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 221154
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
654 AM EST THU JAN 22 2015

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OVER THE REGION TODAY BEFORE AN AREA OF
LOW PRESSURE DEVELOPS ACROSS THE NORTHERN GULF OF MEXICO AND BRINGS
WIDESPREAD PRECIPITATION FRIDAY INTO SATURDAY. HIGH PRESSURE
BRIEFLY BUILDS IN SUNDAY...BEFORE A COLD AND MOIST LOW PRESSURE
SYSTEM AFFECTS THE FORECAST AREA SUNDAY NIGHT INTO TUESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF DAYBREAK...MID LEVEL CLOUDS CONTINUE TO STREAM IN FROM THE
WEST AS AN UPPER JET STREAK MOVES PAST.

IT LOOKS LIKE ONE MORE DAY OF BENIGN WEATHER AS WE AWAIT THE
DEVELOPMENT OF LOW PRESSURE OVER THE NW GULF. IN THE MEAN TIME...
HIGH PRESSURE MOVING FROM THE PLAINS TO THE MIDWEST WILL KEEP IT
DRY. WE WILL BE UNDER A FAST-MOVING QUASI-ZONAL FLOW ALOFT IN THE
CONFLUENT REGION OF THE SPLIT FLOW UPSTREAM. THE STRENGTHENING UPPER
LEVEL JET WILL BRING A STEADY INCREASE IN CLOUDINESS ACROSS THE
REGION TODAY. HIGH TEMPS WILL BE NOTICEABLY COOLER TODAY...BUT MIGHT
NOT BE COOL ENOUGH IF THE MID LEVEL CLOUDS THICKEN TOO EARLY IN THE
DAY.

THE MODELS STILL AGREE THAT LOW PRESSURE WILL ORGANIZE OVER THE NW
GULF TONIGHT IN RESPONSE TO A STRONG AND DEEP SHORT WAVE DIVING OVER
THE SRN PLAINS. DEEPENING MOISTURE WILL CONTINUE TO SPREAD NE FROM
THIS DEVELOPING SYSTEM AND SHOULD ARRIVE SOME TIME AFTER MIDNIGHT.
THE LATEST GUIDANCE HAS BACKED OFF SLIGHTLY ON THE TIMING OF THE
ONSET...WHICH MAKES SENSE GIVEN THE DRY SUB-CLOUD AIR THAT WILL HAVE
TO BE OVERCOME. THE COMBINATION OF MID/UPPER FORCING AND DEVELOPING
ISENTROPIC UPGLIDE SHOULD BRING THE LEADING EDGE OF THE LIGHT PRECIP
INTO NE GEORGIA...THE WRN-MOST PART OF UPSTATE SC...AND THE SRN MTNS
BY DAYBREAK. WILL BE RAMPING UP PRECIP CHANCES FROM THE SW QUICKLY
IN THE PRE-DAWN HOURS. THE PRECIP WILL PROBABLY NOT MAKE IT PAST I-
26 BEFORE THE END OF THE TONIGHT PERIOD. FCST SOUNDINGS SUGGEST THAT
WE SHOULD SEE A PERIOD OF WINTRY PRECIP AT ELEVATIONS ABOVE 3000
FEET OVER THE SRN MTNS AT ONSET BEFORE DAYBREAK...PERHAPS
ACCUMULATING AN INCH OR SO OF SNOW/SLEET...BEFORE CHANGING TO RAIN.
VALLEY LOCATIONS SHOULD BE MOSTLY RAIN...UNLESS COLD AIR BELOW 32F
GETS TRAPPED BEFORE THE PRECIP BEGINS. PROFILES MIGHT BE A BIT MORE
FAVORABLE FOR A LONGER PERIOD OF A WINTRY MIX OVER THE BALSAMS AND
UPPER FR BROAD VALLEY. AN ADVISORY MAY BE NEEDED ACROSS PART OR ALL
THE NC MTNS. AREAS OUTSIDE THE MTNS SHOULD BE RAIN...BUT A VERY
BRIEF MIX WITH SOME SLEET AND/OR SNOW FLAKES WILL NOT BE RULED OUT
AT ONSET.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 315 AM EST THURSDAY...THE SHORT TERM PERIOD INITIALIZES FRIDAY
MORNING AMIDST INTRUDING UPGLIDE PRECIP REGIME ASSOCIATED WITH
PARENT NORTHERN GULF SURFACE LOW.  MODELS HAVE SLOWED PRECIP ONSET
BY A FEW HOURS ON FRIDAY MORNING WHICH WILL IN TURN ALLEVIATE SOME
OF THE INITIAL WINTER WX IMPACTS INTO THE REGION.  SOUNDINGS ON
FRIDAY MORNING WILL SUPPORT RA/FZRA ACROSS THE SW MOUNTAINS WITH A
RA/SN/IP MIX TRENDING FURTHER NORTH.  USING A NON DIURNAL
TEMPERATURE TREND ON FRIDAY AS INSITU WEDGE PREVAILS...STILL
EXPECTING TEMPERATURES TO WARM TO ABOVE FREEZING FOR MOST LOCATIONS
THEREBY LEADING TO ALL LIQUID PRECIP BY AFTERNOON...WITH THE
POSSIBLE EXCEPTION OF THE HIGHEST ELEVATIONS.  INCREASED LOW/MID
LEVEL THICKNESSES INTO FRIDAY EVENING ALLOW FOR MODEST WARM NOSE
DEVELOPMENT ACROSS MUCH OF THE HIGH TERRAIN AHEAD OF THE ADVANCING
UPPER TROF AXIS AND CONSEQUENT COLD ADVECTION.

