397
FXUS62 KGSP 181153
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
653 AM EST SAT JAN 18 2025
SYNOPSIS
LOW PRESSURE MOVING ACROSS THE REGION WILL PROVIDE WIDESPREAD RAIN
THIS MORNING, WITH A WINTRY MIX ACROSS PORTIONS OF THE MOUNTAINS. A
ROUND OF LIGHT SNOW SHOWERS COULD DEVELOP LATE TONIGHT OR SUNDAY
NEAR THE TENNESSEE BORDER. ARCTIC HIGH PRESSURE RETURNS MONDAY
BRINGING BITTER COLD TO THE REGION FOR NEXT WEEK. A STORM SYSTEM
IS EXPECTED TO TRACK FROM THE NORTHERN GULF OF MEXICO TO OFF THE
SOUTHEAST COAST MIDWEEK.
NEAR TERM /THROUGH TONIGHT/
AS OF 645 AM: A KEY FEATURE OF INTEREST FOR THE SHORT TERM WILL BE
THE SHORTWAVE TROUGH NOW OVER FAR WESTERN TN, PROGGED TO DAMPEN AS
IT TRACKS UP THE OHIO VALLEY TODAY. AN ASSOCIATED WARM FRONT EXTENDS
ACROSS NORTHERN AL/GA/SC PRESENTLY. LIGHT PRECIP IS OCCURRING
OVER THE APPALACHIAN REGION AS A RESULT OF DYNAMIC LIFT FROM
THE SHORTWAVE AS WELL AS WARM UPGLIDE, WITH THIS ROUND SHIFTING
EASTWARD ACROSS THE AREA FOR THE REMAINDER OF THE MORNING. MOST
WET-BULB TEMPS IN THE MOUNTAINS HAVE WARMED ABOVE FREEZING AS A
RESULT OF WAA ALOFT AND/OR MOISTENING WITH THE ONSET OF PRECIP,
BUT A FEW POCKETS OF COLDER TEMPS EXIST IN THE SW MOUNTAINS, AND
LARGER SWATHS OF THE MOUNTAINS NE OF THE FRENCH BROAD VALLEY. TEMP
PROFILES WOULD APPEAR TO BE ENTIRELY BELOW FREEZING ABOVE ABOUT
800 MB, WITH A NEAR-ISOTHERMAL LAYER BELOW. WHERE TEMPS ARE NEAR
FREEZING SOME WET SNOW OR SLEET COULD BE FALLING, BUT NO DEFINITIVE
REPORTS SO FAR. WE ISSUED AN SPS EARLIER FOR THE POSSIBILITY OF
QUICK ACCUMULATION OF PERHAPS 1 INCH OF SNOW IN ANY COLDER SPOTS,
BUT BASED ON THE TEMP/WET-BULB TRENDS IT CURRENTLY LOOKS UNLIKELY
WE'LL NEED TO REISSUE THAT WHEN IT EXPIRES AT 8 AM.
PRECIP CHANCES WILL INCREASE OVER THE MOUNTAINS THRU 7-9 AM BEFORE
TAPERING OFF AS THE MAIN AREA OF FORCING PASSES TO THE PIEDMONT,
AND AS WINDS VEER ALOFT AND MOISTURE BECOMES MORE SHALLOW. ANY
REMAINING PRECIP AFTER ABOUT 10 AM IS EXPECTED TO BE PREDOMINANTLY
IF NOT ENTIRELY RAIN. MOST INDICATIONS ARE THAT THIS INITIAL ROUND
OF PRECIP WILL TAPER OFF IN THE I-85/I-77 CORRIDORS BY NOON. WAA
WILL CONTINUE IN THE LOW LEVELS AND LIKELY WILL MAINTAIN CLOUD
COVER OVER MUCH OF THE AREA THIS AFTERNOON. DESPITE THAT, TEMPS
WILL RISE TO NEAR NORMAL ACROSS THE CWA TODAY. HEIGHTS WILL RISE
BRIEFLY AS THE SHORTWAVE DEPARTS AND/OR DAMPENS OUT, BUT LONGWAVE
TROUGH ASSOCIATED WITH APPROACHING ARCTIC AIRMASS WILL REMAIN TO
OUR WEST. JET STREAK AMPLIFIES TO OUR SOUTH AND WEAK SFC LOW TRACKS
ACROSS THE UPPER COASTAL PLAIN OF GA/SC. LIGHT SHOWERS RESULT IN
MOST MODEL SOLUTIONS ACROSS OUR PIEDMONT. SUBTLE DIFFERENCES IN
