738
FXUS02 KWBC 160700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT FRI MAY 16 2025
VALID 12Z MON MAY 19 2025 - 12Z FRI MAY 23 2025
...SEVERE WEATHER AND FLASH FLOODING FORECAST FOR PARTS OF THE
CENTRAL U.S. MONDAY-TUESDAY...
...HAZARDOUS AND RECORD HEAT COULD CONTINUE ESPECIALLY ACROSS TEXAS
AND FLORIDA INTO MID-NEXT WEEK...
..OVERVIEW
THE PRIMARY WEATHER FEATURE NEXT WEEK WILL BE AN UPPER TROUGH/LOW
OVER THE ROCKIES MONDAY THAT TRACKS EAST AS THE WEEK PROGRESSES
ALONG WITH ITS ASSOCIATED SURFACE LOW PRESSURE/FRONTAL SYSTEM. THIS
PATTERN WILL PROVIDE AMPLE LIFT AND INSTABILITY FOR RAIN AND
THUNDERSTORMS IN THE PLAINS, MISSISSIPPI VALLEY, AND OHIO VALLEY
EARLY WEEK AND SPREADING INTO THE EAST FOR MIDWEEK AND BEYOND.
MEANWHILE A SUBTROPICAL UPPER RIDGE WILL CONTINUE TO CAUSE HOT
CONDITIONS TO AREAS OF THE SOUTHEAST, PARTICULARLY INTO SOUTHERN
TEXAS AND FLORIDA, WHERE THE HEAT COULD BE HAZARDOUS AND/OR RECORD
SETTING.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE BEGINS THE MEDIUM RANGE PERIOD MONDAY IN REASONABLY
GOOD AGREEMENT WITH THE PRIMARY UPPER TROUGH AND EMBEDDED UPPER
LOW(S) IN THE INTERIOR WEST AND SPINNING UP A SURFACE LOW IN THE
CENTRAL PLAINS. MODELS DIVERGE RATHER QUICKLY WITH THE DETAILS OF
THE ENERGY ALOFT, LEADING TO DIFFERENCES IN THIS SURFACE LOW TRACK
AND ANOTHER LOW DEVELOPING OVER THE SOUTHERN PLAINS BY TUESDAY.
DYNAMICAL AND ML MODELS ALIKE SHOW A VARIETY OF SOLUTIONS REGARDING
IF THE UPPER LOW SWITCHES TO BE PART OF A NORTHEASTERN TROUGH BY
TUESDAY/WEDNESDAY, WHICH DEPENDS ON HOW MUCH ENERGY LINGERS ATOP
ONTARIO/QUEBEC ON THE BACK END OF AN UPPER LOW EJECTING EAST.
12/18Z GFS RUNS SHOWED THIS TYPE OF PATTERN, WHERE THE INITIALLY
WESTERN ENERGY QUICKLY COMBINES WITH THE EASTERN ENERGY, WHICH
LEADS TO LOW PRESSURE TRACKING EASTWARD MUCH FASTER THAN SLOWER
GUIDANCE LIKE THE ECMWF. DESPITE THE VARIETY IN SOLUTIONS EVEN WITH
THE AI/ML GUIDANCE, THE PRIMARY RESULT WAS THAT IN GENERAL THEY
WERE NOT AS FAST WITH THE LOW TRACK AS THE GFS RUNS. THUS FOR A
FAVORED MIDDLE GROUND WPC FORECAST, REMOVED ANY INCLUSION OF THE
GFS FROM THE MODEL BLEND, WITH SOME ECMWF INCLUSION BUT FAVORING
THE ENSEMBLE MEANS IN PARTICULAR. THIS WAS PRETTY AGREEABLE WITH
THE PREVIOUS FORECAST'S TIMING. THE NEWER 00Z GFS IS SLOWER THAN
THE 12Z AND 18Z RUNS WITH THE LOW, AND THE 00Z ECMWF TRACKED
FASTER, SO THERE IS SOME CONVERGENCE IN THOSE SOLUTIONS. THE 00Z
GEFS MEAN MAY ALIGN WELL WITH THE PREFERRED TIMING (AFTER THE 12Z
AND 18Z GEFS MEANS WERE A LITTLE FAST, IN THE VEIN OF THE GFS).
HOWEVER, THE NEW 00Z CMC DIGS THE UPPER LOW FARTHER SOUTHWEST INTO
THE GREAT BASIN EVEN BY MONDAY TO END UP WITH A MUCH SLOWER LOW
TRACK.
