watching in the coming days.



For Alaska, the mean mid-level pattern is forecast to be fairly zonal, with
potentially positive 500 hPa height departures across the southern half of the
state. There is multi-model depiction of a series of surface lows forming over
the Bering Sea and Gulf of Alaska, although these are not expected to lead to
widespread hazardous conditions.

FORECASTER: Ryan Bolt

$$



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