THEREFORE FCST FOR FRIDAY WILL FEATURE SOLID LIKELY/CATEGORICAL POPS
REGIONWIDE WITH A WINTRY MIX OF RA/SN/IP/FZRA ACROSS MUCH OF THE
WESTERN NC HIGH TERRAIN AT FCST INITIALIZATION WITH A BRIEF LULL IN
WINTER WX PTYPE CONCERNS LATE IN THE AFTERNOON. AS FOR THE REMAINDER
OF THE FCST AREA...TEMPERATURE PROFILES REMAIN WARM ENOUGH TO
PREVENT ANY FROZEN PRECIP WITH THE POSSIBLE EXCEPTION OF A FEW
FLURRIES OR SLEET PELLETS ACROSS THE NORTHWEST NC PIEDMONT AND
NORTHERN FOOTHILLS DURING THE MID/LATE MORNING HOURS.  BEYOND
THAT...REINTRODUCTION OF WINTRY PRECIP OCCURS FRIDAY NIGHT IN THE
FORM OF FZRA ACROSS MUCH OF THE HIGH TERRAIN WITH THE HIGHEST
PROBABILITIES BEING FURTHEST NORTH ACROSS THE NORTHERN MOUNTAIN
ZONES.  AS THE UPPER TROF AXIS SWINGS THROUGH SATURDAY MORNING FCST
FEATURES A CHANGE OVER TO ALL SNOW ACROSS THE MOUNTAINS WHEN
NORTHWEST FLOW BEGINS TO DOMINATE.

ALL SAID...SURFACE TEMPERATURES AND QPF WILL PLAY A HUGE ROLE IN THE
EVENTUAL EVOLUTION OF THIS EVENT...THUS ACCUMULATION UNCERTAINTY
REMAINS LOW.  AS OF NOW...FCST ACCUMULATIONS FOR BOTH SNOW/ICE
REMAIN BELOW WARNING CRITERIA...YET SATISFYING ADVISORY CRITERIA.
THUS...ADVISORY ISSUANCE MAY BE NEEDED SOON TO ACCOUNT FOR WINTRY
PRECIP AT ONSET FRIDAY MORNING.  A SECOND ADVISORY MAY BE NEEDED FOR
THE FRIDAY NIGHT TIMEFRAME WHEN FALLING SURFACE TEMPERATURES BENEATH
LOW/MID LEVEL WARM NOSE FAVORS POSSIBLE FZRA.  LASTLY...PRECIP IS
EXPECTED TO EXIT THE REGION SATURDAY MORNING/AFTERNOON AS THE
SURFACE LOW PULLS AWAY UP THE EAST COAST.  POPS WILL DECREASE ACROSS
THE EASTERN ZONES THROUGH SATURDAY WITH POPS LINGERING ALONG THE TN
LINE AS NORTHWEST UPSLOPE SNOW SHOWERS CONTINUE THROUGH PERIODS END.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 145 AM THURSDAY...SOME UNCERTAINTY EXISTS WITH THE EXT RANGE
FCST. THE MODELS HAVE VARYING IDEAS WRT TO THE TIMING AND STRENGTH
OF THE UPPER S/W PATTERN BEGINNING SUN MORNING...REMAINING OUT OF
SYNC THROUGH THE PERIOD. THE ECMWF IS ABOUT 6-9 HRS QUICKER THAN THE
GFS WITH THE CLIPPER LOW EVOLUTION...WHILE THE CMC GIVE BETTER
SUPPORT SYNOPTICALLY TO THE GFS. THUS...NO MAJOR CHANGES WERE MADE
TO THE GOING FCST.