..WEATHER/HAZARDS HIGHLIGHTS
THE NOTABLE SURFACE LOW PRESSURE SYSTEM CONSOLIDATED OVER THE
CENTRAL PLAINS BY MONDAY WILL DRAW IN ABOVE AVERAGE MOISTURE (WITH
PRECIPITABLE WATER VALUES AROUND THE 90TH PERCENTILE FOR THIS TIME
OF YEAR) AND AMPLE INSTABILITY AHEAD OF ITS ASSOCIATED COLD FRONT.
THE UPPER LOW SPINNING ALOFT WILL PROVIDE GOOD DYNAMICAL LIFT, AND
THIS COMBINATION OF INGREDIENTS WILL LEAD TO WIDESPREAD RAIN AND
THUNDERSTORMS AND MESOSCALE CONVECTIVE SYSTEMS, WITH BEST CHANCES
SLOWLY PROGRESSING EAST FROM THE CENTRAL TO EAST-CENTRAL TO EASTERN
U.S. AS NEXT WEEK PROGRESSES. THE GREATEST CHANCES FOR HEAVY RAIN
CAUSING FLASH FLOODING LOOK TO BE ACROSS THE MID-MISSISSIPPI AND
WESTERN OHIO VALLEYS MONDAY AND TUESDAY, AS MOISTURE AND
INSTABILITY POOL NEAR A WARM FRONT STRETCHING WEST-EAST THAT COULD
PROMOTE TRAINING STORMS. THUS SLIGHT RISKS ARE IN PLACE FOR THE DAY
4/MONDAY AND DAY 5/TUESDAY ERO OVER PRETTY SIMILAR AREAS BEFORE
THE UPPER/SURFACE LOWS EJECT EASTWARD. BROAD MARGINAL RISKS
SURROUND THE SLIGHTS TO THE SOUTH AND EAST WHERE CONVECTION MAY BE
MORE SCATTERED, AND ON MONDAY A MARGINAL CURLS BACK WEST CLOSER TO
THE OW TRACK. SEVERE WEATHER IS ALSO POSSIBLE PER THE STORM
PREDICTION CENTER, AS THEY DELINEATE POSSIBLE SEVERE AREAS ON
MONDAY FOR THE SOUTH-CENTRAL PLAINS TOWARD THE LOWER/MIDDLE
MISSISSIPPI VALLEY ON TUESDAY. RAIN AND THUNDERSTORM POTENTIAL
SHOULD PRESS TOWARD THE EASTERN SEABOARD BY MID TO LATE WEEK.
SOME PRECIPITATION IS FORECAST IN THE INTERMOUNTAIN WEST UNDER THE
UPPER TROUGH/LOW FOR THE FIRST HALF OF NEXT WEEK. THE COOL
TEMPERATURES ALOFT COULD LEAD TO MAY SNOW IN HIGHER ELEVATIONS OF
THE ROCKIES PARTICULARLY MONDAY. CONVECTIVE SHOWERS ARE POSSIBLE
NEAR THE FOUR CORNERS REGION. MEANWHILE ROUNDS OF MODEST
PRECIPITATION MAY BE POSSIBLE IN THE NORTHWEST. LIGHT RAIN MAY
LINGER IN THE NORTHEAST EARLY NEXT WEEK UNDER THE INFLUENCE OF A
NORTHERN TROUGH.
WARM TO HOT TEMPERATURES ARE LIKELY ACROSS THE SOUTHEASTERN U.S.
AS THE SUBTROPICAL UPPER RIDGE REACHES THE REGION. SOUTHERN TEXAS
IN PARTICULAR WILL REMAIN HOT, WITH TEMPERATURES WELL INTO THE 100S
LEADING TO MAJOR TO EXTREME HEATRISK. THE FLORIDA PENINSULA SHOULD
SEE WARM TEMPERATURES IN THE MID TO UPPER 90S. BOTH AREAS COULD
SEE RECORD OR NEAR RECORD WARM LOWS AND HIGHS. MEANWHILE THE TROUGH
ALOFT WILL PROMOTE BELOW NORMAL TEMPERATURES, ESPECIALLY FOR
HIGHS, ACROSS THE INTERIOR WEST MONDAY AND INTO THE NORTHERN PLAINS
TUESDAY. BELOW AVERAGE HIGHS BY AROUND 10 DEGREES ARE ALSO
POSSIBLE IN THE NORTHERN TIER. AS THE TROUGH TRACKS EAST, COOLER
THAN AVERAGE TEMPERATURES SHOULD SHIFT INTO THE EASTERN THIRD OF
THE COUNTRY UNDER IT. THIS MAY ALSO MODERATE THE TEMPERATURES
SOMEWHAT IN THE SOUTH. BUT UPPER RIDGING POKING INTO THE WEST WILL
RAISE TEMPERATURES TO ABOVE NORMAL THERE BY LATER WEEK, BRINGING
HIGHS WELL INTO THE 100S FOR THE DESERT SOUTHWEST.
TATE
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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