506
FXUS02 KWBC 171908
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
308 PM EDT SUN MAR 17 2024
VALID 12Z WED MAR 20 2024 - 12Z SUN MAR 24 2024
..GENERAL OVERVIEW
THE ONGOING BLOCKY UPPER LEVEL PATTERN WITH THE UPPER HIGH OVER
THE PACIFIC NORTHWEST AND AN UPPER LOW OVER THE DESERT SOUTHWEST
SHOULD BREAK DOWN MIDWEEK, WHILE AN INTIAL UPPER TROUGH DOWNSTREAM
OVER THE NORTHEAST LOSES INFLUENCE. THE EJECTION OF THE SOUTHERN
STREAM TROUGH ORIGINATING FROM THE CLOSED UPPER LOW OVER THE
SOUTHWEST WILL LIKELY INDUCE AN ORGANIZED SURFACE LOW OVER THE GULF
THAT WILL INCREASE CHANCES FOR SHOWERS AND STORMS FROM TEXAS TO
FLORIDA, AND THEN UNCERTAINLY UP/OFF THE SOUTHEAST/EAST COAST NEXT
WEEKEND AS A COASTAL STORM. MEANWHILE, MULTIPLE AND COMPLEX
ENERGIES DIGGING INTO AN UPPER TROUGH POSITION OFF THE WEST COAST
ARE EXPECTED TO INCREASING WORK INLAND HEADING INTO NEXT WEEKEND
AND BRING A RESULT TO MORE UNSETTLED AND WET/SNOWY CONDITIONS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00/06 UTC MODEL GUIDANCE SUITE IS IN REASONABLY GOOD AGREEMENT
ON THE SYNOPTIC SCALE WEDNESDAY INTO FRIDAY OVERALL, ALBEIT WITH
LINGERNG TIMING DIFFERENCES WITH FLOW EMBEDDED SHORTWAVES WITH
DEVELOPMENT OF A MORE ZONAL FLOW PATTERN. THERE IS BETTER OVERALL
AGREEMENT IN THE SOUTHERN STREAM SHORTWAVE CROSSING THE SOUTH-
CENTRAL U.S., BUT MORE UNCERTAINTY AS TO WHERE THE CORRESPONDING
SURFACE LOW DEVELOPS OVER THE GULF BY LATE IN THE WEEK. A MODEL
COMPOSITE SEEMS REASONABLE IN THIS TIME FRAME.
THE FORECAST GETS TRICKY 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 OFFERED A MORE PROGRESSIVE AND
NORTHWARD TRACK OF THE SURFACE LOW UP/OFF THE COAST, EVEN COMPARED
TO THE GEFS MEAN WHICH IS MUCH MORE SUPPRESSED AND CLOSER TO THE
ECENS GUIDANCE, AND TO A LESSER EXTENT AN EVEN MORE SURPRESSED
ECMWF. GIVEN UPCERTAINTIES, OPTED FOR THE WPC SURFACE PROGS TO
GRAVITATE CLOSER TO THE GEFS/ECMWF ENSEMBLE MEANS, BUT LATEST 12
UTC MODEL GUIDANCE HAS BROADLY TRENDED MORE NORTHWARD OVERALL.
..WEATHER/HAZARDS HIGHLIGHTS
THERE WILL LIKELY BE AN INCREASE IN SHOWERS AND SOME THUNDERSTORMS
ACROSS PORTIONS OF TEXAS AND OKLAHOMA ON WEDNESDAY WITH WARM AIR
ADVECTION FROM THE WESTERN GULF AND LIFT FROM FRONTAL BOUNDARIES.
IT DOES NOT APPEAR THAT THE CONVECTION WOULD BE WIDESPREAD NOR
HEAVY ENOUGH TO WARRANT ANY WPC EXCESSIVE RAINFALL OUTLOOK (ERO)
MARGINAL RISKS AREAS AT THIS TIME, ALTHOUGH TRENDS WILL CONTINUE TO
BE MONITORED. 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. WHILE THE GREATEST RAINFALL TOTALS WILL REMAIN OFFSHORE
OVER THE GULF, ACTIVITY WILL GRADUALLY WORK TOWARD FLORIDA. THE
EVENTUAL EVOLUTION AND TRACK OF THE SURFACE LOW OFF THE SOUTHEAST
COAST AND POSSIBLY UP OFF THE EAST COAST NEXT WEEKEND (TBD) REMAINS
QUITE UNCERTAIN IN GUIDANCE, BUT CURRENTLY SEEMS TO FAVOR ENHANCED
RAINS UP THROUGH THE COASTAL CAROLINAS. ADDITIONAL ACTIVITY AND
ENHANCED WINDS UP THROUGH THE COASTAL MID-ATLANTIC AND NORTHEAST
ARE POSSIBLE IN GRADIENT 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 TO ESPECIALLY THE CANADIAN ROCKIES. ENHANCED RAINS
ARE EXPECTED TO SPREAD FROM THE PACIFIC NORTHWEST MID-LATER WEEK
DOWN INTO 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 WORK INLAND
ACROSS THE NORTH-CENTRAL GREAT BASIN AND THE NORTHERN ROCKIES/PLAINS,
THEN POSSIBLY THE UPPER MIDWEST INTO/THROUGH NEXT WEEKEND. COLD
CANADIAN HIGH PRESSURE WILL ENSURE WINTER-LIKE TEMPERATURES WILL
BE REINFORCED FROM THE NORTH-CENTRAL U.S. THROUGH THE NORTHEAST.
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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