Whittier North Carolina Personal Weather Station - Area Forecast Discussion

000
FXUS62 KGSP 230220
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
920 PM EST WED FEB 22 2012

.SYNOPSIS...
WEAK HIGH PRESSURE WILL LINGER OVER THE AREA THROUGH THURSDAY. A
STRONG COLD FRONT IS EXPECTED TO MOVE OVER THE CAROLINAS EARLY
FRIDAY. HIGH PRESSURE WILL THEN RETURN OVER THE WEEKEND AND LINGER
INTO EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH THURSDAY/...
LINE OF CONVECTION MOVG THRU E TN AND N GA WEAKENING WITH COOLING AS
IT MOVES E...INDICATING A REDUCED THREAT FOR SVR STORMS. ADJUSTED
POPS AND TIMING...LOWERED QPF OVERNIGHT AND TWEAKED TEMP/DP/RH FOR
THIS UPDATE.

PREVIOUS DISCUSSION...STRONGER SHORT WAVE MOVES THRU THE BOTTOM OF A
BROAD LONG WAVE TROF AND ACROSS THE AREA THIS EVENING. THIS SHOULD
HELP ADDITIONAL CONVECTION DEVELOP THIS EVENING AND MOVE IT ACROSS
THE CWFA. ACTIVITY SHUD BEGIN OVER THE NC MTNS AND NE GA AND MOVE
EAST ACROSS THE CWFA. DEW POINTS SHUD CONTINUE TO INCREASE AHEAD OF
THE WAVE IN THE STRONG SWLY FLOW. THIS WILL LEAD TO WEAK INSTABILITY
ACROSS THE AREA THIS EVENING AS THE WAVE MOVES THRU. SHEAR STILL
EXPECTED TO BE QUITE STRONG AS A LOW LEVEL JET DEVELOPS. LARGE
HELICITY VALUES WITH STRONG TURNING PROFILE ALSO EXPECTED. STILL
APPEARS TO BE A THREAT OF SEVERE STORMS PRODUCING DAMAGING WINDS OR
EVEN A TORNADO IF THE WEAK INSTABILITY CAN BE REALIZED. MULTICELLS
OR EVEN MINI-SUPERCELLS WILL BE POSSIBLE. THE CONVECTION SHUD SWEEP
EAST OF THE AREA AFTER MIDNIGHT WITH SOME LINGERING MTN SHRA ENDING
BY DAYBREAK. EXPECT AREAS OF FOG AND LOW CLOUDS TO DEVELOP AGAIN
TOWARD MORNING IN THE LINGERING LOW LEVEL MOISTURE. LOWS WILL BE AS
MUCH AS 15 DEGREES ABOVE NORMAL.

CLEARING SKIES AND VERY WARM CONDITIONS EXPECTED THU AS HEIGHTS RISE
IN DEVELOPING ZONAL FLOW. EXPECT THE LOW CLOUDS AND FOG TO DISSIPATE
A LITTLE MORE QUICKLY THU MORNING AS FLOW WILL BE A LITTLE MORE WLY
AND DRIER AIR MOVES IN. SHUD BE ANOTHER BREEZY DAY BUT WIND GUSTS
NOT QUITE AS STRONG. HIGHS WILL BE 15 TO 20 DEGREES ABOVE NORMAL IN
THE WLY FLOW AND RISING THICKNESSES.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 200 PM WEDNESDAY...A WEAKLY FORCED FRONTAL BOUNDARY IS
FORECAST TO MOVE ACROSS THE MOUNTAINS AND INTO THE PIEDMONT BY 12Z
FRI WELL AHEAD OF THE MAIN UPPER TROUGH TO ITS WEST. THE QUESTION IS
WHAT THE COVERAGE OF CONVECTION WILL BE THU NIGHT ALONG AND AHEAD OF
THE FRONTAL BOUNDARY? CURRENT INDICATIONS FROM MODEL GUIDANCE IS THAT
A BROKEN LINE OF CONVECTION WILL REACH THE MOUNTAINS SOMETIME AFTER
MIDNIGHT...BUT TEND TO DECREASE IN COVERAGE AS IT MOVES OFF THE
MOUNTAINS EARLY FRIDAY MORNING DUE TO DEEP SW-W WIND FLOW WITH
LITTLE APPARENT BACKING OF THE WIND FIELD IN THE LOWER LEVELS. WIND
SPEEDS/SHEAR WILL BE IMPRESSIVE THU NIGHT WITH 850MB WINDS 50+ KTS.
HELICITY VALUES WILL ALSO BE QUITE HIGH. HOWEVER...LOOKING AT THE
MODEL SOUNDINGS...A MID LEVEL CAPPING INVERSION IS APPARENT. THE
BOTTOM LINE IS THAT IT LOOKS LIKE IT WILL BE DIFFICULT TO GET DEEP
CONVECTION TO DEVELOP OVER A LARGE AREA THU NIGHT...SO WILL SHOW
LIKELY TYPE COVERAGE ENTERING THE MOUNTAINS...BUT DIMINISHING INTO
THE SCATTERED RANGE AS THE FRONT MOVES OFF THE MOUNTAINS. THE SEVERE
THREAT IS CERTAINLY NON ZER0...BUT IT APPEARS ANY SEVERE CONVECTION
SHOULD BE ISOLATED.

