Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 270009
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
709 PM EST THU FEB 26 2015

.SYNOPSIS...
IN THE WAKE OF A COLD FRONT...COLD CANADIAN HIGH PRESSURE WILL BUILD
IN FRIDAY AND SLOWLY WARM THROUGH THE WEEKEND. ABOVE NORMAL
TEMPERATURES SHOULD RETURN TO THE AREA BY MONDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
645 PM UPDATE...THE LOW CLOUDS ACRS THE REGION SCATTERED LATE IN THE
DAY BUT A FAIR AMOUNT OF THEM WILL PERSIST OVERNIGHT BENEATH
ELEVATED INVERSION. WEAK FROPA ON TAP FOR LATE EVENING AS HIGH
PRESSURE STARTS TO BUILD IN FROM THE NW. THIS STANDS TO BRING
A PERIOD OF INCREASED CLOUD COVER AND SOME LOW PRECIP CHANCES TO THE
NW PIEDMONT. SFC TEMPS AND THERMAL PROFILES INDICATE A RA/FZRA SPLIT
OVER THIS AREA...BUT MINIMAL ACCUMULATION IS EXPECTED. CONSIDERING
LINGERING SNOW COVER...AND MOIST SOILS WHERE SNOW MELTED
TODAY...SOME SHALLOW GROUND FOG IS POSSIBLE. ADDED A FOG MENTION
TO PARTS OF THE AREA LATE TONIGHT...MAINLY OVER THE SRN HALF OF THE
CWFA WHERE DEWPOINTS REMAIN HIGHEST.

AS OF 220 PM EST THURSDAY...SKY COVER SHOULD DIMINISH A BIT BY LATE
TOMORROW MORNING AND AFTERNOON AS PROFILES CONTINUE TO GRADUALLY
DRY. OTHERWISE...LOW TEMPS ARE STILL ON TRACK TO BOTTOM OUT BELOW
FRZ FOR ALL ZONES EXCEPT POSSIBLY THE VERY SOUTHERNMOST AREAS. A
WINTER WX ADVISORY WILL BE ISSUED FOR WIDESPREAD BLACK ICE FOR ALL
BUT OUR SOUTHERN TIER COUNTIES FOR TONIGHT THRU TOMORROW MORNING. AN
SPS FOR PATCHY BLACK ICE WILL BE ISSUED FOR THE REMAINING ZONES.
HIGHS TOMORROW WILL BE SIMILAR TO TODAY WITH 40S OVER MOST OF THE
LOWER ELEVATIONS AND COOLER TEMPS FOR MOST OF THE HIGHER TERRAIN.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 240 PM THURSDAY...FORECAST DOES NOT GET ANY LESS TRICKY FOR
THE WEEKEND. GUIDANCE SHOWS SOME WEAK WAVES MOVING ACROSS THE AREA
IN THE FLATTENING UPPER FLOW. AT THE SFC...HIGH PRESSURE BUILDS INTO
THE MID ATLANTIC STATES AND RIDGES SOUTHEAST INTO THE AREA AS A
HYBRID COLD AIR DAMMING EVENT DEVELOPS. THE GFS IS ALONE IN
DEVELOPING SOME LIGHT PRECIP FRI NITE AND SAT AS SOME WEAK
ISENTROPIC LIFT DEVELOPS AS THE THE CAD SETS UP. WILL LEAVE THE FCST
DRY FOR NOW. HOWEVER...DO KEEP CLOUD COVER QUITE HIGH AS THERE WILL
BE SOME MOISTURE TRAPPED UNDER THE DEVELOPING SUBSIDENCE INVERSION.
THE CONTINUED COLD THICKNESSES AND CLOUDS WILL KEEP LOWS AROUND 10
DEGREES BELOW NORMAL AND HIGHS 15 TO 20 DEGREES BELOW NORMAL. DEEP
MOISTURE INCREASES LATE SAT NITE INTO SUNDAY AS SLY LOW LEVEL FLOW
DEVELOPS AHEAD OF AN APPROACHING COLD FRONT. ALL GUIDANCE IS IN
AGREEMENT ON THIS DEVELOPMENT. HOWEVER...THE ECMWF AND GFS ARE
SLOWER TO DEVELOP THE DEEP MOISTURE AND LOW LEVEL ISENTROPIC LIFT
WHILE THE NAM AND SREF ARE FASTER. THE GEFS ENSEMBLE MEAN KEEPS BEST
CHC POP UNTIL AFTER 18Z...BUT MODEL BLENDS SHOW SLIGHT CHC POP
DEVELOPING LATE SAT NITE WITH CHC POP DEVELOPING BY NOON SUNDAY AND
EVEN SOME LIKELY POP ALONG THE NC/SC/GA BORDERS BY THE END OF THE
DAY. HAVE GONE WITH THE MODEL BLEND TIMING FOR NOW GIVEN THE
UNCERTAINTY. SFC TEMPS WILL BE COLD DURING THIS TIME AND ALL
OPERATIONAL AND ENSEMBLE MEAN GUIDANCE SHOWS FREEZING RAIN WOULD
DEVELOP IN MANY AREAS WITH THE EARLIER ONSET. HAVE FOLLOWED THIS
TREND AS WELL...BUT ALSO FOLLOW THE TREND OF WARMING TEMPS DURING
THE DAY WITH P-TYPE CHANGING TO ALL LIQUID AROUND NOON. THIS IS IN
LINE WITH THE CENTER OF THE HIGH PRESSURE MOVING OFF SHORE BUT
REMAINING RIDGED INTO THE AREA...LIMITING ANY MAINTENANCE FLOW OF
DRY AND COLD AIR INTO THE DAMMING REGION. STILL...HIGHS WILL REMAIN
ON THE COOL SIDE IN THE DAMMING REGION...WITH HIGHS 15 TO 20 DEGREES
BELOW NORMAL...AND HIGHS WARMING ACROSS MUCH OF THE MTNS TO 5 TO 10
DEGREES BELOW NORMAL. FOR NOW...EXPECT ANY EARLY QPF TO BE VERY
LIGHT WITH LITTLE TO NO ICE ACCRETION. LOWS SAT NITE 5 TO 10 DEGREES
BELOW NORMAL.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 230 PM THURSDAY...THE MEDIUM RANGE WILL START OUT WITH A BROAD
UPPER RIDGE ACRS THE SOUTHEAST STATES...AND A RATHER DEEP TROF INVOF
THE CALIF COAST. AT THE SFC...A COLD FRONT WILL SLIDE THRU THE AREA
FROM THE NORTH ON MONDAY...WITH SOME MOISTURE AND LIFT AROUND TO
WARRANT MAINLY CHC POPS ACRS THE EASTERN HALF OF THE CWFA AND LIKELY
POPS IN THE WEST FOR SUNDAY NIGHT AND MONDAY. TEMPS LOOK TO BE WARM
ENUF TO KEEP PRECIP AS ALL RAIN.

