860  
FXUS64 KEWX 141150  
AFDEWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX  
650 AM CDT FRI MAY 14 2021  
   
UPDATE
 
 
PLEASE SEE THE 12Z AVIATION FORECAST DISCUSSION BELOW.  
 

 
   
AVIATION
 
 
LOW CLOUDS CONTINUE THIS MORNING, BUT BASES HAVE YET TO LOWER INTO  
MVFR ALONG THE I-35 CORRIDOR. BASED ON THE LATEST GUIDANCE, WE WILL  
ONLY MENTION A TEMPO GROUP FOR SAT BETWEEN 14-16Z THIS MORNING.  
OTHERWISE, EXPECT VFR CONDITIONS ALONG I-35 THROUGH THIS EVENING. LOW  
CLOUDS SHOULD RETURN QUICKLY ALONG I-35 AFTER 15/04Z. AT DRT, MVFR  
CLOUDS ARE INTACT AND WILL CONTINUE THROUGH EARLY AFTERNOON.  
IMPROVEMENT BACK TO VFR IS EXPECTED AFTER 18Z, WITH LOW CLOUDS  
RETURNING AROUND 15/07Z. WE COULD ALSO SEE SOME CONVECTION DEVELOP  
ACROSS THE RIO GRANDE PLAINS EARLY SATURDAY MORNING, WITH THE BEST  
CHANCE EXPECTED JUST BEYOND THE END OF THE CURRENT TAF PERIOD AT DRT.  
 

 
   
PREV DISCUSSION
 
/ISSUED 337 AM CDT FRI MAY 14 2021/  
 
SHORT TERM (TODAY THROUGH SATURDAY)...  
 
EARLY MORNING SATELLITE IMAGERY AND SURFACE OBSERVATIONS SHOW LOW  
CLOUDS ARE IN PLACE ACROSS A GOOD PORTION OF SOUTH CENTRAL TEXAS.  
TEMPERATURES CURRENTLY RANGE FROM THE MID 50S IN THE HILL COUNTRY TO  
NEAR 70 DEGREES ACROSS THE COASTAL PLAINS AND ALONG THE RIO GRANDE.  
 
CLOUDS WILL REMAIN FAIRLY THICK THROUGH THE MORNING HOURS, WITH SOME  
DECREASE IN COVERAGE EXPECTED LATE IN THE AFTERNOON. WITH COOL  
TEMPERATURES ALREADY IN PLACE AND CLOUDS KEEPING A LIMIT ON  
INSOLATION, AFTERNOON HIGHS WILL BE BELOW NORMAL, WITH UPPER 70S TO  
MID 80S IN STORE. WE WILL KEEP THE FORECAST DRY FOR TODAY, BUT WILL  
CONTINUE TO MENTION A LOW CHANCE FOR SHOWERS AND THUNDERSTORMS ALONG  
THE RIO GRANDE AFTER MIDNIGHT. SOME WEAK UPPER LEVEL DISTURBANCES  
MOVING IN FROM THE WEST COMBINED WITH GULF MOISTURE SHOULD ALLOW  
SOME CONVECTION TO DEVELOP EARLY SATURDAY MORNING ALONG THE RIO  
GRANDE.  
 
RAIN CHANCES INCREASE SIGNIFICANTLY ALONG THE RIO GRANDE SATURDAY  
MORNING, THEN SPREAD EAST ACROSS THE REMAINDER OF THE REGION  
SATURDAY AFTERNOON. A STRONG STORM OR TWO COULD BE POSSIBLE SATURDAY  
AFTERNOON ALONG AND WEST OF AN EAGLE PASS TO ROCKSPRINGS LINE.  
MARGINALLY SEVERE HAIL AND STRONG WIND GUSTS ARE THE MAIN SEVERE  
WEATHER CONCERNS. THE LATEST WPC EXCESSIVE RAINFALL OUTLOOK ALSO  
BRINGS A MARGINAL RISK FOR LOCALLY HEAVY RAINFALL TO AREAS GENERALLY  
ALONG AND WEST OF U.S. HIGHWAY 281. AT THIS TIME, MODEL  
PRECIPITATION ESTIMATES ARE NOT VERY HIGH. HOWEVER, RAINFALL RATES  
IN THE STRONGER CONVECTION COULD BRING A LOCALIZED CONCERN FOR  
BRIEF, HEAVY DOWNPOURS.  
 
LONG TERM (SATURDAY NIGHT THROUGH THURSDAY)...  
 
