922   
FXUS21 KWNC 301839  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT APRIL 30 2024  
  
SYNOPSIS: MULTIPLE MODELS CONTINUE TO INDICATE MID-LEVEL HIGH PRESSURE ACROSS   
THE SOUTH-CENTRAL AND SOUTHEASTERN CONTIGUOUS U.S. (CONUS) FROM THE BEGINNING   
TO MIDDLE OF WEEK-2, SUPPORTING INCREASED CHANCES FOR EXCESSIVE HEAT ACROSS   
THESE REGIONS. HOWEVER, THERE CONTINUES TO BE SIGNIFICANT MODEL UNCERTAINTY   
REGARDING THE DETAILS OF THE MID-LEVEL PATTERN, WITH THE ECENS ENSEMBLE MEAN   
FAVORING HIGHER AMPLITUDE AND MORE EXPANSIVE MID-LEVEL HIGH PRESSURE THAN THE   
GEFS. MID-LEVEL LOW PRESSURE UPSTREAM ACROSS THE WESTERN AND NORTH-CENTRAL   
CONUS SUPPORTS INCREASED CHANCES FOR EPISODES OF HEAVY PRECIPITATION ACROSS   
PARTS OF THE MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, AND SOUTHERN   
APPALACHIANS AND ENHANCING FLOOD RISK IN SOME OF THESE AREAS.  
  
HAZARDS  
  
MODERATE RISK OF EXCESSIVE HEAT FOR PARTS OF THE SOUTHEAST AND LOWER   
MISSISSIPPI VALLEY, WED-FRI, MAY 8-10.  
  
SLIGHT RISK OF EXCESSIVE HEAT FOR PARTS OF THE SOUTHERN PLAINS, LOWER   
MISSISSIPPI VALLEY, AND SOUTHEAST, WED-SAT, MAY 8-11.  
  
SLIGHT RISK OF PERIODS OF HEAVY PRECIPITATION ACROSS PARTS OF THE MISSISSIPPI,   
OHIO, AND TENNESSEE VALLEYS, AND SOUTHERN APPALACHIANS, WED-SUN, MAY 8-12.  
  
SLIGHT RISK OF EPISODES OF HIGH WINDS FOR PARTS OF THE INTERIOR WEST, WED-FRI,   
MAY 8-10.  
  
POSSIBLE FLOODING OVER PARTS OF THE MISSISSIPPI VALLEY.  
  
DETAILED SUMMARY  
  
FOR FRIDAY MAY 03 - TUESDAY MAY 07:   
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
  
FOR WEDNESDAY MAY 08 - TUESDAY MAY 14: THE WEEK-2 FORECAST MEAN MID-LEVEL   
HEIGHT PATTERN FAVORS MORE EXPANSIVE POSITIVE 500-HPA HEIGHT ANOMALIES ACROSS   
THE GULF COAST COMPARED TO YESTERDAY. THIS TRANSLATES TO INCREASING SIGNALS FOR   
EXCESSIVE HEAT ACROSS THE REGION. A SLIGHT RISK OF EXCESSIVE HEAT IS   
HIGHLIGHTED ACROSS PARTS OF THE SOUTHERN PLAINS, LOWER MISSISSIPPI VALLEY, AND   
SOUTHEAST, MAY 8 TO 11, WHERE THE GEFS AND ECENS PROBABILISTIC EXTREMES TOOLS   
(PETS) SHOW AT LEAST A 20% CHANCE OF MAXIMUM TEMPERATURES EXCEEDING THE 90TH   
PERCENTILE, CLIMATOLOGICALLY, AND 90 DEG F (95 DEG F ACROSS WESTERN AND   
SOUTHERN TEXAS). AN EMBEDDED AREA IS DESIGNATED WITH A MODERATE RISK (40 TO 60%   
CHANCE) OF EXCESSIVE HEAT DUE TO INCREASING HEAT SIGNALS, BOTH IN DRY AIR   
TEMPERATURE AND HEAT INDEX TOOLS. THE ECENS (GEFS) PET SHOWS AT LEAST A 50%   
(40%) CHANCE OF MAXIMUM TEMPERATURES EXCEEDING THE 85TH PERCENTILE ACROSS THE   
LOWER MISSISSIPPI AND TENNESSEE VALLEYS, AND SOUTHEAST DURING THE 8 TO 10 DAY   
PERIOD (MAY 8-10).  THE NATIONAL BLEND OF MODELS (NBM) FORECASTS RECORD HIGH   
TEMPERATURES IN THE LOW TO MID 90S ACROSS THE LOWER MISSISSIPPI VALLEY, FLORIDA   
AND SOUTHERN CAROLINA AND TRIPLE DIGITS IN THE BIG BEND AREA IN TEXAS.    
  
