National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS62 KGSP 171109
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
709 AM EDT MON MAR 17 2014

.SYNOPSIS...
WAVES OF LOW PRESSURE WILL MOVE NORTHEAST FROM FLORIDA TO ALONG THE
CAROLINA COAST THROUGH TUESDAY. COLD HIGH PRESSURE NEAR NEW YORK
STATE WILL BRING A COOL NORTHEAST BREEZE EAST OF THE MOUNTAINS WHICH
WILL RESULT IN WINTRY PRECIPITATION FOR SOME OF OUR AREA MONDAY
NIGHT AND EARLY TUESDAY.  EXPECT A WEAK COLD FRONT TO CROSS OUR
REGION LATE WEDNESDAY.  HIGH PRESSURE WILL BE IN CONTROL THURSDAY
AND FRIDAY.  EXPECT ANOTHER COLD FRONT TO CROSS ON SATURDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 645 AM EDT...OBS AND LAPS ANALYSIS HAVE FREEZING TEMPS FROM
THE NRN BLUE RIDGE TO TAYLORSVILLE TO MOCKSVILLE...WITH SPOTTY
FREEZING TEMPS AS FAR SOUTH AS SALISBURY TO OLD FORT. UPDATED THE
FORECAST TO ADD SLIGHTLY MORE ICING ALONG THE ERN SLOPES OF THE BLUE
RIDGE THIS MORNING AS BETTER SHOWERS ARE WORKING NE ALONG THE HIGHER
TERRAIN INTO THE SUBFREEZING TEMPS FROM JONAS RIDGE TO NEAR BLOWING
ROCK. AN SPS HAS BEEN ISSUED FOR ROWAN COUNTY...BUT THE ADVISORY
MIGHT NEED TO BE EXPANDED IF BETTER LIGHT RAIN GETS INTO THE
SALISBURY AREA THIS MORNING. OTHERWISE...THE FORECAST IS ON TRACK
WITH A TROUGH AXIS MOVING THROUGH THE LOWER MS RIVER VALLEY...A
CLOSED CIRCULATION DEVELOPING FARTHER SW OVER THE TX GULF
COAST...AND DEEPER MOISTURE STREAMING TOWARD THE FORECAST AREA. AT
THE SFC...THE CAD BOUNDARY WRAPS NEATLY AROUND THE SRN PERIPHERY OF
THE FORECAST AREA...WITH FREEZING TEMPS NOW SOLIDLY IN PLACE NORTH
OF INTERSTATE 40 AND ALONG THE NRN BLUE RIDGE. SOME WEAK CONVECTIVE
ELEMENTS CONTINUE TO RIDE UP THE MTNS IN SW FLOW ALOFT...SENDING
BETTER PRECIP RATES INTO THE NRN TIER WHERE ICING POTENTIAL WILL
CONTINUE THROUGH THE MORNING HOURS.

THE NRN PORTION OF THE UPSTREAM TROUGH WILL MOVE EWD TO THE BASE OF
THE SRN APPALACHIANS THROUGH THE DAY...WHILE THE MORE AMPLIFIED SRN
WAVE SWEEPS EAST ALONG THE GULF COAST. SFC LOW PRES OVER WRN GA
EARLY THIS MORNING WILL SLIDE E ALONG THE WEDGE FRONT TODAY AND MOVE
OFF THE CAROLINA COAST. A POCKET OF BETTER MID LEVEL LAPSE RATES
WILL LIFT NWD ACROSS THE MTNS AND THE CAD LAYER TODAY...BUT ANY
ELEVATED CONVECTION SHOULD REMAIN FAIRLY SHALLOW. BETWEEN LINGERING
UPPER JET DIVERGENCE...WEAK ISENTROPIC LIFT...AND SCATTERED SHOWERS
IN THE BETTER MOISTURE FEED...WILL MAINLY LIKELY POPS AT TIMES...AND
EMBEDDED DRIZZLE BETWEEN THE SHOWERS. THIS WILL KEEP TEMPERATURES
LOCKED IN IN THE 30S AND LOWER 40S THIS AFTN FOR MOST OF THE
AREA...EXCEPT FOR SOME LOWER 50S IN THE FAR SW MTNS.