THE FORECAST DOES NOT GET ANY EASIER FOR FRI AS THE FRONTAL BOUNDARY
WILL BE SLOW TO EXIT THE AREA AS IT AWAITS A PUSH FROM THE UPPER
TROUGH APPROACHING FROM  THE WEST. THE 12Z MODEL SUITE CONTINUES TO VARY
CONSIDERABLY IN REGARD TO HOW FAST THE FRONT WILL MOVE AWAY FROM THE
AREA AND ALSO HOW MUCH PRECIP WILL FALL ALONG THE BOUNDARY. THE
NAM/ECM/GEM ARE SLOWER/WETTER THAN THE FASTER/DRIER GFS. THE SREF
AGAIN APPEARS TO BE A GOOD COMPROMISE WHICH WILL KEEP POPS OVER THE
AREA OUTSIDE OF MOUNTAINS WITH THE HIGHEST POPS OVER SOUTHERN AREAS.
THE FRONT SHOULD FINALLY PUSH TO THE EAST OF THE AREA FRI NIGHT. THE
UPPER TROUGH AXIS IS FORECAST TO ROTATE THROUGH LATE FRI NIGHT INTO
SAT. LOOKS LIKE AT LEAST SOME SCATTERED SNOW SHOWERS WILL BE THE
RESULT IN THE TN BORDER COUNTIES...ESPECIALLY IN THE NORTHERN
MOUNTAINS. OTHERWISE..,.SAT LOOKS TO BE GENERALLY SUNNY ELSEWHERE WITH
TEMPS ABOUT CATEGORY BENEATH SEASONAL LEVELS EVEN WITH DOWNSLOPE
FLOW. USED A MOS BLEND FOR TEMPS.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 215 PM WEDNESDAY...THE FIRST PORTION OF THE MEDIUM RANGE LOOKS
RATHER STRAIGHT FORWARD AS ALL GUIDANCE SOURCES AGREE THAT SURFACE
HIGH PRESSURE WILL BE IN CONTROL OF OUR WEATEHR REGIME ALL OF
SUNDAY AND MOST IF NOT ALL OF THE DAY ON MONDAY. HOWEVER...
DISCREPANCIES IN THE MODEL GUIDANCE QUICKLY DEVELOP BY LATE MON AS
MODELS BECOME OUT OF PHASE WITH UPPER FEATURES. ECM/GEM ARE MUCH
QUICKER THAN THE GFS WITH THE NEXT UPPER TROUGH AND SUBSEQUENT GULF
MOISTURE RETURN LATE MONDAY INTO MONDAY NIGHT. HPC USED A ECM
ENSEMBLE MEAN FOR THE TUE/WED TIME PERIOD WHICH SUPPORTS AN INITIAL
FRONTAL PASSAGE EARLY TUE...WITH A WAVE DEVELOPING ON THE FRONT AND
THEN MOVING AWAY FROM THE AREA ON WED. HENCE...THE FORECAST WILL BE
DRY SUN AND MON MOST AREAS....WITH UNSETTLED WEATHER RETURNING MON
NIGHT...FEATURING CHANCES OF RAIN INTO EARLY WED. DRYER AIR/CLEARING IS
SHOWN OVERSPREADING THE AREA BY LATE WED. STAYED CLOSE TO HPC
GUIDANCE FIELDS WHICH HAS MAX TEMPS NEAR OR A LITTLE BELOW
AVERAGE.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...MAIN CONCERN IS LINE OF CONVECTION MOVG IN
FROM THE W THIS EVE BUT IT HAS WEAKENED WITH COOLING. KEPT PERIOD OF
-SHRA AND CB CLOUDS WITH MVFR CIGS FOR LATE EVE. QUIDANCE STILL AT
ODDS BUT IFR CIGS STILL LOOK REASONABLE LATE TONIGHT UNTIL AFTER
DAYBREAK. CIGS SHOULD SCATTER BY 14-15Z AT LATEST.

OUTLOOK...LOW PRESSURE WILL DEVELOP OVER THE DEEP SOUTH THU NIGHT
AND FRI. WIDESPREAD LOW CIGS AND PCPN ARE EXPECTED AS THE LOW
DEVELOPS. DRIER AND COLDER WEATHER WILL FOLLOW 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...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...DEO
NEAR TERM...RB/RWH
SHORT TERM...LG
LONG TERM...LG
AVIATION...RB

NWS GSP Office Area Forecast Discussion