FXUS62 KGSP 021538
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1038 AM EST WED DEC 2 2009
.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL CONTINUE TO RIDE NORTHEASTWARD AND INTO
THE OHIO VALLEY TODAY AS A COLD FRONT MOVES TOWARD THE EAST COAST.
HIGH PRESSURE WILL NOSE IN FROM THE WEST THROUGH FRIDAY...BEFORE AN
UPPER LEVEL SYSTEM AFFECTS THE REGION ON SATURDAY. BEHIND THIS
SYSTEM...HIGH PRESSURE WILL RETURN TO THE FORECAST AREA AND REMAIN
IN PLACE THROUGH EARLY NEXT WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
EXCEPT FOR THE OBSERVED RAINFALL AMOUNTS...WEATHER TRENDS ARE
FOLLOWING THE FCST MOSTLY AS EXPECTED. WIDESPREAD MODERATE WITH
PATCHES OF HEAVY RAINFALL CONTINUES TO SPREAD BACK INTO THE AREA
THIS MORNING. A SECOND LARGE AREA OF THIS RAINFALL IS TO OUR
SOUTHWEST AND HEADING THIS WAY. ALTHOUGH RAINFALL AMOUNTS HAVE NOT
BEEN EXCESSIVE SO FAR...THE CUMULATIVE AFFECT OF THE NEXT ROUND OF
RAINFALL COULD STILL PRODUCE FLASH FLOODING. THEREFORE...WILL KEEP
THE WATCH IN PLACE. THE HIGHEST H85 WINDS WERE STILL JUST TO OUR
WEST...BUT HEADING THIS WAY AS WELL. EXPECT WINDS TO INCREASE ACROSS
THE HIGHER ELEVATIONS DURING THE AFTERNOON...SO WIND ADV WILL REMAIN
IN PLACE AS WELL. NAM/SREF STILL SUGGEST THE COASTAL WARM FRONT WILL
MOVE INTO THE SOUTHERN CWFA THIS AFTERNOON AS A LOW MOVES ALONG THE
FRONT. POSITIVE CAPE VALUES DEVELOP WITH THE FRONT...AND THIS
COMBINED WITH THE VERY STRONG SHEAR IN PLACE...COULD STILL PRODUCE
SOME SEVERE STORMS. MADE SOME MINOR ADJUSTMENTS TO FCST VALUES DUE TO
CURRENT CONDITIONS...BUT LITTLE CHANGE IN THE OVERALL FCST.
AS FOR TONIGHT...EXPECT PRECIP TO LIFT NE WITH THE SHORT WAVE IN THE
EVENING...FOLLOWED BY SOME WRAP AROUND SHOWER CHANCES OVER THE MTNS.
KEPT MIN TEMPS ABOVE FREEZING WHICH KEEPS THE PRECIP ALL LIQUID.
AREAS EAST OF THE MTNS SHOULD SEE PARTIAL CLEARING BY DAYBREAK
THURSDAY.
&&
.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
AS OF 350 AM WEDNESDAY...SHORT RANGE MODELS REMAIN IN REASONABLE
AGREEMENT ON THURSDAY. LLVL WRAP AROUND MOISTURE WILL REMAIN BANKED
ACROSS THE TN BORDER COUNTIES DURING THE DAY ON THURSDAY. ONLY FEW
TO ISO SHRA MAY DEVELOP ACROSS THE UPSLOPE AREAS OF NC INTO THURSDAY
AFTERNOON. I WILL REDUCE POPS TO SCHC GIVEN WEAK WEST WINDS AND
LIMITED MOISTURE. HIGH TEMPERATURES ARE FORECAST TO REACH NEAR
NORMAL LEVELS ACROSS THE CWA.
FRIDAY...SFC HIGH PRESSURE WILL BUILD ACROSS THE FORECAST AREA FROM
THE WEST. ALOFT...L/W TROF AXIS IS EXPECTED TO SWEEP ACROSS THE
MIDDLE CONUS...RESULTING IN FALLING HEIGHTS ACROSS THE EAST.
