Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 010248
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
948 PM EST SAT JAN 31 2015

.SYNOPSIS...
DRY HIGH PRESSURE WILL PERSIST OVER THE REGION THROUGH SUNDAY
MORNING. MOISTURE WILL RETURN SUNDAY AFTERNOON AND SUNDAY NIGHT
AHEAD OF A LOW PRESSURE SYSTEM AND ASSOCIATED COLD FRONT. THE COLD
FRONT WILL CROSS THE REGION EARLY MONDAY WITH DRY HIGH PRESSURE
RETURNING TUESDAY. ANOTHER COLD FRONT WILL CROSS THE REGION LATE
WEDNESDAY INTO EARLY THURSDAY.

&&

.NEAR TERM /THROUGH SUNDAY/...
AS OF 930 PM...STEADY INCREASE IN MID CLOUD SEEN ON SAT AND IN THE
METARS ACRS THE TN VLY TO THE CAROLINAS. SFC HIGH PRES CONTINUES TO
SHIFT EAST...WHILE A LOW PRES SYSTEM ORGANIZES OVER THE PLAINS. I
UPDATED THE SKY/TEMP/DWPTS WITH LATEST SAT/METARS. NO SIGNIFICANT
CHANGES FOR THE OVERNIGHT. THE COMBINATION OF A SLGT INCREASE IN THE
PRES GRAD AND THICKENING MID CLOUDS MAY KEEP MIN TEMPS UP A BIT
ABOVE THE MOS CONSENSUS. SO I HAVE BUMPED UP THE MIN TEMP ABOUT A
CATEGORY FOR MOST PLACES.

PORTION OF PREVIOUS DISCUSSION...
UPPER LVL DIFFLUENCE IN MOIST SWLY FLOW WILL SET UP OVER THE
FORECAST AREA ON SUNDAY AS A POTENT UPPER LEVEL TROUGH MOVES
EASTWARD INTO THE MID/UPPER MISSISSIPPI VALLEY BY SUN AFTERNOON.
THIS WILL PUSH A DEEPENING SURFACE LOW INTO IN/KY...WITH ITS
ASSOCIATED SURFACE COLD FRONT REACHING THE MISSISSIPPI VALLEY BY 00Z
MON. AHEAD OF THIS FEATURE...A STRONG 45-55KTS OF 850MB LOW LEVEL
SOUTHERLY JET WILL DEVELOP BY LATE SUN AFTERNOON/EVENING. THIS
SHOULD LEAD TO GUSTY SSW WINDS OF +45MPH ACROSS HIGHER RIDGE TOPS
OF THE NC MTNS. THEREFORE...WILL ISSUE A WIND ADVISORY ACROSS THE SW
AND CENTRAL NC MTNS ABOVE 3500FT BETWEEN 22Z SUN AND 10Z MON. AS FOR
THE PRECIP...LATEST MODEL VERTICAL PROFILE OVER THE WESTERN ZONE
INDICATES THAT LLVL LAYER BELOW 600MB WILL REMAIN DRY UNTIL 18Z SUN.
HENCE...HAVE KEPT THE FORECAST DRY ACROSS ENTIRE CWA THRU SUN
MORNING. HOWEVER....POPS QUICKLY RAMP UP FROM WEST TO EAST 18Z INTO
00Z MON AS UPPER DIVERGENCE INCREASES AND DEEP LAYER MOISTURE
ARRIVES THE AREA AHEAD OF THE APPROACHING COLD FRONT. NO WINTRY
PRECIP IS EXPECTED GIVEN WARMER THERMAL PROFILE. TEMPS ON SUNDAY
WILL RUN NEAR...OR A FEW DEGREES BELOW NORMAL.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AS OF 245 AM SATURDAY...12Z GFS INDICATES THAT A SHARP H5 TROUGH
WILL RIPPLE EAST OF THE MISSISSIPPI RIVER VALLEY SUNDAY NIGHT. H5 Q
VECTOR CONVERGENCE INCREASES ACROSS THE SOUTHERN APPALACHIAN AREA
LATE SUNDAY NIGHT...PEAKING DURING EARLY DAYLIGHT HOURS MONDAY. AT
THE SFC...MODELS HAVE TRENDED A LITTLE NORTH WITH THE TRACK OF THE
LOW CENTER...PASSING MORE ACROSS PA/LI MONDAY MORNING. THE TIMING OF
THE STRONG COLD FRONT ACROSS THE REGION IS SLIGHTLY FASTER THAN
PREVIOUS RUNS...BUT NOT SIGNIFICANTLY SO. H85 WINDS AHEAD OF THE
FRONT MAY REACH 50 KTS ACROSS THE SOUTHERN AND CENTRAL MTNS...PLAN
TO HIGHLIGHT WITH A HIGH ELEVATION WIND ADVISORY UNTIL 10Z.
HOWEVER...CAA WILL BE RAPID MON AM...H85 OVER KAVL WILL FALL FROM 6C
AT 9Z TO -10C BY 21Z. THE TEMPERATURE FORECAST WILL BE
CHALLENGING...LIKELY FEATURING WIDESPREAD COOLING TEMPERATURES
THROUGH THE AFTERNOON. NATURALLY...THE TIMING OF THE CAA WILL BE
PIVOTAL TO THE SNOW FORECAST. BASICALLY...PRECIP IS EXPECTED TO FALL
AS RAIN SUNDAY NIGHT...BEGINNING TO MIX WITH SNOW ACROSS THE RIDGES
1 TO 2 HOURS BEFORE SUNRISE MON. MTN PRECIP WILL TRANSITION TO
COMPLETELY SNOW BY MID MORNING MONDAY. APPLYING WPC SNOW RATIO
GUIDANCE TO PRECIP TIMING...NWF AREAS SHOULD RECEIVE 1-2 INCHES MON.
IN ADDITION...NW WINDS SHOULD INCREASE THROUGH MID DAY AS THE
PRESSURE GRADIENT TIGHTENS BETWEEN THE FRONT AND APPROACHING HIGH
PRESSURE...WE WILL CONTINUE TO MENTION IN THE HWO.