UPSTREAM, MID-LEVEL TROUGHING CONTINUES TO BE PREDICTED, ALTHOUGH THERE   
CONTINUES TO BE SIGNIFICANT MODEL DIFFERENCES. THE ECENS ENSEMBLE MEAN   
CONTINUES TO FAVOR MID-LEVEL TROUGHING OVER THE NORTHWESTERN CONUS, WHEREAS THE   
GEFS COUNTERPART IS FURTHER EAST OVER THE NORTH-CENTRAL CONUS. DESPITE THESE   
DIFFERENCES, THIS PATTERN WOULD FAVOR SURFACE LOW FORMATION OVER THE CENTRAL   
CONUS, SHIFTING NORTHEASTWARD FROM THE BEGINNING TO MIDDLE OF WEEK-2. A SLIGHT   
RISK OF HEAVY PRECIPITATION IS POSTED FOR PERIODS OF HEAVY PRECIPITATION ACROSS   
PARTS OF THE MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, AND SOUTHERN   
APPPALACHIANS, MAY 8 TO 12, WHERE THE ECENS PET INDICATES AT LEAST A 20% CHANCE   
OF 3-DAY PRECIPITATION TOTALS EXCEEDING THE 85TH PERCENTILE AND ONE INCH AND   
WHERE POSITIVE PRECIPITATION ANOMALIES ARE INDICATED IN THE GEFS DAILY ENSEMBLE   
MEANS. A BROAD PERIOD IS DESIGNATED FOR THE RISK DUE TO UNCERTAINTY IN TIMING   
OF HEAVY PRECIPITATION, RATHER THAN THE EXPECTATION FOR HEAVY RAIN TO LAST   
MULTIPLE CONSECUTIVE DAYS. RECENT DETERMINISTIC GFS RUNS SHOW ENHANCED   
CONVECTIVE AVAILABLE POTENTIAL ENERGY (CAPE) THAT COULD BE CONDUCIVE FOR   
THUNDERSTORMS IN THE HIGHLIGHTED RISK AREA.  
  
SATURATED SOILS IN ADDITION TO EXPECTED ANTECEDENT HEAVY RAINFALL DURING WEEK-1   
AND PREDICTED WEEK-2 HEAVY RAINFALL SUPPORTS INCREASED LIKELIHOOD FOR FLOODING   
FOR PORTIONS OF THE MISSISSIPPI VALLEY. THIS HIGHLIGHTED FLOOD RISK AREA IS   
BASED ON WHERE THE NATIONAL WATER CENTER’S EXPERIMENTAL FLOOD OUTLOOK SHOWS   
POSSIBLE FLOODING IN THE 4-7 DAY PERIOD AND WHERE THERE IS A SLIGHT RISK OF   
HEAVY PRECIPITATION DURING WEEK-2.  
  
AFOREMENTIONED SURFACE LOW PRESSURE IN THE LEE OF THE ROCKIES PAIRED WITH   
SURFACE HIGH PRESSURE OVER THE NORTH PACIFIC SUPPORTS A BROAD AREA OF TIGHT   
PRESSURE GRADIENT ACROSS THE INTERIOR WEST AND RESULTANT INCREASED CHANCES FOR   
HIGH WINDS. A SLIGHT RISK OF EPISODIC HIGH WINDS IS DESIGNATED ACROSS PARTS OF   
THE MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, AND SOUTHERN APPALACHIANS, MAY 8   
TO 10. THE ECENS PET SHOWS AT LEAST A 20% CHANCE OF WIND SPEEDS EXCEEDING THE   
85TH PERCENTILE AND 20 MPH ACROSS THE HIGHLIGHTED RISK AREA. ANTICIPATED   
INCREASED POTENTIAL FOR HIGH WINDS COMBINED WITH DRY SOILS AND ANTECEDENT AND   
EXPECTED DRY CONDITIONS SUPPORTS ENHANCED RISK FOR WILDFIRES, ESPECIALLY ACROSS   
THE BIG BEND OF TEXAS, NEW MEXICO, AND ARIZONA, WHERE THE NATIONAL INTERAGENCY   
FIRE CENTER (NIFC) SHOWS MODERATE RISK OF SIGNIFICANT FIRE POTENTIAL BY DAY 7.  
  
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: MELISSA OU   
  
  
 
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