THE BEST DYNAMICS WITH THE DEAMPLIFYING SRN WAVE WILL LIKELY PASS
MAINLY SE OF THE REGION TONIGHT. EXPECT MID LEVELS OF THE ATMOSPHERE
TO DRY OUT FROM THE WEST TONIGHT BEHIND THE WAVE...WITH ISENTROPIC
LIFT TAPERING OFF. ALSO...A NE GULF OF MEXICO SFC LOW ASSOCIATED
WITH THE SRN WAVE WILL TRANSITION TO A DEEPENING OFFSHORE WATERS LOW
OVERNIGHT...SENDING COOLER AIR SPILLING SWD INTO THE CAROLINAS.
HOWEVER...THE NAM ONCE AGAIN APPEARS OVERDONE WITH THE DEGREE OF
COOLING SO WILL LEAN TOWARD A GFS/ECMWF BLEND ON SFC TEMPS. IN
ADDITION...MINIMAL PRECIPITATION AND LIMITED ICE NUCLEATION IN
SOUNDINGS WILL SEVERELY LIMIT THE POTENTIAL FOR ICE ACCRETION IN THE
COLDEST NRN TIER AREAS TONIGHT. IT THUS APPEARS THAT FREEZING
DRIZZLE ACROSS PARTS OF WRN NC TONIGHT WILL BE THE PRIMARY THREAT.
WILL HOLD OFF ON ANY ADDITIONAL ADVISORIES AT THIS POINT GIVEN THE
UNCERTAINTY OVER THE SWD PENTRATION OF SUBFREEZING TEMPS AND THE QPF.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 300 AM MONDAY...THE SRN STREAM SHORTWAVE TROF WILL FINALLY GET
EJECTED OUT INTO THE CAROLINA COASTAL WATERS BY EARLY
TUESDAY...TAKING THE DEEPER MOISTURE AND LIFT EAST OF THE AREA. THE
NAM AND GFS IN GOOD AGREEMENT ON VERY SHALLOW MOIST LAYER LINGERING
ON BACK SIDE OF THE SYSTEM...AS COLD AIR DAMMING/WEDGE HOLDS ON
AHEAD OF THE DEEPER NRN STREAM TROF ENTERING THE UPR MIDWEST. ALL
THE OP MODELS SEEM TO AGREE ON LTL IF ANY ADDITIONAL QPF RESPONSE
AFTER 12Z TUESDAY. SO I HAVE POPS TAPERING OFF WITH MUST A MENTION
OF SOME SLGT CHC -RA AND DZ FOR TUESDAY MORNING. THE LLVL FLOW WILL
BACK OUT OF THE SE...WITH THE APPROACH OF THE NEXT SYSTEM. THE FCST
SNDGS SHOW A PERSISTENT INVERSION WITH MOIST UPSLOPE FLOW
DEVELOPING. THE MOIST LAYER DEEPENS TO A FEW THOUSAND FEET BY
TUESDAY EVENING. SO I HAVE POPS RAMP UP TO SLGT CHC TO LOW-END
CHC...FAVORING THE BLUE RIDGE/SE-FACING SLOPES. QPF SHUD BE SPOTTY
AND VERY LIGHT. WITH PLENTY OF STRATUS LIKELY TO REMAIN THRU THE
DAY...TEMPS WILL BE HELD IN THE 40S ALONG AND EAST OF THE BLUE
RIDGE...AND INTO THE 50S WHERE CLOUDS CAN CLEAR OUT IN THE HIGH
TERRAIN AND SW NC MTN VLYS. AGAIN THE NAM IS A COLD
OUTLIER...BRINGING SUBFREEZING TEMPS TO NRN BLUE RIDGE...AS THE SELY
UPSLOPE INCREASES. SINCE THE NAM HAS BEEN WAY TOO COLD SO FAR WITH
THIS CURRENT CAD EVENT...I DID NOT GO THAT COLD WITH TEMPS. SO NOT
EXPECTING ANY FREEZING RAIN/DRIZZLE TUESDAY NIGHT.

