413  
FXUS62 KGSP 162352  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
652 PM EST WED JAN 16 2019  
   
SYNOPSIS
 
 
DRY HIGH PRESSURE WILL CONTINUE SEASONAL WEATHER INTO THURSDAY. A  
WEAK COLD FRONT WILL CROSS THE AREA THURSDAY NIGHT...BEFORE A  
STRONGER AND WETTER SYSTEM AFFECTS THE REGION OVER THE WEEKEND. VERY  
COLD HIGH PRESSURE WILL BUILD ACROSS THE SOUTHEAST EARLY NEXT WEEK.  
 

 
   
NEAR TERM /THROUGH THURSDAY/
 
 
AS OF 646 PM EST WEDNESDAY: FCST REMAINS ON TRACK THIS EVENING,  
WITH LOW CLOUDS BANKED UP AGAINST THE WEST SIDE OF THE MTNS BUT  
NOT MAKING ANY IN-ROADS OVER THE HIGHER TERRAIN. TEMP TREND WAS  
A MIXED BAG. NO BIG CHANGES.  
 
OTHERWISE, SHORT WAVE RIDGING TONIGHT WILL MOVE EAST THURSDAY  
REPLACED BY A SHORT WAVE TROUGH MOVING IN FROM THE WEST. WEAK  
HIGH PRESSURE BUILDS IN FROM THE NORTHEAST TONIGHT BEFORE A WEAK  
SURFACE LOW MOVES EAST INTO THE GREAT LAKES REGION DRAGGING A  
COLD FRONT INTO THE OHIO AND TENNESSEE VALLEYS. EXPECT MAINLY  
CIRRUS OVERNIGHT. HOWEVER, THERE COULD BE LOW CLOUDS FORMING TOWARD  
DAYBREAK AS WEAK ISENTROPIC LIFT DEVELOPS ALONG WITH SOME INCREASE  
IN LOW LEVEL MOISTURE. THERE WILL LIKELY BE FOG OR LOW CLOUDS IN  
THE MOUNTAIN VALLEYS AND UPPER SAVANNAH RIVER VALLEY. LOWS TONIGHT  
WILL BE NEAR TO SLIGHTLY ABOVE NORMAL.  
 
ALTHOUGH THERE IS AN INCREASE IN LOW LEVEL MOISTURE THURSDAY MORNING  
AHEAD OF THE COLD FRONT, DEEPER MOISTURE AND BETTER ISENTROPIC LIFT  
DOESN'T MOVE IN UNTIL THE AFTERNOON. KEEP POP LOW UNTIL THEN WITH  
A QUICK RAMP UPWARD ACROSS THE AREA DURING THE AFTERNOON. AS FOR P-  
TYPE, PRECIP SHOULD BE RAIN, POSSIBLY MIXED WITH A LITTLE SLEET AT  
ONSET AS WET BULBING OCCURS, FOR MOST LOCATIONS. THE EXCEPTION IS  
THE NORTHERN MOUNTAINS WHERE PROFILES AND SURFACE TEMPS WILL BE  
COLD ENOUGH FOR SOME TYPE OF MIXED PRECIP BEFORE WARMING OCCURS  
CHANGING THE PRECIP TO ALL RAIN. THE GFS HAS COME IN COLDER  
THAN PREVIOUS RUNS AND SHOWS SNOW CHANGING TO RAIN. THE NAM HAS  
BEEN MORE CONSISTENT SHOWING A STRONG WARM NOSE WITH SNOW/SLEET  
CHANGING TO FREEZING RAIN THEN RAIN. THIS IS EVEN WITH THE PRECIP  
ONSET MAINLY LATE MORNING TO EARLY AFTERNOON. USING A BLEND, THE  
FORECAST SHOWS A SLEET/FREEZING RAIN MIX CHANGING TO FREEZING RAIN  
THEN RAIN. EITHER WAY, GIVEN THE LIGHT QPF AND STRONG WARM NOSE,  
ANY SLEET ACCUMS OR ICE ACCRETION WILL BE VERY LIGHT AND LIMITED TO  
THE HIGHER ELEVATIONS. HIGHS WILL BE UP TO 5 DEGREES BELOW NORMAL.  
 

