251
FXUS02 KWBC 271955
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
355 PM EDT MON APR 27 2026
VALID 12Z THU APR 30 2026 - 12Z MON MAY 04 2026
...HEAVY RAIN AND FLOODING THREAT INCREASING ACROSS THE SOUTH-
CENTRAL U.S. LATE THIS WEEK...
..OVERVIEW
AN AMPLIFIED UPPER LEVEL PATTERN WILL PERSIST THROUGH THE PERIOD,
WITH MEAN RIDGING OVER THE EASTERN PACIFIC AND MEAN TROUGHING OVER
THE EASTERN UNITED STATES. THIS PATTERN WILL RESULT IN ACTIVE
WEATHER FOR THE SOUTH-CENTRAL U.S. AND EAST COAST, WITH INCREASING
POTENTIAL FOR HEAVY RAIN AND FLOODING LATE THIS WEEK OVER THE
SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY. A COASTAL LOW MAY
ALSO BRING LOCALLY HEAVY RAINFALL AND ISOLATED FLOODING CONCERNS TO
THE NORTHEAST ON THURSDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE REMAINS IN GOOD AGREEMENT ON THE PATTERN THROUGH THE
PERIOD AS AN INCREASINGLY AMPLIFIED AND BLOCKY PATTERN DEVELOPS
ACROSS THE NATION. AN UPPER LEVEL LOW WILL MOVE INTO THE SOUTHWEST
LATE THIS WEEK AND TRIGGER HEAVY RAINFALL ACROSS THE SOUTH-CENTRAL
UNITED STATES. MOST OF THE DETERMINISTIC, ENSEMBLE, AND AI GUIDANCE
HAS COME TO A CONSENSUS ON THE TIMING OF THIS FEATURE, BUT THE
ECMWF SEEMS TO BE MUCH SLOWER THAN ALL OTHER GUIDANCE. THE SPREAD
IN GUIDANCE HAS RESULTED IN A BROAD PRECIPITATION FIELD IN THE
NATIONAL BLEND THAT ACCOUNTS FOR THE SLOWER AND FASTER
POSSIBILITIES.
ANOTHER UPPER LOW IS EXPECTED TO MOVE SOUTH JUST OFFSHORE OF THE
WEST COAST EARLY NEXT WEEK, AND THERE IS QUITE A BIT OF UNCERTAINTY
WITH THE POSITION OF THIS FEATURE. THE ECMWF AND CMC ARE ON THE
WESTERN SIDE OF THE SPREAD WHILE THE GFS AND UKMET ARE ON THE
EASTERN SIDE. AI GUIDANCE SEEMS TO FALL IN BETWEEN, WHICH IS THE
MOST REASONABLE SOLUTION AT THIS POINT. THE EVENTUAL POSITION OF
THIS FEATURE MAY IMPACT WINDS AND PRECIPITATION CHANCES ALONG THE
WEST COAST SUNDAY INTO MONDAY
THE WPC FORECAST WAS COMPOSED OF A NEAR EVEN BLEND OF THE
AVAILABLE DETERMINISTIC GUIDANCE AS A STARTING POINT, WHICH
PRODUCED A REASONABLE MIDDLE OF THE ROAD SOLUTION THROUGH THE END
OF THE WEEK. ENSEMBLE MEANS WERE ADDED TO THE BLEND IN INCREASING
AMOUNTS FOR THE WEEKEND INTO EARLY NEXT WEEK TO HELP SMOOTH OUT
MODEL DIFFERENCES. THIS MAINTAINED CONTINUITY WITH THE NATIONAL
BLEND AND PREVIOUS FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
A FRONTAL SYSTEM ASSOCIATED WITH A DEEPENING TROUGH OVER THE
NORTHEAST WILL BEGIN TO SPREAD MUCH NEEDED RAINFALL INTO THE REGION
ON THURSDAY. THE PRIMARY LOW PRESSURE SYSTEM WILL WEAKEN AS IT
