693
FXUS62 KGSP 090610
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
110 AM EST FRI JAN 9 2026
SYNOPSIS
TEMPERATURES REMAIN UNSEASONABLY WARM THROUGH SATURDAY. RAIN
CHANCES ALSO INCREASE THROUGH SATURDAY UNTIL A COLD FRONT PUSHES
THROUGH THE AREA. TEMPERATURES RETURN TO NEAR-NORMAL SUNDAY INTO
EARLY NEXT WEEK UNDER BUILDING HIGH PRESSURE.
NEAR TERM /THROUGH TONIGHT/
AS OF 1:15 AM FRIDAY:
KEY MESSAGE 1: SOME POTENTIAL FOR AREAS OF DENSE FOG THIS MORNING
EAST OF THE MOUNTAINS.
AT THIS EARLY HOUR, SATELLITE IMAGERY SHOWS THE RETURN OF LOW LEVEL
MOISTURE MOVING UP FROM THE SOUTH AND SOUTHWEST AS AN INITIAL
PULSE OF ISENTROPIC UPGLIDE SPREADS ACROSS THE REGION. WE'RE IN
THE PROCESS OF CLOUDING UP AND GUIDANCE SUGGESTS A WIDESPREAD
LOW STRATUS BY DAYBREAK, BUT ALSO A LARGE AREA OF FOG EAST OF THE
MTNS. NOT THE BEST SITUATION FOR ADVECTION FOG AND CERTAINLY NOT
A RADIATION FOG, SO THERE'S SOME UNCERTAINTY ABOUT HOW THE FOG
WILL PLAY OUT. IT COULD BE A SITUATION WHERE VIS GETS LOW BUT NOT
QUITE LOW ENOUGH FOR A DENSE FOG ADVISORY. WE SHALL MONITOR. THE
FOG POTENTIAL WILL END BY MIDDAY AS BETTER MIXING ELIMINATES IT.
KEY MESSAGE 2: PRECIP CHANCES INCREASE TODAY WITH THE ARRIVAL OF
DEEP MOISTURE AND FORCING.
A SHORT WAVE LIFTING OUT OF THE MID/UPPER TROF OVER THE PLAINS
TODAY WILL CARRY LOW PRESSURE OVER THE GREAT LAKES AND INTO
EASTERN CANADA, WHICH IN TURN WILL DRAG A COLD FRONT ACROSS THE
TN VALLEY REGION THIS AFTERNOON. MID/UPPER FORCING WILL IMPROVE
QUICKLY DURING THE LATE MORNING/EARLY AFTERNOON AHEAD OF THE
BOUNDARY AND SHOULD SPREAD EASTWARD ACROSS OUR REGION THROUGH THE
AFTERNOON AND EVENING. ISENTROPIC LIFT AT LOW AND MID-LEVELS ALSO
IMPROVES ACROSS THE AREA ALONG AND N/W OF I-85 THIS AFTERNOON
WHILE DEEP LAYER MOISTURE MOVES IN FROM THE WEST. SO, IN SPITE
OF THE MEAGER PRECIP ALONG THE BOUNDARY EARLY THIS MORNING,
THE INCREASE IN FORCING SHOULD HELP PRECIP TO BLOSSOM AHEAD OF
THE FRONT ACROSS THE MTNS/FOOTHILLS AT LEAST. PRECIP CHANCES
IMPROVE FROM THE WEST AS A RESULT, BUT THIS WAS ALREADY HANDLED
FAIRLY WELL IN THE ONGOING FORECAST, SO ONLY MINOR CHANGES WERE
MADE. THERE COULD BE A FEW RUMBLES OF THUNDER BECAUSE OF SOME WEAK
ELEVATED INSTABILITY. THE SITUATION CONTINUES TO IMPROVE TONIGHT
AS THE BOUNDARY LAYS OUT ACROSS THE REGION, SO A HIGH PRECIP PROB
STILL LOOKS WARRANTED. THE QPF LOOKS MANAGEABLE AT THIS TIME,
ESPECIALLY CONSIDERING HOW IT HAS BEEN RELATIVELY DRY LATELY. IF
THERE WOULD BE AN OUTSIDE CHANCE OF A PROBLEM, IT WOULD BE IN THE
SOUTHWEST-FACING SLOPES IN THE LITTLE TN BASIN IN SOUTHWEST NC.
