Special Weather Statement, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
250 PM EST WED JAN 11 2012

.SYNOPSIS...
A STRONG LOW PRESSURE SYSTEM ASSOCIATED WITH A COLD FRONT OVER THE
CAROLINAS WILL MOVE OFF TO THE NORTHEAST TONIGHT WITH ANOTHER COLD
FRONT AFFECTING THE REGION ON THURSDAY. HIGH PRESSURE WILL BUILD
INTO THE REGION FOR DRY CONDITIONS AND MODERATING TEMPERATURES
FRIDAY INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 230 PM...A SFC LOW DEVELOPING ALONG THE OCCLUSION NEAR
CHA...WITH A TRAILING COLD FRONT THROUGH THE DEEP SOUTH...WILL ALLOW
WARM SECTOR CONVECTION TO TRANSLATE EWD ACROSS THE SRN HALF OF THE
FORECAST AREA THROUGH LATE AFTERNOON. ONE LIMITING FACTOR FOR STRONG
TO SEVERE TSTMS WITH THIS ACTIVITY IS THAT SFC TO 850 MB FLOW IS
STARTING TO VEER SW...REDUCING LOW LEVEL BULK SHEAR VALUES.
HOWEVER...STILL ANTICIPATE SOME SLIGHTLY ORGANIZED SHALLOW
CONVECTION SE OF INTERSTATE 85 LATE THIS AFTERNOON AS A POCKET OF
800+ J/KG CAPE ON LATEST LAPS MOVES IN. ANOTHER CONVECTIVE CONCERN
WILL BE THE HAIL POTENTIAL OVER THE WRN MTNS WITH THE PASSAGE OF THE
UPPER COLD POOL. WET BULB ZERO HEIGHTS BELOW 7 KFT BY LATE AFTERNOON
OVER THE MTNS WILL MAKE HAIL POSSIBLE IN JUST ABOUT ANY TSTM THAT
FORMS THERE.

REGARDING THE HYDRO THREAT...SOME SPOTTY 2 TO 3 INCH RAINFALL TOTALS
HAVE BEEN REPORTED FROM LAKE TOXAWAY TO HIGHLANDS...BUT WITH NO
ASSOCIATED STREAM FLOODING YET. THE BEST QPF FOR THE REST OF THE
AFTN/EVENING MAY BE UP THE BLUE RIDGE WHERE TOTALS ARE MORE IN THE 1
TO 2 INCH RANGE SO FAR. WILL KEEP THE FFA GOING CONSIDERING THE
FINAL ROUND OF SCATTERED CONVECTION WITH THE THERMAL TROUGH. ANY
FLOODING THAT DEVELOPS WILL PROBABLY NOT BE WIDESPREAD...BUT
ISOLATED STREAM FLOODING COULD STILL DEVELOP UNDER ANY TRAINING
CONVECTION. WILL CONTINUE THE FLOOD WATCH INTO THE EVENING HOURS.

OTHERWISE...THE PHASING UPPER LOW WILL LIFT UP THE APPALACHIANS THIS
EVENING AS THE NEXT UPSTREAM WAVE DIGS INTO THE PLAINS. PROFILES
WILL BEGIN TO DRY OUT AT MID AND UPPER LEVELS TONIGHT...HOWEVER LOW
LEVEL MOISTURE WILL KEEP UPSLOPE SCATTERED SHOWERS GOING IN THE NC
MTNS THROUGH THE EARLY MORNING HOURS. MINS WILL BE A SOLID 10 TO 15
DEGREES ABOVE NORMAL WITH CLOUDS AND MIXING.

