203  
FXUS64 KEWX 201130  
AFDEWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX  
630 AM CDT MON AUG 20 2018  
   
AVIATION
 
 
SHRA ARE IN THE VCNTY OF KSAT/KSSF AND KEPT MENTION THERE THRU 16Z.  
SHRA ARE PUSHING AWAY FROM KAUS AND HAVE NO FURTHER MENTION. EXPECT  
REDEVELOPMENT OF SHRA/TSRA THIS AFTERNOON INTO EVENING. THERE REMAINS  
UNCERTAINTY ON EXACT LOCATIONS AND, FOR NOW, HAVE LEFT OUT MENTION  
IN ALL TAFS. WILL MONITOR RADAR AND MODEL TRENDS FOR ANY UPDATES TO  
MENTION. VFR FLYING CONDITIONS WILL PREVAIL AT ALL TAF SITES, WITH  
SCT MVFR LEVEL STRATUS THRU MID MORNING AND OVERNIGHT INTO TUESDAY  
MORNING. ANY SHRA/TSRA MAY BRING BRIEF MVFR CIGS/VSBYS. WINDS OF 10  
KTS OR LESS ARE EXPECTED, HOWEVER THE STRONGER SHRA/TSRA MAY PRODUCE  
GUSTS UP TO 40 KTS OR SO.  
 

 
   
PREV DISCUSSION
 
/ISSUED 429 AM CDT MON AUG 20 2018/  
 
SHORT TERM (TODAY THROUGH TUESDAY)...  
WEAK ISENTROPIC ASCENT WITHIN THE LOWER LEVELS (ON THE 305K  
SURFACE, ROUGHLY BETWEEN THE GROUND AND 850 MB) IS PRODUCING  
ISOLATED SHOWERS ALONG THE INTERSTATE 37 CORRIDOR EARLY THIS  
MORNING WITH A SECONDARY ROUND OF SHOWER ACTIVITY ALONG A MID-  
LEVEL TROUGH LOCATED AROUND 700 MB. GLOBAL AND HIGHER RESOLUTION  
MODELS SHOW GREATEST PRESSURE ADVECTION ASSOCIATED WITH THIS  
ASCENT SHIFTING FROM I-37 TOWARDS THE RIO GRANDE SOMETIME AROUND  
SUNRISE THROUGH MID-MORNING. AS THIS HAPPENS, WOULD EXPECT AT  
LEAST SOME OF THE RIO GRANDE PLAINS ACTIVITY TO BEGIN SHIFTING  
WEST AND DISSIPATE. ACTIVITY ALONG THE MID-LEVEL TROUGH WILL  
CONTINUE SHIFTING SOUTH TOWARDS INTERSTATE 10 THROUGH THE EARLY  
MORNING HOURS.  
 
ONCE SHOWERS AND LOW CLOUDS CLEAR LATER THIS MORNING, A COLD FRONT  
PUSHING SOUTH ACROSS THE TEXAS PANHANDLE AS OF 3 AM WILL MOVE INTO  
SOUTH CENTRAL TEXAS SOMETIME THIS AFTERNOON. WHILE CONVERGENCE ALONG  
THE FRONT DOES NOT APPEAR TO BE VERY STRONG WITH THE 00Z SUITE OF  
GUIDANCE, CONVECTIVE TEMPERATURES IN THE MID TO UPPER 90S SHOULD BE  
REACHED IN THE MID TO LATE AFTERNOON HOURS. THIS WILL ALLOW FOR  
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS TO DEVELOP ALONG THE  
FRONTAL BOUNDARY, WHICH IS EXPECTED TO BE SOMEWHERE ALONG OR NORTH OF  
THE I-10/I-37 CORRIDOR THIS AFTERNOON. VERY WARM CONVECTIVE  
TEMPERATURES AND FORECAST SOUNDINGS SHOWING DRY AIR IN BOTH THE MID-  
LEVELS AND IN THE SUB-CLOUD LAYER WILL MEAN THAT AN ISOLATED GUSTY  
WIND THREAT WILL EXIST THIS AFTERNOON AND EVENING FROM STRONGER  
CONVECTIVE ACTIVITY. (THE DRIER AIR EVIDENT ON THE FORECAST SOUNDINGS  
INDICATES GOOD POTENTIAL FOR EVAPORATIONAL COOLING AND CONSEQUENTLY  
DOWNDRAFT ACCELERATION.) SPC HREF MEMBERS, HRRR, AND ARW/NMM  
SOLUTIONS SEEM TO FAVOR THE MOST LIKELY AREA FOR DEVELOPMENT  
SOMEWHERE ALONG AND NORTH OF A DEL RIO TO BOERNE TO AUSTIN LINE THIS  
AFTERNOON AND EVENING, BUT GIVEN THE POTENTIAL FOR THUNDERSTORMS TO  
PRODUCE GUSTY WINDS TODAY SOME OF THIS ACTIVITY MAY SAG FARTHER SOUTH  
OR HAVE HIGHER COVERAGE THAN ANTICIPATED ALONG AFOREMENTIONED  
OUTFLOW BOUNDARIES.  
 
