286
FXUS02 KWBC 220701
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST WED NOV 22 2023
VALID 12Z SAT NOV 25 2023 - 12Z WED NOV 29 2023
..PATTERN OVERVIEW
EASTERN PACIFIC INTO NORTHWESTERN NORTH AMERICA UPPER RIDGING THAT
DRIFTS AT LEAST TO THE WEST COAST BY NEXT WEEK WILL PROMOTE A
DEEPER/BROADER MEAN TROUGH EXTENDING FROM CANADA INTO THE LOWER 48
EAST OF THE ROCKIES. MEANWHILE INITIAL WESTERN U.S. TROUGH ENERGY
SHOULD SPLIT, WITH SOME OF IT CONTINUING EASTWARD/PHASING WITH AN
AMPLIFYING CANADIAN SHORTWAVE AND THE REST ELONGATING FOR A TIME
OVER THE SOUTHWESTERN U.S. WITH SOME UNCERTAINTY AS TO ITS
ULTIMATE SHAPE NEXT WEEK. AT THE SURFACE THERE IS A CONTINUED
THEME OF WAVINESS NEAR/SOUTH OF THE GULF COAST AND CLOSE TO THE
EAST COAST, BRINGING SOME POTENTIAL FOR PRECIPITATION ALONG THOSE
COASTS BUT WITH LACK OF CONFIDENCE IN THE SPECIFICS. NORTHERN
STREAM FRONTS/WAVES WILL NOT HAVE A LOT OF MOISTURE TO WORK AND
SHOULD PRODUCE LIGHT PRECIPITATION IF ANY. THE UPPER ENERGY
INITIALLY EMERGING FROM THE WEST MAY PRODUCE AN AREA OF SNOW OVER
THE CENTRAL PLAINS (AND LINGERING OVER THE ROCKIES) ON SATURDAY
WITH SOME RAIN TO THE SOUTH. LIGHT PRECIPITATION MAY EXTEND
FARTHER EAST AND THEN THE PATTERN SHOULD BE FAVORABLE FOR SOME
AREAS OF LAKE EFFECT SNOW FROM SUNDAY ONWARD.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
GUIDANCE CONTINUES TO SHOW DIFFICULTY IN RESOLVING SOME OF THE
DETAILS WITHIN THE MORE AGREEABLE LARGE SCALE EVOLUTION. IN LATEST
RUNS THERE HAS BEEN SOME CONSENSUS EMERGING TOWARD A COMPACT
SURFACE WAVE EVOLVING OFF THE SOUTHEAST COAST DURING THE WEEKEND
IN RESPONSE TO WEAK SOUTHERN STREAM ENERGY AND THEN LIFTING
NORTH/NORTHEAST AS THE OVERALL CANADA INTO CENTRAL U.S. TROUGH
APPROACHES. HOWEVER THE PAST COUPLE CMC/UKMET RUNS HAVE DEPICTED A
FARTHER WEST SURFACE LOW TRACK THAN THE GFS/ECMWF AND THEIR MEANS
PLUS THE CMCENS MEAN. THE AMPLIFYING CANADIAN TROUGH ENERGY SHOULD
SUPPORT A WELL DEFINED WAVE CROSSING THE UPPER GREAT LAKES OR
ONTARIO AROUND SUNDAY (WITH TRAILING FRONT). THEN THIS FEATURE
AND THE WESTERN ATLANTIC WAVE MAY INTERACT TO PRODUCE A STRONGER
SYSTEM TO THE NORTHEAST OF MAINE BY EARLY TUESDAY. THE NEW 00Z GFS
IS IN THE MINORITY FOR ITS CONCENTRATED UPPER LOW CROSSING
NORTHERN NEW ENGLAND THOUGH. BEHIND THIS EVOLUTION, GUIDANCE HAS
BEEN DIVERGENT AND ERRATIC WITH SYSTEM DETAILS IN LIGHT OF LOWER
PREDICTABILITY SHORTWAVE DETAILS AT THE 6-7 DAY TIME FRAME
(TUESDAY-WEDNESDAY). THE MOST COMMON THEME, CURRENTLY ILLUSTRATED
BEST BY RECENT ECMWF RUNS AND THE GEFS/CMCENS MEANS, HAS GENERALLY
BEEN TOWARD A WAVE REACHING THE NORTHERN PLAINS AND THEN THE GREAT
LAKES DURING THAT PERIOD. 12Z ECMWF-INITIALIZED MACHINE LEARNING
MODELS ALSO DEPICT THIS EVOLUTION. CMC RUNS STRAY FASTER WHILE THE
GFS HAS BEEN INCONSISTENT WITH THE NORTHERN TIER DETAILS FROM RUN
TO RUN. SPREAD OVER THE EAST PACIFIC/WESTERN U.S. AFTER MONDAY IS
NOT AS BAD AS IT WAS 24 HOURS AGO BUT MEANINGFUL DIFFERENCES STILL
EXIST. IN PARTICULAR, THE CMC HAS BEEN FASTEST TO SHIFT THE
OVERALL PATTERN EASTWARD WHILE THE GFS IS IN THE MINORITY WITH HOW
LONG IT HOLDS ONTO A CLOSED LOW NEAR BAJA CALIFORNIA.
