012
FXUS02 KWBC 021956
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
356 PM EDT SAT MAY 2 2026
VALID 12Z TUE MAY 5 2026 - 12Z SAT MAY 9 2026
..GENERAL OVERVIEW
A SLIGHTLY BLOCKY UPPER LEVEL PATTERN IS EXPECTED TO BE IN PLACE
FOR THIS FORECAST PERIOD, FEATURING A SOUTHERN STREAM UPPER
TROUGH/CLOSED LOW NEAR THE DESERT SOUTHWEST, A RIDGE AXIS EXTENDING
ACROSS THE PACIFIC NORTHWEST AND NORTHERN ROCKIES, AND BROAD
CYCLONIC FLOW WITH A GENERAL TROUGH OVER THE EASTERN HALF OF THE
COUNTRY. A COLD FRONT WILL CROSS THE EASTERN U.S. AND EXIT THE
COAST THURSDAY NIGHT, WITH MODERATE TO HEAVY RAINFALL AHEAD OF IT
FROM THE LOWER MISSISSIPPI RIVER VALLEY TO THE CENTRAL
APPALACHIANS, AND A RETURN TO COLDER WEATHER BEHIND IT TO CLOSE OUT
THE WORK WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 12Z MODEL GUIDANCE SUITE IS IN GREAT SYNOPTIC SCALE AGREEMENT
ACROSS THE COUNTRY THROUGH THE MIDDLE OF THE WEEK, WITH A GENERAL
DETERMINISTIC MODEL BLEND WORKING WELL FOR FRONTAL PLACEMENTS AND
PRESSURES. THERE IS ALSO DECENT AGREEMENT ON A CORRIDOR OF ENHANCED
QPF FROM THE DEEP SOUTH TO THE OHIO VALLEY AND CENTRAL
APPALACHIANS, BUT DIFFER ON LATITUDINAL PLACEMENT, WITH THE ECMWF
AND AIFS GUIDANCE TO THE SOUTH OF THE GFS/UKMET/NBM.
MODEL GUIDANCE REMAINS IN GOOD AGREEMENT GOING INTO THE
FRIDAY/SATURDAY TIME PERIOD AS WELL, WITH SOME NORMAL MESOSCALE
DIFFERENCES. THE GFS IS A LITTLE TO THE WEST WITH THE UPPER LOW
OVER THE DESERT SOUTHWEST COMPARED TO THE ECMWF/CMC, AND THE CMC IS
MORE BROAD WITH THE UPPER RIDGE OFF THE OREGON/WASHINGTON COAST BY
SATURDAY, BUT IN BOTH INSTANCES THESE MODELS ARE ALL ABLE TO BE
INCORPORATED INTO THE BLEND, WITH THE ENSEMBLE MEANS INCREASED TO
ABOUT 30-40% BY THIS TIME.
..WEATHER/HAZARDS HIGHLIGHTS
THE UPPER-LEVEL LOW WILL CONTINUE TO MEANDER OVER CENTRAL TO
SOUTHEASTERN CANADA THROUGH THE MEDIUM-RANGE PERIOD, BRINGING A
SERIES OF SHORTWAVES ROTATING AROUND THE BASE OF THE MEAN TROUGH.
THIS WILL SUPPORT MULTIPLE FRONTAL PASSAGES AND WAVES OF
PRECIPITATION ACROSS CENTRAL/EASTERN U.S. THE ASSOCIATED COLD AIR
BEHIND THE FRONT AND CYCLONIC FLOW WILL BRING BELOW NORMAL
TEMPERATURES ACROSS THE NORTHERN/CENTRAL PLAINS INTO MUCH OF THE
EASTERN U.S., WITH FROST/FREEZE CONDITIONS FROM THE UPPER MIDWEST
TO THE GREAT LAKES. AHEAD OF THE COLD FRONT, EXPECT SHOWERS AND
THUNDERSTORMS ACROSS UPPER MIDWEST/MISSISSIPPI VALLEY,
OHIO/TENNESSEE VALLEY, GREAT LAKES AND NORTHEAST ON TUESDAY, WITH
GUSTY WINDS ACROSS FROM THE SOUTHERN PLAINS TO THE OHIO VALLEY AND
INTO THE NORTHEAST.
