River Flood Warning 4, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
258 PM EST THU JAN 17 2013

.SYNOPSIS...
LOW PRESSURE WILL MOVE ACROSS THE UPSTATE TONIGHT. EXPECT HIGH
PRESSURE TO PROVIDE DRIER AND SEASONABLY COOL WEATHER FOR THE
WEEKEND. THE COLDEST WEATHER IN QUITE A WHILE MAY ARRIVE NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
AS OF 215 PM...COMPACT UPR LOW NOW CROSSING AL ATTM...WITH A
STRENGTHENING DEFORMATION ZONE SNOW BAND ON N SIDE OF LOW ACRS NRN
AL INTO S-CENTRAL TN. THERE HAVE BEEN A FEW LGTNG STRIKES IN THE
BAND...INDICATIVE OF CONDITIONAL SYMMETRIC INSTABILITY (CSI). A DRY
SLOT IS JUST ENTERING THE WRN EDGE OF THE CWFA AND WILL TAPER OFF
THE WARM CONVEYOR BELT RAIN SHIELD FROM WEST TO EAST THE REST OF THE
AFTN INTO THE EVENING HOURS. GUIDANCE IN DECENT AGREEMENT ON THE
DEFORMATION ZONE TRACKING STRAIGHT ACRS THE CWFA THIS EVENING. THE
12Z NAM IN PARTICULAR SETS UP STRONG 850 MB FRONTOGENESIS WITH THE
FN VECTOR CONVERGENCE RIGHT ALONG I-85. AS THE LOW WRAPS UP...A
TROWAL WILL KEEPING SUPPLYING MOISTURE AND CSI INTO THE DEFORMATION
ZONE AS IT CROSSES THE CWFA. A NAM CROSS SECTION PERPENDICULAR TO
THE ZONE SHOWS NEG GEOSTROPHIC EPV IN THE MID LVLS WITH THE STRONG
OMEGA AND IDEAL DENDRITIC ICE GROWTH ZONE. ALL THIS MEANS THAT
CONDITIONS WILL SUPPORT A NARROW INTENSE BAND OF PRECIP...WHICH WILL
LIKELY CHANGEOVER TO MOD-HVY SNOW. CONFIDENCE ON WHEN AND EXACTLY
WHERE THE BAND SETS UP IS STILL LOW. STILL THINKING IT WILL DEVELOP
ALONG I-85 IN NE GA AND CONTINUE TO PROPAGATE NEWD TO THE CHARLOTTE
METRO AREA LATER THIS EVENING. LLVL CAA WILL HELP THE TRANSITION
FROM THE TOP-DOWN IN THE MTNS AND FROM THE NE TO SW ACRS THE
PIEDMONT. SO STILL EXPECTING 5-8" IN THE NRN MTNS...3-5" ABV 3500FT
IN THE CENTRAL MTNS AND OUT ACRS THE NC FOOTHILLS AND NW PIEDMONT.
SNOW ACCUM TO THE SOUTH ARE MORE UNCERTAIN...AS IT DEPENDS ON WHEN
THE CHANGEOVER OCCURS AND WHERE THE BAND SETS UP. BASED ON THE
TRENDS...I THINK THE CURRENT WINTER STORM WARNINGS AND WINTER WX
ADVISORIES LOOK GOOD.

ANOTHER CONCERN IS ONGOING FLOODING/HYDRO WITHIN OUR FLOOD WATCH. AS
PREVIOUSLY MENTIONED...THE HEAVY RAIN SHUD TAPER OFF FROM WEST TO
EAST WITHIN THE NEXT FEW HOURS. SO SOME FLOODING MAY WORSEN BEFORE
RAIN ENDS...BUT THEN MAINLY BE DEALING WITH RUNOFF FROM MID EVENING
ONWARD. WILL LET THE FLOOD WATCH CONTINUE FOR NOW AND ASSESS RIVER
LEVELS ONCE THE RAIN TAPERS OFF/TRANSITIONS TO SNOW.