THE LATEST MANUAL FORECAST STARTED WITH A 12Z/18Z OPERATIONAL
MODEL COMPOSITE EARLY IN THE PERIOD AND THEN BY AROUND MONDAY
PHASED OUT THE MINORITY INPUT OF THE UKMET/CMC DUE TO THEIR LOWER
CONFIDENCE SOLUTIONS ALONG THE EAST COAST AND WITH THE CMC
STARTING TO STRAY FROM THE MAJORITY ALONG THE WEST COAST.
INCREASING WEIGHT OF THE 18Z GFS/12Z ECENS MEANS LATER IN THE
PERIOD LED TO AN EVEN PROPORTION OF MODELS/MEANS BY DAY 7
WEDNESDAY, WITH COMMON ASPECTS OF THE GFS/ECMWF HELPING TO IMPROVE
DEFINITION BUT DIFFERENCES OVER OTHER AREAS OFFSETTING TO KEEP THE
FORECAST CLOSE TO THE MEANS.
..WEATHER/HAZARDS HIGHLIGHTS
THE UPPER SYSTEM EMERGING FROM THE WEST MAY PRODUCE A FAIRLY
LOCALIZED AREA OF MEANINGFUL SNOWFALL OVER THE CENTRAL PLAINS
AROUND SATURDAY. LATEST PROBABILITIES FOR AT LEAST A QUARTER INCH
OF LIQUID IN THE FORM OF SNOW SHOW THE BEST POTENTIAL CENTERED
OVER WEST-CENTRAL KANSAS. LIGHTER ACTIVITY COULD LINGER OVER THE
SOUTH-CENTRAL ROCKIES. SOME RAIN MAY BE POSSIBLE OVER THE SOUTHERN
PLAINS. A FRONT MAY CARRY REMAINING MOISTURE EASTWARD BUT LIKELY
WITH FAIRLY LIGHT AMOUNTS. LOW PRESSURE DEVELOPING OFF THE
SOUTHEAST COAST DURING THE WEEKEND SHOULD LIFT-NORTHEAST
THEREAFTER. COASTAL NORTH CAROLINA COULD SEE SOME RAIN WITH THIS
SYSTEM WHILE CONFIDENCE REMAINS BELOW AVERAGE FOR HOW MUCH
PRECIPITATION MAY OCCUR OVER THE NORTHEAST. A PASSING WAVE/FRONT
AROUND SUNDAY-MONDAY AND THEN TRAILING FLOW AND POSSIBLY ANOTHER
SYSTEM SHOULD PRODUCE EPISODES OF GREAT LAKES SNOW FROM A
COMBINATION OF LAKE EFFECT AND SYNOPTIC INFLUENCES. THE GULF
COAST/FLORIDA MAY SEE A REBOUND IN RAINFALL POTENTIAL TOWARD
MIDWEEK BUT WITH LOW CONFIDENCE IN SPECIFICS AT THIS TIME.
CURRENTLY THERE IS NO SUFFICIENTLY COHERENT SIGNAL FOR ORGANIZED
HEAVY RAINFALL TO WARRANT ANY RISK AREAS ON THE DAY 4 AND DAY 5
EXCESSIVE RAINFALL OUTLOOKS.
IN A FAIRLY COOL PATTERN OVER A MAJORITY OF THE LOWER 48 FROM THE
WEEKEND INTO THE MIDDLE OF NEXT WEEK, THE MOST EXTREME TEMPERATURE
ANOMALIES SHOULD BE OVER THE EASTERN SLOPES OF THE CENTRAL ROCKIES
INTO CENTRAL PLAINS ON SATURDAY WITH HIGHS 15-25F BELOW NORMAL.
SOME OF THIS COLD AIR WILL CONTINUE SOUTHWARD INTO THE SOUTHERN
PLAINS THEREAFTER WITH HIGHS AT LEAST 10-15F BELOW NORMAL
SUNDAY-MONDAY AND PERHAPS INTO TUESDAY OVER FAR SOUTHERN TEXAS.
ALSO, DURING THE WEEKEND INTO EARLY NEXT WEEK BRISK WINDS WILL
MAKE IT FEEL COLDER OVER THE SOUTHWESTERN U.S. AND VICINITY. THE
REST OF THE CENTRAL U.S. SHOULD MODERATE CLOSE TO NORMAL BY
TUESDAY WITH NORTHERN PLAINS LOWS POSSIBLY TRENDING ABOVE NORMAL.
CONTINUE TO EXPECT SLIGHTLY ABOVE NORMAL TEMPERATURES ALONG THE
CENTRAL-NORTHERN WEST COAST AND PERHAPS EXPANDING A BIT BY THE
MIDDLE OF NEXT WEEK AS EAST PACIFIC UPPER RIDGING DRIFTS EASTWARD.
THE EAST COAST WILL LIKELY BE CHILLY ON SATURDAY (HIGHS UP TO
10-15F BELOW NORMAL OVER THE MID-ATLANTIC INTO NEW ENGLAND), WITH
MOST OF THE EAST TENDING TO BE NEAR TO SOMEWHAT BELOW NORMAL FOR
THE REST OF THE PERIOD.
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 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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