« Back
NWS Peachtree City, Ga » Text Product » GSP Area Forecast Discussion


Printer-friendly Version
Current Version              Previous Versions:   1  2  3  4  5  6  7  8  9  

Area Forecast Discussion

439
FXUS62 KGSP 080244
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1044 PM EDT TUE JUL 7 2015

.SYNOPSIS...
AN LARGE UPPER RIDGE WILL STRENGTHEN AND RETROGRADE OVER THE
SOUTHEAST THROUGH THE WEEKEND. SHOWER AND THUNDERSTORM CHANCES WILL
FAVOR THE AFTERNOON AND EVENING WITH THE BEST CHANCES RESIDING OVER
THE HIGH TERRAIN. A MID LEVEL TROUGH IS EXPECTED TO DIG EAST OF THE
MISSISSIPPI RIVER BY THE MIDDLE OF NEXT WEEK. TEMPERATURES WILL
INCREASE TO ABOVE NORMAL LEVELS.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 1030 PM...HAVE BEEN WATCHING A BROKEN BAND OF SHOWERS/STORMS
MOVING EAST ACROSS THE CUMBERLAND PLATEAU ON KMRX RADAR WITH SOME
INTEREST. SPC MESOANALYSIS SHOWS A TONGUE OF 1000 J/KG OF CAPE AHEAD
OF THE CONVECTION AND OVER THE NE PART OF TN. THIS SHOULD GIVE THE
LINE ENOUGH FUEL TO REACH NW NC BEFORE DYING...AROUND 06Z OR SO.
APOLOGIZE FOR THE LATE UPDATE...BUT THINK IT BEST TO ADD A CHANCE OF
SHOWERS/THUNDERSTORMS TO THE NRN MOUNTAINS IN THE EARLY MORNING
HOURS.

PREVIOUS DISCUSSION...

AT 200 PM EDT TUESDAY...A WEAKENING SHORTWAVE WILL MOVE NORTHEAST AND
AWAY FROM OUR AREA LATE TODAY. AN UPPER LEVEL RIDGE WILL BUILD WEST
FROM THE ATLANTIC TO THE GULF STATES TONIGHT AND WEDNESDAY. THIS
RIDGING WILL RESULT IN THE BULK OF SHORTWAVE ACTIVITY PASSING BY TO
OUR NORTH...REDUCING FORCING OVER OUR AREA.

AT THE SURFACE...A COLD FRONT TO OUR NORTH WILL STALL TO OUR NORTH
OVER THE OH AND POTOMAC RIVER VALLEYS ON WEDNESDAY. MOISTURE
ASSOCIATED WITH THE FRONT IS EXPECTED TO REACH OUR NORTHERN TIER OF
COUNTIES BEFORE DAYBREAK. DESPITE RISING HEIGHTS ALOFT...MODEL
SOUNDINGS SHOW SUBSTANTIAL INSTABILITY BOTH THIS AFTERNOON AND AGAIN
ON WEDNESDAY...WITH PLENTY OF DRY AIR ALOFT FOR EVAPORATIVE
COOLING...AND EVEN SOME MODEST LOW LEVEL SHEAR. CONVECTIVE CHANCES
WILL BE BETTER NORTH AND EAST OF INTERSTATE 85...WHERE MORE MOISTURE
WILL BE AVAILABLE. TEMPERATURES WILL RUN ABOVE NORMAL WITH
INCREASING HEIGHTS ALOFT.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 230 PM TUESDAY...A TYPICAL SUMMERTIME PATTERN CONTINUES THRU
THE SHORT RANGE PERIOD WITH THE SUBTROPICAL BERMUDA ANTICYCLONE IN
PLACE ACROSS THE SERN CONUS KEEPING ANY SHORT WAVES AT BAY TO OUR
WEST AND NORTH. THAT SAID...THE CENTER OF THE ANTICYCLONE DOES
RETROGRADE ON SHORE DURING THE PERIOD...POSSIBLY SETTING UP A
PATTERN CHANGE FOR LATER IN THE FORECAST WITH A BUILDING CENTRAL
CONUS RIDGE AND NORTHEASTERN CONUS TROF.

THE SFC PATTERN IS TYPICAL AS WELL WITH WEAK RIDGING ACROSS THE MTNS
AND A LEE TROF ACROSS THE PIEDMONT...AND ANY SIGNIFICANT FRONTS OR
LOW PRESSURE SYSTEMS OFF TO OUR NORTH. THAT SAID...THE LEE TROF
LOOKS TO BE SETTING UP FARTHER EAST THAN TYPICAL...KEEPING ANY
BETTER FORCING TO THE EAST AS WELL. ALL THIS MEANS ISOLATED TO SCT
DIURNAL CONVECTION ACROSS THE MTNS WITH LITTLE TO NO ACTIVITY ACROSS
THE PIEDMONT...UNLESS THE LEE TROF IS FARTHER WEST. SOME OF THE
GUIDANCE FOR FRIDAY IS HINTING AT BETTER CONVECTIVE CHC OUTSIDE OF
THE MTNS EAST OF I-26 WHERE OUTFLOW BOUNDARIES FROM AN OVERNIGHT MCS
ARE ABLE TO MOVE INTO THE AREA HELPING PROVIDE A TRIGGER. WILL HAVE
TO WAIT AND SEE IF THIS DEVELOPS AS THE LOW LEVEL WLY FLOW IS
CREATING A GENERALLY DRIER PATTERN. ALTHOUGH THE OVERALL CHC OF FOR
SVR STORMS IS LOW...AN ISOLATED SVR STORM IS POSSIBLE...MAINLY
ACROSS THE MTNS.