ONE OTHER THING TO NOTE IS THAT LLVL WINDS WILL REALLY INCREASE AS
THE LOW CROSSES THE AREA THIS EVENING. BOTH THE NAM AND GFS 925MB
WINDS ARE 40-50 KTS ACRS THE PIEDMONT AROUND 00Z. CERTAINLY EXPECT
PERIOD GUSTS IN THE 25 TO 35 MPH RANGE. EVEN THESE WINDS MAY KNOCK
DOWN A FEW TREES. WINDS WILL TAPER OFF LATEST IN THE MTNS. THIS MAY
COMBINE WITH HEAVY SNOW ACCUM TO DOWN TREES AND LIMBS. THESE HAZARDS
WILL BE MENTIONED IN THE WINTER HAZARD PRODUCTS.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
AS OF 215 PM THU...BIG CHANGE IN THE SHORT TERM AS LITTLE IN THE WAY
OF SENSIBLE WX DEVELOPS. HOWEVER...THERE WILL LIKELY BE SOME SNOW
COVERED ROADS AND/OR LINGERING BLACK FRI MORNING. OTHERWISE...
CLEARING SKIES AND SLACKENING WIND EXPECTED THRU THE DAY AS HIGH
PRESSURE BUILDS INTO THE AREA FROM THE NW. HIGHS WILL BE NEAR NORMAL
SOUTH TO 5 DEGREES BELOW NORTH WITH SNOW COVER EVEN UNDER SUNNY
SKIES. SHUD BE GOOD RADIATIONAL CONDITIONS FRI NITE WITH HIGH
PRESSURE REMAINING OVERHEAD. LOWS AS MUCH AS 5 DEGREES BELOW NORMAL.

NEARLY ZONAL FLOW DEVELOPS OVER THE AREA SAT AND SUN. SFC HIGH
PRESSURE REMAINS OVER THE AREA SAT BUT MOVES EAST SUN AS A WAVE
MOVING THRU THE ZONAL FLOW PUSHES A WEAK/DRY COLD FRONT ACROSS THE
AREA SUN. EXPECT SOME INCREASING CLOUDS OVER THE MTNS AS THE FRONT
MOVES THRU...BUT NO PRECIP. HIGHS SAT AND LOWS SAT NITE WILL BE NEAR
NORMAL. HIGHS SUN WILL BE NEAR NORMAL MTNS AND A LITTLE ABOVE
ELSEWHERE.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
AS OF 225 PM THU...THE FIRST PART OF THE MEDIUM RANGE WILL BE
DOMINATED BY A DEVELOPING ERN CONUS TROF AND AN ARCTIC AIR MASS. A
SHORT WAVE MOVES THRU THE TROF DURING THE MON NITE TIME FRAME WITH
ANOTHER WAVE FOR THE TUE NITE/WED TIME FRAME. THE WAVES WILL LEAD TO
A COUPLE OF CLIPPER-TYPE SYSTEMS MOVING NEAR OR NORTH OF THE AREA AS
AN ARCTIC HIGH SETTLES IN. LATEST GUIDANCE DOES INCREASE SOME CLOUDS
ACROSS THE MTNS WITH THESE WAVES...BUT ARE NOW DRY WITH NO NW FLOW
SNOWFALL FOR THE NRN MTNS. THEREFORE...HAVE REMOVED ANY SLIGHT CHC
SNOW WORDING. HAVE RETAINED THE VERY COLD TEMPS FOR TUE AND WED IN
LINE WITH HPC GUIDANCE. THE GFS AND ECMWF HAVE SIMILAR COLD H85
TEMPS WITH THE GEFS MEAN H85 TEMPS MAINLY 1 TO 1.5 SD BELOW
NORMAL...BUT APPROACHING 2 MON NITE. SO THE COLDER TREND STILL SEEMS
ON TRACK. TEMPS ON WED ARE NOT QUITE AS BELOW NORMAL. HEIGHTS RISE
THU AS SHORT WAVE RIDGING BUILDS IN AHEAD OF A DEEP TROF MOVING INTO
THE CENTRAL CONUS. THIS SYSTEM PUSHES A SFC FRONT TOWARD THE AREA
THU. LATEST MDL RUNS KEEP THE AREA DRY THRU THU...SO HAVE FOLLOWED
THAT TREND AS WELL. TEMPS WILL REBOUND TO A LITTLE BELOW NORMAL.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
AT KCLT...CIGS HAVE IMPROVED SOMEWHAT THRU MIDDAY...BUT ARE EXPECTED
TO BE IFR THRU THE DAY...AND MAY LOWER BACK TO LIFR AGAIN THIS
EVENING. STILL EXPECTING PERIODS OF +RA THRU THE AFTN...WITH A QUICK
TRANSITION TO SNOW IN THE 01Z TO 03Z TIME FRAME. THE SNOW MAY BE
HEAVY FOR AN HOUR OR TWO...THEN SHUD QUICKLY TAPER OFF BY 06Z. SKIES
ARE EXPECTED TO THEN CLEAR OUT BY DAYBREAK FRIDAY. WINDS WILL REMAIN
GUSTY OUT OF THE NE. PROBABLY STRONGEST IN THE 00Z TO 03Z TIME
FRAME. THEN DIMINISH OVERNIGHT AND TURN TO MORE OF A N/NW DIRECTION.

