Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KGSP 241759
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1259 PM EST WED DEC 24 2014

.SYNOPSIS...
A COLD FRONT WILL CROSS OUR AREA TODAY. HIGH PRESSURE WILL ARRIVE ON
THURSDAY AND LINGER INTO SATURDAY. A PAIR OF COLD FRONTS WILL
APPROACH THE AREA ON SUNDAY...CROSSING THE AREA MONDAY. GUSTY WINDS
WILL FOLLOW THE FRONT ON TUESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1230 PM...YET ANOTHER UPDATE TO ADJUST THE PRECIP CHANCES
ACROSS THE WESTERN CAROLINAS AND NE GEORGIA. THE EASTERN EDGE OF THE
STEADIER PRECIP WILL CONTINUE TO SHIFT EWD ACROSS METRO CLT THROUGH
EARLY AFTERNOON. THINK PRECIP CHANCES WILL GO DOWN CONSIDERABLY BY
19Z-20Z AND THE NEW GRIDS REFLECT THAT. CANNOT ENTIRELY REMOVE THE
PRECIP CHANCE ON ACCOUNT OF THE SFC FRONT REMAINING TO THE
WEST...AND THE POSSIBILITY OF THE WEDGE FRONT FINALLY MAKING INROADS
OVER THE S/SE FRINGE OF THE AREA. HIGH TEMPS WILL BE A PROBLEM FOR
THE AFTERNOON...AS THE WEDGE IS NOT REALLY ERODING AS MUCH AS IT IS
DRAINING AND MODIFYING. THE HEAVY RAIN THREAT AND SEVERE WEATHER
THREATS ARE DWINDLING...AND PROBABLY LIMITED TO ONLY THE ERN SIDE OF
METRO CLT AT THIS POINT.

AS OF 1130 AM...ANOTHER QUICK UPDATE TO ADJUST THE PRECIP CHANCES
FOR THE BACK END OF THE STEADIER PRECIP MAKING EWD PROGRESS ACROSS
THE WESTERN CAROLINAS AND NE GEORGIA. EXPECT PRECIP TO WIND DOWN
EARLIER THAN EXPECTED. STILL NO SIGNS OF THE WEDGE FRONT MAKING IT
INTO THE FCST AREA...THOUGH.

AS OF 1030 AM...RADAR TRENDS SHOW THE BULK OF THE HEAVIER
PRECIPITATION ALREADY SHIFTING E OF THE FCST AREA AS OF LATE
MORNING...AS THE WARM CONVEYER BELT SHIFTS OFF TO THE EAST. THAT
SHOULD SPELL THE END OF THE FLOOD THREAT ACROSS THE FCST AREA AS
RAINFALL RATES DROP. STILL HAVE WIDESPREAD RAIN ACROSS THE AREA E OF
THE MTNS...BUT PRECIP IS BEGINNING TO BREAK UP OVER THE WEST. THAT
NOTION HAS BEEN SUGGESTED BY THE GFS...THAT A DRY SLOT WILL END THE
PRECIP FROM THE WEST THROUGH EARLY AFTERNOON...AND THAT IDEA HAS A
LOT OF SUPPORT FROM THE SPC 4KM WRF. WILL TAPER THE PRECIP
PROBABILITY DOWN TO THE CHC RANGE FAIRLY QUICKLY THROUGH THAT TIME
AS THE BACK EDGE CROSSES THE AREA. STILL CANNOT TOTALLY RULE OUT
SEVERE THUNDERSTORMS...BUT WE ARE STEADILY LOSING THE POTENTIAL
OVERLAP OF BETTER SHEAR WITH WEAK CAPE. WEDGE DOES NOT YET SHOW ANY
SIGNS OF ERODING INTO THE FCST AREA...ALTHO THE COOL POOL CONTINUES
TO MODIFY AND DRAIN ON ITS OWN.

PREVIOUS DISCUSSION...

AS OF 645 AM EST...THE HIGHLY AMPLIFIED TROUGH AXIS REMAINS JUST
WEST OF THE MS RIVER VALLEY AROUND DAYBREAK THIS MORNING. THE LATEST
SFC ANALYSIS SHOWS THE CAD REGION OVERHEAD CONTINUING TO BECOME
SHALLOWER AND PINCHED...BUT STILL SOLIDLY COVERING OUR AREA WITH
TEMPS IN THE 40S TO LOWER 50S. THE APPROACHING SFC COLD FRONT
STRETCHED FROM NASHVILLE TO NEAR BIRMINGHAM...AND THIS BOUNDARY WILL
CONTINUE TO SLOWLY PUSH EAST THROUGH THE DAY. AFTER THE CURRENT
PRECIP RATE LULL...ANTICIPATE THAT HEAVIER RATES WILL FILL BACK IN
THROUGH THE LATE MORNING HOURS AS THE FRONT APPROACHES. THE UPSLOPE
AREAS HAVE RECEIVED 24 HOUR RAINFALL OF 2 TO 2.5 INCHES AND SHOULD
BE ABLE TO ABSORB THE APPROACHING 0.75 WITH THE MAIN FRONTAL PUSH.
WIDESPREAD FLOODING IS THUS NOT EXPECTED.

