Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 240247
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1047 PM EDT SAT APR 23 2016

.SYNOPSIS...
DRY HIGH PRESSURE WILL BUILD OVER THE REGION FROM THE NORTH
THROUGH SUNDAY. AS THE HIGH MOVES OFFSHORE EARLY IN THE WORK
WEEK...SOUTHWESTERLY FLOW WILL ALLOW MOISTURE TO GRADUALLY RETURN
ACROSS THE SOUTHERN APPALACHIANS. A BACK DOOR COLD FRONT WILL
APPROACH FROM THE NORTH LATE TUESDAY AND STALL OVER THE AREA ON
WEDNESDAY BEFORE RETURNING NORTH AS A WARM FRONT ON THURSDAY.

&&

.NEAR TERM /THROUGH SUNDAY/...
AS OF 1045 PM...CONDITIONS ACROSS THE CWA REMAIN VERY QUIET. THE
FORECAST REMAINS IN GOOD SHAPE...I WILL UPDATE THE EARLY HOURS TO
ALIGN WITH RECENT OBSERVATIONS TRENDS. MORNING VALLEY FOG STILL
APPEARS LIKELY AROUND SUNRISE.

AS OF 9 PM...SFC HIGH PRESSURE CENTERED OVER THE GREAT LAKES WILL
BUILD OVER THE WESTERN CAROLINAS THROUGH SUNDAY MORNING. MTN VALLEY
WINDS MAY BECOME CALM DURING THE PRE DAWN HOURS...FAVORING THE
DEVELOPMENT OF VALLEY FOG BETWEEN 9Z TO 13Z. WINDS SHOULD REMAIN OUT
OF THE NORTH OVERNIGHT...VEERING FROM THE NE DURING THE EARLY
DAYLIGHT HOURS. A WEAK LEE TROF MAY FORM DURING THE AFTERNOON
HOURS...SUPPORTING A LIGHT SOUTH WIND. SKY WILL REMAIN GENERALLY
CLEAR..WITH FEW CIRRUS.

AS OF 640 PM...THE FORECAST REMAINS IN GOOD SHAPE. I WILL ISSUE A
SLIGHT UPDATE FOR HOURLY TEMPS/DWPTS/SKY.

AS OF 230 PM EDT SATURDAY...AN H5 TROF AXIS CONTINUES TO ADVECT
EAST OF THE FCST AREA THIS AFTERNOON YIELDING DEEP/MODEST NW FLOW.
AT THE SURFACE...DRY HIGH PRESSURE CONTINUES TO BUILD OUT OF
CANADA INTO THE GREAT LAKES...EVENTUALLY SLIDING EAST OF THE
APPALACHIANS THROUGH THE OVERNIGHT HOURS INTO SUNDAY MORNING.
WITH THAT...LLV FLOW WILL GRADUALLY VEER NORTHEAST POSSIBLY SETTING
UP OUT OF THE EAST/SOUTHEAST BY EARLY SUNDAY AFTERNOON BENEATH
BUILDING HEIGHTS ALOFT THANKS TO AN INTRUDING SHORTWAVE RIDGE.
GUIDANCE TIME HEIGHT CHARTS ILLUSTRATE THE DEPTH OF THE DRY AIR
THROUGH THE NEAR TERM...WITH THE EXCEPTION OF THE LLVS WHERE RH
REMAINS A BIT ELEVATED.  THUS...THINK THAT SKIES WILL REMAIN PARTLY
CLOUDY THIS AFTERNOON AS CU PREVAILS AHEAD OF SUNSET...EVENTUALLY
GIVING WAY TO MOSTLY CLEAR SKIES OVERNIGHT.  SUNDAY LOOKS TO BE A
FAIRLY NICE SPRING DAY WITH ABOVE NORMAL TEMPS UNDER SUNNY SKIES.
WINDS ON SUNDAY LOOK TO BE RELAXED AS COMPARED TO TODAY THANKS TO
A WEAKENED PRESSURE GRADIENT.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AT 230 PM SATURDAY...ON SUNDAY EVENING AN UPPER RIDGE WILL BE OVER
THE EASTERN USA...AND ANOTHER UPPER TROUGH WILL BE OVER THE PLAINS.
THE UPPER PATTERN PROGRESSES AND DEAMPLIFIES SUCH THAT BY MONDAY THE
NEARLY ZONAL FLOW EXTENDS ACROSS THE SOUTHERN TIER OF STATES. BY
TUESDAY MORNING AND UPPER TROUGH AMPLIFIES OVER THE INTER MOUNTAIN
WEST...AND A RIDGE AMPLIFIES DOWNSTREAM BETWEEN THE PLAINS AND THE
MS RIVER VALLEY.

