806
FXUS02 KWBC 191900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 PM EST SAT NOV 19 2022
VALID 12Z TUE NOV 22 2022 - 12Z SAT NOV 26 2022
...A COUPLE OF LOW PRESSURE SYSTEMS INCLUDING A POSSIBLE
NOR'EASTER COULD CAUSE MEANINGFUL PRECIPITATION ACROSS EASTERN
PARTS OF THE U.S. LATE NEXT WEEK...
..OVERVIEW
A QUASI-ZONAL UPPER PATTERN WITH EMBEDDED SHORTWAVES SHOULD BE IN
PLACE AS THE MEDIUM RANGE PERIOD BEGINS TUESDAY WITH REASONABLY
QUIET WEATHER IN PLACE ACROSS THE COUNTRY, SAVE FOR THE
POSSIBILITY OF HEAVY RAINFALL ACROSS NORTHEASTERN FLORIDA IN
EASTERLY FLOW JUST BEHIND A SURFACE LOW AND FRONTAL BOUNDARY AS
WELL AS A ROUND OF PRECIPITATION IN THE PACIFIC NORTHWEST. BY
MID-LATE WEEK THE GUIDANCE HAS BEEN CONSISTENTLY ADVERTISING A
RAPID AMPLIFICATION OF THE EASTERN PACIFIC/CONTIGUOUS U.S. FLOW,
WITH AN EASTERN PACIFIC TROUGH AND BUILDING WESTERN U.S. RIDGE
LEADING TO A TROUGH DIGGING INTO THE CENTRAL U.S. BY
THURSDAY/THANKSGIVING DAY. THERE IS STILL A FAIR DEGREE OF
UNCERTAINTY OVER WHAT BECOMES OF THIS TROUGH BY FRIDAY AND BEYOND.
THE MAJORITY SCENARIO THUS FAR WOULD HAVE THE OVERALL UPPER TROUGH
CONTINUE EASTWARD AND SUPPORT A CENTRAL U.S. LOW PRESSURE/FRONTAL
SYSTEM CROSSING THE GREAT LAKES WHILE A WESTERN ATLANTIC LOW
PRESSURE SYSTEM LIFTS NORTH (WITH SOME INTERACTION POSSIBLE NEAR
NEW ENGLAND). THESE FEATURES WOULD SUPPORT INCREASING CHANCES FOR
PRECIPITATION LATE NEXT WEEK, BUT CONTINUED SIGNIFICANT GUIDANCE
SPREAD IN THE EXACT LOW TRACKS LEADS TO LOW CONFIDENCE FOR
PRECIPITATION TYPES AND INTENSITY ACROSS THE EAST. TOWARD THE END
OF THE WEEK ISSUES ALSO DEVELOP WITH THE EASTERN PACIFIC UPPER
TROUGH, LEADING TO UNCERTAINTY IN FLOW DETAILS ACROSS THE
NORTHWEST U.S. AND PERHAPS EVEN A ROLE IN THE FORECAST FARTHER
EAST.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
LATEST GUIDANCE HAS GENERALLY SETTLED INTO BETTER AGREEMENT
(VERSUS A COUPLE DAYS AGO) FOR THE ULTIMATE EVOLUTION OF THE UPPER
TROUGH REACHING THE CENTRAL U.S. BY THURSDAY AND LIKELY CONTINUING
INTO THE EAST THEREAFTER. HOWEVER THE PERSISTENCE OF A STRAY
INDIVIDUAL SOLUTION OR TWO EACH RUN CONTINUES TO SUGGEST A
LINGERING RISK THAT GUIDANCE COULD EVENTUALLY GRAVITATE TO AN
EVOLUTION SIGNIFICANTLY DIFFERENT FROM CONSENSUS. THE MAJORITY
SCENARIO (WHICH INCLUDES THE GEFS/ECENS/CMCENS MEANS, LATEST
ECMWF/CMC RUNS, AND 00Z/06Z GFS) HAS THE UPPER TROUGH REMAINING
FAIRLY PHASED WITH A POSSIBLE EMBEDDED UPPER LOW CENTER TRACKING
OVER THE GREAT LAKES/OHIO VALLEY AROUND FRIDAY AND CONTINUING
