783
FXUS02 KWBC 300649
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
149 AM EST SAT NOV 30 2024
VALID 12Z TUE DEC 03 2024 - 12Z SAT DEC 07 2024
..CENTRAL/EAST U.S. ARCTIC COLD MODERATES/RENEWS NEXT WEEK
..SIGNIFICANT GREAT LAKE EFFECT SNOWS CONTINUE NEXT WEEK
..OVERVIEW
AN ANCHORING MEAN UPPER TROUGH WILL ENCOMPASS MUCH OF THE CENTRAL
TO EASTERN UNITED STATES NEXT WEEK, WITH ONLY A VERY GRADUAL SHIFT
EAST OVER TIME. THIS PATTERN WITH WEST/NORTHWEST WINDS WILL BE
FAVORABLE FOR CONTINUED LONG DURATION GREAT LAKE EFFECT TO
NORTHEAST TERRAIN FOCUSING SNOWS. SOME SNOWFALL ACCUMULATIONS WILL
BE SIGNIFICANT IN FAVORED LOCATIONS TO THE LEE OF THE GREAT LAKES.
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. THERE WILL BE PERIODS OF
TEMPORARY MODERATION BETWEEN COLD AIR SURGES AND MODERATE RETURN
FLOW FROM THE GULF OF MEXICO WILL BRING ENHANCED RAINFALL CHANCES
FROM TEXAS THROUGH THE CENTRAL GULF COAST STATES. MEANWHILE, BENIGN
WEATHER AND GRADUALLY WARMING TEMPERATURES ARE FORECAST FOR MUCH
OF THE WEST, ALBEIT WITH ENHANCED SHOWERS BEST ABLE TO REACH THE
PACIFIC NORTHWEST NEXT WEEKEND WITH CLOSER PACIFIC SYSTEM APPROACH.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS AND ENSEMBLES NOW SHOW GOOD AGREEMENT AND AS A RESULT
HIGHER CONFIDENCE IN THE OVERALL MID-LARGE SCALE PATTERN THROUGH
NEXT WEEK. ESPECIALLY MID TO LATE PERIOD THOUGH, THERE ARE SOME
SMALLER SCALE DIFFERENCES PARTICULARLY WITH SHORTWAVES WORKING TO
REINFORCE EASTERN U.S. TROUGHING AND THE SPECIFICS/FRONTAL TIMING
OF A MORE DEFINED SURFACE LOW/SYSTEM THROUGH THE GREAT LAKES.
UNCERTAINTY HAS SLOWLY DECREASED WITH THE TIMING/ORIENTATION OF A
SLOW MOVING SOUTHERN STREAM ELONGATED TROUGH/CLOSED LOW NEAR THE
SOUTHWEST U.S. WHICH HAS IMPLICATIONS FOR RAINFALL AMOUNTS ACROSS
SOUTH-SOUTHEAST TEXAS MUCH OF THE WEEK THAT GRADUALLY SPREADS OVER
THE CENTRAL GULF COAST STATES. OVERALL, THE WPC PROGS FOR NEXT WEEK
WERE MAINLY DERIVED FROM A BROAD COMPOSITE MODEL AND ENSEMBLE MEAN
BLEND AND COMPATIBLE NATIONAL BLEND OF MODELS. THIS MAINTAINS GOOD
CONTINUITY WITH THE PREVIOUS WPC FORECAST SUITE AS WELL AN LATEST
00 UTC CYCLE GUIDANCE, FURTHER BOLSTERING FORECAST CONFIDENCE.
..WEATHER/HAZARDS HIGHLIGHTS
A HIGHLY FAVORABLE PATTERN FOR GREAT LAKE EFFECT SNOW WILL PERSIST
WELL 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 WILL SEE SIGNIFICANT ACCUMULATIONS, LIKELY
CAUSING TRAVEL DISRUPTIONS TO INCLUDE I-90 BETWEEN CLEVELAND AND
BUFFALO AND I-81 NORTH OF SYRACUSE. SHORTWAVES AND FRONTAL SYSTEMS
MAY ALSO SUPPORT PERIODS WITH ADDITIONAL LIGHT TO MODERATE SNOWS
THAT COULD COVER A BROADER AREA FROM THE NORTH-CENTRAL APPALACHIANS
THROUGH FAVORED TERRAIN OF THE NORTHEAST.
MUCH OF THE REST OF THE COUNTRY CAN EXPECT MAINLY DRY CONDITIONS
NEXT WEEK, BUT THERE ARE EXCEPTIONS. RETURN FLOW OF MOISTURE COULD
START TO COME INTO THE WESTERN GULF COAST REGION BY EARLY NEXT
WEEK TO FUEL SOME ENHANCED RAINFALL. THIS LOOKS TO BE SLOW TO
SPREAD ACROSS THE CENTRAL GULF COAST REGION INTO MID-LATER NEXT
WEEK. AT THIS POINT, RAINFALL AMOUNTS ARE NOT HIGH ENOUGH TO
WARRANT EVEN A MARGINAL RISK ON THE WPC DAYS 4 AND 5 EXCESSIVE
RAINFALL OUTLOOKS, BUT THIS CAN CONTINUED TO BE MONITORED GIVEN
ANOMALOUS MOISTURE AND MODEST INSTABILITY. INITIAL UPPER RIDGING
WILL KEEP THE WEST MAINLY DRY, BUT ENHANCED PRECIPITATION CHANCES
GRADUALLY INCREASE FOR THE PACIFIC NORTHWEST BY NEXT WEEKEND
PENDING VARIANCE WITH EXTENT/TIMING OF PACIFIC SYSTEM APPROACH.
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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