395
FXUS02 KWBC 230700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST WED NOV 23 2022
VALID 12Z SAT NOV 26 2022 - 12Z WED NOV 30 2022
...MEANINGFUL PRECIPITATION IS POSSIBLE ACROSS EASTERN PARTS OF
THE U.S. THIS WEEKEND...
...SNOW IS LIKELY ACROSS HIGHER ELEVATIONS OF THE WEST EARLY THIS
WEEK AND MAY SPREAD INTO THE NORTH-CENTRAL U.S. BY
TUESDAY-WEDNESDAY...
..OVERVIEW
THE MEDIUM RANGE PERIOD WILL BEGIN SATURDAY WITH A CLOSED UPPER
LOW ATOP THE SOUTH-CENTRAL U.S., WHILE A SURFACE LOW PRESSURE
SYSTEM SHOULD LIFT QUICKLY FROM THE LOWER MISSISSIPPI VALLEY
TOWARD THE GREAT LAKES REGION THIS WEEKEND. THIS PATTERN WILL
PRODUCE WIDESPREAD RAIN CHANCES ACROSS THE SOUTHEAST, WHERE SOME
LOCALIZED FLOODING MAY BE POSSIBLE, AND FARTHER NORTH ACROSS THE
MISSISSIPPI VALLEY INTO THE OHIO/TENNESSEE VALLEYS, SHIFTING INTO
THE MID-ATLANTIC AND NORTHEAST LATER SATURDAY INTO SUNDAY. SOME
PRECIPITATION MAY FALL AS SNOW IN HIGHER ELEVATIONS OF THE
INTERIOR NORTHEAST. BY EARLY NEXT WEEK, THE UPPER PATTERN LOOKS TO
HAVE A BRIEF TRANSITION TOWARD ZONAL FLOW BEFORE TROUGHING DIGS
INTO 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-WEDNESDAY, WITH SOME SNOW POSSIBLE NORTH
AND WEST OF THE LOW FOR THE NORTHERN PLAINS INTO MINNESOTA, AND
RAIN AHEAD OF A TRAILING COLD FRONT IN THE EAST-CENTRAL CONUS.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
WHILE MODEL GUIDANCE AGREES IN PRINCIPLE FOR AN UPPER LOW CENTERED
SOMEWHERE NEAR THE ARK-LA-TEX FOR DAY 3/SATURDAY, THERE ARE
DIFFERENCES IN POSITION THAT MAY APPEAR RELATIVELY MINOR BUT
CONSIDERABLY AFFECT THE PLACEMENT OF THE PRECIPITATION AND THE
SURFACE LOW/FRONT POSITIONS. IN A FLIP FROM THE PAST SEVERAL DAYS,
THE 12Z ECMWF AND EC ENSEMBLE MEAN WERE AMONG THE SLOWEST
SOLUTIONS OF THE 12/18Z MODEL CYCLE. THE 12Z CMC WAS FASTEST WHILE
THE GFS RUNS AND UKMET SEEMED LIKE THE BEST IN BETWEEN POSITION IN
TERMS OF THE 12/18Z GUIDANCE. THE NEW 00Z CMC HAS SLOWED DOWN
SLIGHTLY CLOSER TO CONSENSUS COMPARED TO ITS PREVIOUS RUN, THE 00Z
GFS AND UKMET BOTH SLOWED A BIT AS WELL, AND THE 00Z ECMWF MAY BE
A TAD FASTER THAN THE 12Z RUN BUT STILL ON THE SLOW SIDE. SO WHILE
GUIDANCE MAY BE CONVERGING SOMEWHAT SLOWER THERE ARE STILL SOME
POSITIONAL DIFFERENCES. THE WPC FORECAST ATTEMPTED TO TAKE A
MIDDLE GROUND APPROACH WITH A BLEND OF THE VARIOUS DETERMINISTIC
GUIDANCE FOR THIS FEATURE, WHICH MEANT BLENDING SOME EC/EC
ENSEMBLE MEAN QPF INTO THE NBM (WHICH IS DESIGNED MORE LIKE THE
GEFS MEAN, SO ON THE FAST SIDE) TO SLOW IT DOWN.