THE LATE DAY FROPA WILL ALLOW SOME CAD EROSION FROM THE SE THROUGH
THE DAY...WITH SLIGHT SFC BASED INSTABILITY LIKELY GETTING UNCOVERED
IN THE LOWER PIEDMONT BY 18Z. IT STILL APPEARS THAT THE BEST
SHEAR/INSTABILITY WILL NOT HAVE STRONG OVERLAP...BUT ANY PRE/FRONTAL
LINE SEGMENTS WILL NEED TO BE WATCHED VERY CAREFULLY THROUGH THE
DAY...ESPECIALLY IN THE ERN PIEDMONT THIS AFTN.

TEMPERATURE PROFILES WILL CRASH ACROSS THE HIGHER TERRAIN FROM THE
WEST AFTER 00Z POST FROPA. LOW LEVEL FLOW WILL HAVE A LESS THAN
FAVORABLE WESTERLY COMPONENT DURING THE UPSLOPE MOISTURE PERIOD
TONIGHT...WHICH WILL LIMIT SNOWFALL POTENTIAL IN THE COLD AIR.
HOWEVER...SOME MEASURE OF DEEP LAYER Q VECTOR CONVERGENCE WILL CROSS
THE MTNS WITH THE LIFTING TROUGH 06Z TO 12Z TONIGHT WHICH WILL GIVEN
WRN MTN POPS A SLIGHT BOOST. EXPECT A SUB ADVISORY EVENT FOR ANY
SNOWFALL ACCUMS AT THE HIGHER ELEVATIONS/TN BORDER AREA OVERNIGHT.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AT 230 AM EST WEDNESDAY...ON THURSDAY MORNING A WEAKENING UPPER
TROUGH WILL BE OVER THE EASTERN SEABOARD....WITH A WEAK RIDGE
UPSTREAM OVER THE EASTERN PLAINS...AND ANOTHER TROUGH OVER THE
ROCKIES. AN UPPER LOW CLOSES OFF AS IT DIVES INTO THE ROCKY MOUNTAIN
TROUGH ON FRIDAY...WHILE THE UPPER RIDGE DOWNSTREAM AMPLIFIES OVER
THE SOUTHERN APPALACHIANS AND GREAT LAKES.

AT THE SURFACE...THURSDAY MORNING WILL FEATURE MOIST WESTERLY FLOW
INTO THE NC MOUNTAINS BEHIND A DEPARTING COLD FRONT. WHILE THE
ORTHOGONAL COMPONENT INTO THE MOUNTAINS IS NOT IDEAL...SOME SNOW
SHOWERS MAY BE ONGOING IN THE MOUNTAINS BORDERING TN. AS A SURFACE
HIGH MOVES ACROSS THE GULF STATES DURING THE DAY...MOISTURE A COLD
ADVECTION DEPART...ENDING MOUNTAIN PRECIPITATION. THE DRY HIGH
PRESSURE WILL MOVE ACROSS GA AND THE CAROLINAS ON THURSDAY NIGHT AND
FRIDAY. LATE FRIDAY NIGHT...GULF MOISTURE WILL START TO REACH OUR
AREA IN SOUTHERLY FLOW BETWEEN THE ATLANTIC HIGH AND AND APPROACHING
COLD FRONT. TEMPERATURES WILL RUN A FEW DEGREES ABOVE NORMAL AS
HEIGHTS RISE ALOFT.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AT 230 AM EST WEDNESDAY...ON SATURDAY MORNING AND UPPER RIDGE AXIS
WILL BE OFF THE EAST COAST...WHILE AND UPPER TROUGH WILL EXTEND FROM
THE NORTHERN PLAINS TO THE SOUTHERN ROCKIES. BY SUNDAY MORNING THE
RIDGE MOVES FARTHER OFF THE EAST COAST...AND THE TROUGH MOVES INTO
THE PLAINS. THE PATTERN PROGRESSES VERY LITTLE INTO MONDAY...BUT BY
TUESDAY THE TROUGH AXIS ENTERS THE MS RIVER VALLEY.

