656
FXUS02 KWBC 190736 AAC
PMDEPD
EXTENDED FORECAST DISCUSSION...UPDATED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
336 AM EDT TUE MAR 19 2024
VALID 12Z FRI MAR 22 2024 - 12Z TUE MAR 26 2024
***LATE SEASON WINTER STORM BECOMING MORE LIKELY FOR THE DAKOTAS
AND INTO PORTIONS OF THE UPPER MIDWEST***
..GENERAL OVERVIEW
A SPLIT UPPER LEVEL FLOW PATTERN IS FORECAST TO INITIALLY BE IN
PLACE ACROSS THE CONTINENTAL U.S. FOR THE END OF THE WEEK, WITH A
SHORTWAVE TROUGH CROSSING THE GULF COAST REGION AND THEN TRACKING
OFF THE EAST COAST, AND BROAD CYCLONIC FLOW ACROSS THE NORTH-
CENTRAL STATES. THE SOUTHERN SHORTWAVE IS EXPECTED TO PRODUCE A
SURFACE LOW OVER THE NORTHERN GULF, AND THEN THE LOW TRACKS OFF
THE SOUTHEAST COAST GOING INTO THE WEEKEND. 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 LATEST MODEL GUIDANCE CONTINUES TO SHOW REASONABLY GOOD
AGREEMENT ON THE SYNOPTIC SCALE TO CLOSE OUT THE WORK WEEK. THERE
CONTINUE TO BE SOME AMPLITUDE AND TIMING DIFFERENCES WITH THE
SOUTHEAST/GULF COAST LOW, WITH THE UKMET SLOWER AND FARTHER
INLAND, AND THE GFS CONTINUING ITS TREND OF A MORE NORTHERLY
TRACK. THE ENSEMBLE MEANS STILL SUPPORT THE IDEA OF A CLOSED CUT-
OFF LOW MEANDERING OFF THE SOUTHEAST. FOR THE LARGER SCALE TROUGH
DEVELOPING ACROSS THE ROCKIES SUNDAY INTO MONDAY, THE GFS IS SLOWER
THAN THE REST OF THE GUIDANCE WITH THE SHORTWAVE INTO THE
SOUTHWEST. THE CMC IS SLIGHTLY FASTER WITH IT DURING THIS TIME AS
IT AMPLIFIES OVER THE FOUR CORNERS REGION, AND IT HAS THE SURFACE
LOW FARTHER NORTHWEST OVER MINNESOTA.
THE WPC FORECAST BLEND INCORPORATED A BLEND OF THE OPERATIONAL
GUIDANCE FOR FRIDAY INTO SATURDAY AFTERNOON, WITH LESS OF THE GFS
OVER THE WEEKEND OWING TO THE MORE NORTHWARD TRACK OF THE LOW OFF
THE EAST COAST. FOR THE SUNDAY THROUGH TUESDAY TIME PERIOD, THE
ENSEMBLE MEANS WERE GRADUALLY INCREASED TO ABOUT 50%. OVERALL, THIS
MAINTAINED GOOD CONTINUITY WITH THE PREVIOUS WPC FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
THERE ARE STILL SOME UNCERTAINTIES IN THE EXPECTED MESOSCALE
EVOLUTION OF THE LOW DEVELOPING IN THE VICINITY OF THE SOUTHEAST
U.S. COAST ON FRIDAY, WITH MODEL GUIDANCE VARIED REGARDING
PLACEMENT OF HEAVIEST QPF AXES. HOWEVER, IT DOES APPEAR MORE
LIKELY THAT HEAVIER RAIN COULD FALL MORE INLAND COMPARED TO
EARLIER FORECASTS, AND THE MARGINAL RISK PLANNED FOR DAY 4 NOW
ENCOMPASSES MOST OF THE FLORIDA PENINSULA AND EXTENDING NORTH TO
CENTRAL NORTH CAROLINA. A SLIGHT RISK AREA COULD EVENTUALLY BE
NEEDED NEAR THE COASTAL CAROLINAS AND EVEN PARTS OF SOUTH FLORIDA,
BUT OVERALL FORECAST CONFIDENCE IS NOT YET HIGH ENOUGH IN EXACT
PLACEMENT. FOR THE DAY 5 PERIOD SATURDAY, THE CORE OF HEAVIEST
RAINFALL LIFTS NORTHEAST AND THE BEST PROSPECTS FOR HEAVIER
RAINFALL WOULD BE FROM EASTERN NORTH CAROLINA TO THE DELMARVA,
ALTHOUGH SOME GUIDANCE SUGGESTS IT COULD ALSO BE FARTHER INLAND.
THERE IS ALSO A MARGINAL RISK PLANNED BOTH DAYS FOR COASTAL
PORTIONS OF NORTHWESTERN CALIFORNIA AND SOUTHWESTERN OREGON WITH
MOISTURE FLUX FROM THE PACIFIC PRODUCING 1-3 INCHES OF QPF OVER
THIS TIME PERIOD.
ATTENTION THEN TURNS TO THE CENTRAL U.S. AS A POTENTIALLY STRONG
SURFACE LOW DEVELOPS IN THE LEE OF THE ROCKIES AND THEN TRACKS
TOWARDS THE MIDWEST BY MONDAY MORNING. THERE IS AN UPWARD TREND
FOR SNOWFALL ACCUMULATIONS FROM THE DAKOTAS TO MINNESOTA AND INTO
WISCONSIN, AS THIS REGION WILL LIKELY BE ON THE COLDER SIDE OF THE
LOW WITH A DEFORMATION ZONE LIKELY DEVELOPING, AND PRODUCING BANDS
OF HEAVIER WET SNOW WITH GUSTY WINDS. 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 TEXAS TO THE OHIO
VALLEY. SNOW SHOWERS ARE ALSO EXPECTED TO CONTINUE ACROSS MANY OF
THE WESTERN U.S. MOUNTAIN RANGES WITH THE UPPER TROUGH BUILDING IN.
THERE WILL LIKELY BE A STARK TEMPERATURE CONTRAST FROM THE CENTRAL
PLAINS/MIDWEST TO THE CANADIAN BORDER LATE IN THE WEEK. WINTER-
LIKE READINGS WILL CONTINUE ACROSS MONTANA, NORTH DAKOTA, AND INTO
NORTHERN MINNESOTA WITH A STRONG ARCTIC HIGH SITUATED OVER CENTRAL
CANADA PROVIDING COLD NORTHERLY FLOW. EVEN COLDER TEMPERATURES ARE
POSSIBLE FROM MONTANA TO THE CENTRAL PLAINS BY NEXT MONDAY BEHIND
THE STRONG COLD FRONT WITH SUBFREEZING HIGH TEMPERATURES FOR
MONTANA AND MOST OF THE DAKOTAS. 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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