MOISTURE AHEAD OF THE NEXT APPROACHING SHARP COLD FRONT AND DEEP
TROUGH WILL LIKELY NOT BE VERY ABUNDANT BY THU AFTN GIVEN THE FAST
EWD PROGRESSION OF THE SYSTEM. MOST OF THE PRECIP WILL BE CONFINED
TO THE IMMEDIATE FRONT AND POST FRONTAL AREAS...ESPECIALLY THE NC
MTNS. SNOW MAY MIX IN AT THE HIGHEST MTN PEAKS LATE IN THE DAY. THE
FROPA WILL BE LATE ENOUGH TO PERMIT HIGHS IN THE LOWER 60S E OF THE
MTNS AND 40S TO 50S MTNS.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AT 230 PM EST WEDNESDAY...AN UPPER LEVEL LOW WILL BE LOCATED IN THE
OH RIVER VALLEY ON THURSDAY NIGHT. THIS LOW MOVES OVER THE EASTERN
GREAT ON FRIDAY. A CHANNELED VORT LOBE MOVING AROUND THIS LOW WILL
CROSS OUR AREA THURSDAY NIGHT AND FRIDAY. AN UPPER TROUGH AXIS
REMAINS OVER THE EAST INTO SATURDAY...BUT OUR AREA REMAINS BETWEEN
NORTHERN AND SOUTHERN STREAM SHORTWAVES. UPSLOPE FLOW SNOW SHOWERS
WILL BE ONGOING THURSDAY NIGHT IN THE NC MOUNTAINS BORDERING
TN...BUT WILL BE LIMITED AS LOW LEVEL FLOW REMAINS WESTERLY. THESE
SNOW SHOWERS TAPER OFF BY FRIDAY NIGHT AS MOISTURE DIMINISHES. AT
THIS TIME ACCUMULATIONS APPROACH TWO INCHES ON SOME OF THE HIGHER
PEAKS ON THE TN BORDER. NO ADVISORY WILL BE ISSUED AT THIS
TIME...GIVING THE NEXT SHIFT A CHANCE TO EVALUATE SNOW POTENTIAL
FURTHER. DRY HIGH PRESSURE BUILDS IN FROM THE GULF STATES ON
SATURDAY.

TEMPERATURES WILL FALL TO AROUND EIGHT DEGREES BELOW NORMAL IN COLD
ADVECTION BY FRIDAY...RECOVERING TO ONLY AROUND FIVE DEGREES BELOW
NORMAL BY SATURDAY.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AT 230 PM EST WEDNESDAY...AN UPPER TROUGH WILL BE LOCATED ALONG THE
EAST COAST ON SUNDAY. THIS FEATURE WILL PROGRESS INTO THE WESTERN
ATLANTIC ON MONDAY...WHILE AN UPPER RIDGE CROSSES THE APPALACHIANS.
BY THE MIDDLE OF NEXT WEEK...A BROAD UPPER TROUGH SETS UP ACROSS THE
NATION.

A BRIEF SHOT OF LOW LEVEL MOISTURE CROSS THE NC MOUNTAINS IN COLD NW
FLOW SATURDAY NIGHT...SUPPORTING LOW CHANCE SNOW SHOWERS ALONG THE
TN BORDER. A BACK DOOR COLD FRONT PASSES BY TO OUR EAST ON SUNDAY...
WHILE HIGH PRESSURE BUILDS EAST ACROSS THE APPALACHIANS. THIS HIGH
PRESSURE CROSSES THE EASTERN SEABOARD ON MONDAY...THEN MOVES
OFFSHORE ON TUESDAY. RETURN FLOW MOISTURE FORM THE GULF OF MEXICO
WILL REACH THE SOUTHERN APPALACHIANS ON THE BACK SIDE OF THE
DEPARTING HIGH ON TUESDAY...AHEAD OF AN APPROACHING COLD FRONT.
FRONTAL PASSAGE OCCURS LATE TUESDAY NIGHT...AN ON WEDNESDAY THE
FRONT WILL BE LOCATED JUST TO OUR SOUTH....WITH A SURFACE WAVE IN
THE GULF STATES.

