021
FXUS02 KWBC 280655
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
255 AM EDT SAT OCT 28 2023
VALID 12Z TUE OCT 31 2023 - 12Z SAT NOV 4 2023
..SYNOPTIC OVERVIEW
THE STRONG COLD FRONT THAT WILL DELIVER THE COLDEST AIR MASS SO
FAR THIS SEASON IS EXPECTED TO CLEAR THE SOUTHEAST U.S. COAST BY
TUESDAY MORNING, AND THEN CLEAR THE FLORIDA PENINSULA BY LATE
WEDNESDAY, WITH A STRONG SURFACE HIGH BUILDING IN BEHIND THE
FRONT. A COUPLE OF REINFORCING UPPER TROUGHS WILL GIVE THIS
COLDER AIRMASS SOME STAYING POWER ACROSS MUCH OF THE CENTRAL AND
EASTERN STATES, WITH PERHAPS THE FIRST NOTABLE LAKE EFFECT SNOW
EVENT OF THE SEASON, AND A LOW PRESSURE SYSTEM DEVELOPING OFF THE
NEW ENGLAND COAST. THE AIRMASS SHOULD GRADUALLY MODIFY SOME GOING
INTO THE END OF NEXT WEEK, AND A PACIFIC STORM SYSTEM APPROACHING
THE NORTHWESTERN COAST WILL INCREASE THE PROSPECTS FOR RAIN AND
MOUNTAIN SNOW TO CLOSE OUT THE WORK WEEK AND INTO NEXT SATURDAY.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
QUESTION MARKS STILL REMAIN FOR THE DEVELOPMENT OF A COASTAL
SURFACE LOW OFF THE NEW ENGLAND COAST MID-WEEK. THE PAST FEW RUNS
OF THE GFS/GEFS HAVE BEEN CONSISTENTLY MORE PROGRESSIVE WITH A
POTENT MID-UPPER LEVEL NORTHERN STREAM TROUGH ACROSS THE GREAT
LAKES REGION, AND THE PAST FEW ECMWF/ECENS/CMC RUNS HAVE ALSO BEEN
CONSISTENT WITH A SLOWER AND A LITTLE MORE AMPLIFIED SOLUTION,
WHICH ALSO HAS SOME SUPPORT FROM THE UKMET AND ICON MODELS. WPC
CONTINUITY ALSO FAVORS THE SLOWER SIDE OF THE NON-NCEP GUIDANCE
FOR THIS FORECAST CYCLE, AND THIS RESULTS IN A LOW DEVELOPING
CLOSER TO THE COAST DUE TO THE INCOMING SHORTWAVE TROUGH, IN
CONTRAST TO THE GFS WHICH HAS THE LOW WELL TO THE EAST OF THE
MODEL CONSENSUS. LOOKING AHEAD TO THE END OF THE WEEK AND NEXT
SATURDAY, THE GFS IS ALSO MORE PROGRESSIVE WITH THE PACIFIC TROUGH
AND FRONT MOVING INLAND ACROSS THE INTERMOUNTAIN WEST, AND THE
ECMWF IS STRONGER WITH A SECOND TROUGH APPROACHING THE PACIFIC
NORTHWEST ON SATURDAY. THE ENSEMBLE MEANS ACCOUNTED FOR ABOUT
HALF OF THE FORECAST BLEND BY NEXT SATURDAY.
..WEATHER/HAZARDS HIGHLIGHTS
IN CONTRAST TO THE HEAVY RAINFALL EXPECTED OVER THE NEXT COUPLE OF
DAYS ACROSS THE SOUTH-CENTRAL U.S., THE EXTENDED FORECAST GOING
INTO EARLY NEXT WEEK FEATURES A RETURN TO MUCH QUIETER CONDITIONS
IN TERMS OF RAINFALL ACROSS THE ENTIRE COUNTRY. THE RAINFALL
EXPECTED BEHIND THE STRONG COLD FRONT AND IN ASSOCIATION WITH THE
OFFSHORE ATLANTIC LOW SHOULD BE BELOW THE THRESHOLDS OF ANY
EXCESSIVE RAINFALL HEADLINES. THERE MAY BE SOME LOCATIONS THAT
GET 0.5 TO 1 INCH OF RAINFALL ON TUESDAY AND INTO EARLY WEDNESDAY
NEAR THE MID-ATLANTIC COAST, BUT THE INTENSITY IS EXPECTED TO BE
ONLY LIGHT TO MODERATE. FOR THE DAY 5 PERIOD WEDNESDAY INTO
WEDNESDAY NIGHT, MOIST ONSHORE FLOW INCREASES ACROSS WESTERN
PORTIONS OF WASHINGTON AND OREGON WITH THE POTENTIAL FOR 1 TO 2
INCHES OF RAINFALL ACROSS THE WEST-FACING TERRAIN, BUT THE
INTENSITY IS ALSO EXPECTED TO BE LIMITED HERE, SO NO EXCESSIVE
RAINFALL HEADLINES ARE WARRANTED AT THIS TIME.
DEPENDING ON THE POTENTIAL EVOLUTION OF AN OFFSHORE LOW AROUND
MIDWEEK, SOME MOISTURE IS EXPECTED TO BE ADVECTED INLAND ACROSS
COASTAL PORTIONS OF THE NORTHEAST U.S., WITH RAIN FOR THE BIG
CITIES AND PERHAPS SOME SNOW FOR THE HIGHER INLAND TERRAIN. SOME
LAKE EFFECT SNOW COULD ALSO MAKE HEADLINES FROM MICHIGAN TO
UPSTATE NEW YORK AS A STRONG SURGE OF COLD AIR ADVECTION RUSHES
ACROSS THE WARMER LAKE WATERS, WITH A FEW INCHES OF ACCUMULATION
POSSIBLE FOR SOME AREAS. LOOKING AHEAD TO THE END OF THE WEEK,
SHOWERS AND MOUNTAIN SNOW IS LIKELY TO MAKE A RETURN FROM
WASHINGTON TO THE NORTHERN ROCKIES, WITH SOME HEAVY SNOW LIKELY
FOR THE HIGHER MOUNTAIN RANGES.
THE COLD AIRMASS USHERED IN BY THE STRONG COLD FRONT ENGULFS ALL
OF THE CENTRAL AND EASTERN U.S., BY TUESDAY, AND THEN COOLER
WEATHER RETURNS TO THE FLORIDA PENINSULA BY WEDNESDAY. WIDESPREAD
ANOMALIES ON THE ORDER OF 15 TO 25 DEGREES BELOW AVERAGE FOR THIS
TIME OF YEAR ARE EXPECTED FROM THE WESTERN HIGH PLAINS TO THE OHIO
VALLEY, AND THEN THE EAST COAST GETS THE COLDEST WEATHER OF THE
WEEK ON THE FIRST DAY OF NOVEMBER ON WEDNESDAY. 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 AS A
MORE ZONAL FLOW PATTERN EVOLVES.
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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