504
FXUS64 KEWX 091213
AFDEWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
613 AM CST TUE FEB 9 2010
AVIATION
A LAYER OF MVFR STRATUS WILL SLOWLY ERODE BY MID MORNING LEAVING
VFR SKIES WITH SOME MID AND UPPER LEVEL CLOUDS LATE MORNING INTO
TONIGHT. INCREASED MOISTURE AND ISENTROPIC LIFT WILL LEAD TO A
LOWERING OF CIGS TO MVFR EARLY WEDNESDAY MORNING AS PRECIPITATION
DEVELOPS ALONG THE RIO GRANDE AND THEN SPREADS EAST ACROSS THE
REMAINDER OF SOUTH CENTRAL TEXAS LATE WEDNESDAY MORNING INTO THE
AFTERNOON. A MIX OF -RA, -SN, AND -IP CAN BE EXPECTED DUE SOME
LAYERS OF AIRMASS BEING BELOW FREEZING. NLY WINDS OF 10 TO 20 KTS
WITH GUSTS TO 25 KTS WILL PREVAIL MOST AREAS THIS MORNING INTO THE
AFTERNOON, AND THEN DECREASE TO LESS THAN 10 KTS TONIGHT. EXCEPT,
ALONG THE RIO GRANDE, NLY WINDS OF 5 TO 10 KTS TODAY WILL BECOME
ELY TO SELY TONIGHT.
PREV DISCUSSION
/ISSUED 536 AM CST TUE FEB 9 2010/
DISCUSSION...
A MIX OF WINTER PRECIPITATION REMAINS A GOOD POSSIBILITY OVER MUCH
OF SOUTH CENTRAL TEXAS OVER THE NEXT FEW DAYS. LIGHT ELEVATED
FLURRIES ARE BEING DETECTED BY RADAR THIS MORNING...BUT DRY LOW
LEVEL CONDITIONS SHOULD EVAPORATE THE MOISTURE BEFORE IT REACHES
THE SURFACE...AND MODELS SHOW THE EARLY MORNING LIFTING MECHANISM
TO WEAKEN WITH TIME.
MORNING LOW CLOUDS AND STRONG NORTH WINDS OF 15-25 MPH EARLY WILL
HOLD MOST HIGH TEMPS IN THE 40S TO SET UP A COLD NIGHT TONIGHT.
CLOUDS AND ISENTROPIC LIFT INCREASES BACK OVER THE AREA FROM THE
WEST TONIGHT...PREVENTING A HARD FREEZE OVER MANY AREAS WITH THE
BEST CHANCE OF A HARD FREEZE OVER NE COUNTIES. LIGHT PRECIPITATION
IS EXPECTED TO DEVELOP TOWARD DAYBREAK NEAR THE RIO GRANDE...AND
SPREAD EAST ACROSS MUCH OF SOUTH CENTRAL TX DURING THE DAY
WEDNESDAY. MODEL SOUNDINGS SUGGEST EARLY WEDNESDAY TO BE THE
PERIOD WHEN MIXED PRECIP CAN BE SEEN FARTHEST SOUTH...BUT RATES
ARE EXPECTED TO BE TOO LIGHT TO AMOUNT TO ACCUMULATION UNTIL
TEMPERATURES MODIFY LOW LEVELS TO PROMOTE A CHANGE BACK TO MAINLY
RAIN. HIGHER ELEVATIONS OVER NORTHWEST COUNTIES COULD SEE ENOUGH
LOW LEVEL TEMPERATURE MODIFICATION FROM THE EARLY PRECIPITATION TO
PROMOTE A CONTINUED MIX INTO WEDNESDAY NIGHT AND THURSDAY...BUT
LIGHT RATES AND WARMER SURFACE CONDITIONS ARE STILL EXPECTED TO
PREVENT ANY SIGNIFICANT ACCUMULATION OF ICE. MODEL TRENDS HAVE
SHOWN THE STORM TRACK GOING INCREASINGLY FARTHER SOUTH WITH
SUCCESSIVE RUNS...SUGGESTING A BETTER OPPORTUNITY TO KEEP LOW
LEVEL TEMPERATURES ABOVE FREEZING WITH NEAR 100 PERCENT HUMIDITIES
THROUGH SEVERAL THOUSAND FEET THROUGH THURSDAY EVENING.
THE BEST CHANCE FOR MEASURABLE WINTER PRECIPITATION IS EXPECTED
TO OCCUR LATE THURSDAY NIGHT AS THE UPPER LOW CENTER OPENS UP AS A
TROUGH AND SLIDES EAST TO SOUTHEAST ACROSS THE AREA. BY MIDNIGHT
FRIDAY MORNING...MODELS SHOW THE COLDER AIR ALOFT DESCENDING
TOWARD THE SURFACE WITH RAIN LIKELY CHANGING OVER TO SNOW FOR
AREAS GENERALLY ALONG AND NORTH OF THE BALCONES ESCARPMENT. THE
GFS FORECAST OPENING OF THE LOW INTO AN OPEN WAVE ALOFT SUGGESTS
PRECIPITATION RATES WOULD ONLY SUPPORT SNOW ACCUMULATIONS OF
AROUND AN INCH AT BEST FOR PARTS OF THE HILL COUNTRY.
HOWEVER...THE NAM MODEL CONTINUES A MORE COMPACT SYSTEM THAT COULD
SUGGEST MORE SNOW AND A DURATION LINGERING INTO THE LATE MORNING
HOURS FRIDAY. WITH A SHORT PERIOD OF OPPORTUNITY TO ACCUMULATE
SNOW AND A WEAKENING STORM SYSTEM...WILL ANTICIPATE A LOWER IMPACT
WINTER WX EVENT AND CONTINUE ADDRESSING THE THREAT WITH AN SPS FOR
ANOTHER SHIFT.
MODEL RUNS FOR LATER PERIODS CONTINUE TO TREND COLDER FOR THE
WEEKEND...BUT CONSENSUS ALSO IS TRENDING DRIER WITH LESS
SUBTROPICAL JET ACTIVITY.
PRELIMINARY POINT TEMPS/POPS
AUSTIN CAMP MABRY 47 32 45 34 43 / - - 20 70 70
AUSTIN BERGSTROM INTL AIRPORT 46 28 45 34 42 / - - 20 70 80
NEW BRAUNFELS MUNI AIRPORT 49 32 44 34 44 / - - 40 70 80
BURNET MUNI AIRPORT 43 27 42 33 37 / - - 20 70 70
DEL RIO INTL AIRPORT 50 36 42 35 44 / - 20 60 50 50
GEORGETOWN MUNI AIRPORT 45 29 44 34 41 / - - 20 70 70
HONDO MUNI AIRPORT 50 32 43 34 41 / - - 50 70 70
SAN MARCOS MUNI AIRPORT 47 31 44 34 43 / - - 30 70 80
LA GRANGE - FAYETTE REGIONAL 47 32 47 35 43 / - - 30 60 80
SAN ANTONIO INTL AIRPORT 49 33 44 35 43 / - - 40 70 80
STINSON MUNI AIRPORT 49 33 44 35 43 / - - 40 70 80
EWX WATCHES/WARNINGS/ADVISORIES
NONE.
18/04
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