532
FXUS02 KWBC 250653
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
253 AM EDT SUN MAY 25 2025
VALID 12Z WED MAY 28 2025 - 12Z SUN JUN 01 2025
..OVERVIEW
THIS MEDIUM RANGE PERIOD BEGINS MIDWEEK WITH A SLOW TO PROGRESS
UPPER LEVEL PATTERN LINGERING OVER THE LOWER 48, WITH SPLIT FLOW TO
INCLUDE A COUPLE OF EMBEDDED CUTOFF LOWS. A NORTHERN STREAM LOW
WILL MEANDER OVER THE NORTH-CENTRAL U.S. AND MIDWEST THIS WEEK
WHILE AN OFFSHORE SOUTHERN STREAM LOW WILL ONLY GRADUALLY APPROACH
THE SOUTHWEST U.S. AS UPPER RIDGING BUILDS HEAT OVER THE WEST. THE
NORTHERN STREAM LOW SHOULD GAIN MOMENTUM HEADING INTO NEXT WEEKEND
AS IT TENDS TO SYNC INTO AMPLIFIED UPPER LEVEL TROUGHING. THIS
PATTERN WILL RESULT IN A PERIOD WITH AREAS OF WET UNSETTLED WEATHER
TO FOCUS FROM THE SOUTH-CENTRAL U.S. TO THE EAST/SOUTHEAST U.S. THIS
WEEK. MEANWHILE, A SERIES OF PACIFIC FRONTAL APPROACHES SLUGGISHLY
TOWARD THE PACIFIC NORTHWEST MAY OFFER SOME MODEST COASTAL RAINS
CHANCES INTO LATER WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE STILL OFFERS A REASONABLY SIMILAR LARGER SCALE PATTERN
EVOLUTION FOR THIS UPCOMING WEEK IN OVERALL SLOW TO TRANSITION
FLOW. HOWEVER, COMPLEX SYSTEM INTERACTIONS HAVE LED TO AN INCREASE
IN SMALLER SCALE FLOW VARIANCES THROUGH MEDIUM RANGE TIME SCALES,
ESPECIALLY EMINATING FROM NORTH-CENTRAL U.S. CLOSED LOW EVOLUTION.
ACCORDINGLY, FAVOR A BETTER COMPATIBLE 18 UTC GEFS MEAN AND 12 UTC
ECMWF/CANADIAN ENSEMBLE MEANS BLEND ALONG WITH BEST CLUSTERED MODEL
GUIDANCE FROM THE 12 UTC ECMWF AND TO A LESSER EXTENT THE 12 UTC
CANADIAN TO ADD REASONABLE DETAIL. THE COMPOSITE SEEMS TO MITIGATE
SMALLER SCALE ISSUES CONSISTENT WITH INDIVIDUAL PREDICTABILITY.
WPC PRODUCT CONTINUITY IS WELL MAINTAINED, WITH A SOLUTION IN LINE
WITH FAVORABLE 00 UTC GUIDANCE TRENDS OF THE ECMWF/CANADIAN/UKMET.
..WEATHER/HAZARDS HIGHLIGHTS
A SERIES OF WAVES WILL DEVELOP ALONG A FRONTAL SYSTEM EMINANTING
FROM THE SOUTH. THESE LOWS WILL SLOWLY PROGRESS DOWNSTREAM TO
FOCUS LOCALLY ENHANCED RAINS, WHILE POOLED MOISTURE FUELS LOCAL
DOWNPOURS NEAR A TRAILING FRONT BACK ACROSS THE SOUTH. DOWNPOUR
CHANCES WILL BE PROTRACTED WITH ADVENT AND REINFORCEMENT FROM
MIDWEST CYCLO/FRONTOGENESIS FROM NORTHERN STREAM ENERGIES THAT LEAD
INTO A LATER PERIOD AMPLIFIED UPPER TROUGH SIGNATURE OVER A
COOLED/UNSETTLED EAST. A DAY 4/WEDNESDAY WPC EXCESSIVE RAINFALL
OUTLOOK (ERO) MARGINAL RISK AREA SHOWS BEST FOCUS MAY LINGER OVER
THE EASTERN MID-ATLANTIC WITH LEAD LOW PASSAGE. THE DAY 4/5 EROS
ALSO OFFER A MARGINAL RISK AREA BACK OVER THE SOUTH-CENTRAL
PLAINS/ROCKIES AND LOWER MISSISSIPPI VALLEY GIVEN INDUCED RETURN
FLOW AND INSTABILITY/UPPER SUPPORT, WITH THE ACTIVE PATTERN LIKELY
TO LINGER LATER WEEK TO MONITOR, ESPECIALLY OVER THE MOIST SOUTH.
IN THE WEST, A BUILDING UPPER RIDGE WILL LEAD TO AN EXPANDING AREA
OF HEAT FROM THE INTERMOUNTAIN WEST INTO THE WEST COAST STATES
THIS WEEK, WITH TEMPERATURES RISING UPWARDS TO 10 TO 15+ DEGREES
ABOVE NORMAL. THIS IN PARTICULAR MAY LEAD TO A HAZARDOUS HEAT FOCUS
FOR THE CALIFORNIA CENTRAL VALLEY LATE WEEK/NEXT WEEKEND.
SCHICHTEL
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 (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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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