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/
AS OF MIDNIGHT FRIDAY MORNING:
KEY MESSAGE 1: HEAVY RAIN MAY CONTINUE SATURDAY MORNING IN THE
SOUTHWESTERN FORECAST AREA.
ALTHOUGH THE BEST FRONTOGENETIC FORCING STILL IS LIKELY TO OCCUR OVER
THE MOUNTAINS AND UPPER SAVANNAH RIVER VALLEY PRIOR TO 12Z SATURDAY,
850MB WINDS WILL REMAIN IN A FAVORABLE SW'LY DIRECTION THROUGH THE
MORNING AND MAY ACTUALLY INCREASE IN SPEED BETWEEN DAYBREAK AND NOON,
CONTINUING TO PROVIDE UPSLOPE FORCING INTO THE SOUTHWEST FACING
MOUNTAIN RIDGES AND TO SOME DEGREE THE ESCARPMENT. 900MB
FRONTOGENESIS (BASICALLY VERY NEAR SURFACE FOR THE HIGHER MOUNTAINS)
IS SHOWN TO INCREASE ON THE NAM AND GFS AFTER 12Z, SO THE POTENTIAL
FOR HEAVY RAINFALL WILL PERSIST, WITH STEERING FLOW ORIENTED ROUGHLY
PARALLEL TO THAT AXIS. PWATS STILL WILL BE NEAR THEIR PEAK VALUE (+3
SD PER ENSEMBLE MEAN) OVER THE AREA. HENCE ANY BANDS OF HEAVY RAIN
ONGOING AT DAYBREAK WILL TAKE TIME TO DIMINISH, AND NEW BANDS COULD
DEVELOP. OF NOTE, THE HIGHER RES DETERMINISTIC MODELS ARE NOT SHOWING
MUCH POTENTIAL FOR RATES GREATER THAN AN INCH PER HOUR; THE MAIN
CONCERN IS FOR A LONGER DURATION RAIN EVENT WITH TOTALS SLOWLY
BUILDING AND CAUSING RISES ON CREEKS AND STREAMS, AND THAT APPEARS
MOST LIKELY IN OUR FAR SW NC COUNTIES AND THE ADJACENT PORTION OF
GA/SC. IN LIGHT OF RECENT DRY WEATHER BEING A BIG MITIGATING FACTOR
FOR FLOOD RISK, THE WPC MARGINAL RISK LOOKS APPROPRIATE FOR THE
WESTERN CWA AND EMBEDDED SLIGHT FOR THE MOUNTAINS NEAR AND SOUTHWEST
OF THE GREAT SMOKIES. NOT CONFIDENT ENOUGH FOR A FLOOD WATCH AT THIS
TIME.
KEY MESSAGE 2: CONVECTION SATURDAY AFTERNOON COULD POSE
AN ISOLATED RISK OF DAMAGING WINDS.
SURFACE COLD FRONT LOOKS UNLIKELY TO CROSS THE MOUNTAINS UNTIL
SATURDAY EVENING, BUT DEEP SATURATION CONTINUES TO BE SHOWN OVER THE
AREA THROUGH THE DAY, SO LAPSE RATES REMAIN POOR, ALTHOUGH STRONG
SOUTHWESTERLY WAA IS EXPECTED TO BRING TEMPS TO THE UPPER 60S OVER
MOST LOWER ELEVATIONS NORTHWEST OF I-85, AND LOWER 70S SOUTHEAST.
