690
FXUS21 KWNC 291937
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT APRIL 29 2024
SYNOPSIS: WEAK MID-LEVEL HIGH PRESSURE OVER THE SOUTHERN CONTIGUOUS U.S.
(CONUS) SUPPORTS INCREASED POTENTIAL FOR EXCESSIVE HEAT TO PORTIONS OF THE
SOUTHERN PLAINS AT THE BEGINNING OF THE WEEK-2 PERIOD. MEANWHILE, A MID-LEVEL
LOW PRESSURE SYSTEM PREDICTED OVER THE NORTHERN PLAINS EARLY IN WEEK-2,
ENHANCES THE LIKELIHOOD FOR HEAVY PRECIPITATION FOR PORTIONS OF THE NORTHERN
PLAINS AND UPPER MISSISSIPPI VALLEY. SURFACE LOW PRESSURE EAST OF THE CENTRAL
ROCKIES IS FAVORED TO BRING A RISK OF HIGH WINDS TO PORTIONS OF THE WESTERN AND
CENTRAL CONUS. CENTRAL FLORIDA HAS BEEN EXPERIENCING PERSISTENT DRYNESS.WITH
LITTLE ADDITIONAL PRECIPITATION FORECAST FOR THE REGION DURING EITHER WEEK-1 OR
WEEK-2 THERE ARE HIGHER CHANCES FOR RAPID ONSET DROUGHT (ROD).
HAZARDS
SLIGHT RISK FOR EXCESSIVE HEAT FOR PORTIONS OF THE SOUTHERN PLAINS, TUE-FRI,
MAY 7-10.
SLIGHT RISK FOR HEAVY PRECIPITATION FOR PORTIONS OF THE NORTHERN PLAINS AND
UPPER MISSISSIPPI VALLEY, TUE-WED, MAY 7-8.
SLIGHT RISK FOR HIGH WIND FOR PORTIONS OF THE GREAT BASIN, CENTRAL AND SOUTHERN
ROCKIES, DESERT SOUTHWEST, AND THE CENTRAL AND SOUTHERN PLAINS, TUE-FRI, MAY
7-10.
RISK FOR RAPID ONSET DROUGHT FOR PORTIONS OF CENTRAL FLORIDA.
DETAILED SUMMARY
FOR THURSDAY MAY 02 - MONDAY MAY 06:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY MAY 07 - MONDAY MAY 13: THERE IS POOR CONSENSUS AMONG ENSEMBLE
MODEL SOLUTIONS REGARDING THE 500-HPA HEIGHT ANOMALIES FOR WEEK-2. NONETHELESS
THERE IS COMMON GROUND WITH REGARD TO SOME KEY SYNOPTIC FEATURES THAT HAVE
IMPLICATIONS FOR POTENTIALLY EXTREME WEATHER DURING THE WEEK-2 FORECAST PERIOD.
BOTH THE GEFS AND ECMWF DEPICT WEAK POSITIVE HEIGHT ANOMALIES OVER THE SOUTHERN
PLAINS FOR MOST OF WEEK-2. AS WE GET TOWARDS THE MIDDLE OF MAY SUCH ANOMALOUS
RIDGING LEADS TO THE POTENTIAL FOR EXCESSIVE HEAT. THE ECMWF AND GEFS
PROBABILISTIC EXTREMES TOOLS (PETS) INDICATE AT LEAST A 20% PROBABILITY OF
MAXIMUM TEMPERATURES EXCEEDING THE 85TH PERCENTILE CLIMATOLOGICALLY, AND 95F
FOR MUCH OF THE SOUTHERN PLAINS, AND >100F FOR PORTIONS OF THE RIO GRANDE
VALLEY FOR MAY 7-10, RESULTING IN A SLIGHT RISK FOR EXCESSIVE HEAT FOR PORTIONS
OF THE SOUTHERN PLAINS AS FAR NORTH AS THE TEXAS HILL COUNTRY FOR THE DAYS
HIGHLIGHTED ABOVE.
