955
FXUS02 KWBC 200701
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST SUN NOV 20 2022
VALID 12Z WED NOV 23 2022 - 12Z SUN NOV 27 2022
...A COUPLE OF LOW PRESSURE SYSTEMS INCLUDING A POSSIBLE
NOR'EASTER COULD CAUSE MEANINGFUL PRECIPITATION ACROSS EASTERN
PARTS OF THE U.S. LATE THIS WEEK...
..OVERVIEW
A QUASI-ZONAL UPPER PATTERN WITH EMBEDDED SHORTWAVES COULD BE IN
PLACE ACROSS THE LOWER 48 AS THE MEDIUM RANGE PERIOD BEGINS
MIDWEEK, BUT THE PATTERN LOOKS TO QUICKLY AMPLIFY BY THANKSGIVING
DAY WITH UPPER TROUGH DEVELOPMENT IN THE CENTRAL U.S. AND RIDGING
BUILDING ACROSS THE WEST BEHIND IT. THE MAJORITY OF MODEL GUIDANCE
CONTINUES TO ADVERTISE THE TROUGH TRACKING EASTWARD THROUGH THE
WEEKEND, SUPPORTING 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). THIS PATTERN WOULD LEAD TO INCREASING CHANCES FOR
PRECIPITATION LATE THIS WEEK FOR THE EAST. HOWEVER, THERE ARE
LARGE SCALE UNCERTAINTIES REMAINING WITH WHAT BECOMES OF THE
TROUGH, AND SMALLER SCALE DIFFERENCES EVEN WITHIN THE MAJORITY
CLUSTER OF THE TROUGH/LOW TRACKS THAT LEAD TO LOW CONFIDENCE FOR
PRECIPITATION TYPES AND INTENSITY ACROSS THE EAST. BY LATE WEEK
INTO NEXT WEEKEND, EASTERN PACIFIC ENERGY COULD APPROACH THE WEST
COAST, BUT THIS ASPECT OF THE FLOW ALSO SHOWS CONSIDERABLE
DIFFERENCES WITH THE DETAILS AND THIS MAY PLAY A ROLE IN THE
FORECAST DIFFERENCES FARTHER EAST.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
MODEL GUIDANCE CONTINUES TO INDICATE THAT ENERGY WILL DIG AROUND
THE NORTHERN ROCKIES REGION TO DEVELOP A DEEPENING TROUGH
PROGRESSING INTO THE EASTERN U.S. BY THURSDAY WITH A RIDGE
AMPLIFYING IN THE WESTERN U.S. BEHIND IT. BUT BY THURSDAY AND
BEYOND, SPREAD INCREASES AMONGST MODEL GUIDANCE FOR THE FUTURE OF
THE TROUGH. WHILE THE MAJORITY OF MODEL GUIDANCE INCLUDING THE
ECMWF/CMC AND THE ENSEMBLE MEANS HAVE THE TROUGH TRACKING EASTWARD
WITH TIME, GFS RUNS THROW A WRENCH IN THE OVERALL CONSENSUS AS THE
12/18/00Z RUNS ALL SHOW THE POTENTIAL FOR ENERGY TO SPLIT OFF
SOUTHWARD AND FORM A CLOSED LOW SOMEWHERE IN THE SOUTH-CENTRAL
U.S. AND MEANDERING THERE AS THE LESS ENERGETIC NORTHERN STREAM
TRACKS QUICKLY EAST. GEFS MEMBERS SHOW QUITE A BIT OF SPREAD IN
THIS REGARD WITH SOME MORE LIKE THE OPERATIONAL GFS RUNS AND SOME
CLOSER TO THE MAJORITY CLUSTER OF OTHER GUIDANCE. AT THIS POINT IT
SEEMS WISEST TO CONSIDER THE GFS RUNS OUTLIERS AS THE
GFS/ECMWF/CMC ENSEMBLE MEANS, AS WELL AS THE DETERMINISTIC CMC AND
ECMWF, KEEP THE TROUGH PHASED AND DEEP ACROSS THE EAST. CHOOSING A
NON-GFS MODEL BLEND ALSO MAINTAINS WPC CONTINUITY BETTER. NOTE
THAT A GFS-TYPE EVOLUTION WOULD GREATLY SHIFT THE SURFACE PATTERN
AND EMPHASIS FOR HEAVIEST PRECIPITATION OVER THE CENTRAL/EASTERN
U.S. THE MAJORITY CLUSTER STILL INDICATES A SURFACE LOW PRESSURE
SYSTEM TRACKING 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. THERE ARE SOME CERTAINLY SOME DIFFERENCES BETWEEN LOWS
FROM ENSEMBLE MEMBERS AND THE DETERMINISTIC MODELS IN TERMS OF THE
EXACT TRACK AND STRENGTH OF EACH LOW, BUT MORE IN THE "TYPICAL
SPREAD" RANGE ONCE THE GFS IS EXCLUDED. BY LATE WEEK INTO THE
WEEKEND THE TROUGH SEEMS MOST LIKELY TO CONTINUE EASTWARD. NEWER
00Z ECMWF AND CMC RUNS SHOW THE TROUGH AXIS SHIFTING A LITTLE MORE
QUICKLY THROUGH THE EAST ALONG WITH THE SURFACE LOW EXITING FASTER
LATE WEEK COMPARED TO THEIR PREVIOUS RUNS.
