387
FXUS02 KWBC 270659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST SUN NOV 27 2022
VALID 12Z WED NOV 30 2022 - 12Z SUN DEC 04 2022
...WET/SNOWY CONDITIONS EXPANDING ACROSS THE WEST WITH BELOW
NORMAL TEMPERATURES...
...HEAVY RAIN POSSIBLY REACHING INTO PARTS OF THE EAST BY
WEDNESDAY...
..OVERVIEW
MOST GUIDANCE CONTINUES TO SHOW A MEAN TROUGH ALOFT BECOMING
ESTABLISHED NEAR THE WEST COAST AND A RIDGE INITIALLY CENTERED
OVER WESTERN CUBA SETTLING OVER THE GULF OF MEXICO, WITH
WEST-SOUTHWESTERLY FLOW TENDING TO PREVAIL BETWEEN THESE TWO
FEATURES. THIS PATTERN SHOULD LEAD TO COOL DAYTIME TEMPERATURES TO
THE WEST OF THE ROCKIES ALONG WITH INCREASING COVERAGE OF RAIN AND
SNOW OVER THE WEST, WITH SOME OF THIS ACTIVITY POTENTIALLY HEAVY.
DAY-TO-DAY DETAILS OF INDIVIDUAL FEATURES WITHIN THE WEST COAST
UPPER TROUGH STILL VARY AMONG THE GUIDANCE SO IT WILL TAKE TIME TO
RESOLVE FORECAST SPECIFICS. FARTHER EAST, A DEEPENING STORM SYSTEM
TRACKING NORTHEASTWARD AWAY FROM LAKE SUPERIOR ON WEDNESDAY WILL
SWEEP A STRONG COLD FRONT THROUGH THE EAST, ACCOMPANIED BY LOCALLY
HEAVY RAINFALL AS WELL AS A BROAD AREA OF BRISK TO STRONG WINDS.
ENERGY EJECTING FROM THE WEST COAST TROUGH MAY BRING A WAVY
FRONTAL SYSTEM INTO THE CENTRAL AND EASTERN U.S. LATE THIS WEEK
THROUGH THE WEEKEND. SOME PRECIPITATION MAY DEVELOP ALONG THIS
FRONT BY THE WEEKEND.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
CLUSTERING HAS BEEN STEADILY IMPROVING FOR THE DEPTH AND TRACK OF
THE STORM EXPECTED TO BE CLOSE TO THE NORTHEASTERN SHORE OF LAKE
SUPERIOR BY THE START OF THE PERIOD EARLY WEDNESDAY. MOST GUIDANCE
HAS BEEN CONVERGING TOWARD THE AVERAGE OF THE RECENT SPREAD BUT
THE 12Z ECMWF WAS SOMEWHAT ON THE DEEPER SIDE. LATEST GFS RUNS
HAVE BEEN A BIT ON THE SLOWER SIDE WITH PROGRESSION OF THE
TRAILING FRONT ACROSS THE EAST, WHILE LATEST RUNS HAVE BACKED AWAY
SOMEWHAT FROM THE IDEA OF THE PRONOUNCED FRONTAL WAVE THAT HAD
PREVIOUSLY BEEN SUGGESTED NEAR/NORTH OF MAINE BY EARLY THURSDAY.
INTO EARLY THURSDAY THERE IS DECENT AGREEMENT, AND FOR AT LEAST
THE PAST 12 HOURS OR SO CONTINUITY AS WELL, REGARDING THE LEADING
SYSTEM FORECAST TO TRACK SOUTHEASTWARD TOWARD THE PACIFIC
NORTHWEST WEDNESDAY-THURSDAY. THEN AFTER EARLY THURSDAY SOLUTIONS
BEGIN TO DIVERGE FOR UPSTREAM SHORTWAVE ENERGY (LATEST UKMET RUNS
TENDING TO BE THE FASTEST AND MOST WESTWARD-ELONGATED). THIS
DEVELOPING ISSUE INITIALLY COMPLICATES THE FORECAST NEAR THE WEST
COAST, INFLUENCING EXACTLY HOW THE LEADING UPPER TROUGH MAY
INCORPORATE A SEPARATE SOUTHERN STREAM FEATURE INITIALLY FARTHER
OUT IN THE PACIFIC. THIS EVOLUTION COULD BRING A FAIRLY COMPACT
BUT VIGOROUS WAVE TO THE VICINITY OF NORTHERN CALIFORNIA LATE IN
THE WEEK. CURRENT GUIDANCE SHOWS A FAIRLY NARROW CORRIDOR FOR THE
POTENTIAL TRACK OF THIS WAVE BUT A LOT OF SPREAD FOR TIMING AND
DEPTH. AFOREMENTIONED ISSUES WITH THE UPSTREAM ENERGY ULTIMATELY
LEAD TO A WIDENING VARIETY OF POSSIBILITIES FOR HOW THE LEADING
ENERGY MAY EJECT EASTWARD AND REFLECT AT THE SURFACE TO THE EAST
OF THE ROCKIES, AND OF COURSE FOR HOW THE WEST COAST TROUGH WILL
LOOK DURING THE WEEKEND. THE NEW 00Z CMC SEEMS OVERDONE WITH THE
AMOUNT OF ENERGY CUTTING THROUGH THE EAST-CENTRAL PACIFIC RIDGE BY
NEXT SUNDAY, LEADING TO FLATTER FLOW ALONG THE WEST COAST, BUT
OTHERWISE IT IS HARD TO DISCOUNT ANY INDIVIDUAL SOLUTIONS SINCE
MOST FIT WITHIN THE OVERALL MEAN PATTERN EVEN WITH DIFFERENT
SHORTWAVE DETAILS. AT LEAST THERE IS STILL DECENT CONTINUITY FOR
THE WAVY FRONT REACHING THE NORTH-CENTRAL PLAINS/UPPER MIDWEST
AROUND FRIDAY, BUT SPECIFICS FOR THIS FRONT DIVERGE THEREAFTER.
