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000
FXUS64 KSJT 211713
AFDSJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
1213 PM CDT TUE MAY 21 2013

.DISCUSSION...
SEE AVIATION DISCUSSION BELOW...

&&

.AVIATION...
A COLD FRONT WAS LOCATED ALONG A LINE FROM SOUTH OF STERLING
CITY...TO JUST SOUTH OF ABILENE...AND MOVING SOUTH. AS THE FRONT
MOVES THROUGH...EXPECT WINDS TO BECOME NORTH AT 12 TO 20
KNOTS...WITH HIGHER GUSTS. IN ADDITION...SHOWERS AND THUNDERSTORMS
WILL BE POSSIBLE WITH THE COLD FRONT...ESPECIALLY AT KABI IN THE
NEXT COUPLE OF HOURS...AND KBBD AND KJCT BY LATE AFTERNOON. BRIEF
MVFR CONDITIONS WILL BE POSSIBLE WITHIN ANY THUNDERSTORMS.
OTHERWISE...EXPECT WINDS TO BECOME LIGHT OVERNIGHT WITH VFR
CONDITIONS. STRATUS DEVELOPMENT WILL ONCE AGAIN BE POSSIBLE AFTER
MIDNIGHT WEDNESDAY...WITH MVFR CEILINGS POSSIBLE.

&&

.PREV DISCUSSION... /ISSUED 1053 AM CDT TUE MAY 21 2013/

UPDATE...
TO INCREASE POPS AND ADD THE TORNADO WATCH FOR PARTS OF THE
AREA...

DISCUSSION...
A COLD FRONT WAS LOCATED FROM SOUTH OF SWEETWATER...TO JUST NORTH
OF ABILENE...TO NEAR ALBANY. FARTHER SOUTH...A DRYLINE WAS
LOCATED ACROSS OUR WESTERN COUNTIES AND ADVANCING EAST. SHOWERS
AND THUNDERSTORMS ARE DEVELOPING ALONG AND JUST BEHIND THE COLD
FRONT...ACROSS THE BIG COUNTRY. THIS TREND IS EXPECTED TO CONTINUE
WITH SHOWERS AND THUNDERSTORMS SPREADING INTO MUCH OF THE EASTERN
HALF OF WEST CENTRAL TEXAS THROUGHOUT THE AFTERNOON. SOME OF THE
STORMS COULD BECOME STRONG TO SEVERE...WITH LARGE HAIL...DAMAGING
WINDS AND A FEW TORNADOES POSSIBLE. A TORNADO WATCH IS IN EFFECT
FOR THE EASTERN HALF OF THE AREA UNTIL 7 PM CDT. I INCREASED
POPS...QPF AND CLOUD COVER ACROSS THESE AREAS. IN ADDITION...GIVEN
THE CURRENT POSITION OF THE COLD FRONT...I HAVE LOWERED TEMPERATURES
ACROSS THE AREA...ESPECIALLY THE NORTHERN HALF OF THE REGION WHICH
WILL BE BEHIND THE FRONT AND CLOUD COVER WILL BE MOST EXTENSIVE.
NO OTHER CHANGES NEEDED AT THIS TIME.

PREV DISCUSSION... /ISSUED 641 AM CDT TUE MAY 21 2013/

DISCUSSION...
SEE AVIATION SECTION.

AVIATION...
A COLD FRONT AND STRONG UPPER LEVEL DISTURBANCE WILL BE FOCUSING
MECHANISMS FOR THUNDERSTORM DEVELOPMENT TODAY AND THIS EVENING...
ACROSS NORTHERN AND EASTERN SECTIONS OF WEST CENTRAL TEXAS.

