935
FXUS02 KWBC 101800
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EDT SUN MAY 10 2026
VALID 12Z WED MAY 13 2026 - 12Z SUN MAY 17 2026
..GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE REMAINS REASONABLY CLUSTERED WITH THE OVERALL LARGER
SCALE UPPER PATTERN FROM MID-LATE WEEK INTO THE WEEKEND,
HIGHLIGHTED BY A WESTERN U.S. RIDGE THAT SLIDES EASTWARD INTO THE
CENTRAL U.S., TROUGHING OVER THE EAST, AND SHORTWAVES DROPPING FROM
THE NORTHERN PLAINS/GREAT LAKES TO REINFORCE EAST TROUGHING. THE
GREATEST SOURCE OF UNCERTAINTY CONTINUES TO SURROUND THE SMALLER
SCALE DETAILS REGARDING THE UPSTREAM EVOLUTION AND TIMING OF A MAIN
CLOSED LOW FROM THE EASTERN PACIFIC THAT SHOULD ADVANCE INLAND
OVER THE WEST AND THEN DOWNSTREAM LATER ON IN THE PERIOD. MODELS
CONTINUE TO STRUGGLE WITH THIS FEATURE, WITH POOR AGREEMENT BOTH
RUN-TO-RUN AND WITHIN THE LARGER MODELING SUITE AS A WHOLE. THERE
WAS ENOUGH AGREEMENT TO UTILIZE A COMPOSITE BLEND OF DETERMINISTIC
GUIDANCE FROM THE EC, GFS, UKMET, AND EC-AIFS FOR DAYS 3 AND 4.
HOWEVER, WEIGHTING SHIFTED DRAMATICALLY TOWARDS THE ENSEMBLE MEANS
FOR THE REST OF THE PERIOD, WITH 100% OF THE BLEND SPLIT BETWEEN
THE EC AND GEFS ENSEMBLE MEANS BY DAY 7. THIS STRATEGY SEEMED TO
BEST PRESERVE CONTINUITY WHILE MAINTAINING INTEGRITY WITH THE 13Z
NATIONAL BLEND OF MODELS.
..WEATHER/HAZARDS HIGHLIGHTS
AN EASTERN CANADIAN CLOSED UPPER-LEVEL LOW WILL CONTINUE TO HELP
SUPPORT A MEAN LONGWAVE TROUGH DOWN INTO THE EASTERN U.S. THROUGH
MID TO LATE WEEK. THIS PATTERN WILL SUPPORT A PERSISTENT CYCLONIC
CIRCULATION ALOFT, ALLOWING MULTIPLE SHORTWAVE ENERGIES TO APPROACH
THE BASE OF THE MEAN TROUGH FROM UPSTREAM. IMPULSES WILL LEAD TO
THE PROGRESSION OF WAVY FRONTAL SYSTEMS TO BRING PERIODS OF
SHOWERS/THUNDERSTORMS THROUGH THE EASTERN THIRD OF THE COUNTRY.
SYSTEM PROGRESSION TO THE ATLANTIC WILL ALSO LOOK TO SPAWN MODERATE
COASTAL CYCLOGENESIS WITH WRAPPING MOISTURE/RAINS LIFTING UP/OFF
THE EAST COAST, LENDING INTO A MARITIME THREAT. THE PERSISTENT
TROUGHING LOOKS TO BREAK DOWN HEADING INTO NEXT WEEKEND AS LOW
AMPLITUDE RIDGING BUILDS IN FROM THE WEST.
UPSTREAM, AN EASTERN PACIFIC CLOSED LOW IS SLATED, WITH MUCH
UNCERTAINTY, TO ADVANCE INLAND SOMETIME MID-LATE WEEK TO FOCUS
ORGANIZED LIGHT TO MODERATE PRECIPITATION MOST LIKELY ACROSS
PORTIONS OF THE NORTHERN GREAT BASIN, PACIFIC NORTHWEST, AND
NORTHERN ROCKIES. A DEVELOPING DOWNSTREAM SURFACE LOW AND FRONTAL
BOUNDARY WILL FORM DOWN FROM THE NORTHERN TIER, BRINGING CHANCES
FOR SHOWERS AND THUNDERSTORMS FROM THE NORTH-CENTRAL U.S. TO THE
GREAT LAKES/EAST. FARTHER UPSTREAM SYSTEM ENERGIES WILL
SUBSEQUENTLY WORK INLAND INTO THE WEST AND DOWNSTREAM OVER THE
LOWER 48 WITH UNCERTAIN TIMING AND WEATHER FOCUS IN INCREASINGLY
ZONAL FLOW ALOFT.
TEMPERATURES FOR THE EASTERN THIRD OF THE U.S. WILL BE NEAR TO
BELOW NORMAL INTO MID-LATE WEEK BEFORE MODERATING INTO NEXT WEEKEND
WITH MAIN UPPER TROUGH EJECTION INTO THE ATLANTIC. MEANWHILE, A
SLOWLY EASTWARD SHIFTING UPPER RIDGE WILL GRADUALLY SPREAD WELL
ABOVE NORMAL TEMPERATURES FROM THE WEST TO THE ROCKIES AND CENTRAL
U.S. THAT MAY PRODUCE SEVERAL HIGH TEMPERATURE RECORDS.
SCHICHTEL/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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