797
FXUS02 KWBC 240709
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
208 AM EST THU NOV 24 2022
VALID 12Z SUN NOV 27 2022 - 12Z THU DEC 01 2022
...SNOW IS LIKELY ACROSS HIGHER ELEVATIONS OF THE WEST EARLY NEXT
WEEK AND MAY SPREAD INTO THE NORTH-CENTRAL U.S. BY
MONDAY-WEDNESDAY...
...WIDESPREAD, POTENTIALLY HEAVY RAINFALL COULD AFFECT THE
EAST-CENTRAL U.S. TUESDAY-WEDNESDAY AHEAD OF A COLD FRONT...
..OVERVIEW
A FAIRLY PROGRESSIVE UPPER PATTERN IS IN STORE FOR MUCH OF NEXT
WEEK. THE UPPER LOW LOCATED IN THE SOUTHERN PLAINS DURING THE
SHORT RANGE PERIOD THAT HAS BEEN VERY TRICKY TO FORECAST FOR
SHOULD BE LIFTING INTO THE MID-MISSISSIPPI VALLEY AS THE MEDIUM
RANGE PERIOD BEGINS EARLY SUNDAY, WHILE A SURFACE LOW ALSO TRACKS
QUICKLY NORTHWARD ACROSS THE NORTHEASTERN QUADRANT OF THE U.S. AND
SPREADS PRECIPITATION ALONG THE LOW TRACK AND THE TRAILING COLD
FRONT IN THE MID-ATLANTIC TO SOUTHEAST ON SUNDAY. MOST
PRECIPITATION WILL BE RAIN, BUT THERE COULD BE SOME LIGHT SNOW IN
HIGHER ELEVATIONS OF THE INTERIOR NORTHEAST. THEN TROUGHING IS SET
TO DIG ACROSS THE WESTERN U.S. MONDAY-TUESDAY, INCREASING
PRECIPITATION CHANCES THERE. AS THE TROUGH SHIFTS EASTWARD, THE
CURRENT FORECAST SHOWS A CONSOLIDATING SURFACE LOW PRESSURE SYSTEM
MAY SHIFT INTO THE MIDWEST FOR TUESDAY-THURSDAY, WITH SOME SNOW
POSSIBLE NORTH AND WEST OF THE LOW FOR THE NORTHERN PLAINS INTO
THE UPPER MIDWEST, AND POTENTIAL FOR HEAVY RAINFALL AHEAD OF A
TRAILING COLD FRONT IN THE EAST-CENTRAL CONUS.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
THE INITIAL UPPER AND SURFACE LOWS TO BEGIN THE PERIOD 12Z SUNDAY
CONTINUED TO TREND SLOWER OVERALL IN THE 12/18Z MODEL CYCLE THAT
WAS AVAILABLE FOR THE OVERNIGHT FORECAST--THOUGH THE UKMET WAS A
BIT OF A SOUTH OUTLIER. THE NEWER 00Z MODELS ARE NOT TOO DIFFERENT
FROM THE EARLIER CONSENSUS, THOUGH THE CMC MOVED FROM THE EASTERN
SIDE OF THE SPREAD TO SLOWER AT 00Z. THUS THIS FORECAST PULLED THE
LOW AND FRONTAL PLACEMENT AS WELL AS THE QPF A BIT FARTHER SOUTH
AND WEST COMPARED TO CONTINUITY GIVEN THE MODEL TREND. THE
DIFFERENCES WERE NOT HUGE, BUT FOR DAY 3 PERHAPS A BIT LARGER
CHANGES THAN NORMAL.
ATTENTION THEN TURNS TO THE WEST WITH ROUNDS OF TROUGHING
EXPECTED. EVEN BY DAY 3/SUNDAY A SHORTWAVE LOOKS TO BE OVER THE
FOUR CORNERS REGION, PASSING QUICKLY INTO THE EAST-CENTRAL U.S. BY
MONDAY. THERE IS GENERAL AGREEMENT FOR ENERGY TO DIG AND DEEPEN
LARGER SCALE TROUGHING IN THE WEST MONDAY-TUESDAY WITH JUST SOME
MINOR SHORTWAVE DIFFERENCES. SLIGHTLY LARGER DIFFERENCES ARISE BY
AROUND WEDNESDAY AS THE TROUGH EJECTS INTO THE CENTRAL U.S.,
PARTICULARLY AS THE 12Z CMC IS FASTER THAN THE BETTER CONSENSUS OF
THE GFS/ECMWF RUNS, BUT ALSO WITH THE DETAILS OF POTENTIAL MINOR
STREAM SEPARATION--THOUGH GUIDANCE DOES NOT CURRENTLY SHOW AN
UPPER LOW FORMING AND CUTTING OFF WITHIN THE TROUGH. THERE IS ALSO
SOME VARIABILITY WITH WHAT MAY BE A COMPLEX SURFACE LOW EVOLUTION
IN THE CENTRAL U.S., WHICH WILL DEPEND ON DETAILS OF THE ENERGY
THAT MAY TAKE MORE TIME TO RESOLVE. THESE DIFFERENCES ARE PRETTY
TYPICAL FOR THIS FORECAST LEAD TIME THOUGH, AND IT APPEARS THAT
THE NEWER 00Z GUIDANCE SHOWS BETTER AGREEMENT FOR THE EVENTUAL
TRACK OF THE CONSOLIDATED LOW INTO SOUTHEASTERN CANADA BY DAY
7/THURSDAY. MODELS ARE ALSO REASONABLY CONSISTENT WITH SHOWING
ANOTHER BOUT OF TROUGHING COMING INTO THE NORTHWEST LATE IN THE
PERIOD.