MONDAY NIGHT THRU TUESDAY NIGHT...A 1028-1032 MB HIGH PRES WILL
QUICKLY TRANSLATE EAST ACRS THE GREAT LAKES AND THE NORTHEAST
STATES...RESULTING IN COLD AIR DAMMING SETTING UP ACRS THE REGION.
AT THIS POINT...THE GFS AND ECMWF REALLY DIVERGE ON THE SENSIBLE WX
FCST FOR THE CWFA...WITH THE GFS MUCH WETTER...WHILE THE EC IS DRY.
I WENT WITH THE SUPERBLEND/WPC GUIDANCE WHICH LOOKS LIKE A
COMPROMISE FOR POPS. THE ECMWF IS COLDER...AND LOCKS IN A MORE
NOTABLE IN-SITU WEDGE ONCE IT BRINGS PRECIP BACK IN TUESDAY NIGHT.
AGAIN...I WENT WITH COMPROMISE ON TEMPS...BUT LEANING TOWARD THE
COOL SIDE OF GUIDANCE FOR HIGHS TUESDAY.

WEDNESDAY THRU THURSDAY NIGHT...MODEL SPREAD CONTINUES TO INCREASE
WITH HANDLING A CYCLONE TRACKING THRU THE PLAINS INTO THE GREAT
LAKES...AS THE UPPER TROF PROGRESSES EAST FROM THE ROCKIES TO THE
PLAINS. THE GFS IS DEEPER AND FASTER WITH THE LOW...BUT HAS A
SECONDARY WAVE DEVELOP ALONG THE FRONT OVER THE GULF STATES AND
TRACK THRU THE AREA WEDNESDAY NIGHT. THE ECWMF IS OVERALL SLOWER
WITH THE FRONT...SHOWING MORE OF AN ANAFRONT PRECIP PATTERN THRU
THURSDAY. IN EITHER CASE...WE COULD SEE A HEAVY RAIN EVENT...WITH
ONE OR TWO ROUNDS OF DECENT QPF...AS THE FRONT SLOWLY PUSHES THRU
FROM THE NORTHWEST. THE LATEST DAYS 6-7 QPF GUIDANCE FROM WPC SHOWS
OVER AN INCH OF QPF ACRS THE PIEDMONT AND 1-3" ACRS THE MTNS. GOING
WITH LIKELY TO CATEGORICAL POPS FOR WED-WED NIGHT...AND CHC POP FOR
THU-THU NIGHT. THE AREA SHUD BE IN THE WARM SECTOR OF THE PLAINS LOW
ON WEDNESDAY...SO ABOVE NORMAL TEMPS IN THE 60S FOR MOST OF THE AREA
EXPECTED. NEAR NORMAL TEMPS FOR THURSDAY...AS COLD FRONT PUSHES THRU.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
AT KCLT...VERTICAL PROFILE CHARACTERIZED BY A MIDLEVEL INVERSION AND
A FAIR AMOUNT OF LLVL MOISTURE. A LOW VFR CIG IS EXPECTED TO LINGER
THRU THE EVENING. WEAK COLD FRONT WILL PUSH THRU AROUND MIDNIGHT BUT
THE CHANCE OF ANY PRECIP IS TOO LOW TO MENTION. HOWEVER AN MVFR CIG
WILL LIKELY RETURN FOR A WHILE INVOF THE FRONT...DRIER AIR WORKING
IN BEHIND IT AND LIFTING TO VFR IF NOT SCATTERING ALTOGETHER. SOILS
ARE VERY WET AFTER SNOWMELT ON THU...AND THOUGH DEWPOINTS WILL BE ON
THE DRY SIDE SOME FOG MAY COME AND GO NEAR DAYBREAK. TEMPS ARE
LIKELY TO BE SUBFREEZING AT THAT TIME AND LIGHT ICE DEPOSITION WOULD
