243
FXUS02 KWBC 060653
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
253 AM EDT SUN APR 6 2025
VALID 12Z WED APR 09 2025 - 12Z SUN APR 13 2025
..GENERAL OVERVIEW
THE LARGE UPPER TROUGH THAT WILL BE IN PLACE ACROSS THE NORTHEAST
U.S. EARLY IN THE WEEK IS FORECAST TO LIFT OUT OF THE REGION BY
THURSDAY. AN AMPLIFYING SHORTWAVE TROUGH ORIGINATING FROM SOUTH-
CENTRAL CANADA IS EXPECTED TO AMPLIFY AS IT DROPS SOUTHEAST ACROSS
THE OHIO VALLEY, AND THUS SUPPORT A SURFACE LOW FROM THE MIDWEST TO
THE MID-ATLANTIC COAST TO CLOSE OUT THE WORK WEEK AND EMERGING OFF
THE COAST NEXT SATURDAY. MEANWHILE, AN UPPER LEVEL RIDGE BUILDS
ACROSS THE INTERMOUNTAIN WEST AND ROCKIES THURSDAY INTO FRIDAY, AND
THEN SHIFTS EASTWARD TO THE PLAINS BY NEXT WEEKEND. WITH THE RIDGE
DEPARTING THE WEST, AN UPPER TROUGH APPROACHES FROM THE PACIFIC
NORTHWEST AND SUPPORTS A SLOW MOVING FRONTAL BOUNDARY ACROSS THE
INTERMOUNTAIN WEST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z MODEL GUIDANCE SUITE INDICATES GOOD SYNOPTIC SCALE
AGREEMENT ACROSS THE CONTINENTAL U.S. ON WEDNESDAY. SIMILAR TO
YESTERDAY, THE 18Z GFS BECOMES STRONGER AND MORE AMPLIFIED WITH
THE UPPER TROUGH ACROSS THE SOUTHEAST U.S. BY LATE FRIDAY, AND
INDICATES MORE OF A POTENTIAL NOR'EASTER TYPE SCENARIO OVER THE
WEEKEND OFF THE EAST COAST WHEN COMPARED TO THE CMC/ECMWF. THE 00Z
GFS IS WEAKER WITH THE OFFSHORE LOW COMPARED TO EARLIER RUNS, AND
MORE IN LINE WITH THE MODEL CONSENSUS.
THE WPC FRONTS/PRESSURES FORECAST WAS MAINLY BASED ON A MULTI-
DETERMINISTIC BLEND ON WEDNESDAY AND THURSDAY, WITH GRADUALLY
INCREASING PROPORTIONS OF THE GEFS AND ECENS THROUGH THE END OF THE
WEEK INTO NEXT WEEKEND, REACHING ABOUT 50% ENSEMBLE MEANS BY NEXT
SUNDAY.
..WEATHER/HAZARDS HIGHLIGHTS
THINGS CONTINUE TO LOOK UNEVENTFUL IN TERMS OF HEAVY RAINFALL
PROSPECTS FOR THE MIDDLE OF THE WEEK, WITH NO RISK AREAS CURRENTLY
NEEDED FOR THE EXCESSIVE RAINFALL OUTLOOKS FOR BOTH DAYS 4 AND 5.
HAVING SAID THAT, A SWATH OF MAINLY LIGHT TO MODERATE RAINFALL IS
EXPECTED FROM THE MIDWEST TO THE OHIO VALLEY, AND PERHAPS A SECOND
AREA OF RAINFALL DEVELOPING ACROSS THE TENNESSEE RIVER VALLEY ON
THURSDAY AS THE SURFACE LOW AND FRONT MOVES THROUGH. EVEN THOUGH
FORECAST RAINFALL TOTALS ARE NOT EXPECTED TO BE HEAVY, THE GROUND
WILL LIKELY STILL BE QUITE SATURATED FOR MANY OF THOSE AREAS AFTER
THE PROLIFIC RAINFALL LATELY, SO THAT IS SOMETHING THAT WILL
CONTINUE TO BE MONITORED. THE SURFACE LOW MAY RE-DEVELOP NEAR THE
MID-ATLANTIC COAST BY FRIDAY NIGHT AND RESULT IN HIGHER RAIN
CHANCES AND BREEZY CONDITIONS FROM VIRGINIA TO SOUTHERN NEW
ENGLAND GOING INTO SATURDAY.
ELSEWHERE ACROSS THE COUNTRY, PERIODS OF MODERATE RAIN AND
MOUNTAIN SNOW RETURN TO WESTERN WASHINGTON AND OREGON COURTESY OF
ONSHORE FLOW AND A COUPLE OF SHORTWAVE TROUGH PASSAGES MID TO LATE
WEEK, BUT THESE DON'T LOOK LIKE MAJOR EVENTS AT THIS TIME. LIGHT
SNOW THEN REACHES THE HIGHER ELEVATIONS OF THE NORTHERN ROCKIES BY
NEXT WEEKEND AS THE MOISTURE MOVES INLAND.
IN TERMS OF TEMPERATURES, THE COLDEST DAY OF THE FORECAST PERIOD
IS EXPECTED ON WEDNESDAY WITH HIGH TEMPERATURES RUNNING ABOUT
10-20 DEGREES BELOW AVERAGE. A MODERATING TREND COMMENCES BY THE
END OF THE WEEK AS THE UPPER TROUGH LIFTS OUT OF THE NORTHEAST
STATES. LOOKING AHEAD TO NEXT WEEKEND, LOWS SHOULD BE NEAR AVERAGE
WHILE DAYTIME HIGHS REMAIN SLIGHTLY BELOW AVERAGE. MEANWHILE, A
WARM PATTERN IS EXPECTED FOR THE WESTERN U.S. THROUGH THE END OF
THE WEEK WITH BOTH DAYTIME HIGHS AND OVERNIGHT LOWS ABOUT 10-20
DEGREES ABOVE AVERAGE, WITH THE GREATEST ANOMALIES OVER THE GREAT
BASIN. THESE MILDER CONDITIONS THEN REACH THE CENTRAL AND NORTHERN
PLAINS BY NEXT WEEKEND AS THE RIDGE SHIFTS EASTWARD.
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 (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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