ELSEWHERE...WIDESPREAD AREA OF RA/+RA CURRENTLY AFFECTING ALL TAF
SITES. PRECIP MAY TAPER OFF LATE THIS AFTN/EARLY EVENING ACRS THE
UPSTATE DUE TO A DRY SLOT. BUT ANOTHER BAND OF PRECIP IS EXPECTED TO
DEVELOP THIS EVENING. GUIDANCE INDICATES POTENTIAL FOR A NARROW
INTENSE BAND THAT WILL LIKELY CHANGEOVER TO SNOW IN THE UPSTATE.
HAVE MENTIONED SNOW AT ALL SITES AS PRECIP TAPERS OFF IN THE 00Z TO
04Z TIME FRAME. THERE MAY BE SOME ICING CONCERNS...BUT TEMPS WILL
HOVER IN THE LWR-MID 30S OVERNIGHT. AT KAVL AND KHKY...EXPECTING
LONGER PERIOD OF ACCUMULATING SNOW...WITH A FEW INCHES OF TOTAL
ACCUM POSSIBLE. CONDITIONS SHUD RAPIDLY IMPROVE OVERNIGHT...AS SKIES
CLEAR AND WINDS DIMINISH AND TURN FROM NE TO NW.

OUTLOOK...DRY HIGH PRESSURE WILL BEGIN BUILDING OVER THE REGION
EARLY FRIDAY AND WILL REMAIN THROUGH THE WEEKEND.

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

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...FLOOD WATCH UNTIL MIDNIGHT EST TONIGHT FOR GAZ010-017.
     WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR GAZ010-
     017.
     WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM EST
     FRIDAY FOR GAZ018-026-028.
NC...FLOOD WATCH UNTIL MIDNIGHT EST TONIGHT FOR NCZ033-035-048>053-
     058-059-062>065-501>510.
     WINTER STORM WARNING UNTIL MIDNIGHT EST TONIGHT FOR NCZ033-
     048>053-058-059-062>065-501>507-509.
     WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR NCZ051-
     058-059-062-063.
     WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM EST
     FRIDAY FOR NCZ082.
     WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 AM EST FRIDAY
     FOR NCZ035>037-056-057-068>072-508-510.
SC...FLOOD WATCH UNTIL MIDNIGHT EST TONIGHT FOR SCZ001>007-010.
     WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR
     SCZ001>003.
     WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM EST
     FRIDAY FOR SCZ004>010.

&&

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

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