FXUS64 KHUN 030942
AFDHUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
342 AM CST THU DEC 3 2009
.DISCUSSION...
LATEST WATER VAPOR IMAGERY AND H5 RUC ANALYSIS SHOWS BROAD TROUGHING
ACROSS THE CENTRAL CONUS. AT THE SURFACE...THE COLD FRONT THAT
BROUGHT GUSTY WINDS AND RAIN TO THE TENNESSEE VALLEY ON WEDNESDAY IS
WELL TO THE EAST OF HERE...AND WHILE THE REGIONAL RADAR VIEW IS
PICKING UP ON A FEW LIGHT ECHOS ACROSS TENNESSEE...CONDITIONS REMAIN
DRY CLOSER TO HOME. THE STORY FOR THE IMMEDIATE SHORT TERM FOCUSES
ON TEMPERATURES AS UPSTREAM OBS SHOW MOSTLY 20S AND 30S UNDER
CONTINUED NORTHWEST FLOW. AS THE UPPER TROUGH CONTINUES TO SAG
SOUTH...UNSEASONABLY COOL TEMPERATURES WILL CONTROL THE FORECAST
WITH HIGHS TODAY AND TOMORROW RUNNING AROUND 10 DEGREES BELOW
NORMAL...OR IN THE 40S.
THE MAIN FORECAST FOCUS FOR THIS PACKAGE STARTS WELL NORTHWEST OF
HERE WITH A LITTLE SHORTWAVE CURRENTLY DIGGING INTO MONTANA/WYOMING
AROUND THE WESTERN FRINGE OF THE H5 TROUGH. AS HIGH AMPLITUDE FLOW
SENDS THIS SHORTWAVE INTO SOUTHERN TEXAS ON FRIDAY IT MERGES WITH A
SECOND WEAK WAVE OVER THE GOMEX AND SPINS UP A SURFACE CYCLONE IN
THE WESTERN GOMEX FRIDAY AFTERNOON. WITH THE TENNESSEE VALLEY
SITTING WELL NORTH/NORTHWEST OF THE LOW...THE CHANCE OF SEEING SNOW
ON FRIDAY NIGHT INTO EARLY SATURDAY MORNING LOOKS INCREASINGLY
LIKELY WITH EACH MODEL RUN.
THE 00Z RUNS OF THE NAM/GFS ARE IN PRETTY GOOD AGREEMENT WITH THE
POSITION OF THE LOW...BUT MORE IMPORTANTLY...SHOW GOOD AGREEMENT WRT
BUFR INDICATED MOISTURE/TEMPERATURE PROFILES AT BOTH MSL AND HSV.
ACROSS EXTREME NORTHWEST ALABAMA...WHILE BUFR PROFILES ARE NEARLY
SATURATED ABOVE H8 BY 06Z SATURDAY...THE LOWEST LEVELS ARE STILL
VERY DRY /ESPECIALLY THE NAM/ SO OPTED TO RETAIN VERY LOW-END POPS
IN THIS AREA...ESPECIALLY CONSIDERING THE 03Z SREFS AOA 1-IN
PROBABILITY IS LESS THAN 25 PERCENT NORTHWEST OF MSL.
AT THIS POINT...THE BEST CHANCE OF SNOW SHOULD BE CENTERED ALONG A
CULLMAN-MARSHALL-JACKSON AXIS...WHERE A NW-SE CROSS SECTION SHOWS A
NICE MIDLEVEL /H55-60/ FGEN/OMEGA COUPLET. HOWEVER...THE BEST
AGEOSTROPHIC VERT CIRC IS SOUTHEAST OF THE CWFA. 03Z SREF
PROBABILITIES SUPPORT ABOUT A 50/50 CHANCE OF AOA 1-IN IN THIS
AREA...WITH NON-ZERO /BUT EXTREMELY LOW/ 4-IN PROBABILITIES. BIGGEST
CONCERN IN THE NORTHEAST AND SNOW TOTALS CENTERS AROUND SURFACE
TEMPERATURES...WHICH WILL BE VERY MARGINAL FRIDAY NIGHT/SATURDAY
MORNING. HOWEVER...ANY SORT OF WET-BULB COOLING IN THE LOWEST LEVELS
SHOULD ALLEVIATE THIS CONCERN.
A QUICK LOOK AT SOIL TEMPERATURES FROM AROUND THE AREA INDICATES
THAT MOST LOCATIONS ARE IN THE UPPER 40S AT 2IN AND 4IN DEPTHS...SO
EVEN IF WE DO SEE A FEW TENTHS OF SNOW...GROUNDS TEMPERATURES WELL
ABOVE FREEZING SHOULD LIMIT ACCUMULATIONS AND THEREFORE TRAVEL
CONCERNS. NEVERTHELESS...WILL CONTINUE TO HIGHLIGHT THIS POTENTIAL
WINTER WEATHER SITUATION IN THE HAZARDOUS WEATHER OUTLOOK. STAY
TUNED TO THE LATEST FORECAST...AS WINTER WEATHER FORECASTING IN THE
TENNESSEE VALLEY COMES WITH A RELATIVELY HIGH DEGREE OF UNCERTAINTY.
THE REST OF THE FORECAST REMAINS LARGELY UNCHANGED FROM THE PREVIOUS
PACKAGE...WITH RAIN SHOWERS DEVELOPING BY TUESDAY IN RESPONSE TO
ANOTHER UPPER LEVEL SYSTEM. WITH GOOD CONTINUITY BETWEEN THE
GFS/ECMWF...OPTED TO INCREASE POPS SLIGHTLY...BUT NO MAJOR CHANGES
MADE.
&&
.PRELIMINARY POINT TEMPS/POPS...
HUNTSVILLE 46 31 44 31 40 / 0 0 0 30 20
SHOALS 47 29 43 28 42 / 0 0 0 20 20
VINEMONT 46 31 44 28 38 / 0 0 0 40 20
FAYETTEVILLE 43 30 43 29 36 / 10 0 0 30 20
ALBERTVILLE 46 31 45 30 37 / 0 0 0 50 30
FORT PAYNE 49 33 48 32 39 / 0 0 0 50 40
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
JLL
