Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX

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000
FXUS64 KEWX 291126
AFDEWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
626 AM CDT TUE JUL 29 2014

.AVIATION...
VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD. A WEAK FRONTAL
BOUNDARY DRAPED ACROSS NERN PORTIONS OF THE REGION WILL ATTEMPT TO
SLIDE SOUTHWARD THROUGHOUT THE DAY. NORTH OF THE BOUNDARY...WINDS
WILL BE NE-ERLY 5 TO 10 KTS. OTHERWISE...SFC WINDS WILL BE SERLY 5
TO 10 KTS. ISOLATED TO SCATTERED SHRA/TSRA IS POSSIBLE ALONG AND
NORTHEAST OF A LINE ROUGHLY FROM KERV TO KSAT TO KVCT...BUT
COVERAGE AND LIKELIHOOD ARE TOO LOW TO WARRANT EXPLICIT MENTION IN
THE TAFS.

&&

.PREV DISCUSSION... /ISSUED 352 AM CDT TUE JUL 29 2014/

SHORT TERM (TODAY THROUGH WEDNESDAY)...
LATEST SURFACE ANALYSIS SHOWS THE WEAK FRONTAL BOUNDARY NEARLY
STATIONARY ALONG A LINE FROM LLANO TO AUSTIN TO NEAR GIDDINGS. THE
FRONT IS NOT EXPECTED TO MOVE MUCH IN THE NEAR TERM...BUT THE
RAP/HRRR/WRFS MOVE THE BOUNDARY A BIT MORE SOUTH THIS AFTERNOON
THAN PREVIOUSLY EXPECTED. BY 3 PM THE FRONT COULD BE AS FAR SOUTH
AS A KERRVILLE TO NEW BRAUNFELS TO LA GRANGE LINE. THE LATEST 06Z
NAM IS EVEN FARTHER SOUTH THAN THE PREVIOUSLY MENTIONED LOCATIONS.
BEHIND THE FRONT WILL BE THE BEST AREA FOR ANY ISOLATED TO
SCATTERED CONVECTION TO DEVELOP. THERE SHOULD BE ABOUT 1500 J/KG
OF CAPE AND WITH LITTLE CIN UPDRAFTS SHOULD BE ABLE TO BE GET
GOING. PW VALUES ARE EXPECTED TO BE 1.8-2.0 INCHES AND BRIEF
MODERATE RAIN IS LIKELY FROM THE STRONGER SHOWERS AND STORMS.
GIVEN THE EXPECTED MOVEMENT OF THE WEAK BOUNDARY FARTHER
SOUTH...EXPANDED THE SLIGHT CHANCE POPS TO ENCOMPASS MORE OF THE
AREA. ALL ACTIVITY SHOULD DISSIPATE BY EARLY EVENING WITH THE LOSS
OF DAYTIME HEATING.

THE CURRENT SYNOPTIC PATTERN SHOWS A LARGE LONGWAVE TROUGH OVER
THE NORTHEASTERN CONUS WITH AN AMPLIFIED RIDGE OVER THE WESTERN
CONUS. THIS PLACES THE PLAINS IN NORTHWEST FLOW ALOFT. AN
EMBEDDED DISTURBANCE IN THE NW FLOW IS EXPECTED TO APPROACH THE
CENTRAL PLAINS TONIGHT. THIS WILL LEAD TO LEE SIDE CYCLOGENESIS
AND THE FRONT SHOULD RESPOND BY QUICKLY MOVING NORTH AND SOUTH
FLOW SHOULD PREVAIL TOMORROW. FORECAST SOUNDINGS SHOW A PRETTY
STOUT CAPPING INVERSION AND WILL LEAVE THE FORECAST WEDNESDAY RAIN
FREE. TEMPERATURES TODAY AND TOMORROW WILL FOLLOW A NEARLY
PERSISTENCE FORECAST AS THE LOW-LEVEL THERMO PROFILE REMAINS
UNCHANGED EXCEPT FOR THE NORTHERN COUNTIES THIS AFTERNOON. AREAS
NORTH OF THE BOUNDARY TODAY SHOULD BE ABOUT 2 DEGREES COOLER THAN
YESTERDAY.