AS THE FRONT SLOWLY MOVES SOUTHWARD AND INTERACTS WITH WARM GULF
MOISTURE, SHOWERS AND THUNDERSTORMS WILL EXPAND INTO THE MID-SOUTH,
MID-ATLANTIC, AND SOUTHEAST BY WEDNESDAY. WITH THE COMBINATION OF
UPPER-LEVEL FORCING AND ORGANIZED THUNDERSTORMS PRODUCING HEAVY
RAINFALL ALONG THE FRONT, LOCALIZED FLOODING MAY BE POSSIBLE ACROSS
THE MID/LOWER MISSISSIPPI VALLEY INTO THE OHIO/TENNESSEE VALLEY
WEDNESDAY INTO THURSDAY. THIS FLOOD THREAT IS REPRESENTED BY THE
MARGINAL RISK ON THE DAY 4/TUESDAY ERO. GOING INTO WEDNESDAY, THE
FRONT SLOWS DOWN SOME, ALLOWING FOR AN INFLUX OF MOISTURE ALONG
THE BOUNDARY OVER THE SOUTHEAST AND THE TENNESSEE VALLEY,
SUPPORTING LOCALLY HEAVY RAINFALL. WITH FLOODING CONCERNS OVER THE
AREA, THE MARGINAL RISK HAS BEEN EXPANDED FOR THE DAY 5/WEDNESDAY
ERO FOR PARTS OF THE OHIO/TENNESSEE VALLEY, LOWER MISSISSIPPI
VALLEY, AND THE SOUTHEAST. THERE IS A GOOD POSSIBILITY THAT A
SLIGHT RISK COULD EVENTUALLY BE NEEDED OVER PORTIONS OF THE OUTLOOK
AREA IN LATER UPDATES.
AS COLD AIR PUSHES INTO THE NORTHERN U.S., THERE IS A SLIGHT
CHANCE FOR SOME MIXED PRECIPITATION OVER SOME ISOLATED HIGHER-
ELEVATION AREAS/NORTHERN AREAS NEAR THE U.S. CANADA BORDER, BUT
IMPACTS WILL BE MINIMAL. IN ADDITION, COLDER AIR BEHIND THE UPPER
LOW EJECTING FROM THE SOUTHWEST U.S. WILL ALSO BRING BELOW NORMAL
TEMPERATURES INTO CALIFORNIA AND THE DESERT SOUTHWEST, WHERE
TEMPERATURES WILL DROP 5-15 DEGREES BELOW AVERAGE INTO MIDWEEK
BEFORE MODERATING LATE IN THE WEEK.
OVER THE WESTERN U.S., THE PACIFIC UPPER LOW/TROUGH WILL MOVE INTO
THE SOUTHWEST EARLY IN THE PERIOD, THEN GRADUALLY EJECTS INTO THE
PLAINS BY LATE WEEK. THIS WILL BRING SUFFICIENT MOISTURE AND
INSTABILITY TO SUPPORT WIDESPREAD LOW ELEVATION SHOWERS AND
POSSIBLE THUNDERSTORMS, AS WELL AS SOME HIGH ELEVATION SNOW ACROSS
PARTS OF CALIFORNIA AND GREAT BASIN. THE COLD FRONT ASSOCIATED
WITH THE LEADING EDGE OF THE COLD AIR INTRUSION INTO THE HIGH
PLAINS WILL DROP INTO THE ROCKIES/PLAINS ON TUESDAY, EXPANDING THE
CHANCE FOR SHOWERS AND THUNDERSTORMS, WITH A COLD RAIN FOR THE
FRONT RANGE OF COLORADO TO SOUTHERN WYOMING THROUGH WEDNESDAY AND
HEAVY SNOW FOR THE COLORADO ROCKIES. OVER THE PACIFIC NORTHWEST, A
RIDGE WILL PUSH INLAND, BRINGING A WARMING TREND. AS THE RIDGE
CONTINUES TO MOVE EASTWARD, ABOVE NORMAL TEMPERATURES WILL RETURN
ACROSS MUCH OF WESTERN U.S. LATER NEXT WEEK.
OUDIT/HAMRICK
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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