Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
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 310539
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
139 AM EDT TUE MAR 31 2015

.SYNOPSIS...
HIGH PRESSURE WILL REBUILD OVER THE REGION TODAY AND LINGER THROUGH
MOST OF TUESDAY. ANOTHER WEAK COLD FRONT WILL MOVE OVER THE AREA
TOMORROW NIGHT WITH HIGH PRESSURE QUICKLY BUILDING AGAIN FOR
WEDNESDAY AND THURSDAY. YET ANOTHER COLD FRONT IS EXPECTED TO
APPROACH THE CAROLINAS BY LATE FRIDAY.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 130 AM...ALL IS GOING ACCORDING TO PLAN. NO CHANGES WILL BE
MADE TO THE REST OF THE OVERNIGHT HOURS AT THIS TIME.

PREVIOUS DISCUSSION...

AS OF 1030 PM...DECENT MIXING PERSISTS ACROSS MUCH OF THE PIEDMONT
AND FOOTHILLS...AS WELL AS THE HIGH ELEVATIONS AND FRENCH BROAD
VALLEY IN WESTERN NC. MEANWHILE...DECOUPLING IS OCCURRING ACROSS THE
SOUTHWEST VALLEYS OF NC...WITH THE FRANKLIN AWOS ALREADY SITTING AT
45. STRONG RADIATIONAL COOLING CONDITIONS WILL PERSIST THROUGH THE
OVERNIGHT...AS WINDS CONTINUE TO DIMINISH AND SKIES REMAIN CLOUD-
FREE. I SUSPECT THAT SHELTERED/TYPICALLY COLD SPOTS SOUTHWEST OF THE
FRENCH BROAD VALLEY WILL LIKELY SEE A LIGHT FREEZE TONIGHT...BUT
CONFIDENCE IS TOO LOW IN WIDESPREAD-FREEZING TEMPS TO WARRANT AN
UPGRADE TO A WARNING...SO THE FROST ADVISORY WILL BE ALLOWED TO
STAND. MEANWHILE...THE MIDDLE AND LOWER FRENCH BROAD VALLEYS SHOULD
SEE A LIGHT UP-VALLEY WIND PERSIST UNTIL ABOUT DAYBREAK...LIKELY
PRECLUDING ANY FREEZE CONCERNS. OUTSIDE THE MTNS...TEMPS WERE BUMPED
UP A SMIDGE IN THE UPPER SAVANNAH RIVER VALLEY. THOSE AREAS SHOULD
TOO EVENTUALLY DECOUPLE...BUT TEMPS THERE ARE STILL IN THE LOWER 60S
AT THIS HOUR.

AS OF 735 PM...OTHER THAN SOME PATCHY CIRRUS PUSHING SOUTHEAST OF
OUR AREA ATTM...CLEAR SKIES COVER MUCH OF THE SOUTHEAST EARLY THIS
EVENING. THE MAIN CONCERN FOR THE VERY NEAR TERM IS OVERNIGHT
TEMPS...ESP OVER THE MTNS...AS A STRONG RADIATIONAL COOLING EVENT IS
BEGINNING TO TAKE SHAPE...ESP WITHIN THE SHELTERED VALLEYS. WHILE IT
APPEARS A LIGHT UP-VALLEY FLOW WILL PREDOMINATE ACROSS THE MID AND
LOWER FRENCH BROAD VALLEY...LIKELY PREVENTING TEMPS FROM CRATERING
TOO MUCH OVERNIGHT...THIS LOOKS LIKE A CASE IN WHICH STRONG
RADIATIONAL COOLING AND COOL AIR DRAINAGE WILL DO ITS BUSINESS
ACROSS THE LITTLE TENN VALLEY AND SURROUNDING DRAINAGES. MIN TEMPS
WERE THEREFORE LOWERED TO RIGHT AROUND FREEZING. IT DOESN/T APPEAR
THAT FREEZING TEMPS WILL BE WIDESPREAD ENOUGH TO WARRANT A FREEZE
WARNING...BUT THE FROST ADVISORY WILL BE EXPANDED TO INCLUDE THE
LITTLE TENN...AS WELL AS THE PIGEON RIVER DRAINAGES.

