000
FXUS64 KSJT 191104
AFDSJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
604 AM CDT SUN MAY 19 2013


.DISCUSSION...
/SEE BELOW FOR AVIATION DISCUSSION/

&&

.AVIATION...
KSJT AND KDYS RADAR VAD INDICATED A 45-50 KT LOW LEVEL JET AT
3000 MSL AT 11Z. WILL MENTION LOW LEVEL WIND SHEAR AT KABI AND
KSJT 14-15Z...AS WINDS WERE LIGHT AT THE SURFACE. STRONG GUSTY
WINDS UP TO 28 KTS ARE EXPECTED BY MID MORNING AT KABI AND KSJT
AS THE WINDS PARTIALLY MIX DOWN. STRATUS OTHERWISE WAS
APPROACHING KJCT AT 11Z...AND WILL PUT A MVFR BROKEN CIG UNTIL
15Z. A FEW THUNDERSTORMS POSSIBLE NEAR A DRYLINE AT KABI AND KBBD
LATE THIS AFTERNOON...BUT POTENTIAL IS TOO SMALL TO PUT IN TAFS.
MVFR STRATUS MAY AFFECT SOUTHERN TERMINALS LATE TONIGHT...WITH
CONTINUED MOISTURE FLOW FROM THE GULF.

&&

.PREV DISCUSSION... /ISSUED 352 AM CDT SUN MAY 19 2013/

SHORT TERM...
DRYLINE WILL BE MOVING ALONG A SONORA...SAN ANGELO...ABILENE...
THROCKMORTON LINE LATE THIS AFTERNOON. GFS SB CAPES ARE OVER 3000
J/KG WITH 0 TO 6 KM SHEARS OF 40 KTS...JUST EAST OF THE DRYLINE.
IF STORMS DO DEVELOP...THEY COULD RAPIDLY BECOME SEVERE. STILL
QUESTIONABLE IN HOW MUCH CAPPING WILL EXIST...BUT WITH STRONG
HEATING AND LOW LEVEL CONVERGENCE ALONG THE DRYLINE...SHOULD SEE
AT LEAST ISOLATED AFTERNOON THUNDERSTORM DEVELOPMENT. STORM
ACTIVITY SHOULD PERSIST INTO THE EVENING HOURS BEFORE WEAKENING.
SPC DAY 1 OUTLOOK HAS A SLIGHT CHANCE OF SEVERE THUNDERSTORMS...
EAST ALONG AND EAST OF A HASKELL...ABILENE...COLEMAN...BROWNWOOD
LINE. LARGE HAIL...DAMAGING WINDS ARE THE MAIN THREATS. AN
ISOLATED TORNADO POSSIBLE...BUT HIGH BASES SHOULD LIMIT THE
TORNADO THREAT. WENT CLOSE TO SATURDAYS HIGH TEMPERATURES FOR
TODAY. OVERNIGHT LOWS HOWEVER SHOULD BE A COUPLE DEGREES LOWER
THAN THIS MORNING...DUE TO LOWER WIND SPEEDS AND LESS MIXING.

04

LONG TERM...
AFTERNOON/EVENING SHOWERS AND THUNDERSTORMS WILL REMAIN IN THE
FORECAST WITH UNSEASONABLY WARM TEMPERATURES EXPECTED THROUGHOUT
THE DURATION OF THE LONG TERM PERIOD.

NOCTURNAL STRATUS IS EXPECTED ACROSS THE SOUTHEAST QUADRANT OF THE
CWA MONDAY MORNING...ERODING BEFORE 12Z UNDER STRONG INSOLATION.
THE DRYLINE WILL MIX EAST DURING THE AFTERNOON AND IS EXPECTED TO
SET UP IN THE VICINITY OF AN ABILENE TO SAN ANGELO LINE. TEMPS
WILL AGAIN BE IN THE MID TO UPPER 90S /WITH A FEW LOCATIONS
APPROACHING 100 DEGREES. THE STRONG DIABATIC HEATING...STEEP MID
LEVEL LAPSE RATES AND DEEP MOISTURE /EAST OF THE DRYLINE/ WILL
YIELD MLCAPE VALUES NEAR OR ABOVE 3000 J/KG. I ANTICIPATE DEEP
LAYER SHEAR TO BE MORE THAN SUFFICIENT FOR SUPERCELLULAR
CONVECTION AS WINDS IN THE MOIST SECTOR BACK TO THE SOUTHEAST BY
LATE AFTERNOON. BOTH THE GFS AND NAM PROG 0-6KM SHEAR VALUES OF
35-40 KTS BY 00Z MONDAY EVENING.

