Winter Storm in Tennessee, January 20, 2001

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
325 AM EST SAT JAN 20 2001

SURFACE LOW WAS OVER WESTERN NC...AND NORTHWESTERLY FLOW WAS
STARTING TO BRING IN THE COLDER AIR MASS. NEXT WE TURN OUR FOCUS TO
THE 50H UPPER LOW SPINNING OVER WESTERN KY AND WEST TN. ALREADY A
DECENT AREA OF SNOW HAS DEVELOP WITH THIS FEATURE ACROSS CENTRAL KY
AND PARTS OF MIDDLE TN...WITH VISIBILITIES GENERALLY BETWEEN 1 AND 3
MILES. ALL OF THE MODELS IN DECENT AGREEMENT WITH THIS FEATURE...BUT
THE NGM DOES NOT HAVE AS MUCH MOISTURE WITH THE SYSTEM. GIVEN THE
CURRENT STATE OF THIS UPPER LOW...WILL GO WITH THE ETA/AVN WHICH
WERE IN VERY CLOSE AGREEMENT WITH QPF AND MOISTURE.

MID LEVEL DRY SLOT WORKING OVER THE AREA...AND MOISTURE IS NOT AS
DEEP...NOT ALLOWING FOR MUCH ICE NUCLEATION EARLY THIS MORNING. EXPECT
SOME PATCHY DRIZZLE (PATCHY FREEZING DRIZZLE IN THE COLDER
LOCATIONS) THROUGH THE EARLY MORNING HOURS. THEN BY 15Z THE DEEPER
MOISTURE WILL WORK INTO THE CWA...AND BY THEN IT WILL BE COLD ENOUGH
ACROSS THE ENTIRE CWA TO MENTION SNOW.

TODAY THERE WILL BE SOME WEAK SURFACE TO 80H CONVERGENCE...ALONG
WITH QVECTOR CONVERGENCE ASSOCIATED WITH THE 50H LOW. THIS SHOULD BE
ENOUGH TO BRING LIGHT SNOWFALL AMOUNTS (QPF OF .1 TO .2) TO MUCH OF
THE AREA...EXCLUDING SE TN WHERE THE MOISTURE JUST WONT BE DEEP
ENOUGH FOR A LONG PERIOD OF TIME. WILL MENTION AN INCH OR LESS FOR
THE CENTRAL VALLEY AND NE TN...BUT 1 TO 2 INCHES FOR THE NRN
PLATEAU...SW VA...SE TN MOUNTAINS...AND EXTREME SW NC. HIGHER
AMOUNTS HERE FOR MORE QPF DUE TO LIFT ENHANCEMENT FROM UPSLOPE FLOW.
THIS WILL REQUIRE AN ADVISORY FOR THESE LOCATIONS. STILL HAVE SOME
CONCERNS ABOUT HOW MUCH WILL ACTUALLY STICK...DUE TO THE WARM AND
WET GROUND. EXPECT THE HIGHEST ELEVATIONS TO HAVE THE BEST CHANCE OF
GOOD ACCUMULATING SNOWS.

THE UPSLOPE COMPONENT WILL BE STRONGEST FOR THE SMOKY AND NE TN
MOUNTAINS. HERE THE 00Z MESO-ETA INDICATES 80H OMEGA OF GREATER THAN
10 MICROBARS...CAPES AROUND 100 J/KG...AND QPFS AROUND .3 INCHES.
THIS UPSLOPE FLOW WILL CONTINUE INTO THE EVENING...AND THEN DIMINISH
AFTER MIDNIGHT. WILL ISSUE A WINTER STORM WARNING FOR TODAY AND THIS
EVENING FOR THESE MOUNTAIN GROUPS FOR 2 TO 4 INCHES OF SNOW...AND
THE NW WINDS OF 15 TO 25 MPH WILL HELP TO DETERIORATE CONDITIONS.

THEN TONIGHT...SUBSIDENCE WORKS INTO THE REGION. ETA SOUNDINGS
INDICATE THAT SOME MOISTURE MAY GET TRAPPED BELOW THE SUBSIDENCE
INVERSION...SO WILL BE A LITTLE MORE PESSIMISTIC ABOUT THE CLOUDS
TONIGHT. THEN CLOUDS SHOULD CLEAR SUNDAY MORNING. WILL REMOVE THE
SLIGHT CHANCE OF SNOW FOR SUNDAY NIGHT AND MONDAY...AS THE NEXT 50H
SHORTWAVE WILL BE DIVING FARTHER SOUTH.

TEMPS STEADY OR SLOWLY FALLING TODAY. WILL GO TOWARD THE WARM SIDE
TONIGHT WITH MORE CLOUDS. AND WILL GO A BIT COOLER ON SUNDAY...EVEN
WITH SUNSHINE. WITH ALL OF THE RAIN AND SNOW...MOST OF THAT SUNSHINE
WILL GO TOWARD EVAPORATION AND NOT WARMING THE SURFACE.

FCSTID = 25
CHA   34  22  43  25 /  40   0   0   0
TYS   33  21  38  22 /  60  10   0   0
TRI   34  20  37  17 /  70  30   0   0
OQT   33  20  39  21 /  60  10   0   0

.MRX...
NC...SNOW ADVISORY FOR TODAY FOR ZONES NCZ060>061.

TN...SNOW ADVISORY FOR TODAY FOR ZONES TNZ012>014...TNZ035...
TNZ087...TNZ102.
     WINTER STORM WARNING FOR TODAY AND THIS EVENING FOR THE SMOKY
AND NE MOUNTAINS.

VA...SNOW ADVISORY FOR TODAY FOR ZONES VAZ001>002...VAZ005>006...
VAZ008.

RBP