weather.gov     
National Weather Service

Area Forecast Discussion
NWS Homepage
This page is being discontinued on March 12, 2014.
The same data is available at this site. Please update your bookmarks.
Thank you, and we apologize for the inconvenience.
Please send an email to SR-SRH.Webmaster@noaa.gov with any concerns.


Current Version
Previous Version:    01  02  03  04  05  06  07  08  09  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  
   31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  
[Printable]
850
FXUS64 KEWX 211756
AFDEWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
1156 AM CST FRI NOV 21 2014

.AVIATION... /18Z TAF UPDATE/
SCATTERED SHOWERS WILL IMPACT THE I-35 TERMINALS FOR MUCH OF
TODAY...WITH ISOLATED TSRA POSSIBLE. MOST OF THE TSRA SHOULD
DEVELOP EAST OF I-35...SO WILL NOT MENTION TSRA THROUGH THIS
EVENING. LATE TONIGHT...SOME OF THE HIGHER RES MODELS SHOW DEEP
CONVECTION FORMING MAINLY WEST OF I-35...WITH LOWER RES MODELS
SHOWING THE ACTIVITY CLOSER TO THE I-35 TAF SITES. WILL DEFER TO
THE HIGHER RES SOLUTIONS AND EXPECT CONVECTION MAINLY TO IMPACT
THE TERMINALS AFTER 12Z. WITH INCREASING SURFACE WINDS AND HIGH
LEVELS OF LOW LEVEL MOISTURE...WILL STICK WITH A PREVAILING IFR
CIG FOR MOST OF THE LATER PERIODS WITH LIFR CONDITIONS AT DRT.

&&

.PREV DISCUSSION... /ISSUED 909 AM CST FRI NOV 21 2014/

UPDATE...
TO BETTER DEFINE SEVERE THREAT SATURDAY.

DISCUSSION...
WE HAVE DECIDED FOR CONSISTENCY TO FOCUS THE SEVERE THREAT ON
SATURDAY AFTERNOON AND EARLY EVENING. HAVE ADJUSTED WEATHER GRIDS
TO REFLECT THIS. OTHERWISE FORECAST LOOKS GOOD FOR NOW.

PREV DISCUSSION... /ISSUED 548 AM CST FRI NOV 21 2014/

AVIATION DISCUSSION...FOR 12Z TAF PACKAGE...
A COMPLEX FORECAST FOR THIS TAF PERIOD AS LOW LEVEL MOISTURE IS
PLENTIFUL RESULTING IN MVFR/IFR/LIFR CATEGORIES IN VIS AND CIG
THROUGHOUT THE NIGHT. THESE CONDITIONS WILL LIKELY PERSIST THROUGH
THE MORNING HOURS BEFORE ALL TERMINALS GENERALLY IMPROVE TO MVFR
CIGS BY MID DAY. KAUS/KSSF/KSAT TERMINALS SHOULD EXPERIENCE
ISOLATED TO SCATTERED SHOWER ACTIVITY THROUGHOUT THE DAY AS WELL
WITH POSSIBLE -TSRA IN THE AFTERNOON. BY NIGHTFALL...BR SHOULD
RETURN FOR ALL TERMINALS TO AT LEAST MVFR.

AN APPROACHING STORM SYSTEM WILL IMPACT ALL TERMINALS TOMORROW
MORNING WITH HIGHEST CHANCE AT KAUS SO INCLUDED PROB30 LATE IN THE
PERIOD FOR PLANNING PURPOSES BEYOND 24 HOURS.

TB3

PREV DISCUSSION... /ISSUED 409 AM CST FRI NOV 21 2014/

SHORT TERM (TODAY THROUGH SATURDAY)...
CLOUDY SKIES AND PATCHY FOG HAVE OVERSPREAD SOUTH CENTRAL TEXAS
OVERNIGHT AS CONTINUED SOUTHERLY FLOW PUMPS IN WARMER TEMPERATURES
AND HIGHER MOISTURE INTO THE AREA. THE WEAK LIFT ASSOCIATED WITH
THE WARM AIR ADVECTION HAS LED TO ISOLATED SHOWER DEVELOPMENT
SINCE YESTERDAY AND THIS WILL CONTINUE MAINLY ACROSS THE EASTERN
ZONES EARLY THIS MORNING. CURRENTLY...THE LOW-LEVEL FLOW IS SSW IN
THE LOWEST 4 KM OF THE ATMOSPHERE. BY THE AFTERNOON MOST GUIDANCE
MEMBERS ARE BACKING THE WINDS TO THE SSE AND INCREASING THE LOW-
LEVEL JET IN RESPONSE TO THE APPROACHING UPPER LOW WHICH IS
CURRENTLY OVER SOUTHERN CALIFORNIA PER LATEST WATER VAPOR
ANALYSIS. THE BACKING OF THE WIND AND INCREASING OF THE SPEED WILL
LEAD TO A STRONG PUSH OF POSITIVE THETA-E ADVECTION BEGINNING
IN THE SOUTHEAST ZONES...NEAR THE COASTAL PLAINS THIS AFTERNOON.
THE NOSE OF THE INCREASING THETA-E VALUES WILL THEN PUSH NORTHWEST
TO THE I-35 CORRIDOR BY 6 PM AND THEN THE HILL COUNTRY AND EDWARDS
PLATEAU BY MIDNIGHT. POSITIVE THETA-E ADVECTION IS A DIRECT
MEASURE OF INCREASING TEMPERATURE/MOISTURE WHICH IS LIFT. THIS
LIFT CAN ALSO BE SEEN ON ISENTROPIC CHARTS ON CONSTANT THETA
SURFACES. EXPECT ABOUT A 50 TO 60 PERCENT COVERAGE OF SHOWERS AND
THUNDERSTORMS IN THE FORM OF A BROKEN LINE BEGINNING THIS
AFTERNOON ACROSS THE SOUTHEAST AND THEN MOVING NORTHWEST THROUGH
MIDNIGHT.

