068
FXUS02 KWBC 220700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST TUE NOV 22 2022
VALID 12Z FRI NOV 25 2022 - 12Z TUE NOV 29 2022
...MEANINGFUL PRECIPITATION IS POSSIBLE ACROSS THE SOUTHEASTERN
U.S. LATE THIS WEEK AND POTENTIALLY INTO THE NORTHEAST EARLY NEXT
WEEK...
..OVERVIEW
FORTUNATELY, MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT WITH
THE OVERALL PATTERN ACROSS THE COUNTRY LATE THIS WEEK INTO EARLY
NEXT WEEK. UNFORTUNATELY, MODELS HAVE TRENDED TOWARD THE SOLUTION
THAT HAS NOT BEEN FAVORED IN THE WPC FORECAST OVER THE LAST FEW
DAYS SINCE THIS PATTERN WAS FORMERLY IN THE MINORITY. THE NEW
MODEL GUIDANCE AND THE WPC FORECAST INDICATE THAT A CLOSED UPPER
LOW WILL TRACK ACROSS THE SOUTH-CENTRAL U.S. ALONG WITH A
DEVELOPING SURFACE LOW PRESSURE SYSTEM FOR FRIDAY-SATURDAY. THIS
SHOULD LEAD TO WIDESPREAD RAIN CHANCES ACROSS THE SOUTHERN HALF OF
THE PLAINS AND MISSISSIPPI VALLEY AND FARTHER EAST INTO THE
SOUTHEAST, OHIO AND TENNESSEE VALLEYS, AND THE EAST COAST FOR LATE
WEEK INTO THE WEEKEND. THERE IS SOME CHANCE OF SNOW ON THE
BACKSIDE OF THE CLOSED LOW IN THE SOUTHERN HIGH PLAINS ON FRIDAY.
BY EARLY NEXT WEEK, THE UPPER PATTERN IS LIKELY TO TRANSITION TO
MORE ZONAL FLOW, BUT WITH TROUGHING AND FRONTS COMING INTO THE
NORTHWEST PROMOTING INCREASING PRECIPITATION CHANCES ACROSS THE
WEST COAST INTO THE GREAT BASIN AND ROCKIES SUNDAY-TUESDAY.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
IT HAS BEEN QUITE DIFFICULT TO MAKE A DETERMINISTIC FORECAST THE
PAST FEW DAYS GIVEN THE MODEL SPREAD AND NO NOTABLE MIDDLE GROUND
TYPE SOLUTIONS BETWEEN A CLUSTER OF MODELS LED BY THE ECMWF AND EC
ENSEMBLE MEMBERS THAT SHOWED A PHASED UPPER TROUGH MARCHING
THROUGH THE CENTRAL-EASTERN U.S. ALONG WITH A STRENGTHENING
NORTHEAST SURFACE LOW AROUND THE THURSDAY-SATURDAY TIMEFRAME, AND
ONE LED BY THE GFS/SOME GEFS MEMBERS/UKMET THAT SPILLED ENERGY
INTO THE SOUTHERN STREAM ENOUGH TO CREATE A CLOSED UPPER LOW OVER
TEXAS OR SO WITH A SLOWER TRACK. THE SIGNIFICANT DIFFERENCES
SEEMED TO ARISE FROM ENERGY IN THE EASTERN PACIFIC HANDLED
DIFFERENTLY BY EACH MODEL. THE WPC FORECAST HAD BEEN LEANING
TOWARD THE FORMER CLUSTER WHICH HAD FIT CONTINUITY BETTER.
HOWEVER, NOW PRETTY MUCH ALL THE GUIDANCE HAS TRENDED TOWARD THE
SLOW SOUTHERN STREAM UPPER LOW TYPE OF SOLUTION. THERE STILL
REMAIN SOME WIGGLES THE PLACEMENT OF THE UPPER LOW FROM MODEL TO
MODEL AND RUN TO RUN, BUT THERE IS MUCH LESS SPREAD THAN THERE HAS
BEEN. THUS THE WPC FORECAST, AFTER A TREND IN THAT DIRECTION BY
THE PREVIOUS SHIFT, WAS PRETTY MUCH "ALL IN" ON SHOWING A CLOSED
LOW OVER THE SOUTHERN PLAINS DAY 3/FRIDAY AND A SLIGHT SHIFT
EASTWARD DAY 4/SATURDAY. THIS AFFECTED THE FRONTAL POSITIONS AND
QPF AND OTHER WEATHER GRIDS WITH SOME NECESSARY CHANGES TO
CONTINUITY. THE FORECAST BLEND FOR FRONTS/PRESSURES WAS BASED ON A
MULTI-MODEL DETERMINISTIC BLEND OF THE 12/18Z GUIDANCE TO PROVIDE
A MIDDLE GROUND BETWEEN SLIGHTLY SLOWER OR FASTER SOLUTIONS.
