281
FXUS02 KWBC 071901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
301 PM 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. TO 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. A STRENGTHENING
RIDGE ACROSS THE WESTERN U.S. WILL BRING WELL ABOVE NORMAL
TEMPERATURES THAT WILL GRADUALLY MOVE INTO THE CENTRAL U.S. BY
MIDWEEK. ADDITIONAL TROUGHING, WITH MUCH MORE UNCERTAINTY, MAY MOVE
INTO THE WEST BY THE END OF THE PERIOD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST GUIDANCE SHOWS GOOD AGREEMENT ON THE LARGE SCALE FOR
THE FIRST HALF OF THE PERIOD WHICH MAINLY FEATURES A BUILDING RIDGE
OVER THE WEST, TROUGHING OVER THE EAST, AND A SHORTWAVE DROPPING
FROM THE NORTHERN PLAINS INTO THE GREAT LAKES TO REINFORCE THE
TROUGH IN THE EAST. THE GREATEST SOURCE OF UNCERTAINTY SURROUNDS
THE EVOLUTION AND TIMING OF A SHORTWAVE THAT DROPS SOUTH AND
EASTWARD FROM NEAR ALASKA INTO THE NORTHEAST PACIFIC AND POSSIBLY
EVENTUALLY THE WEST. SOME OF THE 00Z GUIDANCE SEEMED TO SUGGEST A
POSSIBLE TREND TOWARDS THIS SYSTEM MOVING INTO THE WEST LATE
PERIOD, RATHER THAN A CUT-OFF LOW WELL OFF THE COAST LIKE WAS THE
CONSENSUS YESTERDAY. BUT THE TIMING OF THIS SOLUTION IS HIGHLY
UNCERTAIN, WITH THE ECMWF FAST, AND THE CMC/EC-AIFS SLOWER. THE GFS
AND GEFS MEMBERS CONTINUE TO KEEP THIS SYSTEM WELL OFFSHORE, WITH
LESS BREAKDOWN OF THE RIDGE OVER THE WEST. THE NEW 12Z GUIDANCE
THIS AFTERNOON DO NOT PROVIDE ANY ADDITIONAL CLARITY, AND GENERALLY
LOOK SIMILAR TO THE 00Z RUNS. THERE DOES SEEM TO BE SOMEWHAT OF A
SUGGESTION THAT MORE TROUGHING WILL COME INTO THE WEST LATE PERIOD
THAN SUGGESTED BY THE PREVIOUS FORECASTS, SO THE WPC SURFACE PROGS
AND SENSIBLE WEATHER GRIDS TRIED TO TREND IN THAT DIRECTION SHOWING
MORE OF A RIDGE BREAKDOWN THAN THE PREVIOUS SHIFT. THE WPC
FORECAST TODAY WAS WEIGHTED MORE TOWARDS THE MIDDLE GROUND CMC AND
EC-AIFS SOLUTIONS, ALONG WITH THE ENSEMBLE MEANS. ALSO INTRODUCED
ADDITIONAL, ALBEIT LIGHT, QPF ACROSS THE WEST FOR THE WEDNESDAY AND
THURSDAY TIME PERIOD COMPARED TO WHAT THE 13Z NBM INITIALLY
OFFERED.
..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
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 NORTHEAST 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 CONTINUES FOR THE 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. THE LATE PERIOD
POSSIBLE TROUGH INTO THE WEST MAY SPREAD SOME GENERALLY LIGHT AND
TERRAIN INDUCED PRECIPITATION MID WEEK NEXT WEEK AS WELL.
TEMPERATURES WILL CONTINUE TO TREND BELOW AVERAGE ACROSS THE
EASTERN U.S., 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 BY MONDAY INTO 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.
SANTORELLI/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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