270
FXUS02 KWBC 111736
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
135 PM EDT WED OCT 11 2023
VALID 12Z SAT OCT 14 2023 - 12Z WED OCT 18 2023
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THERE IS DECENT AGREEMENT AMONG GLOBAL DETERMINISTIC GUIDANCE
THROUGH THIS WEEKEND WITH A CENTRAL PLAINS LOW THAT WEAKENS/OPENS
INTO A TROUGH OVER THE GREAT LAKES FRIDAY NIGHT AS IT JOINS A
TROUGH FROM AN EASTERN CANADIAN LOW. LIKEWISE WITH AN OMEGA HIGH
OVER NORTH-CENTRAL CANADA AND TROUGHING OFF THE PACIFIC NORTHWEST.
HOWEVER, BY SUNDAY NIGHT, THE 00Z ECMWF BEGINS TO OUTPACE ITS
ENSEMBLE MEAN WITH AN OPEN WAVE APPROACHING THE PACIFIC NORTHWEST
WHERE THE 00Z CMC/UKMET HAVE A SLOWER/CLOSED LOW AND THE 06Z GFS
IS FARTHER NORTH. GIVEN THE OUTPACING DETERMINISTIC RUN, THE MODEL
PREFERENCE SHIFTS FROM A GENERAL MODEL BLEND OVER THE WEEKEND TO
ONE FAVORING THE 00Z ECENS/06Z GEFS MEANS BY MONDAY. QPF BEGAN
WITH THE 13Z NBM WITH TIMING/MAGNITUDE BLENDING WITH THE ECMWF AND
GFS THROUGH SUNDAY, THEN IT WAS MORE OF AN EFFORT TO REDUCE THE
NBM COVERAGE BOTH EAST AND WEST EARLY NEXT WEEK DUE TO UNCERTAINTY
AND A LACK OF SIGNAL FOR EXCESSIVE RAIN. THE 12Z GFS FEATURES A
SHARPER TROUGH APPROACHING THE PACIFIC NORTHWEST ON MONDAY WHICH
IS MORE IN LINE WITH THE NON-ECMWF CONSENSUS.
..WEATHER/HAZARDS HIGHLIGHTS
A LOW TRACKING EAST FROM THE GREAT LAKES WEAKENS INTO A TROUGH
THIS WEEKEND AS IT REACHES STALLS OVER THE NORTHEAST. MODERATE TO
LOCALIZED HEAVY RAINS ARE FORECAST ACROSS THE NORTH-CENTRAL
MID-ATLANTIC. A MARGINAL RISK IS MAINTAINED FOR THE DAY 4/SATURDAY
EXCESSIVE RAINFALL OUTLOOK WITH A BIT OF A TRIM FROM THE NORTH
BASED ON THE LATEST GUIDANCE. MEANWHILE, A COMPLEX SERIES OF
SYSTEMS WILL ACT TO AMPLIFY AN EASTERN PACIFIC UPPER TROUGH
POSITION AND ALSO BRING MOISTURE TO THE PACIFIC NORTHWEST COAST TO
FUEL MODERATE TO POSSIBLY HEAVY PRECIPITATION FOR FAVORED TERRAIN
OF THE CASCADES IN A WET PERIOD LATE WEEKEND/NEXT WEEK. HOWEVER,
LOW ENOUGH PRECIPITATION RATES WARRANT NO EXCESSIVE RAINFALL RISK
FOR DAY 5/SUNDAY.
THE COLD FRONT SWEEPING ACROSS THE EASTERN U.S. SATURDAY INTO
SUNDAY WILL BRING TEMPERATURES GENERALLY 10 TO 15 DEGREES BELOW
NORMAL, INCLUDING SOUTH FLORIDA WHICH WILL SEE NEAR RECORD HIGH
TEMPERATURES IN THE LOW TO MID 90S THROUGH SATURDAY. MEANWHILE, A
BUILDING RIDGE OVER THE WEST-CENTRAL U.S. BRINGS TEMPERATURES
GENERALLY 5 TO 10 DEGREES ABOVE NORMAL WEST FROM THE ROCKIES TO
THE EASTERN LEE OF THE CASCADES.
JACKSON
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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