LOW CLOUDS DEVELOPING EARLY THIS MORNING ALONG THE EDGES OF OUR
FORECAST AREA. TO THE NORTH THE LOW CLOUD DEVELOPMENT IS JUST
BEHIND A COLD FRONTAL BOUNDARY. TO THE SOUTHEAST...LOW CLOUDS
ARE EXPANDING IN COVERAGE FROM THE HILL COUNTRY INTO OUR FAR
SOUTHEASTERN COUNTIES. CARRYING TEMPO GROUPS THIS MORNING FOR MVFR
CEILINGS AT KABI...JCT AND KBBD. SCATTERED SHOWERS AND THUNDERSTORMS
COULD DEVELOP LATER THIS MORNING ACROSS THE BIG COUNTRY...AS THE
COLD FRONT MOVES SOUTH ACROSS THAT AREA. CARRYING VCTS AT KABI
AFTER 16Z. ADDITIONAL THUNDERSTORM DEVELOPMENT IS EXPECTED THIS
AFTERNOON ALONG THE COLD FRONT ACROSS THE EASTERN BIG COUNTRY...
HEARTLAND AND NORTHWEST HILL COUNTRY AREAS. CARRYING A VCTS GROUP
AT KBBD AFTER 20Z. HAVE A POTENTIAL FOR SEVERE STORMS WITH STRONG
WINDS AND HAIL. IN ADDITION...LOCALLY HEAVY RAINFALL WITH REDUCTIONS
IN CEILING AND VISIBILITY WILL BE POSSIBLE WHERE THE STORMS OCCUR.

SOUTH TO SOUTHWEST WINDS WILL SHIFT TO THE NORTH WITH THE COLD
FRONTAL PASSAGE TODAY. NORTH WINDS EARLY TONIGHT WILL DIMINISH AND
BECOME LIGHT AND VARIABLE OVERNIGHT. CLEARING SKIES EXPECTED
TONIGHT. HAVE SOME UNCERTAINTY ON WHETHER LOW CLOUD DEVELOPMENT
WILL OCCUR TOWARD MORNING ACROSS OUR EASTERN AND SOUTHEASTERN
COUNTIES. LEAVING THE MENTION OUT FOR NOW.

PREV DISCUSSION... /ISSUED 426 AM CDT TUE MAY 21 2013/

TODAY AND TONIGHT...
THE MAIN CONCERN IN THE SHORT TERM IS WITH SEVERE WEATHER
POTENTIAL ACROSS OUR EASTERN COUNTIES THIS AFTERNOON AND EVENING.

A FAIRLY STRONG SHORTWAVE TROUGH /CURRENTLY OVER THE SOUTHERN
ROCKIES/ WILL MOVE EAST INTO THE SOUTHERN PLAINS AND NORTH TEXAS
TODAY. A SURFACE COLD FRONT WILL PUSH SOUTH ACROSS OUR NORTHWESTERN
COUNTIES THIS MORNING...AND THROUGH OUR CENTRAL AND SOUTHERN
COUNTIES THIS AFTERNOON. THIS FRONT SHOULD EXIT OUR SOUTHEASTERN
COUNTIES BY 7-8 PM THIS EVENING.

AS LIFT FROM THE APPROACHING SHORTWAVE TROUGH IMPINGES ON THE
AREA...SOME OF THE MODELS INDICATE CONVECTIVE DEVELOPMENT ACROSS
PARTS OF THE BIG COUNTRY LATER THIS MORNING ALONG AND BEHIND THE
COLD FRONT. HAVE ADDED 20-30 POPS ACROSS OUR NORTHEASTERN COUNTIES
THIS MORNING FOR THIS POSSIBILITY. WITH INCREASING VERTICAL SHEAR
AND STEEP MID-LEVEL LAPSE RATES...CANNOT RULE OUT THE POSSIBILITY OF
A FEW STRONG ELEVATED STORMS WITH HAIL THIS MORNING. THE MAIN
SEVERE WEATHER POTENTIAL...HOWEVER...IS THIS AFTERNOON AND EVENING
ACROSS OUR EASTERN COUNTIES...WHEN FAVORABLE COMBINATION OF VERTICAL
SHEAR AND INSTABILITY WILL BE SUPPORTIVE OF ORGANIZED SEVERE STORMS.
STORMS ARE EXPECTED TO DEVELOP ALONG THE SOUTHWARD-MOVING COLD
FRONT. COULD HAVE DISCRETE SUPERCELLS INITIALLY...BEFORE STORMS
ORGANIZE INTO A QUASI-LINEAR MCS. OUR HEARTLAND AND NORTHWEST HILL
COUNTRY COUNTIES LOOK TO BE ON THE SOUTHWEST END OF THE ANTICIPATED
QUASI-LINEAR MCS. CARRYING THE HIGHEST POPS ACROSS OUR HEARTLAND
AND NORTHWEST HILL COUNTRY COUNTIES.

