FXUS64 KMRX 050847
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
347 AM EST SAT DEC 5 2009
.SHORT TERM (TODAY AND TONIGHT)...
IR SATELLITE INDICATES AN AREA OF COLDER CLOUD TOPS FROM THE OHIO
VALLEY TO CENTRAL AL. THIS IS AN AREA OF SYNOPTIC SCALE FORCING IN
THE ENTRANCE REGION OF A STRONG UPPER JET AND AHEAD OF THE 500 MB
SHORTWAVE TROUGH. MODELS INDICATE GOOD Q-VECTOR CONVERGENCE THAT
WILL BRING LIFT TO THE SOUTHERN APPALACHIANS THROUGH THE MORNING AS
THE TROUGH MOVES EAST. CROSS SECTIONS ALSO INDICATE THAT LIFT IS
CORRELATED WITH AGEOSTROPHIC CIRCULATIONS AROUND THE ENTRANCE REGION
OF THE JET...AND IS MAXIMIZED OVER EAST TN BETWEEN 09Z AND 15Z. BUT
OVERALL...LIFT IS NOT VERY STRONG DUE TO A LACK OF LOW LEVEL
FORCING...AND EXITS MOST OF THE AREA BY THE AFTERNOON.
SURFACE TEMPERATURES ARE CURRENTLY BETWEEN 35 AND 40 ACROSS THE
AREA...AND HAVE BEEN DROPPING VERY SLOWLY OVER THE PAST SEVERAL
HOURS IN RESPONSE TO WEAK COLD ADVECTION. DEWPOINTS HAVE BEEN
DROPPING AS WELL...SO WHEN THE PRECIP REACHES THE GROUND...TEMPS
SHOULD COOL TO NEAR FREEZING. PRECIP MAY BEGIN AS RAIN BEFORE
CHANGING OVER TO SNOW. DUE TO THE LACK OF STRONG LIFT AS DESCRIBED
ABOVE...THE SNOW SHOULD NOT BE HEAVY FOR THE MOST PART. MARGINAL
TEMPS AND LIGHT TO MODERATE SNOWFALL RATES SHOULD PREVENT MUCH
ACCUMULATION IN THE VALLEY. HIGHER ELEVATIONS WHERE TEMPS ARE COLDER
SHOULD SEE GREATER AMOUNTS. TWEAKED THE FORECAST SNOW AMOUNTS DOWN
SLIGHTLY FROM THE PREVIOUS FORECAST...BUT NOT SIGNIFICANTLY. WE ARE
EXPECTING LESS THAN 1 INCH IN THE CENTRAL AND SOUTHERN VALLEY...WITH
1-3 INCHES IN THE NORTHERN PLATEAU/NORTHERN TN VALLEY/SW VA/SW
NC...AND 1-4 IN THE SMOKIES AND NE TN MOUNTAINS. THE CURRENT
ADVISORY AREAS AND THE SPS WILL BE KEPT IN TACT.
THE NAM AND THE GFS SHOW THE 700 MB TROUGH PASSAGE OCCURRING LATE IN
THE AFTERNOON...WITH DRY ADVECTION QUICKLY FOLLOWING. PRECIP SHOULD
BE OVER BEFORE 00Z...WITH CLEARING SKIES THROUGH THE EVENING. THIS
CLEARING ALONG WITH DIMINISHING WINDS THAT WILL BECOME CALM AFTER
MIDNIGHT SHOULD ALLOW TEMPS TO PLUNGE INTO THE 20S EVERYWHERE. WITH
WET ROADS FROM THE DAYTIME PRECIP...BLACK ICE WILL LIKELY BE A
PROBLEM SUNDAY MORNING. WILL CONTINUE TO MENTION THIS IN THE WSW AND
THE SPS.
.LONG TERM (SUNDAY THROUGH FRIDAY)...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. ANOTHER FRONT ENTERS THE REGION ON TUESDAY AND LINGERS
INTO WEDNESDAY. WITH DECENT MOISTURE ADVERTISED...WILL BUMP UP POPS
TO LIKELY FOR TUESDAY NIGHT AND CHANCE FOR WEDNESDAY. MODELS
INDICATING PRECIPITATION SHOULD BE ALL LIQUID NOW ON BOTH TUESDAY NIGHT
AND WEDNESDAY. WITH COLDER AIR FILTERING BEHIND THE FRONT...MAY
STILL SEE SNOW DEVELOPING ON WEDNESDAY NIGHT WITH THE BEST CHANCE
FOR ACCUMULATION ACROSS THE HIGHER ELEVATION. HIGH PRESSURE RETURNS
BRINGING DRY WEATHER FOR THURSDAY. ANOTHER FRONT MOVES INTO THE
REGION ON FRIDAY. WITH STILL UNCERTAINTY ON TIMING...WILL KEEP
FRIDAY DRY FOR NOW. STAYED NEAR MEX/HPC GUIDANCE FOR TEMPERATURES.
&&
.PRELIMINARY POINT TEMPS/POPS...
CHATTANOOGA AIRPORT, TN 40 24 50 33 48 / 60 0 0 10 20
KNOXVILLE MCGHEE TYSON AIRPORT, TN 37 23 46 31 48 / 90 10 0 10 20
OAK RIDGE, TN 37 23 46 31 47 / 80 10 0 10 20
TRI CITIES AIRPORT, TN 36 22 45 29 47 / 100 10 0 10 20
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR THE
FOLLOWING ZONES: CHEROKEE...CLAY.
TN...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR THE
FOLLOWING ZONES: BLOUNT SMOKY MOUNTAINS...CAMPBELL...
CLAIBORNE...COCKE SMOKY MOUNTAINS...EAST POLK...HANCOCK...
HAWKINS...JOHNSON...MORGAN...NORTHWEST CARTER...NORTHWEST
GREENE...SCOTT TN...SEVIER SMOKY MOUNTAINS...SOUTHEAST
CARTER...SOUTHEAST GREENE...SOUTHEAST MONROE...SULLIVAN...
UNICOI...WASHINGTON TN.
VA...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR THE
FOLLOWING ZONES: LEE...RUSSELL...SCOTT...WASHINGTON...WISE.
&&
$$
DGS/GH