THE TRACK OF THIS FEATURE TRANSLATE TO A LOW CONFIDENCE FORECAST,
SO WE ADVERTISE NO BETTER THAN 30-40% POP THERE. TEMPS WILL BE
WARM ENOUGH FOR ONLY RAIN WITH THIS FEATURE--MINS LIKELY SEVERAL
DEGREES ABOVE NORMAL UNDER PERSISTENT CLOUD COVER. PROG SOUNDINGS
INDICATE A LOW INVERSION WITH SATURATION BELOW, SO FOG LIKELY
(AND PERHAPS DENSE AT LEAST LOCALLY). SOME WEAK UPSLOPE PRECIP
MAY ALSO CONTINUE ALONG THE TN BORDER TONIGHT WHICH ALSO LIKELY
WOULD BE RAIN, MOST OF THE NIGHT. HOWEVER, BY DAYBREAK SUNDAY,
TROUGH AXIS AND COLD FRONT WILL REACH THE MOUNTAINS AND PRECIP
LIKELY WILL CHANGE TO SNOW, WITH ACCUMS MAINLY SUNDAY.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/
AS OF 3:35 AM EST SATURDAY...THE SHORT-TERM FCST PICKS UP AT 12Z ON
SUNDAY WITH VERY BROAD UPPER TROFING CENTERED OVER THE CENTRAL CONUS.
THIS TROF WILL BE EXPANSIVE AND COVER MOST OF THE CONUS THRU THE BULK
OF THE PERIOD. THE TROF DOES BEGIN TO SHIFT EAST AND DEAMPLIFY TOWARDS
THE END OF THE PERIOD EARLY TUESDAY AS UPPER RIDGING BUILDS OVER THE
WEST COAST. AT THE SFC, ANOTHER LOW WILL SPIN UP OVER THE CAROLINAS
ALONG A LINGERING FRONTAL BOUNDARY AS THE PERIOD IS BEGINNING. THIS
LOW IS EXPECTED TO QUICKLY LIFT NORTHEAST AND OFF THE ATLANTIC COAST
BY SUNDAY NIGHT WITH BROAD, ARCTIC HIGH PRESSURE SPREADING OVER THE
SOUTHEAST IN ITS WAKE AND LINGERING OVER OUR AREA FOR THE REST OF THE
PERIOD. WINDS ARE EXPECTED TO STRENGTHEN OUT OF THE W AND NW EARLY IN
THE PERIOD AS THE SFC LOW LIFTS NE OF OUR AREA. THE GUSTY WINDS WILL
COMBINE WITH SOME LINGERING RAIN SHOWERS OUTSIDE THE MTNS AND RAIN/SNOW
SHOWERS OVER THE MTNS DURING THE FIRST 6 HRS OR SO OF THE PERIOD ON
SUNDAY. AFTER ROUGHLY 18Z SUNDAY, IT'S LOOKING LIKE TEMPERATURES OVER
THE FAVORED NW FLOW SNOW AREAS WILL BE COLD ENOUGH TO SUPPORT ONLY SNOW.
SNOW AMOUNTS CONTINUE TO TREND UPWARDS MODESTLY, AND NOW IT'S LOOKING
LIKE THE NC/TN BORDER REGION WILL REACH AT LEAST ADVISORY CRITERIA BY
EARLY MONDAY. AFTER DISCUSSION WITH OUR NEIGHBORING FCST OFFICES, WE
ELECTED TO ISSUE A WINTER STORM WATCH FOR HAYWOOD, MADISON, YANCEY,
AND MITCHELL COUNTIES, AND FOR THE HIGH ELEVATIONS OF SWAIN AND GRAHAM
COUNTIES FROM 12Z SUNDAY TO 12Z MONDAY. FOR AVERY, WE ELECTED TO ISSUE
A WINTER WX ADVISORY FOR THE SAME TIME FRAME. OTHERWISE, ANY LINGERING
PRECIP OUTSIDE THE MTNS ON SUNDAY SHOULD BE RAIN. THE COMBINATION OF
GUSTY WINDS AND COLD TEMPS, WILL LIKELY PRODUCE WIND CHILL VALUES BELOW
ZERO ACROSS MOST OF THE MTNS EARLY MONDAY, WITH SINGLE DIGIT TO LOW TEENS
POSSIBLE FOR MOST OF OUR LOWER TERRAIN. AS SUCH, IT IS LIKELY THAT A COLD
WX ADVISORY WILL BE NEEDED FOR A GOOD PORTION OF OUR CWA AND POSSIBLY AN
EXTREME COLD WARNING FOR SOME OF OUR MTN ZONES.
