554
FXUS02 KWBC 221908
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
207 PM 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
MODEL GUIDANCE HAS REMAINED IN BETTER AGREEMENT WITH THE OVERALL
PATTERN ACROSS THE COUNTRY LATE THIS WEEK INTO EARLY NEXT WEEK.
THE WPC FORECAST INDICATES 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
THE MODEL GUIDANCE HAS REMAINED IN RELATIVELY GOOD AGREEMENT
OVERNIGHT IN TERMS OF THE INITIAL OVERALL UPPER-LEVEL PATTERN
GIVEN THE NOTED UNCERTAINTY THE PAST FEW DAYS. THIS IS
SPECIFICALLY TRUE FOR THE TREND OF THE ECMWF TO FOLLOW THE OTHER
DETERMINISTIC GUIDANCE IN THE DEVELOPMENT AND LATER PROGRESSION OF
A CLOSED UPPER-LEVEL LOW OVER THE SOUTHERN PLAINS. AS A
COMPARISON, THE GFS HAS REMAINED CONSISTENT IN THIS SOLUTION OVER
MULTIPLE RUNS THE PAST DAY WHILE THE ECMWF HAS FURTHER CONVERGED
TOWARDS THIS SOLUTION AS OF THE 00Z RUN IN BOTH TIMING AND IN
DEPICTING AN INCREASINGLY DEEPER LOW. HOWEVER, THERE ARE A NUMBER
OF MORE DETAILED SPECIFICS IN THE PHASING AND AMPLITUDE OF WAVES
LATER INTO THE PERIOD THAT STILL LEADS TO AREAS OF MORE
SIGNIFICANT UNCERTAINTY. GIVEN THE SIMILAR TREND ACROSS THE
DETERMINISTIC GUIDANCE FOR THE CLOSED LOW OVER THE SOUTHERN
PLAINS, THE WPC FORECAST INITIALLY STARTS WITH AN EVEN BLEND OF
THE 00Z ECMWF/UKMET/CMC AND 06Z GFS. THE GUIDANCE STARTS TO
DIVERGE IN THE HANDLING OF A DEVELOPING SHORTWAVE UPSTREAM OVER
THE WESTERN U.S. WHILE THE TIMING AND AMPLITUDE DIFFER SOME, THE
00Z ECMWF/UKMET/CMC ALL DEPICT A DEVELOPING WAVE OVER THE
NORTHWEST WHILE THE 00Z/06Z RUNS OF THE GFS WERE RELATIVE OUTLIERS
IN COMPARISON WITH ONLY A MODEST, SUBTLE WAVE DEPICTED. THUS, TO
MAINTAIN THE PROGRESSION OF THE LOW TO THE EAST WHILE INCLUDING A
SLIGHTLY MORE AMPLIFIED SHORTWAVE IN THE WEST, THE 00Z ECENS MEAN
WAS PROGRESSIVELY INCREASED IN THE WPC FORECAST BLEND AS THE 06Z
GFS WAS DECREASED GIVEN THE RELATIVELY SIMILAR EVOLUTION OF THE
EASTERN LOW IN THE OTHER DETERMINISTIC GUIDANCE. INCORPORATING
MORE OF THE 00Z ECENS MEAN ALSO HELPED TO MAINTAIN A LOWER
AMPLITUDE SHORTWAVE GIVEN THE LINGERING UNCERTAINTY IN THIS
SOLUTION IN BOTH THE PROGRESSION AND ENERGY OF THE WAVE AND
SUBSEQUENT DOWN-SCALED EFFECTS ON THE WEATHER PATTERN. LATER IN
THE PERIOD, THE FOCUS TURNS TOWARDS THE WEST AGAIN AS A HIGHLY
AMPLIFIED, POSITIVELY TILTED UPPER-LEVEL TROUGH DEVELOPS UPSTREAM
OFF THE WEST COAST BEFORE DIGGING INTO THE SOUTHWEST. BOTH THE 06Z
GFS AND 00Z CMC ARE MORE AMPLIFIED THAN THE 00Z ECMWF, WHILE THE
00Z GEFS AND ECENS MEANS ARE ALSO EXPECTEDLY LESS AMPLIFIED
COMPARED TO THE DETERMINISTIC GUIDANCE. THE WPC FORECAST BLEND IN
THE LATE PERIOD INCLUDED INCREASED RELIANCE ON THE MEANS GIVEN
GREATER UNCERTAINTY BUT STILL RELIED ON A CONTRIBUTION OF THE
DETERMINISTIC GUIDANCE TO PROVIDE A BIT MORE AMPLIFICATION OF THE
TROUGH OVER THE SOUTHWEST GIVEN HOW FAR SOUTH THE TROUGH DIGS IN
THE 06Z GFS AND 00Z CMC. USE OF THE ENSEMBLE MEANS HELPS TO
ADDRESS AN ADDITIONAL LINGERING AREA OF UNCERTAINTY WITH ANOTHER
SUBSEQUENT UPSTREAM WAVE DEVELOPING LATE IN THE PERIOD. THE MEANS
INCLUDE THE POTENTIAL OF A SHORTWAVE OVER THE PACIFIC OFF BRITISH
COLUMBIA BUT AGAIN ALLOW FOR A LESS AMPLIFIED PATTERN UNTIL MORE
SPECIFICS ON THE TIMING AND PROGRESSION OF THESE WAVES CAN BE
RESOLVED.