TUESDAY...THE CENTER OF A SOUTHERN PLAIN HIGH WILL BUILD ACROSS THE
WESTERN CAROLINAS AND NE GA. CONDITIONS WILL FEATURE A LIGHT
DOWNSLOPE WIND AND CLEAR TO MOSTLY CLEAR SKY. COOL THICKNESSES WILL
RESULT IN BELOW NORMAL TEMPERATURES...GENERALLY 7-10 DEGREES BELOW
NORMS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 245 PM SATURDAY...MODELS STILL AT ODDS OVER THE STORM SYSTEM
CENTERED ON THURSDAY. THE GFS SHOWS THE SRN STREAM UPPER LOW
STARTING OVER MEXICO OPENING UP AN MOVING EAST ALONG THE GULF COAST
AND PHASING WITH A NRN STREAM SHORT WAVE DIVING INTO THE LOWER MS
VALLEY WED AND THU. THIS WAVE THEN SLIDES ACROSS THE SE ON FRI WITH
NWLY FLOW SETTING UP ON SAT. THE ECMWF KEEPS THE OPENING UPPER LOW
SUPPRESSED AND DAMPENED AS IT MOVES ACROSS THE GULF OF MEXICO. THE
NRN STREAM SHORT WAVE DOES NOT PHASE AND REMAINS WEAKER AS IT MOVES
ACROSS THE AREA THU AND THU NITE...WITH NWLY FLOW DEVELOPING FRI AND
ZONAL FLOW SAT.

