613
FXUS62 KGSP 101946
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
246 PM EST SUN NOV 10 2024
SYNOPSIS
COLD AIR DAMMING WILL CONTINUE TODAY, MAINTAINING CLOUDY CONDITIONS,
AHEAD OF A COLD FRONT WHICH WILL RAMP UP RAIN CHANCES THROUGH
TOMORROW. DRY HIGH PRESSURE WILL RETURN FOR TUESDAY AND WEDNESDAY,
AND ANOTHER COLD FRONT WILL CROSS THE AREA THURSDAY.
NEAR TERM /THROUGH MONDAY/
AS OF 211 PM SUNDAY: MOIST ISENTROPIC LIFT ASSOCIATED WITH A WARM
CONVEYOR BELT OF SORTS HAS FORCED THE DEVELOPMENT OF EXTENSIVE LOW
CLOUDINESS AND PATCHES OF LIGHT RAIN ACROSS THE REGION, LOCKING IN
A COLD AIR DAMMING WEDGE EAST OF THE MTNS. FORCING SLOWLY IMPROVES
THROUGH THE AFTERNOON, WHICH SHOULD EXPAND THE AREA WHERE LIGHT
RAIN IS FALLING NORTHWARD ACROSS THE REST OF THE WESTERN PIEDMONT
AND FOOTHILLS. MOST LOCATIONS GET A LIKELY PRECIP PROB THROUGH THE
EARLY EVENING IN RESPONSE. NOTE THIS IS ONE OF THOSE SITUATIONS
WHERE WE HAVE A RELATIVELY HIGH PRECIP PROB BUT RELATIVELY LOW
QPF. TEMPS MIGHT ONLY CREEP UP ANOTHER DEGREE OR TWO BEFORE DUSK.
THE MOIST UPGLIDE APPEARS TO MAXIMIZE AROUND 00Z MONDAY ALONG
WITH THE BEST DPVA AND UPPER DIVERGENCE, AFTER WHICH THAT FORCING
MOVES OFF TO THE NORTHEAST AND THE ISENTROPIC LIFT BECOMES MORE
SHALLOW. THUS, PRECIP PROBS WERE RAISED TONIGHT BUT SLOWLY DIMINISH
INTO THE LATE EVENING. HOWEVER, THE UPGLIDE NEVER REALLY ENDS AT
LOW LEVELS INTO THE EARLY MORNING HOURS, SO DRIZZLE COULD PERSIST
OVERNIGHT IN MANY PLACES. MEANWHILE, LOW PRESSURE MOVING ACROSS
THE GREAT LAKES AND OVER ONTARIO WILL PUSH A SFC FRONT TOWARD THE
MTNS FROM THE WEST. THE FLOW ALOFT AHEAD OF THIS FRONT SHOULD VEER
MORE SOUTHWESTERLY AND KEEP WEAK WARM ADVECTION IN PLACE, WHICH
ALONG WITH THICK CLOUD COVER WILL PROBABLY KEEP TEMPS NEARLY STEADY
TONIGHT. THE FRONT SHOULD REACH THE MTNS BY DAYBREAK. AS THE FRONT
GETS PUSHED OVER THE MTNS AND THEN OUT OVER THE PIEDMONT MONDAY
MORNING, THE FORCING WILL CONTINUE TO WEAKEN AND PRECIP COVERAGE
WILL ALSO DIMINISH. SO, APART FROM SOME LIKELY ALONG THE TN BORDER
EARLY ON, THE WEAKENING KEEPS PROBS IN THE CHANCE RANGE EAST OF THE
MOUNTAINS. THE GUIDANCE MANAGES TO DEVELOP SOME WEAK INSTABILITY
MAINLY S/E OF I-85 IN THE MORNING, SO AN ISOLATED THUNDERSTORM
CAN'T BE RULED OUT, BUT IN GENERAL THE SITUATION DOESN'T LOOK
VERY FAVORABLE FOR STORMS. THE BETTER FORCING IS GONE BY THE
TIME INSTABILITY MAXIMIZES IN THE MID/LATE AFTERNOON, WHILE THE
BOUNDARY MIGHT ALSO BE SOUTHEAST OF THE FCST AREA. TEMPS WILL BE
TRICKY AND WILL DEPEND ON HOW QUICKLY THE FLOW CAN VEER AND BECOME
MORE DOWNSLOPE, CONTRIBUTING TO THE LOW CLOUDS SCATTERING OUT IN
TIME. IF THAT HAPPENS, WE WOULD SEE A FAIRLY NICE AFTERNOON WITH
TEMPS REBOUNDING 15 DEGREES OR MORE COMPARED TO THIS AFTERNOON.
SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/
AS OF 1237 PM EDT SUNDAY: BY MONDAY EVENING, THE FRONTAL CIRCULATION
WILL BE NEAR THE SOUTHEASTERN EXTENT OF THE FORECAST AREA, IF NOT
ENTIRELY EAST OF THE AREA, ALLOWING A DRIER AIR MASS TO FILTER IN
THROUGH THE OVERNIGHT FOR ALL ZONES, EXCEPT SOME ISOLATED AREAS OF
THE MOUNTAINS WHERE LINGERING UPSLOPE MOISTURE MAY CONTINUE TO
PRODUCE SHOWERS AND CLOUDS. THE ASSOCIATED SLUG OF POSTFRONTAL CAA
WILL BE SHORT-LIVED, BUT WILL OCCUR OVERNIGHT AND THE FIRST PART OF
TUESDAY, RESULTING IN TEMPERATURES MONDAY NIGHT FALLING INTO THE LOW
50S OR UPPER 40S, AND ONLY CLIMBING INTO THE MID OR UPPER 60S ON
TUESDAY AFTERNOON. TUESDAY NIGHT, AS ANY LINGERING POSTFRONTAL WIND
SUBSIDES, CONDITIONS SHOULD SET UP FOR EXCELLENT RADIATIVE COOLING,
AND TEMPERATURES WILL DROP TO THE LOW 40S OR EVEN UPPER 30S OUTSIDE
THE MOUNTAINS...WHILE THE HIGHEST ELEVATIONS COULD SEE FREEZING
TEMPERATURES.
