179
FXUS02 KWBC 221858
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 PM EST WED NOV 22 2023
VALID 12Z SAT NOV 25 2023 - 12Z WED NOV 29 2023
...MEANINGFUL SNOW LIKELY SATURDAY ACROSS PARTS OF THE
SOUTH-CENTRAL PLAINS...
..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. BUT ON SATURDAY, THE UPPER ENERGY
INITIALLY INITIALLY EMERGING FROM THE WEST LOOKS TO PRODUCE AN
AREA OF SNOW OVER THE SOUTH-CENTRAL PLAINS (AND LINGERING OVER THE
ROCKIES) WITH SOME RAIN TO THE SOUTH. 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 COINCIDE WITH MUCH MOISTURE
AND SHOULD PRODUCE LIGHT PRECIPITATION IF ANY. LAKE EFFECT
PRECIPITATION IS LIKELY THOUGH THROUGH THE FIRST HALF OF NEXT WEEK.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
GUIDANCE CONTINUES TO SHOW DIFFICULTY IN RESOLVING SOME OF THE
DETAILS WITHIN THE MORE AGREEABLE LARGE SCALE EVOLUTION. RECENT
GUIDANCE CONTINUES TO SHOW INDICATIONS OF A COMPACT SURFACE LOW
DEVELOPING OFF THE SOUTHEAST COAST DURING THE WEEKEND IN RESPONSE
TO WEAK SOUTHERN STREAM ENERGY AND THEN LIFTING FAIRLY QUICKLY
NORTH/NORTHEAST THROUGH THE WESTERN ATLANTIC AS THE OVERALL CANADA
INTO CENTRAL U.S. TROUGH APPROACHES. CMC RUNS (00Z, THE NEW 12Z,
AND MANY CMC ENSEMBLE MEMBERS) TEND TO BE FARTHER WEST WITH ITS
TRACK, AND UKMET RUNS ARE FARTHER WEST AS WELL. THE 00Z ECMWF
SEEMED TO BE A REASONABLE MIDDLE GROUND GIVEN THE 00/06Z GFS RUNS
WERE EAST. THE 12Z GFS/GEFS MEAN TRENDED A BIT WEST FROM THE
00Z/06Z POSITIONS, WHICH PUTS THEM CLOSER TO THE EC, SO THIS TRACK
WAS FAVORED. THE SURFACE LOW LOOKS TO TRACK TO THE NORTH OF MAINE
BY EARLY TUESDAY AND STRENGTHEN AS IT COMBINES WITH AMPLIFYING
CANADIAN TROUGH ENERGY AND POSSIBLY ANOTHER SURFACE LOW. THE
PATTERN ALOFT SHOWS INCREASING SPREAD AS THE 00Z AND 06Z GFS
CONCENTRATE A DEEP UPPER LOW CROSSING NORTHERN NEW ENGLAND. THE
12Z GFS BACKED OFF ON THIS, BUT OVERALL GUIDANCE HAS BEEN
DIVERGENT AND ERRATIC WITH THE PLACEMENT OF SHORTWAVES AND THUS
FRONTS WITHIN THE BROADER TROUGH BY THE 6-7 DAY TIME FRAME
(TUESDAY-WEDNESDAY). CHANGES TO FRONTAL PLACEMENT ARE LIKELY IN
FUTURE FORECASTS GIVEN THE VARYING GUIDANCE.
FARTHER WEST, MODELS SHOW SOME DIFFERENCES WITH MID-UPPER ENERGY
PULLING OFF INTO THE SOUTHWEST EARLY NEXT WEEK, WITH THE 00Z UKMET
SEEMINGLY AN OUTLIER WITH A FARTHER NORTH POSITION OF AN UPPER LOW
CLOSING OFF AROUND MONDAY WHERE THE BULK OF OTHER GUIDANCE HAS
RIDGING SNEAKING IN TOWARD THE WEST COAST. UPSTREAM, AS A CLOSED
LOW TRACKS EAST THROUGH THE PACIFIC, THE 00Z AND 06Z GFS SHOWED A
FARTHER WEST POSITION OF THIS FEATURE ALLOWING FOR A WIDER RIDGE
AXIS COMPARED TO THE WELL-CLUSTERED ECMWF AND CMC. THE 12Z GFS AND
GEFS MEAN HAVE BOTH TRENDED EAST AND ARE MORE AGREEABLE WITH THE
LOW/TROUGH TO RIDGE POSITIONS NOW.
THE WPC FORECAST UTILIZED A MODEL BLEND OF THE 00Z ECMWF, 06Z GFS,
00Z CMC, AND 00Z UKMET (IN ORDER OF MOST TO LEAST WEIGHTING) EARLY
IN THE FORECAST PERIOD. PHASED OUT THE UKMET AND DECREASED THE
PROPORTION OF THE CMC AND GFS FIRST AND EVENTUALLY THE ECMWF AS
LEAD TIME AND SPREAD INCREASED, IN FAVOR OF MORE GEFS AND EC
ENSEMBLE MEAN GUIDANCE THAT ARE LESS PRONE TO THE WAFFLING THAT
DETERMINISTIC MODELS SHOW.
..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, WITH A SLIGHT SHIFT SOUTHWARD IN THIS
FORECAST ISSUANCE TO INCLUDE FAR NORTHERN OKLAHOMA PER THE MODEL
TRENDS. LIGHTER SNOW ACTIVITY COULD LINGER OVER THE SOUTH-CENTRAL
ROCKIES. SOME RAIN MAY BE POSSIBLE OVER THE SOUTHERN PLAINS. THEN
A FRONT MAY CARRY REMAINING MOISTURE EASTWARD INTO SUNDAY 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 OCCURS AS WELL AS THE PRECIPITATION TYPE 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. POTENTIAL FOR ORGANIZED HEAVY RAINFALL REMAINS TOO LOW
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.
TATE/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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page