543
FXUS02 KWBC 200657 AAC
PMDEPD
EXTENDED FORECAST DISCUSSION...UPDATED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 AM EDT WED MAR 20 2024
VALID 12Z SAT MAR 23 2024 - 12Z WED MAR 27 2024
***LATE SEASON WINTER STORM BECOMING MORE LIKELY FOR THE DAKOTAS
AND INTO MINNESOTA AND WISCONSIN***
..GENERAL OVERVIEW
THE SHORTWAVE TROUGH CROSSING THE SOUTHEAST U.S. ON FRIDAY AND INTO
SATURDAY WILL PRODUCE A SURFACE LOW OVER THE NORTHEASTERN GULF,
AND THEN DEVELOP FURTHER AS IT TRACKS OFF THE SOUTHEAST COAST GOING
INTO THE WEEKEND, PRODUCING HEAVY RAIN AND GUSTY WINDS FOR MANY
COASTAL AREAS. LOOKING AHEAD TO THE SUNDAY TO TUESDAY TIME PERIOD,
A PATTERN CHANGE EVOLVES ACROSS THE WESTERN HALF OF THE U.S. AS A
LARGER SYNOPTIC SCALE TROUGH DEVELOPS ACROSS THE INTERMOUNTAIN WEST
AND ROCKIES. THIS WILL LEAD TO SURFACE CYCLOGENESIS ACROSS THE
CENTRAL PLAINS AND MIDWEST, BRINGING A LATE SEASON WINTER STORM TO
PARTS OF THE NORTHERN PLAINS, AND STRONG THUNDERSTORMS ACROSS
PORTIONS OF THE SOUTH.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE FORECAST PERIOD BEGINS ON SATURDAY WITH RELATIVELY GOOD OVERALL
DETERMINISTIC MODEL AGREEMENT, ALTHOUGH THE UKMET IS SLOWER AND
FARTHER WEST WITH THE SURFACE LOW DEVELOPING OVER THE SOUTHEAST
STATES. THIS TREND CONTINUES WITH THE UKMET GOING INTO MONDAY WITH
A SOLUTION THAT IS WELL TO THE WEST OF THE ENSEMBLE MEANS, AND IT
ALSO IS CONSIDERABLY SLOWER BRINGING OUT THE LOW ACROSS THE PLAINS
ON MONDAY. THE GFS CONTINUES WITH THE IDEA OF SPLITTING THE EAST
COAST LOW INTO A NORTHERN STREAM COMPONENT THAT RACES TOWARDS THE
NORTHEAST, AND THE SOUTHERN PORTION THAT IS MORE IN LINE WITH THE
ECMWF AND CMC SOLUTIONS. LOOKING AHEAD TO TUESDAY AND BEYOND, THE
GFS STRAYS FROM THE CONSENSUS BY ACCELERATING THE UPPER MIDWEST LOW
INTO ONTARIO AND FASTER THAN THE GEFS MEAN. THE NEXT SYSTEM
ENTERING THE PACIFIC NORTHWEST FEATURES GREATER MODEL DIFFERENCES,
WITH A WEAK FEATURE BEING DEPICTED FOR NOW UNTIL A CLEARER TREND
EMERGES IN THE GUIDANCE.
THE WPC FORECAST WAS PRIMARILY BASED ON A CMC/GFS/ECMWF BLEND AS A
STARTING POINT FOR THE WEEKEND OWING TO THE DIFFERENCES NOTED IN
THE UKMET, AND THEN LESS GFS BY TUESDAY AND INCREASING PROPORTIONS
OF THE ENSEMBLE MEANS TO ABOUT 50% BY NEXT WEDNESDAY.