DEWPOINTS ALREADY WILL BE IN THE UPPER 50S IN THE MORNING AND SHOULD
PUSH PAST 60 BY MIDDAY. SBCAPE REMAINS SMALL, NO BETTER THAN 200-300
J/KG, IN MOST GUIDANCE SOLUTIONS, THOUGH THE PROBABILITY OF NONZERO
SBCAPE HAS INCREASED IN RECENT CYCLES OF SEVERAL MODELS. SCREAMING
40-50 KT WINDS AT 850 MB WILL OFFER SUFFICIENT 0-3KM BULK SHEAR TO
ANTICIPATE A SMALL THREAT OF DAMAGING WINDS WITH LOW-TOPPED
CONVECTIVE STORMS, EVEN IF NO THUNDER RESULTS (THOUGH THUNDER CHANCES
HAVE INCREASED WITH THE MEAN SBCAPE). THE ORIENTATION OF THE SHEAR
VECTORS IS LESS THAN IDEAL W.R.T. THE EXPECTED ORIENTATION OF THE
FRONT, AND THE CAMS THAT GO OUT THRU SATURDAY ARE NOT PRODUCING MUCH
IN THE WAY OF UPDRAFT HELICITY. WE ALSO LACK THE STRONG 500MB TROUGH
THAT IS KNOWN TO BE AN IMPORTANT FACTOR IN HIGH-SHEAR LOW-CAPE
TORNADO THREAT. NEVERTHELESS, SPC HAS A MARGINAL RISK AREA
ENCOMPASSING THE CWA SATURDAY, AND THAT LOOKS REASONABLE. EVEN IF
CONVECTION DOES NOT PRODUCE A SPIN-UP, HAVE INCLUDED FORECAST WIND
GUSTS ABOVE NBM ON THE ASSUMPTION THAT RAIN OR CONVECTIVE DOWNDRAFTS
COULD BRING DOWN STRONG WINDS OF 30-40 MPH.
KEY MESSAGE 3: COLD FRONT WILL BRING WINDY CONDITIONS SATURDAY NIGHT
AND SUNDAY, WHICH COULD OVERLAP WITH LOW RELATIVE HUMIDITY SUNDAY
AFTERNOON.
CAA WILL SET IN SATURDAY NIGHT WITH LEADING VORT AXIS BLOWING THRU
THE AREA, AND SFC GRADIENT BEGINS TO INCREASE ACROSS THE MOUNTAINS,
AND HIGH ELEVATIONS WILL SEE GUSTS PICK UP ACCORDINGLY, POTENTIALLY
REACHING ADVISORY CRITERIA BY DAYBREAK SUNDAY. ENOUGH MOISTURE COULD
LINGER ALONG THE TN BORDER FOR FLURRIES WITH VERY LIGHT SNOW ACCUMS
NOT OUT OF THE QUESTION IN HIGH ELEVATIONS THRU MIDDAY. THE MAIN
SHORTWAVE PASSES DURING THE DAY SUNDAY, WHICH USHERS IN A SECONDARY
FRONT AND VEERS WINDS SOLIDLY NW. TEMPS IN THE HIGHER MOUNTAINS
SHOULD REMAIN NEARLY STEADY THROUGH THE DAY OR FALL SLIGHTLY, WHILE
AREAS EAST OF THE MOUNTAINS WILL SEE A NORMAL DIURNAL CURVE, WITH
COLDER AIR OFFSET BY DOWNSLOPING. DEWPOINTS WILL TANK FOLLOWING THE
TROUGH AXIS, AND GUSTS TO NEARLY 30 MPH ARE LIKELY AT TIMES IN THE
PIEDMONT. THERE COULD BE A BRIEF PERIOD OF OVERLAP BETWEEN THE WIND
AND LOW RH, THOUGH BOTH CONDITIONS BECOME LESS CONCERNING FOR FIRE WX
QUICKLY WITH SUNSET IN THE PIEDMONT, THOUGH IT WOULDN'T TAKE MUCH TO
WORSEN CONDITIONS DURING THE AFTERNOON. WE'LL BE COMING OUT OF THE
RAINY PERIOD, SO FUEL MOISTURE MAY NOT BE QUITE LOW ENOUGH TO WARRANT
ANY FIRE WEATHER HEADLINES AS IT IS, BUT THAT IS SOMETHING THAT WILL
NEED TO BE MONITORED SUNDAY.
LONG TERM /MONDAY THROUGH THURSDAY/
AS OF 1250 AM FRI:
KEY MESSAGE: DRY AND SEASONABLY COLD MONDAY AND TUESDAY. PASSING
TROUGH BRINGS BACK CHANCES FOR PRECIP WEDNESDAY AND THURSDAY.