LONG TERM /TUESDAY THROUGH FRIDAY/
AS OF 2:55 AM EST SATURDAY...THE EXTENDED FCST PICKS UP AT 12Z
ON TUESDAY WITH EXPANSIVE UPPER TROFING CENTERED OVER THE GREAT
LAKES TAKING ON A MORE POSITIVE TILT. OVER THE NEXT COUPLE OF DAYS,
THE UPPER TROF WILL LIFT NE AND MOVE OFF THE ATLANTIC COAST WITH
HEIGHTS BRIEFLY RECOVERING OVER THE SOUTHEAST IN ITS WAKE. MOST OF
THE LONG-RANGE GUIDANCE STILL SUGGESTS THAT ANOTHER UPPER TROF WILL
AMPLIFY ACROSS THE CENTRAL CONUS LATE NEXT WEEK AS THE PERIOD IS
ENDING. AT THE SFC, A WEAK LOW WILL BE SPINNING UP OVER THE GULF OF
MEXICO AS THE PERIOD BEGINS EARLY TUESDAY. THIS LOW IS EXPECTED TO
RAPIDLY MOVE NE AND OUT OVER THE ATLANTIC BY EARLY WEDNESDAY. AT
THE SAME TIME, HIGH PRESSURE GETS REINFORCED FROM THE WEST ACROSS
OUR AREA AND LINGERS THRU AT LEAST THURSDAY. BY THE END OF THE
PERIOD LATE NEXT WEEK, MOST OF THE LONG-RANGE GUIDANCE TRIES TO
DEVELOP ANOTHER LOW SOMEWHERE TO OUR SOUTH, BUT THE LOCATION AND/
OR TIMING REMAINS UNCLEAR AT THIS POINT. OVERALL, THE LONG-RANGE
GUIDANCE APPEARS TO BE COMING INTO BETTER AGREEMENT WRT THE LOW
ON TUES/WED. WITH THE COLD AIR IN PLACE DURING THAT TIME, IT'S
STILL LIKELY THAT ANY PRECIP THAT DOES MATERIALIZE WOULD BE SNOW
FOR OUR CWA, HOWEVER POPS REMAIN CAPPED IN THE CHANCE RANGE AT
THIS TIME. THE OTHER MAIN CONCERN FOR THE PERIOD WILL BE THE VERY
COLD AIRMASS THAT LINGERS FOR MOST OF THE PERIOD. THIS AIRMASS
WILL PRODUCE VERY COLD TEMPERATURES AND WIND CHILLS, ESPECIALLY
ACROSS THE MTNS. HIGH TEMPERATURES WILL STRUGGLE TO GET ABOVE
FREEZING BOTH TUESDAY AND WEDNESDAY ACROSS MOST OF OUR CWA. TEMPS
ARE STILL EXPECTED TO REBOUND SOMEWHAT ON THURSDAY AND FRIDAY, BUT
STILL REMAIN WELL-BELOW CLIMATOLOGY. LOW TEMPS EARLY TUES, WED, AND
THURS ARE EXPECTED TO DROP INTO THE SINGLE DIGITS IN THE MTNS AND
TEENS OUTSIDE THE MTNS. WIND CHILL VALUES WILL BE DANGEROUSLY COLD,
ESPECIALLY ACROSS THE MTNS, WITH SINGLE DIGIT TO BELOW ZERO WIND
CHILLS EXPECTED BOTH TUES AND WED MORNING. WIND CHILLS OUTSIDE THE
MTNS ARE EXPECTED TO RANGE FROM THE SINGLE DIGITS TO THE TEENS EACH
MORNING. THUS, A COLD WEATHER ADVISORY LOOKS LIKELY FOR AT LEAST A
PORTION OF OUR AREA DURING THIS PERIOD.
AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
AT KCLT AND ELSEWHERE: PRECIP SHIELD INITIALLY DRIVEN BY SHORTWAVE
WILL SHIFT OVER THE TAF TERMINALS FROM WEST TO EAST THIS MORNING,
LIKELY TAPERING OFF 15-16Z. PERIODS OF MVFR VSBY COULD OCCUR FROM
THIS PRECIP. A LITTLE BIT OF -SN OR -PL COULD MIX IN AT KAVL OR
KHKY BUT PROBABLY NOT ENOUGH FOR IMPACT. CIGS WILL DROP TO MVFR
AND SUBSEQUENTLY IFR AFTER PRECIP TAPERS OFF, DUE TO ONGOING WAA
CAUSING PERSISTENT MOIST INVERSION TODAY. THESE LOWER TO LIFR BY
EVENING AND ARE NOT LIKELY TO ERODE UNTIL SUNDAY, AFTER THE END OF
THE RESPECTIVE PERIODS. A SECOND ROUND OF LIGHT/BRIEF SHRA COULD
OCCUR THIS EVENING OR EARLY SUNDAY, BUT CONFIDENCE IS LOW ENOUGH
ONLY TO MENTION AS VCSH, EXCEPT AT KCLT DUE TO LONGER DURATION
OF CHANCE, IN PROXIMITY TO POSSIBLE ATLANTIC COAST CYCLOGENESIS
TONIGHT. A SIGNAL FOR IFR FOG IS SEEN FOR TONIGHT, LIKELY AFFECTING
ALL SITES. WINDS GENERALLY LIGHT SOUTHERLY, ALTHOUGH TURNING NW
AT KAVL THIS EVENING IF NOT GOING CALM.
OUTLOOK: NW FLOW SNOW SHOWERS LIKELY SUNDAY NEAR THE NC/TN BORDER,
NW OF KAVL, MAINLY IN THE MORNING. AN ARCTIC AIRMASS WILL SPREAD
INTO THE REGION LATE SUNDAY INTO SUNDAY NIGHT, BRINGING EXCEPTIONAL
COLD TO THE REGION WHICH WILL LAST INTO LATE NEXT WEEK. SMALL
CHANCE OF SNOW TUE EVENING THRU EARLY WED.
CLIMATE
RECORDS FOR 01-20
MAX TEMPERATURE MIN TEMPERATURE
STATION HIGH LOW HIGH LOW
------- ---------- ---------- ---------- ----------
KAVL 69 1906 24 2009 53 1954 -13 1985
1890
KCLT 71 1951 30 1983 53 1890 -2 1985
1929 1893
1927
KGSP 72 1933 30 1983 56 1922 1 1985
RECORDS FOR 01-21
MAX TEMPERATURE MIN TEMPERATURE
STATION HIGH LOW HIGH LOW
------- ---------- ---------- ---------- ----------
KAVL 72 1927 8 1985 59 1927 -16 1985
KCLT 73 1935 24 1985 58 1954 -5 1985
KGSP 73 1927 26 1985 59 1933 -4 1985
RECORDS FOR 01-22
MAX TEMPERATURE MIN TEMPERATURE
STATION HIGH LOW HIGH LOW
------- ---------- ---------- ---------- ----------
KAVL 73 1932 21 1960 59 1933 0 1970
KCLT 74 1937 29 1970 60 1906 5 1970
KGSP 72 1938 31 1970 58 1933 3 1893
1921
RECORDS FOR 01-23
MAX TEMPERATURE MIN TEMPERATURE
STATION HIGH LOW HIGH LOW
------- ---------- ---------- ---------- ----------
KAVL 73 1927 20 2005 54 1999 1 1936
1936
KCLT 75 1927 27 1970 59 1999 9 2003
KGSP 73 1974 30 1970 58 1999 5 1893
1927
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...WINTER WEATHER ADVISORY FROM 7 AM SUNDAY TO 7 AM EST MONDAY
FOR NCZ033.
WINTER STORM WATCH FROM SUNDAY MORNING THROUGH MONDAY MORNING
FOR NCZ048>052-058.
SC...NONE.
SYNOPSIS...WIMBERLEY
NEAR TERM...WIMBERLEY
SHORT TERM...JPT
LONG TERM...JPT
AVIATION...WIMBERLEY
CLIMATE...GSP
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