Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 231459
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
959 AM EST FRI JAN 23 2015

.SYNOPSIS...
LOW PRESSURE WILL TRACK ALONG THE GULF COAST EARLY TODAY...BEFORE
MOVING UP THE EAST COAST OVER THE WEEKEND. HIGH PRESSURE WILL
BRIEFLY BUILD IN ON SUNDAY...BEFORE A LOW PRESSURE SYSTEM AFFECTS
THE FORECAST AREA SUNDAY NIGHT AND MONDAY. HIGH PRESSURE BUILDS OVER
THE AREA FROM MID TO LATE NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 950 AM...RADAR SHOWS WIDESPREAD PRECIP ACROSS THE AREA WITH
MANY REPORTS OF SLEET MIXED WITH RAIN OUTSIDE OF THE MTNS AS THE
ATMOS COOLED TO WET BULB TEMPS WITH INCREASING MOISTURE. THIS MIX
WILL BE SHORT LIVED AS STRONG WARMING OCCURS IN THE DEVELOPING
STRONG WAA FLOW. ACROSS THE MTNS...THE WINTRY MIX CONTINUES ACROSS
THE NRN MTNS AND BLUE RIDGE...AND MUCH OF THE HIGH ELEVATIONS SOUTH
TO THE BALSAMS. HOWEVER...SFC WET BULBS ARE WARMING QUITE A BIT WEST
OF THE FRENCH BROAD VALLEY. EXPECT THE SMOKIES AND BALSAMS WILL
REMAIN BELOW FREEZING FOR A LITTLE LONGER BEFORE THE WARMING KICKS
IN. WILL REMOVE MACON...SRN JACKSON AND TRANSYLVANIA FROM THE ADV AS
NO SIGNIFICANT WITNRY PRECIP SHOULD FALL THERE. WILL LEAVE IN FOR
THE SMOKIES AND BALSAMS EVEN THO THERE WILL LIKELY BE A BREAK IN THE
WINTRY MIX THIS AFTERNOON AS SNOW IS EXPECTED TO REDEVELOP
OVERNIGHT. MAY BE ABLE TO REMOVE BUNCOMBE THIS AFTERNOON WHEN WARMING
OCCURS OVER THE NORMALLY COLDER EASTERN SECTIONS. WINTRY MIX SHUD
LINGER THRU THE AFTERNOON ACROSS THE HIGHER ELEVATIONS OF THE NRN
MTNS AND NRN FOOTHILLS. OTHERWISE...LITTLE CHANGE IN GOING FCST.

AS OF 640 AM...MAINLY LIGHT PRECIP CONTINUES TO OVERSPREAD THE
FORECAST AREA THIS MORNING. BASED ON THE LATEST OBSERVATIONAL
TRENDS...IT APPEARS THAT ANY WINTRY PRECIP SHOULD BE CONFINED TO
AREAS ALONG AND NORTH OF THE I-40 CORRIDOR...AND AREAS ABOVE ABOUT
3000 FEET SOUTH OF THIS CORRIDOR. WITH TEMPS EXPECTED TO STAY ABOVE
FREEZING IN ALL BUT THE HIGH ELEVATIONS...AND ALONG THE IMMEDIATE
EASTERN BLUE RIDGE ESCARPMENT...LITTLE IF ANY ACCUMS ARE EXPECTED IN
THESE AREAS. EVEN IF SOME AREAS DO SEE A LITTLE ACCUMULATION...
TRAVEL SHOULD NOT BE AN ISSUE...EXCEPT PERHAPS ON ROADS LEADING INTO
THE MTNS FROM THE NC FOOTHILLS. OTHERWISE...NOTHING MORE THAN A
CHILLY RAIN CAN BE EXPECTED FOR ABOUT 80 PERCENT OF THE FORECAST
AREA. AS PRECIP FALLS INTO THE COOL/DRY AIR MASS NEAR THE SURFACE...
IN SITU/HYBRID COLD AIR DAMMING WILL DEVELOP...WITH TEMPS EXPECTED
TO REMAIN IN THE 30S THROUGH THE MORNING...IF NOT THROUGH THE ENTIRE
DAY.