MODEST SOUTHERLY WINDS 10-15 MPH ALONG THE MID AND UPPER TEXAS COASTS  
TODAY WILL ALLOW FOR THE SEA BREEZE TO REACH THE COASTAL COUNTIES  
LATER THIS AFTERNOON. THIS BOUNDARY WILL SERVE AS A SECONDARY FOCUS  
FOR SHOWER AND THUNDERSTORM DEVELOPMENT TODAY ACROSS THE COASTAL  
PLAINS. THERE IS A LOW POTENTIAL THAT THE SEA BREEZE AND THE COLD  
FRONT COULD COLLIDE SOMEWHERE NEAR I-10 ACROSS THE EASTERN  
COUNTIES/COASTAL PLAINS LATE THIS AFTERNOON OR EVENING SHOULD OUTFLOW  
DRIVE THE FRONT FARTHER SOUTH, RESULTING IN ADDITIONAL THUNDERSTORM  
DEVELOPMENT. WOULD HAVE TO KEEP AN EYE OUT FOR SOME BRIEF HEAVY RAIN  
IN THAT AREA SHOULD THAT SCENARIO OCCUR GIVEN VERY HIGH ATMOSPHERIC  
MOISTURE (FORECAST PWATS NEAR 1.8-2 INCHES).  
 
OUTSIDE OF RAIN, HEAT INDEX VALUES THIS AFTERNOON WILL CLIMB TO NEAR  
OR ABOVE 105 IN MANY LOCATIONS EAST OF THE INTERSTATE 35 CORRIDOR  
THIS AFTERNOON. LOSS OF DAYTIME HEATING SHOULD ALLOW FOR MOST  
THUNDERSTORM ACTIVITY TO DISSIPATE BY MID-EVENING AND PROVIDE RELIEF  
FROM THE HEAT, BUT THE FRONTAL BOUNDARY IS EXPECTED TO REMAIN DRAPED  
ACROSS THE FORECAST AREA. DRIER AIR BEHIND THE FRONT SHOULD ALLOW  
FOR TEMPERATURES TO FALL INTO THE LOWER 70S ACROSS THE EDWARDS  
PLATEAU BY TUESDAY MORNING WITH LOWS IN THE MID TO UPPER 70S  
ELSEWHERE. THE REMNANT COLD FRONT IS EXPECTED TO RESULT IN ISOLATED  
TO POSSIBLY SCATTERED SHOWER AND THUNDERSTORM DEVELOPMENT AGAIN ON  
TUESDAY AS HIGHS RISE INTO THE UPPER 90S TO LOW 100S.  
 
LONG TERM (TUESDAY NIGHT THROUGH SUNDAY)...  
THE COLD FRONT GRADUALLY LOSES DEFINITION AND WASHES OUT TUESDAY  
NIGHT AS UPPER RIDGING BUILDS OVER TEXAS AND PERSISTS THROUGH THE END  
OF THE WEEK. THIS WILL END RAIN CHANCES FOR SOUTH CENTRAL TEXAS IN  
THE LONG TERM PORTION OF THE FORECAST AND RESULT IN HIGH TEMPERATURES  
CLIMBING INTO THE UPPER 90S TO LOW 100S EACH DAY THROUGH THE END OF  
THE WORK WEEK. THE SEA BREEZE MAY TRY TO MAKE ANOTHER RUN AT THE  
COASTAL COUNTIES BY SUNDAY, BUT SUBSIDENCE FROM THE UPPER RIDGE LOOKS  
TO BE TOO MUCH FOR RAIN TO OVERCOME THIS FAR OUT.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
AUSTIN CAMP MABRY 98 77 100 77 100 / 30 20 20 10 -  
AUSTIN BERGSTROM INTL AIRPORT 98 77 100 75 101 / 30 20 20 10 -  
NEW BRAUNFELS MUNI AIRPORT 97 75 99 75 100 / 20 20 20 10 -  
BURNET MUNI AIRPORT 97 74 98 73 99 / 30 20 20 10 -  
DEL RIO INTL AIRPORT 98 78 101 78 102 / 20 20 10 10 -  
GEORGETOWN MUNI AIRPORT 98 76 99 74 100 / 30 20 20 10 -  
HONDO MUNI AIRPORT 99 74 101 74 102 / 20 20 10 10 -  
SAN MARCOS MUNI AIRPORT 98 76 100 75 101 / 20 20 20 10 -  
LA GRANGE - FAYETTE REGIONAL 99 78 101 76 101 / 20 20 20 10 -  
SAN ANTONIO INTL AIRPORT 98 77 99 77 101 / 20 20 20 10 -  
STINSON MUNI AIRPORT 98 77 100 76 100 / 20 20 10 10 -  
 

 
   
EWX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
MESOSCALE/AVIATION...04  
SYNOPTIC/GRIDS...HUFFMAN  
 
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