 
   
SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/
 
 
AS OF 245 PM WEDNESDAY: SHOWER ACTIVITY IS EXPECTED TO GRADUALLY  
DIMINISH FRIDAY MORNING WITH POSSIBLY A FEW LINGERING SHOWERS INTO  
THE AFTERNOON AT THE NC/TN LINE AS THE SHORT WAVE ASSOCIATED WITH  
THE WEAK SYSTEM PUSHES OFF THE CAROLINA COAST. CANNOT RULE OUT SNOW  
OR SLEET BRIEFLY MIXING IN WITH THE SHOWERS ACROSS THE NORTHERN  
MOUNTAINS, ALTHOUGH IMPACTS WOULD BE MINIMAL IF ANY. LEFT OVER LOW  
LEVEL MOISTURE MAY SUPPORT LOW CLOUDS OR FOG FOR SOME AREAS AND MAY  
DELAY DIURNAL HEATING A BIT. OTHERWISE MOSTLY SUNNY SKIES ARE  
EXPECTED BY THE AFTERNOON, EXCEPT IN THE MOUNTAINS NEAR THE TN  
BORDER WHERE PARTLY TO MOSTLY CLOUDY SKIES MAY PERSIST. HIGHS FRIDAY  
ARE EXPECTED TO BE SEVERAL DEGREES ABOVE NORMAL WITH HIGHS IN THE  
50S TO NEAR 60. WEAK NORTHWEST FLOW TURNS SOUTHWEST FRIDAY EVENING  
AND NIGHT WITH INCREASING MOISTURE INITIALLY ALOFT IN ADVANCE OF THE  
NEXT STORM SYSTEM. THIS WILL SUPPORT INCREASING HIGH CLOUDS FRIDAY  
NIGHT. THIS COMBINED WITH INCREASING WARM AIR ADVECTION WITH SUPPORT  
LOW TEMPERATURES ABOUT 10 DEGREES ABOVE NORMAL WITH 40S FOR MANY  
AREAS ESPECIALLY OUTSIDE OF THE MOUNTAINS.  
 
A VIGOROUS SOUTHERN STREAM SHORTWAVE TROUGH OVER THE ROCKIES TO  
BEGIN THE SHORT TERM FRIDAY WILL DROP SOUTHEAST WHILE GRADUALLY  
PHASING WITH NORTHERN STREAM ENERGY SATURDAY, SUPPORTING DEEPENING  
OF THE TROUGH ACROSS THE MISSISSIPPI VALLEY. SOUTHERLY FLOW WILL  
DEVELOP AND STRENGTHEN FAIRLY RAPIDLY SATURDAY IN ADVANCE OF THE  
ASSOCIATED COLD FRONT PUSHING EAST THROUGH THE GULF COAST STATES.  
THIS WILL SUPPORT CONTINUED INCREASING MID TO EVENTUALLY LOW LEVEL  
CLOUDS WITH LIGHT RAIN DEVELOPING FIRST ACROSS THE SOUTHWEST  
MOUNTAINS EARLY IN THE DAY, SPREAD ACROSS MOST OF THE REGION BY  
SATURDAY EVENING. ALL RAIN IS EXPECTED AS THE FA WILL BE IN THE WARM  
SECTOR OF THE STORM. AMOUNTS WILL GENERALLY BE LIGHT THROUGH  
SATURDAY EVENING. HIGHS SATURDAY WILL BE LARGELY DEPENDENT ON THE  
ONSET OF RAIN WITH THE CURRENT FORECAST GOING WITH HIGHS GENERALLY  
IN THE 50S. BREEZY SOUTHERLY WINDS ARE LIKELY ACROSS HIGHER TERRAIN  
BY SATURDAY EVENING WITH GUSTS IN EXCESS OF 30 MPH LIKELY.  
 