PRECIPITATION WILL CONTINUE OVERSPREADING THE CWA FROM THE SOUTHWEST
THIS MORNING...IN ASSOCIATION WITH GULF COAST CYCLONE THAT WILL MOVE
UP AND JUST INLAND OF THE SOUTHEAST COAST THIS AFTERNOON INTO
TONIGHT. CATEGORICAL/100 POPS ARE A SLAM DUNK ACROSS THE ENTIRE CWA
BY LATE MORNING. OF PRIMARY CONCERN WILL BE THE POTENTIAL FOR WINTRY
WEATHER ACROSS THE MTNS...PRIMARILY THE HIGH ELEVATIONS...THE
VALLEYS FROM THE FRENCH BROAD NORTH...AND ESPECIALLY THE EASTERN
ESCARPMENT. THE LATEST OBSERVATIONS INDICATE WET BULB TEMPS IN THE
UPPER 20S TO LOWER 30S EVERYWHERE WITH THE EXCEPTION OF THE
SOUTHWEST NC VALLEYS...WHERE WET BULBS CONTINUE TO CREEP UP INTO THE
MID 30S. OVERALL...IT APPEARS THAT MOST LOCATIONS (WITH THE
EXCEPTION OF THOSE SW VALLEYS) SHOULD SEE SOME AMOUNT OF WINTRY
PRECIP...PROBABLY BEGINNING AS SNOW OR SLEET IN MOST AREAS...BEFORE
STRONG WARM ADVECTION ABOVE SHALLOW COOL/HYBRID COLD AIR DAMMING
LAYER ESTABLISHES A VERY STRONG WARM NOSE. IN FACT...THE LATEST
GUIDANCE DEPICTS TEMPS OF +5 TO +6 IN THE H8 TO H7 LAYER DEVELOPING
BY AFTERNOON. THIS WILL SUPPORT A TRANSITION TO FREEZING RAIN AND
THEN RAIN ACROSS THE VAST MAJORITY OF THE MTNS FROM LATE MORNING TO
EARLY AFTERNOON. IN FACT...THE TRANSITION FROM FZRA TO RA MAY OCCUR
QUITE QUICKLY IN MOST AREAS...CONSIDERING THE DEPTH AND STRENGTH OF
THE WARM NOSE...AND THE /SELF LIMITING/ NATURE OF FZRA.

HOWEVER...PERSISTENCE OF FREEZING RAIN INTO THE AFTERNOON WILL BE A
CONCERN ALONG THE EASTERN ESCARPMENT OF THE BLUE RIDGE...ESPECIALLY
FROM THE BLACK MOUNTAIN AREA NORTH TOWARD SPRUCE PINE/NEWLAND/
BLOWING ROCK...WHERE STOUT SE WINDS ABOVE THE COLD DOME WILL PROVIDE
A SOURCE OF COOLING OWING TO MECHANICAL LIFT. IN FACT...IF THE CAD
WERE A LITTLE STRONGER/MORE CLASSICAL IN NATURE...AND THE WARM NOSE
A LITTLE LESS PROMINENT...I/D PROBABLY PULL THE TRIGGER ON A WARNING
FOR THESE AREAS. AS SUCH...THERE/S TOO MUCH UNCERTAINTY CONCERNING
THE RESIDENCE TIME OF COLD AIR ALONG THE ESCARPMENT...AND I DON/T
HAVE THE CONFIDENCE TO UPGRADE ATTM. HOWEVER...THERE PROBABLY WILL
BE A FEW AREAS THAT DO APPROACH OR EVEN REACH ICE WARNING
CRITERIA...SO PLAN TO BEEF UP THE WORDING IN THE ADVISORY FOR THESE
AREAS.

OTHERWISE...THE HIGHEST RAINFALL TOTALS TODAY SHOULD EXIST SOUTHEAST
OF I-85...NEARER THE TRACK OF THE SURFACE LOW...WHERE AMOUNTS IN THE
1-1.5 INCH RANGE ARE EXPECTED. MOST OF THE REMAINDER OF THE AREA
SHOULD SEE .75-1.0 INCH...WITH HIGHER AMOUNTS LIKELY NEAR THE
ESCARPMENT.

