452
FXUS21 KWNC 071805
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT May 07 2024

SYNOPSIS: Mid-level high pressure over the West Coast and mostly zonal flow
over the contiguous U.S. (CONUS) results in a relatively tranquil period of
weather for week-2. Early in the period, a stalled frontal boundary over the
Gulf Coast leads to the potential for heavy precipitation for portions of the
Southeast U.S.

HAZARDS

Slight risk for heavy precipitation for portions of eastern Texas, Lower
Mississippi Valley, Tennessee Valley, Southern Appalachians, Mid-Atlantic, and
Southeast U.S., Wed-Fri, May 15-17.

DETAILED SUMMARY

FOR FRIDAY MAY 10 - TUESDAY MAY 14:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR WEDNESDAY MAY 15 - TUESDAY MAY 21: At the outset of week-2, ensemble models
favor moderate ridging (troughing) over the West Coast (Great Plains) as
depicted by 500-hPa height anomalies. The GEFS favors a broad trough, while the
ECMWF features a narrower trough over the Great Plains. Model solutions move
this trough eastward quickly, and favor the development of a mid-level ridge
over the Great Plains by the end of the forecast period. This emerging ridge
may lead to a risk for excessive heat for the southern CONUS late in week-2,
however there is still too much uncertainty regarding this outcome so no
heat-related hazard is posted at this time.



Ensemble models have come into better agreement today regarding the timing and
location of potentially heavy precipitation associated with a stalled frontal
boundary along the Gulf Coast. Both the GEFS and ECMWF Probabilistic Extremes
Tools (PETs) indicate at least a 20% probability of 3-day accumulated
precipitation exceeding the 85th percentile and 1 inch for portions of the
southeastern CONUS for May 15-17. The ECMWF is especially bullish, with much
wider coverage of the area indicated for 1 inch total and over 2 inches
possible for portions of the Louisiana coast. Therefore a slight risk for heavy
precipitation is posted for portions of eastern Texas, Lower Mississippi
Valley, Tennessee Valley, Southern Appalachians, Mid-Atlantic, and Southeast
U.S. for the above dates.



In Alaska, as we move into the middle of May snowmelt season is underway and
frozen rivers are beginning to break up. This leads to the potential for river
flooding related to ice-jams. We continue to monitor the situation but
currently there are no indications of impending major river break-ups or
serious threat of ice-jamming so no flooding-related hazards are posted at this
time. Caution should be exercised however; river break-up can be unpredictable
and local conditions can change quickly.

FORECASTER: Danny Barandiaran

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