A SECOND FEATURE THAT IS WELL-DEPICTED IN MODEL SOLUTIONS IS PERSISTENT SURFACE
LOW PRESSURE IN THE LEE OF THE ROCKIES FOR MOST OF THE FORECAST PERIOD. WHEN
PAIRED WITH SURFACE HIGH PRESSURE OVER THE NORTH PACIFIC, A BROAD TIGHT
PRESSURE GRADIENT IS DEPICTED OVER MUCH OF THE SOUTHWESTERN CONUS, WHICH WOULD
FAVOR HIGH WINDS FOR THE REGION. THIS IS SUPPORTED BY THE GEFS AND ECMWF WIND
PETS, WHICH GIVE AT LEAST A 20% PROBABILITY OF WIND SPEEDS EXCEEDING THE 85TH
PERCENTILE FOR PORTIONS OF THE WESTERN AND CENTRAL CONUS ROUGHLY FROM THE
SIERRA NEVADAS EAST TO WESTERN KANSAS AND OKLAHOMA, THUS A SLIGHT RISK FOR HIGH
WIND IS POSTED FOR PORTIONS OF THE GREAT BASIN, CENTRAL AND SOUTHERN ROCKIES,
DESERT SOUTHWEST, AND THE CENTRAL AND SOUTHERN PLAINS FOR MAY 7-10.
BOTH THE GEFS AND ECMWF ALSO DEPICT A PASSING SHORTWAVE TROUGH MOVING ALONG THE
NORTHERN TIER EARLY IN THE FORECAST PERIOD. THIS TROUGH MAY PAIR UP WITH THE
AFOREMENTIONED SURFACE LOW PRESSURE, BRINGING POTENTIALLY HEAVY PRECIPITATION
TO THE NORTHERN PLAINS. THE GEFS AND ECMWF PETS BOTH INDICATE AT LEAST A 20%
PROBABILITY OF 3-DAY PRECIPITATION TOTALS EXCEEDING THE 85TH PERCENTILE AND AT
LEAST A HALF INCH AT THE ONSET OF WEEK-2 CENTERED OVER THE DAKOTAS. SOLUTIONS
FROM THESE TWO MODELS DIFFER WITH REGARD TO THE TIMING OF THE HEAVIEST
RAINFALL, WITH THE ECMWF MOVING THE SHORTWAVE EAST MORE QUICKLY THAN THE GEFS.
ALTHOUGH MODELS INDICATE THE SYSTEM MOVING THROUGH THE REGION FAIRLY QUICKLY,
THE UNCALIBRATED ECENS SHOWS 3-DAY PRECIPITATION TOTALS EXCEEDING ONE INCH.
ADDITIONALLY, WITH THE POTENTIAL FOR THUNDERSTORMS A SLIGHT RISK FOR HEAVY
PRECIPITATION IS POSTED FOR PORTIONS OF THE NORTHERN PLAINS AND UPPER
MISSISSIPPI VALLEY FOR MAY 7-8.
IN THE SOUTHEAST, ABOVE-NORMAL TEMPERATURES AND NEAR- TO BELOW-NORMAL
PRECIPITATION IS FORECAST DURING WEEKS-1 AND 2. IN PARTS OF THE CENTRAL FLORIDA
PENINSULA SOIL MOISTURE LEVELS ARE DECLINING DUE TO LIMITED PRECIPITATION IN
RECENT WEEKS AND MONTHS. RECENT WEEKS HAVE SEEN AREAS OF ABNORMAL DRYNESS (D0)
DEVELOPING AND EXPANDING ACROSS BOTH OF THESE REGIONS. AS WE APPROACH THE
MIDDLE OF MAY, INCREASING SUN ANGLES AND TEMPERATURES IN THE 80-90 DEG F COULD
LEAD TO FURTHER DRYING OF SOILS AND POTENTIALLY LEAD TO DROUGHT CONDITIONS
ACROSS THIS REGION. THEREFORE, AN AREA OF RAPID ONSET DROUGHT (ROD) IS POSTED
FOR PORTIONS OF CENTRAL FLORIDA.
IN ALASKA, AS WE MOVE INTO THE MIDDLE OF MAY SNOWMELT SEASON IS UNDERWAY AND
FROZEN RIVERS WILL BEGIN TO BREAK UP IN THE NEAR FUTURE.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 SO NO FLOODING-RELATED HAZARDS ARE POSTED AT THIS TIME.
FORECASTER: DANNY BARANDIARAN
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