AS WE GET INTO TOMORROW MORNING...CONTINUED WEAK LIFT ON
ISENTROPIC CHARTS WILL RESULT IN ISOLATED TO SCATTERED ACTIVITY
ACROSS MUCH OF THE AREA. ALSO BY TOMORROW MORNING...THE UPPER LOW
IS PROGGED TO BE NEAR NORTHERN MEXICO...ENTERING WEST TEXAS.
MODELS ARE IN FAIRLY GOOD AGREEMENT WITH THE PLACEMENT AND
STRENGTH OF THE LOW AS IT PROGRESSES THROUGH THE AREA. THIS LOW IS
EXPECTED TO TRANSITION FROM A POSITIVE TILT TO EITHER A NEUTRAL OR
SLIGHTLY NEGATIVE TILT AS IT MOVES OVER THE AREA SATURDAY
AFTERNOON. A NEGATIVE TILT TO AN UPPER TROUGH IS MORE CONDUCIVE
FOR THUNDERSTORM DEVELOPMENT AS UPPER DIFFLUENCE COMMENCES AHEAD
OF THE TROUGH. MODELS ARE FORECASTING THE CENTER OF THE STRONGEST
LIFT OF THE UPPER LOW TO MOVE ACROSS THE HEART OF OUR CWA AS IS
EVIDENT BY THE PEAK TROPOPAUSE FOLD TO 430 MB OVER SAN ANTONIO
SATURDAY NIGHT. THIS SHOULD EQUATE TO SUBSTANTIAL UPPER FORCING
FOR ASCENT AND WILL LEAD TO WIDESPREAD SHOWER AND THUNDERSTORM
ACTIVITY ACROSS MUCH OF IF NOT ALL THE CWA. THE QUESTION THEN
TURNS TO THE INSTABILITY/SHEAR PARAMETERS AND ANY MESOSCALE
FEATURES THAT COME INTO PLAY FOR SEVERE WEATHER CHANCES.

MODELS ARE IN FAIRLY GOOD AGREEMENT THAT THERE WILL BE AROUND 750
TO 1500 J/KG OF SURFACE BASED CAPE ACROSS MUCH OF THE AREA
SATURDAY. THIS AMOUNT OF INSTABILITY IN ADDITION TO 40 KNOTS OF
0-6 KM SHEAR WILL BE SUFFICIENT FOR ORGANIZED CONVECTION. THE MAIN
LIMITING FACTOR WILL BE THE AMOUNT OF ACTIVITY AND WHAT EFFECT
THAT WILL HAVE ON SEVERE CHANCES. IF THERE IS TOO MUCH OF A
COVERAGE OF ACTIVITY...IT WILL BE DIFFICULT TO REALIZE THE PEAK
INSTABILITY VALUES. NEVERTHELESS...THE MOST LIKELY SCENARIO WILL
BE WIDESPREAD ACTIVITY WITH EMBEDDED ROTATING THUNDERSTORMS AS THE
ACTIVITY MOVES FROM WEST TO EAST DURING THE DAY SATURDAY. LARGE
HAIL AND DAMAGING WINDS WILL BE THE MAIN THREATS. THE SHERB INDEX
IS A FORECAST TOOL TO HELP WITH THESE HIGH SHEAR/LOW CAPE EVENTS
AND CURRENT FORECASTED VALUES ARE ABOVE 1.0 WHICH IS FAVORABLE FOR
SEVERE CONVECTION...MAINLY IN THE FORM OF A QLCS OR INDIVIDUAL
LINE SEGMENTS. THIS SEEMS REASONABLE AND CAN SOMEWHAT BE SEEN ON
THE HIGH-RES MODELS. THE TORNADO THREAT IS NON-ZERO GIVEN THE
AMOUNT OF LOW-LEVEL SHEAR EXPECTED OVER THE AREA. WOULD LIKE TO
SEE MORE DISCRETE ACTIVITY AND A FOCUSED SURFACE BOUNDARY OVER THE
AREA TO EXPECT ANYTHING GREATER THAN ISOLATED TORNADOES.

