609
FXUS02 KWBC 281756
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1256 PM EST THU NOV 28 2024
VALID 12Z SUN DEC 01 2024 - 12Z THU DEC 05 2024
..ARCTIC COLD GRADUALLY MODERATING AS IT PUSHES EAST NEXT WEEK
..LAKE EFFECT SNOW LIKELY TO CONTINUE INTO NEXT WEEK
..OVERVIEW
A LARGE SCALE UPPER TROUGH IS EXPECTED TO ENCOMPASS MUCH OF THE
CENTRAL TO EASTERN UNITED STATES AT THE START OF THE PERIOD SUNDAY,
WITH SOME VERY GRADUAL SHIFT EAST AND WEAKENING AS NEXT WEEK
PROGRESSES. THIS PATTERN WITH WEST/NORTHWEST WINDS WILL BE
FAVORABLE FOR CONTINUED LONG DURATION LAKE EFFECT SNOW. SOME OF THE
SNOWFALL ACCUMULATIONS COULD BE SIGNIFICANT IN FAVORED LOCATIONS.
THE PERIODICALLY REINFORCED TROUGH ALOFT AND COLD SURFACE HIGH
PRESSURE ORIGINALLY STEMMING FROM THE ARCTIC WILL CAUSE CONTINUED
COLDER THAN AVERAGE TEMPERATURES MIGRATING ACROSS CENTRAL AND
EASTERN PARTS OF THE COUNTRY. MEANWHILE BENIGN WEATHER AND
GRADUALLY WARMING TEMPERATURES ARE FORECAST FOR THE WEST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT ON THE LARGE SCALE
EASTERN TROUGH/WESTERN RIDGE PATTERN. THERE IS SOME SIGNAL FOR THE
EASTERN TROUGH TO GRADUALLY LIFT OUT OF THE SOUTHEAST, BUT
PERIODIC SHORTWAVES DOWN THE WESTERN SIDE OF THE TROUGH WILL KEEP
IT GENERALLY ANCHORED OVER THE OHIO VALLEY-NORTHEAST WELL INTO NEXT
WEEK. THESE SHORTWAVES PROVIDE UNCERTAINTY IN THE DETAILS OF THE
FORECAST WHICH HAVE IMPLICATIONS ON FRONTAL PLACEMENT AND SENSIBLE
WEATHER. OUT WEST, GUIDANCE AGREES STRONG RIDGING WILL HOLD OVER
THE PACIFIC NORTHWEST AS A SOUTHERN STREAM TROUGH/EMBEDDED UPPER
LOW MEANDERS NEAR THE SOUTHWEST. THE CMC IS A LITTLE BIT MORE
AGGRESSIVE WITH A SHORTWAVE INTO THE NORTHWEST NEXT THURSDAY/DAY 7,
WHICH SHIFTS THE ENTIRE PATTERN EASTWARD A LITTLE QUICKER THAN
CONSENSUS. THE UPDATED FORECAST FROM WPC TODAY USED A GENERAL MODEL
BLEND THROUGH DAY 5, INCREASING ENSEMBLE MEANS BY DAY 6 AND 7, AND
LESSER INCORPORATION OF THE CMC. THIS MAINTAINED GOOD AGREEMENT
WITH THE PREVIOUS WPC FORECAST AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
THE PRONOUNCED UPPER TROUGH AND A COLD SURFACE HIGH WILL REMAIN IN
PLACE INTO EARLY 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 SUNDAY-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 SUNDAY-TUESDAY. BY
MIDWEEK THE COLD SHOULD BE GRADUALLY LESSENING IN SCOPE AND
MAGNITUDE, BECOMING MORE LIMITED TO THE EAST WEDNESDAY AND
NORTHEAST THURSDAY WITH TEMPERATURES THAT ARE BELOW NORMAL BY
AROUND 5-10 DEGREES. MEANWHILE ABOVE AVERAGE TEMPERATURES ARE
FORECAST TO SPREAD ACROSS THE WEST AND REACH THE PLAINS BY
WEDNESDAY-THURSDAY.
A FAVORABLE PATTERN FOR LAKE EFFECT SNOW WILL PERSIST INTO EARLY
NEXT WEEK. EXACT SNOW AXES WILL DEPEND ON WIND DIRECTIONS THAT
COULD VARY FROM NORTHWEST TO WEST DAY TO DAY, BUT SOME AREAS
DOWNWIND OF THE LAKES COULD SEE SIGNIFICANT ACCUMULATIONS DURING
LATE THIS WEEK TO EARLY NEXT WEEK, LIKELY CAUSING TRAVEL
DISRUPTIONS ON I-90 BETWEEN CLEVELAND AND BUFFALO AND I-81 NORTH OF
SYRACUSE. CLOSER TO MIDWEEK, 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 GENERALLY DRY
CONDITIONS NEXT WEEK. RETURN FLOW OF MOISTURE COULD START TO COME
INTO THE WESTERN GULF COAST REGION BY EARLY NEXT WEEK FOR SOME
SHOWER ACTIVITY, WHICH LOOKS TO SPREAD ACROSS THE SOUTH-CENTRAL
U.S. MONDAY-WEDNESDAY. INITIAL NORTHERN STREAM RIDGING WILL KEEP
THE WEST DRY FOR THE MOST PART, BUT PRECIPITATION CHANCES SHOULD
GRADUALLY INCREASE IN THE PACIFIC NORTHWEST AS NEXT WEEK
PROGRESSES.
SANTORELLI/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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