WEDNESDAY AND WEDNESDAY NIGHT...THE NRN STREAM TROF WILL QUICKLY
TRACK THRU THE GREAT LAKES...WITH A SFC LOW UNDERNEATH. THE LOW WILL
DRAG A COLD FRONT ACRS THE OH VLY. THE FRONT LOOKS QUITE DRY IN
PRETTY MUCH ALL THE GUIDANCE. IN FACT...THE MODEL QPF FIELDS SHOW
MORE RESPONSE WITH THE UPSLOPE/UPGLIDE AHEAD OF THE FRONT. I WILL
KEEP A SLGT CHC IN FOR WEDNESDAY...BUT EVEN THAT MAY BE OVERDONE.
THE FRONT WILL BE STRONG ENUF TO SCOUR OUT THE CAD/STRATUS...AND
ALLOW TEMPS TO WARM BACK INTO THE UPR 50S TO MID 60S (NEAR NORMAL).
SKIES CONTINUE TO CLEAR WEDNESDAY NIGHT...AND LLVL NWLY CAA FLOW
WILL BRING TEMPS DOWN INTO THE 30S MTNS AND UPR 30S TO LWR 40S
PIEDMONT BY THURSDAY MORNING.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 200 AM EDT MONDAY...THE MEDIUM RANGE PERIOD STARTS AT 12Z
THURSDAY WITH HIGH PRESSURE BUILDING IN FROM THE WEST AND TRANSITING
TO OFF THE CAROLINA COAST LATE FRIDAY. THE CANADIAN MODEL IS THE ONE
IN DISAGREEMENT AS IT BRINGS A SHORTWAVE WEST TO EAST ACROSS OUR
REGION LATE THURSDAY WITH A THIRD OF AN INCH OR LESS QPF. THIS IS
NOT ON THE GFS AND ECMWF AND PREFER TO KEEP IT OUT OF THE CURRENT
FORECAST. THE NEXT COLD FRONT CROSSES FROM THE NW ON SATURDAY
BRINGING A QUARTER OF AN INCH OF RAIN OR LESS THEN MOVES IT SE WITH
A 1030 HIGH PRESSURE CENTERED NEAR NRN ILLINOIS AT 12Z SUNDAY. ALL
PRECIP WITH THE FRONTAL PASSAGE WILL BE LIQUID FORM AS TEMPS SHOULD
BE WAY TOO WARM FOR ANYTHING ELSE. THIS HIGH IS FORECAST TO MOVE
TOWARD THE MID ATLANTIC BY 12Z MONDAY CONTINUING DRY WEATHER FOR
MUCH OF THE EASTERN STATES. BOTH THE GFS AND ECMWF SHOW A BROAD
UPPER TROUGH OVER THE EASTERN TWO THIRDS OF THE NATION NEXT SUNDAY
WITH UPPER RIDGING OVER CALIFORNIA. OUR TEMPS WILL BE A LITTLE ABOVE
NORMAL THUR THROUGH SAT AND THEN DROP BEHIND THE FRONT TO A LITTLE
BELOW NORMAL.

&&

.AVIATION /11Z MONDAY THROUGH FRIDAY/...
AT KCLT...PERSISTENT NE FLOW IN THE EXISTING CAD LAYER WILL CONTINUE
TO BRING COOLER TEMPERATURES IN FROM THE NE...BUT FAVOR RAP/GFS
PROFILES OVER NAM IN NOT PRODUCING ANY FZRA OR FZDZ THIS MORNING.
EXPECT MAINLY LIGHT RAIN AND DRIZZLE TODAY ALONG WITH IFR TO LIFR
CIGS. TEMPS WILL COOL FURTHER TONIGHT...AND FZDZ COULD MAKE A RUN AT
THE TERMINAL IN THE 08Z TO 12Z TIME FRAME. A PROB30 GROUP FOR FZDZ
WILL BE ADDED TO THE TAF.

AT KHKY...NE FLOW AND LIFR TO IFR CIGS WILL PERSIST AT KHKY ALONG
WITH MAINLY RAIN AND DRIZZLE TODAY. A NARROW WINDOW OF LIGHT FZRA IS
IN PLACE THROUGH ABOUT 15Z. BETTER COOLING OF TEMPS ON THE NE FLOW
TONIGHT WILL INCREASE FZDZ CHANCES AFTER 04Z.

ELSEWHERE...EXPECT MAINLY LIFR TO IFR CIGS THROUGH THE PERIOD WITH
RAIN OR DRIZZLE AT TIMES. NE FLOW WILL CONTINUE AT THE UPSTATE TAF
SITES IN THE COLD AIR DAMMING LAYER...WHILE FLOW WILL BE MORE SRLY
INITIALLY AT KAVL...BECOMING NW LATER IN THE PERIOD. WILL KEEP ANY
FZRA OR FZDZ MENTION FOR TONIGHT OUT OF THE FORECAST AT
PRESENT...BUT IT COULD GET CLOSE TO A KAVL TO KGSP LINE TOWARD THE
END OF PERIOD IF ANY PRECIP LINGERS.

OUTLOOK...COLD AIR DAMMING AND ASSOCIATED LOW RESTRICTIONS WILL
LINGER THROUGH TUE BEFORE SLOWLY SCOURING AHEAD OF THE NEXT
APPROACHING FRONT TUE NIGHT INTO WED. DRYING HIGH PRES WILL RETURN
THU INTO FRI.

CONFIDENCE TABLE...

            11-17Z        17-23Z        23-05Z        05-11Z
KCLT       MED   72%     MED   73%     HIGH  82%     HIGH  90%
KGSP       MED   64%     HIGH  80%     MED   77%     MED   71%
KAVL       MED   74%     MED   76%     HIGH  82%     HIGH  81%
KHKY       MED   65%     MED   73%     HIGH  82%     HIGH  82%
KGMU       MED   69%     HIGH  80%     MED   69%     MED   71%
KAND       MED   71%     HIGH  80%     MED   74%     MED   75%

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 EDT TODAY FOR NCZ033-
     035>037-049-050-056-501>506.
SC...NONE.

&&

$$
SYNOPSIS...DEO
NEAR TERM...HG
SHORT TERM...ARK
LONG TERM...DEO
AVIATION...HG