 
   
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
 
 
AS OF 200 PM WED: THOUGH SOME TIMING DIFFERENCES REMAIN, THE MAJOR  
GLOBAL MODELS HAVE CONVERGED ON A SOLUTION FEATURING NORTHERN- AND  
SOUTHERN-STREAM SHORTWAVES COMING INTO PHASE AS THEY SWING INTO THE  
EASTERN CONUS LATE IN THE WEEKEND. THE RESULT IS A FULL-LATITUDE  
TROUGH REACHING THE EASTERN SEABOARD BY EARLY MONDAY. IN RESPONSE,  
FROM SATURDAY NIGHT ONWARD, A DEEP SFC LOW WILL DRIVE FROM THE  
TENNESSEE VALLEY TOWARD THE NEW ENGLAND COAST. A POWERFUL COLD FRONT,  
ARGUABLY THE STRONGEST WE HAVE EXPERIENCED THIS WINTER, WILL PUSH  
THRU THE CWFA EARLY SUNDAY.  
 
THE FA WILL BE IN THE WARM SECTOR AT THE START OF THE PERIOD (00Z  
SUN), WITH RAINFALL RATES COMING TO A HEAD SOON THEREAFTER AS THE SFC  
FRONT ENTERS THE AREA ALONG WITH STRONG DIVERGENCE/DPVA ALOFT. THE EC  
AND CANADIAN ARE A FEW HOURS SLOWER THAN THE GFS IN BRINGING IN THE  
COLD FRONT, SO OUR FCST POPS WILL DECLINE A BIT MORE SLOWLY EAST OF  
THE MTNS THAN THE GFS WOULD SUGGEST. THAT SAID, THE NECESSARY  
INGREDIENTS FOR A QUICK-HITTING NORTHWEST FLOW SNOW EVENT STILL LOOK  
LIKE THEY WILL COME TOGETHER FOR A BRIEF TIME EARLY SUNDAY, WHILE  
MOISTURE AND COLD AIR OVERLAP. THE STRONG UPSLOPE WINDS APPEAR TO BE  
A LOCK BASED ON THE GLOBAL MODEL CONSENSUS, WHICH WILL OCCUR IN  
CONJUNCTION WITH THE AFOREMENTIONED DPVA. BACKWARD TRAJECTORIES AND  
925/850MB WIND FIELDS SUGGEST PARCELS WILL HAVE PASSED OVER THE  
EASTERN GREAT LAKES, A PHENOMENON ASSOCIATED WITH MORE EFFICIENT  
SNOWFALL RATES. FAVORABLE UPSLOPE WINDS CONTINUE LATER SUNDAY, THOUGH  
MOISTURE DOES BECOME A BIT QUESTIONABLE, PARTICULARLY IF THE DRIER  
LOW LEVELS DEPICTED ON THE EC VERIFY. THAT SAID, THE RAPID COOLING  
ALOFT SUGGESTS THE REMAINING MOISTURE AT THAT TIME WILL BE AT  
TEMPERATURES FAVORABLE FOR SNOW GROWTH. WE WILL PRUDENTLY ADVERTISE  
ONLY A GRADUAL DECLINE IN POPS INTO LATE SUNDAY. EVENT TOTAL SNOWFALL  
RIGHT NOW LOOKS LIKE IT EVENTUALLY MAY WARRANT A WINTER WEATHER  
ADVISORY FOR THE MTNS, BUT THERE IS PLENTY OF TIME FOR VALUES TO  
CHANGE. OUR ATTENTION FOR IMPACT WEATHER THEN TURNS TO THE BITTERLY  
COLD AIR PUSHING INTO THE REGION. SUB-ZERO WIND CHILLS ARE EXPECTED  
ACROSS MUCH OF THE MOUNTAIN ZONES MONDAY MORNING. TEMPS MONDAY HAVE  
BEEN LEANED IN FAVOR OF THE COLDER ECMWF NUMBERS, WHICH VERIFIED  
BETTER THAN THE COMMON BLENDS IN OUR LAST MAJOR ARCTIC OUTBREAK.  
MAXES LOOK TO BE 10 TO 15 DEGREES BELOW CLIMO.  
 