NORTHWEST FLOW SNOW WILL BE WANING EARLY SUN WHILE THE COASTAL LOW
ADVANCES QUICKLY TOWARD NEW ENG AND H85 FLOW BECOMES W/LY. A LULL IN
PRECIP ACTIVITY WILL OCCUR SUN AFTERNOON BEFORE THE CLIPPER AIDED BY
STRONG ULVL FORCING ADVANCES ACROSS THE OH VALLEY. THIS WILL CREATE
A GOOD SETUP FOR UPSLOPE -SHRA ACROSS THE WRN NC MTNS SUN
AFTERNOON...CHANGING OVER TO SNOW AFTER 03Z MON. MOISTURE LEVELS
CONTINUE TO LOOK PRETTY HIGH UPSTREAM AS THE LOW DEEPENS OVER NOVA
AND ADVECTS GLAKES MOISTURE TOWARD THE MTNS. THE BEST SNOW RATES
LOOK TO BE OVERNIGHT MON WHERE ARND 2 INCHES IS PROBABLE. TEMP
PROFILES WILL SUPPORT MTN SNOW INTO MON EVENING AND EARLY TUES WITH
ADDITIONAL ACCUMS. AT THIS POINT IT LOOKS LIKE ADVISORY LEVEL SNOW
DUE TO THE LONG NATURE OF THE EVENT. A MIX OF RA/SN IS POSSIBLE
OUTSIDE THE MTNS ACROSS THE NC FOOTHILLS/PIEDMONT EARLY MON MORNING
THROUGH NOON AS UPPER DYNAMICS ALLOW A CONVECTIVE ENHANCEMENT BEFORE
THE BL WARMS ENUF FOR ALL RAIN. NO SIGFNT IF ANY ACCUMS OUTSIDE THE
MTNS ARE ANTICIPATED. LIGHT SNOW WILL WANE FAIRLY QUICKLY EARLY TUES
ACROSS THE NC MTN SPINE WITH LITTLE ADDITIONAL ACCUMS.

MAX TEMPS THROUGH THE PERIOD WILL BE RIGHT AROUND NORMAL SUN/MON AND
A COUPLE CATS BELOW NORMAL TUE/WED. MINS WILL BE ABOUT 5 DEGREES
ABOVE NORMAL SUN...AND NEAR NORMAL THE REMAINING MORNINGS.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...

AT KCLT AND ELSEWHERE...VFR CONDITIONS SHOULD PREVAIL THRU THE TAF
PERIOD. AN UPPER LEVEL JET STREAK WILL CONTINUE TO BRING MID AND
HIGH LEVEL CLOUDS STREAKING OVERHEAD THRU THE DAY. WIND SHOULD BE
LIGHT FROM A NW OR N DIRECTION. MOISTURE PROFILES WILL CONTINUE TO
DEEPEN AFTER SUNSET THIS EVENING...WITH CEILINGS GRADUALLY LOWERING
FROM THE SW. PRECIP SHOULD BEGIN TO SPREAD IN FROM THE SW AFTER
MIDNIGHT...BUT WILL HAVE DIFFICULTY REACHING THE GROUND AT FIRST.
THINK LIGHT RAIN WILL REACH KAND BEFORE 12Z FRIDAY...BUT THE NE
EXTENT OF THE PRECIP WILL BE NO FARTHER THAN I-26. WILL INTRODUCE
LIGHT RAIN AT KAND AT 10Z WITHOUT A VIS/CIG RESTRICTION...BUT EXPECT
A LOW CLOUD DECK TO BE MOVING IN FROM NE GEORGIA AT THAT TIME. WILL
KEEP KAVL/KGSP/KGMU WITH ONLY A VCSH FOR NOW. CANNOT RULE OUT SOME
SLEET OR SNOW RIGHT AT ONSET...ESPECIALLY AT KAVL...BUT THINK THE
BULK OF THE PRECIP WILL START RIGHT AFTER 12Z.

OUTLOOK...CONDITIONS WILL QUICKLY DETERIORATE FROM THE SW FRIDAY
MORNING AS MOISTURE AND PRECIP SPREAD NE FROM A DEVELOPING AREA OF
LOW PRESSURE OVER THE NW GULF. THE LOW WILL MOVE FROM THE NRN GULF
OF MEXICO TO THE SE COAST AND WILL BRING PRECIPITATION AND
RESTRICTIONS TO OUR AREA FRIDAY AND FRIDAY NIGHT. THERE COULD BE
WINTRY PRECIP FROM KAVL TO KHKY FOR SEVERAL HOURS ON FRIDAY.
ANOTHER SYSTEM ON MONDAY COULD BRING MORE RESTRICTIONS OVER THE
MTNS MAINLY NEAR THE TN BORDER THROUGH MONDAY NIGHT.

CONFIDENCE TABLE...

            12-18Z        18-24Z        00-06Z        06-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     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...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...SBK
NEAR TERM...PM
SHORT TERM...CDG
LONG TERM...SBK
AVIATION...PM


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