FXUS64 KEWX 301153
AFDEWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
553 AM CST MON NOV 30 2009
.AVIATION...
VFR SKIES WITH AREAS OF -RA WILL PREVAIL WITH CIGS ABOVE 5K FT,
EXCEPT LOCAL MVFR CIGS/VSBYS IN AND NEAR +RA. AN UPPER LOW WILL
APPROACH THE BIG BEND BY TUESDAY. THIS WILL CAUSE RA TO INCREASE
IN AREAL COVERAGE AND INTENSITY. IN TURN, CIGS/VSBYS WILL SLOWLY
LOWER WITH MVFR OVERNIGHT INTO TUESDAY MORNING AND THEN TO IFR
TUESDAY AFTERNOON. NLY WINDS OF 12 TO 20 KTS WITH GUSTS UP TO NEAR
30 KTS WILL PREVAIL THIS MORNING, DECREASE TO 5 TO 10 KTS LATE
THIS AFTERNOON AND EVENING, AND THEN INCREASE TO 8 TO 15 KTS LATE
TONIGHT AND TUESDAY.
&&
.PREV DISCUSSION... /ISSUED 500 AM CST MON NOV 30 2009/
DISCUSSION...
WINTER STORM ANALYSIS CONTINUES TO POINT TOWARD A MINOR INTRUSION OF
MIXED PRECIPITATION INTO OUR NORTHERN COUNTIES TUESDAY NIGHT INTO
WEDNESDAY MORNING. EARLY THIS MORNING, AN AREA OF RAIN IS WORKING TO
MODIFY THE FRONTAL INVERSION WHICH SHOULD LIMIT THE POTENTIAL FOR
SLEET TODAY AND TONIGHT. SFC OBS AND RADAR VAD WINDS SHOW A COLD
RAIN PATTERN FOR THE SOUTHERN EDWARDS PLATEAU AS THE UPPER LOW AND
SUBTROPICAL JET STREAM KICKS UP ABUNDANT OVERRUNNING RAINS.
THE HIGHER RAINFALL RATES SHOULD MAINLY BE BELOW HALF AN INCH PER
HOUR AS SUGGESTED BY THE KECU OBSERVATIONS AND AN APPARENT BRIGHTBAND
RADAR SIGNATURE THAT PASSED OVER. THUS SOME LIGHT OVERESTIMATION
OF RADAR RAIN ESTIMATES IS POSSIBLE NW OF SAN ANTONIO.
HIGHER RAINFALL RATES MAY DEVELOP OVER THE COASTAL PLAINS WHERE A
MORE SHALLOW FRONT WILL TAP INTO PRECIPITABLE WATER VALUES AROUND
1.25 INCHES. SPOTTY 1+ INCH TOTALS ARE POSSIBLE IN THESE AREAS
EACH 12-HOUR FORECAST PERIOD UNTIL THE UPPER LOW NUDGES THE
DEEPER LIFT EAST LATE TUESDAY NIGHT. THUS A 3-DAY STORM TOTAL
ENDING WEDNESDAY MORNING OVER THE COASTAL PRAIRIES SHOULD AVERAGE
1-2 INCHES, WITH ISOLATED 4 INCH AMOUNTS POSSIBLE. THIS STEADY
RAIN COULD PROMOTE SOME MINOR RUN-OFF PROBLEMS, WITH SOME LARGER
STREAMS POSSIBLY BECOMING SWOLLEN BY THE END OF THE PERIOD;
HOWEVER, FLASH FLOODING LOOKS UNLIKELY.
AS FOR THE WINTER MIX POTENTIAL TUESDAY, MODEL SOUNDINGS HAVE
SHOWN GOOD CONSISTENCY ON RAIN MIXING WITH SNOW. THE FRONTAL
INVERSION NEVER HAS A CHANCE TO ESTABLISH A SLEET PATTERN AS IS
BEING NOTED WITH THIS MORNING'S PRECIP TRENDS. THE UPPER LOW
CENTER DRAGGING E-NE LIFTING OUT OF WEST TX SHOULD PROVIDE THE
ONLY SIGNIFICANT THREAT OF WINTER WX. THE COLD MID-LEVEL
TEMPERATURES SHOULD ENTER OUR WESTERN COUNTIES TUESDAY EVENING
AND PASS THE RAIN-SNOW MIX JUST NORTH OF THE AUSTIN AREA BY 15Z
WEDNESDAY. GROUND TEMPERATURES SHOULD REMAIN ABOVE FREEZING, AND
NO ACCUMULATIONS ARE ANTICIPATED. HOWEVER, LATER SHIFTS MAY NEED
TO WATCH FOR BRIEF HEAVIER SNOWFALL RATES THAT COULD BRIEFLY COOL
LOW LEVEL TEMPERATURES AND SUPPORT A LIGHT ACCUMULATION.
MODEL TRENDS ARE LESS CONSISTENT BEHIND THE DEPARTING STORM
SYSTEM, WITH THE GFS TRENDS SHOWING AN DEEPENING LONGWAVE TROUGH
PATTERN OVER THE CENTRAL US LATE THIS WEEK. THIS SHOULD SUPPORT
COLDER ADVECTION BEHIND THE LOW AND POSSIBLY THE FIRST FREEZE OF
THE SEASON FOR SOME CENTRAL AND SOUTHERN COUNTIES BY THURSDAY
MORNING. THE UPPER TROUGH IS PROGRESSIVE, AND MOST MODELS SHOW A
ZONAL FLOW ALOFT DEVELOPING OVER THE AREA BY THE WEEKEND; THUS
MILDER WEATHER AND INCREASING GULF MOISTURE AND RAIN POTENTIAL IS
EXPECTED.
&&
.PRELIMINARY POINT TEMPS/POPS...
AUSTIN CAMP MABRY 55 44 46 41 55 / 70 50 90 70 20
AUSTIN BERGSTROM INTL AIRPORT 54 43 48 39 54 / 70 50 90 70 20
NEW BRAUNFELS MUNI AIRPORT 54 44 49 40 56 / 80 60 90 50 20
BURNET MUNI AIRPORT 52 40 44 36 50 / 50 40 80 70 20
DEL RIO INTL AIRPORT 53 44 52 37 57 / 80 70 80 20 10
GEORGETOWN MUNI AIRPORT 53 42 46 38 51 / 50 40 90 70 20
HONDO MUNI AIRPORT 54 44 50 39 56 / 80 70 90 40 10
SAN MARCOS MUNI AIRPORT 53 43 49 39 57 / 80 50 90 70 20
LA GRANGE - FAYETTE REGIONAL 55 45 51 43 57 / 80 60 80 70 30
SAN ANTONIO INTL AIRPORT 55 45 50 41 58 / 80 70 90 40 10
STINSON MUNI AIRPORT 55 45 51 41 59 / 90 70 90 40 10
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
18/04
