FXUS64 KSJT 031809
AFDSJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
1209 PM CST THU DEC 3 2009
.DISCUSSION...
EXPECT DEVELOPING MVFR TO IFR CEILINGS OVERNIGHT TONIGHT AS ANOTHER
UPPER-LEVEL DISTURBANCE MOVES ACROSS TEXAS AND BRINGS THE POTENTIAL
FOR SNOW. SEE AVIATION BELOW.
&&
.AVIATION...
ANOTHER UPPER-LEVEL TROUGH OF LOW PRESSURE WILL MOVE EAST ACROSS
WEST CENTRAL TEXAS BEGINNING LATER TONIGHT. MEANWHILE...SURFACE
TEMPERATURES WILL FALL BELOW THE FREEZING MARK ACROSS WEST CENTRAL
TEXAS A FEW HOURS BEFORE THIS UPPER TROUGH MOVES OUT OF EASTERN
NEW MEXICO AND INTO WEST TEXAS. THUS...ANY PRECIPITATION WHICH
FALLS ACROSS WEST CENTRAL TEXAS TONIGHT THROUGH THE END OF THIS
FORECAST CYCLE WILL BE SNOW. THE LATEST NAM12 AND BUFKIT DATA
INDICATE THE BEST CHANCE FOR SNOW WILL BE MAINLY ALONG AND SOUTH
OF OUR INTERSTATE 20 CORRIDOR AFTER MIDNIGHT TONIGHT. PLAN FOR
INITIAL VFR CEILINGS TO DECREASE INTO THE MVFR RANGE AFTER
MIDNIGHT. AS THE SYSTEM MOVES ACROSS WEST CENTRAL TEXAS AROUND
SUNRISE TOMORROW MORNING...INCREASING SNOWFALL MAY DROP CEILINGS
INTO THE IFR RANGE. AS FOR SURFACE WINDS...LOOK FOR MAINLY NORTH
WINDS AROUND 10 KNOTS OR LESS FOR THE NEXT 24 HOURS.
23/HUBER
&&
.PREV DISCUSSION... /ISSUED 455 AM CST THU DEC 3 2009/
AVIATION...
/12Z UPDATE/
VFR CONDITIONS ARE EXPECTED TO CONTINUE OVER THE NEXT 24
HOUR. LOW LEVEL WINDS WILL BECOME NORTH NORTHEAST AT 10 KNOTS OR
LESS LATE MORNING/EARLY AFTERNOON.
PREV DISCUSSION... /ISSUED 413 AM CST THU DEC 3 2009/
SHORT TERM...
MODELS ARE FAIRLY CONSISTENT WITH THE EVOLUTION OF A MID/UPPER
TROUGH AFFECTING THE FORECAST AREA TODAY INTO FRIDAY. THE GFS IS
MORE PROGRESSIVE THAN THE NAM IN THE SPEED OF THE TROUGH AXIS WITH
THE TROUGH AXIS OVER EASTERN NEW MEXICO BY DAYBREAK TOMORROW. WILL
NOT SUBSTANTIALLY CHANGE ONGOING POP FCST...SLIGHT CHANCE OVER THE
WESTERN TIER NEAR MIDNIGHT AND SPREADING OVER THE CWA BEFORE 12Z
FRIDAY WITH THE FASTER GFS. WILL KEEP SNOW TOTALS LIGHT THROUGH
THIS PERIOD. BEST DYNAMICS EXPECTED TO BE WEST OF THE AREA TONIGHT
WHERE THE GFS GENERATED MIDLEVEL DISTURBANCES ROTATING AROUND THE
BASE OF THE MID/UPPER TROUGH AXIS. FOLLOWING AFTERNOON HIGHS
TODAY IN THE UPPER 30S TO LOWER 40S...LOOKING FOR TEMPS DROPPING
WELL INTO THE 20S BY MIDNIGHT TONIGHT OVER MOST OF THE AREA.
LONG TERM...
THE MAIN CONCERN IN THE LONG TERM PORTION OF THE FORECAST REMAINS
THE SNOW POTENTIAL FRIDAY...AND COLD TEMPERATURES THROUGH SATURDAY
MORNING.
