Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 231944
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
244 PM EST FRI JAN 23 2015

.SYNOPSIS...
LOW PRESSURE WILL TRACK ALONG THE CAROLINA COAST TONIGHT...BEFORE
CONTINUING UP THE EAST COAST...ALLOWING PRECIPITATION TO TAPER OFF
IN OUR AREA. HIGH PRESSURE WILL BRIEFLY BUILD IN ON SUNDAY...BEFORE
A LOW PRESSURE SYSTEM AND TRAILING UPPER LEVEL DISTURBANCE AFFECT
THE AREA SUNDAY NIGHT THROUGH TUESDAY MAINLY BRINGING PRECIPITATION
CHANCES TO THE MOUNTAINS. HIGH PRESSURE BUILDS OVER THE AREA FOR THE
MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 225 PM...FORECAST DOES NOT GET ANY EASIER AS UPPER LOW OVER
TEXAS OPENS AND MOVES EAST ALONG THE GULF COAST TONIGHT THEN INTO
THE ATLANTIC SAT. AT THE SFC...MILLER A TYPE LOW PRESSURE SYSTEM
ALONG THE GULF COAST TODAY MOVES TO THE CAROLINA COASTAL PLAIN
TONIGHT THEN UP THE ATLANTIC COAST SATURDAY. THIS WILL KEEP PRECIP
ACROSS THE AREA INTO THE EVENING WITH A DRY SLOT DEVELOPING ACROSS
THE CENTER OF THE CWFA OVERNIGHT BETWEEN THE DEPARTING WARM CONVEYOR
BELT AND THE APPROACHING DEFORMATION ZONE. ALTHOUGH COLD...P-TYPE
SHUD REMAIN ALL RAIN UNTIL PRECIP ENDS SAT MORNING OUTSIDE OF THE
MTNS. THAT SAID...CANNOT RULE OUT SOME SNOW MIXING IN ACROSS THE
LOWER ELEVATIONS OF THE NRN FOOTHILLS/NW PIEDMONT BEFORE ENDING. NO
ACCUMS ARE EXPECTED IF THAT DOES OCCUR. SKIES CLEAR SAT WITH GUSTY
NW WINDS DEVELOPING. LOWS TONIGHT WILL BE 5 TO 10 DEGREES ABOVE
NORMAL...WITH HIGHS SAT A FEW DEGREES BELOW NORMAL.

OF COURSE...A DIFFERENT STORY EXISTS ACROSS THE MTNS. MOST LOCATIONS
ARE ABOVE FREEZING...EXCEPT FOR THE HIGHEST ELEVATIONS OF THE NRN
MTNS. THE GOOD NEWS THERE IS THAT PRECIP IS VERY LIGHT...SO ONLY
LIGHT ADDITIONAL ICE ACCRETION IS EXPECTED THRU THE AFTERNOON.
PRECIP WILL PICK BACK UP ACROSS THE MTNS OVERNIGHT AS A DEFORMATION
ZONE MOVES IN FROM THE WEST AND NWLY FLOW DEVELOPS. THE WARM NOSE
CURRENTLY OVER THE AREA WILL ONLY SLOWLY ERODE OVERNIGHT AS THE
COLDER H85 LEVEL AIR IS SLOW TO MOVE IN AS THIS IS NOT A TYPICAL NW
FLOW EVENT. THEREFORE...WHERE TEMPS FALL BACK BELOW FREEZING...
MAINLY ABOVE 3500 FEET...PRECIP WILL CHANGE OVER TO FREEZING RAIN.
ONCE THE COLD AIR ARRIVES TOWARD DAYBREAK...THEN THE PRECIP WILL
CHANGE OVER TO SNOW...WITH SNOW LEVELS DROPPING TO OR NEAR THE
VALLEY FLOORS. BY THEN...PRECIP WILL BE TAPERING OFF AS THE
DEFORMATION ZONE MOVES NE OF THE AREA AND THE LOW LEVEL MOISTURE
BECOMES MORE SHALLOW. IN FACT...PRECIP WILL END RATHER QUICKLY SAT
MORNING WITH ONLY SOME LINGERING CLOUDS ACROSS THE NRN MTNS FOR THE
AFTERNOON. THEREFORE...GIVEN THE LIGHT ADDITIONAL ACCUMS OF ICE AND
SNOW ACROSS THE NC MTNS...WILL LEAVE THE WINTER WX ADV IN PLACE.
THERE WILL BE SOME LIGHT ACCUMS IN THE VALLEYS OF THE CENTRAL AND
SRN MTNS. HOWEVER...THEY SHUD BE AN INCH OR LESS WITH NO ICING...
PRECLUDING THE NEED FOR AN ADV. DO EXPECT GUSTY WINDS TO DEVELOP
OVERNIGHT AND CONTINUE THRU THE DAY. LOWS TONIGHT WILL BE 5 TO 10
DEGREES ABOVE NORMAL WITH HIGHS SAT 5 TO 10 DEGREES BELOW NORMAL.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AS OF 230 PM FRIDAY...ANOTHER VORTMAX WILL CROSS THE CWFA SATURDAY
EVENING...AS IT ROUNDS THE BASE OF A BROAD 500 MB ERN CONUS TROF.
THE NAM AND GFS AGREE THAT THERE WILL BE A BRIEF SHOT OF SHALLOW
MOISTURE WITHIN REINFORCING 850 MB NWLY FLOW. ENUF SO THAT A FEW
FLURRIES/LGT SNOW SHWRS MAY DEVELOP ALONG THE TN BORDER...PRIMARILY
IN THE NRN NC MTNS. I HAVE POPS RAMPING BACK UP TO CHC IN THE NRN
FOUR TN BORDER ZONES LATE EVENING...THEN TAPERING OFF TO LESS THAN
15 PCT BY 12Z SUN. THE REST OF THE AREA SHUD SEE MOSTLY CLEAR SKIES.
TEMPS WILL BE NEAR NORMAL.

