879
FXUS02 KWBC 041848
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
248 PM EDT FRI APR 4 2025
VALID 12Z MON APR 07 2025 - 12Z FRI APR 11 2025
..GENERAL OVERVIEW
IT REMAINS GOOD NEWS THAT MAJOR IMPROVEMENT IS COMING TO THE AREAS
THAT ARE GETTING HAMMERED BY EXTREMELY HEAVY RAINFALL AND SEVERE
WEATHER FRIDAY AND INTO THIS WEEKEND. AN AMPLIFYING UPPER LEVEL
TROUGH OVER THE GREAT LAKES AND OHIO VALLEY REGION WILL ACCELERATE
A COLD FRONTAL PASSAGE, WITH THE WAVY BOUNDARY EXITING THE EAST
COAST ON MONDAY. THERE IS HOWEVER A THREAT FOR PLOWABLE SNOW/ICE
OVER THE NORTHERN TIER OF THE NORTHEAST THROUGH MONDAY AS A
SUPPORTING AND AMPLIFIED UPPER TROUGH AND WAVY LEAD FRONTS WORK
THROUGH. OTHERWISE, DRIER AND MUCH COOLER CONDITIONS WILL ARRIVE
BEHIND IT AND LIKELY REMAIN THROUGH MUCH OF NEXT WEEK. MEANWHILE
ACROSS THE WESTERN HALF OF THE COUNTRY, A COUPLE OF SHORTWAVES WILL
PASS THROUGH THE NORTHWESTERN STATES WITH SOME ORGANIZED
PRECIPITATION OVERTOP A MEAN RIDGE POSITION. THIS UPPER LEVEL RIDGE
IS EXPECTED TO BUILD OVER THE GREAT BASIN THEN ROCKIES LATER NEXT
WEEK, TO BE SANDWICHED BETWEEN A DOWNSTREAM TROUGH ACROSS THE EAST-
CENTRAL U.S. AND AN AMPLIFYING TROUGH OFF THE WEST COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST MODEL GUIDANCE INDICATES GOOD OVERALL AGREEMENT ACROSS THE
CONTINENTAL U.S. AND VICINITY FOR EARLY NEXT WEEK AND A MULTI-
DETERMINISTIC MODEL BLEND WORKS WELL AS A STARTING POINT FOR THIS
TIME FRAME. BY MIDWEEK, RECENT GFS AND TO A LESSER EXTENT GEFS RUNS
THROUGH THE 06 UTC CYCLE BECOME FASTER AND STRONGER WITH THE UPPER
PATTERN AND LOW PRESSURE SYSTEM DEVELOPING ACROSS THE PLAINS, AND
THIS CONTINUES GOING INTO THE END OF NEXT WEEK AS WELL.
EXAMINATION OF AIFS MACHINE LEARNING GUIDANCE FROM THE ECMWF AND
TELECONNECTIONS WITH POSITIVE/NEGATIVE 500MB HEIGHT ANOMALIES OVER
THE NORTH PACIFIC AND NORTH ATLANTIC SUPPORT THE IDEA OF A SLOWER
TROUGH EVOLUTION AND PROGRESSION ACROSS THE EASTERN U.S. FOR THE
SECOND HALF OF NEXT WEEK. THIS FALLS MORE IN LINE WITH THE
ECMWF/ECENS/CMC/CANADIAN ENSEMBLE MEAN SOLUTIONS AND THE WPC
FORECAST FOLLOWS THIS PREFERRED APPROACH, IN CONTRAST TO THE FASTER
GFS RUNS. HOWEVER, THE 12 UTC GFS HAS TRENDED MORE AMPLIFIED AND
SLOWER. THERE IS ALSO GROWING MODEL SPREAD WITH SHORTWAVE ENERGY
APPROACHING THE PACIFIC NORTHWEST LATE IN THE PERIOD, SO AN
ENSEMBLE MEAN APPROACH ALSO WORKS WELL FOR THIS REGION BY THURSDAY
INTO NEXT FRIDAY. GIVEN UNCERTAINTIES, OPTED TO SHIFT THE WPC
FORECAST BLEND TO AT LEAST 70% ECMWF/CANADIAN ENSEMBLE MEANS AND
NBM OVER/NEAR THE LOWER 48. THIS PLAN MAINTAINS GOOD WPC PRODUCT
CONTINUITY OVER OUR NATION.
..WEATHER/HAZARDS HIGHLIGHTS
THE HEAVY RAINFALL POTENTIAL DECREASES QUITE A BIT TO BEGIN NEXT
WEEK IN COMPARISON TO WHAT IS EXPECTED THIS WEEKEND. HOWEVER, THERE
WILL STILL BE AN AXIS OF DEEP MOISTURE OVER THE COASTAL PLAIN TO
COASTAL AREAS OF THE SOUTHEAST STATES AHEAD OF THE COLD FRONT,
WITH AREAL 1-2+ INCH TOTALS POSSIBLE FROM NORTHERN FLORIDA AND SOUTHERN
GEORGIA TO THE HAMPTON ROADS AREA OF SOUTHEAST VIRGINIA, MAINLY
BETWEEN 12Z MONDAY AND 00Z TUESDAY, WHERE A MARGINAL RISK OF
EXCESSIVE RAINFALL REMAINS IN EFFECT FOR THE DAY 4 ERO PERIOD.
WITH THE EXCEPTION OF THE CENTRAL AND SOUTHERN FLORIDA PENINSULA,
THE THREAT OF HEAVY RAINFALL SHOULD BE OVER BY TUESDAY ACROSS THE
REMAINDER OF THE COUNTRY WITH NO RISK AREAS NEEDED. 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.
THE WPC HAZARDS OUTLOOK ADDED A THREAT FOR PLOWABLE EARLY APRIL
SNOW/ICE ACROSS THE NORTHERN TIER OF THE NORTHEAST AS ENHANCED
LOCALLY BY TERRAIN THROUGH MONDAY WITH APPROACH OF AN AMPLIFIED
UPPER TROUGH AND WITH LEAD SURFACE FRONTS AND WRAPPING MOISTURE.
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 BY EARLY NEXT WEEK, BUT THIS
DOES NOT LOOK LIKE A MAJOR EVENT AT THIS TIME. LIGHT PRECIPITATION
CROSSES THE NORTHERN PLAINS AND MIDWEST INTO MID-LATE NEXT WEEK,
AND THE NEXT GOOD CHANCE OF RAINFALL MAY REACH INTO THE EASTERN
U.S. BY NEXT FRIDAY AS AN UNCERTAIN SURFACE LOW MAY DEVELOP.
IN TERMS OF TEMPERATURES, MUCH COOLER CONDITIONS ARE COMING FOR THE
EASTERN U.S. AFTER THE STRONG COLD FRONT EXITS THE EAST COAST
SUNDAY NIGHT/MONDAY MORNING. AFTERNOON HIGHS ARE LIKELY TO BE ON
THE ORDER OF 15 TO PERHAPS 25 DEGREES BELOW EARLY APRIL AVERAGES ON
TUESDAY FROM THE OHIO VALLEY TO THE EASTERN GREAT LAKES,
COMPLIMENTS OF THE UPPER LOW OVERHEAD. READINGS RETURN CLOSER TO
AVERAGE BY LATE IN THE WEEK FOR THE EAST COAST STATES. 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/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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