NORTHEAST INTO SATURDAY. AT THE SAME TIME SURFACE LOW PRESSURE
WOULD TRACK INTO THE GREAT LAKES THURSDAY-FRIDAY WHILE A SEPARATE
SURFACE LOW DEVELOPS ALONG THE EAST COAST, WITH POSSIBLE
CONSOLIDATION OF THESE CENTERS OVER OR NEAR NEW ENGLAND BY
SATURDAY. JUST WITHIN THIS MAJORITY CLUSTER THERE IS A FAIRLY
BROAD RANGE OF MODEL/ENSEMBLE POSSIBILITIES FOR STORM TRACK AND
INTENSITY BY 6-7 DAYS OUT. MEANWHILE, A SMALL MINORITY STILL SHOWS
THE POTENTIAL FOR AN UPPER LOW TO CLOSE OFF WELL IN THE
SOUTHWESTERN PART OF THE UPPER TROUGH. THE 00Z UKMET DID THIS OVER
THE SOUTHERN ROCKIES/HIGH PLAINS (SHIFTED A BIT EASTWARD IN THE
NEW 12Z RUN), WHILE THE NEW 12Z GFS HAS SUDDENLY CHANGED TO A
SOUTHERN PLAINS/LOWER MISSISSIPPI VALLEY UPPER LOW BY
FRIDAY-SATURDAY. SUCH AN EVOLUTION WOULD GREATLY SHIFT THE SURFACE
PATTERN AND EMPHASIS FOR HEAVIEST PRECIPITATION OVER THE
CENTRAL/EASTERN U.S. INDIVIDUAL ENSEMBLE MEMBERS GENERALLY REFLECT
THE IDEAS OF OPERATIONAL SOLUTIONS AS A WHOLE, IN THAT MEMBERS
SHOW THE GREATEST DENSITY CLOSER TO THE CONSENSUS IDEA AND A
SMALLER NUMBER SUGGESTING OTHER ALTERNATIVES.
THE OTHER MAJOR FORECAST ISSUE ARISING BY FRIDAY-SATURDAY INVOLVES
FLOW WITHIN THE EASTERN PACIFIC TROUGH. THERE HAS BEEN SOME
INCONSISTENCY IN GUIDANCE ALREADY AND CURRENT SOLUTIONS ARE SPLIT
OVER WHETHER FLOW MAY SEPARATE, LEADING TO TWO GENERAL CLUSTERS--A
PHASED TROUGH AND STRONG RIDGE EXTENDING INTO SOUTHWESTERN CANADA
(ENSEMBLE MEANS, LATEST ECMWF/CMC RUNS, AND 00Z/06Z GFS) VERSUS
SEPARATED TROUGH ENERGY THAT LEADS TO MORE PACIFIC FLOW DENTING
THE WESTERN NORTH AMERICAN RIDGE (12Z GFS/UKMET). THE FACT THAT
SOLUTION CLUSTERS FOR BOTH OF THE MAJOR FORECAST UNCERTAINTIES
ROUGHLY COINCIDE SUGGESTS THE FARTHER WEST EVOLUTION COULD PLAY A
ROLE IN DECIDING WHAT HAPPENS OVER THE EASTERN HALF OF THE U.S.
INTERESTINGLY, THE NEW 12Z ECMWF SEPARATES FLOW WITHIN THE PACIFIC
TROUGH BUT FOR A SHORTER TIME AND TO A LESSER EXTENT THAN THE
MINORITY CLUSTER, WHILE MAINTAINING DECENT CONTINUITY FOR THE
EASTERN U.S. EVOLUTION.
THE UPDATED FORECAST BASED ON 00Z/06Z GUIDANCE SIDED WITH THE
MAJORITY SCENARIO REPRESENTED BY THE ENSEMBLE MEANS ALONG WITH THE
00Z/06Z GFS AND 00Z ECMWF/CMC. THE FIRST HALF OF THE PERIOD
EMPLOYED THE OPERATIONAL MODELS EXCLUSIVELY TO DEPICT THE BEST
DETAIL POSSIBLE WITHIN THAT CLUSTER, WHILE DAYS 6-7
FRIDAY-SATURDAY TRANSITIONED TO SOME INPUT FROM THE 06Z GEFS/00Z
ECMWF MEANS AS WELL AS WPC CONTINUITY. THIS APPROACH HELPED TO
PROVIDE A FAIRLY STEADY SOLUTION WHILE AWAITING ANY POTENTIALLY
SIGNIFICANT SHIFTS IN THE GUIDANCE.