MOSTLY CLEAR WITH WINDS BECOMING LIGHT MONDAY AS SFC HIGH CENTERS
OVER THE GULF/ATLANTIC COASTAL PLAIN. MAX TEMPS END UP ABOUT A
CATEGORY BELOW NORMAL FOR THE FIRST TIME IN A WHILE. RH LIKELY TO
BOTTOM OUT AT OR BELOW 30 PERCENT IN MUCH OF THE AREA THAT AFTERNOON,
THOUGH WITH THE LIGHT WINDS FIRE WX CONCERN MAY BE MITIGATED. SW FLOW
DEVELOPS TUESDAY; TEMPS AND DEWPOINTS REBOUND ALTHOUGH LOW RH AGAIN
MAY OCCUR. HEIGHT FALLS ARE REINFORCED ALOFT AS CLIPPER-LIKE TROUGH
DIGS INTO THE UPPER MIDWEST CIRCA TUESDAY. MODELS CONTINUE TO SHOW
THIS TROUGH DEEPENING NEAR THE GREAT LAKES AND BRINGING ANOTHER COLD
FRONT TO THE SOUTHERN APPALACHIANS WED OR THU. MOST MODELS STILL
SHOW THE TROUGH ACTIVATING THE COASTAL FRONT, AND WHILE THE
DETERMINISTIC GFS/EC/GDPS NOW DEPICT THE INCIPIENT LOW DISTANT ENOUGH
FROM OUR AREA TO PRECLUDE PRECIP IN OUR PORTION OF THE PIEDMONT, A
FEW ENSEMBLE MEMBERS FROM EACH MODEL STILL DO, AND SO NBM REFLECTS
SMALL POPS THERE. TEMPERATURES WOULD BE WARM ENOUGH FOR ONLY RAIN
OUTSIDE THE MOUNTAINS, WHERE SNOW WOULD BE PREDOMINANT WHERE TEMPS
ARE COLD ENOUGH. LIGHT MOUNTAIN ACCUMS APPEAR POSSIBLE.
AVIATION /06Z FRIDAY THROUGH TUESDAY/
AT KCLT AND ELSEWHERE: A SOUTHERLY FLOW OF MOISTURE RETURNING
FROM THE GULF WAS ALREADY WORKING ITS MAGIC AT THIS LATE HOUR
WITH A GRADUALLY DEVELOPING/EXPANDING AREA OF MVFR CEILING
RESTRICTIONS. GUIDANCE IS ESPECIALLY PESSIMISTIC WITH THE
CEILING DROPPING DOWN THROUGH MVFR AND IFR TO LIFR BY DAYBREAK,
BUT IT COULD JUST AS EASILY BE THE VIS THAT BECOMES THE MAIN
RESTRICTION. WARM ADVECTION, THE ARRIVAL OF PRE-FRONTAL SHOWER
ACTIVITY, AND SOUTHWESTERLY FLOW WILL EVENTUALLY BE ABLE TO OVERCOME
THE LIFR/IFR RESTRICTIONS BECAUSE THERE SHOULDN'T BE ANY OF THE
USUAL COLD AIR DAMMING, SO THE FOG WILL MIX OUT AND THE CEILING
SHOULD LIFT STEADILY BACK TO MVFR WITH HOLES IN THE AFTERNOON. THE
SITUATION DOESN'T CHANGE THOUGH, AND THE RESTRICTIONS WILL RETURN
AFTER SUNSET, IF THEY EVER GO AWAY THAT IS. WIND DIRECTION IS
EXPECTED TO SHIFT FROM SE TO SW TODAY AND THEN BACK AGAIN TONIGHT.
OUTLOOK: FLIGHT RESTRICTIONS LIKELY INTO THE WEEKEND AS THE COLD
FRONT MOVES INTO THE AREA. CONDITIONS IMPROVE LATE SATURDAY INTO
SUNDAY BEHIND THE FRONT.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...JCW
NEAR TERM...PM
SHORT TERM...JCW
LONG TERM...JCW
AVIATION...PM
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