SUNDAY THRU MONDAY...A POTENT CLIPPER SYSTEM WILL DIVE INTO THE OHIO
VALLEY ON SUNDAY...THEN CROSS THE SOUTHERN APPALACHIANS SUNDAY
NIGHT. THE SYSTEM WILL HAVE STRONG DEEP-LAYER Q-VECTOR
CONVERGENCE...COUPLED WITH DECENT RH. A CROSS SECTION OF THE NC MTNS
SHOWS PEAK LLVL LIFT WITH THE QG FORCING WILL BE AROUND 06Z. OF
COURSE...GIVEN THE FAST MOVING NATURE...EXACT TIMING IN THE MODELS
MAY BE OFF BY A FEW HOURS. IN ANY CASE...HAVE POPS RAMP UP TO HIGH-
END LIKELY ALONG THE TN BORDER OVERNIGHT...WITH EVEN A BIT OF SLGT
CHC TO LOW-END CHC OF LIGHT RAIN ACRS THE NC PIEDMONT AND ERN
UPSTATE...AS THE STRONG FORCING MAY ALLOW FOR A FEW STRAY SHWRS TO
/BREAK CONTAINMENT/. FCST SNDGS SHOW STEEP LLVL LAPSE RATES WITH
PROGRESSIVELY BETTER NW UPSLOPE COMPONENT ALONG THE TN LINE (30-35
KTS). THE SFC-BASED WARM LAYER LOOKS TOO DEEP FOR ANY SNOW OR SLEET
EAST OF THE MTNS. HOWEVER...GIVEN THE OVERNIGHT TIMING...CANNOT RULE
OUT A VERY BRIEF AND SPOTTY MIX ACRS MAINLY THE NC FOOTHILLS AND NW
PIEDMONT MONDAY MORNING. FOR NOW...I WILL KEEP ONLY RAIN MENTION
OUTSIDE THE HIGH TERRAIN. SNOW AMTS LOOK SOLIDLY ADVISORY LVL...AND
COULD APPROACH WARNING...IF THE UPSLOPE FLOW CAN OVERLAP THE BEST
LAPSE RATES AND MID LVL FORCING. WILL CONTINUE TO MENTION SNOW
POSSIBLE IN THE NW FLOW AREAS IN THE HWO. TEMPS WILL BE NEAR NORMAL
ON SUNDAY...WITH SLIGHTLY ABOVE NORMAL LOWS MONDAY MORNING...THEN
NEAR OR SLIGHTLY BELOW NORMAL HIGHS MONDAY AFTN...AS CAA AND
LINGERING CLOUDS LIMIT HEATING.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 200 PM FRI...LATEST GLOBAL MODEL RUNS SHOW A SECOND NRN STREAM
SHORTWAVE DIVING OUT OF CANADA EARLY NEXT WEEK...THRU THE UPPER OH
VALLEY AND THEN ACROSS THE CAROLINAS MON NIGHT AND TUE. THE MODELS
HAVE TRENDED A LITTLE STRONGER WITH THIS WAVE...WITH EARLIER RUNS
GENERALLY SUGGESTING ONLY A WEAK POCKET OF VORT CROSSING THE AREA IN
THE WAKE OF MONDAY/S CLIPPER. THE IMPLICATION FOR THE FCST IS MORE OR
LESS TO PROLONG THE EFFECTS OF AN ERN CONUS TROUGH...MAINTAINING
CHANCES OF NW FLOW PRECIP IN THE MTNS AND BRINGING SLIGHT CHANCES TO
SOME AREAS EAST OF THE MTNS AS THE SHORTWAVE PASSES. POPS DIMINISH BY
EARLY WED AS SHORTWAVE RIDGING RETURNS TO THE SRN APPALACHIAN REGION
FOR WED AND WED NIGHT. HOWEVER THIS RESULTS FROM THE BREAKDOWN OF THE
REX BLOCK OVER THE WEST COAST...AND THE REMNANT SHORTWAVE FROM THE
BLOCKING LOW MOVES IN BEHIND THAT RIDGE...WHICH COULD BRING SOME
PRECIP BACK TO THE AREA BY THU NIGHT. GUIDANCE SUGGESTS THIS
SHORTWAVE COULD PHASE WITH A CLIPPER AND DRIVE A COLD FRONT INTO THE
UPPER OH/TN VALLEYS. THAT MIGHT BEAR WATCHING. TEMPS WILL REMAIN A
LITTLE BELOW CLIMO MON NIGHT THRU WED MRNG...WHEN THICKNESSES APPEAR
TO BOTTOM OUT. A GENTLE WARMING TREND IS EXPECTED THEREAFTER.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
AT KCLT...RAIN AND IFR CONDITIONS WILL CONTINUE INTO THE EVENING.
RAIN TAPERS OFF OVERNIGHT...BUT IFR CONDITIONS REMAIN. NELY WIND
BECOMES NLY OVERNIGHT. WINDS TURN NWLY AFTER DAYBREAK AND MOISTURE
BEGINS TO THIN AND LIFT. EXPECT A RISE TO MVFR BY MID MORNING THEN
SCATTERING OUT BY EARLY AFTERNOON. NWLY WINDS BECOME GUSTY BY NOON
AS WELL.

