030
FXUS02 KWBC 050652
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
252 AM EDT SAT APR 5 2025
VALID 12Z TUE APR 8 2025 - 12Z SAT APR 12 2025
..GENERAL OVERVIEW
A PATTERN CHANGE IS COMING FOR THE EASTERN HALF OF THE COUNTRY FOR
MUCH OF THE UPCOMING WEEK AFTER THE PASSAGE OF A STRONG COLD FRONT.
UPPER LEVEL TROUGHING SITUATED OVER THE GREAT LAKES AND NORTHEAST
WILL LEAD TO MUCH COOLER CONDITIONS COMPARED TO WHAT IS CURRENTLY
IN PLACE NOW. BY MIDWEEK, A SURFACE LOW DEVELOPS ACROSS THE CENTRAL
PLAINS AND REACHES THE MID-ATLANTIC REGION AROUND FRIDAY NIGHT,
BRINGING LIGHT TO MODERATE RAIN FROM THE MIDWEST TO THE EAST COAST,
AND PERHAPS SOME SNOW ACROSS PORTIONS OF THE GREAT LAKES. BY THE
END OF THE WEEK, AN UPPER RIDGE IS LIKELY TO BUILD ACROSS THE
INTERMOUNTAIN WEST AND ROCKIES, AND AN UPPER LEVEL TROUGH OFF THE
PACIFIC NORTHWEST COAST, WITH MULTIPLE ROUNDS OF RAIN AND MOUNTAIN
SNOW EXPECTED FOR WESTERN WASHINGTON AND OREGON.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z MODEL GUIDANCE SUITE INDICATES GOOD SYNOPTIC SCALE
AGREEMENT ACROSS THE CONTINENTAL U.S. ON TUESDAY, ALTHOUGH THERE
ARE STILL SOME MESOSCALE DIFFERENCES WITH THE SURFACE LOW EXITING
NEW ENGLAND THROUGH EARLY WEDNESDAY. THE GFS BECOMES STRONGER AND A
LITTLE FASTER WITH THE SURFACE LOW DEVELOPING OVER THE MIDWEST BY
MID-WEEK, BUT NOT TO THE SAME EXTENT AS YESTERDAY. GOING INTO THE
END OF THE WEEK, THE GUIDANCE IS MAINLY IN AGREEMENT WITH THE EC-
AIFS, WITH THE EXCEPTION THAT THE AIFS IS A LITTLE LESS AMPLIFIED
WITH THE TROUGH ACROSS THE OHIO VALLEY. BY SATURDAY, THERE ARE MORE
TIMING DIFFERENCES WITH THE ARRIVAL OF PACIFIC SHORTWAVES ACROSS
THE NORTHWESTERN U.S., AND THE GFS IS SLOWER WITH THE TROUGH ACROSS
THE SOUTHEAST STATES WHEN COMPARED TO THE CMC/ECMWF/AIFS.
THE WPC FRONTS/PRESSURES FORECAST WAS MAINLY BASED ON A MULTI-
DETERMINISTIC BLEND ON TUESDAY, AND THEN MAINLY 12Z ECMWF/18Z GFS
FOR WEDNESDAY AND THURSDAY WITH GRADUALLY INCREASING PROPORTIONS OF
THE GEFS AND ECENS THROUGH THE END OF THE WEEK, REACHING ABOUT 50%
ENSEMBLE MEANS BY NEXT SATURDAY.
..WEATHER/HAZARDS HIGHLIGHTS
THE HEAVY RAINFALL POTENTIAL DECREASES QUITE A BIT GOING INTO THE
TUESDAY AND WEDNESDAY TIME PERIOD, WITH NO RISK AREAS NECESSARY FOR
BOTH THE DAY 4 AND DAY 5 EXCESSIVE RAINFALL OUTLOOKS. WITH THE
EXCEPTION OF SOME LOCALLY HEAVY SHOWERS ACROSS PORTIONS OF THE
CENTRAL AND SOUTHERN FLORIDA PENINSULA, THE THREAT OF HEAVY
RAINFALL SHOULD BE OVER BY TUESDAY ACROSS THE REMAINDER OF THE
COUNTRY. IF FUTURE MODELS TREND HIGHER WITH QPF OVER SOUTH FLORIDA
DURING THIS TIME, IT IS POSSIBLE A MARGINAL RISK AREA MAY
EVENTUALLY BE NEEDED THERE AS WE ENTER THE SHORT RANGE FORECAST
PERIOD.
ELSEWHERE ACROSS THE COUNTRY, RAIN AND MOUNTAIN SNOW MAKES A
RETURN TO WESTERN WASHINGTON AND OREGON COURTESY OF ONSHORE FLOW
AND A COUPLE OF SHORTWAVE TROUGH PASSAGES NEXT WEEK, BUT THESE
DON'T LOOK LIKE MAJOR EVENTS AT THIS TIME. LIGHT PRECIPITATION
CROSSES THE NORTHERN PLAINS AND MIDWEST INTO MID-LATE NEXT WEEK,
AND THE NEXT GOOD CHANCE OF RAINFALL REACHES THE EASTERN U.S. BY
NEXT FRIDAY INTO SATURDAY AS A SURFACE LOW LIKELY DEVELOPS.
LINGERING SNOW IS ALSO LIKELY ACROSS PORTIONS OF NORTHERN NEW
ENGLAND THROUGH TUESDAY EVENING BEFORE THE SURFACE LOW DEPARTS THE
REGION TUESDAY NIGHT.
IN TERMS OF TEMPERATURES, MUCH COOLER CONDITIONS ARE COMING FOR THE
EASTERN U.S. AFTER THE STRONG COLD FRONT EXITS THE EAST COAST
BY MONDAY MORNING. AFTERNOON HIGHS ARE LIKELY TO BE ON THE ORDER
OF 10 TO 20 DEGREES BELOW EARLY APRIL AVERAGES ON TUESDAY AND
WEDNESDAY FROM THE OHIO VALLEY/GREAT LAKES TO THE NORTHEAST U.S.,
COMPLIMENTS OF THE UPPER LOW OVERHEAD. READINGS RETURN CLOSER TO
AVERAGE BY LATE IN THE WEEK FOR THE EAST COAST STATES WITH THE
UPPER TROUGH LIFTING OUT OF THE REGION. MEANWHILE, A WARM PATTERN
IS EXPECTED FOR THE WESTERN U.S. THROUGH THE WEEK WITH BOTH DAYTIME
HIGHS AND OVERNIGHT LOWS ABOUT 10-20 DEGREES ABOVE AVERAGE, WITH
THE GREATEST ANOMALIES OVER THE GREAT BASIN.
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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