770
FXUS02 KWBC 190708
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
208 AM 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 AND A
ROUND OF PRECIPITATION IN THE PACIFIC NORTHWEST. BY THE LATTER
HALF OF THE WEEK, THE PATTERN IS FORECAST TO AMPLIFY CONSIDERABLY
WITH A POTENT UPPER TROUGH MOVING ACROSS THE CENTRAL U.S. INTO THE
EAST, WHILE RIDGING BUILDS BEHIND ACROSS THE WEST. AT THE SURFACE,
THIS WILL LEAD TO A LOW PRESSURE/FRONTAL SYSTEM TRAVERSING THE
CENTRAL U.S. AND CROSSING THE GREAT LAKES WHILE THE WESTERN
ATLANTIC LOW PRESSURE SYSTEM LIFTS NORTH. THESE FEATURES WILL
SUPPORT INCREASING CHANCES FOR PRECIPITATION LATE NEXT WEEK, BUT
GIVEN THE MODEL SPREAD IN THE EXACT LOW TRACKS, THERE IS
UNCERTAINTY REGARDING PRECIPITATION TYPES AND AREAS OF HEAVIER
AMOUNTS ACROSS THE EAST.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
FORTUNATELY MODEL GUIDANCE IS SHOWING BETTER AGREEMENT THAN IT WAS
A DAY OR SO AGO WITH TROUGHING AMPLIFYING SOMEWHAT AGGRESSIVELY IN
THE CENTRAL U.S. BY WEDNESDAY-THURSDAY AS SHORTWAVE ENERGY DIVES
FROM THE NORTHEASTERN PACIFIC INTO SOUTHWESTERN CANADA AND INTO
THE NORTHERN ROCKIES AND HIGH PLAINS, CAUSING THE TROUGH TO DIG.
THERE REMAIN SOME DIFFERENCES WITH THE PLACEMENT OF THE TROUGH
WITH TIME AND POTENTIAL FOR A CLOSED LOW TO FORM WITHIN IT, BUT
THESE ARE RELATIVELY MINOR FOR THE MEDIUM RANGE PERIOD. A SURFACE
LOW SHOULD ALSO TRACK TOWARD THE UPPER MIDWEST WHILE THE PATTERN
WOULD ALSO SUPPORT CYCLOGENESIS NEAR THE EAST COAST. WHILE THERE
IS SOME MODEL SPREAD FOR THE TRACKS OF EACH SURFACE LOW, AT LEAST
MODELS ARE REASONABLY AGREEABLE FOR THESE SYSTEMS TO FORM. THERE
MAY BE SOME DIFFERENCES IN THE POTENTIAL FOR THEIR PHASING.
MEANWHILE MODEL GUIDANCE ALSO SHOWS GOOD AGREEMENT FOR AN OVERALL
UPPER TROUGH ACROSS THE WEST FOR THE LATTER PART OF THE WEEK. THE
FEATURE WITH PERHAPS THE MOST MODEL SPREAD IS EASTERN PACIFIC
UPPER ENERGY THAT COULD FORM A SOUTHERN STREAM CLOSED LOW BUT WITH
A LARGE VARIETY AMONG MODELS/ENSEMBLE MEMBERS FOR WHERE IT TRACKS.
THE UKMET HAD SEEMED TO BE AN OUTLIER WITH ITS DRIFT WEST INTO THE
PACIFIC RATHER THAN GRADUALLY EAST, UNTIL THE NEW 00Z ECMWF TOOK
THE SAME SORT OF TRACK AS THE UKMET HAD BEEN TAKING.
THE AMPLIFYING PATTERN AND REASONABLE AGREEMENT ON THE LARGE SCALE
MEANT THE WPC FORECAST COULD BE BASED ON A BLEND OF THE
DETERMINISTIC 12/18Z GFS, 12Z CMC, AND 12Z ECMWF RUNS THROUGH DAY
5, WITH INCORPORATION OF THE EC/GEFS ENSEMBLE MEANS BY DAYS 6-7.
THIS APPROACH LED TO BETTER DEFINITION OF THE EASTERN U.S. SURFACE
LOWS THOUGH WITH THE CAVEAT THAT THEIR TRACKS MAY CHANGE.
..WEATHER/HAZARD HIGHLIGHTS
PRECIPITATION IS POSSIBLE ACROSS THE PACIFIC NORTHWEST AND FARTHER
EAST INTO THE NORTHERN ROCKIES ON TUESDAY-WEDNESDAY WITH A FRONTAL
SYSTEM PASSING THROUGH. MODEL TRENDS HAVE REMAINED GENERALLY DRIER
FOR THE NORTHWEST AND INTO THE ROCKIES LATER IN THE WEEK AS
SURFACE HIGH PRESSURE AND UPPER RIDGING BUILD IN. SANTA ANA WINDS
ACROSS SOUTHERN CALIFORNIA MAY BE A CONCERN THOUGH
TUESDAY-WEDNESDAY. SHOWERS AND THUNDERSTORMS ARE POSSIBLE ACROSS
FLORIDA AND INTO THE SOUTHEAST THROUGH TUESDAY-WEDNESDAY AS A LOW
PRESSURE SYSTEM ALONG A FRONT MEANDERS NEARBY AND FOCUSES MOISTURE
ACROSS THOSE AREAS. ISOLATED FLASH FLOODING COULD BE A CONCERN
PARTICULARLY ACROSS URBAN AREAS.
THEN AS THE UPPER PATTERN AMPLIFIES LATER IN THE WEEK BY
THANKSGIVING DAY AND BEYOND, GULF MOISTURE WILL 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 HOPEFULLY COMES INTO BETTER
CONSENSUS WITH LOW TRACKS AND TEMPERATURES.
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 FORECAST TO WARM ACROSS THE WEST COAST BY
MIDWEEK WITH ABOVE AVERAGE TEMPERATURES BY AROUND 5-15F 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 ARE FORECAST FOR THE MISSISSIPPI
VALLEY TOWARD THE EAST COAST FRIDAY-SATURDAY AS THE TROUGH MOVES
THROUGH.
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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