531
FXUS02 KWBC 210711
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
210 AM EST MON NOV 21 2022
VALID 12Z THU NOV 24 2022 - 12Z MON NOV 28 2022
...A COUPLE OF LOW PRESSURE SYSTEMS INCLUDING A POSSIBLE
NOR'EASTER COULD CAUSE MEANINGFUL PRECIPITATION ACROSS
CENTRAL/EASTERN PARTS OF THE U.S. LATE THIS WEEK...
..OVERVIEW
THE MEDIUM RANGE PERIOD WILL BEGIN THURSDAY WITH LIKELY AN
AMPLIFIED UPPER PATTERN ACROSS THE LOWER 48, WITH A RIDGE ATOP THE
WEST AND A DEEPENING TROUGH ACROSS CENTRAL PARTS OF THE COUNTRY.
BY LATE WEEK THERE CONTINUES TO BE A SIGNIFICANT AMOUNT OF MODEL
SPREAD WITH WHAT BECOMES OF THIS TROUGH, WITH SOLUTIONS RANGING
FROM A LOW CUTTING OFF IN THE SOUTHERN PLAINS TO A MORE PHASED
LARGE-SCALE TROUGH PROGRESSING INTO THE EAST. THE WPC FORECAST HAS
BEEN FAVORING THE LATTER SOLUTION FOR THE PAST FEW DAYS, WHICH AT
THE SURFACE YIELDS A LOW PRESSURE SYSTEM MOVING EAST ACROSS THE
GREAT LAKES OR NEARBY WITH A COLD FRONT PASSING ACROSS THE
CENTRAL-EASTERN U.S. AND PHASING WITH ANOTHER LOW TRACKING
NORTHWARD NEAR THE ATLANTIC COAST, LEADING TO A POTENTIALLY STRONG
STORM AFFECTING NEW ENGLAND DURING THE WEEKEND. BUT THE
PERSISTENCE OF THE MINORITY SCENARIO REDUCES CONFIDENCE AND THERE
IS STILL A POSSIBILITY FOR A SLOWER/SOUTHERN AREA OF SIGNIFICANT
RAINFALL AND LESS PRECIPITATION/SURFACE LOW DEVELOPMENT OVER THE
NORTHEAST. BY EARLY NEXT WEEK, THE UPPER PATTERN IS LIKELY TO
TRANSITION TO MORE ZONAL FLOW, BUT WITH EVENTUAL TROUGHING AND
FRONTS COMING INTO THE NORTHWEST PROMOTING INCREASING
PRECIPITATION CHANCES THERE.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
THE CONFIDENCE IN THE FORECAST FOR DAYS 3-5 (THURSDAY-SATURDAY) IS
MUCH LOWER THAN NORMAL BECAUSE OF THE HIGH DEGREE OF MODEL SPREAD.
OFTEN DIFFERENCES THIS LARGE IN THE EXTENDED RANGE ARE SOMEWHAT
RESOLVED BY THE EARLY PART OF THE MEDIUM RANGE PERIOD. THE TYPE OF
SOLUTION THAT WPC HAS BEEN LEANING TOWARD, A MORE PHASED TROUGH
WITH PERHAPS AN UPPER LOW INSIDE, HAS BEEN MOST PERSISTENTLY
FORECAST BY THE ECMWF RUNS WITH NOTABLE SUPPORT BY EC AND CMC
ENSEMBLE MEMBERS IN PARTICULAR. CMC DETERMINISTIC RUNS WERE ALSO
IN THIS CAMP--UNTIL THE NEWER 00Z RUN. MEANWHILE GFS RUNS HAVE
VARIED QUITE A BIT FROM RUN TO RUN, BUT GENERALLY TOWARD AN UPPER
LOW CLOSING OFF IN THE SOUTHERN STREAM AND LINGERING AROUND THE
SOUTHERN PLAINS. MORE SPECIFICALLY, THE 12Z GFS SEEMED TO BE MORE
PHASED AND IN BETTER ALIGNMENT WITH THE EC/CMC WHILE THE 18Z AND
THE 00Z RUNS INDICATED A SLOW CLOSED LOW AGAIN. UKMET RUNS HAVE
ALSO BEEN CLOSER TO THIS CLOSED LOW SOLUTION, WHILE GEFS MEMBERS
SHOW SOME SIGNIFICANT SPREAD WITH SOME CLOSER TO THE OPERATIONAL
GFS AND SOME WITH A MORE EC/CMC PHASED TYPE SOLUTION. BOTH TYPES
OF SCENARIOS CAN AND DO HAPPEN DOWNSTREAM OF RIDGING SO THERE IS
LOW CONFIDENCE IN WHICH TO CHOOSE. AT THE SURFACE, THERE HAS BEEN
SOME WAFFLING WITH THE PLACEMENT OF LOWS AS WELL OF COURSE,
INITIALLY WITH A GREAT LAKES OR SOUTHERN CANADA LOW THAT OVERALL
SEEMED TO BOUNCE BACK SOUTH IN THE 12Z GUIDANCE BUT SEEMS TO HAVE
SHIFTED TO A NORTHERN TRACK WITH THE NEWER 00Z GUIDANCE--WHICH
COULD LEAD TO LESS INTERACTION WITH A SURFACE LOW FARTHER SOUTH.
