566
FXUS02 KWBC 280757
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
357 AM EDT TUE APR 28 2026
VALID 12Z FRI MAY 01 2026 - 12Z TUE MAY 05 2026
...HEAVY RAIN AND FLOODING THREAT INCREASING FROM CENTRAL TEXAS TO
THE LOWER MISSISSIPPI VALLEY LATER THIS WEEK...
..OVERVIEW
A PERSISTENT UPPER LEVEL LOW SPINNING OVER SOUTHEAST CANADA WILL
KEEP CONDITIONS COOL AND UNSETTLED THROUGH THE WEEKEND INTO EARLY
NEXT WEEK. MEANWHILE, A POTENT STORM SYSTEM WITH PLENTY OF MOISTURE
TO WORK WITH WILL SET THE STAGE FOR HEAVY RAIN AND POTENTIAL
FLOODING CONCERNS FROM THE SOUTHERN PLAINS TO THE SOUTHEAST LATE
WEEK INTO THE WEEKEND. LOOKING AHEAD TO NEXT WEEK, ANOTHER PACIFIC
LOW MAY BRING SHOWERS TO PARTS OF THE GREAT BASIN AND INTERMOUNTAIN
WEST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE CONTINUES TO HAVE A FAIRLY DECENT HANDLE ON THE
EVOLUTION OF AN INCREASINGLY AMPLIFIED BLOCKING PATTERN ACROSS THE
LOWER 48 FROM LATER THIS WEEK THROUGH EARLY NEXT WEEK. THIS PATTERN
IS HIGHLIGHTED BY A LARGE CUT-OFF UPPER LOW SPINNING OVER
SOUTHEAST CANADA, WITH A STRONG SHORTWAVE SLIDING ACROSS THE
SOUTHERN TIER OF THE U.S. REINFORCING BROADLY DEEP TROUGHING ACROSS
THE EASTERN U.S. AT THE SAME TIME, MODELS ARE IN GOOD AGREEMENT
WITH THE DEVELOPMENT OF A CLASSIC REX BLOCK ALONG THE WEST COAST
LATER THIS WEEKEND INTO EARLY NEXT WEEK. WHILE THERE ARE STILL SOME
SPATIAL AND TEMPORAL DIFFERENCES OF THESE PATTERN DRIVERS AMONGST
THE VARYING MODEL SUITES, THE DIFFERENCES ARE SMALL ENOUGH TO STILL
BE ABLE TO FORM A REASONABLE CONSENSUS IN LINE WITH THE NATIONAL
BLEND OF MODELS.
THE WPC PRODUCT SUITE WAS DERIVED FROM A BLEND OF DETERMINISTIC
AND MACHINE LEARNING GUIDANCE, WITH AN INCREASE IN WEIGHTING OF THE
EC AND GEFS ENSEMBLE MEANS FOR THE LATTER HALF OF THE PERIOD. THIS
COMPOSITE HELPED TO MAINTAIN CONTINUITY WHILE SMOOTHING OUT MODEL
DIFFERENCES, ESPECIALLY LATER IN THE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
AN OCCLUDING COASTAL LOW PRESSURE SYSTEM PIVOTING FROM NORTHERN
NEW ENGLAND INTO SOUTHEAST CANADA WILL CONTINUE TO FOSTER COOL,
BREEZY, AND SHOWERY CONDITIONS ACROSS PARTS OF THE NORTHEAST FRIDAY
INTO THE WEEKEND. A LITTLE SNOW STILL CAN'T BE RULED OUT ACROSS
THE HIGHER ELEVATIONS OF NORTHERN NEW ENGLAND OR THE INTERIOR
NORTHEAST AS COLDER AIR WRAPS IN ON THE BACKSIDE OF THE LOW, BUT
THE RISK IS LOWER THAN PREVIOUS DAYS. TEMPERATURES FROM THE NORTH-
CENTRAL U.S. TO MUCH OF THE EASTERN U.S. WILL RUN SEVERAL DEGREES
BELOW SEASONAL NORMS OVER THE COURSE OF THE WEEKEND, SETTING UP THE
POTENTIAL FOR NIGHTTIME FROST AND FREEZE CONCERNS OVER PARTS OF
THE REGION.
