312
FXUS62 KGSP 200244
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1044 PM EDT FRI OCT 19 2018
SYNOPSIS
A NARROW BAND OF SHOWERS CROSSES OUR REGION AHEAD OF A COLD FRONT ON
SATURDAY. MUCH COOLER AND DRIER AIR ARRIVES BEHIND THE FRONT
SATURDAY NIGHT THROUGH SUNDAY. THE DRY AND COOL AIR WILL LINGER INTO
THE EARLY PART OF THE WEEK BEFORE THE WEATHER BECOMES MORE UNSETTLED
BY LATE WEEK.
NEAR TERM /THROUGH SATURDAY/
AS OF 1040 PM...LATEST SATELLITE IMAGERY MID TO HIGH LEVEL CLOUDS
STREAMING INTO THE FA AHEAD OF A SLOW MOVING COLD FRONT OVER THE
OHIO RIVER VALLEY. LOW CLOUDS WERE ALSO ADVANCING INTO THE REGION
FROM THE SOUTH DUE TO SOUTHERLY MOIST UPGLIDE IN ADVANCE OF THE
FRONT. THE CLOUDS WILL KEEP MIN TEMPS ELEVATED ABOUT 10-15 DEGREES
ABOVE NORMAL. SHOWERS ALONG AND AHEAD OF AN APPROACHING COLD FRONT
WILL ENTER THE NC MOUNTAINS BEFORE DAYBREAK. THE HIGH-RES GUIDANCE
AGREES THAT THIS ACTIVITY WILL STRUGGLE TO SURVIVE OVER THE
MOUNTAINS TO THE PIEDMONT. SO POPS REFLECT CATEGORICAL ALONG THE TN
LINE TO SLIGHT CHC IN THE WESTERN UPSTATE. THERE WILL BE LITTLE, IF
ANY CAPE WITH THE FRONT; NO THUNDER IS EXPECTED AND QPF WILL BE
LIGHT.
THE FRONT SHOULD PASS QUICKLY THRU THE FORECAST AREA ON SATURDAY,
USHERING IN STRONG LOW-LEVEL CAA BY MIDAFTERNOON. SKIES WILL START
TO CLEAR, AND NWLY DOWNSLOPE FLOW WILL NEGATE SOME OF THE CAA
INITIALLY EAST OF THE MOUNTAINS. SO IT WILL BE A TRICKY MAX TEMP
FORECAST. FOR NOW, GOING WITH SUPERBLEND, WHICH KEEPS TEMPS IN THE
50S TO MID 60S IN THE MOUNTAINS, BUT STILL GETTING TO THE UPPER 60S
TO LOWER 70S EAST. WINDS SHOULD START TO PICK UP ACROSS THE HIGH
TERRAIN BY LATE AFTN, BUT WILL SHOULD STAY BELOW WIND ADVISORY
CRITERIA THRU THE DAYLIGHT HOURS.
SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/
AS OF 245 PM EDT FRIDAY: THE FORECAST IS STILL ON TRACK TO BRING THE
COLDEST AIR OF THE SEASON INTO THE WESTERN CAROLINAS AND NORTHEAST
GEORGIA ON SATURDAY NIGHT IN THE WAKE OF A COLD FRONT/SHORT WAVE
PASSAGE. THIS WILL BE AN ADVECTIVE FREEZE AS THE WIND WILL COME
AROUND TO NW AND SHOULD BE HOWLING AT TIMES ACROSS THE RIDGETOPS
AND HIGHER ELEVATIONS, NOT QUITE HIGH ENOUGH TO SUGGEST A WIND
ADVISORY AT THIS TIME, BUT THE GUIDANCE HAS 850 MB WINDS ON THE
ORDER OF 40 KT OR SO. THE TREND IN THE GUIDANCE REMAINS SLIGHTLY
COLDER WITH EACH RUN, SO CONFIDENCE IS HIGH ENOUGH NOW TO ISSUE A
FREEZE WATCH FOR ALL THE NC MOUNTAINS AND THE HIGHER ELEVATIONS OF
THE NRN FOOTHILLS OF NC. IN THAT AREA, ONLY THE LITTLE TN RIVER AND
FRENCH BROAD RIVER VALLEYS LOOK LIKE THEY WILL STAY IN THE MID-30S,
BUT WITH THE TREND, THEY COULD EASILY ALSO GET BELOW 32F. FROST
WOULD BE PREVENTED BY THE STEADY NW WIND ACROSS THE MTNS, AND
ELSEWHERE. RESIDUAL LOW LEVEL MOISTURE WILL BE FORCED UPSLOPE
BY THE STRONG NW FLOW, BUT MOISTURE LOOKS TO BE SHALLOW, SO THE
CHANCES OF MEANINGFUL PRECIP LOOK LOW. ALL THE SAME, A FEW PLACES
NEAR THE TN BORDER WILL PROBABLY HAVE THEIR FIRST SNOWFLAKES OF
THE SEASON. THE MOISTURE PULLS OUT BY DAYBREAK ON SUNDAY, WHICH
INCIDENTALLY LOOKS LIKE A CRISP AND COOL AUTUMN DAY WITH BRIGHT
SUN AND TEMPS TEN DEGREES BELOW NORMAL. WE ARE SET TO DO THE
FROST/FREEZE THING ALL OVER AGAIN SUNDAY NIGHT AS THE MODELS SHOW
THE CENTER OF THE SFC HIGH MOVING OVER WRN NC AT DAYBREAK MONDAY
WITH WHAT SHOULD BE IDEAL RADIATIONAL COOLING CONDITIONS. DO NOT
BE SURPRISED IF OUR FORECAST IS 3-5 DEGREES TOO WARM FOR EARLY
MONDAY MORNING. HAVE A FEELING THAT A GOOD BIT OF THE NC FOOTHILLS
AND WRN PIEDMONT WILL ALSO FLIRT WITH 32F AROUND DAYBREAK MONDAY,
WITH LOTS OF FROST EAST OF THE MOUNTAINS. MONDAY WILL BE ANOTHER
BEAUTIFUL AUTUMN DAY WITH SUN AND COOL TEMPS.