AT THE SFC....THE GFS MAINTAINS ITS WETTER FORECAST EVEN AS THE
ASSOCIATED MILLER-A LOW HAS BEEN SUPPRESSED FARTHER SOUTH INTO THE
GULF OF MEXICO. A COLD FRONT MOVES SOUTH OF THE AREA THU AS A CAD
SETS UP AND A COMBINATION OF UPPER JET FORCING AND ISENTROPIC LIFT
OVER THE CAD...SPREADS PRECIP INTO THE AREA WED NITE AND THU...
WHICH THEN DIMINISHES THU NITE. THE ECMWF MAINTAINS ITS GENERALLY
DRY FCST WITH THE EVEN FURTHER SUPPRESSED MILLER-A LOW AND A DRIER
FRONT AND CAD. THERE IS SOME NW FLOW PRECIP ACROSS THE MTNS WED NITE
WITH THE FRONT AND THU NITE WITH A SHORT WAVE. THE GEFS ENSEMBLE
MEAN SHOWS SLIGHT TO LOW CHC POP DURING THIS TIME FRAME...SO HAVE
TRENDED TOWARD THAT SCENARIO GIVEN THE CONTINUED UNCERTAINTY AND LOW
CONFIDENCE. GIVEN THE COLD TEMPS ASSOCIATED WITH THIS SYSTEM...
PRECIP WOULD BE SNOW OR A RAIN/SNOW MIX ACROSS THE MTNS WITH MAINLY
RAIN ELSEWHERE...AT LEAST THRU MOST OF THE PRECIP PERIOD. IT COULD
END AS SOME VERY LIGHT SNOW OUTSIDE OF THE MTNS HOWEVER. TEMPS NEAR
TO A LITTLE ABOVE NORMAL WED...FALL BELOW NORMAL THU AND FRI...THEN
BACK TO NEAR NORMAL SAT.

&&

.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
AT KCLT...A LOW PRES SYSTEM WILL CONTINUE ORGANIZE OVER THE MIDWEST
TONIGHT THRU SUNDAY. A GRADUAL INCREASE IN MOISTURE AND LLVL SWLY
FLOW IS EXPECTED AHEAD OF THE SYSTEM. SO EXPECT GRADUAL INCREASE IN
CLOUDS...WITH PLENTY OF MID LVL CIGS THRU MIDDAY SUNDAY. THEN
GUIDANCE AGREES THAT A LOW VFR DECK WILL DEVELOP...WITH MVFR CIGS
JUST TO THE SOUTHWEST TO END THE 00Z TAF PERIOD. WINDS WILL FAVOR SW
AND SHUD REMAIN LIGHT THRU SUNDAY MORNING. THEN A SLIGHT INCREASE TO
6-10KT DURING THE AFTN HOURS. COULD SEE A FEW LOW-END GUSTS OF 15-16
KTS...BUT NOT FREQUENT.

ELSEWHERE...AS WITH KCLT ABOVE...INCREASING MOISTURE AND SWLY FLOW
AHEAD OF A STORM SYSTEM TO THE WEST. LOWER CIGS SHUD ARRIVE A LITTLE
EARLIER ACRS THE UPSTATE AND AT KAVL...WITH MVFR CIGS EXPECTED BY
MID AFTN. KHKY IS EXPECTED TO STAY VFR UNTIL ABOUT THE END OF THE
00Z TAF PERIOD. A RAIN SHIELD IS EXPECTED TO DEVELOP TO OUR WEST
DURING THE DAY...ENTERING THE NC MTNS AND WRN UPSTATE BY EARLY
EVENING. SW WINDS EXPECTED THRU THE PERIOD. COULD SEE SOME LOW-END
GUSTS (IN THE 15-19 KT RANGE ) ACRS THE UPSTATE AND AT KAVL...WITH
ENUF FREQUENCY TO ADD MENTION AT KAVL.

OUTLOOK...RAIN AND LOWER CIGS/VSBY EXPECTED SUNDAY NIGHT THRU MIDDAY
MONDAY. DRYING NW FLOW IS EXPECTED ON THE BACK-SIDE OF THE SYSTEM BY
LATE MONDAY...BUT WILL BE ACCOMPANIED BY GUSTY WINDS...ESP AT KAVL.
ANOTHER MOIST LOW PRES SYSTEM MAY AFFECT THE REGION LATE NEXT WEEK.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  82%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  97%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  92%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  83%
KAND       HIGH 100%     HIGH 100%     HIGH  94%     HIGH  92%

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...WIND ADVISORY FROM 5 PM SUNDAY TO 5 AM EST MONDAY FOR NCZ048-
     051-052-058-059-062>064.
SC...NONE.

&&

$$
SYNOPSIS...JPT
NEAR TERM...ARK/JOH
SHORT TERM...NED
LONG TERM...RWH
AVIATION...ARK



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