MEANWHILE, THERE ARE SOME MODEL DIFFERENCES REGARDING FLOW COMING
INTO THE WEST. THE NON-GFS MODELS INDICATE AN INITIAL SHORTWAVE
COMING INTO CALIFORNIA SATURDAY-SUNDAY (THOUGH THE 12Z ECMWF WAS
LESS AGGRESSIVE WITH IT THAN ITS PREVIOUS RUNS) AND THEN GENERALLY
MORE TROUGHING INFLUENCE REACHING THE NORTHERN HIGH PLAINS BY 12Z
MONDAY COMPARED TO THE RIDGIER GFS. BUT AT LEAST GUIDANCE IS
REASONABLY AGREEABLE WITH MORE POTENT ENERGY DIGGING INTO THE WEST
MONDAY-TUESDAY AND SHIFTING INTO THE CENTRAL U.S. WEDNESDAY. GFS
AND EC RUNS INDICATE DISPARATE ENERGY WITH A SEPARATE TROUGH
COMING IN BEHIND BY WEDNESDAY, WHILE THE CMC IS COMBINING THOSE
FEATURES MORE, WHICH WILL LIKELY TAKE SOME TIME TO BE RESOLVED
GIVEN THE ENERGY WILL TRACK AROUND TYPICALLY UNCERTAIN AREAS
ROUNDING ARCTIC/ALASKA/NORTHERN PACIFIC RIDGING. OVERALL THE WPC
FORECAST TRENDED TOWARD MORE UTILIZATION OF ENSEMBLE MEANS TO
ABOUT HALF BY DAY 6-7, TRYING TO MITIGATE THE INDIVIDUAL MODEL
SPREAD. BUT EVEN WITH SOME MODEL DIFFERENCES THERE IS THE
POTENTIAL FOR A LOW PRESSURE SYSTEM TO STRENGTHEN IN THE CENTRAL
HIGH PLAINS AND TRACK TOWARD THE MIDWEST TUESDAY-WEDNESDAY.
..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 AND PRODUCE
WIDESPREAD RAIN CHANCES THIS WEEKEND. SOME LOCALLY HEAVY RAINFALL
MAY BE POSSIBLE IN THE SOUTHEAST AND INTO THE SOUTHERN
APPALACHIANS AND PIEDMONT ON SATURDAY, WHICH COULD CAUSE ISOLATED
FLASH FLOODING IF RAIN RATES ARE HIGH ENOUGH. PRECIPITATION IS
LIKELY TO SPREAD ACROSS THE MIDDLE MISSISSIPPI VALLEY AND
OHIO/TENNESSEE VALLEYS ON SATURDAY AS WELL, AND INTO THE
MID-ATLANTIC AND NORTHEAST LATE SUNDAY INTO MONDAY. 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.
THE PACIFIC NORTHWEST INTO THE NORTHERN ROCKIES CAN EXPECT SOME
LIGHT TO MODERATE PRECIPITATION ON SATURDAY 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 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. WHILE THE DETAILS ARE UNCERTAIN,
THE HIGHEST PROBABILITIES FOR HEAVY SNOW SHOULD INITIALLY BE
ACROSS THE CASCADES AND SIERRA NEVADA, WITH SOME SNOW IN THE
WASATCH/ROCKIES AS WELL. THEN WITH THE POTENTIAL FOR LOW PRESSURE
SYSTEM DEVELOPMENT IN THE CENTRAL U.S., SNOW IS POSSIBLE ON THE
BACKSIDE OF THE LOW AS IT TRACKS NORTHEASTWARD INTO THE MIDWEST
TUESDAY-WEDNESDAY. LOWER ELEVATION AREAS THAT COULD SEE SNOW WOULD
INCLUDE EASTERN MONTANA INTO THE DAKOTAS AND MINNESOTA. THIS IS AT
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. THIS WEEKEND BEHIND THE INITIAL UPPER LOW,
WHILE MILDER THAN NORMAL TEMPERATURES PARTICULARLY IN TERMS OF
LOWS ARE POSSIBLE IN THE EAST. 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 10-20F BELOW AVERAGE MAY FOCUS ACROSS THE
NORTHERN HIGH PLAINS. MEANWHILE, THE SOUTH-CENTRAL AND
EAST-CENTRAL U.S. COULD SEE ABOVE NORMAL TEMPERATURES AHEAD OF THE
WESTERN 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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page