601
FXUS02 KWBC 191832
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
132 PM EST MON FEB 19 2024
VALID 12Z THU FEB 22 2024 - 12Z MON FEB 26 2024
..OVERVIEW
AN UPPER LEVEL TROUGH/DEEP CYCLONE ESTABLISHES ITSELF BRIEFLY
ACROSS SOUTHEAST CANADA/THE NORTHEAST SATURDAY MORNING, COOLING
THE REGION OFF TEMPORARILY, BEFORE ZONAL FLOW IN THE NORTHERN
STREAM SCOOTS IT OUT TO SEA. A PHASED TROUGH MOVES INTO THE WEST
BY NEXT MONDAY, BRINGING MORE PRECIPITATION TO THE REGION.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE GUIDANCE SHOWS RATHER GOOD AGREEMENT UNTIL LATE IN THE PERIOD,
WHEN THE 00Z ECMWF OUTPACES THE REMAINDER OF THE GUIDANCE SUITE.
THE PRESSURES, WINDS, 500 HPA HEIGHTS, AND QPF WERE BASED ON A
BLEND OF THE 06Z GFS, 00Z ECMWF, 00Z UKMET, AND 00Z CANADIAN.
ENSEMBLE MEANS WERE USED FOR MOST FIELDS LATE IN THE PERIOD. THE
REMAINDER OF THE GRIDS WERE PRIMARILY BASED ON THE 13Z NBM, WHICH
WERE THEN MODIFIED TO FIT THE FORECAST QPF, POP-WISE.
..WEATHER/HAZARDS HIGHLIGHTS
PRECIPITATION SHOULD INCREASE IN COVERAGE AND INTENSITY (TO SOME
DEGREE) OVER PORTIONS OF THE OHIO VALLEY THURSDAY WITHIN A
MOISTURE PLUME IN A WARM AIR ADVECTION REGIME. RAINFALL AMOUNTS OF
AN INCH OR TWO ARE LIKELY IN THE OHIO VALLEY, WITH LOCALLY HIGHER
AMOUNTS. SOME COMPETING FACTORS ARE IN PLACE REGARDING WHETHER
THIS RAINFALL WILL LEAD TO A FLASH FLOODING THREAT. SOME
INSTABILITY COMBINED WITH GOOD DYNAMICAL SUPPORT (LEFT EXIT REGION
OF THE JET) MAY LEAD TO HIGH RAINFALL RATES (IN THIS CASE, 0.5-1"
IN AN HOUR). DEEP WEST-SOUTHWESTERLY FLOW COULD ALLOW FOR SOME
CELL TRAINING, BUT AT THE MOMENT, MU CAPE APPEARS TO MAX OUT IN
THE 250 J/KG RANGE. FLASH FLOOD GUIDANCE IS FAIRLY LOW IN AND
NEAR THE EASTERN KY AND WV COAL FIELDS, AS YOU'D EXPECT. THE
EXCESSIVE RAINFALL OUTLOOK SHRANK THE AREA OF THE MARGINAL RISK
ACROSS THE OHIO VALLEY TO CENTRAL APPALACHIANS, CONFORMING TO THE
AREA OF LOWEST FLASH FLOOD GUIDANCE. THE PRECIPITATION SHOULD
REACH THE EAST THURSDAY-FRIDAY WITH SNOW POSSIBLE IN PARTS OF THE
NORTHEAST. NORTHERN NEW ENGLAND HAS A RELATIVELY HIGHER
PROBABILITY OF SEEING NOTABLE SNOW ALONG WITH THE POTENTIAL FOR A
PERIOD OF BRISK WINDS. THERE IS STILL UNCERTAINTY WITH THE SNOW
AMOUNTS AND PLACEMENT. BEHIND THIS SYSTEM, PARTS OF THE GREAT
LAKES MAY SEE MOSTLY LIGHT SNOW FROM A COMBINATION OF LAKE EFFECT
AND LAKE ENHANCED ACTIVITY CAUSED BY NEARBY FRONTS.
THE WEST WILL SEE A BREAK FROM PRECIPITATION AROUND
THURSDAY-FRIDAY WITH A BOUT OF RIDGING ALOFT. AN EASTERN PACIFIC
UPPER LOW AND ITS SURFACE REFLECTION WILL MEANDER AND GRADUALLY
DRIFT CLOSER TO THE WEST COAST, SPREADING PRECIPITATION CHANCES TO
CALIFORNIA BY LATE FRIDAY-SATURDAY. BY SUNDAY MODEL GUIDANCE IS
MORE AGREEABLE THAT PRECIPITATION SHOULD SPREAD INTO THE PACIFIC
NORTHWEST AND CALIFORNIA WITH SOME MOISTURE SPREADING FARTHER
INLAND INTO THE INTERMOUNTAIN WEST.
AREAS FROM THE PLAINS/MIDWEST EASTWARD WILL SEE ABOVE NORMAL
TEMPERATURES THURSDAY WITH THE EXCEPTION OF A COOLER FLORIDA
PENINSULA. TEMPERATURES LOOK TO MODERATE CLOSER TO AVERAGE IN THE
EAST LATE WEEK AFTER A COLD FRONTAL PASSAGE OR TWO, LIKELY
REACHING BELOW AVERAGE FOR HIGHS IN THE NORTHEAST SATURDAY.
MEANWHILE RENEWED UPPER RIDGING IN THE WEST-CENTRAL U.S. WILL
PROMOTE TEMPERATURES WARMING EVEN FURTHER BY THE WEEKEND INTO
EARLY NEXT WEEK FOR MUCH OF THE PLAINS AND MISSISSIPPI VALLEY.
TEMPERATURES 15-30F ABOVE NORMAL FOR LATE FEBRUARY WILL BE COMMON
IN THE GREAT PLAINS AS FORECAST HIGHS GET INTO THE 80S FOR MUCH OF
TEXAS EARLY NEXT WEEK WITH 60S MAKING IN ROADS INTO THE DAKOTAS.
MEANWHILE THE WESTERN U.S. SHOULD BE NEAR TO SLIGHTLY ABOVE
NORMAL.
ROTH
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, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES ARE AT:
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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