335
FXUS02 KWBC 281844
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
244 PM EDT SAT OCT 28 2023
VALID 12Z TUE OCT 31 2023 - 12Z SAT NOV 04 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
THE UPPER LEVEL PATTERN AT THE START OF THE PERIOD (TUESDAY) IS
EXPECTED TO FEATURE A STRONG EMBEDDED SHORTWAVE OVER THE UPPER
MIDWEST WITHIN THE BROAD TROUGHING ADVANCING THROUGH THE CENTRAL
U.S.. THE STRENGTH AND AMPLITUDE OF THAT FEATURE AS IT REACHES THE
OHIO VALLEY AND EASTERN U.S. REMAINS VERY UNCERTAIN WITH RATHER
LARGE SPREAD BETWEEN THE GFS AND NON-NCEP GUIDANCE. THE GFS
SOLUTION ADVERTISES A WEAKER SHORTWAVE THAT PASSES QUICKLY THROUGH
THE CENTRAL/EASTERN U.S. AND RESULTS IN AN OFFSHORE LOW WELL AWAY
FROM THE NORTHEAST COAST WHILE HIGH PRESSURE QUICKLY OVERTAKES THE
REGION IN ITS WAKE. MEANWHILE, THE ECMWF AND OTHER NON-NCEP
GUIDANCE SHOWS A BIT SLOWER SOLUTION, WITH A MORE AMPLIFIED
SHORTWAVE THAT INDUCES LOW PRESSURE CLOSER TO THE NORTHEAST COAST
ON WEDNESDAY. THE ENSEMBLE MEANS INCLUDING THE GEFS WOULD FAVOR
THE SLOWER SOLUTIONS, SO THE WPC BLEND INCLUDED HIGHER WEIGHTS OF
THE ECMWF/CMC/UKMET FOR DAY 3-5. ELSEWHERE, GUIDANCE HAS THE MORE
TYPICAL BIASES FOR THE UPCOMING PACIFIC NORTHWEST ATMOSPHERIC
RIVER EVENT FOR MID-WEEK WHERE A BLEND OF THE GFS/ECMWF AND THE
ENSEMBLE MEANS WAS USED.
..WEATHER/HAZARDS HIGHLIGHTS
THE MAIN WEATHER HIGHLIGHTS WILL BE THE ARRIVAL OF SOME OF THE
COLDEST AIR SO FAR THIS FALL ACROSS MUCH OF THE CENTRAL TO EASTERN
U.S., IN THE WAKE OF A STRONG COLD FRONT AND AS HIGH PRESSURE
SETTLES OVER THE CENTRAL TO EASTERN UNITED STATES. HIGH
TEMPERATURES TUESDAY AND WEDNESDAY WILL BE 10 TO NEAR 25 DEGREES
BELOW NORMAL ACROSS MUCH OF THE CENTRAL U.S. AND UPWARDS OF 10
DEGREES BELOW NORMAL FOR THE CAROLINAS NORTHWARD THROUGH NEW
ENGLAND. THE ONLY WARM AND ABOVE NORMAL SPOTS WILL BE ACROSS THE
FLORIDA PENINSULA AS WELL AS PORTIONS OF SOUTHERN ARIZONA AND
PARTS OF CALIFORNIA. OVERNIGHT LOWS WILL BE SIMILARLY BELOW
NORMAL, WITH NEAR TO SUB FREEZING TEMPERATURES OVERSPREADING A
LARGE PORTION OF THE COUNTRY. IN FACT, WEDNESDAY AND THURSDAY
MORNING LOWS MAY DIP INTO THE UPPER 30S AS FAR SOUTH AS THE GULF
COAST FROM TEXAS THROUGH THE WESTERN FLORIDA PANHANDLE. FURTHER TO
THE NORTH ACROSS NORTHERN TEXAS THROUGH THE MID-MISSISSIPPI
VALLEY, NUMEROUS LOCATIONS MAY SET RECORD LOWS FOR WEDNESDAY
MORNING AS READINGS FALL WELL INTO THE 20S.
SOUTHERN STREAM ENERGY INTERACTING WITH AN APPROACHING SHORTWAVE
OUT OF THE GREAT LAKES MAY DEVELOP A COASTAL LOW OFF THE
MID-ATLANTIC/NORTHEAST LATE TUESDAY THROUGH WEDNESDAY. IF THE LOW
ENDS UP DEVELOPING CLOSER TO THE COAST, RAINFALL WILL BE MORE
WIDESPREAD ALONG THE COASTAL AREAS OF THE NORTHEAST BEFORE ENDING
LATER WEDNESDAY AND WEDNESDAY NIGHT. OTHERWISE, THE NEXT MAIN
PRECIPITATION EVENT WILL BE AN ATMOSPHERIC RIVER EVENT FOR THE
PACIFIC NORTHWEST LATE WEDNESDAY THROUGH THURSDAY WHERE WIDESPREAD
RAINFALL OF 1-2 INCHES WILL BE COMMON FOR THE WEST-FACING SLOPES
OF THE OLYMPICS AND CASCADES AND NORTHERN CALIFORNIA COASTAL
RANGES. 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 IN THE WAKE OF THE
COLD FRONT MID-WEEK, WITH A FEW INCHES OF ACCUMULATION POSSIBLE
FOR SOME AREAS.
TAYLOR
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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