926
FXUS62 KGSP 260238
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1038 PM EDT SUN OCT 25 2020
SYNOPSIS
COOL HIGH PRESSURE WILL BUILD SOUTH INTO THE REGION THROUGH
TONIGHT, THEN WEAKEN ON MONDAY AS COOL TEMPERATURES LINGER. EXPECT A
RETURN TO ABOVE NORMAL TEMPERATURES FOR TUESDAY AND WEDNESDAY BEFORE
THE NEXT ROUND OF RAIN APPEARS BY THURSDAY AHEAD OF A STRONG UPPER
LOW. AS THIS LOW MOVES OFF THE EAST COAST LATE FRIDAY, COOL, DRY
HIGH PRESSURE WILL DROP TEMPERATURES A LITTLE BELOW NORMAL FOR NEXT
WEEKEND.
NEAR TERM /THROUGH MONDAY/
AS OF 1030 PM EDT: RADAR ECHOES HAVE REALLY DIMINISHED OVER THE
LAST COUPLE OF HOURS, BUT THERE IS STILL A FEW PATCHES OF DRIZZLE
OUT THERE, ESPECIALLY NEAR THE ESCARPMENT. THE POPS/WX WERE UPDATED
TO REFLECT THE LOWER COVERAGE, WITH MAINLY JUST SLGT CHC TO LOW-END
CHC FOR THE NEXT FEW HOURS. ALSO MADE SOME TWEAKS TO THE TEMP TRENDS
TO LINE UP WITH OBS.
OTHERWISE, THE UPPER SHORTWAVE WILL CONTINUE TO MOVE NE OF THE AREA
AND OFFSHORE WITH HEIGHTS GRADUALLY RECOVERING THROUGH THE REMAINDER
OF THE PERIOD AS UPPER RIDGING BUILDS TO OUR SOUTH. AT THE SFC, THE
CAD WEDGE IS EXPECTED TO STRENGTHEN OVER THE NEXT SEVERAL HOURS AS
ITS PARENT HIGH SLIDES FARTHER EAST AND WEAK LOW PRESSURE EVENTUALLY
LIFTS NORTHWARD JUST OFF THE SE COAST. THE PARENT HIGH WILL BE
FAIRLY TRANSITORY AND IS EXPECTED TO MOVE EAST OF NOVA SCOTIA
TOMORROW AFTN, THEREBY ERODING THE CAD LATER TOMORROW AS THE PERIOD
ENDS AND ALLOWING SOME CLEARING ACROSS MOST OF THE FCST AREA. WITH
THE CAD IN PLACE, MIN TEMPS EARLY TOMORROW WILL BE COOLER THAN THEY
HAVE BEEN THE PAST FEW DAYS (ALTHOUGH STILL ABOVE NORMAL), BUT HIGHS
TOMORROW WILL BE BELOW NORMAL.
SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/
AS OF 100 PM SUNDAY: WEAK HIGH PRESSURE WILL REMAIN IN PLACE OVER THE
REGION INTO WEDNESDAY. A RATHER DEEP UPPER RIDGE WILL BE CENTERED OFF
THE SOUTHEAST COAST, WHICH WILL ALLOW WEAK MOIST UPGLIDE TO CONTINUE
OVER THE HIGH; MOSTLY CLOUDY CONDITIONS ARE THUS EXPECTED MONDAY
NIGHT. THE DISSIPATION OF THOSE CLOUDS TUESDAY, COMBINED WITH THE
RELATIVELY LARGE THICKNESSES, WILL SUPPORT TEMPS REBOUNDING SEVERAL
DEGREES ABOVE NORMAL. TUESDAY NIGHT A MOIST WARM FRONT WILL SHIFT
NORTH FROM THE GULF COAST, AS TC ZETA MOVES NORTHWARD AND A CUTOFF
UPPER LOW MOVES ACROSS WEST TEXAS. PRECIP MAY SPREAD INTO SOME OF OUR
AREA AS SOON AS LATE TUESDAY NIGHT; CHANCES INCREASE THRU WEDNESDAY.
FCST MAX TEMPS FALL BACK SLIGHTLY, MAINLY ON ACCOUNT OF CLOUDIER
SKIES.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
AS OF 200 PM SUNDAY: ZETA WILL BE CAUGHT BETWEEN THE ATLANTIC RIDGE
AND THE UPPER LOW, SO IT GENERALLY CAN BE EXPECTED TO CURVE EAST
AFTER LANDFALL. THE OPERATIONAL GFS AND ITS ENSEMBLE MEMBERS ARE ON
THE EASTERN SIDE OF THE ENVELOPE, CARRYING THE CIRCULATION CLOSE TO
THE SOUTHERN APPALACHIANS, WHEREAS THE EC AND ITS ENSEMBLE ARE MORE
TO THE NORTHWEST AND INLAND. THE CANADIAN IS CLOSER TO THE GFS AT THE
MOMENT, BUT WITH SIMILAR STORMS EARLIER THIS SEASON IT FLIP-FLOPPED
BETWEEN THE GFS AND EC CAMPS, SO I WOULDN'T PLACE TOO MANY CHIPS ON
THAT SO-CALLED CONSENSUS. THE GFS AND CANADIAN TRACKS DO SUGGEST
STRONGER LOW- TO MID-LEVEL WINDS PASSING OVER OUR AREA. THAT WOULD
RESULT IN STRONGER UPSLOPE AND FRONTOGENETIC EFFECTS, IN TURN
RESULTING IN GREATER QPF POTENTIAL. THE RESULTANT 0-1KM AND 0-3KM
BULK SHEAR WOULD ALSO POINT TO A TC TORNADO THREAT WEDNESDAY NIGHT.