BE EXPECTED IF THE FOG WERE SUFFICIENTLY DENSE. I FELT A TEMPO
FOR MVFR VSBY WAS WARRANTED. WILL ADVISE NEXT SHIFT OF FZFG RISK.
FLOW WILL REMAIN CALM OR VERY LIGHT NORTHERLY TONIGHT...VEERING
SLIGHTLY ON FRI. STRATOCU DEVELOPMENT DURING THE AFTN IS EXPECTED TO
BRING CIGS DOWN TO NEAR MVFR/VFR THRESHOLD.

ELSEWHERE...SIMILAR TO KCLT WITH CLOUDS LIKELY TO LINGER
OVERNIGHT BENEATH AN ELEVATED INVERSION...THOUGH INITIALLY VFR FOR
THE MOST PART. NWLY FLOW AND SOME SFC INSTABILITY COULD PRODUCE SOME
LIGHT SNOWFALL NEAR THE TENN BORDER AND MVFR CIGS SPILLING OVER TO
KAVL MOST OF THE NIGHT. FRONT ARRIVING LATE EVENING SHOULD BRING
MVFR BACK FOR A TIME. PRECIP CHANCES ARE TOO LOW TO MENTION AT ANY
TAF SITES...BUT A SLIGHT CHC OF RA OR FZRA /DEPENDENT ON SFC TEMP/
EXISTS OVER THE NRN FOOTHILLS AND NW PIEDMONT OF NC...NEAR KHKY.
PATCHY LIGHT FOG WILL LIKELY FORM OVER PIEDMONT NC AND THE UPSTATE
WHERE SFC RH IS HIGH ENOUGH. A TEMPO MVFR MENTION IS MADE AT
KGSP/KGMU AND IFR AT KAND...THE LATTER BEING NEARER LAKE HARTWELL.
LIGHT NORTHERLY WINDS WILL VEER SLIGHTLY OVER THE COURSE OF THE DAY
FRI WITH CONTINUING LOW VFR CIGS.

OUTLOOK...LOW LEVEL MOISTURE WILL LINGER THROUGH THE REMAINDER OF
THE WEEK AND INTO THE WEEKEND AS COLD AIR DAMMING BUILDS FROM
THE NORTH ON SATURDAY. FLIGHT RESTRICTIONS WILL BE POSSIBLE DURING
THIS TIMEFRAME...ESPECIALLY ON SUNDAY ONCE MOISTURE SPREADS IN FROM
THE SOUTH AND CIGS LOWER.

CONFIDENCE TABLE...

            13-19Z        19-01Z        01-07Z        07-12Z
KCLT       HIGH  95%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   74%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       MED   77%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     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...WINTER WEATHER ADVISORY UNTIL 10 AM EST FRIDAY FOR GAZ010-017-
     018.
NC...WINTER WEATHER ADVISORY UNTIL NOON EST FRIDAY FOR NCZ033-
     048>053-058-059-062>065-501-503-505-507-509.
     WINTER WEATHER ADVISORY UNTIL 10 AM EST FRIDAY FOR NCZ035>037-
     056-057-068>072-082-502-504-506-508-510.
SC...WINTER WEATHER ADVISORY UNTIL 10 AM EST FRIDAY FOR SCZ001>009.

&&

$$
SYNOPSIS...CSH
NEAR TERM...JPT/WIMBERLEY
SHORT TERM...RWH
LONG TERM...ARK
AVIATION...WIMBERLEY


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