MEANWHILE, A POTENT SOUTHERN STREAM PACIFIC LOW SCOOTING ALONG THE
U.S./MEXICO BORDER WILL EJECT INTO THE SOUTHERN PLAINS ON FRIDAY
AS THIS DISTURBANCE PROGRESSES EASTWARD, IT WILL BEGIN TO INTERACT
WITH A LINGERING FRONTAL BOUNDARY. ANOMALOUS PACIFIC AND GULF
MOISTURE OVERRUNNING THIS FRONTAL ZONE COMBINED WITH IMPRESSIVE
DYNAMICS AND FORCING FROM A STRONG UPPER JET WILL LEAD TO THE
INCREASING POTENTIAL FOR SIGNIFICANT RAINFALL AND SCATTERED
FLOODING CONCERNS FROM CENTRAL TEXAS TO THE LOWER MISSISSIPPI
VALLEY FRIDAY INTO EARLY SATURDAY. GIVEN AN ENVIRONMENT FAVORABLE
FOR HEAVY RAINFALL, MODELS CONTINUE TO PRODUCE A GROWING SIGNAL FOR
WIDESPREAD RAINFALL TOTALS OF 2-4" WITH LOCALLY HIGHER AMOUNTS
POSSIBLE. AS A RESULT, INTRODUCED A SLIGHT RISK TO THE EXISTING DAY
4/FRIDAY MARGINAL RISK ERO, COVERING FROM CENTRAL TEXAS TO
SOUTHERN ARKANSAS, WESTERN MISSISSIPPI, AND NORTHERN LOUISIANA.
MACHINE LEARNING ERO GUIDANCE HINTED AT THE POTENTIAL FOR A FUTURE
EASTWARD EXPANSION OF THE SLIGHT RISK WHICH WILL BE MONITORED.
THE RISK FOR HEAVY RAINFALL SHIFTS EASTWARD INTO THE SOUTHEAST ON
SATURDAY AS A FRONTAL WAVE FUELED BY STILL IMPRESSIVE MOISTURE AND
FORCING TRACKS TOWARDS THE MID-ATLANTIC COAST. DESPITE THIS REGION
CURRENTLY BEING AFFECTED BY SIGNIFICANT DROUGHT, CLUSTERS OF
THUNDERSTORMS COULD CONTAIN RAINFALL RATES THAT ARE HEAVY ENOUGH TO
PRODUCE RUNOFF, ESPECIALLY WHEN CONSIDERING GROUNDS AND SOILS THAT
MAY HAVE A DIFFICULT TIME ABSORBING RAIN WITH HEAVY INTENSITY.
THUS, DECIDED TO INTRODUCE A DAY 5/SATURDAY MARGINAL RISK ERO FROM
THE FLORIDA PANHANDLE NORTHEASTWARD TO SOUTHERN NORTH CAROLINA.
THEN LOOKING AHEAD TO SUNDAY THROUGH EARLY NEXT WEEK, THE COLD
FRONT THAT FOLLOWS IN THE WAKE OF THE DEVELOPING COASTAL FRONTAL
WAVE IS LOOKING LIKE IT MAY STALL ACROSS FLORIDA. SHOULD THIS
OCCUR, THE STALLED FRONTAL BOUNDARY WOULD THEN BECOME A FOCUS FOR
ADDITIONAL HEAVY RAIN AND FLOODING THREATS WHICH WILL NEED TO BE
MONITORED AS WE GET CLOSER.
MILLER
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, EXCESSIVE RAINFALL OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY MESSAGES ARE AT:
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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