Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 061942
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
242 PM EST SAT FEB 6 2016

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN ACROSS THE FORECAST AREA THROUGH THE
WEEKEND...WHILE STRONG LOW PRESSURE FORMS OFF THE CAROLINA COAST. A
COLD FRONT WILL PUSH THROUGH THE REGION ON MONDAY...USHERING IN
BELOW NORMAL TEMPERATURES AND AN INCREASE OF MOISTURE INTO THE
MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH SUNDAY/...
AS OF 230 PM...VISIBLE SATELLITE IMAGERY SHOWS THAT CLOUD COVER HAS
THINNED A BIT ACROSS THE REGION...WHICH HAS ALLOWED SFC TEMPS TO
WARM UP NICELY...CLOSE TO WHAT WAS EXPECTED. A LOOK AT AREA RADARS
REVEALS SOME LIGHT PRECIP ALREADY DEVELOPING ACROSS PARTS OF E
CENTRAL GA AND THE MIDLANDS OF SC. SOME OF THIS COULD GET FAIRLY
CLOSE TO THE CLT METRO AREA IN THE LATE AFTERNOON...BUT FOR NOW THE
FCST WILL REMAIN DRY.

THE BIG QUESTION FOR THE OVERNIGHT HOURS IS WHAT TO DO ON THE
EASTERN EDGE OF THE FCST AREA AS CYCLOGENESIS TAKES PLACE OFF THE
COAST OF SC. THE SYSTEM IS VERY DYNAMIC WITH A WHOLE HOST OF FORCING
AS AN UPPER LOW CLOSES OFF ACROSS S GA OR N FL EARLY SUNDAY MORNING.
HOWEVER...THAT FORCING WILL MISS THE FCST AREA JUST TO THE EAST. THE
WAY THE MODELS DEPICT THE COMBINATION OF FRONTOGENESIS AND UPPER
FORCING...THERE WILL LIKELY BE A SHARP GRADIENT ON THE W/NW EDGE OF
THE SYSTEM. THE OPERATIONAL GUIDANCE HAS A STRONG CONSENSUS THAT THE
SHARP GRADIENT WILL BE JUST TO THE SE OF UNION COUNTY NC...AND THE
12Z GEFS PLUME DIAGRAM FOR CLT AGREES WITH A LOW POP. WILL INCLUDE A
SMALL CHANCE OF PRECIP EARLY SUNDAY MORNING INTO THE SE HALF OF
UNION COUNTY...TO AGREE WITH NEIGHBORS...BUT THAT IS ABOUT IT.
PARTIAL THICKNESS/FCST SOUNDINGS SUGGEST THAT THE PRECIP WILL FALL
AS EITHER RAIN OR SNOW IF IT HAPPENS AROUND DAYBREAK. EITHER
WAY...THE AMT WILL BE TOO SMALL AND THE CHANCE TOO LOW TO MENTION IN
THE HWO...MUCH LESS ENTERTAIN ANY ADVISORIES. NOTE THIS COULD STILL
BE A PROBLEM...DEPENDING ON WHERE THAT SHARP GRADIENT LIES...SO STAY
TUNED. TEMPS WILL BOTTOM OUT AROUND FREEZING.