THICKNESSES SHOULD REMAIN FAIRLY COOL WITH INCREASING CLOUD COVER
THROUGH THE DAY. LOW TEMPERATURES ARE FORECAST TO FALL CLOSE TO
NORMAL...HOWEVER...HIGH TEMPERATURES WILL LIKELY REMAIN 3-6 DEGREES
BELOW NORMAL.
THE LONGWAVE TROF AXIS WILL PUSH EAST ACROSS THE MISSISSIPPI RIVER
VALLEY FRIDAY NIGHT. A POWERFUL JET STREAKS NORTHWARD ON THE EAST
HALF OF THE TROF LATE FRI NIGHT...PROVIDING A LARGE REGION OF UPPER
DIVERGENCE ACROSS THE SOUTHEAST BY 12Z SAT. LIFT DEEPENS ACROSS THE
CWA 15Z-21Z SATURDAY AS H7-H5 FRONTOGENESIS ON THE WESTERN SIDE OF
COASTAL LOW PRESSURE PIVOTS OVER THE WESTERN CAROLINAS. FORECAST
SOUNDINGS INDICATE THAT DEEP MOISTURE WILL ARRIVE BETWEEN 9Z-12Z SAT
AND REMAIN INTO SATURDAY EVENING. IN ADDITION...MODELS INDICATE THAT
A SMALL REGION -EPV MAY DEVELOP ACROSS THE WESTERN CAROLINAS ALONG
AND AHEAD OF THE H5 TROF SAT AFTERNOON.
IT CERTAINLY APPEARS THAT MEASURABLE PRECIPITATION WILL OCCUR ACROSS
THE CWA FROM THIS EVENT. THE MAIN CHALLENGE WILL REMAIN WITH THE
P-TYPE FORECAST. USING A BLEND OF SREF...GFS40 LLVL TEMPS...I WILL
FORECAST FREEZING TEMPS ACROSS THE MTNS WITH MID TO U30S EAST OF THE
MTNS BY SUNRISE SAT. HEATING AFTER SUNRISE WILL REMAIN LIMITED BY
PRECIP...THICK CLOUD COVER...AND ONGOING NORTH SFC WINDS. HIGH TEMPS
ARE FORECAST TO RANGE FROM FREEZING ACROSS THE HIGH TERRAIN TO LOW
TO MID 40S EAST OF THE MTNS. PARTIAL THICKNESSES AND THE TOP DOWN
METHOD YIELD MAINLY SN ACROSS THE HIGH ELEVATIONS WITH A MIX IN THE
VALLEYS. AT THIS POINT...PRECIPITATION SHOULD REMAIN RA ACROSS NE
GA...SC...AND EAST OF I-40 ACROSS NC. PRECIP WILL GRADUALLY DECREASE
EARLY SATURDAY EVENING AS THE H5 TROF RIPPLES EAST OF THE CWA. THIS
FORECAST PACKAGE WILL FEATURE SNOWFALL OF 1-3 INCHES ABOVE 3000 FEET
IN ELEVATION...WILL HIGHLIGHT IN THE HWO. SAT NIGHT...SKY COVER WILL
DECREASE WITH THE ARRIVAL OF HIGH PRESSURE. FRESH CAA AND LIGHT
WINDS SHOULD RESULT IN COLD LOW TEMPS. BY 12Z SUN...TEMPS ARE
FORECAST TO RANGE FROM THE L20S ACROSS THE MTNS WITH MID 20S TO 30
DEGREES EAST OF THE MTNS. IN FACT...IT APPEARS THAT TEMPS WILL FALL
BELOW FREEZING ACROSS THE MTNS LATE SAT EVENING. DAMP ROADS AND
ONGOING RUNOFF MAY RESULT IN SIGNIFICANT BLACK ICE SAT NIGHT...PLAN
TO HIGHLIGHT IN THE HWO.
&&
.LONG TERM /SUNDAY THROUGH TUESDAY/...
