127
FXUS02 KWBC 070510
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
110 AM EDT THU MAY 7 2026
VALID 12Z SUN MAY 10 2026 - 12Z THU MAY 14 2026
..GENERAL OVERVIEW
AN AMPLIFIED MEAN FLOW PATTERN WILL PERSIST THROUGH MUCH OF THE
PERIOD, TIED TO A CLOSED LOW ANCHORED OVER EASTERN CANADA. THIS
WILL BRING DEEP CYCLONIC FLOW AND SHORTWAVE ENERGIES EJECTING INTO
CENTRAL/EASTERN U.S. THIS PATTERN WILL SUPPORT A SERIES OF FRONTAL
PASSAGES, WHICH WILL BRING SHOWERS AND THUNDERSTORMS ALONG THE
BOUNDARIES. AS THE PRIMARY COLD FRONT MOVES SOUTHEASTWARD, BELOW
NORMAL TEMPERATURES WILL SPREAD INTO EASTERN U.S. THROUGH TUESDAY.
AN STRENGTHENING RIDGE ACROSS THE WESTERN U.S. WILL BRING WELL
ABOVE NORMAL TEMPERATURES THAT WILL GRADUALLY MOVE INTO CENTRAL
U.S. BY MIDWEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODEL GUIDANCE REMAINS WELL CLUSTERED THROUGH MOST OF
THE FORECAST PERIOD IN REGARD TO THE LARGE-SCALE FEATURES OF THE
BROAD TROUGHING ACROSS EASTERN U.S. FROM THE ANCHORED LOW OVER
EASTERN CANADA AND THE RIDGE OVER WESTERN U.S. THERE ARE SOME
SMALLER SCALE DIFFERENCES THAT APPEAR AMONGST THE DETERMINISTIC MODELS
TOWARDS DAY 5. THE GFS SEEMS TO EJECT ADDITIONAL SHORTWAVE TROUGHS
ALONG THE EASTERN U.S. TROUGH COMPARED TO THE ECMWF AND CMC. IN
ADDITION, THE MODELS DIVERGE A BIT FOR THE LOW/TROUGH OVER THE
PACIFIC LATER IN THE PERIOD. SOME OF THESE DIFFERENCES WILL HAVE AN
IMPACT ON SENSIBLE WEATHER AND FRONTAL PLACEMENTS AND PROGRESSION.
THE WPC FORECAST USED A COMPOSITE BLEND OF THE
ECMWF/GFS/CMC/ECAIFS/UKMET THROUGH THE EARLIER PORTION OF THE
PERIOD, WITH GRADUALLY ADDING MORE WEIGHT TOWARD THE ENSEMBLE MEANS
TO COMPENSATE FOR TIMING AND AMPLITUDE DIFFERENCES.
..WEATHER/HAZARDS HIGHLIGHTS
THE CLOSED UPPER-LEVEL LOW OVER EASTERN CANADA WILL CONTINUE TO
SUPPORT A MEAN LONGWAVE TROUGH EXTENDING INTO EASTERN U.S. THROUGH
THE PERIOD. THIS PATTERN WILL BRING A MATURE AND PERSISTENT
CYCLONIC CIRCULATION ALOFT AND MULTIPLE SHORTWAVE ENERGIES EJECTING
ALONG THE BASE OF THE MEAN TROUGH. EACH IMPULSE WILL SUPPORT THE
PROGRESSION OF A STRONG COLD FRONT THAT WILL SWEEP THROUGH THE
EASTERN HALF OF THE COUNTRY EARLY IN THE PERIOD. THE FRONTAL
PASSAGE WILL BRING WIDESPREAD SHOWERS AND THUNDERSTORMS ACROSS
PORTIONS OF THE GREAT LAKES, LOWER MISSISSIPPI VALLEY/SOUTHERN
PLAINS, OHIO VALLEY INTO THE NORTHWEST AND MID- ATLANTIC, WITH
LOCALLY HEAVY RAINFALL POSSIBLE ALONG THE BOUNDARY THROUGH MONDAY.
ACROSS THE SOUTHERN TIER, THE PRIMARY HEAVY RAINFALL THREAT IS
EXPECTED TO FOCUS NEAR THE QUASI-STATIONARY FRONTAL BOUNDARY
EXTENDING FROM EASTERN TEXAS THROUGH THE GULF COAST REGION ON
SUNDAY. DEEP- LAYER GULF MOISTURE TRANSPORT AND WEAK IMPULSES
MOVING THROUGH THE SOUTHERN STREAM WILL SUPPORT REPEATED
CONVECTIVE REDEVELOPMENT ALONG THE BOUNDARY. WITH FLOODING CONCERNS
OVER THE AREA, A MARGINAL RISK HAS BEEN CONTINUED FOR DAY 4/SUNDAY
ERO ACROSS PARTS OF THE SOUTHEAST. ON MONDAY, THE BOUNDARY WEAKENS
AS THE PRIMARY COLD FRONT MOVES INTO THE AREA.
AS THE PRIMARY COLD FRONT MOVES CLOSER TO THE EAST COAST, MUCH OF
THE PLAINS AND MISSISSIPPI VALLEY WILL SEE A SHORT- LIVED DRYING
TREND BY MONDAY WITH THE FRONT CLEARING THE EAST COAST BY TUESDAY.
FARTHER WEST, ANOTHER FRONTAL BOUNDARY BEGINS TO FORM OVER THE
NORTHERN TIER AS A POTENTIAL CLIPPER SYSTEM, BRINGING CHANCES FOR
SHOWERS AND THUNDERSTORMS ACROSS THE NORTHERN PLAINS INTO THE UPPER
MIDWEST, AND EVENTUALLY THE GREAT LAKES AND NORTHEAST. IN
ADDITION, DEEP BOUNDARY LAYER MIXING MAY BRING SOMEWHAT GUSTY WINDS
ACROSS THE ROCKIES AND PLAINS THROUGH THE PERIOD.
TEMPERATURES WILL CONTINUE TO TREND BELOW AVERAGE ACROSS EASTERN
U.S., AS THE PRIMARY COLD FRONT PUSHES SOUTHEASTWARD THROUGH
MONDAY. ACROSS WESTERN U.S., A RIDGING PATTERN WILL BRING WELL
ABOVE HIGHS THROUGH MIDWEEK, AND WILL PUSH EASTWARD INTO CENTRAL
U.S. BY TUESDAY. RECORD TYING/BREAKING HIGHS WILL EXPAND FROM
CALIFORNIA INTO SOUTHERN PLAINS ON TUESDAY. IN ADDITION, SOME OF
THE HIGH TEMPERATURES ACROSS PORTIONS OF CENTRAL CALIFORNIA VALLEYS
AND DESERT SOUTHWEST WILL REACH MODERATE TO MAJOR HEATRISK LEVELS
BY MONDAY INTO TUESDAY.
OUDIT
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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