718
FXUS02 KWBC 040655
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
255 AM EDT SUN MAY 4 2025
VALID 12Z WED MAY 07 2025 - 12Z SUN MAY 11 2025
...MID TO LATE WEEK HEAVY RAINFALL POTENTIAL FOR THE CENTRAL GULF
COAST INTO THE SOUTHEAST...
..OVERVIEW
A BLOCKY PATTERN IN THE SHORT RANGE SHOULD FINALLY BEGIN TO BREAK
DOWN BY WEDNESDAY AS A PAIR OF UPPER LOWS OVER THE EAST AND WEST
WEAKEN AND SHIFT EAST. A STATIONARY OR SLOW MOVING FRONTAL BOUNDARY
DRAPED ACROSS THE SOUTHEAST MAY CONTINUE TO SUPPORT HEAVY RAINFALL
ACROSS THE REGION, AND ESPECIALLY ALONG THE GULF COAST. A
SHORTWAVE DROPPING IN FROM EAST-CENTRAL CANADA MAY BRIEFLY CUT OFF
ANOTHER LOW OVER THE NORTHEAST ON FRIDAY, WHILE THE WESTERN LOW
SHIFTS EAST AND EVENTUALLY SETTLES OVER THE SOUTHEAST NEXT WEEKEND.
THIS MAY CONTINUE THE THREAT FOR SHOWERS AND STORMS ACROSS THE
SOUTHEAST WELL INTO NEXT WEEKEND. UPPER RIDGING OVER THE WEST COAST
WILL BUILD INTO THE ROCKIES/CENTRAL U.S. AS A PACIFIC TROUGH NEARS
THE WEST COAST NEXT SUNDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST MODELS AND ENSEMBLES ARE IN GOOD AGREEMENT THROUGH ABOUT
FRIDAY ON THE OVERALL PATTERN EVOLUTION DURING THE MEDIUM RANGE
PERIOD, BUT STILL WITH PLENTY OF UNCERTAINTY IN THE DETAILS. THE
MODELS HAVE TRENDED TOWARDS MORE AGREEMENT ON THE SECOND POTENTIAL
UPPER LOW OVER THE NORTHEAST, BUT DIFFER IN TIMING AND PLACEMENT AS
IT EXITS NEXT WEEKEND. ALSO SOME UNCERTAINTY IN THE STRENGTH OF
ADDITIONAL WEAKER SHORTWAVE ENERGY OVER EASTERN CANADA WHICH
AFFECTS THE STRENGTH OF ANY RIDGING OVER THE NORTHEAST BEHIND THE
UPPER LOW. ELSEWHERE, MUCH OF THE GUIDANCE NOW SHOWS THE MAIN CORE
OF ENERGY FROM THE INITIAL WEST LOW HANGING BACK OVER THE
SOUTHEAST, AT LEAST THROUGH NEXT WEEKEND, BUT SUBTLE DIFFERENCES IN
THE POSITION OF THIS WOULD HAVE IMPACTS ON SENSIBLE WEATHER
THREATS. THERE IS SOME CONSIDERABLE TIMING DIFFERENCES WITH THE
NEXT TROUGH INTO THE WEST BY SATURDAY AND THE CMC WAS THE OUTLIER
THIS CYCLE AS IT CLOSES OFF A SOUTHERN STREAM LOW THAT DRIFTS
WESTWARD INTO THE PACIFIC AND NORTHERN STREAM ENERGY DRAGS ACROSS
THE NORTHWEST. THE GFS, ECMWF, AND ENSEMBLE MEANS SHOW MORE
ELONGATED TROUGHING APPROACHING THE COAST, THOUGH THE ECMWF WAS
SLIGHTLY FASTER.
THE WPC PROGS FOR TONIGHT WERE ABLE TO USE A GENERAL MODEL BLEND
FOR DAYS 3-5 WITH ENOUGH AGREEMENT. TRANSITIONED TO 40-60 PERCENT
OF THE ENSEMBLE MEANS DAY 6 AND 7 TO MITIGATE BIGGER DIFFERENCES IN
THE LATE PERIOD FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
BY WEDNESDAY, THE START OF THE PERIOD, THE HEAVIEST RAINS ARE
LIKELY TO FOCUS ALONG THE CENTRAL GULF COAST POOLING ALONG A
FRONTAL BOUNDARY. FOR THE DAY 4/WEDNESDAY ERO, MAINTAINED A SLIGHT
RISK FROM FAR SOUTHEAST TEXAS INTO SOUTHERN MISSISSIPPI AND
SOUTHERN ALABAMA, AS HEAVY RAIN RATES AND TRAINING COULD CAUSE
SCATTERED FLASH FLOODS, BUT THE POTENTIAL MAY BE LIMITED SLIGHTLY
BY DRIER ANTECEDENT CONDITIONS AND HIGHER FLASH FLOOD GUIDANCE.
HEAVY RAIN COULD PERSIST INTO THURSDAY ALONG THE CENTRAL GULF COAST
AND INTO PARTS OF THE SOUTHEAST, BUT OPTED FOR JUST A MARGINAL
RISK RIGHT NOW GIVEN LINGERING GUIDANCE UNCERTAINTY AND DRY SOILS.
SOME RAIN AND STORMS ARE LIKELY TO PERSIST ACROSS THE SOUTHEAST IN
GENERAL INTO LATE WEEK AND THE WEEKEND AS WELL.
UNDER THE DEPARTING EASTERN UPPER LOW ON WEDNESDAY, WRAPBACK
MOISTURE AND INSTABILITY ON THE BACKSIDE OF THE ASSOCIATED SURFACE
LOW COULD LEAD TO LOCALLY HEAVY RAIN IN THE SENSITIVE TERRAIN OF
THE INTERIOR NORTHEAST. A MARGINAL RISK REMAINS IN PLACE FOR THE
WEDNESDAY (DAY 4) ERO PERIOD.
THE UPPER LOW OVER THE SOUTHWEST EARLY IN THE PERIOD WILL RESULT
IN BELOW TO WELL BELOW NORMAL TEMPERATURES FOR THE SOUTHWEST AND
SOUTH-CENTRAL PLAINS WHERE DAYTIME HIGHS COULD BE 15-20 DEGREES
BELOW NORMAL. THIS SHOULD MODERATE WITH TIME BUT MAY STILL REMAIN
MODESTLY BELOW NORMAL INTO LATE WEEK FOR THE SOUTHERN PLAINS. UPPER
RIDGING BUILDING OVER THE WEST AS THE UPPER LOW SHIFTS EAST WILL
ALLOW FOR EXPANDING COVERAGE OF ABOVE NORMAL TEMPERATURES THERE AS
NEXT WEEK PROGRESSES, INCLUDING 100 DEGREE TEMPERATURES IN THE
DESERT SOUTHWEST. ABOVE AVERAGE TEMPERATURES WILL STRETCH INTO THE
NORTHERN TIER AS WELL, WITH HIGHS REACHING THE 70S AND 80S IN THE
NORTHERN PLAINS TO UPPER MIDWEST. SLIGHTLY ABOVE NORMAL
TEMPERATURES MAY MOVE INTO THE NORTHEAST NEXT WEEKEND.
SANTORELLI
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page