THE PRECIPITATION FORECAST INCLUDED AN INCREASE IN RAIN AMOUNTS
FROM THE SOUTHEAST UP THE EAST COAST IN THE WARM SECTOR OF THE
EASTERN U.S. SYSTEM COMPARED TO THE PREVIOUS FORECAST AS BOTH THE
NBM AND DETERMINISTIC GUIDANCE HAD TRENDED UPWARD ACROSS THIS
REGION. IN COMPARISON, PRECIPITATION AMOUNTS CAME DOWN A BIT
ACROSS THE MIDWEST AND OHIO VALLEY. A GENERAL MODEL BLEND KEPT
THINGS RELATIVELY SIMILAR DURING THE MIDDLE OF THE PERIOD BETWEEN
THE EASTERN U.S. SYSTEM AND INCREASE IN PRECIPITATION SPREADING
ACROSS THE WEST. LATE IN THE PERIOD, THE TREND IN THE GUIDANCE WAS
FOR HIGHER PRECIPITATION AMOUNTS IN THE PACIFIC NORTHWEST.
..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. RAIN AND PERHAPS
SOME THUNDERSTORMS ARE EXPECTED FROM TEXAS/OKLAHOMA EAST ACROSS
THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST ON FRIDAY. LOCALLY
HEAVY RAINFALL CAUSING ISOLATED FLASH FLOODING IS POSSIBLE.
BENEATH THE UPPER-LEVEL LOW AND ALONG THE BACKSIDE OF THE
SUBSEQUENT SURFACE LOW TRACK, THERE HAS BEEN AN INCREASING TREND
IN THE POTENTIAL FOR AT LEAST A FEW INCHES OF SNOW FROM EASTERN
NEW MEXICO THROUGH THE TEXAS PANHANDLE AND INTO WESTERN OKLAHOMA.
THE LOW IS FORECAST TO TRACK NORTHEASTWARD AND SPREAD
PRECIPITATION UP THE EAST COAST AS WELL AS ACROSS THE MIDDLE
MISSISSIPPI VALLEY AND OHIO/TENNESSEE VALLEYS INTO THE WEEKEND.
LOCALLY HEAVY RAINFALL IS AGAIN POSSIBLE ON SATURDAY FOR PORTIONS
OF THE SOUTHERN APPALACHIANS AND PIEDMONT. 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 ALSO 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. PRECIPITATION IS FORECAST TO SPREAD
SOUTHWARD ACROSS CALIFORNIA AND INTO THE GREAT BASIN AND ROCKIES
FOR EARLY NEXT WEEK AS THE NOTED UPPER TROUGH BEGINS TO DIG INTO
THE REGION. LOWER ELEVATION RAIN AND HIGHER ELEVATION SNOW WILL BE
LIKELY. SOME HEAVIER SNOW AMOUNTS MAY BE POSSIBLE FOR THE CASCADES
AND THE SIERRA NEVADA.
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, WHICH WILL HELP CONTRIBUTE TO THE
POSSIBILITY OF SNOW OVER THE REGION AS THE GUIDANCE HAS TRENDED
COLDER. 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.
PUTNAM/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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