BY EARLY FRIDAY MORNING...THE AXIS OF THE LARGE TROUGH WILL
EXTEND FROM THE WESTERN GREAT LAKES REGION SOUTHWESTWARD INTO WEST
TEXAS. WEST AND WEST CENTRAL TEXAS WILL BE NEAR THE BASE OF THIS
TROUGH WHERE STRONG DYNAMICS WILL COMBINE WITH COLD TEMPERATURES
AT THE SURFACE TO CREATE A GOOD CHANCE FOR ACCUMULATING SNOWFALL.
AREAS OF FRONTOGENESIS IN THE MID LEVELS WILL BE COUPLED WITH
UPPER LEVEL LIFT AS THE TROUGH AXIS MOVES QUICKLY EAST THROUGH THE
AREA. THE TIMING FOR THIS COMBINATION CONTINUES TO BE DURING THE
MORNING HOURS FRIDAY...LARGELY AFTER SUNRISE FOR WEST CENTRAL
TEXAS. THE MID LEVEL FRONTOGENESIS ALSO APPEARS TO MAXIMIZED SOUTH
OF THE INTERSTATE 20 CORRIDOR FOR WEST CENTRAL TEXAS...HINTING
THAT THE BEST CHANCE FOR ACCUMULATING SNOWFALL WILL BE IN THE
CONCHO VALLEY AND HEARTLAND AREAS...AS WELL AS ALONG THE
INTERSTATE 10 CORRIDOR. THE ONE CONCERN AT THIS TIME APPEARS TO BE
A VERY DRY SUBCLOUD LAYER THAT WILL NEED SOME TIME TO SATURATE
BEFORE SNOW CAN REACH THE GROUND. BELIEVE THE STRENGTH OF THE
SYSTEM WILL BE ABLE TO OVERCOME THIS DRY LAYER AND CREATE SNOWFALL
ACCUMULATION BETWEEN 1 AND 2 INCHES ACROSS A FAIRLY BROAD
REGION...MAINLY SOUTH OF INTERSTATE 20...WITH BANDS OF HEAVIER
AMOUNTS POSSIBLE. AS THE SYSTEM MOVES QUICKLY EAST...PRECIPITATION
WILL END FROM WEST TO EAST DURING THE AFTERNOON. HAVE KEPT HIGH
TEMPERATURES COLD FOR FRIDAY WITH EXPECTED
CLOUDCOVER...PRECIPITATION...AND CONTINUED COLD AIR ADVECTION.
CLEARING SKIES AND LIGHT WINDS AND POSSIBLE SNOWCOVER BEHIND THE
TROUGH FRIDAY NIGHT WILL SET THE AREA UP FOR VERY COLD OVERNIGHT
LOWS SATURDAY. HAVE UNDERCUT GUIDANCE BY A FEW DEGREES FOR
SATURDAY MORNING LOWS.
FOLLOWING THE SNOW POTENTIAL FOR FRIDAY...THE FORECAST SHOULD BE
MAINLY DRY FOR THE AREA. GENERALLY ZONAL FLOW WILL ALSO ALLOW
TEMPERATURES TO WARM BACK UP TO NEAR NORMAL LEVELS. A QUICKLY
PASSING TROUGH SUNDAY WILL CREATE THE POTENTIAL FOR PRECIPITATION
EAST OF THE AREA...AND A WEAK COLD FRONT MONDAY.
A STRONGER TROUGH WILL AFFECT THE AREA TUESDAY INTO WEDNESDAY. THE
BEST CHANCE FOR PRECIPITATION REMAINS EAST OF THE FORECAST AREA
THOUGH...SO HAVE KEPT FORECAST DRY. COOLER TEMPERATURES WILL MOVE
IN BEHIND A COLD FRONT FOR WEDNESDAY.
&&
.PRELIMINARY POINT TEMPS/POPS...
ABILENE 41 19 36 21 50 / 0 20 50 10 0
SAN ANGELO 44 24 34 20 48 / 0 20 60 10 0
JUNCTION 46 31 37 18 49 / 0 20 60 10 0
&&
.SJT WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
23/HUBER
