Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 280224
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1024 PM EDT MON APR 27 2015

.SYNOPSIS...
A LARGE COOL AND DRY AIR MASS WILL DOMINATE THE WEATHER ACROSS THE
SOUTHERN APPALACHIAN REGION THROUGH TUESDAY. A WELL ORGANIZED LOW
PRESSURE SYSTEM WILL LIFT ACROSS THE DEEP SOUTH...TRACKING ALONG THE
ATLANTIC COAST DURING THE MID WEEK. ANOTHER CANADIAN AIR MASS WILL
SETTLE BACK OVER THE REGION DURING THE LATE WEEK AND WILL REMAIN
INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 1030 PM...ALL IS QUIET ACROSS THE WESTERN CAROLINAS AND NE
GEORGIA. PATCHES OF THICKER CIRRUS WERE HELPING TO KEEP TEMPS A BIT
WARMER THAN EXPECTED AT THIS TIME OF THE EVENING...SO AN UPWARD
ADJUSTMENT WAS MADE TO THE COOLING TREND. STILL TOO EARLY TO GIVE UP
ON THE MIN TEMPS...THOUGH.

PREVIOUS DISCUSSION...

 AS OF 230 PM...A SHORT WAVE ROTATES ACROSS THE AREA TONIGHT IN THE
CYCLONIC FLOW AROUND AN UPPER LOW MOVING EAST AWAY FROM THE NEW
ENGLAND COAST. AT THE SFC...HIGH PRESSURE NOSES IN FROM THE NW
OVERNIGHT. EXPECT THE CU OUTSIDE OF THE MTNS TO DIMINISH THRU THIS
EVENING...BUT WILL LINGER A LITTLE LONGER ACROSS THE MTNS UNTIL THE
NW FLOW ABATES AFTER MIDNIGHT. THERE WILL ALSO BE QUITE A BIT OF
CIRRUS OVERNIGHT AS UPPER LEVEL MOISTURE MOVES IN WITH A JET STREAK.
THIS CIRRUS WILL HELP KEEP TEMPS FROM BOTTOMING OUT ACROSS THE AREA.
HOWEVER...TEMPS WILL STILL FALL ENUF FOR FROST TO DEVELOP ACROSS THE
NC MTNS. THE FROST SHUD BE WIDESPREAD ENUF FOR A FROST ADVISORY
ALONG THE TN BORDER COUNTIES FROM SWAIN NORTH...INCLUDING THE NRN
BLUE RIDGE PORTIONS OF THE FOOTHILLS. EXPECT PATCH FROST ACROSS THE
REST OF THE NC MTNS...AND POSSIBLY NORMALLY COLDER LOCATIONS OF THE
I-40 CORRIDOR. LOWS WILL BE AROUND 5 DEGREES BELOW NORMAL.

THE FLOW BECOMES MORE WLY TUE AS THE NEW ENGLAND UPPER LOW MOVES
FARTHER OFF SHORE AND A SRN PLAINS UPPER LOW MOVES INTO THE
MID-SOUTH. AT THE SFC...HIGH PRESSURE CONTINUES TO BUILD INTO THE
AREA AS A LOW PRESSURE SYSTEM MOVES ALONG THE CENTRAL GULF COAST.
CLOUDS WILL INCREASE THRU THE DAY AHEAD OF THIS SYSTEM...BUT ALL
GUIDANCE HAS BACKED OFF ON THE SPEED OF THE PRECIP WITH THE LOW.
THEREFORE...HAVE SLOWED PRECIP ONSET AS WELL UNTIL AFTER THE TUE
PERIOD. ALTHOUGH MID AND UPPER LEVEL CLOUDS INCREASE THRU THE DAY...
THERE MAY BE LITTLE IN THE WAY OF LOW CLOUDS AS LOW LEVEL MOISTURE
IS LIMITED AND ISENTROPIC LIFT IS DELAYED EVEN WITH LOW LEVEL FLOW
TURNING SELY. THE CLOUDS AND LOWER THICKNESSES WILL LIMIT HEATING
AND KEEP HIGHS 5 TO 10 DEGREES BELOW NORMAL.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
OF 200 PM MONDAY...MAIN FOCUS FOR THE SHORT TERM IS THE SOUTHERN
STREAM UPPER LOW MOVING EASTWARD ACROSS THE DEEP SOUTH. AN ATTENDANT
SURFACE CYCLONE IS FORECAST TO BE JUST EAST OF THE MISSISSIPPI DELTA
REGION AT 00Z WED AND IS FORECAST TO TRACK EASTWARD TO THE SC COAST
BY 00Z THU AND THEN TURN NORTHWARD UP THE EAST COAST ON THU IN
RESPONSE TO ANOTHER UPPER LOW DIGGING RAPIDLY SOUTHWARD THROUGH THE
GREAT LAKES.