EVEN IF ZETA STAYS FURTHER WEST, WE MAY NOT BE TOTALLY OUT OF THE
WOODS FOR SEVERE WX: PRACTICALLY ALL THE AVAILABLE GUIDANCE SHOWS THE
UPPER LOW TRACKING ACROSS THE TENNESSEE VALLEY LATE THURSDAY, AND
MORE OR LESS THROUGH OUR CWA THURSDAY NIGHT. A SLIGHTLY UNSTABLE WARM
SECTOR APPEARS LIKELY TO PRECEDE THE LOW AND ATTENDANT COLD FRONT,
WITH ENOUGH SHEAR TO PROMPT A HIGH-SHEAR/LOW-CAPE DAMAGING WIND
THREAT. BOTH SEVERE AND FLOOD THREATS APPEAR MARGINAL AND LOCALIZED
AT THIS POINT, BUT CONFIDENCE HAS INCREASED TO THE POINT THAT WE WILL
START TO RAMP UP MESSAGING THE POTENTIAL IMPACTS.
COOLER AIR AND A DRYING TREND SHOULD ARRIVE ON FRIDAY IN THE WAKE OF
THE FRONT, WITH TEMPS FALLING A LITTLE BELOW NORMAL. MOST LIKELY
PRECIP WILL END BEFORE ENOUGH COOLING OCCURS FOR A P-TYPE CHANGEOVER;
THE REMAINING MOISTURE LIKELY WILL BE VERY SHALLOW ANYWAY. SOME FROST
COULD OCCUR SATURDAY AND SUNDAY MORNINGS, AT LEAST IN THE COOLER
MOUNTAIN/FOOTHILL LOCATIONS.
AVIATION /03Z MONDAY THROUGH FRIDAY/
AT KCLT AND ELSEWHERE: WIDESPREAD IFR CIGS EXPECTED TONIGHT THRU AT
LEAST THE FIRST HALF OF MONDAY, AS COLD AIR DAMMING PERSISTS. THERE
ARE PATCHES OF -RA AND DZ AROUND THIS EVENING, AND THAT SHOULD
GRADUALLY TAPER OFF THRU THE OVERNIGHT. WIND WILL BE IN THE USUAL
CAD CONFIGURATION, BUT BECOME LIGHTER. THE WEDGE WEAKENS ON MONDAY,
BUT THE LOW CLOUDS WILL TAKE A WHILE TO IMPROVE, WITH COMPLETE
SCATTERING OF CIGS IN DOUBT. STILL EXPECT MOST SITES TO REACH VFR BY
LATE AFTN, WITH KAND BEING THE POSSIBLE EXCEPTION. THE CENTER OF
HIGH PRESSURE SETTLES OVER THE AREA LATE IN THE DAY, CAUSING WIND TO
BE MORE VARIABLE OR GO CALM.
OUTLOOK: SOME RETURN OF LOW CLOUDS AND PATCHY FOG EXPECTED AGAIN
MONDAY NIGHT THRU EARLY TUESDAY, BUT CAD SHOULD COMPLETELY ERODE BY
TUESDAY AFTN, BRINGING A BRIEF PERIOD OF VFR TO THE AREA. MOISTURE
QUICKLY SPREADS BACK IN ON WEDNESDAY, AS THE REMNANTS OF ZETA PASS
BY, WITH ANOTHER ROUND OF WIDESPREAD PRECIP AND RESTRICTIONS LIKELY
THRU AT LEAST THURSDAY. DRY AIR BEGINS TO FILTER IN BEHIND ZETA ON
FRIDAY.
CONFIDENCE TABLE...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT MED 69% MED 61% HIGH 91% HIGH 81%
KGSP MED 64% MED 66% HIGH 85% HIGH 86%
KAVL HIGH 91% HIGH 97% LOW 59% HIGH 84%
KHKY MED 66% MED 77% HIGH 85% HIGH 89%
KGMU MED 69% MED 62% HIGH 84% HIGH 85%
KAND MED 78% HIGH 88% HIGH 90% HIGH 82%
THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES ARE AVAILABLE AT
THE FOLLOWING LINK:
WWW.WEATHER.GOV/GSP/AVIATION
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...DEO
NEAR TERM...ARK/JPT
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...ARK
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