FARTHER WEST, THERE CONTINUES TO BE A GENERAL TREND TOWARD
TROUGHING IN THE WEST EARLY NEXT WEEK. SOME GUIDANCE LIKE THE 12Z
ECMWF WAS AGGRESSIVE IN BRINGING IN A SHORTWAVE TO THE WESTERN
U.S. BY SUNDAY BEFORE THE MAIN TROUGH FEATURE, AND THERE ARE
CERTAINLY MODEL DIFFERENCES THAT BASICALLY AVERAGE OUT TO ZONAL
FLOW, BEFORE BETTER AGREEMENT FOR TROUGHING COMING IN AROUND
TUESDAY--THOUGH OF COURSE THERE ARE SOME MODEL DIFFERENCES IN THE
DETAILS OF HOW FAST THE TROUGH MOVES INLAND AND ITS DEPTH ETC. THE
WPC FORECAST UTILIZED A DETERMINISTIC MODEL AND GEFS/EC ENSEMBLE
MEAN BLEND (JUST OVER HALF ENSEMBLE MEANS) FOR THE LATTER PART OF
THE PERIOD TO ALLEVIATE THESE DIFFERENCES.
..WEATHER/HAZARD HIGHLIGHTS
AHEAD OF THE CLOSED UPPER LOW IN THE SOUTHERN PLAINS AND A COUPLE
OF LOW PRESSURE/FRONTAL SYSTEMS, GULF MOISTURE IS LIKELY TO STREAM
INTO CENTRAL AND EASTERN PARTS OF THE LOWER 48. PRECIPITATION IS
EXPECTED FROM TEXAS/OKLAHOMA (WHICH COULD BE IN THE FORM OF SNOW
FOR SOME PORTIONS) WITH RAIN AND PERHAPS SOME THUNDERSTORMS
FARTHER EAST ACROSS THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST ON
FRIDAY. LOCALLY HEAVY RAINFALL CAUSING ISOLATED FLASH FLOODING IS
POSSIBLE. THE LOW IS FORECAST TO TRACK NORTHEASTWARD AND SPREAD
PRECIPITATION ACROSS THE MIDDLE MISSISSIPPI VALLEY AND
OHIO/TENNESSEE VALLEYS AS WELL ON SATURDAY, AND INTO THE EASTERN
SEABOARD BY SUNDAY. WITH THIS LOW TRACK, MOST AREAS ARE LIKELY TO
SEE RAIN RATHER THAN WINTRY PRECIPITATION, BUT HIGHER ELEVATIONS
OF THE INTERIOR NORTHEAST COULD BE AN EXCEPTION. THERE COULD BE
SOME LAKE EFFECT RAIN/SNOW SHOWERS EARLY NEXT WEEK BEHIND THE
UPPER TROUGH.
THE PACIFIC NORTHWEST INTO THE NORTHERN ROCKIES CAN EXPECT SOME
LIGHT TO MODERATE PRECIPITATION LATE THIS WEEK IN CONJUNCTION WITH
A COUPLE OF FRONTAL SYSTEMS. AS UPPER TROUGHING SHIFTS INTO THE
REGION, PRECIPITATION IS FORECAST TO SPREAD SOUTHWARD ACROSS
CALIFORNIA AND INTO THE GREAT BASIN AND ROCKIES FOR EARLY NEXT
WEEK. LOWER ELEVATION RAIN AND HIGHER ELEVATION SNOW WILL BE
LIKELY.
THE UPPER LOW NOW FORECAST ATOP THE SOUTH-CENTRAL U.S. LATE WEEK
WILL CAUSE SOME COOLER THAN NORMAL TEMPERATURES THERE,
PARTICULARLY IN TERMS OF HIGHS THAT COULD BE 10-20F BELOW NORMAL
MAINLY IN TEXAS ON FRIDAY. MEANWHILE LOWS ARE LIKELY TO BE WARMER
THAN NORMAL FOR THE CENTRAL/EASTERN GULF COAST STATES AND
NORTHWARD INTO THE TENNESSEE/OHIO VALLEYS FRIDAY GIVEN THE GULF
INFLOW AHEAD OF THE UPPER LOW, SHIFTING INTO THE EAST BY SUNDAY.
SLIGHTLY MILDER THAN NORMAL HIGH TEMPERATURES FOR THE
NORTH-CENTRAL U.S. FRIDAY-SATURDAY SHOULD MODERATE TO NEAR NORMAL
BY SUNDAY. AS UPPER TROUGHING INFLUENCES THE WEST EARLY NEXT WEEK,
EXPANDING COVERAGE OF BELOW AVERAGE TEMPERATURES IS LIKELY THERE,
WHILE THE SOUTH-CENTRAL U.S. FLIPS TO SLIGHTLY ABOVE NORMAL AHEAD
OF THE TROUGH.
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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