ON SUNDAY...THE SURFACE/UPPER LOW PULLS AWAY AND HIGH PRESSURE
STARTS TO MOVE BACK IN FROM THE WEST WITH LOW LEVEL DOWNSLOPE. THIS
SHOULD MAKE FOR A RELATIVELY QUIET DAY...ALTHOUGH PERHAPS A BIT
BREEZY OVER THE WRN PIEDMONT. TEMPS SHOULD MAKE IT BACK TO AROUND
NORMAL.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AS OF 230 PM SATURDAY...A COLD FRONT WILL APPROACH THE SOUTHERN
APPALACHIANS EARLY MONDAY MORNING. BY THE TIME THE FRONT
ARRIVES...LOW TEMPERATURES ACROSS THE CWA ARE FORECAST TO RANGE FROM
THE UPPER 20S ACROSS THE MTNS TO LOW TO MID 30S ACROSS THE UPPER
SAVANNAH RIVER VALLEY. 12Z GFS360 INDICATES THAT A LARGE FIELD OF
BROAD Q-VECTOR CONVERGENCE WILL SWEEP ACROSS THE WESTERN CAROLINAS
AND NE GA ON MONDAY. THE COMBINATION OF THE SFC COLD FRONT AND
PASSING MID LEVEL SYNOPTIC SCALE FORCING WILL SUPPORT PRECIP CHCS
SPREADING ACROSS THE FOOTHILLS AND PIEDMONT DURING MONDAY AFTERNOON.
BETWEEN 18Z MON TO 0Z TUES...H85 WINDS WILL SHIFT FROM THE NW AND
INCREASE TO 25-30 KTS...SUPPORTING UPSLOPE FLOW ALONG THE TN BORDER.
GIVEN THE SFC TEMPERATURES AND LOW LEVEL THERMAL PROFILES...PRECIP
SHOULD FALL AS EITHER SNOW OR A COLD RAIN. SNOW IS EXPECTED ACROSS
THE MTNS IN THE MORNING...THEN SHOULD MIX OVER TO RAIN WITHIN THE
VALLEY FLOOR BY MID DAY. TEMPS ACROSS THE RIDGES SHOULD YIELD HIGH
ELEVATION SNOWFALL THROUGH THE DAYLIGHT HOURS. AREAS EAST OF THE
MTNS SHOULD SEE ONLY RAINFALL AS HIGH TEMPS WARM TO THE 40S ACROSS
THE REGION.

MODERATE TO STRONG H85 CAA WILL SWEEP ACROSS THE FORECAST AREA
MONDAY NIGHT...WITH MTN LOCATIONS COOLING TO -12 TO -14 C BY 12Z
TUES. MIN TEMPS ARE FORECAST TO RANGE FROM THE TEENS ACROSS THE MTNS
TO LOW 20S WITHIN THE VALLEYS...UPPER 20S TO THE EAST. COLD H85
TEMPS WILL REMAIN ACROSS THE MTNS THROUGH THE DAY...SUPPORTED BY
THICK CLOUD COVER AND GUSTY NW WINDS. CATE TO LIKELY POPS WILL
REMAIN ACROSS THE TN BORDER COUNTIES THROUGH THE MORNING...REDUCING
TO CHC POPS DURING THE AFTERNOON. FOOTHILL TO PIEDMONT AREAS WILL
REMAIN GENERALLY DRY. HIGH TEMPS SHOULD REMAIN BELOW FREEZING ACROSS
THE MTNS TO AROUND 40 EAST. MON AND TUES...TOTAL SNOWFALL FORECAST
GIVES 2 TO 4 INCHES ALONG THE SPINE OF THE APPALACHIANS TO 1-2
INCHES ACROSS THE VALLEYS OF THE TN BORDER COUNTIES. LITTLE TO NO
ACCUMS EXPECTED ACROSS THE FOOTHILLS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
AS OF 200 PM SATURDAY...ONE MORE PIECE OF CHANNELED VORTICITY WILL
DIVE THRU THE EASTERN CONUS TROF TUESDAY NIGHT...ENHANCING QG
FORCING ACROSS THE SOUTHERN APPALACHIANS. FROM WEDNESDAY THRU
THURSDAY NIGHT...THE EASTERN TROF WILL LIFT OUT SOMEWHAT...RESULTING
IN MORE ZONAL FLOW ATOP THE CWFA. THEN ANOTHER CLIPPER SHORT WAVE
SYSTEM WILL DIVE INTO THE MIDWEST ON FRIDAY...AND CARVE OUT THE
EASTERN TROF AGAIN BY SATURDAY.