MODELS MOSTLY AGREE THAT THE ACTIVITY WILL SHUT OFF FROM WEST TO
EAST PRETTY RAPIDLY IN THE AFTERNOON. BY 6 PM...THE BACK EDGE OF
THE CONVECTION SHOULD BE JUST EAST OF THE I-35 CORRIDOR. DRY WEST
WINDS FROM THE SURFACE TO 850 MB WILL MOVE IN AHEAD OF THE UPPER
LOW AND THIS WILL END THINGS. THE OUTLIER IS THE NAM WHICH IS
DEVELOPING ANOTHER LINE OF STORMS AROUND 6 PM WEST OF THE I-35
CORRIDOR...BUT THE NAM 850 WINDS ARE UNREALISTIC. IT KEEPS THE
WEST WIND SHIFT DIRECTLY UNDERNEATH THE 500 MB LOW...WHILE THE
REST OF THE GUIDANCE MEMBERS HAVE THE WIND SHIFT AHEAD OF THE LOW
WHICH IS MORE REALISTIC.

THE LAST THING TO FOCUS ON IS THE HEAVY RAIN POTENTIAL ACROSS THE
AREA. THE HIGHEST RAIN TOTALS WILL BE ACROSS THE EASTERN AND
NORTHERN ZONES. MOISTURE SHOULD POOL UP NICELY IN THAT CORRIDOR
AS A WEAK SURFACE LOW DEVELOPS JUST NORTH OF OUR CWA. PW VALUES
WILL BE AROUND 1.5 OR ABOUT 2 STANDARD DEVIATIONS ABOVE THE MEAN
FOR THIS TIME OF THE YEAR. THESE AREAS WILL LIKELY RECEIVE 1 TO 2
INCHES OF RAIN WITH ISOLATED LOCATIONS PICKING UP 4 INCHES.

LONG TERM (SATURDAY NIGHT THROUGH THURSDAY)...
THE REST OF THE THUNDERSTORM ACTIVITY WILL BE EXITING THE AREA BY
MIDNIGHT SATURDAY NIGHT. DRY WEST WINDS WILL BE LEFT IN PLACE
SUNDAY AND THIS SHOULD BE A WARM AND SUNNY DAY FOR THE AREA WITH
HIGHS REACHING LOWER TO MIDDLE 70S. A LONGWAVE TROUGH WILL PASS
THROUGH THE PLAINS SUNDAY AND WILL SEND A DRY FRONT INTO THE
REGION BY MONDAY MORNING COOLING THINGS OFF ONCE AGAIN. THE REST
OF THE WEEK SHOULD REMAIN DRY WITH HIGHS IN THE 60S AND LOWS IN
THE 30S/40S. THANKSGIVING LOOKS DRY AND SEASONAL.

HAMPSHIRE

&&

.PRELIMINARY POINT TEMPS/POPS...
AUSTIN CAMP MABRY              63  70  55  76  47 /  50 100  20  -   10
AUSTIN BERGSTROM INTL AIRPORT  62  71  53  77  45 /  50 100  30  -   10
NEW BRAUNFELS MUNI AIRPORT     64  73  53  77  47 /  50  80  20  -   10
BURNET MUNI AIRPORT            61  68  51  74  43 /  50 100  10  -   10
DEL RIO INTL AIRPORT           62  74  50  77  47 /  40  50  10   0  -
GEORGETOWN MUNI AIRPORT        62  69  53  75  45 /  50 100  30  -   10
HONDO MUNI AIRPORT             62  73  48  75  44 /  50  60  10  -   10
SAN MARCOS MUNI AIRPORT        63  72  52  77  46 /  50  90  20  -   10
LA GRANGE - FAYETTE REGIONAL   63  74  57  76  48 /  30  90  60  -   10
SAN ANTONIO INTL AIRPORT       65  74  54  77  48 /  50  70  10  -   10
STINSON MUNI AIRPORT           65  75  53  77  48 /  50  70  10  -   10

&&

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

$$

MESOSCALE/AVIATION...18
SYNOPTIC/GRIDS...05
PUBLIC SERVICE/DATA COLLECTION...00






U.S. Dept. of Commerce
NOAA National Weather Service
1325 East West Highway
Silver Spring, MD 20910
E-mail: w-nws.webmaster@noaa.gov
Page last modified: May 16, 2007
NATIONAL WEATHER SERVICE: for Safety, for Work, for Fun - FOR LIFE