128
FXUS02 KWBC 040659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST TUE FEB 4 2025
VALID 12Z FRI FEB 07 2025 - 12Z TUE FEB 11 2025
...POTENTIALLY HEAVY SNOW AND ICE ACROSS THE NORTHERN MID-ATLANTIC
AND NORTHEAST THIS WEEKEND...
..OVERVIEW
QUASI-ZONAL FLOW WITH EMBEDDED SHORTWAVES ACROSS THE LOWER 48 LATE
WEEK WILL TRANSITION TO A PATTERN WITH A POSITIVELY TILTED MEAN
TROUGH SETTING UP ACROSS THE INTERIOR WEST THIS WEEKEND INTO EARLY
NEXT WEEK, JUST DOWNSTREAM OF A HIGHLY AMPLIFIED PACIFIC THROUGH
ALASKA UPPER RIDGE. PRECIPITATION IS LIKELY TO SPREAD THROUGH THE
WEST FRIDAY BEFORE FINALLY TRENDING DRIER OVER THE WEEKEND. FARTHER
EAST, SNOW ACROSS THE NORTH-CENTRAL U.S. AND RAIN CENTERED IN THE
OHIO VALLEY ON FRIDAY WILL CONSOLIDATE INTO A LOW PRESSURE/FRONTAL
SYSTEM BRINGING POSSIBLE LOCALLY HEAVY RAIN TO THE OHIO
VALLEY/CENTRAL APPALACHIANS AND POSSIBLE HEAVY SNOW TO THE
NORTHEAST, ALONG WITH SOME FREEZING RAIN AND SLEET IN BETWEEN, FOR
THE WEEKEND. PRECIPITATION LOOKS TO REMAIN/GET RENEWED CENTERED
OVER THE TENNESSEE VALLEY INTO EARLY NEXT WEEK. TEMPERATURE-WISE,
BROAD AREAS OF WELL ABOVE NORMAL TEMPERATURES LATE THIS WEEK WILL
SHRINK IN SCOPE TO THE SOUTHEAST EARLY NEXT WEEK. MEANWHILE BELOW
AVERAGE TEMPERATURES IN THE NORTHWESTERN AND NORTH-CENTRAL U.S. ARE
FORECAST TO TREND EVEN COLDER INTO MONDAY-TUESDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
TONIGHT'S MODELS AND ENSEMBLES REMAIN FAIRLY AGREEABLE FOR THE
OVERALL PATTERN WITH TYPICAL SCATTER FOR INDIVIDUAL FEATURES AND
SHORTWAVE DETAILS. A QUICK-MOVING SHORTWAVE ALONG THE NORTHERN TIER
WILL DRAW A SURFACE LOW FROM THE SOUTH-CENTRAL PLAINS
NORTHEASTWARD OVER THE WEEKEND. BY EARLY SUNDAY, MODELS SHOW SOME
SPREAD WITH THE LOW TRACK, MADE MORE COMPLICATED BY POTENTIAL
SECONDARY LOW FORMATION JUST OFFSHORE WHILE THE ORIGINAL LOW TRACKS
NEAR/OVER THE LOWER GREAT LAKES. THE 18Z GFS FAVORED THE OFFSHORE
LOW FOR A MORE SUPPRESSED LOW TRACK. THE 12Z/NEWER 00Z GFS RUNS
WERE MORE AGREEABLE WITH OTHER GUIDANCE THAT THE GREAT LAKES LOW
WILL REMAIN THE PRIMARY LOW. HOWEVER, A SOLUTION LIKE THE 18Z GFS
CANNOT BE COMPLETELY RULED OUT ESPECIALLY BECAUSE A HANDFUL OF THE
AI/ML MODELS WERE SIMILAR. THE LOW TRACK HAS IMPLICATIONS FOR
WINTER WEATHER ACROSS THE NORTHEAST, BUT AT LEAST MODELS AGREE IN
THE EXISTENCE OF THE LOW ALBEIT WITH SOME TRACK DIFFERENCES.
THE PATTERN OF A WESTERN TROUGH WITH ITS AXIS TOWARD HUDSON BAY
THIS WEEKEND INTO EARLY NEXT WEEK HAS BROAD AGREEMENT, BUT ROUNDS
OF NORTHERN AND SOUTHERN STREAM ENERGY FEEDING INTO THE TROUGH ARE
MUCH MORE VARIABLE. THESE LOWER PREDICTABILITY FEATURES FAVOR USING
A MODEL/ENSEMBLE MEAN BLEND SO AS NOT TO FAVOR ANY PARTICULAR
INDIVIDUAL SOLUTION THAT COULD EASILY CHANGE WITH ITS NEXT RUN.
THE WPC FORECAST USED A MULTI-MODEL DETERMINISTIC BLEND OF THE 12Z
GUIDANCE EARLY IN THE FORECAST PERIOD, AND GRADUALLY INCREASED THE
PROPORTION OF GEFS AND EC ENSEMBLE MEANS TO NEAR/JUST OVER HALF BY
DAYS 6/7 AS SPREAD IN THE DETAILS INCREASED.