THE DRYLINE HAS RETREATED WEST OF OUR FORECAST AREA. THE 00Z NAM
AND GFS BOUNDARY LAYER FIELDS SUGGEST THAT THE DRYLINE COULD MAKE
AN INTRUSION INTO THE WESTERN CONCHO VALLEY AND NORTHERN EDWARDS
PLATEAU THIS AFTERNOON BEFORE BEING OVERTAKEN BY THE COLD FRONT.
WITH LESS CLOUD COVER EXPECTED ACROSS THESE AREAS ALONG WITH A
THERMAL RIDGING PATTERN AT 850 MB...TEMPERATURES COULD WELL REACH
THE 90-95 DEGREE RANGE FOR HIGHS BEFORE THE COLD FRONT ARRIVES.
TEMPERATURES ARE EXPECTED TO BE APPRECIABLY COOLER ACROSS THE BIG
COUNTRY...WHERE THE COLD FRONT ARRIVES EARLIER IN THE DAY AND
WHERE GREATER CLOUD COVER SHOULD DEVELOP.

THUNDERSTORM ACTIVITY WILL END LATER THIS EVENING ACROSS OUR
FAR SOUTHEASTERN COUNTIES AS THE COLD FRONT CONTINUES TO MOVE
SOUTH. IN THE WAKE OF THE FRONTAL PASSAGE...NORTH WINDS WILL
DIMINISH AND BECOME LIGHT OVERNIGHT...AS WEAK SURFACE HIGH
PRESSURE SETTLES SOUTH INTO OUR AREA. WITH THIS SETUP TEMPERATURES
WILL BE COOLER TONIGHT...AND GOING WITH OVERNIGHT LOWS IN THE 60-65
DEGREE RANGE. WHILE THE GFS MOS LOOKS TOO AGGRESSIVE /AT THIS TIME/
WITH THE RADIATIONAL COOLING FOR TONIGHT...OUR FORECAST LOWS MAY
NEED TO BE TWEAKED DOWN FURTHER.

WEDNESDAY THROUGH FRIDAY...
BOTH THE GFS AND THE ECMWF SHOW A SHORTWAVE RIDGE DEVELOPING IN
THE UPPER LEVELS ACROSS WEST CENTRAL TEXAS. BUT THEY ALSO SHOW
SHOWERS AND STORMS ALONG THE WESTERN EDGE ACROSS MUCH OF WEST
TEXAS...WITH THE STORMS TRYING TO MOVE EAST INTO PORTIONS OF WEST
CENTRAL TEXAS EACH EVENING. WILL KEEP THE SLIGHT CHANCE POPS IN
THE FORECAST AS IS FOR NOW.

SATURDAY THROUGH TUESDAY...
UPPER LEVEL RIDGE INTENSIFIES AND BROADENS...LEAVING WEST CENTRAL
TEXAS IN A HOT AND DRY PATTERN. 850 MB WINDS REMAIN OUT OF THE
SOUTH AND SOUTHEAST...WHICH HELPS MITIGATES THE TEMPERATURES A FEW
DEGREES...BUT STILL LOOKING LIKE READINGS WELL INTO THE 90S FOR
MEMORIAL DAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
ABILENE  60  91  69  92  70 /  10  10  10  10  20
SAN ANGELO  61  94  70  94  69 /  10   5  10  10  20
JUNCTION  63  93  70  93  68 /  20   5   5  10  10

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

DANIELS