GSP Afternoon discussion

[Dan]

GSP has IMO some of the best forecasters in the nation. Once again a very in-depth discussion of tonight's storm...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
237 PM EST SAT DEC 25 2004

.SHORT TERM (TONIGHT THROUGH TUESDAY)...
INTERESTING 24 HOURS SETTING UP FOR SOUTHERN PART OF OUR FORECAST
AREA...AS CYCLOGENESIS UNDERWAY IN THE GULF OF MEXICO WILL PROVIDE A
GLANCING BLOW OF WINTRY PRECIPITATION TO THE SOUTHERN AND SOUTHEAST
PORTION LATER TONIGHT AND EARLY SUNDAY AS INCIPIENT LOW MOVES
NORTHEAST OFF THE SOUTHEAST COAST. WE RECENTLY UPDATED THE FORECAST
TO ISSUE A WINTER WEATHER ADVISORY FOR OUR FRINGE BORDER COUNTIES
FROM ELBERT GEORGIA TO UNION NORTH CAROLINA...AND FOR NOW WE
WILL HOLD AT THAT...AND NOT UPGRADE TO A WARNING FOR ANY OF THE
ADVISORY AREA. 12Z MODEL RUNS AND LATEST NCEP GUIDANCE...HOWEVER...
SUGGEST IT WILL BE A CLOSE CALL. AND THE SYNOPTIC SETUP IS ONE
WHICH FAVORS A TIGHT PRECIPITATION GRADIENT ON THE NORTHWEST
EDGE...WHICH LINES UP WITH OUR BORDERS WITH THE ATLANTA...COLUMBIA
AND RALEIGH FORECAST OFFICES.

MORNING OBSERVED SOUNDINGS...AND CURRENT LAPS SOUNDINGS...INDICATE
LOW LEVELS VERY DRY INITIALLY. WARM ADVECTION EXPECTED TO BEGIN
ACROSS OUR SOUTHERN TIER ZONES LATE TONIGHT AS SURFACE WAVE MAKES
ITS CLOSEST APPROACH. MODELS INITIALIZED POORLY WITH STRENGTH OF
SURFACE WAVE...SUGGESTING GREATER POTENTIAL FOR A MORE NORTHERLY
DISTRIBUTION OF PRECIPITATION. SURFACE WAVE AND ATTENDANT UPPER
TROF EXPECTED TO SWING BY IN THE PREDAWN HOURS...WHEN UPPER
DIVERGENCE/DEFORMATION ZONE AND WARM ADVECTION MAXIMIZED. BIG
QUESTION IS HOW FAR NORTH WILL MEASURABLE PRECIPITATION FALL...GIVEN
THE QUANTITY OF DRY AIR THAT MUST BE OVERCOME AND BREVITY OF
PRECIPITAITON TIMING WINDOW. AT THIS JUNCTURE...APPEARS
PRECIPITATION TIME WILL BE 06Z TO 12Z ELBERT/ABBEVILLE...09Z TO 15Z
CHESTER TO UNION NORTH CAROLINA...AND GREENWOOD/SOUTHEAST
LAURENS/SOUTHEAST UNION SOUTH CAROLINA WITH THE LONGEST
PRECIPITATION POTENTIAL.

THERMAL PROFILES ON FORECAST SOUNDINGS SHOW POTENTIAL FOR MOSTLY
SNOW WITH THIS EVENT...BUT ETA AND ITS HIGHER RESOLUTION SISTERS
INSISTENT ON WARM NOSE THAT COULD INITIATE A PERIOD OF
SLEET/FREEZING RAIN. WE DO NOT BELIEVE THE WARM NOSE IS
SUFFICIENTLY STRONG ENOUGH FOR MUCH FREEZING RAIN...BUT WILL MENTION
SNOW/SLEET...AND A SLIGHT CHANCE OF FREEZING RAIN. CHANCES OF RAIN
WILL BE PUT AT 60% FOR THE ADVISORY COUNTIES...WITH TIGHT POP
INTER-COUNTY GRADIENTS; THIS COULD BE A SITUATION WHERE JUST A FEW
MILES MAKES A BIG DIFFERENCE IN HOW MUCH PRECIPITATION OCCURS. TO
THE NORTH...CHANCES OF SNOW SHOWERS/SLEET FOR THE REST OF THE
UPSTATE FOOTHILLS/PIEDMONT...NORTH TO THE CHARLOTTE METRO AREA...BUT
DRIER AIR MORE ENTRENCHED IN THESE LOCATIONS AND THEY MAY ACTUALLY
BE TOO FAR NORTH FOR THE WARM ADVECTION MOISTURE TO INVADE THE DRIER
LOW LEVELS THAT WILL BE IN PLACE. SLIGHT CHANCES TO NO CHANCES OF
PRECIPITATION FOR MOST AREAS NORTH AND WEST OF INTERSTATE 85.

WE WILL PLAN TO PAINT 2 TO 3 INCH SNOWFALL AMOUNTS FOR SMALL
SLIVERS OF GREENWOOD...LAURENS...AND CHESTER COUNTIES IN SOUTH
CAROLINA...AND FOR EXTREME SOUTHEAST UNION NORTH CAROLINA; MOST OF
THE ADVISORY AREA WILL GET AN INCH OR TWO MENTIONED. ACCUMULATIONS
PROJECTED TO DROP OFF RAPIDLY FROM THERE...TO NO MORE THAN A DUSTING
FOR THE GREENVILLE/SPARTANBURG METRO AREA. MOST OF THE SIGNIFICANT
SNOWFALL WILL BE TO THE EAST OF OUR FORECAST AREA.

WITH THE DEVELOPING CYCLONE AND UPPER TROF SWINGING ACROSS TONITE...
WE WILL INDICATE NORTH TO NORTHEAST WINDS 10 TO 20 MPH SOUTH AND
EAST. TEMPERATURES TEENS NORTH TO UPPER 20S/NEAR 30 SOUTH.

PRECIPITATION SHIELD SHOULD ERODE FROM THE WEST AND SOUTH SUNDAY
MORNING...AND DEPENDENT ON THE VERIFICATION OF ANY WARM NOSE...WE
COULD SEE A BRIEF PERIOD OF FREEZING RAIN BEFORE EVENT ENDS FOR
GOOD SOUTH AND EAST. FORECAST SOUNDINGS FOR A FEW OF THE ADVISORY
COUNTIES SUGGEST THE EVENT COULD END AS RAIN. SURFACE WAVE
PROJECTED TO CONTINUE MOVING OUT TO SEA...CUTTING OFF
MOISTURE FROM OUR REGION. DECREASING CLOUDS STILL LOOK GOOD FOR THE
AFTERNOON. WE TONED DOWN HIGH TEMPERATURES FOR SUNDAY...40 TO 45 MOST
AREAS.