BASED ON THE 12Z/18Z ARRAY OF GUIDANCE, THE UPDATED FORECAST
STARTED WITH AN OPERATIONAL MODEL COMPOSITE EARLY AND THEN
STEADILY INCREASED 18Z GEFS/12Z ECMWF MEAN INPUT TO HALF TOTAL
WEIGHT BY LATE IN THE PERIOD. THIS PROVIDED FAIRLY GOOD CONTINUITY
INTO LATE WEEK WHILE DETAIL CHANGES IN MOST GUIDANCE LED TO SOME
ADJUSTMENTS BY SATURDAY NEAR THE WEST COAST.
..WEATHER/HAZARD HIGHLIGHTS
A SYSTEM NEARING THE PACIFIC NORTHWEST SHOULD CONTINUE SPREADING
MOISTURE INTO THE REGION AND THE FAR NORTHERN ROCKIES DURING
WEDNESDAY WITH SOME LOCALLY MODERATE TO HEAVY RAIN AND HIGHER
ELEVATION SNOW POSSIBLE. GRADUAL AMPLIFICATION OF UPPER TROUGHING
SHOULD EXPAND THE PRECIPITATION SHIELD SOUTHEASTWARD THROUGH THE
REST OF THE WEEK, POSSIBLY REACHING INTO CENTRAL OR SOUTHERN
CALIFORNIA AND THE CENTRAL ROCKIES. FOR A PERIOD OF TIME LATE IN
THE WEEK, THE FRONT ASSOCIATED WITH THE INITIAL SYSTEM COULD DRAW
IN SOME LOWER LATITUDE MOISTURE/WAVINESS, WHICH WOULD ENHANCE
RAIN/SNOW TOTALS OVER SOME AREAS--MOST LIKELY IN THE VICINITY OF
NORTHERN CALIFORNIA. CONFIDENCE IN THE SPECIFICS OF THIS POTENTIAL
EVOLUTION IS STILL NOT GREAT THOUGH. ANOTHER SYSTEM DROPPING
SOUTHEASTWARD TOWARD THE WEST COAST MAY BRING ANOTHER ROUND OF
PRECIPITATION AROUND THE END OF THE WEEK OR THE WEEKEND. SNOW
LEVELS IN THE NORTHWEST COULD DECLINE TO FAIRLY LOW ELEVATIONS
OVER SOME AREAS.
STRONG LOW PRESSURE TRACKING NORTHEASTWARD OVER CANADA WILL PUSH A
COLD FRONT THROUGH THE EASTERN U.S. DURING WEDNESDAY-WEDNESDAY
NIGHT. AREAS OF MODERATE TO HEAVY RAIN MAY ACCOMPANY THIS FRONT
GIVEN THE VIGOROUS DYNAMICS ALOFT AND STRONG SOUTHERLY FLOW OF
MOISTURE AHEAD OF THE FRONT. THIS STORM SYSTEM AND ITS FRONT MAY
PRODUCE STRONG WINDS OVER SOME AREAS OF THE NORTHEAST QUADRANT OF
THE LOWER 48. EXPECT A BRIEF PERIOD OF LAKE EFFECT SNOW AFTER
SYSTEM PASSAGE. A WAVY FRONT REACHING THE NORTH-CENTRAL
PLAINS/UPPER MIDWEST BY FRIDAY SHOULD NOT HAVE TOO MUCH
PRECIPITATION WITH IT AS IT CONTINUES ACROSS THE NORTHERN-CENTRAL
U.S. INTO THE FIRST PART OF THE WEEKEND. MORE ORGANIZED RAINFALL
COULD THEN DEVELOP NEAR THE FRONT AS IT STALLS OVER THE
EAST-CENTRAL U.S., DEPENDING ON HOW MUCH MOISTURE THE
WEST-SOUTHWESTERLY FLOW ALOFT AND POSSIBLY SOME LOW LEVEL GULF
INFLOW CONTRIBUTE.
MUCH OF THE WEST AND FAR NORTHERN PLAINS SHOULD SEE BELOW NORMAL
TEMPERATURES FOR MOST OF NEXT WEEK. THIS IS ESPECIALLY THE CASE
FOR DAYTIME HIGHS, WITH COLDEST ANOMALIES OF 10-25F BELOW NORMAL
POSSIBLE OVER/NEAR MONTANA MID-LATE WEEK. LATEST FORECAST TRENDS
HAVE BEEN TOWARD SLIGHTLY LESS EXTREME COLD OVER THE NORTHWEST
LATE IN THE WEEK, SO ANY DAILY RECORDS FOR COLD LOWS/DAYTIME HIGHS
MAY BE FAIRLY ISOLATED. MEANWHILE, THE EASTERN U.S. WILL SEE A
BRIEF PERIOD OF ABOVE NORMAL TEMPERATURES (UP TO PLUS 10-15F
ANOMALIES FOR HIGHS AND SLIGHTLY WARMER FOR MORNING LOWS) ON
WEDNESDAY AHEAD OF THE FRONT CROSSING THE REGION. THEN THE COLD
AIR BEHIND THE FRONT WILL DROP READINGS TO MODERATELY BELOW NORMAL
OVER THE CENTRAL AND THEN EASTERN U.S. WEDNESDAY-THURSDAY,
FOLLOWED BY A REBOUND TO ABOVE NORMAL READINGS FROM THE
CENTRAL-SOUTHERN PLAINS INTO PARTS OF THE SOUTHEAST.
RAUSCH
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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES 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
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