Hail in North Carolina, April 17, 2012

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1047 AM EDT TUE APR 17 2012

.SYNOPSIS...
MOISTURE WILL SPREAD NORTHEAST AS A FRONT DRIFTS INTO THE WESTERN
CAROLINAS AND NORTHEAST GEORGIA. THIS FRONT WILL LINGER IN THE AREA
BRINGING MUCH NEEDED RAIN THROUGH WEDNESDAY. THE FRONT WILL
DEPART...AND WEAK HIGH PRESSURE WILL MOVE ACROSS THE AREA ON
THURSDAY AND FRIDAY. ANOTHER FRONT WILL ARRIVE ON SATURDAY. LOW
PRESSURE DEVELOPING ON THE FRONT WILL PASS NEAR THE AREA ON SUNDAY.
DRYING WILL OCCUR BEHIND THE DEPARTING LOW ON MONDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 AM...THE 12Z SFC ANALYSIS PLACED A SLOW-MOVING COLD FRONT
ROUGHLY ALONG THE I-85 CORRIDOR. THE GFS/RUC/NAM ARE ALREADY IN
DISAGREEMENT ON THE EVOLUTION OF THE FRONT THIS AFTN...WITH NAM A
NRN OUTLIER KEEPING THE FRONT ACRS THE NC MTNS. WITH THAT SAID...I
DO LIKE THE NAM CAPE FIELD WHICH LINES UP BEST WITH LATEST OBS AND
CLOUD COVER ON VIS. SO THE BEST GUESS ON HOW CONVECTION WILL DEVELOP
TODAY IS FOR IT TO START ACRS THE NC MTNS...THEN A SECOND BATCH
INVOF THE FRONT ACRS THE UPPER SAVANNAH VALLEY AND LOWER PIEDMONT.
THE 12Z SOUNDINGS SHOW SOME DRY AIR ABOVE 700 MB...AND WEAK SHEAR.
STILL EXPECT ENUF INSTBY AND SHEAR FOR STORMS TO DEVELOP DEEP
UPDRAFTS AND SOME ORGANIZATION INTO MULTI-CELL CLUSTERS LATE THIS
AFTN INTO THE EVENING ACRS THE MAINLY THE UPSTATE AND NE GA. THE
LATEST SPC DAY 1 KEEPS THE SLIGHT RISK IN THESE AREAS. SO THE MAIN
CHANGE TO THE TODAY PERIOD IS TO DELAY POPS AND CLOUDS. TEMPS/DEWPTS
LOOK ON TRACK. POPS AND QPF FOR TONIGHT STILL LOOK ON TRACK SO NO
CHANGES PAST THIS EVENING.

PREVIOUS DISCUSSION...
AS OF 700 AM...CLOUDINESS IS INCREASING FROM THE SW ACROSS THE UPPER
SAVANNAH RIVER VALLEY. SOME BRIEF MORNING FOG IS POSSIBLE...BUT THIS
SHOULD CLEAR UP QUICKLY. ALL LOCATIONS SHOULD HIT CONVECTIVE TEMPS
QUITE QUICKLY TODAY...ALLOWING THE CUMULUS FIELD TO FILL IN AND
CONVECTION TO START TRIGGERING FROM THE SW AS SFC WAVES MOVE NE
ALONG THE FRONT. THE FRONTAL BOUNDARY SHOULD GRADUALLY SLIP
SOUTHEAST TODAY...LIKELY APPROACHING THE INTERSTATE 85 CORRIDOR BY
LATE AFTERNOON. CONVECTIVE COVERAGE SHOULD CONTINUE TO BLOSSOM
ACROSS THE REGION THROUGH THE AFTN AS MOISTURE DEEPENS AND
CONVERGENCE INCREASES ALONG THE FRONTAL ZONE. A FAIRLY SHARP
GRADIENT IN POP WILL BE REQUIRED...WITH LOW END CATEGORICAL IN SW
SECTIONS...RANGING DOWN TO CHC IN THE NC NW PIEDMONT. SURFACE BASED
CAPE VALUES OF 1000 J/KG OR HIGHER WILL LIKELY POOL SOUTHEAST OF THE
FRONTAL ZONE...MAINLY OVER FOOTHILL AND PIEDMONT SECTIONS OF NE GA
AND UPSTATE SC THIS AFTN. MULTICELLULAR TSTMS WITH POSSIBLY DAMAGING
WINDS AND MARGINAL LARGE HAIL WILL BE FEATURED IN THE HWO FOR THIS
AFTN AND EVENING ACROSS THE SE HALF.