MID-LEVEL DRY SLOTTING AND VEERING LOW LEVEL FLOW/DIMINISHING
ISENTROPIC LIFT SHOULD BRING AN END TO THE MORE ROBUST PRECIP RATES
THIS EVENING...ALTHOUGH PLENTY OF LINGERING LOW LEVEL MOISTURE MAY
SUPPORT PATCHY LIGHT RAIN AND DRIZZLE IN MANY LOCATIONS THROUGH THE
NIGHT. AFTER MIDNIGHT...COLD AIR ADVECTION WILL DEVELOP OVER THE
MTNS AS THE FLOW TURNS NW IN RESPONSE TO THE CYCLONE PUSHING OFF THE
MID-ATLANTIC COAST. SNOW LEVELS WILL BEGIN TO DROP ACROSS THE MTNS
DURING THIS TIME...AS DEFORMATION ZONE BAND APPROACHES FROM THE TENN
VALLEY. THIS WILL RESULT IN A SYNOPTICALLY ENHANCED NW FLOW SNOW
EVENT...WITH 1 TO 3 INCHES EXPECTED ALONG THE TENN BORDER...MAINLY
ABOVE 3000 FEET BY DAYBREAK SATURDAY.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AT 230 AM EST FRIDAY...ON SATURDAY MORNING AN UPPER TROUGH WILL BE
OVER THE EASTERN HALF OF THE CONTINENT....WHILE AN UPPER LOW WILL BE
OFF BAJA CALIFORNIA. A WELL DEFINED SHORTWAVE WILL BE MOVING THROUGH
THE BASE OF THE TROUGH AND ACROSS THE SOUTHERN APPALACHIANS. A
SECOND WEAKER SHORTWAVE CROSSES THE MOUNTAINS LATE IN THE DAY...AND
A THIRD MORE ROBUST SHORTWAVE CROSSES THE MOUNTAINS SATURDAY NIGHT.
YET ANOTHER SHORTWAVE APPROACHES FROM THE NW ON SUNDAY...CROSSING
THE AREA ON SUNDAY NIGHT.

AT THE SURFACE...COLD...MOIST NW FLOW INTO THE NC MOUNTAINS WILL
PERSIST SATURDAY MORNING...SUPPORTING CONTINUING SNOW SHOWERS UNTIL
WARMING OCCURS LATE IN THE MORNING. THE MODELS SHOW A DEFORMATION
ZONE CROSSING THE FOOTHILLS AND PIEDMONT DURING THE MORNING IN THE
WAKE OF THE DEPARTING SURFACE LOW...WITH THICKNESS VALUES QUITE LOW.
MODEL SOUNDINGS SUGGEST THAT NEAR SURFACE TEMPERATURES WILL BE WARM
ENOUGH FOR PRECIPITATION EAST OF THE MOUNTAINS TO BE IN THE FORM OF
RAIN. THE RAPID MOVEMENT OF THE DEFORMATION ZONE WOULD LIMIT BOTH
THE DURATION AND AMOUNT OF PRECIPITATION EAST OF THE MOUNTAINS...
WITH DRYING IN THE AFTERNOON.

THE MODELS BRING ADDITIONAL LOW LEVEL MOISTURE INTO THE NC MOUNTAINS
SATURDAY EVENING...MAINLY NORTH OF INTERSTATE 40. WITH THE TOP OF
THE MOIST LAYER TO WARM FOR ICE NUCLEATION...FREEZING RAIN WOLD BE
EXPECTED THERE. BRIEF DRYING IS EXPECTED EARLY SUNDAY...BEFORE
ANOTHER ROUND OF MOISTURE PRECEDING A COLD FRONT ARRIVES IN THE
MOUNTAINS. ANOTHER ROUND OF PRECIPITATION WOULD START IN THE
MOUNTAINS IN THE AFTERNOON...WITH SNOW LEVELS LOWERING THROUGH THE
EVENING. WITH SURFACE TEMPERATURES ABOVE FREEZING...RAIN SHOWERS ARE
EXPECTED TO ACCOMPANY THE FRONT ACROSS THE FOOTHILLS AND PIEDMONT
SUNDAY NIGHT...ENDING BEFORE DAYBREAK AS THE SURFACE LOW MOVES OFF
THE COAST. NW FLOW SNOW SHOWERS WOULD FOLLOW THE FRONT ALONG THE TN
BORDER LATE SUNDAY NIGHT...PERHAPS MIXING WITH SOME FREEZING RAIN AS
THE TOP OF THE MOIST LAYER BECOMES MARGINAL FOR ICE NUCLEATION.

TEMPERATURES WILL RUN NEAR NORMAL SATURDAY AND SATURDAY NIGHT.
TEMPERATURES WARM TO SEVERAL DEGREES ABOVE NORMAL AHEAD OF THE
SECOND FRONT...AND STAY ABOVE NORMAL SUNDAY NIGHT DUE TO CLOUD COVER
AND WIND.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 115 AM FRIDAY...THE OP MODELS CONTINUE TO SHOW VARYING
DISAGREEMENT WITH THE INCOMING H5 WAVE MON. THE 00Z GFS IS NOW THE
FRONT RUNNER AS FAR AS TIMING GOES AND IS NOT SUPPORTED BY IT/S OWN
ENS MEAN. THE ECMWF IS A GOOD COMPROMISE BTW THE CAM AND THE GFS.
CONFIDENCE IS PRETTY GOOD MON WITH THE CONTINUING NW FLOW EVENT AND
FROZEN PRECIP MAKING IT EAST OF THE MTNS...BUT THE EXTENT TO WHICH
THE NW FLOW SN CONTINUES IS NOT QUITE CLEAR WITH THE RENEGADE GFS
BRINGING IN A MOIST ULVL S/W ON THE HEELS OF THE DEPARTING TROF
AXIS. FOR NOW...WILL LET THE NWFS TAPER OFF AROUND NOON TUE.

