494
FXUS02 KWBC 080657
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 AM EDT TUE APR 8 2025
VALID 12Z FRI APR 11 2025 - 12Z TUE APR 15 2025
..GENERAL OVERVIEW
AN AMPLIFYING SHORTWAVE TROUGH ORIGINATING FROM SOUTH-CENTRAL
CANADA IS EXPECTED TO AMPLIFY AS IT DROPS SOUTHEAST ACROSS THE OHIO
VALLEY, TO SUPPORT A SURFACE LOW FROM THE MIDWEST TO THE MID-
ATLANTIC COAST TO CLOSE OUT THE WORK WEEK AND EMERGING OFF THE
COAST ON 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 COLD FRONT CROSSING THE INTERMOUNTAIN WEST
TO THE CENTRAL/NORTHERN PLAINS THROUGH NEXT MONDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z MODEL GUIDANCE SUITE INDICATES GOOD SYNOPTIC SCALE
AGREEMENT ACROSS THE CONTINENTAL U.S. ON FRIDAY. THERE ARE STILL
SOME DIFFERENCES IN THE SURFACE LOW EVOLUTION NEAR THE EAST COAST
AND WHETHER A SECONDARY LOW WILL FORM AND BECOME THE DOMINANT LOW
BY SATURDAY MORNING, BUT THAT IS NOW LOOKING MORE LIKELY. THE AREA
WITH THE GREATEST MODEL DIFFERENCES IS ACROSS THE WEST COAST REGION
GOING INTO SUNDAY AND ACROSS MUCH OF THE WESTERN U.S. MONDAY IN
REGARDS TO THE EVOLUTION OF THE TROUGH MOVING INLAND FROM THE
PACIFIC. THE 12Z CMC WAS MOST OUT OF ALIGNMENT WITH THE OVERALL
MODEL CONSENSUS AT THE TIME OF FRONTS PREPARATION, BUT THE 00Z CMC
HAS TRENDED MORE IN LINE WITH THE CONSENSUS.
THE WPC FRONTS/PRESSURES FORECAST WAS MAINLY BASED ON A GFS/ECMWF
BLEND ON FRIDAY AND SATURDAY, WITH SOME UKMET ALSO. THERE WAS
GRADUALLY INCREASING PROPORTIONS OF THE GEFS AND ECENS SUNDAY
THROUGH EARLY NEXT WEEK TO ABOUT HALF.
..WEATHER/HAZARDS HIGHLIGHTS
THE LOW PRESSURE SYSTEM CROSSING THE OHIO VALLEY AND THEN REACHING
THE EAST COAST TO CLOSE OUT THE WEEK WILL BE THE NEXT EVENT TO
MONITOR. A DEEPENING COASTAL LOW NEAR THE MID-ATLANTIC COAST ON
FRIDAY AND INTO EARLY SATURDAY SHOULD BRING HIGHER RAIN CHANCES AND
BREEZY CONDITIONS FROM THE CAROLINAS TO NEW ENGLAND. A MARGINAL
RISK AREA CONTINUES FOR DAY 4/FRIDAY FROM MARYLAND NORTHWARD TO
SOUTHERN NEW ENGLAND WITH MORE OF AN ENHANCED QPF SIGNAL IN THE
DETERMINISTIC GUIDANCE, WITH PERHAPS 1-2 INCHES OF RAINFALL FOR
SOME AREAS. HIGHER ELEVATION SNOWFALL IS ALSO LIKELY ACROSS
NORTHERN NEW ENGLAND FRIDAY NIGHT INTO SATURDAY. THE RAINFALL
BECOMES LIGHTER IN GENERAL BY SATURDAY ACROSS THE NORTHEAST, AND
FOR NOW THE DAY 5 ERO HAS NO RISK AREAS.
IN TERMS OF TEMPERATURES, A WARM PATTERN IS EXPECTED FOR THE
WESTERN U.S. FOR THE END OF THE WEEK WITH BOTH DAYTIME HIGHS AND
OVERNIGHT LOWS ABOUT 10-20 DEGREES ABOVE AVERAGE, WITH SOME
READINGS POTENTIALLY 25 DEGREES ABOVE AVERAGE ACROSS PORTIONS OF
WYOMING AND MONTANA. THESE MILDER CONDITIONS THEN REACH THE
CENTRAL AND NORTHERN PLAINS BY NEXT WEEKEND AS THE RIDGE SHIFTS
EASTWARD, WITH WIDESPREAD 15-25 DEGREE POSITIVE ANOMALIES ACROSS
THE CENTRAL PLAINS AND MIDWEST BY SUNDAY.
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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