FXUS64 KOHX 110205
AFDOHX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NASHVILLE TN
805 PM CST THU DEC 10 2009

.UPDATE...VERY COLD HIGH PRESSURE WILL SETTLE OVER MID TN TONIGHT. 
WINDS ARE ALREADY NEAR CALM...DEW POINTS ARE MOSTLY IN THE 7 TO 12
RANGE...AND SKIES ARE CLEAR OTHER THAN SOME PATCHY INCONSEQUENTIAL
CIRRUS. BASED ON OBSERVATION TRENDS AND COMPARISONS TO UPSTREAM
CONDITIONS FROM LAST NIGHT...THE DAY FORECASTERS MADE AN EXCELLENT
DECISION UNDERCUTTING MOS TEMPS. IN FACT...WE WILL KNOCK DOWN
TEMPS A LITTLE MORE FOR OUTLYING AREAS. MOST OF MID TN WILL FALL
SOMEWHERE IN THE 12-16 RANGE...WITH A FEW OF THE USUALLY COLDER
SPOTS HITTING THE UPPER SINGLE DIGITS. LOOK FOR AN UPDATE SOON
WITH THESE MINOR ADJUSTMENTS.

13

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.PREV DISCUSSION... /ISSUED 330 PM CST THU DEC 10 2009/ 

DISCUSSION...
FORECAST REASONING WILL BE BASED ON A LEAN TOWARD A CONSENSUS MODEL 
SOLUTION FOR THE FORECAST PERIOD UNLESS OTHERWISE NOTED.

CURRENTLY...TEMPS MAINLY IN THE LOWER TO MID 30S...WITH DEWPOINTS
IN THE SINGLE DIGITS. SFC HIGH PRESSURE APEX APPROACHING THE MS
RIVER VALLEY REGION. WINDS W-NW 10 TO 20 MPH. A FEW CLOUDS HERE
AND THERE...BUT GENERALLY CLR SKIES. ZONAL FLOW ALOFT.   

FORECAST QUANDARIES...APEX OF HIGH PRESSURE SHOULD BE ACROSS
E PORTIONS OF MID STATE BY 12Z FRI. WINDS SHOULD DIE OFF AND
BECOME GENERALLY LIGHT IN NATURE. WITH ZONAL FLOW ALOFT NOT
USHERING IN ANY ADDITIONAL MOISTURE ADVECTION...THUS GENERALLY
CLR SKIES EXPECTED...AND WINDS EXPECTED TO BECOME LIGHT IN NATURE
..ALONG WITH DEWPOINTS AROUND NOON TODAY IN THE LOWER TEENS...
GOOD RADIATIONAL COOLING NIGHT LOOKS TO BE IN STORE. THUS...WILL
UNDERCUT LOWS ACROSS THE REGION 4 DEGREES OR MORE FROM CURRENT
GUIDANCE VALUES...AS MODELS DO NOT PICK UP WELL ON COLD TEMPS
SCENARIOS LIKE THIS WELL. THUS...TEMPS UPPER TO MID TEENS W
TO MID TO LOW TEENS PLATEAU.

LOOK FOR SUBTLE INCREASE IN MOISTURE AS SFC HIGH MOVES SLOWLY TO OUR 
E...AND A MORE E-SLY SFC WIND COMPONENT DEVELOPS THRU 12Z SAT.
GENERALLY DRY ZONAL FLOW ALOFT WILL CONTINUE...AND WILL UNDERCUT 
MODEL GUIDANCE TEMPS BY A FEW DEGREES ON FRI...BUT GO MORE IN LINE
WITH GFS MOS FOR FRI NIGHT AS IT IS REASONABLE IN ITS HANDLING OF 
THIS LOW TEMP SCENARIO WELL.

OVER THE WEEKEND...LOOK FOR INCREASING MOISTURE ASSOCIATED WITH
SFC LOW THAT WILL DEVELOP OF THE N TX COAST AND MOVE ACROSS THE N 
GULF BY THE AFTERNOON HOURS ON SAT...AND WITH SHORTWAVES IN SWLY 
FLOW ALOFT EXPECTED...ENOUGH DYNAMICS WILL BE IN PLACE FOR THE 
CHANCE OF RAINFALL ACROSS THE MID STATE FROM THE AFTERNOON HOURS ON 
SAT...EXCEPT FOR A SLIGHT CHANCE ACROSS PORTIONS OF THE N CUMBERLAND 
PLATEAU. BEST CHANCE OF RAINFALL WILL BE SAT NIGHT AS GULF LOW 
CONTINUES TO MOVE E...AND EXPECT TEMPS TO REMAIN MAINLY IN THE UPPER 
30S. WITH SFC AND TEMPS THRU THE BOUNDARY SEVERAL DEGREES ABOVE 
FREEZING...DO NOT EXPECT AT THIS TIME ANY CHANCE OF A WINTRY PCPN 
MIX. WILL GO WITH CHANCE POPS SUN MORNING...THEN DECREASING 
CLOUDINESS AS RIDGING DEVELOPS ALOFT AND WEAK SFC RIDGING ASSOCIATED 
WITH SLY FLOW DEVELOPS...AS THE SFC LOW EVENTUALLY MOVES OFF THE FL 
COAST BY 12Z MON. DURING THIS PERIOD...TEMPS SHOULD SLOWLY CLIMB 
OVER THE WEEKEND CLOSER TO CLIMATOLOGICAL NORMS.

AS A WEAK COLD FRONT MOVES THRU THE MID STATE ON MON...WILL CONTINUE
TO MENTION SLIGHT CHANCE OF SHWRS...AS UPPER FLOW MORE SWLY 
ORIENTATED WITH THE POSSIBILITY OF ADDITIONAL SHORTWAVE PASSAGES IN 
FLOW AS UPPER TROUGH BEGINS TO DEEPEN ACROSS CNTRL U.S. CHANCE OF 
RAIN EXPECTED MON NIGHT INTO TUE PER POST FRONTAL MOISTURE...WITH
BEST RAINFALL AMOUNTS ACROSS S PORTIONS OF THE MID STATE. RAINFALL
WILL BEGIN TO TAPER OFF BY LATE TUE AFTERNOON.

LOOK FOR CANADIAN BASED SFC HIGH AND RIDGING ALOFT TO PROVIDE FOR DRY
CONDITIONS AND BELOW NORMAL TEMPS THRU NEXT WEEKEND. WILL LEAN TOWARD
GFS MEX GUIDANCE VALUES THRU THIS PERIOD.

JBW

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.OHX WATCHES/WARNINGS/ADVISORIES...NONE. 

&&

$$