858
FXUS21 KWNC 091817
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 09 2025
SYNOPSIS: AN AREA OF MID-LEVEL LOW PRESSURE OVER THE WESTERN CONTIGUOUS U.S.
(CONUS) AT THE OUTSET OF WEEK-2 IS FAVORED TO SHIFT EASTWARD, LEADING TO
INCREASED POTENTIAL FOR HEAVY PRECIPITATION AND NEW OR RENEWED FLOODING OVER
PORTIONS OF THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY AND THE
SURROUNDING REGIONS. MULTIPLE DAYS OF ANOMALOUSLY WARM TEMPERATURES MAY REACH
HAZARDOUS THRESHOLDS AT TIMES ACROSS PARTS OF THE RIO GRANDE VALLEY AND PARTS
OF FLORIDA BENEATH DEVELOPING MID-LEVEL HIGH PRESSURE.
HAZARDS
SLIGHT RISK OF EXCESSIVE HEAT FOR PORTIONS OF THE RIO GRANDE VALLEY, SAT-MON,
MAY 17-19.
SLIGHT RISK OF EXCESSIVE HEAT FOR PORTIONS OF FLORIDA, SAT-MON, MAY 17-19.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF SOUTHERN PLAINS, LOWER AND
MIDDLE MISSISSIPPI, LOWER OHIO, AND TENNESSEE VALLEYS, SAT-MON, MAY 17-19.
FLOODING POSSIBLE FOR PORTIONS OF THE SOUTHERN PLAINS AND LOWER MISSISSIPPI
VALLEY.
DETAILED SUMMARY
FOR MONDAY MAY 12 - FRIDAY MAY 16:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY MAY 17 - FRIDAY MAY 23: ENSEMBLE MEANS FROM THE GEFS, ECENS, AND
CMCE FOR 500-HPA HEIGHTS DEPICT AN AMPLIFIED TROUGH COMING ASHORE OVER THE WEST
COAST DURING WEEK-1 AND SPREADING OVER THE WESTERN CONUS BY THE OUTSET OF
WEEK-2, ALONG WITH LEE CYCLOGENESIS AND A SURFACE LOW OVER THE GREAT PLAINS.
THIS SYNOPTIC SETUP FAVORS MOIST SOUTHERLY FLOW OFF THE GULF AND INTO THE
SOUTHERN PLAINS AND MISSISSIPPI VALLEY, INCREASING THE POTENTIAL FOR HEAVY
PRECIPITATION ACROSS A REGION REPEATEDLY IMPACTED BY ROUNDS OF EXCESSIVE
RAINFALL. THE GEFS, ECENS, AND CMCE PROBABILISTIC EXTREMES TOOLS (PETS) FOR
HEAVY PRECIPITATION ALL INDICATE AT LEAST A 20% CHANCE OF 3-DAY PRECIPITATION
TOTALS EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND AT LEAST 1 INCH FOR
MUCH OF THE FORECAST PERIOD ACROSS A PORTION OF THE SOUTHERN AND CENTRAL PLAINS
AND INTO THE LOWER AND MIDDLE MISSISSIPPI VALLEY. TOOLS HAVE GENERALLY SHIFTED
PRECIPITATION FURTHER NORTHEAST RELATIVE TO YESTERDAY. THIS WOULD BE WELCOMED
ACROSS EASTERN TEXAS AND LOUISIANA STILL DEALING WITH ONGOING FLOODING FROM THE
PAST WEEK’S RAINFALL. HOWEVER, THE SIGNALS PERSIST ACROSS MUCH OF ARKANSAS,
NORTHEAST TEXAS AND INTO MIDDLE MISSISSIPPI, LOWER OHIO, AND TENNESSEE VALLEYS.
THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED FOR THIS REGION FOR
MAY 17-19.
THE SOUTHERN PORTIONS OF THE HIGHLIGHTED SLIGHT RISK OF HEAVY PRECIPITATION
HAVE HAD WIDESPREAD AMOUNTS OF FOUR OR MORE INCHES OF RAIN IN THE PAST SEVEN
DAYS AND EIGHT OR MORE IN THE LAST 30. THE CURRENT 7 DAY QPF SHOWS A DRY PERIOD
DURING WEEK-1 WHICH MAY ALLOW TIME FOR SOILS TO RECOVER BUT ANOTHER ROUND OF
HEAVY PRECIPITATION COULD LEAD TO RENEWED CHANCES FOR FLOODING. THEREFORE, A
FLOODING POSSIBLE RISK IS FORECAST FOR PARTS OF THE SOUTHERN PLAINS AND LOWER
MISSISSIPPI VALLEY.
POSITIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST TO SPREAD INTO THE SOUTHERN
PLAINS AND ACROSS THE GULF BY LATE WEEK-1 AND INTO WEEK-2. ANOMALOUSLY WARM
TEMPERATURES ARE INDICATED BY MULTIPLE MODELS FOR THE LOWER RIO GRANDE VALLEY
AND IN PARTS OF FLORIDA LATE IN WEEK-1 AND EXTENDING INTO EARLY WEEK-2 AS A
RESULT OF THIS MID-LEVEL RIDGE. THE MAXIMUM TEMPERATURE PETS SHOW A STRONG
SIGNAL FOR ANOMALOUS WARMTH IN PERCENTILE SPACE, 30-50% CHANCES OF EXCEEDING
THE 85TH CLIMATOLOGICAL PERCENTILE, ACROSS BOTH FLORIDA AND THE RIO GRANDE
VALLEY. IN SOUTHERN TEXAS, THE PETS ALSO SHOW 20-40% CHANCES FOR TEMPERATURES
TO EXCEED 100 DEGF, APPROACHING 105. THE NWS HEAT RISK TOOL INDICATES MAJOR
HEAT RISK DEVELOPING ALONG THE RIO GRANDE AT THE END OF WEEK-1. MULTIPLE DAYS
OF TEMPERATURES NEAR EXCESSIVE HEAT THRESHOLDS MAY RESULT IN EXPANDED HEAT RISK
BY THE BEGINNING OF WEEK 2. IN FLORIDA, THE GEFS DEPICTS WIDESPREAD 95 DEGF
ACROSS FLORIDA EARLY IN THE WEEK-2 PERIOD WITH BIAS-CORRECTED APPARENT
TEMPERATURE TOOLS SHOWING 20-30% CHANCES OF APPARENT TEMPERATURES EXCEEDING 100
DEGF. THEREFORE, SLIGHT RISKS OF EXCESSIVE HEAT ARE HIGHLIGHTED FOR PORTIONS OF
THE RIO GRANDE VALLEY AND FLORIDA, MAY 17-19. MODELS ARE SHOWING ELEVATED DEW
POINTS ALONG THE SOUTHERN TEXAS GULF COAST IN ADDITION TO THE BUILDING HEAT
WHICH MAY LEAD TO ELEVATED APPARENT TEMPERATURES IN THE AREA AND SO THE
EXCESSIVE HEAT RISK SHAPE WAS EXPANDED EAST TO THE GULF COAST TODAY. PARTS OF
THE SOUTHWESTERN AND SOUTH-CENTRAL CONUS WILL NEED TO BE MONITORED THROUGHOUT
WEEK-2 AS THE ECENS AND GEFS FORECAST A BUILDING MID-LEVEL RIDGE ACROSS THE
REGION BY THE END OF WEEK-2.
AS SPRING CONTINUES AND DAILY INCOMING SOLAR RADIATION FLUX TOTALS INCREASE,
ICE-BOUND RIVERS ARE BEGINNING TO BREAK UP IN ALASKA. 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: RYAN BOLT
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page