FXUS62 KGSP 252006
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
305 PM EST FRI DEC 25 2009
.SYNOPSIS...
WEAK HIGH PRESSURE WILL BUILD ACROSS THE SOUTHEAST STATES THROUGH
THE WEEKEND WHILE A LARGE UPPER LEVEL TROUGH CROSSES OVERHEAD. A
STRONG UPPER LEVEL RIDGE WILL THEN BRING IN MUCH COOLER HIGH
PRESSURE MONDAY AND DROP TEMPERATURES BLOW NORMAL THROUGH THE MIDDLE
OF NEXT WEEK.
&&
.NEAR TERM /THROUGH SATURDAY/...
SOLID PCPN SHIELD WILL CONTINUE MOVING DOWNSTREAM OF THE EASTERN CWFA
THROUGH LATE AFTERNOON. LINGERING LOCALIZED EXCESSIVE RUNOFF FROM
HEAVY RAINFALL WILL CONTINUE...AND PLAN ON LETTING FLASH FLOOD WATCH
EXPIRE AS SCHEDULE...BUT LONGER TERM AREAL FLOOD WARNINGS REMAIN IN
EFFECT INTO THE EVENING WITH SVRL MAINSTEM RIVER FLOOD WARNINGS IN
EFFECT THROUGH SATURDAY.
LOWER OVC ACRS THE FTHLS/PIEDMONT WITHIN LINGERING WEAK WEDGE SHOULD
EVENTUALLY SCOUR...BUT TIMING REMAINS UNCERTAIN...ESPECIALLY AS ANY
MIXING LOOKS TO LIMITED WITHIN THE WEAK FLOW AND HEADING INTO THE
NIGHTTIME HOURS. AS DRYING ALOFT CONTINUES...AREAS OF FOG MAY ALSO
DEVELOP.
WITH TEMPERATURES EXPECTED TO FALL TO FREEZING AND BELOW BY EARLY
SATURDAY MORNING...ANY WATER LINGERING ON ROADS WILL FREEZE. THE
GREATEST THREAT IS ACRS THE NC MTNS/FTHLS WHERE ICE ACCUMULATED
EARLIER...SNOWMELT CONTINUES AND TEMPERATURES WILL BE THE LOWEST.
WILL PLAN ON ISSUED A WINTER WX ADVISORY FOR BLACK ICE FOR THESE
AREAS.
THE FA TO REMAIN WITHIN DEEP MID/UPPER LEVEL CYCLONIC FLOW ON
SATURDAY...BUT WEAK SFC RIDGING AND THE PRESENCE OF DEEP DRYING
TO RESULT IN A QUICK RETURN TO FAIR WX CONDITIONS AND MAX TEMPS
A LITTLE ABOVE CLIMO.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
AS OF 250 PM FRI...AN INTENSE UPPER LOW WILL FINALLY GET PICKED
UP BY THE WESTERLIES SUNDAY NIGHT AND MONDAY. WITH A WEAK SURFACE
RIDGE AND A DRY AIRMASS IN PLACE...THE WEATHER WILL BE FAIR SAT
NGHT AND SUNDAY. AS THE AXIS OF THE UPPER LOW SWINGS JUST NORTH OF
THE REGION OVERNIGHT...NORTHWEST FLOW...COLDER TEMPERATURES AND
CYCLONIC CURVATURE WILL BEGIN TO AFFECT THE MOUNTAINS. THE
RESULTING UPSLOPE FLOW SHOULD YIELD GOOD SNOWSHOWER COVERAGE ALONG
THE TN LINE. THE HEIGHTS ARE A LITTLE HIGH...BUT WITH A MOIST
LAYER EXTENDING UP TO AROUND 750 MB AND H8 TEMPS FALLING TO AROUND
-10 DEG C...THE SNOWSHOWER ACTIVITY SHOULD BE VIGOROUS ENOUGH TO
CAUSE ACCUMULATING SNOWFALL. THE PREVIOUS SHIFT HAD 1 TO 2 INCHES
OF SNOW...AND MY NUMBERS ARE SIMILAR...WITH THE HIGHEST TOTALS