AS OF 245 AM WEDNESDAY...THE BULK OF THE MEDIUM RANGE WILL BE QUIET
WITH BELOW NORMAL TEMPS. ALOFT...THE PERIOD SUNDAY THROUGH TUESDAY
WILL BE DEFINED BY QUASI ZONAL FLOW WITH SOME AMPLIFICATION OF THE
PATTERN ON TUESDAY AS A TROF BEGINS TO MOVE OUT OF THE FOUR CORNERS
REGION. AT THE SURFACE...HIGH PRESSURE WILL SETTLE IN ACROSS THE FA
ON SUNDAY AND LARGELY REMAIN IN PLACE THROUGH TUESDAY. THE VARIOUS
MODEL SOLUTIONS DO DEPICT SOME MOISTENING FROM THE WEST BY TUESDAY
AFTERNOON...AND I DO CONTINUE TO ADVERTISE SLIGHT CHANCE POPS DURING
THIS PERIOD AS A COMPROMISE BETWEEN THE ECMWF AND THE GFS. OVERALL
TEMPS WILL REMAIN BELOW CLIMO AS COOL LOW LEVEL NERLY FLOW WILL
DOMINATE THE PERIOD AND UPPER HEIGHTS REMAIN LARGELY UNCHANGED IN
THE QUASI ZONAL FLOW ALOFT. THIS RESULTS IN TEMPS ABOUT 3-5 DEGREES
BELOW CLIMO THROUGH EARLY NEXT WEEK.
&&
.AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT AND ELSEWHERE...FIRST BATCH OF RAIN WORKING ACROSS THE
WESTERN CAROLINAS IS GRADUALLY BRINGING THE CEILING AND VISIBILITY
DOWN INTO THE MVFR RANGE WHILE ESTABLISHING THE COLD AIR DAMMING
WEDGE. EXPECT CEILING TO CONTINUE FALLING INTO IFR RANGE THROUGH MID
MORNING...WHERE IT SHOULD STAY FOR SEVERAL HOURS INTO THE AFTERNOON.
SOME LOW IFR IS NOT OUT OF THE QUESTION...ESPECIALLY IN THE MORE
INTENSE SHOWERS. THE PRIMARY CONCERN IS LOW LEVEL WIND SHEAR AS AN
INTENSE LOW LEVEL JET TRANSLATES ACROSS THE REGION THIS MORNING...SO
ALL TAFS FEATURE SOME MENTION OF 45-50KT WIND FROM SE AT 2K FEET.
ALTHOUGH THE MODEL DATA DOES NOT SHOW IT...WE SHOULD SEE A BRIEF
LULL IN THE PRECIP THIS MORNING BASED ON RADAR TRENDS SEEN OVER
GEORGIA. THIS MIGHT IMPROVE THE VISIBILITY A BIT...BUT THINK CEILING
WILL REMAIN IFR. THE UPPER SYSTEM WILL MOVE PAST LATE IN THE
AFTERNOON WHICH SHOULD BREAK UP THE LOW CLOUDS AND ALSO BRING THE
POSSIBILITY OF A LINE OF THUNDERSTORMS. WENT WITH A PERIOD OF MVFR
CEILING FOR A FEW HOURS BEFORE LIFTING IT AS THE DRY SLOT WORKS IN
FROM THE SOUTHWEST IN THE EVENING. CLOUDS SHOULD SCATTER OUT BEHIND
THE FRONT IN THE MID TO LATE EVENING WITH WINDS SHIFTING AROUND TO
THE SOUTHWEST.
OUTLOOK...VFR EXPECTED THURSDAY AND FRIDAY...BUT BRIEF MVFR POSSIBLE
AT KAVL AROUND SUNRISE. ANOTHER PERIOD OF MVFR CONDITIONS IS
POSSIBLE ON SATURDAY AS AN UPPER DISTURBANCE MOVES THROUGH...WHICH
COULD RESULT IN SOME LIGHT SNOW OVER THE MTNS.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...FLASH FLOOD WATCH THROUGH THIS EVENING FOR GAZ010-017-018-026-
028-029.
WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR GAZ010-017.
NC...FLASH FLOOD WATCH THROUGH THIS EVENING FOR NCZ035>037-056-057-
062>065-068>072-082-501>510.
WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR NCZ033-048>053-
058-059-062>065-501-503-505-507-509.
SC...FLASH FLOOD WATCH THROUGH THIS EVENING FOR SCZ001>014-019.
WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR SCZ001>003.
&&
$$
SYNOPSIS...BSH
NEAR TERM...PM/RWH
SHORT TERM...NED
LONG TERM...BSH
AVIATION...PM