ALL THIS PORTENDS SEVERAL FORCING MECHANISMS AFFECTING THE WESTERN
CAROLINAS AND NE GA BEGINNING TUE NIGHT. UPPER DIVERGENCE COMBINED WITH
ISENTROPIC UPGLIDE AND UPSLOPE FLOW IN COMBINATION WITH ACCOMPANYING
DEEP MOISTURE WILL RESULT IN A RAPID INCREASE IN RAINFALL COVERAGE
BY EARLY WEDNESDAY. THE TRANSITORY NATURE OF THE WEATHER SYSTEM AND
LACK OF CONVECTIVE ELEMENTS SHOULD PRECLUDE EXCESSIVE RAINFALL
TOTALS THAT WOULD PRESENT HYDRO ISSUES. HOWEVER...A SOAKING RAIN IS
EXPECTED WITH RAINFALL TOTALS GENERALLY AROUND 1 INCH OR SO. THE
SOUTHERN TRACK OF THE LOW WILL KEEP THE AREA UNDER A COOL NE FLOW AT
THE SFC. THEREFORE...TEMPS ON WED WILL SHOW LITTLE DIURNAL CHANGE.
WILL LEAN TOWARD THE RAWBLEND GUIDANCE FOR MAX TEMPS WHICH WILL TAMP
DOWN HIGHS INTO GENERALLY THE LOW TO MID 50S ACROSS THE REGION.

THE BULK OF THE PRECIP WILL MOVE EAST OF THE AREA WED NIGHT AS THE
SFC LOW TRACKS OFF THE CAROLINA COAST. OUR ATTENTION THEN TURNS TO
AN ANOMALOUS UPPER LOW PLUNGING QUICKLY SE FROM THE GREAT LAKES. THE
UPPER LOW WILL REACH THE WESTERN CAROLINAS AND NE GA LATE THURSDAY
AND IT WILL BE ACCOMPANIED BY A SURFACE COLD FRONT. THE 12Z NAM AND
GFS RESPOND WITH SHOWERS THU AFTERNOON AS THE UPPER FORCING AND
COLD FRONT ARRIVE. THEY ALSO DEVLOP A FEW HUNDRED JOULES OF CAPE...SO
SOME RUMBLES OF THUNDER MAY OCCUR. WITH FREEZING LEVELS FALLING TO
AROUND 5000 FT OR SO IN THE MOUNTAINS SOME GRAUPEL MAY OCCUR WITH
SOME OF THE CONVECTIVE CELLS. TEMPS WILL REMAIN BELOW CLIMO ON THU
WITH 50S IN THE MOUNTAINS AND 60S ELSEWHERE.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 200 PM EDT MONDAY...THE MEDIUM RANGE FCST PERIOD INITIALIZES
THURSDAY EVENING AMIDST A DEPARTING SURFACE LOW OVER THE WESTERN
ATL...WHILE A SECONDARY UPPER SHORTWAVE DIVES SOUTH FROM THE GREAT
LAKES REGION.  NOT MUCH CHANGE FROM PREVIOUS FCST REGARDING SAID
UPPER WAVE AS MODELS CONTINUE TO WARRANT LOW END CHANCE TO SLIGHT
CHANCE POPS OVER THE FCST AREA THROUGH FRIDAY MORNING WITH THE
HIGHEST POPS RESIDING OVER THE NC HIGH TERRAIN WHERE NW FLOW
UPSLOPING WILL AID SHOWER DEVELOPMENT.  THE FCST DRIES OUT THROUGH
FRIDAY...THEN REMAINS DRY THROUGH THE WEEKEND AS DEEP LAYER RIDGING
PREVAILS.  THAT SAID...MODELS DO HINT AT LOW CHANCES FOR PRECIP ON
SUNDAY AFTERNOON ACROSS THE NC MTNS WITH MAX HEATING...HOWEVER KEPT
ANY MENTION OUT OF FCST AS UPPER RIDGE IS EXPECTED TO PROVIDE AMPLE
SUBSIDENCE.  ON MONDAY SAID RIDGE BEGINS TO FLATTEN AS A MORE POTENT
UPPER WAVE DEVELOPS OVER THE CENTRAL/NORTHERN PLAINS.  THUS DID
INTRODUCE SLIGHT CHANCE POPS ACROSS THE NC MOUNTAINS AND NORTHERN
FOOTHILLS AS ANY CAPPING COULD BE WEAKENED AMIDST DIURNAL INDUCED
INSTABILITY.  TEMPERATURES THROUGH THE PERIOD WILL MODERATE TO ABOVE
NORMAL LEVELS.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
AT KCLT AND ELSEWHERE...EXPECT VFR CONDITIONS THROUGH THE PERIOD.
SCT VFR CU EARLY THIS EVENING WILL BECOME FEW AFTER SUNSET WITH
CIRRUS BECOMING BKN. THERE APPEARS TO BE LITTLE CHANCE OF
RESTRICTIONS THROUGH THE EARLY MORNING HOURS. VARIABLE NW/N/NE WIND
THIS EVENING SHOULD SETTLE INTO A LIGHT NNE BY LATE THIS EVENING...
AND THEN STAY NE ON TUESDAY. GUSTS OVER THE MTNS SHOULD ABATE BY
03Z. ON TUESDAY...EXPECT INCREASING HIGH CLOUDS...WITH A LOW CLOUD
DECK APPROACHING FROM THE SW LATE IN THE PERIOD. THINK ANY LOW CLOUD
CEILING BELOW 060 WILL HOLD OFF UNTIL AFTER 00Z WEDNESDAY.

OUTLOOK...A LOW PRESSURE SYSTEM WILL TRACK ACROSS THE DEEP SOUTH
WEDNESDAY AND THURSDAY THEN UP THE ATLANTIC COAST FRI...WITH CEILING
AND VSBY RESTRICTIONS POSSIBLE.

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 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...FROST ADVISORY FROM 2 AM TO 9 AM EDT TUESDAY FOR NCZ033-
     048>052-501-503-505.
SC...NONE.

&&

$$
SYNOPSIS...ARK
NEAR TERM...PM/RWH
SHORT TERM...LG
LONG TERM...CDG
AVIATION...PM


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