ELSEWHERE...SIMILAR CONDITIONS TO KCLT. KAVL THE BIG EXCEPTION WHERE
SLY WINDS BECOME SELY THIS EVENING THEN NLY OVERNIGHT. THEY WILL
ALSO SEE STRONGER NLY WINDS AND GUSTS AFTER DAYBREAK. IN ADDITION...
IFR CIGS LIKELY TO LINGER LONGER THERE. CANNOT RULE OUT SOME SNOW AT
KAVL OVERNIGHT...BUT ANY ACCUMS WILL BE VERY LIGHT.

OUTLOOK...VFR BUT GUSTY WINDS EXPECTED SATURDAY AFTERNOON. A SERIES
OF CLIPPER SYSTEMS WILL BRING SNOW CHANCES TO THE AREA EARLY IN THE
WEEK...MAINLY TO THE MTNS NORTH AND WEST OF KAVL.

CONFIDENCE TABLE...

            19-01Z        01-07Z        07-13Z        13-18Z
KCLT       MED   68%     MED   65%     MED   74%     HIGH  86%
KGSP       HIGH  80%     MED   61%     MED   66%     MED   75%
KAVL       MED   76%     MED   71%     MED   73%     MED   69%
KHKY       MED   75%     LOW   58%     MED   66%     HIGH  86%
KGMU       HIGH  80%     MED   61%     MED   66%     MED   76%
KAND       MED   76%     MED   68%     MED   72%     HIGH  85%

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: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...WINTER WEATHER ADVISORY UNTIL NOON EST SATURDAY FOR NCZ033-
     048>052-058-059-501-503-505.
SC...NONE.

&&

$$
SYNOPSIS...WIMBERLEY
NEAR TERM...RWH
SHORT TERM...ARK
LONG TERM...WIMBERLEY
AVIATION...RWH


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