443
FXUS02 KWBC 291750
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
150 PM EDT SUN OCT 29 2023
VALID 12Z WED NOV 01 2023 - 12Z SUN NOV 05 2023
..SYNOPTIC OVERVIEW
AN EXPANSIVE SURFACE HIGH WILL ENCOMPASS MUCH OF THE CENTRAL AND
EASTERN U.S. FOR THE MIDDLE OF THE WEEK WITH THE COLD FRONT
CLEARING THE FLORIDA COAST BY LATE WEDNESDAY. THIS AIRMASS WILL
BRING THE COLDEST AIR OF THE SEASON FOR MOST AREAS, WITH
WIDESPREAD FROST AND FREEZE CONDITIONS DURING THE OVERNIGHT HOURS
ACROSS MUCH OF THE SOUTH-CENTRAL STATES TO THE EAST COAST. THE
AIRMASS GRADUALLY MODIFIES BY THE END OF THE WEEK, AND A RENEWED
SURGE OF COLDER WEATHER ARRIVES FOR THE NORTHERN PLAINS AND UPPER
MIDWEST BY FRIDAY INTO NEXT WEEKEND. A STORM SYSTEM MOVING INLAND
ACROSS THE PACIFIC NORTHWEST AND NORTHERN ROCKIES IS EXPECTED TO
INCREASE PRECIPITATION ACROSS THESE AREAS BY WEDNESDAY AND
CONTINUING INTO THE END OF THE WEEK, WITH SOME SIGNAL OF AN
ATMOSPHERIC RIVER EVENT.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE 00/06Z GUIDANCE CAPTURED THE OVERALL SYNOPTIC EVOLUTION ACROSS
THE LOWER 48 REASONABLY WELL DURING THE MEDIUM RANGE PERIOD. A
FAIRLY ZONAL PATTERN ACROSS MUCH OF THE COUNTRY HELPED WITH THIS.
AN UPPER TROUGH EMERGING FROM THE EASTERN PACIFIC OVER THE PACIFIC
NORTHWEST. THE LATEST GUIDANCE HAS TRENDED STRONGER AND MORE WET
WITH THE EAST PAC SYSTEM THIS COMING THURSDAY/FRIDAY. THAT BEING
SAID, THERE'S STILL SOME UNCERTAINTY AROUND THE TIMING AND
STRENGTH OF THE SYSTEM. GIVEN THE ZONAL PATTERN THROUGH THE
PERIOD, A GENERAL MODEL BLEND CONSISTING OF THE 00Z EC/CMC/UKMET
AND 06Z GFS WERE UTILIZED THROUGH DAY 5 BEFORE A TRANSITION TO A
PREDOMINANTLY 00Z ECE/CMCE AND 06Z GEFS BASED BLEND.
..WEATHER/HAZARDS HIGHLIGHTS
MOST OF THE CONTINENTAL U.S. SHOULD BE RELATIVELY UNEVENTFUL IN
TERMS OF IMPACTFUL RAINFALL FOR THE MIDDLE TO END OF THE WEEK.
THE EXCEPTION TO THIS WILL BE ACROSS WESTERN OREGON AND WASHINGTON
WHERE A POTENTIAL ATMOSPHERIC RIVER EVENT MAY PRODUCE A FEW INCHES
OF RAINFALL FROM THE COASTAL RANGES OF NORTHERN CALIFORNIA TO THE
OLYMPIC MOUNTAINS OVER THE DAY 4 AND 5 TIME PERIOD. AT THIS TIME,
IT APPEARS THE GREATEST MOISTURE FLUX TOWARDS THE COAST WOULD BE
DURING THE TRANSITION PERIOD BETWEEN DAY 4 AND 5 (06Z THURSDAY --
18Z FRIDAY). THUS, THE MARGINAL RISK THAT WAS ISSUED OVERNIGHT FOR
DAY 4 WAS EXTENDED INTO DAY 5 WITH SOME EXPANSION INTO THE COASTAL
RANGES OF NORTHERN CALIFORNIA.
SOME LAKE EFFECT SNOW IS LIKELY FROM MICHIGAN TO UPSTATE NEW YORK
AS A STRONG SURGE OF COLD AIR ADVECTION RUSHES ACROSS THE WARMER
LAKE WATERS ON WEDNESDAY, WITH A FEW INCHES OF ACCUMULATION
POSSIBLE FOR SOME AREAS, BUT NOT LOOKING LIKE A MAJOR EVENT BY ANY
MEANS. LOOKING AHEAD TO THE END OF THE WEEK, PRECIPITATION
INCREASES ACROSS MUCH OF THE NORTHWESTERN STATES WITH POTENTIALLY
HEAVY SNOW FOR THE HIGHER MOUNTAIN RANGES. PARTS OF NORTHERN
CALIFORNIA MAY ALSO GET RAIN BY THE END OF THE WEEK.
THE COLD AIRMASS USHERED IN BY THE STRONG COLD FRONT ENGULFS ALL
OF THE CENTRAL AND EASTERN U.S., BY WEDNESDAY. WIDESPREAD
ANOMALIES ON THE ORDER OF 10 TO 20 DEGREES BELOW AVERAGE FOR THIS
TIME OF YEAR ARE EXPECTED FROM TEXAS TO THE EAST COAST ON
WEDNESDAY FOR HIGHS. THE FIRST FROST/FREEZE OF THE SEASON IS
EXPECTED FOR A VAST EXPANSE OF THE SOUTH-CENTRAL U.S. AND ALSO
EXTENDING INTO THE MAJOR METRO AREAS OF THE NORTHEAST U.S. GOING
INTO THE MIDDLE TO END OF THE WEEK. THIS AIRMASS SHOULD THEN
MODIFY GOING INTO FRIDAY AND BEYOND WITH TEMPERATURES CLOSER TO
AVERAGE AS A MORE ZONAL FLOW PATTERN EVOLVES.
KEBEDE/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, 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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