773
FXUS02 KWBC 010522
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
122 AM EDT FRI MAY 1 2026
VALID 12Z MON MAY 04 2026 - 12Z FRI MAY 08 2026
..OVERVIEW
THE PERSISTENT AMPLIFIED UPPER-LEVEL LOW OVER SOUTHEAST CANADA CONTINUES
TO BRING SHORTWAVE ENERGY ACROSS CENTRAL/EASTERN U.S. INTO NEXT
WEEK. THIS PATTERN WILL BRING MULTIPLE ROUNDS OF PRECIPITATION AND
COOLER THAN NORMAL CONDITIONS ACROSS UPPER MIDWEST, MID- ATLANTIC,
GREAT LAKES, AND NORTHEAST THROUGH MIDWEEK. AS THE FRONT MOVES
SOUTHEASTWARD, SHOWERS AND THUNDERSTORMS ARE EXPECTED TO EXPAND
INTO LOWER MISSISSIPPI VALLEY INTO SOUTHEAST. ANOTHER LOW/TROUGH
OFF THE PACIFIC WILL BRING PRECIPITATION ACROSS PARTS OF THE WEST
EARLY NEXT WEEK. THE RIDGE MOVES INLAND OVER THE WEST BY MIDWEEK,
BRINGING ABOVE SEASONAL TEMPERATURES.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODEL GUIDANCE PROVIDES AN OVERALL DECENT AGREEMENT ON
THE LARGE-SCALE FEATURES, WITH THE DETERMINISTIC MODELS SHOWING
SOME SMALL-SCALE DIFFERENCE WITH TIMING AND STRUCTURE. THE LARGE-
SCALE DIFFERENCES BECOME NOTABLE AROUND DAY 5, WITH THE MOST
DISAGREEMENT ON THE UPPER LOW/TROUGH OVER THE PACIFIC. ALTHOUGH
THE MODELS CONTINUE TO SHOW GOOD AGREEMENT WITH THE UPPER
LOW/TROUGH OVER SOUTHEASTERN CANADA THROUGH THE PERIOD, THE
DETERMINISTIC MODELS CONTINUE TO SHOW DISCREPANCY WITH THE
SHORTWAVE ENERGY EMBEDDED AT THE BASE OF THE LOW. THEREFORE, THE
WPC FORECAST CONSISTED OF A MULTI- MODEL BLEND OF THE
GFS/ECMWF/CMC/UKMET/EC- AIFS FOR THE FIRST HALF OF THE PERIOD. THE
LATER PORTION INCORPORATED THE ENSEMBLE MEANS TO HELP SMOOTH OUT
SOME OF THE AMPLITUDE AND TIMING DIFFERENCES AMONGST THE MODELS.
..WEATHER/HAZARDS HIGHLIGHTS
THE PERSISTENT UPPER-LEVEL TROUGH OVER SOUTHEASTERN CANADA
CONTINUES TO SLOWLY MOVE EASTWARD, EJECTING MULTIPLE EMBEDDED
SHORTWAVE DISTURBANCES THROUGH THE PERIOD. THE TROUGH WILL PUSH A
FEW FRONTAL PASSAGES ACROSS CENTRAL AND EASTERN U.S., WHICH WILL
REINFORCE UNSETTLED WEATHER. BY MONDAY, EXPECT SHOWERS AND
THUNDERSTORMS ACROSS UPPER MIDWEST, OHIO VALLEY, GREAT LAKES AND
NORTHEAST. WITH THE TIGHTENING PRESSURE GRADIENT, GUSTY WINDS MAY
DEVELOP ALONG THE FRONT ACROSS SOUTHERN PLAINS INTO OHIO VALLEY AND
NORTHEAST. AS THE FRONT SLOWLY MOVES SOUTHWARD AND INTERACTS WITH
WARM GULF MOISTURE, SHOWERS AND THUNDERSTORMS WILL DEVELOP OVER
PARTS OF THE MID/LOWER MISSISSIPPI VALLEY, MID- ATLANTIC, AND
SOUTHEAST BY MIDWEEK. WITH THE COMBINATION OF UPPER- LEVEL FORCING
AND ORGANIZED THUNDERSTORMS PRODUCING HEAVY RAINFALL, LOCALIZED
FLOODING MAY BE POSSIBLE ACROSS MID/LOWER MISSISSIPPI VALLEY INTO
OHIO/TENNESSEE VALLEY. THIS FLOOD THREAT IS REPRESENTED BY THE
MARGINAL RISK ON DAY 5/TUESDAY ERO.
ADDITIONALLY, THE COLD FRONT WILL BRING BELOW NORMAL TEMPERATURES
BEHIND THE FRONT, ESPECIALLY OVER PARTS OF NORTHERN/CENTRAL
PLAINS, CALIFORNIA, AND SOUTHWEST, WHERE TEMPERATURES WILL DROP
10-15 DEGREES BELOW AVERAGE THROUGH MIDWEEK. WITH THE COLDER
TEMPERATURES, CHANCES FOR SOME MIXED PRECIPITATION OVER THE
NORTHERN PARTS OF THE UPPER GREAT LAKES/MIDWEST WILL BE POSSIBLE
TUESDAY THROUGH THURSDAY.
OVER THE WESTERN U.S., A UPPER LOW/TROUGH APPROACHING THE COAST
WILL BRING PRECIPITATION OVER THE AREA FOR THE FIRST PORTION OF
NEXT WEEK. WITH SUFFICIENT MOISTURE AND INSTABILITY, EXPECT LOW
ELEVATION SHOWERS AND POSSIBLE THUNDERSTORMS, AS WELL AS SOME HIGH
ELEVATION SNOW ACROSS CALIFORNIA AND GREAT BASIN. A SECONDARY COLD
FRONT WILL DROP INTO THE ROCKIES/PLAINS BY TUESDAY, EXPANDING THE
CHANCE FOR SHOWERS AND THUNDERSTORMS ACROSS THE AREA. EXPECT
FLOODING POTENTIAL TO INCREASE AS TRAINING MAY DEVELOP ALONG THE
SLOW-MOVING FRONT. OVER THE PACIFIC NORTHWEST, POSSIBLE RECORD
BREAKING WARM TEMPERATURES MAY DEVELOP ON TUESDAY AS AN RIDGE
PUSHES INLAND. AS THE RIDGE CONTINUES TO MOVE EASTWARD, ABOVE
NORMAL TEMPERATURES WILL RETURN ACROSS MUCH OF WESTERN U.S. BY
THURSDAY.
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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