934
FXUS02 KWBC 250701
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST SAT NOV 25 2023
VALID 12Z TUE NOV 28 2023 - 12Z SAT DEC 02 2023
..OVERVIEW
AN UPPER LOW OVER/NEAR HUDSON BAY WILL ALLOW FOR GENERAL TROUGHING
WITH SOME EMBEDDED SHORTWAVES TUES-THURS ACROSS THE GREAT LAKES
AND NORTHEAST. THIS PATTERN WOULD SUPPORT A MULTI-DAY PERIOD OF
ENHANCED LAKE EFFECT SNOWS, ONGOING FROM THE END OF THE SHORT
RANGE PERIOD, LOCALLY HEAVY AT TIMES. AN INITIAL RIDGE OVER THE
WEST ON TUESDAY SHOULD BE REPLACED BY MEAN TROUGHING AS A CLOSED
LOW DROPS INTO THE SOUTHWEST WITH A REINFORCING AMPLIFIED
SHORTWAVE/ADDITIONAL EMBEDDED LOW FRIDAY-SATURDAY. THIS SHOULD
PROMOTE RIDGE BUILDING DOWNSTREAM ACROSS THE SOUTHEAST AND
EVENTUALLY THE EAST COAST BY NEXT WEEKEND. MUCH OF NEXT WEEK
SHOULD BE RELATIVELY QUIET AND DRY, WITH THE EXCEPTION OF THE
GREAT LAKES AND INCREASED MOISTURE AND PRECIPITATION MOVING INTO
THE SOUTH-CENTRAL U.S. BY LATE IN THE WEEK.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
WHILE THE MODELS ON THE SYNOPTIC SCALE SHOW RELATIVELY GOOD
AGREEMENT, AT LEAST THE FIRST HALF OF THE PERIOD, THERE IS STILL
LOWER CONFIDENCE THAN DESIRED IN THE DETAILS OF INDIVIDUAL
SHORTWAVES THROUGH THE GREAT LAKES/NORTHEAST AFFECTING FRONTAL AND
SURFACE WAVE POSITIONS. OUT WEST, THERE ARE SOME PLACEMENT
DIFFERENCES WITH THE INTITIAL UPPER LOW MOVING INTO THE WEST
WEDNESDAY-THURSDAY AND THEN TIMING/STRENGTH OF THE ENERGY THROUGH
THE MID-SOUTH LATER IN THE WEEK (WITH IMPLICATIONS FOR POSSIBLE
LATE PERIOD HEAVY RAINFALL ACROSS THE LOWER MISSISSIPPI VALLEY AND
GULF COAST). GREATER UNCERTAINTY ARISES WITH ADDITIONAL SHARPER
SHORTWAVE ENERGY TOWARDS THE PACIFIC NORTHWEST THURSDAY-FRIDAY,
WHICH SOME GUIDANCE SHOWS ANOTHER UPPER LOW CLOSING OFF NEAR
CALIFORNIA BEFORE IT SLIDES INLAND. THIS SHOULD GENERALLY ACT TO
AMPLIFY TROUGHING FURTHER ACROSS THE WEST LATE PERIOD, BUT THERE
IS STILL CONSIDERABLE UNCERTAINTY IN THE TIMING AND DETAILS.
THE WPC BLEND FOR TONIGHT WAS ABLE TO UTILIZE A PURELY
DETERMINISITIC MODEL BLEND (BETWEEN THE ECMWF, GFS, AND
UKMET...THE CMC WAS TOO SHARP WITH A SHORTWAVE THROUGH THE GREAT
LAKES EARLY ON) DAYS 3-5. AFTER THAT, BLENDED IN INCREASING
AMOUNTS OF THE ENSEMBLE MEANS TO SMOOTH OUT DIFFERENCES OUT WEST
LATE PERIOD. GENERALLY THIS MAINTAINED GOOD CONTINUITY WITH THE
PREVIOUS WPC FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
FAVORABLE WESTERLY COLD FLOW OVER THE STILL RELATIVELY WARM GREAT
LAKES WILL CONTINUE TO PROMOTE A MULTI-DAY PERIOD OF ACCUMULATING
LAKE EFFECT SNOW ESPECIALLY DOWNWIND OF LAKES ERIE AND ONTARIO,
WITH THE BEST CHANCE FOR POSSIBLY HEAVY TOTALS ON TUESDAY. MODELS
SHOW AGREEMENT ON A FAVORABLE LAKE EFFECT EVENT MONDAY INTO
TUESDAY (AND POSSIBLE ADDITIONAL BEYOND), BUT GIVEN THE SMALL
SCALE OF THE HEAVY SNOWBANDS, MINOR SHIFTS IN LOCATION OF THE
BANDS WOULD PROVIDE CONSIDERABLY DIFFERENT CONDITIONS AND
ACCUMULATIONS OVER SLIGHTLY DIFFERENT AREAS. ELSEWHERE ACROSS THE
COUNTRY, CONDITIONS LOOK MOSTLY DRY THROUGH NEXT WEEK THOUGH SOME
LIGHT PRECIPITATION MAY ACCOMPANY A SHORTWAVE INTO THE WEST AROUND
MIDWEEK. PRECIPITATION CHANCES ALONG THE GULF COAST REGION TO
PERHAPS AS FAR NORTH AS THE MIDDLE MISSISSIPPI VALLEY LOOK TO
INCREASE AGAIN BY LATE WEEK AS A WARM FRONT LIFTS NORTHWARD
THROUGH THE GULF OF MEXICO BRINGING POSSIBLY AT LEAST LOCALLY
HEAVY RAINFALL.
MUCH OF THE SOUTH-CENTRAL TO EASTERN U.S. SHOULD SEE NEAR TO BELOW
NORMAL TEMPERATURES THROUGH THE FIRST HALF OF NEXT WEEK WITH
DECENT COVERAGE OF HIGHS AND LOWS 10-15F BELOW CLIMATOLOGY. THE
WEST-CENTRAL U.S. SHOULD BE MODERATING BACK TOWARD NORMAL MID WEEK
WITH THE INTERIOR WEST COOLING BACK DOWN DURING THE LATTER HALF OF
THE WEEK DUE TO TROUGHING ALOFT. AN EXCEPTION TO THE BELOW AVERAGE
TEMPERATURES MAY BE ACROSS THE NORTHERN PLAINS, WHERE BY TUESDAY
AND BEYOND LOWS IN THE 20S AND HIGHS IN THE 40S ARE EXPECTED,
WHICH ARE AROUND 5-15F ABOVE NORMAL. BY THURSDAY AND ESPECIALLY
FRIDAY, SOUTHERLY FLOW OFF THE WARM GULF OF MEXICO LOOKS TO RAMP
UP AND INCREASE TEMPERATURES, ESPECIALLY LOWS, IN THE
SOUTH-CENTRAL U.S. LOWS OF A FEW DEGREES ABOVE AVERAGE AND HIGHS
NEAR AVERAGE IN FLORIDA ON MONDAY ARE LIKELY TO COOL
TUESDAY-WEDNESDAY AFTER A FRONTAL PASSAGE, BEFORE SLOWLY
REBOUNDING.
TATE/SANTORELLI
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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