THE WPC FORECAST FOR ALL THIS LEANED TOWARD THE ECMWF-LED PHASED
TROUGH SOLUTION YIELDING A POSSIBLY DEEP SURFACE LOW IN THE
NORTHEAST. THIS CLUSTER WAS CLOSER TO CONTINUITY AND THIS WAS A
SITUATION WHERE THE MODEL GUIDANCE BECOMES SO DIFFERENT THAT
ATTEMPTING TO BLEND MODELS FOR AN IN BETWEEN SOLUTION WAS NOT
REALLY POSSIBLE. THE SURFACE LOW TRACK TRENDED SLOWER THAN THE
PREVIOUS FORECAST. THIS SEEMS LIKE IT MIGHT BE A GOOD THING
CONSIDERING THE NEW 00Z MODELS CAME IN SLOWER, INCLUDING THE
ECMWF, THOUGH NOT AS SLOW WITH THE CLOSED LOW AS THE OTHER
GUIDANCE. PERHAPS MODEL GUIDANCE WILL GO TOWARD THIS MIDDLE GROUND
SOLUTION. THE MODEL BLEND WAS BASED ON A BLEND OF THE 12Z ECMWF,
12Z CMC, 12Z GFS (WHICH WAS MORE PROGRESSIVE/PHASED THAN THE OTHER
GFS RUNS), AND THE GEFS AND EC ENSEMBLE MEANS. FOR QPF, BLENDED IN
A CONSIDERABLE AMOUNT OF ECMWF AND EC MEAN SINCE THE 01Z NBM
FAVORS THE GEFS/GFS TYPE SOLUTIONS AND THE FRONTS/PRESSURES BLEND
LEANED AWAY FROM THAT.
AFTER THAT BY EARLY NEXT WEEK, THE OVERALL PATTERN IS LIKELY TO
FLATTEN BUT WITH SOME EMBEDDED SHORTWAVES, AND MORE LONGWAVE
RIDGING SHOULD COME INTO THE NORTHWEST AROUND DAY 7/MONDAY. SO THE
WPC FORECAST WAS BASED ON A BLEND OF THE DETERMINISTIC MODELS AND
MEANS GIVEN AVERAGE AGREEMENT.
..WEATHER/HAZARD HIGHLIGHTS
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 CONTINUE TO 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 STILL POTENTIAL FOR SIGNIFICANTLY
DIFFERENT PRECIPITATION COVERAGE AND AMOUNTS, WHICH WOULD INVOLVE
MORE RAINFALL ACROSS THE SOUTHERN TIER FROM TEXAS ACROSS THE LOWER
MISSISSIPPI VALLEY AND SOUTHEAST, AND LOWER TOTALS (WITH
WEAKER/MORE OFFSHORE LOW PRESSURE) FARTHER NORTH.
THEN BY NEXT WEEKEND, LAKE EFFECT SNOW IS ONCE AGAIN A POSSIBILITY
BEHIND THE UPPER TROUGH. THE NORTHWEST MAY SEE A BRIEF PERIOD OF
DRY WEATHER BUT MOISTURE COULD RETURN INTO WESTERN WASHINGTON AS
SOON AS THANKSGIVING DAY, WITH A SERIES OF FRONTAL SYSTEMS
SPREADING RAIN AND HIGH ELEVATION SNOW ACROSS MORE OF THE
NORTHWEST AND EVENTUALLY NORTHERN CALIFORNIA THROUGH THE WEEKEND,
WITH EXPANDING COVERAGE INTO THE GREAT BASIN/ROCKIES EARLY NEXT
WEEK.
TEMPERATURES ARE LIKELY TO TREND ABOVE AVERAGE ALONG THE WEST
COAST BY THURSDAY WITH PLUS 5-15F ANOMALIES EXPANDING INTO THE
ROCKIES AND CENTRAL U.S. LATER IN THE WEEK AS THE UPPER RIDGE
BUILDS IN. WESTERN U.S. TEMPERATURES SHOULD TREND BACK TOWARD
NORMAL AND PERHAPS BELOW AVERAGE BY EARLY NEXT WEEK GIVEN THE
LATEST FORECAST OF UPPER FLOW BECOMING MORE ZONAL AND EVENTUALLY
SWITCHING TO A TROUGH PATTERN. FARTHER EAST, 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 IS LIKELY TO MOVE THROUGH. ANOMALIES WILL DEPEND UPON
THE DETAILS OF THE EASTERN U.S. UPPER TROUGH AND POTENTIAL EAST
COAST SYSTEM, WHICH ARE STILL QUITE UNCERTAIN.
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, 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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