LARGE SCALE FORCING WILL BE STRONGEST ACROSS THE NORTHERN HALF OF
THE AREA...MEANING THE CAP IS EXPECTED TO HOLD FOR THE MOST PART
IN THE SOUTHERN ZONES. I THINK CONVECTION WILL GENERALLY REMAIN
ISOLATED WITH THE BEST CHANCE BEING NORTH OF THE COLORADO RIVER.
WITH THE PRIMARY CONVECTIVE MODE BEING SUPERCELLS...THE MAIN
THREATS WILL BE LARGE HAIL AND DAMAGING WINDS. HODOGRAPHS LOOK
REASONABLE FOR A SMALL TORNADO THREAT AS WELL...ESPECIALLY AS WE
MOVE INTO THE EVENING HOURS AND THE NOCTURNAL LOW LEVEL JET
INTENSIFIES. HOWEVER...ONCE WE LOSE DAYTIME HEATING...CONVECTION
IS EXPECTED TO WANE AS IT WILL BE MAINLY DIURNALLY DRIVEN.

A SIMILAR SETUP IS EXPECTED ON TUESDAY WITH TEMPERATURES AGAIN IN
THE MID/UPPER 90S. HOWEVER...PROLONGED SOUTHWEST FLOW ALOFT WILL
CONTRIBUTE TO A STRENGTHENING ELEVATED MIXED LAYER WHICH WILL
RESULT IN A STRONGER CAP ACROSS THE FORECAST AREA. I STILL THINK
WE WILL SEE GENERALLY ISOLATED CONVECTION DURING THE AFTERNOON
WITH PRECIP CHANCES LINGERING THROUGH MOST OF THE NIGHT AS A WEAK
SURFACE BOUNDARY SAGS SOUTH TOWARD THE I-10 CORRIDOR. THE FORECAST
IS DRY FOR WEDNESDAY AS THE TROUGH CURRENTLY LOCATED TO OUR WEST
FINALLY MOVES EAST OF THE AREA...REPLACED BY SHORTWAVE RIDGING.
THE DRYLINE WILL LIKELY REMAIN TO OUR WEST FOR A FEW DAYS. THE
ADDED LOW LEVEL MOISTURE AND WESTERN SHIFT OF THE LOWER
TROPOSPHERIC THERMAL RIDGE WILL LIKELY RESULT IN TEMPS UNDER 100
DEGREES WEDNESDAY THROUGH FRIDAY. HOWEVER...A FEW LOCATIONS MAY
SNEAK ABOVE THE CENTURY MARK.

THIS HOT AND DRY PERIOD WILL CONTINUE THROUGH FRIDAY AFTERNOON BUT
DIURNAL CONVECTION ALONG THE DRYLINE WILL POTENTIALLY MOVE INTO
THE BIG COUNTRY FRIDAY NIGHT. I INSERTED A SLIGHT CHANCE OF
THUNDERSTORMS TO HIGHLIGHT THIS POTENTIAL. THE MODELS ARE IN
DISAGREEMENT REGARDING THE WEEKEND PATTERN WITH THE GFS SHOWING
WEAK NORTHWEST FLOW AND THE ECMWF SUGGESTING CONTINUING SOUTHWEST
TO WEST FLOW. THE LATER WOULD BE PREFERABLE FOR PRECIP CHANCES BUT
CONFIDENCE IS LOW WITH EITHER AT THIS TIME.

JOHNSON

FIRE WEATHER...
A DRYLINE WILL BE MOVING EAST ALONG A SONORA...SAN ANGELO...
ABILENE...THROCKMORTON LINE LATE THIS AFTERNOON. ELEVATED FIRE
WEATHER CONDITIONS ARE EXPECTED ALONG AND WEST OF THE DRYLINE...
AS RH VALUES FALL INTO THE TEENS. AREAS IN THE BIG COUNTRY...WEST
OF AN ABILENE TO THROCKMORTON LINE...WILL SEE NEAR CRITICAL
VALUES...AS 20 FOOT SOUTHWEST WINDS OF 15 TO 20 MPH DEVELOP.
SIMILAR CONDITIONS ARE EXPECTED AGAIN MONDAY...HOWEVER WINDS WILL
BE 2 TO 4 MPH LOWER.

04

&&

.PRELIMINARY POINT TEMPS/POPS...
ABILENE  97  69  97  69  90 /  20  20  10  10  20
SAN ANGELO 100  69  99  70  94 /   5   5  10  10  10
JUNCTION  95  70  96  72  95 /  10  10  20  20  20

&&

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

$$

99/99/04