AFTER A SLIGHT CHANCE OF NW FLOW SNOW SHOWERS ALONG THE TN BORDER
SATURDAY NIGHT AND EARLY SUNDAY...POPS WIL BE CARRIED FROM MONDAY
NIGHT INTO WEDNESDAY...WITH A PEAK AT FRONTAL PASSAGE LATE TUESDAY
NIGHT. MODELS SOUNDINGS HAVE ENOUGH OF A WARM NOSE ABOVE COOL LOW
LEVELS TO SUPPORT STARTING PRECIPITATION AS A SLIGHT CHANCE OF SNOW
OR FREEZING RAIN IN THE NC MOUNTAINS TUESDAY MORNING...AND SLEET
EAST OF THE MOUNTAINS. WITH POPS SO LOW...ACCUMULATIONS WILL NOT BE
CARRIED AT THIS TIME. A CHANCE OF RAIN FOLLOWS DURING THE DAY ON
TUESDAY. BRIEF SNOW IS POSSIBLE BEHIND THE FRONT IN THE NC MOUNTAINS
LATE TUESDAY NIGHT AND EARLY WEDNESDAY. AGAIN...WITH GENERALLY LOW
POPS...ONLY A LIGHT ACCUMULATION WILL BE FORECAST IN THE NORTHERN NC
MOUNTAINS AT THIS TIME. TEMPERATURES WILL RISE FROM SLIGHTLY BELOW
NORMAL TO SLIGHTLY ABOVE NORMAL AHEAD OF THE FRONT...THEN WILL FALL
TO SLIGHTLY BELOW NORMAL BEHIND THE FRONT ON WEDNESDAY IN CLOUD
COVER AND NORTHEAST FLOW.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
AT KCLT...WIDESPREAD SHOWER COVERAGE SHOULD KEEP CIGS IFR ON AVERAGE
THROUGH THE LATE AFTERNOON HOURS. WILL KEEP A CB MENTION IN UNTIL
01Z...BUT SEE NO UPSTREAM LIGHTNING TO SUGGEST WE NEED A TEMPO TSRA
AT THIS POINT. SE WINDS WILL TURN SRLY WITH TIME AND THEN SW THROUGH
THU MORNING. EXPECT LIFR TO IFR CIGS OVERNIGHT...WITH SLOW LIFTING
TO MVFR BY 15Z THU WITH SW MIXING.

ELSEWHERE...SHOWER COVERAGE IS BEGINNING TO SLOWLY SCATTER OUT FROM
THE SW EARLY THIS AFTERNOON...BUT STRONGER CONVECTION IS STARTING TO
FILL BACK IN AS THE UPPER COLD POOL APPROACHES. TEMPO TSRA COULD BE
NEEDED KAVL TO KGSP TO KAND BEFORE 21Z...BUT WILL HOLD ON CB CLOUD
TYPES THERE FOR NOW. MOST LOCATIONS WILL MAINTAIN IFR CIGS...BUT
TEMPO LIFR TO MVFR CIGS WILL POSSIBLE AT TIMES BETWEEN MIXING WITH
APPROACHING FRONT AND THEN HEAVIER SHOWERS. SE WINDS WILL TURN SRLY
THEN SW THROUGH THE PERIOD. DESPITE THE DECENT MIXING...A MOIST BL
WILL KEEP LIFR TO IFR CIGS IN PLACE OVERNIGHT. CIGS WILL STEADILY
LIFT TO MVFR THROUGH 15Z THU.

OUTLOOK...A SECOND COLD FRONT WILL CROSS THE REGION LATE
THURSDAY...WITH DRIER HIGH PRES AND VFR CONDITIONS RETURNING FOR THE
WEEKEND.

AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE
PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE
CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)...

WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...FLOOD WATCH UNTIL MIDNIGHT EST TONIGHT FOR GAZ010.
NC...FLOOD WATCH UNTIL MIDNIGHT EST TONIGHT FOR NCZ033-035-049-050-
     053-059-062>065-501>510.
SC...FLOOD WATCH UNTIL MIDNIGHT EST TONIGHT FOR SCZ001>003.

&&

SYNOPSIS...JOH
NEAR TERM...HG
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...HG

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