AT THE SFC...A LARGE LOW PRESSURE SYSTEM WILL BE GRADUALLY FILLING
OVER THE NORTHEAST...KEEPING OUR AREA UNDER PERSISTENT LLVL NWLY
FLOW. MOISTURE WILL CONTINUE TO BANK UP ALONG THE USUAL NW FLOW
UPSLOPE AREAS...BUT SHUD GRADUALLY TAPER OFF WEDNESDAY INTO
WEDNESDAY NIGHT. ADDITIONAL SCATTERED TO OCCASIONALLY NUMEROUS SNOW
SHOWERS ARE EXPECTED ALONG THE TN LINE...ESPECIALLY TUESDAY NIGHT
THRU WEDNESDAY AFTERNOON. THE REST OF THE AREA SHUD BE MOSTLY CLEAR
AND QUITE CHILLY. THICKNESSES AND 850 MB TEMPS BOTTOM OUT EARLY
WEDNESDAY...WITH STILL SOME CAA AND WINDS TO MAKE FOR SOME WIND
CHILL CONCERNS IN THE HIGH TERRAIN. ADDITIONAL SNOW ACCUMS SHUD BE
GENERALLY LIGHT...BUT SOME SORT OF WINTER WX OR WIND CHILL ADV WILL
LIKELY BE NEEDED UNTIL THINGS WIND DOWN. A REINFORCING COLD FRONT IS
EXPECTED TO ACCOMPANY THE NEXT SYSTEM...BUT THE MEDIUM RANGE MODELS
ARE IN DISAGREEMENT ON THE EXACT TIMING AND ON THE AMOUNT OF
MOISTURE WITH IT. FOR NOW...I WILL INTRODUCE A SLGT CHC OF SNOW
SHOWERS ALONG THE TN LINE FRIDAY THRU FRIDAY NIGHT. TEMPS WILL BE
ABOUT 15-20 DEGREES BELOW NORMAL ON WEDNESDAY...WITH WIND CHILLS
BELOW ZERO ABOVE ABOUT 3500 FT EARLY THURSDAY MORNING. THEN TEMPS
WILL MODERATE BACK TO ONLY A CATEGORY OR TWO BELOW NORMAL BY
FRIDAY...BEFORE THE NEXT SURGE OF COLD AIR BRINGING TEMPS BACK DOWN
5 TO 10 DEG BELOW NORMAL FOR SATURDAY.

&&

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
AT KCLT...VFR THROUGH THE EVENING HOURS. THE BIG QUESTION COMES
ABOUT LATE TONIGHT AND EARLY SUNDAY MORNING IN TERMS OF FROZEN
PRECIP ON THE WESTERN EDGE OF THE STORM SYSTEM EXPECTED TO DEEPEN
RAPIDLY OFF THE CAROLINA COAST. THERE SHOULD BE A VERY SHARP WRN
EDGE TO THE PRECIP AND LOW CLOUDS...AND FOR THE TIME BEING...IT IS
MOST LIKELY THAT THE EDGE WILL BE EAST OF KCLT.  THUS...THE TAF
FEATURES ONLY A VICINITY SHOWER WITH A SCATTERED LOW CLOUD DECK...
AND NO RESTRICTIONS. THERE IS A SMALL CHANCE THAT THE PRECIP COULD
REACH BACK FAR ENUF TO THE W TO AFFECT THE AIRFIELD AROUND
DAYBREAK...BUT FAR TOO LOW A CHANCE TO MENTION RIGHT NOW. THIS MIGHT
BE CHANGED IN FUTURE AMENDMENTS. WIND SHOULD BE LIGHT NE THIS
AFTERNOON...AND COME AROUND TO NORTHERLY AS THE SFC LOW DEVELOPS
OFFSHORE LATER TONIGHT.

ELSEWHERE...VFR CONDITIONS WILL CONTINUE THROUGH THE PERIOD. HIGH
CLOUDS WILL REMAIN ACROSS THE AREA THRU THE DAY WITH SOME MID CLOUD
MOVING IN THIS AFTERNOON AND CONTINUING OVERNIGHT... ESPECIALLY FOR
THE I-85 TAF SITES. N TO NE WIND CONTINUES THRU THE PERIOD. AT KAVL
THIS SHOULD BE NNW...WITH SOME GUSTS LIKELY AFTER SUNRISE SUNDAY.

OUTLOOK...WEAK HIGH PRESSURE WILL REMAIN ACROSS THE REGION WILL FALL
APART SUNDAY NIGHT. A STRONG UPPER AIR DISTURBANCE COULD BRING
ENOUGH MOISTURE TO WRING OUT A FEW RAIN OR SNOW SHOWERS ON MONDAY.

CONFIDENCE TABLE...

            19-01Z        01-07Z        07-13Z        13-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET 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...NONE.
SC...NONE.

&&

$$
SYNOPSIS...SBK
NEAR TERM...PM
SHORT TERM...NED
LONG TERM...ARK
AVIATION...PM


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