AS OF 245 PM...A COLD FRONT WILL COMPLETELY SWEEP EAST ACROSS THE
REGION BY EARLY THIS EVENING. IN THE WAKE OF THE FRONT...A FEW
DIURNAL CU WILL LINGER ACROSS THE CWA...PRIMARILY ALONG THE TN
BORDER. THE CU WILL DISSIPATE QUICKLY AS THE SUN SETS...LEAVING THE
REGION UNDER MOSTLY CLEAR CONDITIONS OVERNIGHT. AT THE SFC...NEAR
TERM MODELS INDICATE THAT THE CENTER OF HIGH PRESSURE WILL BUILD
ACROSS THE SOUTHERN APPALACHIAN REGION...RESULTING IN CALM TO LIGHT
AND VARIABLE CONDITIONS. FORECAST SOUNDINGS INDICATE THAT A BL
INVERSION WILL DEVELOP ACROSS THE REGION TONIGHT. AS THE INVERSION
LOWERS TONIGHT...VERY DRY AIR WILL BECOME EXPOSED TO THE MTN
RIDGES...LOWERING LATE NIGHT HIGH ELEVATION DEWPOINTS TO AROUND
ZERO. MTN VALLEY VALUES ARE FORECAST TO RANGE AROUND 30 DEGREES. LOW
TEMPERATURES SHOULD RANGE FROM THE MID 30S TO THE UPPER 30S ACROSS
THE I-40 CORRIDOR OF THE FOOTHILLS AND PIEDMONT...AREAS FROM THE
UPPER SAVANNAH RIVER VALLEY TO THE CLT METRO AREA RANGE AROUND 40.
THE COMBINATION OF CLOSE DEWPOINT DEPRESSIONS...CALM WINDS...AND MID
30S WILL LIKELY YIELD WIDESPREAD FROST WITHIN THE FRENCH BROAD
VALLEY TONIGHT. WE WILL HIGHLIGHT WITH A FROST ADVISORY FOR THE
FRENCH BROAD VALLEY. PATCHY FROST IS POSSIBLE ACROSS THE I-40
CORRIDOR.

ON TUESDAY...HIGH PRESSURE WILL SHIFT OVER THE WESTERN ATLANTIC AS A
COLD FRONT APPROACHES FROM THE WEST. RETURN FLOW SHOULD SUPPORT HIGH
TEMPERATURES REACHING INTO THE U60S ACROSS THE MTN VALLEYS AND LOW
70S EAST. DEWPOINTS SHOULD REMAIN MAINLY STEADY IN THE MID TO UPPER
30S. AFTERNOON RH VALUES ARE FORECAST TO RANGE IN THE MID TO UPPER
20S WITH GUST WINDS. AFTER COORDINATION WITH NCFS WE WILL HIGHLIGHT
THE NC ZONES FROM THE FRENCH BROAD VALLEY EAST ACROSS THE PIEDMONT
WITH A FIRE DANGER STATEMENT.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
OF 230 PM EDT MONDAY...AN UPPER TROUGH AND ASSOCIATED SURFACE LOW
WILL MOVE OFF THE EAST COAST TUE NIGHT. A TRAILING COLD FRONT FROM
THE EAST COAST LOW WILL MOVE ACROSS THE AREA TUESDAY NIGHT. SOME
CONVECTION ASSOCIATED WITH THE FRONT WILL MAKE A RUN AT THE NC
MOUNTAINS TUE EVENING. THE 12Z NAM IS MOST AGGRESSIVE IN BRINGING
SHOWERS/STORMS INTO THE MOUNTAINS. THE GFS IS MUCH MORE MUTED WITH
CAPES QUICKLY DWINDLING TUE EVENING AND THE EC ESSENTIALLY HAS A DRY
FRONTAL PASSAGE. HENCE...WILL NOT GO OVERBOARD WITH POPS...AND WILL
KEEP THINGS DRY EAST OF THE MOUTNAINS WITH DEEP LAYER W/NW FLOW
THROUGH THE COLUMN. WILL MAINTAIN THE LOW END CHANCE TO SLIGHT
CHANCE POPS OVER THE NC MOUNTAINS TUE EVENING. BEHIND THE
FRONT...HIGH PRESSURE IS FORECAST TO SETTLE OVER THE REGION FROM THE
NORTH PRODUCING CLEARING BY WED MORNING AND TEMPS A NOTCH ABOVE
CLIMO ON WED. QUIET CONDITIONS ARE EXPECTED TO CONTINUE THROUGH WED
NIGHT AS THE HIGH MOVES OFF THE EAST COAST.

