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FXUS21 KWNC 081758
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT April 08 2025

SYNOPSIS: At the beginning of the forecast period a surface low pressure system
over Quebec brings the potential for high winds to much of the Great Lakers and
Northeast U.S. Surface low pressure is favored to develop over the Great Plains
during week-2, bringing the potential for high winds to portions of the
Southern and Central Plains as well as the Central and Southern Rockies.
Potentially heavy precipitation is depicted by multiple model ensembles east of
this surface low pressure, possibly prolonging flooding concerns in the Ohio
and Mississippi watersheds.

HAZARDS

Slight risk of heavy precipitation for portions of the Ohio, Tennessee, Lower
and Middle Mississippi Valleys, and Southern and Central Plains, Thu-Mon, Apr
17-21.

Slight risk of high winds for the Southern Plains and Southern Rockies, as well
as portions of the Desert Southwest, Central Rockies, Central Plains, and Lower
and Middle Mississippi Valley, Wed-Thu, Apr 16-17.

Slight risk of high winds for the Great Lakes, Central Appalachians, and
Northeast U.S., as well as portions of the Ohio Valley and Mid-Atlantic,
Wed-Thu, Apr 16-17.

Flooding possible for portions of the Ohio, Tennessee, and Middle and Lower
Mississippi Valleys.

DETAILED SUMMARY

FOR FRIDAY APRIL 11 - TUESDAY APRIL 15:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR WEDNESDAY APRIL 16 - TUESDAY APRIL 22: Model ensembles depict a very
transient synoptic picture during the week-2 period characterized by multiple
weak shortwave troughs moving across the Contiguous U.S. (CONUS). At the outset
of week-2 low pressure at the surface and aloft is favored over Quebec, setting
up a tight pressure gradient and the potential for high winds over the
northeastern CONUS during the early portion of the forecast period. This is
supported by the ECMWF Probabilistic Extremes Tool (PET), which indicates at
least a 20% chance of 3-day maximum wind speed exceeding the 85th
climatological percentile and at least 20mph over much of the Great Lakes,
Northeast U.S., and Central Appalachians as well as portions of the
Mid-Atlantic and Ohio Valley early in the forecast period. This low pressure is
favored to exit the region quickly, with models indicating the strongest signal
for high winds during Apr 16-17, warranting the continuation of a slight risk
of high winds for the regions listed for Apr 16-17.



Multiple models also favor the development of surface low pressure in the lee
of the Rockies early in week-2. This feature is not very strong in ensemble
means but is fairly persistent and model solutions form an expansive rain
shield east of the low pressure center, bringing the potential for heavy
precipitation over some regions recently affected by excessive rain.
Uncalibrated probabilities from the ECMWF indicate at least a 20% chance of
3-day precipitation totals to exceed 1 inch for most of week-2, particularly
from the 17th onward. This is also well indicated in the ECMWF PET. Curiously,
the GEFS PET does not show much signal for excessive precipitation, but the
GEFS ensemble mean shows similar total accumulations to the ECMWF. Despite some
uncertainty due to these differences in the forecast tools, there is sufficient
evidence to warrant a slight risk of heavy precipitation for portions of the
Ohio, Tennessee, Lower and Middle Mississippi Valleys, and Southern and Central
Plains for Apr 17-21. At the outset of week-2 surface high pressure over the
southeastern CONUS teams up with this surface low to form a tight pressure
gradient over the Southern and Central Plains. 10m wind forecasts from the
ECMWF and GEFS indicate periodic high winds over much of Texas and extending
westward into New Mexico and northward well into the Central Plains. This is
also indicated by the ECMWF PET, which shows at least a 20% chance of 3-day
maximum wind speed exceeding the 85th percentile and 20mph early in the
forecast period. The low pressure center is favored to move quickly eastward,
along with weakening surface pressure gradients, therefore a slight risk of
high winds is posted for the Southern Plains and Southern Rockies, as well as
portions of the Desert Southwest, Central Rockies, Central Plains, and Lower
and Middle Mississippi Valley for Apr 16-17, after which chance of high winds
diminish. Finally, given the copious antecedent rainfall and recurring flooding
concerns in this region, a flooding possible hazard is posted for portions of
the Ohio and Middle Mississippi Valleys due to the potential for new and
renewed rises in river levels. While main channels are already very high, and
thus likely wont respond too much to additional precipitation, tributaries and
streams will be more susceptible to flooding or flash flooding.



In Alaska, multiple models depict a surface low pressure system tracking across
the Gulf of Alaska during week-2. This system is depicted with strong pressure
gradients and developing strong winds that may potentially affect coastal areas
of Southeast Alaska. This situation will be monitored closely, but no
associated hazard is posted at this time. In addition, as spring continues and
daily incoming solar radiation flux totals increase, ice-bound rivers will
begin to break up. There is no associated hazard posted at this time but this
situation will be closely monitored in the coming days and weeks as conditions
can quickly change, leading to the potential for ice jams and associated
flooding.

FORECASTER: Danny Barandiaran

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