FXUS64 KMRX 240255
AFDMRX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MORRISTOWN TN
950 PM EST WED DEC 23 2009
.DISCUSSION...FORECAST ON TRACK. NO UPDATE PLANNED. LIGHT PCPN
TO THE WEST APPEARED TO THREATEN E TN OVERNIGHT. UPPER PATTERN
BECOMING LESS FAVORABLE OVERNIGHT SO POP FREE NIGHT LOOKS GOOD.
MIN TEMPS MAY BE A DEGREE TOO COOL BUT WILL LET STAND. SON
PREVIOUS DISCUSSION:
SHORT TERM (TONIGHT THROUGH FRIDAY NIGHT)...
A CLOSED LOW WILL BE SLOWLY TRACKING NORTHEAST ACROSS THE
PLAINS...WHILE HIGH PRESSURE WILL REMAIN FIRMLY ANCHORED OVER THE
EAST COAST. A LOW LEVEL SOUTH-SOUTHWESTERLY FLOW ON THE WEST SIDE OF
THE RIDGE AXIS TODAY WILL BACK TO A MORE SOUTH-SOUTHEASTERLY
DIRECTION THROUGH TONIGHT...PROVIDING INCREASING MOISTURE THROUGH
THE COLUMN AND FAVORABLE CONDITIONS FOR MOUNTAIN WAVES.
HOWEVER...THE ONSET OF PRECIP LOOKS TO BE DELAYED WITH EACH MODEL
RUN AS THE EASTWARD PROGRESS OF THE LOW IS SLOW. IN ADDITION...WITH
A STRENGTHENING SOUTHEASTERLY FLOW...DOWNSLOPE WINDS WILL LIKELY
CREATE A SHADOW EFFECT IN THE TN VALLEY AND FURTHER DELAY THE ONSET
OF RAIN IN NORTHERN SECTIONS. LIFT REMAINS WEAK OVER OUR AREA UNTIL
A NEGATIVELY-TILTED UPPER TROUGH WILL CROSS THE LOWER MS VALLEY AND
THE TN VALLEY THURSDAY NIGHT...PROVIDING GOOD UPPER DIVERGENCE OVER
OUR AREA. SO WILL REMOVE THE POPS FROM TONIGHT...LOWER POPS IN THE
NORTHERN VALLEY TO A SLIGHT CHANCE THROUGH THURSDAY...AND BRING
LIKELY POPS IN THE SOUTH THURSDAY AFTERNOON. CATEGORICAL POPS
EVERYWHERE WILL CONTINUE THURSDAY NIGHT. PASSAGE OF THE COLD FRONT
OCCURS ON FRIDAY...AND MODELS INDICATE DRY AIR ALOFT MOVING IN
RAPIDLY FRIDAY MORNING. WILL END ALL POPS ACROSS THE AREA BEFORE 00Z
SATURDAY. WINDS WILL ALSO BE TAPERING OFF THROUGH FRIDAY AFTERNOON
AS THE PRESSURE GRADIENT SLACKENS AND BOUNDARY LAYER WINDS TURN TO
THE SOUTHWEST.
THE HIGH WIND WATCH FOR THE MOUNTAINS AND FOOTHILLS WILL BE CHANGED
TO A HIGH WIND WARNING AS CONDITIONS CONTINUE TO LOOK FAVORABLE FOR
A SIGNIFICANT MOUNTAIN WAVE EVENT. BOTH THE NAM AND THE GFS SHOW
WINDS OF 75 KTS AT 850 MB. EVEN AT ONLY 3000 FEET...WINDS REACH 50
KTS FOR A SUSTAINED PERIOD THURSDAY NIGHT. THUS WILL ISSUE A WIND
ADVISORY FOR THE CUMBERLAND PLATEAU COUNTIES...SOUTHWEST
VIRGINIA...AND EXTREME SOUTHWEST NORTH CAROLINA.
ANOTHER POTENTIAL ISSUE WILL BE FLOODING...MAINLY IN AREAS THAT
STILL HAVE SNOW COVER...PRIMARILY THE TN MOUNTAINS AND SOUTHWEST
VIRGINIA. MELTING SNOW COMBINED WITH ONE HALF TO ONE INCH OF
RAINFALL COULD CAUSE SOME SMALL CREEKS AND STREAMS TO FLOOD. AN SPS
WILL BE ISSUED TO ADDRESS THIS.
LONG TERM (SATURDAY THROUGH THURSDAY)...
HUGE UPPER LOW MOVES FROM GREAT LAKES AREA SLOWLY OUT TO NORTHEAST
DURING THE PERIOD, REPLACED BY SHORT RIDGING IN SOUTHEASTERN U.S.
WEAK COLD FRONT MOVES OUT LATE TUESDAY WITH UPPER LOW, REPLACED BY
SURFACE HIGH WHICH ALSO TAKES ITS SWEET TIME MOVING IN. AIR MASS IS
QUITE DRY AND SO POPS VERY LOW. WHEN THERE ARE POPS, WENT WITH
SLIGHT CHANCE SNOW SHOWERS, NO ACCUMULATION EXPECTED. TEMPS STILL
IN PRETTY AGREEMENT WITH PREVIOUS FORECAST, A HAIR ON THE COOL SIDE
COMPARED TO CLIMATOLOGY.
&&
.PRELIMINARY POINT TEMPS/POPS...
CHATTANOOGA AIRPORT, TN 38 54 44 50 29 / 10 60 100 20 10
KNOXVILLE MCGHEE TYSON AIRPORT, TN 35 52 42 50 29 / 0 30 100 50 10
OAK RIDGE, TN 36 52 43 49 29 / 0 30 100 40 10
TRI CITIES AIRPORT, TN 31 49 36 48 30 / 0 20 100 90 10
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...WIND ADVISORY FROM 4 PM THURSDAY TO NOON EST FRIDAY FOR THE
FOLLOWING ZONES: CHEROKEE...CLAY.
TN...WIND ADVISORY FROM 4 PM EST /3 PM CST/ THURSDAY TO NOON EST /11
AM CST/ FRIDAY FOR THE FOLLOWING ZONES: BLEDSOE...
CAMPBELL...CLAIBORNE...MARION...MORGAN...SCOTT TN...
SEQUATCHIE.
HIGH WIND WARNING FROM 4 PM THURSDAY TO NOON EST FRIDAY FOR THE
FOLLOWING ZONES: BLOUNT SMOKY MOUNTAINS...COCKE SMOKY
MOUNTAINS...EAST POLK...JOHNSON...MCMINN...NW BLOUNT...
NORTH SEVIER...NORTHWEST CARTER...NORTHWEST COCKE...
NORTHWEST GREENE...NORTHWEST MONROE...SEVIER SMOKY
MOUNTAINS...SOUTHEAST CARTER...SOUTHEAST GREENE...SOUTHEAST
MONROE...UNICOI...WASHINGTON TN...WEST POLK.
VA...WIND ADVISORY FROM 4 PM THURSDAY TO NOON EST FRIDAY FOR THE
FOLLOWING ZONES: LEE...RUSSELL...SCOTT...WASHINGTON...WISE.
&&
$$
DGS/BB