AS SOUTHERLY FLOW KICKS IN ON THURSDAY...MOISTURE WILL INCREASE
ACROSS THE AREA. A WEST TO EAST MOVING SHORT WAVE WILL ACT WITH THE
INCREASED MOISTURE TO PRODUCE SCATTERED SHOWERS AND PERHAPS A FEW
THUNDERSTORMS THURSDAY AFTERNOON. TEMPS ON THU WILL BE NEAR CLIMO
WITH INCREASED CLOUD COVER AND SCT PRECIP.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AT 230 PM EDT MONDAY...ON FRIDAY EVENING NEARLY ZONAL FLOW WILL BE
OVER THE SOUTHERN TIER OF STATES AS WEAK UPPER RIDGING WILL BE OFF
THE EAST COAST...AND LOW AMPLITUDE TROUGHING WILL EXTEND FROM THE
UPPER MIDWEST TO THE SW USA. THE UPPER TROUGH MOVES TO THE GREAT
LAKES AND CENTRAL MS RIVER VALLEY BY SATURDAY...BUT UPPER FLOW
REMAINS ALMOST ZONAL OVER THE SOUTHEAST. THE TROUGH AMPLIFIES
SLIGHTLY AS IT CROSSES THE SOUTHERN APPALACHIANS...THEN DEAMPLIFIES
AS IT MOVES OFF THE EAST COAST ON SUNDAY.  BY LATE SUNDAY THE MODELS
GO OUT OF PHASE OFF EACH COAST...RESULTING IN DIFFERENCES IN FLOW
OVER THE SE.

AT THE SURFACE...A COLD FRONT WILL APPROACH FROM THE NW ON THURSDAY
NIGHT AND FRIDAY...PRECEDED BY ROBUST GULF INFLOW INTO THE SOUTHERN
APPALACHIANS. THE FRONT CROSSES OUR AREA EARLY SATURDAY...FOLLOWED
BY DRY HIGH PRESSURE ON SUNDAY. BY MONDAY THE SURFACE HIGH MOVES OFF
THE EAST COAST...BUT HIGH PRESSURE REMAINS LODGED ALONG THE EASTERN
SEABOARD...WHILE GULF INFLOW SPREADS MOISTURE UP THE MS...TN AND OH
RIVER VALLEYS. THIS MOISTURE AND ASSOCIATED RAINFALL SPREADS EAST
ACROSS OUR AREA DURING THE DAY. TEMPERATURES WILL RUN ABOVE NORMAL
AHEAD OF THE FIRST FRONT...SLIGHTLY BELOW NORMAL BEHIND IT...THEN
RETURN TO ABOVE NORMAL AHEAD OF THE SECOND FRONT.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
AT KCLT AND ELSEWHERE...VFR THROUGH THE PERIOD...WITH MOSTLY CLEAR
SKY AND A LIGHT WIND THROUGH DAYBREAK. S/SW WINDS WILL THEN DEVELOP
AFTER SUNRISE...REACHING THE 10-15 KT RANGE AT MOST TERMINALS DURING
THE AFTERNOON. SOME GUSTS TO AROUND 20 KTS WILL ALSO BE POSSIBLE
DURING THAT TIME. A SURFACE FRONT TO THE SOUTH AND SOUTHWEST MAY
ACTIVATE AS A WARM FRONT THIS AFTERNOON...BUT AT THIS POINT IT DOES
NOT APPEAR THAT ANY SHOWER ACTIVITY WILL REACH CLOSE TO ANY OF THE
TAF SITES. EXPECT A FEW TO SCT CLOUDS WITH BASES AROUND 060 THIS
AFTERNOON AND EVENING. WIND GUSTS SHOULD DIMINISH WITH SUNSET.

OUTLOOK...VFR THROUGH WEDNESDAY. AN APPROACHING WARM FRONT AND
RESULTANT MOISTURE RETURN WILL BRING BETTER CHANCES FOR
PRECIP/RESTRICTIONS ACROSS THE AREA LATER IN THE WEEK...PERHAPS
STARTING THURSDAY MORNING. A COLD FRONT WILL AFFECT THE AREA FRIDAY
INTO EARLY SATURDAY...BRINGING ANOTHER ROUND OF RAIN/POSSIBLE
THUNDERSTORMS AND RESTRICTIONS.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-00Z
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 UNTIL 9 AM EDT THIS MORNING FOR NCZ048-051>053-
     058-059-062-065.
     FIRE DANGER STATEMENT FROM NOON EDT TODAY THROUGH THIS
     AFTERNOON FOR NCZ033-035>037-048>050-053-056-057-065-
     068>072-082-501>510.
SC...NONE.

&&

$$
SYNOPSIS...JPT
NEAR TERM...JDL/NED/PM
SHORT TERM...LG
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.