980
FXUS02 KWBC 180656
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 AM EDT MON MAR 18 2024
VALID 12Z THU MAR 21 2024 - 12Z MON MAR 25 2024
..GENERAL OVERVIEW
A SPLIT UPPER LEVEL FLOW PATTERN IS FORECAST TO BE IN PLACE ACROSS
THE CONTINENTAL U.S. FOR THE END OF THE WEEK, WITH A SHORTWAVE
TROUGH CROSSING THE GULF COAST REGION AND BROAD CYCLONIC FLOW
ACROSS THE NORTH-CENTRAL STATES. THE SOUTHERN SHORTWAVE IS EXPECTED
TO SPUR SURFACE CYCLOGENESIS OVER THE NORTHERN GULF AND THEN THE
LOW TRACKS OFF THE SOUTHEAST COAST GOING INTO THE WEEKEND. LOOKING
AHEAD TO SUNDAY AND NEXT MONDAY, A LARGER SYNOPTIC SCALE TROUGH
LIKELY DEVELOPS ACROSS THE WESTERN U.S. WITH AN ORGANIZED LOW
PRESSURE SYSTEM DEVELOPING OVER THE PLAINS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z MODEL GUIDANCE SUITE IS IN REASONABLY GOOD AGREEMENT ON
THE SYNOPTIC SCALE ON THURSDAY, ALTHOUGH THERE ARE SOME AMPLITUDE
DIFFERENCES WITH THE GULF COAST TROUGH AND THE SOUTHWARD EXTENSION
OF THE DEEP UPPER LOW OVER CENTRAL CANADA. A GENERAL MODEL
COMPROMISE SEEMS REASONABLE FOR THE END OF THE WEEK.
THE FORECAST GETS MORE CHALLENGING GOING INTO NEXT WEEKEND FOR THE
EAST COAST REGARDING THE LIKELY EVOLUTION OF AN OFFSHORE SURFACE
LOW. RECENT RUNS OF THE GFS AND CANADIAN TEND TO OFFER A MORE
PROGRESSIVE AND NORTHWARD TRACK OF THE SURFACE LOW UP THE COAST,
EVEN COMPARED TO THE GEFS MEAN WHICH IS MUCH MORE SUPPRESSED AND
CLOSER TO THE ECENS GUIDANCE. GIVEN THE ONGOING UNCERTAINTIES IN
THE EVENTUAL TRACK OF THAT LOW, THE PREFERENCE IS FOR SOMETHING
CLOSER TO THE GEFS/ECMWF ENSEMBLE MEANS. THE WPC QPF WAS REDUCED
ACROSS THE NORTHEAST COMPARED TO THE NBM GIVEN THE MUCH FARTHER
NORTH TRACK OF THE GFS THAT IS NOT CURRENTLY PREFERRED.
..WEATHER/HAZARDS HIGHLIGHTS
WITH THE LOW BEGINNING TO DEVELOP OVER THE GULF THURSDAY INTO
FRIDAY, AN AXIS OF GREATER MOISTURE FLUX NEAR THE COAST MAY RESULT
IN HEAVIER LOCAL DOWNPOURS FROM SOUTHEAST TEXAS TO SOUTHERN
LOUISIANA, WHERE AN ERO MARGINAL RISK AREA REMAINS IN PLACE FOR THE
DAY 4 PERIOD. WHILE THE GREATEST RAINFALL TOTALS ARE FORECAST TO
REMAIN OFFSHORE OVER THE NORTHERN GULF, ACTIVITY WILL GRADUALLY
PROGRESS TOWARD THE FLORIDA PENINSULA ON FRIDAY, WITH POTENTIAL FOR
SOME LOCALIZED HEAVY RAINFALL ACROSS PORTIONS OF SOUTHERN FLORIDA
WHERE A DAY 5 MARGINAL RISK AREA IS PLANNED. THE EVENTUAL
EVOLUTION AND TRACK OF THE SURFACE LOW OFF THE SOUTHEAST COAST AND
POSSIBLY UP OFF THE EAST COAST FRIDAY INTO NEXT WEEKEND REMAINS
QUITE UNCERTAIN IN GUIDANCE, BUT CURRENTLY SEEMS TO FAVOR ENHANCED
RAINS UP THROUGH THE COASTAL CAROLINAS, WHERE A DAY 5 MARGINAL RISK
AREA IS ALSO PLANNED. ADDITIONAL RAINFALL AND ENHANCED WINDS NEAR
THE COASTAL MID-ATLANTIC AND NORTHEAST ARE POSSIBLE IN GRADIENT
FLOW BETWEEN THE WESTERN ATLANTIC COASTAL LOW AND AMBIENT HIGH
PRESSURE WEDGED INLAND OVER THE REGION.
MEANWHILE, MULTIPLE ROUNDS OF MAINLY LIGHT SNOW ARE FORECAST WITH
A HEAVIER SNOW FOCUS FOR FAVORED TERRAIN OF WESTERN MONTANA AND
NORTHERN IDAHO, AND ALSO THE CANADIAN ROCKIES. ENHANCED RAINS ARE
EXPECTED TO SPREAD FROM THE PACIFIC NORTHWEST DOWN ACROSS
CALIFORNIA BY FRIDAY AND INTO SATURDAY AS THE NEXT STORM SYSTEM
MOVES INTO THE REGION, WITH TERRAIN FOCUSING SNOWS FOR THE CENTRAL
AND NORTHERN SIERRA. ACTIVITY SHOULD ALSO PROGRESS INLAND ACROSS
THE NORTH-CENTRAL GREAT BASIN AND THE NORTHERN ROCKIES/PLAINS,
THEN PROBABLY THE UPPER MIDWEST INTO NEXT WEEKEND. THERE MAY BE A
CORRIDOR OF MORE ENHANCED SNOW ON THE NORTHWEST SIDE OF A
DEVELOPING SURFACE LOW ACROSS THE DAKOTAS AND INTO MINNESOTA
TOWARDS THE END OF THE FORECAST PERIOD LATE SUNDAY INTO MONDAY.
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. ABOVE NORMAL TEMPERATURES
ACROSS THE INTERMOUNTAIN WEST MIDWEEK ARE EXPECTED TO COOL DOWN TO
BELOW AVERAGE LEVELS WITH THE UPPER TROUGH DEVELOPING LATE IN THE
FORECAST PERIOD. EVEN COLDER TEMPERATURES ARE POSSIBLE FROM MONTANA
TO THE CENTRAL PLAINS BY NEXT MONDAY BEHIND A STRONG COLD FRONT
WITH SUBFREEZING HIGH TEMPERATURES FOR MONTANA AND MOST OF THE
DAKOTAS.
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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