SATURDAY MORNING STARTS OUT WITH SURFACE HIGH PRESSURE CENTERED NEAR
THE NC OUTER BANKS. THIS HIGH EXTENDS ACROSS THE WESTERN CAROLINAS
AND N GA...WHILE A COLD FRONT ENTERS THE MID AND LOWER MS RIVER
VALLEY...PRECEDED BY MOIST GULF INFLOW. THIS GULF INFLOW STARTS TO
WEAKENS ON SUNDAY AS THE FRONT SLOWLY CROSSES THE GULF STATE...AND
BECOMES QUITE LIMITED AS THE FRONT CROSSES GA AND THE CAROLINAS
SUNDAY NIGHT AND EARLY MONDAY. A SECONDARY FRONT CROSSES THE AREA
FROM THE NW LATE ON MONDAY...WITH COLD MOIST UPSLOPE FLOW IN ITS
WAKE SUPPORTING SNOW IN THE NC MOUNTAINS BORDERING TN INTO TUESDAY.
TEMPERATURES WILL RUN ABOVE NORMAL AHEAD OF THE PAIR OF FRONTS...AND
BELOW NORMAL BEHIND THEM.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AT KCLT...THE BETTER PART OF THE REST OF THE DAY SHOULD BE PLAGUED
BY IFR/LIFR RESTRICTIONS. THE STEADIER PRECIP SHOULD MOVE EAST OF
THE AIRFIELD BY 19Z-20Z...AND THEREAFTER MORE SPOTTY SHOWER ACTIVITY
WILL CONTINUE IN ADVANCE OF THE FRONT. A TEMPO GROUP WAS INCLUDED TO
HANDLE THAT. THERE COULD BE A FEW MVFR/VFR HOLES THAT OPEN BRIEFLY
AFTER STRONGER SHOWERS MOVE THROUGH...BUT THE STRATUS SHOULD FILL
RIGHT BACK IN. THE PROBLEM IS THE WEDGE SHOWS LITTLE SIGN OF ERODING
FROM THE SE AS WIDESPREAD PRECIP CONTINUES TO STREAM N/NE IN THE
WARM CONVEYOR BELT OVER THE MIDLANDS AND SANDHILLS. WEAK FLOW OVER
THE DRAINING WEDGE WILL HELP TO MAINTAIN THE LOW STRATUS WELL INTO
THE EVENING HOURS...AND IN ALL LIKELIHOOD...TO AT LEAST 03Z. THE
CONDITIONAL CLIMATOLOGY CONTAINS A RELATIVELY ROBUST NUMBER OF OBS
WHICH INDICATE LIFR PAST 05Z. VEERING FLOW BEHIND THE FRONT THAT
WILL PASS DURING LATE EVENING SHOULD SPELL DOOM FOR THE WEDGE
REMNANTS...AND THE CEILING SHOULD IMPROVE TO MVFR AND THEN VFR
DURING THE EARLY MORNING HOURS. THIS WAS INDICATED AT 06Z BUT COULD
HAPPEN CLOSER TO 09Z. THE LOW CLOUDS SHOULD SCATTER OUT BY 13Z OR
SO...BUT THIS COULD NOT BE INCLUDED IN THE NEW TAF BECAUSE OF SPACE
LIMITATIONS.

ELSEWHERE...OUTSIDE THE MTNS...SIMILAR TO KCLT BUT WITH EARLIER
TIMING FOR THE END OF PRECIP AND SCATTERING OF LOW STRATUS CEILING.
HAVE INCLUDED A PERIOD OF A FEW HOURS TO START THE TAFS WHEN SHOWER
ACTIVITY COULD STILL MOVE THROUGH...OTHERWISE...JUST LOW STRATUS
WITH SOME FOG REDEVELOPMENT. AT KAVL...CEILING SHOULD IMPROVE
EARLIER...IN EARLY EVENING...AS NW FLOW DEVELOPS.

OUTLOOK...DRY HIGH PRESSURE WILL BUILD BACK INTO THE REGION THURSDAY
NIGHT AND FRIDAY WITH VFR CONDITIONS. ANOTHER COLD FRONT WILL ARRIVE
FROM THE NW SATURDAY NIGHT AND MAY STALL OVER THE MTNS. THAT MAY
ALLOW RESTRICTIONS TO DEVELOP BY SUNDAY MORNING...PERHAPS CONTINUING
THROUGH THE MIDDLE OF NEXT WEEK.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH  81%     MED   70%     HIGH 100%     HIGH 100%
KGSP       MED   79%     HIGH  84%     HIGH 100%     HIGH 100%
KAVL       HIGH  89%     MED   69%     HIGH 100%     MED   76%
KHKY       HIGH  84%     MED   70%     HIGH 100%     HIGH 100%
KGMU       MED   77%     HIGH  85%     HIGH 100%     HIGH 100%
KAND       MED   73%     HIGH  85%     HIGH 100%     HIGH 100%

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...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JAT
NEAR TERM...HG/PM
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...PM


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.