..WEATHER/HAZARDS HIGHLIGHTS
PRECIPITATION IS LIKELY TO CONTINUE IN THE WESTERN U.S. ON FRIDAY
AS A COUPLE OF LOW PRESSURE/FRONTAL SYSTEMS MOVE THROUGH. RAINFALL
MAGNITUDES WILL FINALLY LESSEN IN COASTAL CALIFORNIA, BUT FARTHER
INLAND SNOW WILL BE POSSIBLE ACROSS THE CASCADES/SIERRA NEVADA AND
FARTHER EAST ACROSS THE NORTHERN AND CENTRAL ROCKIES. BY THE
WEEKEND, MUCH LESS PRECIPITATION IS FORECAST FOR THE WEST, WITH
JUST SOME LIGHT AMOUNTS IN THE PACIFIC NORTHWEST AND PARTS OF THE
NORTHERN/CENTRAL ROCKIES. THE CENTRAL ROCKIES MAY SEE SOME HIGH
WINDS IN THE POST-FRONTAL PATTERN ON SATURDAY.
FARTHER EAST, SOME SNOW IS FORECAST TO SPREAD INTO THE DAKOTAS
FRIDAY AND INTO THE UPPER MIDWEST FRIDAY-SATURDAY TO THE NORTH OF
DEVELOPING LOW PRESSURE IN THE SOUTH-CENTRAL PLAINS. MEANWHILE
MOISTURE PRESENT ACROSS THE OHIO VALLEY AND VICINITY WILL LEAD TO
SOME LIGHT TO MODERATE RAIN FRIDAY. THEN AS THE SURFACE LOW TRACKS
NORTHEAST, MODERATE TO HEAVY SNOW IS FORECAST TO DEVELOP ACROSS THE
GREAT LAKES AND THE NORTHEASTERN U.S. ON SATURDAY. PROBABILITIES
OF PLOWABLE SNOW/SLEET CONTINUE TO INCREASE ACROSS THE NORTHERN
MID-ATLANTIC INTO THE NORTHEAST, ESPECIALLY IN HIGHER ELEVATIONS OF
THE CATSKILLS, ADIRONDACKS, AND BERKSHIRES. SLEET AND FREEZING
RAIN ARE ALSO A POSSIBILITY ACROSS PORTIONS OF THE MID-ATLANTIC,
NEW YORK, AND SOUTHERN NEW ENGLAND. TO THE SOUTHWEST, RAIN IS
LIKELY ACROSS THE OHIO VALLEY AND CENTRAL APPALACHIANS. POTENTIALLY
HEAVY RAIN BE MOST CONCERNING IN THE CENTRAL APPALACHIANS WHERE
THERE ARE WET ANTECEDENT CONDITIONS ALREADY, PLUS AMPLE RAINFALL IN
THE SHORT RANGE PERIOD. MULTIPLE ROUNDS OF RAIN ARE POSSIBLE DUE
TO CONVECTION WELL AHEAD AND THEN RAIN DIRECTLY AHEAD OF THE COLD
FRONT. THUS A MARGINAL RISK IS DELINEATED IN THE DAY 5/SATURDAY ERO
CENTERED IN WEST VIRGINIA. THE PATTERN WILL BE FAVORABLE FOR
PRECIPITATION ACROSS THE SOUTHERN HALF OF THE MISSISSIPPI VALLEY TO
TENNESSEE VALLEY AND SOUTHERN MID-ATLANTIC INTO EARLY NEXT WEEK.
SOME WINTRY WEATHER MAY BE POSSIBLE ON THE NORTHERN SIDE OF THE
PRECIPITATION SHIELD.
COLDER THAN AVERAGE TEMPERATURES ARE FORECAST FOR NORTHWESTERN AND
NORTH-CENTRAL PARTS OF THE LOWER 48 THROUGH THE PERIOD. THE COLD
WILL BE ESPECIALLY PRONOUNCED ACROSS MONTANA AND NORTH DAKOTA,
ESPECIALLY BY EARLY NEXT WEEK WHEN ANOTHER SURGE OF COLD AIR IS
LIKELY. BY MONDAY-TUESDAY, LOWS ARE FORECAST TO BE IN THE -10S AND
-20S, ALONG WITH SOME BELOW ZERO HIGHS. MEANWHILE, AREAS FROM THE
FOUR CORNERS STATES ACROSS THE SOUTH ARE EXPECTED TO SEE
UNSEASONABLE WARMTH AS HIGHS AND LOWS THAT ARE 20-30 DEGREES ABOVE
AVERAGE BECOME WIDESPREAD. THESE ANOMALIES COULD SET DAILY RECORDS.
EXACT TEMPERATURES/ANOMALIES VARY SOMEWHAT AT ANY PARTICULAR PLACE
FRIDAY-SATURDAY, BUT BY SUNDAY-MONDAY THERE SHOULD BE A MORE
PRONOUNCED COOLING TREND ACROSS THE FOUR CORNERS AND SOUTH-CENTRAL
U.S. TO THE MID-ATLANTIC BEHIND A STRONG COLD FRONT. BY TUESDAY
WARMER THAN AVERAGE TEMPERATURES SHOULD BE LIMITED TO THE CENTRAL
GULF COAST TO FLORIDA.
TATE
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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