STRONGER UPPER SUPPORT WILL ARRIVE WITH THE DEEPEST MOISTURE
TONIGHT. THE RIGHT ENTRANCE REGION OF THE UPPER JETLET WILL PRODUCE
SOME 300 MB DIVERGENCE...AND DEEP LAYER Q VECTOR CONVERGENCE SHOULD
ARRIVE AHEAD OF THE APPROACHING SHORTWAVE FROM 06Z TO 12Z.
CATEGORICAL SHOWER COVERAGE IS EXPECTED THROUGHOUT...BUT INSTABILITY
REMAINS A QUESTION. WILL NEED TO KEEP AT LEAST AN ISOLD TO SCT
THUNDER MENTION EVERYWHERE AS THE COLUMN WILL BE STRONGLY
DYNAMICALLY FORCED AND 850 TO 500 MB LAPSE RATES WILL BE 6 DEG C/KM
OR BETTER IN MOST AREAS. UPGLIDE OVER THE FRONTAL ZONE WILL BE MOST
ACTIVE OVER WRN NC TONIGHT....WHERE THE RAIN COULD BE HEAVY AT
TIMES. HOWEVER...THE RECENT DRY CONDITIONS SHOULD PRECLUDE ANY HYDRO
PROBLEMS.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AT 0230 EDT TUESDAY...A WEAKENING UPPER TROUGH WILL CROSS THE
SOUTHERN APPALACHIANS ON WEDNESDAY...THEN MOVE OFFSHORE ON THURSDAY.
A COLD FRONT IN THE PIEDMONT WEDNESDAY MORNING WILL SLOWLY DRIFT
SOUTHEAST OF THE AREA. A WAVE ON THE FRONT TO THE SOUTH WILL PRODUCE
ISENTROPIC UPGLIDE OVER THE FRONT...RUSTLING IN PRECIPITATION WELL
BEHIND THE BOUNDARY INTO WEDNESDAY EVENING. PRECIPITATION AMOUNTS
COULD BE SUBSTANTIAL GIVE THE STRENGTH OF THE UPGLIDE. THIS UPGLIDE
SHIFTS EAST ON THURSDAY...WHEN DRYING OF THE MID LEVELS TAKES
PLACE.  LOW LEVELS REMAIN MOIST...AND LINGERING CLOUD COVER CAN BE
EXPECTED INTO THURSDAY NIGHT. TEMPERATURES WILL EXHIBIT A LOW
DIURNAL RANGE WEDNESDAY UNDER CLOUD COVER...THEN A SLIGHTLY GREATER
DIURNAL RANGE THURSDAY IN THE WAKE OF THE DEPARTING SYSTEM AND
PRECIPITATION.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AT 0230 EDT TUESDAY...AN UPPER TROUGH WILL MOVE FROM THE PLAINS ON
FRIDAY...TO THE SOUTHERN APPALACHIANS BY SUNDAY. THE ECMWF IS A BIT
FASTER WITH ITS TROUGH AXIS...WHILE THE GFS IS SLOWER. THE GFS
CLOSES OFF AN UPPER  LOW NEAR THE FL PANHANDLE SUNDAY...WHILE THE
ECMWF CLOSES OFF ITS LOW OVER THE CENTRAL APPALACHIANS. BOTH MODELS
PROGRESS THEIR LOWS TO THE EASTERN SEABOARD BY MONDAY...WITH THE GFS
LOW MUCH WEAKER AND FARTHER SOUTH. THE HPC MEDIUM RANGE FORECAST
INITIALLY FAVORED THE GFS SOLUTION...AS THE ECMWF WAS NORTHERN
OUTLIER WITH ITS UPPER SYSTEM...BUT THEIR DAY 7 SURFACE SYSTEM
POSITION RESEMBLES THE ECMWF.

