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

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FXUS64 KEWX 292011
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
311 PM CDT SUN MAY 29 2016

.SHORT TERM (Tonight through Monday Night)...
THE PRIMARY FOCUS OF THE SHORT TERM WILL BE THE PROSPECT OF
MULTIPLE ROUNDS OF ADDITIONAL STORM SYSTEMS TONIGHT AND TOMORROW
NIGHT.

FOR TONIGHT...YET ANOTHER SHORTWAVE PERTURBATION IN THE H5 RIDGE
OVER TEXAS WILL PASS OVER THE BIG BEND AND EDWARDS PLATEAU TONIGHT
PROVIDING UPPER LEVEL SUPPORT FOR ANOTHER ROUND OF DRY LINE
CONVECTION IN THE BIG BEND REGION AND OFF THE MEXICAN MOUNTAINS.
SIMILAR TO THE LAST COUPLE DAYS...Instability IS QUITE HIGH AND
EFFECTIVE SHEAR VALUES ARE 40+ KTS WITHIN A VERY WARM AND MOIST
AIR MASS. THUS INITIALLY ISOLATED SUPERCELLS ARE POSSIBLE WEST OF
THE CWA AND RIO GRANDE AND ORGANIZE INTO A CONVECTIVE CLUSTER OR
MCS BY THIS EVENING. WHILE THIS WAS AGREED UPON BY MOST HI-RES
MODELS AND SYNOPTIC MODELS THIS MORNING...THE LATEST SUITE OF HI-
RES RUNS ARE NOT AS BULLISH ON QPF GENERATION. EVEN WITH THE
UNCERTAINTY FOR QPF AMOUNTS...FLASH FLOOD GUIDANCE IS VERY
LOW...LESS THAN 1 INCH IN SOME CASES...FOR LOCATIONS IN THE HILL
COUNTRY THAT RECEIVED MULTIPLE INCHES OF RAIN LAST NIGHT.

IN ADDITION...AN MCS FROM THE NORTH IS PROJECTED TO PUSH SOUTHWARD
ACROSS CENTRAL TEXAS OVERNIGHT AS WELL. THERE IS MORE UNCERTAINTY
WITH THIS POSSIBILITY AS MANY MODELS DETERIORATE THIS LINE AS IT
APPROACHES THE CWA. HOWEVER...IF IT IS ABLE TO MAKE IT FAR ENOUGH
SOUTH...ADDITIONAL RAINFALL COULD IMPACT THE HILL COUNTRY TOWARDS
12Z TOMORROW MORNING.

AS A RESULT...A FLASH FLOOD WATCH WAS ISSUED DUE TO THE HIGH
VULNERABILITY OF THE HILL COUNTRY AND EDWARDS PLATEAU TO FLASH
FLOODING...EVEN WITH RELATIVELY LOW AMOUNTS OF QPF INDICATED IN
THE MODELS.

ANOTHER SIMILAR SET UP IS POSSIBLE TOMORROW NIGHT AS YET ANOTHER
SHORTWAVE PASSAGE IS EVIDENT IN GFS/EURO/CANADIAN. IF SO...THE
FLASH FLOOD WATCH MAY NEED TO BE EXTENDED THROUGH TUESDAY AS WELL.

&&

.LONG TERM (Tuesday through Sunday)...
THE LONG TERM FORECAST HAS NOT CHANGED SUBSTANTIALLY AS A STRONG
COLD FRONT IS STILL PROGGED TO MOVE THROUGH WEDNESDAY AND PRODUCE
WIDESPREAD HEAVY RAINFALL ACROSS MUCH OF CENTRAL AND SOUTH CENTRAL
TEXAS. THEREFORE THE FLASH FLOOD THREAT WILL CONTINUE THROUGH AT
LEAST MID WEEK.

THE MOST NOTABLE CHANGE IN THE MID RANGE FORECAST IS THE
PERSISTENT LIGHT TO MODERATE QPF GENERATION DUE TO THE MAIN H5
LOW DEEPENING OVERTOP OF SOUTH CENTRAL TEXAS THURSDAY AND SLOWLY
MOVING OFF LATE FRIDAY. WHILE THE COLD FRONT PASSAGE SHOULD
ELIMINATE THE POTENTIAL FOR ADDITIONAL HEAVY RAINS...EVEN THE MORE
MEAGER SHOWER GENERATION THURSDAY AND FRIDAY UNDERNEATH THE LOW
MAY SERVE TO PROLONG WHATEVER FLASH FLOODING IMPACTS OCCUR
THROUGHOUT THE WEEK.

THE POP CHANCES MAY FINALLY BEGIN TO WANE INTO NEXT WEEKEND AS
THE MAIN UPPER LOW FINALLY PUSHES EAST. HOWEVER...12Z LONG RANGE
MODEL SUITE SHOWS SOME DISAGREEMENT IN THIS EVOLUTION AS THE
GFS/CANADIAN/DGEX PUSH THE LOW INTO LOUISIANA BY SUNDAY...BUT THE
EURO LAGS THE LOW OVER SOUTHEAST TEXAS THROUGH MONDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              71  85  70  85  70 /  30  30  30  50  40
Austin Bergstrom Intl Airport  70  85  69  84  70 /  30  30  30  50  40
New Braunfels Muni Airport     71  86  70  85  71 /  20  30  30  50  40
Burnet Muni Airport            69  83  68  82  68 /  30  30  30  50  50
Del Rio Intl Airport           72  87  72  88  71 /  60  30  50  40  40
Georgetown Muni Airport        69  84  68  83  69 /  30  30  30  50  50
Hondo Muni Airport             72  86  71  85  71 /  40  30  40  50  40
San Marcos Muni Airport        70  85  69  84  70 /  20  30  30  50  30
La Grange - Fayette Regional   71  86  70  85  71 /  10  20  20  40  20
San Antonio Intl Airport       72  86  71  84  71 /  30  30  30  50  40
Stinson Muni Airport           73  87  72  86  72 /  30  30  30  40  40

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from 7 PM CDT this evening through Monday
afternoon for the following counties: Bandera...Blanco...Edwards...
Gillespie...Kendall...Kerr...Kinney...Medina...Real...Uvalde...Val
Verde.

&&

$$

Mesoscale/Aviation...Runyen
Synoptic/Grids...TB3
Public Service/Data Collection...30


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