351
FXUS02 KWBC 241806
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
106 PM EST THU NOV 24 2022
VALID 12Z SUN NOV 27 2022 - 12Z THU DEC 01 2022
...SNOW LIKELY ACROSS HIGHER ELEVATIONS OF THE WEST INTO NEXT
WEEK...
...HEAVY RAIN AND SEVERE WEATHER POSSIBLE ACROSS PARTS OF THE
SOUTH AND INTO THE OHIO VALLEY TUESDAY-WEDNESDAY NEXT WEEK...
..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 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 AND AMPLIFY ACROSS THE WESTERN U.S.
MONDAY-TUESDAY, MOUNTAIN SNOW CHANCES SHIFTING FROM THE PACIFIC
NORTHWEST TO THE CENTRAL GREAT BASIN AND ROCKIES. AS THE TROUGH
SHIFTS EASTWARD, THE CURRENT FORECAST SHOWS A CONSOLIDATING
SURFACE LOW PRESSURE SYSTEM TO SHIFT FROM THE CENTRAL PLAINS INTO
THE MIDWEST FOR TUESDAY-WEDNESDAY, WITH SOME SNOW POSSIBLE NORTH
AND WEST OF THE LOW FOR THE NORTHERN PLAINS INTO THE UPPER
MIDWEST. CONFIDENCE CONTINUES TO INCREASE FOR SEVERE WEATHER AND
HEAVY RAINFALL POTENTIAL AHEAD OF THIS SYSTEM ACROSS PARTS OF THE
SOUTH AND INTO THE OHIO VALLEY.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
LATEST 00Z/06Z GUIDANCE SHOWS FAIRLY GOOD AGREEMENT ON THE INITIAL
UPPER LOW AS IT SHIFTS INTO THE MIDWEST ON SUNDAY. BEHIND THIS,
ANOTHER MUCH WEAKER SHORTWAVE SHOULD QUICKLY MOVE THROUGH THE
SOUTHERN PLAINS INTO THE MIDWEST SUNDAY-MONDAY. THOUGH THE 00Z CMC
WAS A SLOWER OUTLIER, THE 12Z RUN TODAY DID SPEED UP AND SEEMS
MORE IN LINE.
ATTENTION THEN SHIFTS OUT WEST AS A TROUGH BEGINS TO DIG THROUGH
THE WEST MONDAY-TUESDAY, AND INTO THE CENTRAL AND EASTERN U.S.
WEDNESDAY-THURSDAY. GUIDANCE AND ENSEMBLES SHOW MINOR TIMING
DIFFERENCES EARLY IN THE WEEK WITH THIS POTENTIALLY HIGH IMPACT
SYSTEM, BUT DO SHOW SOME MEANINGFUL DIFFERENCES IN AMPLITUDE. THE
00Z (AND NEW 12Z) RUNS OF THE CMC AND UKMET ARE NOTABLY LESS
AMPLIFIED AND FASTER (LATER PERIOD) THAN THE GFS AND ECMWF. THE
ENSEMBLES ALSO SHOW SOME VARIABILITY BUT WOULD FAVOR A BIT MORE
AMPLIFIED SOLUTION. MINOR DIFFERENCES IN THE UPPER PATTERN BECOME
MORE IMPORTANT AT THE SURFACE WITH A COMPLEX SURFACE LOW EVOLUTION
IN THE CENTRAL U.S.. THESE DIFFERENCES ARE PRETTY TYPICAL FOR THIS
FORECAST LEAD TIME THOUGH, AND THE DAYTIME GUIDANCE DOES SHOW
SOMEWHAT 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, BUT WITH
MORE DIFFERENCES IN THE TIMING.
THE WPC FORECAST USED A GENERAL BLEND OF THE DETERMINISTIC
GUIDANCE LED BY THE 06Z GFS AND 00Z ECMWF FOR THE EARLY PART OF
THE PERIOD. LEFT THE CMC AND UKMET OUT AFTER DAY 4 IN FAVOR OF THE
ENSEMBLE MEANS IN ORDER TO DEPICT A MORE AMPLIFIED TROUGH OVER THE
WEST. THE FORECAST GRADUALLY TRANSITIONED TO HALF GEFS/EC ENSEMBLE
MEAN WITH THE GFS AND ECMWF BY DAYS 6-7. THIS HELPED TO MITIGATE
SOME OF THE MODEL DETAILS DIFFERENCES AND ALSO MAINTAINED GOOD
AGREEMENT WITH THE OVERNIGHT WPC FORECAST PACKAGE.
..WEATHER/HAZARD HIGHLIGHTS
GULF MOISTURE IS FORECAST TO STREAM INTO THE 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, WITH THE EXCEPTION OF HIGHER
ELEVATIONS OF THE INTERIOR NORTHEAST WHERE SNOW COULD FALL. A
FAIRLY PROGRESSIVE SYSTEM 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, WITH EVEN SOME POTENTIAL
FOR LOWER ELEVATION SNOWS TOO.
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 THE EASTERN
DAKOTAS INTO THE UPPER MIDWEST. SUFFICIENT MOISTURE AND
INSTABILITY IN THE WARM SECTOR COULD LEAD TO SEVERE WEATHER, WITH
SPC ALREADY HIGHLIGHTING THE CHANCE IN THEIR OUTLOOK FOR NEXT
TUESDAY ACROSS PARTS OF EASTERN TEXAS INTO THE LOWER MISSISSIPPI
VALLEY. DETAILS REGARDING THIS POTENTIALLY HIGH IMPACT SYSTEM WILL
VARY AS IT GETS CLOSER IN TIME, SO STAY TUNED TO FUTURE FORECAST
UPDATES.
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. 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.
SANTORELLI/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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