THUS THE WPC FORECAST UTILIZED A BLEND OF THE DETERMINISTIC
GUIDANCE LED BY THE 18Z GFS AND 12Z ECMWF FOR THE EARLY PART OF
THE PERIOD, WITH GRADUAL TRANSITION TO ABOUT HALF THE GEFS AND EC
ENSEMBLE MEAN GUIDANCE BY DAYS 6-7. THIS SERVED TO MAINTAIN SOME
STRENGTH OF SYSTEMS WHILE ALSO SMOOTHING OUT INDIVIDUAL MODEL
DIFFERENCES.
..WEATHER/HAZARD HIGHLIGHTS
GULF MOISTURE IS FORECAST TO STREAM INTO PARTS OF THE CENTRAL AND
EASTERN U.S. AHEAD OF THE UPPER AND SURFACE LOWS MOVING FROM THE
MID-MISSISSIPPI VALLEY NORTHEASTWARD AND PRODUCE WIDESPREAD RAIN
CHANCES ON SUNDAY FOR THE EAST. 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
WHERE SNOW COULD FALL. SINCE THE LOW AND FRONTS WILL BE MOVING
QUICKLY BY THEN, THIS SHOULD LESSEN OVERALL FLOODING CONCERNS.
THE PACIFIC NORTHWEST INTO THE NORTHERN ROCKIES CAN EXPECT
INCREASING PRECIPITATION ON SUNDAY IN CONJUNCTION WITH A COUPLE OF
FRONTAL SYSTEMS. PRECIPITATION IS THEN FORECAST TO SPREAD
SOUTHWARD ACROSS CALIFORNIA AND EASTWARD INTO THE GREAT BASIN AND
ROCKIES BY MONDAY AS THE NOTED UPPER TROUGH CONTINUES DIGGING INTO
THE REGION. LOWER ELEVATION RAIN AND HIGHER ELEVATION SNOW WILL BE
LIKELY. AT THIS POINT IT LOOKS LIKE THE HEAVIEST SNOW SHOULD BE
ACROSS THE CASCADES INTO THE WASATCH TO WIND RIVER MOUNTAINS AND
THE NORTHERN/CENTRAL ROCKIES, WITH MORE UNCERTAINTY FOR HEAVY
PRECIPITATION IN CALIFORNIA/THE SIERRA NEVADA. YET ANOTHER ROUND
OF TROUGHING COULD INCREASE CHANCES FOR ADDITIONAL PRECIPITATION
IN THE NORTHWEST BY WEDNESDAY-THURSDAY.
LOW PRESSURE SYSTEM DEVELOPMENT/CONSOLIDATION STILL LOOKS LIKELY
IN THE CENTRAL U.S. BY AROUND MIDWEEK, BRINGING PRECIPITATION
CHANCES TO CENTRAL AND EASTERN PORTIONS OF THE LOWER 48.
WIDESPREAD, POTENTIALLY HEAVY RAINFALL LOOKS POSSIBLE ACROSS PARTS
OF THE MISSISSIPPI VALLEY INTO THE OHIO/TENNESSEE VALLEYS AND
APPALACHIANS. THERE ALSO REMAINS POTENTIAL FOR SNOW ON THE
BACKSIDE OF THE LOW AS IT TRACKS NORTHEASTWARD INTO THE MIDWEST
TUESDAY-WEDNESDAY, WITH A POSSIBLE FOCUS OF SNOW FROM EASTERN
MONTANA INTO THE DAKOTAS AND THE UPPER MIDWEST. THIS IS TOWARD THE
END OF THE MEDIUM RANGE PERIOD THOUGH SO THE DETAILS OF THE
FORECAST MAY NEED TO CHANGE WITH TIME, SO STAY TUNED TO FUTURE
FORECASTS.
SLIGHTLY COOLER THAN NORMAL HIGHS COULD LINGER IN THE
SOUTH-CENTRAL U.S. ON SUNDAY, WHILE MILDER THAN NORMAL
TEMPERATURES ARE POSSIBLE IN THE EAST WITH ANOMALIES FOR LOWS
AROUND 10-20F AND HIGHS AROUND 5-15F ABOVE NORMAL. BUT MORE
WIDESPREAD COOLER THAN NORMAL TEMPERATURES ARE LIKELY TO EXPAND
ACROSS THE WESTERN HALF OF THE U.S. MONDAY-WEDNESDAY AS DEEPENING
TROUGHING TAKES HOLD THERE. ANOMALIES OF 15-25F BELOW AVERAGE MAY
FOCUS ACROSS THE NORTHERN HIGH PLAINS MONDAY AND SPREAD SOUTH INTO
THE GREAT BASIN AND CENTRAL HIGH PLAINS TUESDAY. MEANWHILE, THE
SOUTH-CENTRAL AND EAST-CENTRAL U.S. COULD SEE ABOVE NORMAL
TEMPERATURES AHEAD OF THE WESTERN TROUGH. THEN THE COLD AIR
CONTINUES MARCHING EASTWARD TO FLIP MOST AREAS TO BELOW NORMAL BY
NEXT THURSDAY.
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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