199
FXUS02 KWBC 082000
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
400 PM EDT FRI MAY 8 2026
VALID 12Z MON MAY 11 2026 - 12Z FRI MAY 15 2026
..GENERAL OVERVIEW
IT GENERALLY REMAINS THE CASE THAT THE UPPER AIR PATTERN ACROSS
THE MAINLAND U.S. WILL FEATURE A PERSISTENT RIDGE IN THE WEST AS
TRANSIENT SHORTWAVES DIPPING INTO THE NORTHERN TIER STATES TEND TO
AMPLIFY A MEAN TROUGH IN THE EAST THROUGH MUCH OF NEXT WEEK. POST-
FRONTAL RAINFALL WILL LIKELY BE MOVING OFF THE EAST COAST LATER ON
MONDAY FOLLOWED BY SOME POTENTIAL FOR CYCLOGENESIS JUST OFF THE
MID-ATLANTIC COAST LATE NEXT WEEK. MEANWHILE, PERSISTENT WARMTH
SHOULD GRADUALLY MIGRATE EASTWARD INTO THE PLAINS LATE NEXT WEEK
WITH SOMEWHAT UNCERTAIN TIMING ON MID-TO-LATE-WEEK ARRIVAL OF
RAINFALL INTO THE PACIFIC NORTHWEST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
RECENT MODEL GUIDANCE GENERALLY PROVIDES GOOD AGREEMENT ON THE
OVERALL SYNOPTIC PATTERN EVOLUTION FOR THE MAINLAND U.S. THROUGH
DAY 7. THE ECMWF AND CMC HAVE BEEN BRINGING A SHORTWAVE TROUGH
ONSHORE INTO THE PACIFIC NORTHWEST ON DAY 5 WEDNESDAY. IN CONTRAST,
THE GFS HANGS ON TO THE WESTERN U.S. UPPER RIDGE, WHICH IS A
SCENARIO SUPPORTED BY THE ENSEMBLE MEANS FROM THE ECMWF, GEFS, AND
CMC. BY DAYS 6-7, THERE IS INCREASING MODEL AGREEMENT FOR A
SHORTWAVE TIPPING INTO THE GREAT LAKES MIDWEEK TO AMPLIFY THE MEAN
TROUGH, WITH POSSIBLE CYCLOGENESIS JUST OFF THE EAST COAST BY
AROUND FRIDAY OF NEXT WEEK. MEANWHILE, FOR THE WESTERN U.S., THERE
IS GOOD ENSEMBLE MEAN AGREEMENT FOR THE NEXT TROUGH FROM THE
PACIFIC TO APPROACH THE WEST COAST BY AROUND FRIDAY, THOUGH THE
DETERMINISTIC MODEL SOLUTIONS SHOW A GREAT DEAL OF SPREAD.
THE WPC FORECAST CHARTS WERE COMPOSED BASED ON THE CONSENSUS OF 40%
FROM THE 06Z GFS & GEFS, 40% FROM THE 00Z ECMWF & EC MEAN, AND 20%
FROM THE 00Z CMC & CMC MEAN. THIS BLEND PROVIDED SOLUTIONS VERY
COMPATIBLE WITH THE PREVIOUS FORECAST PACKAGE.
..WEATHER/HAZARDS HIGHLIGHTS
THE CLOSED UPPER-LEVEL LOW OVER EASTERN CANADA WILL CONTINUE TO
SUPPORT A MEAN LONGWAVE TROUGH EXTENDING INTO THE EASTERN U.S.
THROUGH THE PERIOD. THIS PATTERN WILL BRING A MATURE AND PERSISTENT
CYCLONIC CIRCULATION ALOFT AND MULTIPLE SHORTWAVE ENERGIES TO
APPROACH THE BASE OF THE MEAN TROUGH FROM UPSTREAM. EACH IMPULSE
WILL SUPPORT THE PROGRESSION OF A WAVY COLD FRONT THAT SWEEPS
THROUGH THE EASTERN HALF OF THE COUNTRY EARLY NEXT WEEK, LEADING
INTO THE POSSIBILITY OF COASTAL CYCLOGENESIS. THE FRONTAL PASSAGE
WILL BRING WIDESPREAD SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF
THE GREAT LAKES, LOWER MISSISSIPPI VALLEY/SOUTHERN PLAINS, OHIO
VALLEY INTO THE NORTHEAST AND MID-ATLANTIC, WITH LOCALLY HEAVY
RAINFALL POSSIBLE ALONG THE BOUNDARY AND UP THE CAROLINA COAST ON
MONDAY.
AS THE PRIMARY COLD FRONT MOVES TOWARD 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. SYSTEM
PROGRESSION TO THE WESTERN ATLANTIC MAY ALSO SUPPORT COASTAL
CYCLOGENESIS AND INLAND WRAPPING RAINS AND UNSETTLED WEATHER
WEDNESDAY INTO THURSDAY. MEANWHILE, THE POSSIBLE MID-LATER
TROUGH/SYSTEM EJECTION INTO/ACROSS THE NORTHWEST/WEST MAY SPREAD
SOME GENERALLY LIGHT AND TERRAIN INDUCED PRECIPITATION AS WELL.
TEMPERATURES WILL CONTINUE TO TREND BELOW AVERAGE ACROSS THE
EASTERN U.S. WITH SCATTERED AREAS OF FROST/FREEZE, AS THE PRIMARY
COLD FRONT PUSHES SOUTHEASTWARD THROUGH MONDAY. ACROSS THE WESTERN
U.S., A RIDGING PATTERN WILL BRING WELL ABOVE NORMAL 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. SOME OF THE HIGH TEMPERATURES ACROSS
PORTIONS OF CENTRAL CALIFORNIA VALLEYS AND DESERT SOUTHWEST WILL
REACH MODERATE TO MAJOR HEATRISK LEVELS INTO MONDAY/TUESDAY.
MODERATE TO MAJOR, AND EVEN SPOTTY EXTREME, HEATRISK IS ALSO
POSSIBLE THIS WEEKEND INTO EARLY NEXT WEEK FOR PARTS OF SOUTH
FLORIDA, AND GIVEN CONTINUED DROUGHT AND LOW HUMIDITIES, MAY POSE
AN INCREASED FIRE WEATHER RISK AS WELL.
KONG/SCHICHTEL
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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