A SHORTWAVE RIDGE IS EXPECTED TO RETURN TO THE EAST ON MONDAY,  
SETTING UP OVER THE ATLANTIC COAST AND INDUCING RETURN FLOW BY  
TUESDAY. ANOTHER BAROCLINIC ZONE DEVELOPS ON THE UPSTREAM SIDE OF THE  
RIDGE, AND THE NEXT DEEP SHORTWAVE SPINS UP A SFC LOW OVER THE  
CENTRAL CONUS BY MIDWEEK. MODELS DIFFER ON HOW FAST THE RETURN FLOW  
REINTRODUCES PRECIP INTO OUR AREA AHEAD OF THAT SYSTEM, AND  
ACCORDINGLY ON THE TIMING OF THE SYSTEM ITSELF. CONFIDENCE IS LOW IN  
THE ADVERTISED POPS AND P-TYPES AHEAD OF IT. AGAIN THE GFS IS THE  
FASTEST MODEL OF THE SET, BUT AT ANY RATE THE PRIMARY EFFECTS OF THE  
SYSTEM ARE EXPECTED TO BE AFTER THE END OF THE FCST PERIOD, WEDNESDAY  
OR THURSDAY. TEMPS DO LOOK TO MODERATE BACK TO ABOUT NORMAL BY  
WEDNESDAY.  
 

 
   
AVIATION /00Z THURSDAY THROUGH MONDAY/
 
 
AT KCLT AND ELSEWHERE: VFR WITH MAINLY CIRRUS EXPECTED THROUGH  
THE EVENING HOURS FOR ALL BUT RIGHT ALONG THE TN BORDER.  
INCREASING MOISTURE AHEAD OF THE NEXT SYSTEM WILL BRING HIGH  
CLOUDINESS TO THE AREA AFTER MIDNIGHT. GUIDANCE HAS REALLY  
BACKED OFF WITH THE FCST OF RESTRICTIONS EARLY THURSDAY MORNING  
AND THE NEW TAFS REFLECT THAT TREND FOR THE TIME BEING. WILL  
MONITOR AND AMEND ACCORDINGLY LATER THIS EVENING IF IT LOOKS  
LIKE RESTRICTIONS WILL DEVELOP AT KAVL AND KAND TOWARD MORNING.  
GIVEN THE INCREASED UNCERTAINTY OF LOW CLOUDS, HAVE BACKED OFF  
TO JUST FEW MVFR-LEVEL CLOUDS AT KCLT. WIND WILL BE LIGHT NE  
OVERNIGHT BUT IS STILL FCST TO COME AROUND TO S DURING THE EARLY  
AFTERNOON. LIGHT PRECIP WILL MOVE IN FROM THE WEST IN THE  
MID/LATE AFTERNOON. ALL SITES BEGIN WITH A PROB30 IN THE  
AFTERNOON AND WILL RAMP UP FROM THERE. LATEST INDICATION IS THAT  
FLIGHT RESTRICTIONS WILL HOLD OFF UNTIL AFTER NIGHTFALL ON  
THURSDAY.  
 
OUTLOOK: UNSETTLED WEATHER WILL CONTINUE THURSDAY NIGHT, WITH  
BRIEF IMPROVEMENTS ON FRIDAY BEFORE YET ANOTHER SYSTEM PUSHES IN  
FOR THE WEEKEND WITH ASSOCIATED PRECIPITATION AND RESTRICTIONS.  
 
CONFIDENCE TABLE...  
 
00-06Z 06-12Z 12-18Z 18-00Z  
KCLT HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KGSP HIGH 100% HIGH 100% HIGH 100% HIGH 94%  
KAVL HIGH 100% HIGH 97% HIGH 98% MED 77%  
KHKY HIGH 100% HIGH 100% HIGH 100% HIGH 84%  
KGMU HIGH 100% HIGH 100% HIGH 100% HIGH 94%  
KAND HIGH 100% HIGH 100% HIGH 100% HIGH 97%  
 
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:  
 
WWW.WEATHER.GOV/GSP/AVIATION  
 

 
   
GSP WATCHES/WARNINGS/ADVISORIES
 
 
GA...NONE.  
NC...NONE.  
SC...NONE.  
 

 
 

 
SYNOPSIS...SBK  
NEAR TERM...PM/RWH  
SHORT TERM...MUNROE  
LONG TERM...WIMBERLEY  
AVIATION...PM  
 
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