ACROSS THE NRN MTNS AND ALONG THE IMMEDIATE TN LINE DOWN ACROSS
THE CENTRAL AND SOUTHWEST MTNS.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 245 PM FRIDAY...H5 SHRTWV MOVES E OF AREA MON NIGHT. LOW LVL
MOISTURE IN NW FLOW OVER NC MTNS ALONG TN BORDER WILL ALLOW SNOW
SHWRS TO LINGER THRU THE DAY MON BEFORE ENDING MON NIGHT. H5 RIDGE
BUILDS OVER REGION TUE AND SFC HIGH RIDGES DOWN OVER CWA WITH COOL
NE FLOW DEVELOPING. THERE SHOULD BE ENOUGH SUNSHINE FOR TEMPS TO
WARM TO WITHIN A COUPLE DEG OF AVG TUE AFTN. UPPER RIDGE MOVES E AND
NEXT S STREAM SHORTWAVE APPROACHES THE AREA FROM THE SW TUE
NIGHT-WED. MODELS CONTINUE TO STRUGGLE WITH RUN TO RUN CONTINUITY
AND DIVERGE FROM EACH OTHERS SOLUTIONS REGARDING THIS SYSTEM. IN ANY
CASE THERE IS ENOUGH AGREEMENT TO SEE THAT AS SFC HIGH PRESSURE
RIDGES INTO THE CWA FROM THE NE WED...A SFC LOW DEVELOPS IN THE N
GULF AND TRACKS ENE INTO N FL BEFORE WEAKENING AND REDEVELOPING OFF
THE CAROLINA COAST IN WHAT APPEARS TO BE A PSBL MILLER B SCENARIO.
THE S EXTENT OF THIS TRACK INDICATES A RAIN-SNOW MIX BUT KEPT POPS
IN THE CHC RANGE ATTM DUE TO RELATIVELY HIGH DEGREE OF UNCERTAINTY
REGARDING DETAILS AND TIMING.
&&
.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
AT KCLT...WILL HANG MY HAT ON THE NAM/S HANDLING OF SENSIBLE
WX BEHIND DEPARTING PCPN SHIELD...WITHIN LINGER WEAK DAMMING
REGIME. USING NAM GUIDANCE...WOULD EXPECT NNE WINDS TO GRADUALLY
BACK AND WEAKEN INTO THIS EVENING...WITH NO CIG IMPROVEMENT. IT IS
QUESTIONABLE WHETHER ENUF WIND WILL LINGER TO PREVENT WIDESPREAD
FOG DEVELOPMENT...ESPECIALLY AS THE NIGHT WEARS ON AND DRYING
ABOVE THE SFC INCREASES. EXPECT A RETURN TO VFR BY MID-MORNING
SATURDAY AS WINDS BECOME WSW.
ELSEWHERE ACRS THE FA...AGAIN WILL BASE THE FORECAST ON THE
LINGERING WEAK WEDGE CONDITIONS PROGGED BY THE NAM. EXPECTING
LOW CIGS TO CONTINUE INTO TONIGHT WITH THE PROBABILITY THAT FOG
BECOMES WIDESPREAD AS DRYING ABOVE THE SFC INCREASES. EXPECTING
VFR CONDITIONS TO RETURN BY MID-MORNING.
OUTLOOK...VFR CONDITIONS EXPECTED SATURDAY THRU TUE. MOISTURE AHEAD
OF A WEAK COLD FRONT WILL RETURN TO THE FA ON WEDNESDAY.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 9 AM EST
SATURDAY FOR NCZ033-048>053-058-059-062>065-501>510.
FLASH FLOOD WATCH UNTIL 4 PM EST THIS AFTERNOON FOR NCZ035>037-
056-057-069>072-082.
SC...FLASH FLOOD WATCH UNTIL 4 PM EST THIS AFTERNOON FOR SCZ009-014.
&&
$$
SYNOPSIS...SBK
NEAR TERM...CSH
SHORT TERM...MCAVOY
LONG TERM...RB
AVIATION...CSH/JAT