..WEATHER/HAZARDS HIGHLIGHTS
ON SATURDAY, THE CORE OF HEAVIEST RAINFALL LIFTS NORTHEAST AND THE
BEST PROSPECTS FOR HEAVY RAINFALL WOULD BE FROM EASTERN NORTH
CAROLINA TO THE DELMARVA AND INTO COASTAL NEW JERSEY. THE HIGHEST
UNCERTAINTY IS WITH NORTHWARD EXTENT, WITH GREATER CONFIDENCE FOR
HEAVIER TOTALS ACROSS THE COASTAL MID-ATLANTIC, AND THEN
POTENTIALLY INTO SOUTHERN NEW ENGLAND. THEREFORE, THE MARGINAL RISK
HAS BEEN EXTENDED NORTHEASTWARD TO ENCOMPASS MORE OF THE MID-
ATLANTIC AND NOW REACHING PORTIONS OF SOUTHERN NEW ENGLAND. A
SLIGHT RISK IS PLANNED FROM THE NORTHERN DELMARVA TO CENTRAL NEW
JERSEY, WHERE A STRONGER MODEL SIGNAL EXISTS FOR A FEW INCHES OF
RAINFALL DURING THE DAY 4 PERIOD. ON SUNDAY, A MARGINAL RISK AREA
IS PLANNED FOR PORTIONS OF THE CENTRAL PLAINS WITH A CORRIDOR OF
HEAVIER RAIN LIKELY DEVELOPING FROM NORTHERN KANSAS TO EASTERN
NEBRASKA AS THE SURFACE LOW TRACKS BY. FOR THE WEST, THERE IS A
MARGINAL RISK PLANNED ON SATURDAY FOR COASTAL PORTIONS OF
NORTHWESTERN CALIFORNIA AND SOUTHWESTERN OREGON WITH MOISTURE FLUX
FROM THE PACIFIC, PRODUCING 1-2 INCHES OF QPF HERE.
ATTENTION THEN TURNS TO THE CENTRAL U.S. AS A STRONG SURFACE LOW IS
FORECAST TO DEVELOP IN THE LEE OF THE ROCKIES, AND THEN TRACKS
TOWARDS THE MIDWEST BY MONDAY MORNING. THERE CONTINUES TO BE AN
UPWARD TREND FOR SNOWFALL ACCUMULATIONS FROM EASTERN MONTANA TO
THE DAKOTAS, MINNESOTA, AND NORTHERN WISCONSIN, AS THIS REGION
WILL LIKELY BE ON THE COLDER SIDE OF THE LOW WITH A DEFORMATION
ZONE DEVELOPING, AND PRODUCING BANDS OF HEAVIER WET SNOW WITH
GUSTY WINDS. THERE HAS BEEN A NORTHWESTWARD TREND FOR THE HIGHER
SNOWFALL TOTALS ACROSS THE UPPER MIDWEST COMPARED TO YESTERDAY.
MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS, SOME OF
WHICH COULD BE STRONG TO SEVERE, CAN BE EXPECTED IN THE WARM SECTOR
OF THE LOW FROM THE CENTRAL GULF COAST TO THE OHIO VALLEY. THERE
ARE STILL QUESTION MARKS ABOUT HOW MUCH INSTABILITY WILL EXIST
AHEAD OF THE FRONT, EVEN THOUGH THE KINEMATIC ENVIRONMENT WILL BE
MORE FAVORABLE FOR POTENTIAL SEVERE WEATHER. SNOW SHOWERS ARE ALSO
EXPECTED TO CONTINUE ACROSS MANY OF THE WESTERN U.S. MOUNTAIN
RANGES WITH THE UPPER TROUGH BUILDING IN.
IN TERMS OF TEMPERATURES, WINTER-LIKE READINGS WILL CONTINUE
ACROSS THE NORTH-CENTRAL U.S. WITH A STRONG ARCTIC HIGH SITUATED
OVER CENTRAL CANADA PROVIDING COLD NORTHERLY FLOW. MEANWHILE, A
PLEASANT WARM-UP IS LIKELY AHEAD OF THE DEVELOPING STORM SYSTEM
FROM THE DEEP SOUTH TO THE OHIO VALLEY.
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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