402
FXUS02 KWBC 181902
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST FRI NOV 18 2022
VALID 12Z MON NOV 21 2022 - 12Z FRI NOV 25 2022
..OVERVIEW
A MORE ZONAL CONFLUENT FLOW REGIME IS FORECAST TO ESTABLISH ITSELF
ACROSS THE NORTHERN TIER STATES BY THE START OF THE MEDIUM-RANGE
PERIOD AS AN UPPER TROUGH DE-AMPLIFIES FURTHER AND EXITS THE
NORTHEAST. THIS WILL LEAD TO MODERATING TEMPERATURES TO EXPAND
EASTWARD FROM THE PLAINS TO THE EAST COAST THROUGH MIDWEEK.
MEANWHILE, A LOW PRESSURE WAVE FORMING ALONG A STALLED FRONT IS
FORECAST TO BRING HEAVY RAIN POTENTIAL ALONG THE EAST COAST OF
FLORIDA EARLY NEXT WEEK. FOR THE WEST COAST, MODELS ARE GENERALLY
TRENDING TOWARD BUILDING A STRONGER RIDGE LATE NEXT WEEK WHILE
DEVELOPING A BETTER-DEFINED TROUGH DOWNSTREAM OVER THE GREAT
PLAINS. THIS PATTERN WILL TEND TO INHIBIT HEAVY PRECIPITATION
FROM REACHING THE PACIFIC NORTHWEST WHILE SPREADING MOISTURE
NORTHWARD FROM THE GULF WITH UNSETTLED WEATHER LIKELY EXPANDING
ACROSS THE EASTERN HALF OF THE COUNTRY BY THE THANKSGIVING HOLIDAY
WEEKEND. BY FRIDAY, THERE APPEARS TO BE THE POTENTIAL FOR THE
UPPER TROUGH TO INTERACT AND AMPLIFY THE LOW PRESSURE WAVE OFF THE
SOUTHEAST U.S. AND THEN TRACK IT UP THE EAST COAST. HOWEVER,
DETAILS OF THIS INTERACTION ARE QUITE UNCERTAIN AT THIS TIME.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
MUCH OF THE UNCERTAINTY WILL BE TOWARD THE END OF NEXT WEEK WITH
THE POTENTIAL FOR CYCLOGENESIS TO OCCUR NEAR THE EAST COAST. THIS
IS IN RESPONSE TO A GENERAL MODEL TREND TO BUILD A STRONGER RIDGE
NEAR THE WEST COAST WHILE PROMOTING A MORE AMPLIFIED TROUGH
DOWNSTREAM ACROSS THE PLAINS STATES. THE LAST COUPLE OF ECMWF
RUNS HAVE BEEN MORE AGGRESSIVE IN THIS REGARD ALTHOUGH EARLIER
RUNS FROM BOTH THE ECMWF AND THE GFS HAVE HINTED AT THIS
POSSIBILITY. THE 12Z GFS KEEPS THE TROUGH PROGRESSIVE WHEREAS THE
CMC DOES NOT FAVOR THE PHASING OF THE UPPER TROUGH WITH THE LOW
OFF THE SOUTHEAST U.S.
THE WPC FORECAST WAS BASED ON A BLEND OF THE 06Z GFS/GEFS WITH THE
00Z ECMWF/EC MEAN WITH SMALL CONTRIBUTIONS FROM THE 00Z CMC/CMC
MEAN, BUT LEANING TOWARD THE EC MEAN BY DAY 7.
..WEATHER/HAZARD HIGHLIGHTS
CHILLY TEMPERATURES THIS WEEKEND ARE EXPECTED TO CONTINUE INTO THE
FIRST PART OF NEXT WEEK, BUT SHOULD BE GRADUALLY MODERATING. LOW
TEMPERATURES ON MONDAY ARE FORECAST TO BE 10-15F BELOW NORMAL FROM
THE LOWER MISSISSIPPI VALLEY THROUGH THE EAST, BUT ONLY A FEW
DEGREES BELOW AVERAGE TUESDAY AND NEAR TO ABOVE (ESPECIALLY ACROSS
THE SOUTHEAST) NORMAL AS THE WEEK PROGRESSES, THOUGH THE INTERIOR
NORTHEAST MAY SEE ANOTHER BOUT OF COLD AIR THURSDAY-FRIDAY. HIGH
TEMPERATURES COULD REMAIN COOL FOR SOUTHERN TEXAS ON MONDAY, WITH
HIGHS IN THE 50S BELOW NORMAL BY 15-25F, WHICH SHOULD GRADUALLY
WARM THROUGH MIDWEEK AS WELL. THE EAST MAY SEE SOME BELOW NORMAL
HIGHS ONCE AGAIN BY THE LATTER PART OF NEXT WEEK. MEANWHILE THE
WEST COULD SEE INCREASING COVERAGE OF ABOVE AVERAGE TEMPERATURES
BY THURSDAY-FRIDAY GIVEN THE RIDGE ALOFT.
SOME LINGERING LAKE EFFECT SNOW IS POSSIBLE INTO MONDAY DOWNWIND
OF ESPECIALLY THE LOWER GREAT LAKES, BUT THE BULK OF THE
SIGNIFICANT SNOW FOR PLACES LIKE BUFFALO, NEW YORK IS FORECAST TO
FALL DURING THE SHORT RANGE PERIOD. MEANWHILE, MULTIPLE FRONTAL
SYSTEMS MOVING INTO THE NORTHWESTERN U.S. COULD CAUSE ROUNDS OF
PRECIPITATION THERE NEXT WEEK, WITH HIGHER ELEVATION SNOW. HOWEVER
THERE IS STILL A FAIR DEGREE OF UNCERTAINTY OVER THE SOUTHWARD
EXTENT AND INTENSITY OF RAIN/MOUNTAIN SNOW ON A DAY-TO-DAY BASIS.
SURFACE HIGH PRESSURE DOMINATING INTERIOR PARTS OF THE WEST IS
LIKELY TO KEEP THAT REGION FAIRLY DRY. MEANWHILE, A SHORTWAVE AND
MOISTURE ADVECTING FROM THE GULF OF MEXICO COULD LEAD TO SHOWERS
AND SOME THUNDERSTORMS ACROSS TEXAS AND POTENTIALLY FARTHER EAST
ACROSS THE SOUTHEAST EARLY IN THE WEEK. EASTERLY FLOW AND A
FRONTAL SYSTEM MEANDERING NEAR THE FLORIDA PENINSULA WILL ENHANCE
SHOWER/THUNDERSTORM COVERAGE THERE, AND ISOLATED FLASH FLOODING
CANNOT BE RULED OUT ESPECIALLY OVER URBAN AREAS. THEN BY THE
LATTER HALF OF THE WEEK, MOISTURE COULD STREAM NORTH AHEAD OF THE
POTENTIAL CENTRAL U.S. TROUGH AND INCREASE CHANCES FOR
PRECIPITATION ACROSS THE EASTERN HALF OF THE U.S., THOUGH THE
DETAILS REMAIN UNCERTAIN AND WILL DEPEND ON EVOLUTION OF THE UPPER
AND SURFACE SYSTEMS.
KONG/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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