545
FXUS02 KWBC 061816
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
216 PM 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 FOR
THE EAST. THE SYSTEM WILL EJECT SHORTWAVE ENERGIES ACROSS THE
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, WITH INSTABILITY AND
ANOMALOUS MOISTURE SUPPORTING MODERATE TO HEAVY RAINFALL SATURDAY
INTO SUNDAY. 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 BUILD ACROSS MUCH OF THE
WESTERN U.S. AND EVENTUALLY CENTRAL U.S. BY EARLY NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODEL GUIDANCE FOR TODAY REMAINS IN DECENT AGREEMENT
FOR THE LARGE-SCALE FORECAST OVER THE CONUS DURING THE PERIOD, WITH
SOME NOTABLE DIFFERENCES IN THE DETAILS OF SMALLER SYSTEMS MOVING
THROUGH THE FLOW. THERE ARE A FEW MINOR DIFFERENCES WITH SYSTEMS AS
THEY RELOAD INTO THE TROUGH OVER THE EAST, BUT A GENERAL MODEL
COMPROMISE SEEMED TO SERVE AS A GOOD STARTING POINT. AFTER THIS,
THERE ARE SOME DIFFERENCES WITH A SHORTWAVE RIDING THE TOP OF THE
WESTERN U.S. RIDGE MID-PERIOD, WITH THE ECMWF NOTABLY STRONGER WITH
THIS SYSTEM (AND THE RESULTING QPF). LATE IN THE PERIOD, THERE IS
SOME UNCERTAINTY WITH THE PLACEMENT AND STRUCTURE OF THE WESTERN
U.S. RIDGE, OWING TO GREATER DIFFERENCES IN AN UPPER LOW LOCATED
WELL OFF THE WEST COAST. THE WPC FORECAST TRENDED MORE TOWARDS THE
ENSEMBLE MEANS FOR THE LATTER HALF OF THE FORECAST PERIOD, WITH
ALSO MAINTAINED GOOD AGREEMENT WITH THE PREVIOUS WPC FORECAST. FOR
THE MOST PART, THE NBM SERVED AS A DECENT STARTING POINT FOR THE
SENSIBLE WEATHER GRIDS, WITH ONLY MINOR EDITS NEEDED.
..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 HAS BEEN
MAINTAINED FOR DAY 4/SATURDAY ERO ACROSS ACROSS THE LOWER
MISSISSIPPI VALLEY INTO THE DEEP SOUTH, AND DAY 5/SUNDAY ERO FOR
PARTS OF THE SOUTHEAST. 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.
OVER THE WESTERN/CENTRAL U.S., 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 DURING THE OVERNIGHT
HOURS, THERE IS A CHANCE FOR HIGH- ELEVATION SNOW ACROSS THE
ROCKIES ON SATURDAY. IN ADDITION, DEEP BOUNDARY LAYER MIXING MAY
BRING SOMEWHAT 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 THE UPPER
MIDWEST, AND EVENTUALLY THE GREAT LAKES AND NORTHEAST.
AS THE COLD FRONT OVER THE NORTHERN TIER MOVES SOUTHEASTWARD, IT
WILL USHER A RETURN OF BELOW- AVERAGE TEMPERATURES ACROSS THE
NORTHEASTERN U.S. WITH MODERATING 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 MODERATE TO
MAJOR HEATRISK LEVELS ACROSS PORTIONS OF THE CENTRAL CALIFORNIA
VALLEYS AND THE DESERT SOUTHWEST BY MONDAY INTO TUESDAY. WELL ABOVE
NORMAL TEMPERATURES PUSH EASTWARD INTO THE CENTRAL U.S. BY
TUESDAY.
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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