WITH THE RIDGE IN PLACE...THICKNESSES RISE THRU THE PERIOD PUSHING
TEMPS INTO THE MID 90S OUTSIDE OF THE MTNS AND WELL INTO THE 80S
ACROSS THE MTN VALLEYS. HOWEVER...DEW POINTS WILL BE RELATIVELY LOW
WITH THE WLY FLOW...KEEPING HEAT INDEX VALUES UNDER 100. LOWS IN THE
UPPER 60S TO LOWER 70S EXPECTED OUTSIDE OF THE MTNS...WITH 60S FOR
THE MTN VALLEYS.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
245 PM TUESDAY...MEDIUM RANGE MODELS INDICATE THAT A LARGE H5 RIDGE
WILL REMAIN CENTERED ACROSS THE DEEP SOUTH ON SATURDAY...SLIDING
WEST TO THE SOUTHERN PLAINS BY SUNDAY. THIS WEEKEND...VERY WARM MID
LEVEL TEMPERATURES WILL REMAIN ACROSS THE REGION...RESULTING IN VERY
LITTLE INSTABILITY. GIVEN THE MID LEVEL RIDGING...WEAK SFC
FLOW...AND UNFAVORABLE THERMAL AND MOISTURE PROFILES...I WILL KEEP
POPS LIMITED TO CHC ALONG THE RIDGES WITH SCHC POPS EAST.
TEMPERATURES SHOULD RANGE 3 TO 5 DEGREES ABOVE NORMAL.

MONDAY AND TUESDAY...THE H5 RIDGE IS FORECAST TO AMPLIFY ACROSS THE
GREAT PLAINS AS A LONGWAVE TROF DIGS ACROSS THE APPALACHIANS. MEDIUM
RANGE MODELS GENERALLY SHOW A ACTIVE PERIOD OF MCS ACTIVITY ACROSS
THE OHIO RIVER VALLEYS AND MID ATLANTIC REGION. HOWEVER...THE
WESTERN CAROLINAS AND NE GA SHOULD REMAIN WELL SOUTH THE MCS TRACKS.
HOWEVER...FALLING HEIGHTS ALOFT AND COOLING MID LEVEL TEMPERATURES
SHOULD YIELD GREATER INSTABILITY ACROSS THE CWA. I WILL INDICATE A
MID DAY INCREASE IN POPS ACROSS THE MTNS...SPREADING EAST ACROSS THE
FOOTHILLS AND PIEDMONT DURING THE AFTERNOON. HIGH TEMPERATURES
SHOULD CONTINUE TO RANGE 3 TO 4 DEGREES ABOVE NORMAL.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...VFR THRU THE PERIOD. EXPECT A LIGHT SW WIND OVERNIGHT WITH
SOME THIN CIRRUS. ON WEDNESDAY...CONVECTIVE CLOUDS SHOULD ONCE AGAIN
DEVELOP WITH SOME HEATING DURING THE LATE MORNING HOURS. THE NAM
SEEMS OVERLY AGGRESSIVE WITH DEVELOPING SHOWERS/STORMS ON THE BLUE
RIDGE IN EARLY AFTERNOON AND THEN CARRYING THEM ACROSS THE WRN
PIEDMONT IN THE EARLY EVENING WEDNESDAY...LIKE THERE IS SOME UPSCALE
GROWTH. FCST SOUNDINGS DO NOT LOOK ALL THAT GREAT AND THINK THE
MODEL IS OVERDONE. PREFER SOMETHING MORE LIKE THE SPC 4KM WRF THAT
SHOWS THE PIEDMONT REMAINING DRY...LIKE TODAY...SO HAVE LEFT ANY
MENTION OUT OF THE TAF.

ELSEWHERE...AN ISOLATED PATCH OF SHOWERS/STORMS OVER THE SRN
FOOTHILLS/BLUE RIDGE OF NC SHOULD DISSIPATE WITH LOSS OF HEATING
BEFORE IT REACHES ANY TAF SITES. OVERNIGHT...WITH JUST SOME THIN
CIRRUS...THINK MTN VALLEYS WILL ONCE AGAIN GET SOME FOG. WENT
PERSISTENT AT KAVL THINKING THAT TEMPORARY IFR IS A DISTINCT
POSSIBILITY...BUT MVFR A GOOD BET. KAND ALSO A DECENT BET TO SEE A
BRIEF PERIOD OF MVFR FOG AROUND DAYBREAK. OTHERWISE...SCT CU WITH A
SW WIND ON WEDNESDAY. BEST CHANCE...30 PCT OR SO...FOR CONVECTION
WILL BE NEAR THE MTNS AND FOOTHILLS...THUS INDICATED AT KAVL/KHKY.

OUTLOOK...ISOLATED TO SCATTERED AFTN/EVENING THUNDERSTORMS ARE
EXPECTED OVER THE AREA THRU THIS WEEKEND...MAINLY IN THE MTNS...WITH
ASSOCIATED RESTRICTIONS UNDER THE HEAVIEST SHOWERS. LOW CLOUDS AND
FOG COULD DEVELOP IN THE MORNING AT PLACES THAT HAVE SHOWER ACTIVITY
THE DAY BEFORE.

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...NONE.
SC...NONE.

&&

$$
SYNOPSIS...NED
NEAR TERM...JAT/PM
SHORT TERM...RWH
LONG TERM...NED
AVIATION...PM



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