THE OTHER MAJOR FORECAST ISSUE ARISING BY FRIDAY-SUNDAY INVOLVES
FLOW WITHIN THE EASTERN PACIFIC TROUGH. THERE HAS BEEN SOME
INCONSISTENCY IN GUIDANCE WITH A COUPLE OF ROUNDS OF ENERGY AND
WHETHER FLOW MAY SEPARATE WITHIN THE OVERALL TROUGH AS WELL AS HOW
ENERGY APPROACHES AND ENTERS NORTH AMERICA GIVEN THE OVERALL
RIDGE. GFS RUNS (PARTICULARLY THE 12Z) HAVE A POTENT SHORTWAVE
TRACKING EASTWARD AND PRESSING THE NORTHERN SIDE OF THE RIDGE
SOUTH THIS WEEKEND AS THE ECMWF DEFLECTS IT NORTHWARD. EARLIER ON
THERE ARE ALSO SOME SOUTHERN STREAM DIFFERENCES EVEN WITHIN THE
MAJORITY CLUSTER FOR ENERGY AROUND NORTHERN MEXICO OR SO, WITHOUT
CLEAR CONSENSUS YET AS THE 12Z ECMWF WENT WITHOUT A FEATURE THERE
WHILE THE 00Z ECMWF HAS IT WHILE THE CMC RUNS DO TOO. SO THESE
FEATURES REMAIN UNCERTAIN FOR NOW.
THUS THE WPC FORECAST BLEND BEGAN WITH A MULTI-MODEL DETERMINISTIC
BLEND FOR DAY 3/THURSDAY BUT WITH QUICK DECREASING AND EVENTUAL
REMOVAL OF THE 12/18Z GFS COMPONENTS GIVEN THEIR FLOW EVOLUTIONS
APPEAR LESS LIKELY. THE MORE AGREEABLE GEFS AND EC ENSEMBLE MEANS
WERE UTILIZED WITH INCREASING PROPORTIONS TO HALF BY DAY 6 AND
OVER HALF DAY 7 GIVEN THE INCREASING MODEL SPREAD EVEN WITHIN THE
MAJORITY CLUSTER. THIS MAINTAINED GOOD CONTINUITY WITH PREVIOUS
FORECASTS WHILE AWAITING ANY POTENTIALLY SIGNIFICANT SHIFTS IN THE
GUIDANCE.
..WEATHER/HAZARD HIGHLIGHTS
WEDNESDAY IS LIKELY TO BE FAIRLY DRY ACROSS THE LOWER 48, THOUGH
WITH PERHAPS SOME SHOWERS ACROSS FLORIDA AND THE SOUTHEASTERN
ATLANTIC COAST AS WELL AS A FEW RAIN AND SNOW SHOWERS IN NORTHERN
PARTS OF THE ROCKIES AND PLAINS. 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 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 A
MINORITY POTENTIAL FOR SIGNIFICANTLY DIFFERENT PRECIPITATION
COVERAGE AND AMOUNTS, WHICH COULD INVOLVE MORE RAINFALL ACROSS THE
SOUTHERN TIER AND LOWER TOTALS FARTHER NORTH. THEN BY NEXT
WEEKEND, LAKE EFFECT SNOW IS ONCE AGAIN A POSSIBILITY BEHIND THE
TROUGH, AND TROUGHING/ENERGY IN THE EASTERN PACIFIC COULD LEAD TO
PRECIPITATION COMING INTO THE PACIFIC NORTHWEST AND NORTHERN
CALIFORNIA.
TEMPERATURES IN THE MEDIUM RANGE PERIOD SHOULD BE OVERALL MORE
SEASONABLE COMPARED TO THOSE OF LAST WEEK. 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-SUNDAY AS
THE UPPER TROUGH IS LIKELY TO MOVE THROUGH.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page