594
FXUS02 KWBC 290658
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 AM EST FRI NOV 29 2024
VALID 12Z MON DEC 02 2024 - 12Z FRI DEC 06 2024
..CENTRAL/EAST ARCTIC COLD MAY MODERATE THEN RENEW NEXT WEEK
..SIGNIFICANT GREAT LAKE EFFECT SNOWS CONTINUE INTO NEXT WEEK
..OVERVIEW
A LARGE SCALE UPPER TROUGH IS EXPECTED TO ENCOMPASS MUCH OF THE
CENTRAL TO EASTERN UNITED STATES NEXT WEEK, WITH ONLY A VERY
GRADUAL SHIFT EAST AND WEAKENING OVER TIME. THIS PATTERN WITH
WEST/NORTHWEST WINDS WILL BE FAVORABLE FOR CONTINUED LONG DURATION
LAKE EFFECT FOCUSING SNOWS. SOME OF THE SNOWFALL ACCUMULATIONS
COULD BE SIGNIFICANT IN FAVORED TO THE LEE LOCATIONS. THE
PERIODICALLY REINFORCED TROUGH ALOFT AND COLD SURFACE HIGH PRESSURE
ORIGINALLY STEMMING FROM THE ARCTIC WILL CAUSE CONTINUED COLDER
THAN AVERAGE TEMPERATURES MIGRATING FAR SOUTHWARD ACROSS CENTRAL
AND EASTERN PARTS OF THE COUNTRY, ALBEIT LIKELY TO OFFER SOME
MODERATION OVER TIME AS RETURN INFLOW FROM THE GULF OF MEXICO ALSO
BRINGS SOME ENHANCED RAINFALL CHANCES TO TEXAS AND LOUSIANA WITH
SYSTEM GENESIS. MEANWHILE, BENIGN WEATHER AND GRADUALLY WARMING
TEMPERATURES ARE FORECAST FOR THE WEST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL AND ENSEMBLE FORECAST SPREAD AND UNCERTAINTY SEEM LOWER THAN
NORMAL FOR THE PERIOD FROM MONDAY THROUGH WEDNESDAY, BOLSTERING
CONFIDENCE. A FAVORED COMPOSITE OF BEST CLUSTERED GUIDANCE FROM
THE 18 UTC GFS AND 12 UTC ECMWF/CANADIAN ALONG WITH THE 01 UTC
NATIONAL BLEND OF MODELS (NBM) PROVIDES A SOLID BASIS THAT ENJOYS
GREAT ENSEMBLE SUPPORT AND CONTINUITY. FORECAST SPREAD GRADUALLY
INCREASES INTO LATER NEXT WEEK WITH THE HANDLING OF SOUTHERN STREAM
UPPER TROUGH/LOW PROGRESSION INLAND AS WELL AS WITH EMBEDDED
SYSTEM DETAILS AND RESULTING MAIN UPPER TROUGH AMPLITUDE VARIANCES
OVER THE EAST-CENTRAL STATES. PREFERRED A COMPOSITE OF COMPATIBLE
GEFS/ECMWF/CANADIAN ENSEMBLE MEANS AND THE NBM FOR MAX PRODUCT
CONTINUITY ON THE AMPLIFIED SIDE OF SOLUTIONS GIVEN UPSTREAM
FLOW. LATEST 00 UTC MODELS HAVE FAVORABLY TRENDED MORE IN LINE.
..WEATHER/HAZARDS HIGHLIGHTS
IT GENERALLY REMAINS THE CASE THAT A PRONOUNCED UPPER TROUGH AND A
COLD SURFACE HIGH WILL REMAIN IN PLACE INTO NEXT WEEK AND PRODUCE
SOME CONTINUED COLD WEATHER THAT COULD BE DANGEROUS IN THE NORTHERN
PLAINS. THE COLD IS FORECAST TO GRADUALLY MODERATE COMPARED TO THE
SHORT RANGE PERIOD, BUT REMAIN BELOW NORMAL BY 15-20F MONDAY IN
THE NORTHERN PLAINS AS LOWS WILL BE IN THE NEGATIVE SINGLE DIGITS
WITH HIGHS IN THE LOW 10S. MEANWHILE THE COLD AIR MASS WILL SPREAD
FARTHER SOUTHEAST IN MODERATED FORM, ACROSS THE MISSISSIPPI VALLEY,
OHIO/TENNESSEE VALLEYS, AND INTO THE APPALACHIANS AND EASTERN
SEABOARD. A HANDFUL OF RECORD LOW MAX AND MIN TEMPERATURES ARE
POSSIBLE ACROSS THE OHIO VALLEY INTO THE APPALACHIANS, WHERE
TEMPERATURES ARE FORECAST TO BE AROUND 15-20F BELOW AVERAGE AND
STAY BELOW FREEZING FOR HIGHS IN MANY AREAS MONDAY-TUESDAY. BY
MIDWEEK, THE COLD SHOULD BE GRADUALLY LESSENING IN SCOPE AND
MAGNITUDE, BECOMING MORE LIMITED TO THE EAST WEDNESDAY, BUT
ADDITIONAL COLD AIR MAY SURGE IN FROM CANADA INTO LATER NEXT WEEK.
MEANWHILE ABOVE AVERAGE TEMPERATURES ARE FORECAST TO SPREAD ACROSS
THE WEST AND REACH THE PLAINS INTO MID-LATER NEXT WEEK.
A FAVORABLE PATTERN FOR GREAT LAKE EFFECT SNOW WILL PERSIST INTO NEXT
WEEK. EXACT SNOW AXES AND LOCAL INTENSITIES WILL DEPEND ON
REINFORCING SYSTEM PASSAGES WITH WIND DIRECTIONS THAT COULD VARY
FROM NORTHWEST TO WEST DAY TO DAY, BUT SOME AREAS DOWNWIND OF THE
LAKES COULD SEE SIGNIFICANT ACCUMULATIONS, LIKELY CAUSING TRAVEL
DISRUPTIONS ON I-90 BETWEEN CLEVELAND AND BUFFALO AND I-81 NORTH OF
SYRACUSE. LATER, SHORTWAVES AND FRONTAL SYSTEMS MAY COME THROUGH
THE GREAT LAKES REGION FOR SOME ADDITIONAL LIGHT SNOW THAT COULD
COVER A BROADER AREA.
MUCH OF THE REST OF THE COUNTRY CAN EXPECT MAINLY DRY CONDITIONS
NEXT WEEK. RETURN FLOW OF MOISTURE COULD START TO COME INTO THE
WESTERN GULF COAST REGION BY EARLY NEXT WEEK TO FUEL SOME ENHANCED
RAINFALL, WHICH LOOKS TO BE SLOW TO SPREAD ACROSS THE LOWER
MISSISSIPPI VALLEY AND VICINITY INTO MID-LATER NEXT WEEK. INITIAL
UPPER RIDGING WILL KEEP THE WEST MAINLTY DRY, BUT PRECIPITATION
CHANCES MAY GRADUALLY INCREASE INTO THE PACIFIC NORTHWEST LATER
NEXT WEEK, BUT ASSOCIATED PACIFIC SYSTEM APPROACH TRENDED SLOWER.
SCHICHTEL
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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