..WEATHER/HAZARD HIGHLIGHTS
EXPECT SOME RAIN AND HIGHER ELEVATION SNOW ACROSS THE PACIFIC
NORTHWEST AND FARTHER EAST INTO THE NORTHERN ROCKIES ON
TUESDAY-WEDNESDAY WITH A FRONTAL SYSTEM PASSING THROUGH. MODEL
GUIDANCE CONTINUES TO SHOW A FAIRLY DRY PERIOD FOR THE NORTHWEST
AND INTO THE ROCKIES LATER IN THE WEEK AS SURFACE HIGH PRESSURE
AND UPPER RIDGING BUILD IN. SOME PACIFIC MOISTURE COULD START TO
REACH THE COAST AGAIN AROUND SATURDAY. FARTHER SOUTH, SANTA ANA
WINDS MAY BE A CONCERN ACROSS SOUTHERN CALIFORNIA FOR AT LEAST A
PORTION OF THE PERIOD. SHOWERS AND THUNDERSTORMS ARE POSSIBLE
ACROSS FLORIDA AND INTO THE SOUTHEAST THROUGH TUESDAY-WEDNESDAY
ALONG AND NORTH OF A WAVY FRONT THAT WILL BE ACCOMPANIED BY A BAND
OF ENHANCED MOISTURE. THE BEST DEFINED FRONTAL WAVE MAY TAKE SHAPE
OFFSHORE THE SOUTHEAST ON WEDNESDAY. ISOLATED FLASH FLOODING COULD
BE A CONCERN PARTICULARLY ACROSS URBAN AREAS.
THEN AS THE UPPER TROUGH AMPLIFIES EAST OF THE ROCKIES BY
THANKSGIVING DAY AND BEYOND, GULF MOISTURE SHOULD STREAM INTO THE
EASTERN HALF OF THE U.S. AHEAD OF THE TROUGH. THE SOUTHEASTERN
QUADRANT OF THE U.S. NORTHWARD INTO THE OHIO VALLEY AND GREAT
LAKES MAY SEE SOME PRECIPITATION AROUND THANKSGIVING, WHILE
HEAVIER PRECIPITATION LOOKS MORE LIKELY ACROSS THE NORTHEASTERN
U.S. ON FRIDAY. CURRENT FORECASTS INDICATE THAT WINTRY
PRECIPITATION IS A BETTER POSSIBILITY FOR THE INTERIOR NORTHEAST
WHILE THE METROPOLITAN AREAS ALONG THE I-95 CORRIDOR ARE MORE
LIKELY TO GET RAIN. BUT STAY TUNED TO FUTURE FORECASTS AS THESE
UNCERTAIN DETAILS LIKE PRECIPITATION TYPES IN PARTICULAR AREAS
COULD CHANGE AS MODEL GUIDANCE EVENTUALLY COMES INTO BETTER
CONSENSUS WITH LOW TRACKS AND TEMPERATURES. DEPENDING ON THE
STRENGTH OF ONE OR MORE LOW PRESSURE CENTERS, WINDS COULD BECOME
BRISK TO STRONG FOR A TIME. ALSO NOTE THAT THERE IS A MINORITY
POTENTIAL FOR SIGNIFICANTLY DIFFERENT PRECIPITATION COVERAGE AND
AMOUNTS, WHICH COULD INVOLVE MORE RAINFALL ACROSS THE SOUTHERN
TIER AND LOWER TOTALS FARTHER NORTH.
TEMPERATURES IN THE MEDIUM RANGE PERIOD SHOULD BE OVERALL MORE
SEASONABLE COMPARED TO THOSE OF THIS PAST WEEK. COOLER THAN NORMAL
TEMPERATURES COULD CONTINUE ACROSS THE SOUTHERN TIER FOR TUESDAY,
ESPECIALLY ACROSS SOUTHERN TEXAS WHERE HIGHS COULD BE 10-20F BELOW
NORMAL. TEMPERATURES ARE LIKELY TO TREND ABOVE AVERAGE ALONG THE
WEST COAST BY MIDWEEK WITH PLUS 5-15F ANOMALIES EXPANDING INTO THE
ROCKIES AND CENTRAL U.S. LATER IN THE WEEK AS THE UPPER RIDGE
BUILDS IN. CONVERSELY, POST-FRONTAL COOLER TEMPERATURES ESPECIALLY
IN TERMS OF HIGHS SHOULD EXTEND FROM THE MISSISSIPPI VALLEY TOWARD
THE EAST COAST FRIDAY-SATURDAY AS THE UPPER TROUGH MOVES THROUGH.
RAUSCH/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, 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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