939
FXUS02 KWBC 060459
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1259 AM EDT WED MAY 6 2026
VALID 12Z SAT MAY 09 2026 - 12Z WED MAY 13 2026
..GENERAL OVERVIEW
THE DEEP CYCLONIC FLOW REGIME TIED TO A CLOSED LOW OVER EASTERN
CANADA WILL FACILITATE A CONTINUATION OF UNSETTLED CONDITIONS. THE
SYSTEM WILL EJECT SHORTWAVE ENERGIES ACROSS CENTRAL/EASTERN U.S.,
SUPPORTING A SERIES OF FRONTAL PASSAGES, WHICH WILL BRING SHOWERS
AND THUNDERSTORMS ALONG THE BOUNDARIES. THE REMNANTS OF A PRIOR
FRONT WILL LINGER ACROSS THE LOWER MISSISSIPPI VALLEY INTO THE
SOUTHEAST, BRINGING ADDITIONAL RAINFALL TO THE AREA. BELOW NORMAL
TEMPERATURES WILL CONTINUE ACROSS THE GREAT LAKES INTO THE
NORTHEAST THROUGH THE WEEKEND INTO EARLY NEXT WEEK, WHILE A WARMING
TREND CONTINUES TO PUSH EASTWARD ACROSS MUCH OF THE WESTERN U.S.
AND EVENTUALLY CENTRAL U.S. BY EARLY NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE DETERMINISTIC MODELS REMAINS IN DECENT AGREEMENT FOR THE
LARGE-SCALE FEATURES OF THE RIDGE MOVING INTO WESTERN U.S. AND THE
BROAD TROUGHING OVER EASTERN U.S. THERE SEEMS TO BE SOME
DIFFERENCES AMONGST THE MODELS EARLY IN THE PERIOD OF A SHORTWAVE
TROUGH THAT MOVES THROUGH THE SOUTHWEST WITH THE CMC SHOWING A
FASTER PROGRESSION COMPARED TO ECMWF AND GFS. ON DAY 5, MODEL
SPREAD INCREASES FOR THE TIMING AND AMPLITUDE OF THE EMBEDDED
SHORTWAVES WITHIN THE EASTERN TROUGH AND THE EVOLUTION AND INLAND
PROGRESSION OF THE RIDGE OVER THE WEST. THESE DIFFERENCES WILL
CREATE SOME UNCERTAINTY FOR FRONTAL BOUNDARY PLACEMENT AND
SENSIBLE WEATHER. THE MULTI-MODEL BLEND WEIGHTED TOWARD ENSEMBLE
MEANS PROVIDES A STABLE SOLUTION FOR THE VARIABILITY WITHIN THE
DETERMINISTIC MODELS. THEREFORE, THE FORECAST CONSISTED OF A EVEN
MODEL BLEND OF THE CMC/GFS/ECMWF/ECAIFS, WITH LESS WEIGHT ON UKMET
AS TIMING DIFFERENCES WAS MUCH LARGE THAN THE OTHER MODELS. LATER
IN THE PERIOD, THE ENSEMBLE MEANS WERE PHASED IN TO COMPENSATE FOR
THE TIMING, AMPLITUDE, AND EVOLUTION DIFFERENCES.
..WEATHER/HAZARDS HIGHLIGHTS
THE CLOSED UPPER-LEVEL LOW OVER EASTERN CANADA WILL CONTINUE TO
BRING CYCLONIC FLOW AND MULTIPLE SHORTWAVE ENERGIES NEAR THE BASE
OF THE MEAN TROUGH. THIS WILL FACILITATE 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. IN ADDITION, THE
SOUTHERN EXTEND OF A PREVIOUS FRONT WILL CONTINUE TO STALL ACROSS
THE GULF COAST REGION, WHERE PERSISTENT MOISTURE POOLING AND WEAK
IMPULSES EMBEDDED IN THE SUBTROPICAL FLOW COULD SUPPORT OCCASIONAL
CONVECTION AND HEAVY RAINFALL ALONG THE SOUTHEAST THROUGH SUNDAY.
WITH FLOODING CONCERNS OVER THE AREA, A MARGINAL RISK HAVE BEEN
INTRODUCED FOR DAY 4/SATURDAY ERO ACROSS SOUTHEASTERN TEXAS,
LOUISIANA, AND MISSISSIPPI AND DAY 5/SUNDAY ERO ACROSS PARTS OF
ALABAMA, GEORGIA, AND TENNESSEE. AS 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.
OVER THE WESTERN/CENTRAL U.S., A SHORTWAVE ENERGY WILL PUSH A
FRONTAL BOUNDARY OVER PARTS OF THE NORTHERN-CENTRAL ROCKIES/PLAINS,
WHICH WILL BRING A CHANCE FOR LOW- ELEVATION SHOWERS AND
THUNDERSTORMS. WITH TEMPERATURES DROPPING TO FROST/FREEZE CRITERIA
DURING THE OVERNIGHT HOURS, THERE IS A CHANCE FOR HIGH- ELEVATION
SNOW ACROSS THE ROCKIES ON SATURDAY. IN ADDITION, DEEP BOUNDARY
LAYER MIXING WILL BRING GUSTY WINDS ACROSS THE AREA THROUGH THE
WEEKEND. ON MONDAY, 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 UPPER
MIDWEST. FURTHERMORE, WRAPAROUND MOISTURE AND EMBEDDED SHORTWAVES
WILL BRING CHANCES FOR SOME SCATTERED SHOWERS ACROSS THE GREAT
LAKES INTO THE NORTHEAST THROUGH THE PERIOD.
AS THE COLD FRONT OVER THE NORTHERN TIER MOVES SOUTHEASTWARD, IT
WILL USHER A RETURN OF ANOMALOUS BELOW- AVERAGE TEMPERATURES ACROSS
NORTHEASTERN U.S. AND MODERATE TEMPERATURES ACROSS CENTRAL U.S. BY
SUNDAY. A RIDGING PATTERN WILL CONTINUE TO MOVE FURTHER INLAND
OVER THE WESTERN U.S. EARLY IN THE PERIOD, BRINGING INCREASINGLY
WELL ABOVE AVERAGE HIGHS THROUGH EARLY NEXT WEEK. SOME RECORD-
TYING/BREAKING HIGHS WILL BE POSSIBLE AS HEAT REACHES POTENTIALLY
HAZARDOUS LEVELS ACROSS PORTIONS OF THE CENTRAL CALIFORNIA VALLEYS
AND THE DESERT SOUTHWEST BY MONDAY INTO TUESDAY. WELL ABOVE NORMAL
TEMPERATURES PUSH EASTWARD INTO CENTRAL U.S. BY 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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