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
AS OF 215 PM EDT FRIDAY: THE WEATHER FOR BETTER PART OF THE WEEK
STILL LOOKS RELATIVELY TRANQUIL WITH HIGH PRESSURE DOMINANT. A SHORT
WAVE SHOULD BRING A DRY COLD FRONT ACROSS THE REGION ON TUESDAY
TO REINFORCE THE HIGH AND KNOCK TEMPS BACK DOWN BELOW NORMAL. THE
RELATIVELY FLAT UPPER FLOW MAY BECOME BRIEFLY MORE NW DURING THE
MIDDLE PART OF THE WEEK AS A RIDGE MOVES EASTWARD ACROSS THE PLAINS
AND MIDWEST. FROM THURSDAY ONWARD, SIGNIFICANT MODEL DIFFERENCES
RAISE UNCERTAINTY. THE GFS WOULD MOVE A WEAK UPPER SYSTEM ACROSS
THE AREA AND KEEP PRECIP SUPPRESSED TO THE SOUTH THRU THE END OF
THE PERIOD. THE ECMWF WOULD STILL ALLOW FOR A STRONGER SHORT WAVE
TO MOVE ACROSS THE SRN TIER, AND ALTHO THE TIMING HAS SLIPPED,
STILL BRINGS PRECIP BACK IN THURS NITE AS A SFC WAVE MOVES EASTWARD
ACROSS THE DEEP SOUTH. THE FCST GENERALLY FOLLOWS ALONG WITH THE
SPIRIT OF THE ECMWF AS IT HAS BETTER CONTINUITY AT THIS POINT.
AVIATION /03Z SATURDAY THROUGH WEDNESDAY/
AT KCLT AND ELSEWHERE: LOW CLOUDS VFR LOWERING TO MVFR ARE MOVING
INTO THE REGION FROM THE SOUTH AND EXPECTED TO OVERSPREAD MANY
TERMINALS THIS EVENING, ESPECIALLY FROM KGSP/KGMU TO KCLT AND POINTS
SOUTH. SHOWER ACTIVITY WILL LIKELY MOVE INTO THE REGION FROM THE
WEST MAINLY AFTER AFTER MIDNIGHT AHEAD OF AN APPROACHING COLD FRONT.
PATCHY FOG AND LOWERING VSBYS ARE POSSIBLE OVERNIGHT THROUGH
SATURDAY MORNING WITH SHOWER ACTIVITY FOCUSED ACROSS THE MTNS.
SHOWER ACTIVITY WILL QUICKLY DIMINISH FROM WEST TO EAST (EXCEPT FOR
LINGERING UPSLOPE SHOWERS NEAR THE TN BORDER) SATURDAY AFTERNOON
WITH A WIND SHIFT TO THE WEST OR NORTHWEST WITH GUSTS UP TO 20 MPH
POSSIBLE.
OUTLOOK: GUSTY NW WINDS EXPECTED SATURDAY NIGHT BEHIND A STRONG COLD
FRONT. HIGH PRESSURE QUICKLY BUILDS IN SUNDAY, ALLOWING WINDS TO
SUBSIDE AND BRINGING CLEAR CONDITIONS.
CONFIDENCE TABLE...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT MED 79% MED 65% MED 73% HIGH 100%
KGSP MED 73% MED 71% HIGH 100% HIGH 100%
KAVL HIGH 100% HIGH 86% HIGH 82% HIGH 100%
KHKY HIGH 100% HIGH 93% HIGH 98% HIGH 100%
KGMU MED 65% MED 64% HIGH 100% HIGH 100%
KAND MED 75% MED 61% HIGH 87% HIGH 100%
THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:
WWW.WEATHER.GOV/GSP/AVIATION
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY MORNING
FOR NCZ033-048>053-058-059-062>065-501-503-505.
SC...NONE.
SYNOPSIS...DEO
NEAR TERM...ARK/MUNROE
SHORT TERM...PM
LONG TERM...PM
AVIATION...MUNROE
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