ANOTHER COUPLE INCHES OF SNOWFALL IS PROBABLE ACROSS THE FAR WRN MTN
ZONES AND NRN MTNS MON WITH COLD H85 MOISTURE FLUX AND ORTHOGONAL
FLOW CONTINUING. THE UPPER TROF WILL BE DYNAMIC ENOUGH TO HELP
GENERATE -RA/SN ACROSS THE NC FHILLS AND PIEDMONT EARLY MON...AND
THEN POSSIBLY -SNSH/--SN MON NIGHT. CROSS SECTIONS SHOW A PRONOUNCED
AREA OF H7/H5 QG FRONTOGENESIS CROSSING THE NRN ZONES EARLY MON AND
THEN CHANNELED VORT MON NIGHT ENHANCING THE WANING MOISTURE MON
NIGHT. SOME VERY LIGHT SN ACCUMS ARE POSSIBLE MON NIGHT OVER THE NC
FHILLS/PMONT WITH PROFILES MAINTAINED BELOW FREEZING. A DRY FCST IS
IN STORE LATE TUE THROUGH THE PERIOD AS A S/W ULVL RIDGE AND A CP
SFC HIGH BUILD ACROSS THE OH/TN VALLEYS. MAX/MIN TEMPS WILL REMAIN
BELOW NORMAL...SLOWLY WARMING UP AS SW/LY RETURN FLOW DEVELOPS BY
THU.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
AT KCLT AND ELSEWHERE (EXCEPT KAVL/KHKY)...WIDESPREAD RAIN WILL
CONTINUE THRU THE AFTERNOON. CIGS AND VSBY WILL CONTINUE TO
DETERIORATE AS WELL. THAT SAID...IFR MAY BE DELAYED...BUT SHUD STILL
DEVELOP DURING THE AFTERNOON. ONCE CONDITIONS DETERIORATE...THEY
WILL BE SLOW TO RECOVER. RAIN IS EXPECTED TO BEGIN DIMINISHING BY
THIS EVENING...BUT CIGS AND VISBY SHOULD REMAIN LOW IN PERSISTENT
COOL WEDGE. NE WINDS IN THE 8-12 KTS RANGE ARE EXPECTED THROUGH THE
DAY...BECOMING LIGHT AND TURNING TOWARD THE NORTH TONIGHT.

AT KAVL/KHKY...THE WINDOW FOR A WINTRY MIX HAS CLOSED WITH ONLY RAIN
EXPECTED FOR THE REST OF THE PERIOD. OTHERWISE...LOWERING CIGS AND
VSBY ARE EXPECTED...BUT WILL BE DELAYED FROM PREVIOUS TIMING. IFR
CONDITIONS ARE EXPECTED BUT LATER. ONCE CONDITIONS DETERIORATE...
THEY WILL BE SLOW TO RECOVER. RAIN IS EXPECTED TO BEGIN DIMINISHING
BY THIS EVENING...BUT CIGS AND VISBY SHOULD REMAIN LOW IN PERSISTENT
COOL WEDGE.

OUTLOOK...RESTRICTIONS SHOULD CONTINUE INTO EARLY SATURDAY BEFORE
DIMINISHING FROM THE SW. A SERIES OF CLIPPER SYSTEMS WILL BRING SNOW
CHANCES TO THE AREA EARLY IN THE WEEK...MAINLY TO THE MTNS NORTH AND
WEST OF KAVL.

CONFIDENCE TABLE...

            15-21Z        21-03Z        03-09Z        09-12Z
KCLT       HIGH  81%     MED   77%     HIGH  81%     MED   76%
KGSP       MED   72%     HIGH  83%     HIGH  86%     HIGH  80%
KAVL       MED   77%     MED   70%     HIGH  84%     MED   73%
KHKY       HIGH  83%     HIGH  83%     HIGH  81%     HIGH  93%
KGMU       MED   72%     MED   78%     HIGH  81%     HIGH  80%
KAND       MED   74%     HIGH  83%     HIGH  81%     HIGH  83%

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...WINTER WEATHER ADVISORY UNTIL NOON EST SATURDAY FOR NCZ033-
     048>052-058-059-501-503-505.
SC...NONE.

&&

$$
SYNOPSIS...JAT
NEAR TERM...JDL/RWH
SHORT TERM...JAT
LONG TERM...SBK
AVIATION...JDL/RWH


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