248
FXUS02 KWBC 270756
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
356 AM 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 WEEK INTO THE WEEKEND...
..OVERVIEW
AN AMPLIFIED UPPER FLOW PATTERN WILL LEAD TO EPISODES OF ACTIVE
WEATHER ACROSS PARTS OF THE COUNTRY BEGINNING LATER THIS WEEK AND
LASTING THROUGH EARLY NEXT WEEK. A STRENGTHENING LOW PRESSURE
SYSTEM WILL BRING MUCH NEEDED RAIN TO THE NORTHEAST THURSDAY INTO
FRIDAY, WITH COASTAL LOW DEVELOPMENT LEADING TO MULTI-DAY RAINS
INTO NORTHERN NEW ENGLAND THROUGH THE WEEKEND INTO EARLY NEXT WEEK.
MEANWHILE, A SOUTHERN STREAM PACIFIC LOW EJECTING OUT OF THE
SOUTHWEST WILL SET THE STAGE FOR HEAVY RAIN FROM THE SOUTH- CENTRAL
TO SOUTHERN U.S. LATE WEEK INTO THE WEEKEND.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST GUIDANCE CONTINUES TO HAVE A DECENT HANDLE ON THE
INCREASINGLY AMPLIFIED BLOCKING PATTERN THAT IS EXPECTED TO MATURE
LATER THIS WEEK AND PERSIST INTO THE FIRST WEEK OF MAY. THAT BEING
SAID, AS IS TYPICALLY THE CASE WITH BLOCKING PATTERNS, MODELS CAN
SOMETIMES STRUGGLE WITH THE SMALLER SCALE FEATURES AND DETAILS.
CASE IN POINT, THE TIMING OF THE SOUTHERN STREAM PACIFIC LOW
ADVANCING INLAND ACROSS SOUTHERN CALIFORNIA AND THE SOUTHWEST
CONTINUES TO TREND SLOWER, WHICH IS A TREND THAT FIRST STARTED
SEVERAL DAYS AGO. GIVEN THE INFLUENCE OF THIS FEATURE ON THE
POTENTIAL HEAVY RAIN EVENT ACROSS TEXAS LATER THIS WEEK, OPTED TO
DERIVE THE WPC FORECAST USING A COMPOSITE BLEND THAT INITIALLY
LEANED ON THE SLOWER (AND FARTHER SOUTH) SOLUTIONS OF THE ECMWF,
EC-AIFS, AND TO A LESSER EXTENT, THE GFS. BY DAY 6 AND 7, THE BLEND
SHIFTED HIGHER WEIGHTS TOWARDS THE EC AND GEFS ENSEMBLE MEANS,
WHICH OFFERED A COMPROMISE BETWEEN STABILITY AND DETAIL OF FEATURES
ALONG WITH CONTINUITY.
..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 SOUTHEAST 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 THE SOUTHERN HALF
OF MAINE. WHILE THE SIGNAL FOR HEAVY RAIN IS NOTEWORTHY AND COULD
LEAD TO RUNOFF OR LOCALIZED POOR DRAINAGE FLOODING, RECENT MODERATE
TO SEVERE DROUGHT CONDITIONS WILL LIKELY RENDER MOST OF THE RAIN
MORE BENEFICIAL THAN HAZARDOUS. AS A RESULT, NO DAY 4/THURSDAY ERO
WAS HIGHLIGHTED FOR THE TIME BEING. THE COASTAL LOW STALLS OUT
LATER 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 INLAND
ACROSS SOUTHERN CALIFORNIA, THE SOUTHWEST, AND THE FOUR CORNERS
STATES THURSDAY INTO FRIDAY, SPREADING LIGHT TO MODERATE LOW
ELEVATION RAIN AND HIGHER ELEVATION MOUNTAIN SNOW INTO THE REGION.
AS THIS FEATURE EJECTS EASTWARD INTO THE SOUTHERN PLAINS, IT WILL
BEGIN TO INTERACT WITH A NEARLY STATIONARY BOUNDARY DRAPED ROUGHLY
ALONG I-20 IN TEXAS. 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 CENTRAL AND SOUTHERN
TEXAS. DESPITE QUESTIONS WITH RESPECT TO THE QUALITY OF INSTABILITY
(PARTICULARLY NORTH OF I-20) AND THE ONGOING DROUGHT CONDITIONS
OVER PARTS OF THE REGION, THE HEAVY RAIN SIGNAL IS CONCERNING. FOR
THE DAY 4/THURSDAY ERO, THE EXISTING MARGINAL RISK WAS EXPANDED
SOUTHWARD IN AN EFFORT TO CAPTURE THE CURRENT FORECAST QPF MAX
WHILE ALSO ACCOUNTING FOR THE BETTER INSTABILITY SOUTH OF I-20 (AND
ESPECIALLY ALONG AND SOUTH OF I-10). AN UPGRADE TO A SLIGHT RISK
WAS CONSIDERED, BUT OPTED TO HOLD OFF FOR NOW GIVEN UNCERTAINTY
WITH MESOSCALE DETAILS. AFTER THURSDAY, WAVES ALONG THE FRONTAL
ZONE WILL EXPAND THE RAINFALL FOOTPRINT EASTWARD OVER THE MID-SOUTH
AND SOUTHEAST FRIDAY INTO THE WEEKEND, WITH ADDITIONAL RISKS OF
HEAVY RAIN AND POTENTIAL FLOODING. AS A RESULT, A DAY 5/FRIDAY ERO
WAS INTRODUCED FOR MOST OF EASTERN TEXAS, SOUTHERN ARKANSAS, THE
NORTHERN HALF OF LOUISIANA, AND SOUTHWESTERN MISSISSIPPI.
ADDITIONAL UPGRADES AND EXPANSIONS FARTHER EAST ARE POSSIBLE 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 COUNTRY MOUNTAIN SNOW.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page