TRACKS INTO SOUTHEASTERN CANADA, BUT SECONDARY COASTAL DEVELOPMENT
OFF THE MID-ATLANTIC WILL TAKE CONTROL SOON AFTER AS IT APPROACHES
SOUTHERN NEW ENGLAND LATER THURSDAY INTO FRIDAY. THE NEWLY FORMED
LOW WILL THEN BEGIN TO DRAW A LONG FETCH OF ANOMALOUS GULF/ATLANTIC
MOISTURE NORTHWARD, SUPPORTING AN AXIS OF HEAVY RAINFALL TOTALING
1-3" ACROSS NORTHERN NEW ENGLAND AND ESPECIALLY FROM EASTERN NEW
HAMPSHIRE INTO THE SOUTHERN HALF OF MAINE. WHILE THE SIGNAL FOR
HEAVY RAIN IS NOTEWORTHY AND COULD LEAD TO RUNOFF AND/OR LOCALIZED
FLOODING, THE MAJORITY OF THE RAINFALL SHOULD BE BENEFICIAL GIVEN
MODERATE TO SEVERE DROUGHT CONDITIONS. AS A RESULT, NO DAY
4/THURSDAY ERO WAS HIGHLIGHTED FOR THE TIME BEING. THE COASTAL LOW
SHOULD STALL OVER THE CANADIAN MARITIMES FRIDAY INTO THE WEEKEND,
ALLOWING INTENSITY TO WANE BUT KEEPING CONDITIONS COOL, WINDY, AND
WET/UNSETTLED THROUGH EARLY NEXT WEEK. A LITTLE SNOW WRAPPING IN ON
THE BACK/COLDER SIDE OF THE STORM CAN'T BE RULED OUT EITHER ACROSS
THE HIGHER ELEVATIONS OF NORTHERN NEW ENGLAND OR THE INTERIOR
NORTHEAST.
MEANWHILE, A SOUTHERN STREAM PACIFIC LOW WILL SLOWLY TRACK INTO THE
SOUTHWEST ON THURSDAY AND INTERACT WITH A FRONTAL BOUNDARY OVER
THE SOUTHERN PLAINS. ANOMALOUS PACIFIC AND GULF MOISTURE
OVERRUNNING THIS FRONTAL BOUNDARY COMBINED WITH IMPRESSIVE DYNAMICS
AND FORCING FROM A STRONG UPPER JET WILL LEAD TO THE INCREASING
POTENTIAL FOR SIGNIFICANT RAINFALL ACROSS THE SOUTHERN PLAINS AND
LOCALLY HEAVY SNOW IN THE SOUTHERN ROCKIES. FOR THE DAY 4/THURSDAY
ERO, THE EXISTING MARGINAL RISK WAS EXPANDED NORTHWESTWARD TO
ACCOUNT FOR INCREASING QPF AMIDST DECENT INSTABILITY. FRIDAY INTO
THE WEEKEND, WAVES ALONG THE FRONTAL ZONE WILL EXPAND THE RAINFALL
FOOTPRINT EASTWARD INTO THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST,
WITH ADDITIONAL RISKS OF HEAVY RAIN AND POTENTIAL FLOODING. THE
DAY 5/FRIDAY ERO FEATURES A MARGINAL RISK AREA FROM TEXAS TO THE
LOWER MISSISSIPPI VALLEY THAT WAS EXPANDED EASTWARD TO ACCOUNT FOR
A SLIGHTLY FASTER PROGRESSION OF THE FRONTAL SYSTEM. THIS RISK AREA
MAY BE EXPANDED FURTHER EAST AND COULD POTENTIALLY BE UPGRADED
WITH FUTURE UPDATES.
ELSEWHERE, ANOTHER PACIFIC CLOSED LOW MAY APPROACH NORTHERN
CALIFORNIA AND THE GREAT BASIN LATER THIS WEEKEND INTO EARLY NEXT
WEEK, BRINGING COOLER AND UNSETTLED WEATHER FEATURING LOW ELEVATION
RAIN AND HIGH ELEVATION MOUNTAIN SNOW.
DOLAN/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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