LONG TERM (WEDNESDAY NIGHT THROUGH MONDAY)...
THE PREVIOUSLY MENTIONED DISTURBANCE EMBEDDED IN THE NORTHWEST
FLOW SHOULD APPROACH THE AREA THURSDAY. THIS WILL SEND THE FRONT
BACK TO THE SOUTH AS A COLD FRONT AND IT SHOULD INITIALLY
REACH THE HILL COUNTRY THURSDAY AFTERNOON. YESTERDAY WE MENTIONED
THAT THERE WOULD BE ANOTHER DISTURBANCE IN THE NORTHWEST FLOW THAT
WOULD CAUSE OUR FRONT TO STALL OVER SOUTH- CENTRAL TEXAS FOR ABOUT
36 HOURS BRINGING PROLONGED RAIN CHANCES TO THE AREA. THE FORECAST
MODELS HAVE LOST THIS FEATURE OVER THE PAST COUPLE OF RUNS AND THE
FRONT IS NOW EXPECTED TO PUSH SOUTH OF THE FORECAST AREA BY FRIDAY
EVENING INSTEAD OF SATURDAY.

THE HEAVY RAINFALL POTENTIAL LOOKS LESS PROMISING AS WELL. IN
ADDITION TO THE LOSS OF A STALLED FRONTAL BOUNDARY...850 FLOW
AHEAD OF THE FRONT IS ONLY FORECAST TO BE 5-10 KNOTS WHICH DOES
NOT HELP STRONGLY LIFT AIR PARCELS ON TOP OF THE FRONTAL
LAYER...HELPING THE RAIN PRODUCTION. ALSO NOT EXPECTING MUCH POST-
FRONTAL PRECIP AS WELL...DUE TO THE 850 FRONT LINING UP NEARLY
OVER THE SURFACE FRONT. NORTH WINDS AT 850 USUALLY MEAN RAIN
CHANCES WILL BE ENDING. NEVERTHELESS...THERE WILL BE A FRONTAL
BOUNDARY...WEAK UPPER SUPPORT AND PW VALUES ABOVE 2 INCHES IN
PLACE OVER SOUTH CENTRAL TEXAS. THESE THREE INGREDIENTS ALONE
SHOULD ALLOW A FAIRLY DECENT COVERAGE OF ACTIVITY THURSDAY NIGHT
THROUGH FRIDAY WITH SHOWER AND THUNDERSTORM COVERAGE SLOWLY
TRANSITIONING FROM NORTH TO SOUTH ACROSS THE FORECAST AREA. ALSO
WITH PW VALUES ABOVE TWO INCHES...RAINFALL TOTALS OF A FEW INCHES
ARE POSSIBLE FOR ISOLATED LOCATIONS WHO HAPPEN TO BE UNDER ONE OF
THE HEAVY DOWNPOURS. LOCALLY HEAVY RAINFALL IS STILL
POSSIBLE...BUT THE LIKELIHOOD OF WIDESPREAD HEAVY RAINS APPEAR
LESS LIKELY THAN YESTERDAY.

WILL END ALL POPS BY SATURDAY AND WILL SHOW A MOSTLY DRY FORECAST
FOR THE REST OF THE PERIOD. PROLONGED NORTHERLY FLOW WILL ENSURE
HIGHS THURSDAY AND BEYOND WILL BE A DEGREE OR TWO BELOW NORMAL FOR
THIS TIME OF THE YEAR. THE ONLY MENTION OF RAIN BEYOND SATURDAY
WILL BE MONDAY ACROSS THE FAR SOUTHEASTERN ZONES FOR POTENTIAL SEA
BREEZE ACTIVITY.

HAMPSHIRE

&&

.PRELIMINARY POINT TEMPS/POPS...
AUSTIN CAMP MABRY              98  75  99  75  95 /  30  -   -   -   40
AUSTIN BERGSTROM INTL AIRPORT  99  72  99  74  95 /  30  -   -   -   40
NEW BRAUNFELS MUNI AIRPORT     99  71 100  74  96 /  20  -   -   -   20
BURNET MUNI AIRPORT            95  73  98  74  91 /  30  -   -   10  30
DEL RIO INTL AIRPORT           98  78 101  78  98 /  -    0   0  10  20
GEORGETOWN MUNI AIRPORT        96  73  98  74  93 /  30  -   -   10  40
HONDO MUNI AIRPORT             99  71  99  73  97 /  10  -   -   -   20
SAN MARCOS MUNI AIRPORT        98  72  99  74  96 /  20  -   -   -   30
LA GRANGE - FAYETTE REGIONAL   98  75  98  76  95 /  30  10  -   -   20
SAN ANTONIO INTL AIRPORT       97  75  99  77  96 /  20  -   -   -   20
STINSON MUNI AIRPORT           99  73  99  75  98 /  20  -   -   -   10

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

MESOSCALE/AVIATION...25
SYNOPTIC/GRIDS...29





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