042
FXUS02 KWBC 201859 AAC
PMDEPD
EXTENDED FORECAST DISCUSSION...UPDATED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 PM 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
MODEL GUIDANCE HAS BEEN RELATIVELY CONSISTENT IN BOTH THE OVERALL
PATTERN AND TRENDS WITHIN INDIVIDUAL RUNS REGARDING A SOUTHERN
STREAM SHORTWAVE/SUBSEQUENT GULF COAST TO SOUTHWEST ATLANTIC LOW
DEVELOPMENT THIS WEEKEND. THE LATEST 00Z ECMWF AND CMC CONTINUE TO
SHOW A LOW DEVELOPING ALONG THE NORTHERN GULF COAST AROUND
SATURDAY MORNING, TRACKING TO THE NORTHEAST OFF THE COAST OF THE
CAROLINAS BY SUNDAY MORNING. ON THE OTHER HAND, THE GFS HAS
MAINTAINED A SOLUTION SHOWING A MORE ACTIVE NORTHERN STREAM WAVE,
POTENTIALLY PHASING WITH SOME OF THE ENERGY FROM A FASTER MOVING
SOUTHERN STREAM SYSTEM, SUBSEQUENTLY ACCELERATING TO THE NORTH INTO
CANADA. SOME ENERGY REMAINS TO THE SOUTH BUT MAINTAINED/ADDITIONAL
SURFACE LOW DEVELOPMENT TAKES PLACE FAR OFFSHORE WITH NO REMAINING
SENSIBLE WEATHER IMPACTS FOR THE EAST COAST. THE UKMET MAINTAINS
ONLY A SOUTHERN STREAM SYSTEM SIMILAR TO THE ECMWF/CMC, HOWEVER THE
LOW PROGRESSION IS SLOWER.
THEN, MID-PERIOD EARLY NEXT WEEK, ATTENTION TURNS WESTWARD AS AN
AMPLIFYING WESTERN TROUGH LEADS TO LEE CYCLOGENESIS ALONG THE
ROCKIES, WITH THE DEEPENING LOW EVENTUALLY LIFTING NORTHEAST
THROUGH THE PLAINS/UPPER MIDWEST. ONCE AGAIN, THE 00Z ECMWF AND CMC
HAVE A SIMILAR SOLUTION IN TERMS OF TIMING AND TRACK OF THE
SURFACE SYSTEM THROUGH THE UPPER MIDWEST, TRAVERSING THE REGION
SUNDAY THROUGH TUESDAY, WHILE THE GFS IS FASTER AND BRINGS THE LOW
INTO CANADA BY AS EARLY AS TUESDAY MORNING. AVAILABLE DATA FROM THE
SUITE OF MACHINE LEARNING MODELS FROM THE EC SUPPORTS A SOLUTION
WITH SIMILAR TRACK/TIMING TO THE ECMWF/CMC, BOTH FOR THE EAST COAST
SYSTEM AS WELL AS THE CENTRAL U.S. LOW, FAVORING A SLOWER MOVEMENT
WHILE TRAVERSING THE UPPER MIDWEST. THE ICON ALSO FAVORS THE
ECMWF/CMC SOLUTION OFF THE EAST COAST, THOUGH DOES INDICATE MORE
UNCERTAINTY WITH THE SYSTEM OVER THE CENTRAL U.S., TAKING A MORE
SOUTHEASTERLY TRACK COMPARED TO THE ECMWF AND CMC.
THE UPDATED WPC FORECAST USES AN INITIAL COMPOSITE BLEND OF THE
DETERMINISTIC GUIDANCE BUT WITH PREFERENCE GIVEN TO THE ECMWF AND
CMC GIVEN BETTER CONSENSUS SUPPORT FOR THEIR HANDLING OF THE EAST
COAST AND CENTRAL U.S. SYSTEMS. THERE IS AN INCREASING
CONTRIBUTION FROM THE ECENS AND GEFS MEANS BY THE MIDDLE OF THE
PERIOD AS UNCERTAINTY REGARDING THE TIMING AND INTENSITY OF THE
CENTRAL U.S. SYSTEM GROWS, FAVORING A GREATER PERCENTAGE OF THE
ECENS GIVEN THE GEFS SHOWS A FASTER TREND SIMILAR TO THE GFS,
WHICH HAS LESS CONSENSUS SUPPORT. A 50/50 BLEND OF THE
DETERMINISTIC AND MEAN GUIDANCE IS USED BY THE END OF THE PERIOD
GIVEN INCREASING SPREAD HANDLING UPSTREAM ENERGIES OVER THE WEST.
..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 AND SOUTHERN
NEW ENGLAND, WITH A MARGINAL RISK ENCOMPASSING THE REGION. A
SLIGHT RISK IS INCLUDED 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 1-3 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 UPPER MIDWEST BY MONDAY MORNING. THERE CONTINUES TO BE
AN UPWARD TREND FOR SIGNIFICANT SNOWFALL ACCUMULATIONS (8"+) FROM
EASTERN MONTANA TO THE DAKOTAS, MINNESOTA, AND NORTHERN WISCONSIN,
AS THIS REGION WILL 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. A SWATH OF POTENTIALLY IMPACTFUL FREEZING RAIN MAY ALSO
OCCUR, MOST LIKELY TO THE SOUTHEAST OF THE HEAVY SNOW SWATH FROM
EASTERN NEBRASKA NORTHEASTWARDS THROUGH IOWA AND INTO SOUTHWESTERN
WISCONSIN. TIMING/TRACK UNCERTAINTY MAY CHANGE THE EVENTUAL
LOCATION OF THE IMPACTFUL WINTER WEATHER, BUT THE RISK FOR
DISRUPTIONS TO DAILY LIFE AND HAZARDOUS TRAVEL IS APPARENT.
MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS, SOME OF
WHICH COULD BE STRONG TO SEVERE, CAN BE EXPECTED IN THE WARM
SECTOR OF THE SYSTEM, BEGINNING FROM THE SOUTHERN PLAINS SUNDAY,
SPREADING EASTWARD TO THE MISSISSIPPI VALLEY MONDAY AND THE
CENTRAL GULF COAST TO THE OHIO VALLEY TUESDAY. THERE ARE STILL
QUESTION MARKS ABOUT HOW MUCH INSTABILITY WILL EXIST AHEAD OF THE
FRONT AS THE SYSTEM PROGRESSES EASTWARD, 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.
PUTNAM/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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page