THUNDERSTORMS WILL BE ONGOING OUT OVER THE SOUTHERN EDWARDS PLATEAU  
AND RIO GRANDE PLAINS AT THE START OF THE PERIOD, WITH ORGANIZATION  
INTO AN MCS POSSIBLE BY EARLY SUNDAY MORNING. THE LAST FEW RUNS OF  
THE NAM CONTINUE TO INDICATE THIS SCENARIO UNFOLDING, WITH SOME  
AGREEMENT FROM GLOBAL MODELS AS WELL. HOW THINGS EVOLVE LATER ON  
SUNDAY IS MORE UNCERTAIN. WITH THE POSSIBILITY OF AN ONGOING MCS  
ADVANCING EASTWARD PAST THE HIGHWAY 281 CORRIDOR BY SUNRISE, AND  
PUSHING INTO THE COASTAL PLAINS BY MID-MORNING, ATMOSPHERIC RECOVERY  
INTO THE AFTERNOON WILL BE THE PRIMARY QUESTION. WILL OUR WESTERN  
COUNTIES HAVE ENOUGH TIME TO RELOAD FOR THE POSSIBILITY OF  
THUNDERSTORM DEVELOPMENT BY THE LATE AFTERNOON/EARLY EVENING ON  
SUNDAY? A MID TO UPPER LEVEL SHORTWAVE WILL SLIDE EASTWARD THROUGH  
THE HILL COUNTRY BY LATE SATURDAY AND EARLY SUNDAY, HELPING TO  
INCREASE THE SYNOPTIC FORCING FOR ASCENT OVER THE REGION. AT THIS  
TIME, CONDITIONS APPEAR FAVORABLE FOR STORMS TO DEVELOP OUT WEST,  
WITH DEEP LAYER SHEAR OF 40-50 KTS, STEEP MID-LEVEL LAPSE RATES OF  
7-7.5 C/KM, AND AMPLE MUCAPE OF 2500-3500 J/KG GENERALLY WEST OF  
HIGHWAY 83. IF SKIES CAN CLEAR IN TIME, AND TEMPERATURES CAN RECOVER,  
DESTABILIZATION IS POSSIBLE, AND AS A RESULT, SPC HAS INTRODUCED A  
MARGINAL RISK (LEVEL 1 OF 5) FOR AREAS ALONG AND WEST OF AN EAGLE  
PASS TO LEAKEY TO JUNCTION LINE. THE PRIMARY HAZARD WITH ANY STORMS  
THAT FORM WILL BE LARGE HAIL.  
 
TURNING OUR ATTENTION TO THE NEXT THREAT, MONDAY THROUGH WEDNESDAY  
LOOKS TO BE A RATHER ACTIVE PERIOD FOR SOUTH-CENTRAL TEXAS WITH  
MULTIPLE ROUNDS OF RAIN AND THUNDERSTORMS, SOME OF WHICH COULD BE  
STRONG TO SEVERE. A POWERFUL H5 LOW WILL MOVE OVER THE FOUR CORNERS  
LATE MONDAY, HELPING TO INCREASE FORCING FOR ASCENT OVER THE REGION.  
ALL THREE GLOBAL MODELS ARE IN GOOD AGREEMENT ON THE PLACEMENT AND  
TIMING OF THIS UPPER LEVEL TROUGH/LOW THROUGH MONDAY EVENING, BEFORE  
DIVERGING TUESDAY MORNING. WHILE THE CANADIAN/ECMWF DEPICT A SLIGHTLY  
WEAKER, MORE ELONGATED UPPER LOW OVER NORTHEASTERN COLORADO BY  
WEDNESDAY MORNING, THE GFS REMAINS THE STRONGER OF THE SOLUTIONS AND  
THE FURTHEST SOUTH, CENTERED OVER THE TEXAS PANHANDLE. ULTIMATELY,  
HOW THE OVERALL CONVECTIVE PATTERN EVOLVES IS HIGHLY DEPENDENT ON  
THE PLACEMENT OF THIS UPPER LEVEL LOW AND HOW IT IS ORIENTED. ONE  
THING ALL THREE MEMBERS HAVE IN COMMON IS A NEGATIVELY TILTED TROUGH  
BY LATE TUESDAY AND STRETCHING INTO WEDNESDAY. THIS WILL ENHANCE LIFT  
AND WAA OVER THE WARM SECTOR ON BOTH TUESDAY AND WEDNESDAY  
AFTERNOONS.  
 
AT THIS TIME, THE FEELING IS THAT SOME STRONG TO SEVERE STORMS WILL  
BE POSSIBLE MONDAY-WEDNESDAY, BUT WHERE AND EXACTLY WHEN IS MORE UP  
IN THE AIR THAN ANYTHING ELSE. THE DRYLINE WILL LIKELY REMAIN OUT  
WEST, ALLOWING QUITE A BIT OF MOISTURE TO SURGE WEST AND NORTH OVER  
THE CWA ALL THREE DAYS. ONE THING THAT COULD LIMIT SEVERE POTENTIAL  
IS THE EXTENSIVE CLOUD COVER EXPECTED OVER THE REGION WHICH COULD  
LIMIT SURFACE HEATING. HOWEVER, GIVEN SUBSTANTIAL MUCAPE OF 2000-3000  
J/KG, STEEP MID-LEVEL LAPSE RATES OF 7.5-8.5 C/KM, AND VEERING  
PROFILES, ALL MODES OF SEVERE WEATHER ARE POSSIBLE, ESPECIALLY LARGE  
HAIL, IF THE CAP CAN BE BROKEN EACH AFTERNOON.  
 
