FXUS64 KMRX 040843
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
343 AM EST FRI DEC 4 2009
.SHORT TERM (TODAY THROUGH SATURDAY)...
THE FIRST ACCUMULATING SNOW EVENT OF THE SEASON APPEARS TO BE TAKING
SHAPE OVER THE NEXT 36 HOURS. A POSITIVELY TILTED TROUGH AXIS OVER
THE PLAINS THIS MORNING WILL ROTATE SOUTHEAST...INDUCING
CYCLOGENESIS NEAR THE GA/SC COASTLINE. THE NAM AND THE GFS AGREE
THAT THE LARGE SCALE FORCING AS INDICATED BY Q-VECTOR CONVERGENCE
WILL BE CENTERED OVER OUR AREA AT 12Z SAT...AND BOTH MODELS HAVE
SHOWN VERY GOOD RUN-TO-RUN CONSISTENCY WITH THIS...ALTHOUGH THE TWO
MODELS HAVE SOME TIMING DIFFERENCES. CROSS SECTIONS OF AGEOSTROPHIC
CIRCULATIONS IN THE ENTRANCE REGION OF THE UPPER JET SHOW GOOD LIFT
IN THE EASTERN PORTIONS OF OUR AREA. AS THE LIFT APPEARS TO BE
CONNECTED WITH LARGE SCALE FORCING
MECHANISMS...CONFIDENCE IS FAIRLY HIGH. HOWEVER THERE ARE SOME
IMPORTANT FEATURES LACKING FOR A GOOD SNOWFALL...SUCH AS MIDLEVEL
FRONTOGENESIS...LOW LEVEL CONVERGENCE...SURFACE TEMPS WELL BELOW
FREEZING...AND A TROWAL. SO WHILE THERE SHOULD BE STEADY SNOW...IT
SHOULD NOT BE HEAVY. DAYTIME TEMPERATURES SATURDAY WILL BE
MARGINALLY NEAR FREEZING...WHICH MAY HELP LIMIT
ACCUMULATIONS...ESPECIALLY IN THE VALLEY.
THE PREVIOUS FORECAST OF 3-6 INCHES IN THE MOUNTAINS APPEARS
REASONABLE AND WILL KEEP THAT GOING IN THE WATCH. SINCE THE ONSET OF
SNOW WILL BE AFTER MIDNIGHT...LATE SECOND PERIOD...WILL NOT MAKE ANY
CHANGES OR UPGRADES TO THE WATCH. LOCATIONS OUTSIDE THE MOUNTAINS IN
NE TN AND SW VA COULD SEE 1-3 INCHES...BUT FOR NOW WILL HOLD OFF ON
AN ADVISORY.
.LONG TERM (SATURDAY NIGHT THROUGH THURSDAY)...THE FRONT MOVES OUT
OF THE REGION BY SATURDAY NIGHT. WILL KEEP ONLY SLIGHT CHANCE POPS
FOR THE EASTERN PORTIONS OF THE CWA DURING THE EVENING HOURS.
ADDITIONAL SNOWFALL WILL BE MINIMAL. HIGH PRESSURE BUILDS IN
BRINGING DRY WEATHER FOR SUNDAY. A WEAK FRONT TRACKS THROUGH THE
AREA ON MONDAY. MOISTURE IS LIMITED SO KEPT ONLY SLIGHT CHANCE POPS
FOR MONDAY. WITH COLD AIR LINGERING...SHOULD SEE SNOW RETURN ACROSS
MAINLY THE HIGHER ELEVATIONS ON MONDAY NIGHT. ANOTHER FRONT ENTERS
THE REGION ON TUESDAY AND LINGERS INTO WEDNESDAY. WITH DECENT
MOISTURE ADVERTISED...WILL KEEP CHANCE POPS GOING FOR BOTH TUESDAY
AND WEDNESDAY. WILL PROBABLY SEE MORE SNOW DEVELOPING ON TUESDAY
NIGHT AND WEDNESDAY NIGHT WITH THE BEST CHANCE FOR ACCUMULATION
ACROSS THE HIGHER ELEVATIONS AGAIN. HIGH PRESSURE RETURNS BRINGING
DRY WEATHER FOR THURSDAY. STAYED NEAR MEX/HPC GUIDANCE FOR
TEMPERATURES.
&&
.PRELIMINARY POINT TEMPS/POPS...
CHATTANOOGA AIRPORT, TN 46 32 38 25 52 / 0 60 60 10 0
KNOXVILLE MCGHEE TYSON AIRPORT, TN 45 32 36 24 48 / 0 70 80 10 0
OAK RIDGE, TN 44 32 36 24 48 / 0 50 70 10 0
TRI CITIES AIRPORT, TN 44 32 35 21 46 / 0 60 80 20 0
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...WINTER STORM WATCH FROM LATE TONIGHT THROUGH SATURDAY EVENING
FOR THE FOLLOWING ZONES: BLOUNT SMOKY MOUNTAINS...COCKE
SMOKY MOUNTAINS...JOHNSON...SEVIER SMOKY MOUNTAINS...
SOUTHEAST CARTER...SOUTHEAST GREENE...UNICOI.
VA...NONE.
&&
$$
DGS/GH