ON FRIDAY OUR AREA IS BETWEEN A STATIONARY FRONT NEAR THE COAST...
AND A COLD FRONT IN THE MS RIVER VALLEY. THIS COLD FRONT REACHES THE
SOUTHERN APPALACHIANS ON SATURDAY MORNING...AND CROSSES OUR ARE
DURING THE DAY....BRINGING SHOWERS AND THUNDERSTORMS WITH IT. THE
FRONT OCCLUDES OVER CENTRAL NC ON SUNDAY...WITH ITS DEFORMATION ZONE
EXTENDING WEST OVER OUR AREA. THAT SHOULD KEEP PRECIPITATION
GOING...AND THE SLOW MOVEMENT OF THE SYSTEM...COMBINED WITH
SUBSTANTIAL FORCING...COULD PRODUCE SOME IMPRESSIVE RAINFALL.
ENOUGH INSTABILITY WITH THE MID LEVEL COLD POOL FOR THUNDERSTORMS TO
PERSIST BEHIND THE FRONT. THE SURFACE SYSTEM LIFTS NE UP THE COAST
ON MONDAY...LEAVING NW FLOW OVER THE MOUNTAINS IN ITS WAKE...IN VERY
LOW ECWMF THICKNESS VALUES FOR THIS TIME OF YEAR. WITH LOW
CONFIDENCE IN SUCH ABNORMAL THICKNESS VALUES...JUST A COLD RAIN WILL
BE CARRIED IN THE MOUNTAINS FOR NOW. TEMPERATURES WILL TREND
DOWNWARD FROM ABOVE NORMAL ON FRIDAY...TO BELOW NORMAL BY MONDAY...
AS HEIGHTS FALL AND COOLER AIR SETTLES OVER THE AREA IN THE WAKE OF
THE SYSTEM.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
AT KCLT...VFR LEVEL STRATOCUMULUS IS INCREASING ACROSS THE UPPER
SAVANNAH RIVER VALLEY TO THE SW THIS MORNING. KCLT HAS SHOWN NO VSBY
RESTRICTIONS...BUT CANNOT RULE OUT BRIEF MVFR SINCE THE AIRFIELD WAS
CLEAR MOST OF THE NIGHT. MODEL TIME HEIGHTS SHOW A GRADUAL INCREASE
AND LOWERING OF THE VFR CLOUDS THROUGH THE DAY...WITH CONVECTIVE
TEMPS BEING MET BY AROUND 16Z. THE SFC FRONT SHOULD APPROACH THE
VICINITY OF THE AIRFIELD THIS AFTN...WITH INSTABILITY POOLING ON THE
SE SIDE OF THE BOUNDARY NEAR THE INTERSTATE 85 CORRIDOR. WILL NOW
FEATURE VCTS AND CB CLOUD TYPE STARTING AT 20Z. WIDESPREAD SHRA
SHOULD THEN FOLLOW FOR THE TONIGHT PERIOD AS UPPER SUPPORT ARRIVES
FROM THE W ALONG WITH DEEPER MOISTURE AND RETURNING UPGLIDE OVER THE
FRONTAL ZONE. NRLY WINDS THIS MORNING WILL TURN NE AND STRENGTHEN
THROUGH THE PERIOD.

ELSEWHERE...VFR CLOUDINESS SHOULD STEADILY FILL BACK IN FROM THE SW
THROUGH THE DAY AS WEAK WAVES OF LOW PRESSURE MOVE NE ALONG A
FRONTAL ZONE STALLING ACROSS THE REGION. CANNOT RULE OUT SOME BRIEF
MVFR VSBY AT THE TAF SITES GIVEN THE MOSTLY CLEAR NIGHT...BUT VSBY
SHOULD RECOVER FAST. SHOWER COVERAGE SHOULD RAPIDLY INCREASE FROM
THE SW TOWARD NOON AS CONVECTIVE TEMPS ARE MET AND CONVERGENCE
INCREASES RAPIDLY ALONG THE FRONTAL ZONE. THE BEST CHANCE OF
THUNDERSTORMS WILL BE ACROSS THE UPSTATE SC TAF SITES WHERE
INSTABILITY WILL BE HIGHEST LATE THIS AFTN. SHRA COVERAGE SHOULD
INCREASE OVERNIGHT AS UPPER SUPPORT ARRIVES FROM THE WEST. SFC BASED
INSTABILITY WANES TONIGHT...BUT DEEP FORCING AND STEEP LAPSE RATES
ALOFT COULD WARRANT A CONTINUED THUNDER MENTION AT SOME POINT.
EXPECT WSW FLOW EARLY TO BECOME N TO NE LATER THIS MORNING...THEN
STRENGTHENING NELY THROUGH THE LATTER PERIOD.

