234
FXUS02 KWBC 280656
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
156 AM EST TUE JAN 28 2025
VALID 12Z FRI JAN 31 2025 - 12Z TUE FEB 04 2025
..GENERAL OVERVIEW
THE FORECAST PERIOD BEGINS FRIDAY WITH A CLOSED UPPER LOW TRACKING
EASTWARD FROM THE CENTRAL PLAINS AND EVOLVING INTO AN OPEN WAVE AS
IT REACHES THE EAST COAST SATURDAY MORNING. THIS IS EXPECTED TO
FUEL THE DEVELOPMENT OF WIDESPREAD RAIN AND SOME THUNDERSTORMS
FROM THE CENTRAL GULF COAST TO THE MID-ATLANTIC AND SOUTHERN NEW
ENGLAND. A COUPLE ROUNDS OF SNOW ARE POSSIBLE ACROSS THE NORTHERN
TIER THROUGH THE PERIOD. BACK ACROSS THE PACIFIC NORTHWEST, A COLD
FRONT AND ASSOCIATED MOISTURE FEED AHEAD OF IT WILL LEAD TO THE
RETURN OF RAIN AND MOUNTAIN SNOW BY FRIDAY AND CONTINUING INTO THE
WEEKEND. MOST OF THE COUNTRY WILL HAVE NEAR OR ABOVE NORMAL
TEMPERATURES THROUGH THE PERIOD, UNTIL EARLY NEXT WEEK WHEN AN
ARCTIC AIRMASS SETTLES ACROSS THE NORTHERN PLAINS AND MIDWEST
BEHIND A STRONG COLD FRONT.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 18/00Z MODEL GUIDANCE SUITE IS IN GOOD SYNOPTIC SCALE
AGREEMENT ACROSS THE COUNTRY FOR THE END OF THE WEEK. HOWEVER THERE
WERE SOME MORE TIMING DIFFERENCES OBSERVED WITH THE CMC AND UKMET
SOLUTIONS, SO THE MODEL BLEND WAS WEIGHTED MORE TOWARDS THE
GFS/ECMWF TO START. GIVEN THE TRANSITION TO A MORE ZONAL FLOW
PATTERN ALOFT BY SUNDAY, THE GUIDANCE DIFFERS MORE WITH TIMING AND
MAGNITUDE OF FEATURES IN THE NORTHERN STREAM FLOW, AND THE ARRIVAL
OF THE ARCTIC FRONT ACROSS THE NORTHERN PLAINS. THE FORECAST BLEND
TRANSITIONED TO ABOUT 50% ENSEMBLE MEANS BY EARLY NEXT WEEK TO
ACCOUNT FOR THE INCREASING MODEL UNCERTAINTY.
..WEATHER/HAZARDS HIGHLIGHTS
AN OCCLUDED LOW PRESSURE SYSTEM IS FORECAST TO MOVE ACROSS MISSOURI
AND THEN OVER THE OHIO VALLEY BY FRIDAY MORNING. IN THE WARM
SECTOR OF THE SURFACE LOW, WARM AIR ADVECTION IN COMBINATION WITH
STRONG FORCING ALOFT WILL CREATE A FAVORABLE ENVIRONMENT FOR HEAVY
RAINFALL FROM THE PANHANDLE OF FLORIDA TO THE SOUTHERN APPALACHIANS.
THERE WILL LIKELY BE A CORRIDOR OF RAINFALL TOTALS APPROACHING ONE
INCH ACROSS PORTIONS OF THIS REGION, AND THERE COULD BE THE
POTENTIAL FOR SOME TRAINING/REPEATED CONVECTION AHEAD OF THE
TRAILING COLD FRONT, ALBEIT LESS INTENSE THAN WHAT IS EXPECTED ON
THURSDAY. THE NEW DAY 4 OUTLOOK HAS A SMALLER MARGINAL RISK AREA
COMPARED TO THE PREVIOUS DAY 5 OUTLOOK OWING TO A FASTER STORM
SYSTEM, AND IF QPF TRENDS LOWER IN FUTURE FORECASTS, IT'S POSSIBLE
THIS RISK AREA MAY EVENTUALLY BE DROPPED. MEANWHILE WITH THIS
SYSTEM, PRECIPITATION WILL LIKELY BE IN THE FORM OF SNOW OR A
WINTRY MIX ON THE NORTHERN EDGE. CURRENT FORECASTS SHOW THE
POTENTIAL FOR WINTER WEATHER TO LINGER ACROSS UPSTATE NEW YORK TO
INTERIOR NEW ENGLAND THROUGH SATURDAY MORNING. ANOTHER ROUND OF
WINTER WEATHER COULD TRACK ACROSS THE GREAT LAKES TO THE NORTHEAST
ON SUNDAY WITH A CLIPPER TYPE SYSTEM.
MOIST INFLOW IS FORECAST TO RETURN TO THE WEST COAST LATE THIS
WEEK, EXPANDING INTO THE NORTHERN GREAT BASIN/ROCKIES, WITH ROUNDS
OF LOW PRESSURE/FRONTAL SYSTEMS TRACKING THROUGH THE REGION.
AN ATMOSPHERIC RIVER EVENT IS BECOMING MORE LIKELY FOR THE FRIDAY-
SATURDAY TIME PERIOD FROM NORTHERN CALIFORNIA TO THE OLYMPIC
PENINSULA. A DAY 4 MARGINAL RISK WILL BE VALID FOR THE COASTAL
RANGES AND THE FOOTHILLS OF THE OREGON CASCADES, AND A DAY 5
MARGINAL A LITTLE FARTHER TO THE SOUTH TO INCLUDE MORE OF NORTHERN
CALIFORNIA AND EXTENDING INTO SOUTHWESTERN OREGON, WITH THE
HEAVIEST RAINFALL LIKELY TO FALL ON SATURDAY. THERE IS THE
POTENTIAL THAT A SLIGHT RISK MAY EVENTUALLY BE NEEDED IN FUTURE
OUTLOOKS FOR PORTIONS OF NORTHWESTERN CALIFORNIA.
TEMPERATURES ARE EXPECTED TO BE ABOVE AVERAGE TO CLOSE OUT THE
WEEK FOR THIS TIME OF YEAR ACROSS MUCH OF THE CENTRAL AND EASTERN
U.S., WITH HIGHS RUNNING ABOUT 5-15 DEGREES ABOVE AVERAGE IN MOST
CASES. THIS ALSO HOLDS TRUE GOING INTO THE WEEKEND, ALTHOUGH NEW
ENGLAND AND THE MID-ATLANTIC REGION LIKELY REMAIN CLOSER TO
SEASONAL AVERAGES. THE NEXT ROUND OF ARCTIC COLD ARRIVES ACROSS
MONTANA ON SUNDAY AND EXTENDS INTO THE DAKOTAS BY MONDAY, WITH
HIGHS POTENTIALLY 15-25 DEGREE BELOW AVERAGE IN MANY CASES. COLDER
WEATHER THEN ENCOMPASSES MORE OF THE CENTRAL AND NORTHERN U.S.
GOING INTO TUESDAY.
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 (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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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