AT THE SURFACE...ON SUNDAY EVENING DRY HIGH PRESSURE BE OFF THE
EAST COAST...WHILE A COLD FRONT WILL BE CROSSING THE PLAINS. THE
NORTHERN PORTION OF THE FRONT PROGRESSES...WHILE THE SOUTHERN
PORTIONS SLOWS...SUCH THAT BY TUESDAY A SLOW MOVING COLD FRONT WILL
BE TO OUR NORTH OVER THE OH AND POTOMAC RIVER VALLEYS...AND THE
SLOW MOVING COLD FRONT WILL REMAIN IN TX. MOIST INFLOW AHEAD OF THE
COLD FRONT WILL BE CONCENTRATED MAINLY OVER THE MS RIVER VALLEY...
ALTHOUGH ENOUGH MAY BE PRESENT TO SUPPORT PRECIPITATION OVER OUR
AREA...MAINLY IN THE MOUNTAINS ON TUESDAY. INSTABILITY APPEARS TO
BE RATHER LIMITED AT THIS TIME. TEMPERATURES WILL RUN ABOVE NORMAL
UNDER THE UPPER RIDGE.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AT 230 PM SATURDAY...ON TUESDAY EVENING AN UPPER RIDGE WILL BE OVER
HE MS RIVER VALLEY...WITH WEAK TROUGHING TO THE EAST AND WEST. THE
PATTERN DEAMPLIFIES SUCH THAT BY THURSDAY ZONAL FLOW EXISTS ACROSS
THE SOUTHERN TIER OF THE NATION. BY SATURDAY ANOTHER RIDGE AMPLIFIES
OVER THE MS RIVER VALLEY...WITH TROUGHS AMPLIFYING OFF THE EAST
COAST AND OVER THE WESTERN USA.

AT THE SURFACE...A COLD FRONT WILL MOVES TROUGH ALONG THE EAST COAST
TUESDAY NIGHT...STALLING NEAR INTERSTATE 40 BY WEDNESDAY MORNING...
WHILE MOIST GULF INFLOW AHEAD OF A COLD FRONT PERSISTS OVER THE
LOWER MS RIVER VALLEY AHEAD OF A COLD FRONT IN TX. THE EASTERN FRONT
MOVES NORTH ON THURSDAY...WHILE THE WESTERN FRONT REACHES THE MS
RIVER VALLEY....AND A DECREASING PRESSURE GRADIENT DECREASES GULF
INFLOW AS IT SPREAD EAST TO THE SOUTHERN APPALACHIANS. BY FRIDAY
MORNING THE COLD FRONT REACHES THE SOUTHERN APPALACHIANS...BUT A
WEAKENING PRESSURE GRADIENT AHEAD THE FRONT REDUCED MOIST INFLOW
INTO OUR AREA. THE FRONT DROPS WELL SOUTH OF OUR AREA ON SATURDAY...
WHILE HIGH PRESSURE SPREADS SOUTH OVER THE SOUTHERN APPALACHIANS. IT
REMAINS UNCLEAR WHETHER MOISTURE WILL REMAIN NORTH OF THE FRONT TO
ALLOW LIGHT PRECIPITATION TO PERSIST ON SATURDAY. TEMPERATURES WILL
RUN ABOVE NORMAL...COOLING SLIGHTLY BEHIND THE COLD FRONT.

&&

.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
AT KCLT AND ELSEWHERE...VFR EAST OF THE MTNS. SFC HIGH PRESSURE
CENTERED OVER THE GREAT LAKES WILL BUILD OVER THE WESTERN CAROLINAS
THROUGH SUNDAY MORNING. MTN VALLEY WINDS MAY BECOME CALM DURING THE
PRE DAWN HOURS...FAVORING THE DEVELOPMENT OF VALLEY FOG BETWEEN 9Z
TO 13Z. WINDS SHOULD REMAIN OUT OF THE NORTH OVERNIGHT...VEERING
FROM THE NE DURING THE EARLY DAYLIGHT HOURS. A WEAK LEE TROF MAY
FORM DURING THE AFTERNOON HOURS...SUPPORTING A LIGHT SOUTH WIND. SKY
WILL REMAIN GENERALLY CLEAR..WITH FEW CIRRUS.

OUTLOOK...HIGH PRESSURE AND MOSTLY VFR CONDITIONS WILL PERSIST INTO
MONDAY. PRECIPITATION CHANCES WILL START TO INCREASE ON TUESDAY.

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  83%     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 SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JPT
NEAR TERM...NED
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...NED



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