624
FXUS02 KWBC 271859
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 PM 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
THE GUIDANCE CONTINUES TO SHOW GOOD CLUSTERING AND AGREEMENT IN
TERMS OF TRACK AND DEPTH OF THE STORM EXPECTED TO BE CLOSE TO THE
NORTHEASTERN SHORE OF LAKE SUPERIOR BY THE START OF THE PERIOD ON
WEDNESDAY. THERE REMAINS SOME MINOR TIMING DIFFERENCES FOR THE
TRAILING FRONT THROUGH THE EAST WEDNESDAY-WEDNESDAY NIGHT.
ATTENTION SHIFTS OUT WEST THE REST OF THE PERIOD AS A COUPLE OF
POTENTIALLY IMPACTFUL SYSTEMS IMPACT THE WESTERN U.S.. THE FIRST,
EXPECTED TO REACH THE COAST BY EARLY THURSDAY, COULD BRING A
FAIRLY COMPACT FROM VIGOROUS WAVE TO THE VICINITY OF NORTHERN
CALIFORNIA LATER THIS WEEK. MODELS SHOW SOME DIFFERENCES IN TERMS
OF TIMING AND DEPTH (LEADING TO QPF DIFFERENCES TOO), BUT BETTER
CONSENSUS ON THE OVERALL TRACK. PREVIOUS RUNS OF THE UKMET WERE
FASTER TO BRING THE ENERGY INLAND, WHILE THE 00Z ECMWF WAS
SLOWEST/DEEPEST, WITH THE 06Z/12Z GFS AND 00Z/12Z CMC A GOOD
MIDDLE GROUND. FTHE 12Z UKMET AND ECMWF RUNS TODAY BOTH DID TREND
CLOSER TO THE GFS/CMC. UPSTREAM, THE NEXT SYSTEM MAY BRING A
COMPACT CLOSED LOW NEAR THE CANADIAN MARITIMES OR PACIFIC
NORTHWEST NEXT WEEKEND BUT WITH MUCH FAIRLY LARGE UNCERTAINTIES IN
TERMS OF TIMING, WHICH CONTINUE WITH TODAYS LATEST 12Z RUNS. ONE
NOTABLE OUTLIER WAS THE CMC AS IT WAS MUCH FLATTER THAN THE BETTER
CONSENSUS OF THE ECMWF/GFS AND ENSEMBLES ALL SUGGESTING MORE
AMPLIFICATION TO THE PATTERN. ALTHOUGH, DESPITE BETTER AGREEMENT
FOR A MORE AMPLIFIED SYSTEM, UNCERAINTY REMAINS HIGH ON THE
SPECIFICS INCLUDING TIMING AND DEPTH OF THIS SYSTEM.
THE WPC FORECAST FOR TODAY (SENT BEFORE 12Z MODEL RUNS WERE
AVAILABLE) USED A GENERAL BLEND BETWEEN EARLY ON WITH THE 00Z/06Z
DETERMINISTIC RUNS WITH MORE WEIGHTING TOWARDS THE GFS/ECMWF OVER
THE CMC/UKMET DUE TO INITIAL ISSUES OUT WEST. AFTER DAY 5, LEANED
INCREASINGLY MORE TOWARDS THE ENSEMBLE MEANS WHICH SERVED AS A
GOOD MIDDLE GROUND AMIDST PLENTY OF UNCERTAINTY WITH THE SECOND
WESTERN U.S. SYSTEM.
..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, BUT ALSO POTENTIAL FOR SNOW IN THE
LOWLANDS AS WELL. 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 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 AS WELL. 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.
SANTORELLI/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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