OUTLOOK...THE FRONT WILL BE VERY SLOW TO CLEAR EAST OF THE REGION
THROUGH THE DAY ON WED. CONTINUED WIDESPREAD SHOWERS AND
RESTRICTIONS ARE LIKELY INTO WED...WITH A LINGERING MOIST BOUNDARY
LAYER LIKELY CREATING IFR RESTRICTIONS WED NIGHT BEFORE DRYING
BEGINS IN EARNEST THU. EXPECT MAINLY VFR CONDITIONS THROUGH
FRI...EXCEPT FOR POSSIBLE EARLY MORNING FOG. ANOTHER COLD FRONT WILL
LIKELY BRING PRECIPITATION AND RESTRICTIONS BACK INTO THE AREA OVER
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...JAT
NEAR TERM...ARK/HG
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...HG

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
328 AM EDT TUE APR 17 2012

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-181100-
RABUN-HABERSHAM-STEPHENS-FRANKLIN-HART-ELBERT-AVERY-ALEXANDER-
IREDELL-DAVIE-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-BUNCOMBE-CATAWBA-
ROWAN-GRAHAM-NORTHERN JACKSON-MACON-SOUTHERN JACKSON-TRANSYLVANIA-
HENDERSON-CLEVELAND-LINCOLN-GASTON-MECKLENBURG-CABARRUS-UNION NC-
CALDWELL MOUNTAINS-GREATER CALDWELL-BURKE MOUNTAINS-GREATER BURKE-
MCDOWELL MOUNTAINS-EASTERN MCDOWELL-RUTHERFORD MOUNTAINS-
GREATER RUTHERFORD-POLK MOUNTAINS-EASTERN POLK-OCONEE MOUNTAINS-
PICKENS MOUNTAINS-GREENVILLE MOUNTAINS-GREATER OCONEE-
GREATER PICKENS-GREATER GREENVILLE-SPARTANBURG-CHEROKEE-YORK-
ANDERSON-ABBEVILLE-LAURENS-UNION SC-CHESTER-GREENWOOD-
328 AM EDT TUE APR 17 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST GEORGIA...PIEDMONT
NORTH CAROLINA...WESTERN NORTH CAROLINA AND UPSTATE SOUTH CAROLINA.

.DAY ONE...TODAY AND TONIGHT.

A COLD FRONT IS EXPECTED TO STALL ACROSS THE WESTERN CAROLINAS AND
NORTHEAST GEORGIA TODAY. LOW PRESSURE MOVING NORTHEAST ALONG THE
FRONT WILL LIKELY TRIGGER THUNDERSTORMS THROUGH THE AFTERNOON AND
EVENING HOURS. THE COVERAGE OF THE THUNDERSTORMS WILL BE GREATEST
ACROSS NORTHEAST GEORGIA AND UPSTATE SOUTH CAROLINA...AND MORE
SCATTERED IN NATURE FARTHER NORTH INTO NORTH CAROLINA. ANY
THUNDERSTORMS THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE
CLOUD TO GROUND LIGHTNING...BRIEFLY GUSTY WINDS...AND VERY HEAVY
RAINFALL. A FEW THUNDERSTORMS COULD BECOME SEVERE...PRODUCING
DAMAGING WIND GUSTS IN EXCESS OF 60 MPH AND HAIL AS LARGE AS
QUARTERS. THE GREATEST THREAT OF SEVERE THUNDERSTORMS WILL BE
ACROSS NORTHEAST GEORGIA AND THE UPSTATE OF SOUTH CAROLINA THIS
AFTERNOON AND EVENING.

WIDESPREAD SHOWERS...WITH ISOLATED TO SCATTERED THUNDERSTORMS...WILL
LIKELY CONTINUE THROUGH THE OVERNIGHT HOURS. LOCALLY HEAVY
RAINFALL WILL BE POSSIBLE...ESPECIALLY ALONG THE EASTERN SLOPES OF
THE MOUNTAINS...AND THE ADJACENT FOOTHILLS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTERS ARE REQUESTED TO FORWARD ANY REPORTS OF LARGE
HAIL...DAMAGING WINDS...TORNADOES OR FLASH FLOODING TO OUR OFFICE.

GERAPETRITIS