WINDS WILL VEER AROUND TO EASTERLY LEADING UP TO DAYBREAK WEDNESDAY
AS HIGH PRESSURE DRIFTS OFF THE NEW ENGLAND COAST...REMAINING THAT
WAY THROUGH THE END OF THE PERIOD. 850MB WINDS WILL PICK UP OUT OF
THE SOUTH, AND MODEST ISENTROPIC ASCENT WILL RESULT IN ENHANCED
CLOUD COVER THROUGH THE DAY. THIS LOOKS TO SET UP ANOTHER CLASSICAL
CAD CONFIGURATION, SUCH THAT THERE'S A <25% CHANCE THAT MOST
LOCATIONS WILL MAKE IT OUT OF THE 50S WEDNESDAY, WITH THE EXCEPTION
OF THE SAVANNAH RIVER VALLEY AND EXTREME SOUTHERN UPSTATE, WHICH
COULD SEE 60 DEGREES OR SO.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
AS OF 1253 PM EDT SUNDAY: THURSDAY REMAINS MURKIER. THE ADVANCE OF
A PREFRONTAL TROUGH CONTINUES TO BE DEPICTED BY OPERATIONAL MODELS,
WHICH IN THEORY SHOULD HELP SCATTER OUT THE RESIDUAL WEDGE FROM THE
BOTTOM UP. BUT, MODELS ARE NOTORIOUSLY OVERAGGRESSIVE IN SCATTERING
OUT WEDGES. EITHER WAY, THE ARRIVAL OF THE FRONT THURSDAY EVENING
SHOULD SCOUR OUT THE WEDGE...GIVING US ANOTHER SLUG OF CAA LASTING
THROUGH EARLY FRIDAY AS HIGH PRESSURE BUILDS IN FROM THE NORTHWEST.
MODEL SOLUTIONS BEGIN TO DIVERGE WILDLY PAST THIS POINT. THERE'S A
ROUGH CONSENSUS THAT HIGH PRESSURE WILL PERSIST THROUGH FRIDAY AND
THE FIRST HALF OF SATURDAY, WHILE A HIGHLY-AMPLIFIED TROUGH DEVELOPS
OVER THE FOUR CORNERS REGION AND CENTRAL GREAT PLAINS. SOME
GUIDANCE MAINTAINS HIGH PRESSURE RIGHT UP THROUGH SUNDAY, BUT MORE
PROGRESSIVE SOLUTIONS TAKE THE TROUGH INTO THE OHIO VALLEY BY
SUNDAY, WHICH RESULTS IN A RETURN OF MOISTURE TO THE AREA THROUGH
THE END OF THE WEEKEND. SO, CONFIDENCE REMAINS LOW ON THE EVOLUTION
OF THINGS PAST FRIDAY OR SO.
AVIATION /20Z SUNDAY THROUGH FRIDAY/
AT KCLT AND ELSEWHERE: SEEING THE EFFECTS OF THE COLD AIR DAMMING
WEDGE SLOWLY TAKE OVER ACROSS THE REGION EARLY THIS AFTERNOON, WITH
LIGHT PRECIP AND LOW CLOUDS EXPANDING NORTHEASTWARD TO ENCOMPASS
MOST OF THE REGION. THIS DEVELOPMENT SHOULD ESTABLISH THE NE
WIND SLOWLY BACKING TO MORE NORTHARLY. KCLT MAY BE IN-AND-OUT OF
THE MVFR OVER THE NEXT FEW HOURS, BUT THE REST OF THE TERMINALS
SHOULD BE IN THE CEILING RESTRICTION FROM NOW THROUGH THE PASSAGE
OF THE COLD FRONT MONDAY MORNING. THE CEILING/VIS IS EXPECTED
TO DROP DOWN THROUGH MVFR AND INTO IFR AFTER IT GETS DARK, WITH
IFR/LIFR PREVAILING THROUGH AT LEAST DAYBREAK MONDAY AS LOW LEVEL
SOUTHERLY MOIST UPGLIDE CONTINUES ABOVE THE SHALLOW NORTHEASTERLY
SFC LAYER. THE WINDS ALOFT DO NOT APPEAR TO BE STRONG ENOUGH FOR
LLWS AT THIS POINT. MODEL GUIDANCE SHOWS THE FRONTAL ZONE MOVING
THROUGH IN THE MIDDLE OF THE DAY, WHICH SUGGESTS THAT WE SHOULD
BE ABLE TO STRIP OUT THE LOWEST CLOUD DECK, BUT WILL NOT SCATTER
OUT CLOUDS AS QUICKLY AS GUIDANCE DOES TOWARD THE END OF THE
PERIOD. EXPECT IT WILL TAKE A FEW MORE HOURS TO GET THE DOWNSLOPE
BEHIND THE FRONT TO DO THE TRICK. WIND WILL BE TRICKY MONDAY
MORNING, WITH A SHIFT TO SW IMMEDIATELY AHEAD OF THE BOUNDARY,
AND THEN MORE SW AFTER ITS PASSAGE.
OUTLOOK: DRY AND MOSTLY VFR WEATHER EXPECTED TUE-WED. MOISTURE
BEGINS TO RETURN FROM THE SOUTHWEST ON THURSDAY.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...MPR
NEAR TERM...PM
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...PM
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