387
FXUS02 KWBC 121958
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
358 PM EDT TUE MAY 12 2026
VALID 12Z FRI MAY 15 2026 - 12Z TUE MAY 19 2026
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS ARE IN REASONABLY GOOD AGREEMENT REGARDING THE EVOLUTION OF
THE OVERALL SYNOPTIC PATTERN ACROSS THE LOWER 48 DURING THE MEDIUM
RANGE PERIOD. A STRONG CLOSED LOW OVER THE EASTERN U.S. WITH ZONAL
FLOW UPSTREAM ACROSS THE REST OF THE CONUS WILL GIVE WAY TO A MORE
AMPLIFIED PATTERN THROUGH EARLY NEXT WEEK.
A SHORTWAVE EMANATING FROM THE GULF OF ALASKA WILL DIG DOWN INTO
THE WEST THIS WEEKEND. A DOWNSTREAM RIDGE DEVELOPS OVER THE EASTERN
U.S. IN RESPONSE TO THIS. A GENERAL MODEL BLEND CONSISTING OF THE
AVAILABLE DETERMINISTIC AND AI GUIDANCE WERE SUFFICIENT IN
CAPTURING MUCH OF THIS EVOLUTION. WHERE THINGS BEGAN TO DIVERGE,
IS AROUND POTENTIAL SPLIT FLOW DEVELOPMENT OVER THE WEST EARLY NEXT
WEEK. THE CANADIAN SUITE WAS THE ONLY GUIDANCE THAT SUGGESTED THIS
SCENARIO, SO IT WAS SIMPLY NOT INCLUDED IN THE BLEND. THE EURO
SUITE IS FAVORED BEYOND DAY 5 WITH THE USUAL INCREASE IN ENSEMBLE
MEAN WEIGHTING IN THE BLEND.
..WEATHER/HAZARDS HIGHLIGHTS
AMPLIFIED UPPER TROUGHING WILL PERSIST OVER THE EAST INTO FRIDAY.
SYSTEM PROGRESSION TO THE ATLANTIC WILL SPAWN MODERATE COASTAL
CYCLOGENESIS WITH MODERATE WRAPPING MOISTURE/RAINS/WINDS LIFTING
INTO NEW ENGLAND WHILE ACTING AS A MARITIME THREAT.
UPSTREAM GUIDANCE FINALLY AGREES TO PROGRESS A CURRENT MAIN EASTERN
PACIFIC UPPER LEVEL CLOSED LOW/TROUGH BODILY INLAND TO THE NORTH-
CENTRAL U.S./SOUTH-CENTRAL CANADA BY FRIDAY TO SPAWN SURFACE
CYCLOGENESIS AND FOCUS LIGHT-MODERATE MIDWEST/GREAT LAKES TRAILING
FRONTAL QPF. ACTIVITY DIMINISHES WITH WEEKEND DOWNSTREAM SYSTEM
PROGRESSION OVER EASTERN CANADA AND THE NORTHEAST.
FARTHER UPSTREAM SYSTEM ENERGIES SUBSEQUENTLY WORK INTO THE WEST
AND DOWNSTREAM UP ACROSS THE CENTRAL U.S. WITH LESS CERTAINTY THIS
WEEKEND INTO EARLY NEXT WEEK. HOWEVER, THERE IS AM EMERGING SIGNAL
THAT WEEKEND UPPER TROUGH PASSAGE OVER THE WEST WILL FOCUS SOME
ORGANIZED PRECIPITATION CHANCES BROADLY OVER THE NORTHWEST AND
NORTH-CENTRAL INTERMOUNTAIN WEST/ROCKIES. WAVY DOWNSTREAM FRONTAL
GENESIS AND LEAD GULF RETURN FLOW OF MOISTURE AND INSTABILITY MAY
SET THE STAGE TO FUEL AN EMERGING LATER WEEKEND/EARLY NEXT WEEK
ENHANCED CENTRAL U.S. CONVECTIVE RAINFALL PATTERN TO MONITOR.
MEANWHILE, AN EASTWARD SPREADING UPPER RIDGE WILL SPREAD WELL
ABOVE NORMAL PRE-FRONTAL TEMPERATURES ACROSS THE CENTRAL TO EASTERN
U.S. THIS PERIOD THAT MAY SUPPORT LOCAL HIGH TEMPERATURE VALUES.
TO THE SOUTH, LOW LEVEL ONSHORE FLOW WILL BRING SHOWER INTO FLORIDA
IN PROXIMITY TO UPPER LOW DEVELOPMENT NEAR/EAST OF THE BAHAMAS.
KEBEDE/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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