WITH REGARD TO THE THREAT FOR FLOODING, IT'S BECOMING AN INCREASINGLY  
BIGGER CONCERN AS FREEZING LEVELS WILL REMAIN QUITE HIGH, LEADING TO  
VERY EFFICIENT WARM RAIN PROCESSES. ADDITIONALLY, PRECIPITABLE WATER  
IS RUNNING SOME +2 STANDARD DEVIATIONS ABOUT THE MEAN, AND AROUND  
150% OF NORMAL FOR MID-MAY. PWATS OF 1.5-2" WILL BE COMMON SUNDAY-  
WEDNESDAY, AS THE GULF OF MEXICO REMAINS WIDE OPEN FOR BUSINESS.  
FURTHERMORE, MODEL SOUNDINGS INDICATE LONG, SKINNY CAPE AND A NEARLY  
SATURATED VERTICAL COLUMN, WHICH IS A TELLTALE SIGN OF HEAVY RAIN  
POTENTIAL. ADD THIS TO THE ALREADY SATURATED SOILS AROUND THE AREA,  
AND FLASH FLOODING POTENTIAL LOOKS TO BE GREATEST LATE TUESDAY  
THROUGH WEDNESDAY, ESPECIALLY ACROSS THE I-35 CORRIDOR AND POINTS  
EASTWARD. AT THIS TIME, WPC HAS PORTIONS OF THE HILL COUNTRY AND  
COASTAL PLAINS WITHIN A DAY 2 AND DAY 3 MARGINAL RISK FOR FLOODING  
RAIN. WIDESPREAD RAINFALL TOTALS OF 2-4" ARE POSSIBLE WITH LOCALLY  
HEAVIER AMOUNTS IN EXCESS OF 5" BY THURSDAY MORNING.  
 
BEYOND WEDNESDAY, MODELS DIVERGE SUBSTANTIALLY, AND HOW THE OVERALL  
SYNOPTIC PATTERN EVOLVES IS A BIT MORE UNCERTAIN. ONE THING THAT WE  
DO EXPECT THOUGH IS THE THREAT FOR MORE SHOWERS AND THUNDERSTORMS AS  
THE REGION REMAINS WITHIN FAVORABLE SOUTHWESTERLY FLOW ALOFT.  
 
PREV DISCUSSION... /ISSUED 110 AM CDT FRI MAY 14 2021/  
 
UPDATE...  
PLEASE SEE THE 06Z AVIATION FORECAST DISCUSSION BELOW.  
 
AVIATION...  
LOW CLOUDS CONTINUE TO DEVELOP OVER THE REGION, WITH ALL SITES  
CURRENTLY VFR. THIS WILL CHANGE OVER THE NEXT SEVERAL HOURS AS CIGS  
LOWER INTO MVFR. LOW-LEVEL MOISTURE PROFILES SUGGEST CIGS WILL REMAIN  
MVFR THROUGH MOST OF THE MORNING HOURS, THEN LIFT INTO THE 4-5K AGL  
RANGE BY EARLY AFTERNOON. SOME BRIEF CLEARING OF LOW CLOUDS MAY TAKE  
PLACE DURING THE EARLY EVENING HOURS, BUT MVFR CIGS WILL LIKELY  
RETURN AGAIN ALONG THE I-35 CORRIDOR 15/04-06Z TIME FRAME.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
AUSTIN CAMP MABRY 80 66 82 67 81 / 0 - 50 40 70  
AUSTIN BERGSTROM INTL AIRPORT 81 65 82 67 81 / 0 - 40 40 70  
NEW BRAUNFELS MUNI AIRPORT 82 67 83 69 83 / 0 - 50 40 60  
BURNET MUNI AIRPORT 80 65 79 67 79 / 0 - 50 50 60  
DEL RIO INTL AIRPORT 84 70 86 70 89 / - 20 50 40 20  
GEORGETOWN MUNI AIRPORT 80 64 82 67 80 / 0 0 40 50 70  
HONDO MUNI AIRPORT 83 67 82 68 84 / 0 20 70 60 50  
SAN MARCOS MUNI AIRPORT 82 65 82 67 81 / 0 - 50 40 60  
LA GRANGE - FAYETTE REGIONAL 82 65 85 70 81 / 0 0 30 30 70  
SAN ANTONIO INTL AIRPORT 82 68 81 69 83 / 0 10 60 50 60  
STINSON MUNI AIRPORT 84 69 83 70 84 / 0 10 60 50 60  
 

 
   
EWX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SHORT-TERM/AVIATION...PLATT  
LONG-TERM...MORRIS  
 
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