168
FXUS64 KSJT 050030
AFDSJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
730 PM CDT SAT JUL 4 2009
UPDATE
INCREASE POPS FOR THE BIG COUNTRY.
DISCUSSION
THUNDERSTORM COMPLEX MOVING INTO BIG COUNTRY MOVING EAST THIS
EVENING. PER CONVECTIVE TRENDS...INCREASED POPS IN THE BIG COUNTRY
TO LIKELY IN MOST AREAS...ESPECIALLY ALONG/NORTH OF I-20. ADDED A
SLIGHT CHANCE OF STORMS FOR IRION COUNTY AS A FEW STORMS DEVELOP
IN REAGAN COUNTY.
PREV DISCUSSION
/ISSUED 655 PM CDT SAT JUL 4 2009/
DISCUSSION...
AVIATION DISCUSSION FOLLOWS.
AVIATION...
AREA OF THUNDERSTORMS PRODUCED BY PRE-FRONTAL TROF AHEAD OF
FRONTAL BOUNDARY IS NOW MOVING INTO WEST CENTRAL TEXAS. THESE
STORMS WILL LIKELY IMPACT THE BIG COUNTRY THROUGH THIS EVENING.
FOR THIS REASON...INCLUDED MENTION OF THUNDERSTORMS FOR KABI.
STRONG WINDS TO NEAR 45KNOTS NEAR THE THUNDERSTORMS...PEA SIZE
HAIL...AND LOTS OF LIGHTING.
PREV DISCUSSION... /ISSUED 538 PM CDT SAT JUL 4 2009/
UPDATE...
INCREASED BIG COUNTRY POPS.
DISCUSSION...
LARGE GROUP OF THUNDERSTORMS...FROM MIDLAND TO SNYDER TO CHILDRESS
MOVING NORTHEAST THIS AFTERNOON. STORM COMPLEX MAY TAKE ON A MORE
EASTERLY MOVEMENT AS THEY BECOME ORGANIZED. UPDATED TO INCREASE
POPS...MAINLY NORTH OF I-20.
PREV DISCUSSION... /ISSUED 224 PM CDT SAT JUL 4 2009/
SHORT TERM...
LATEST VISIBLE SATELLITE SHOWS A CU FIELD DEVELOPING ACROSS THE BIG
COUNTRY AHEAD OF A WEAK COLD FRONT...WHICH CURRENT OBS SHOW IS
LOCATED FROM CORVINA IN THE TEXAS PANHANDLE TO NEAR TOPEKA
KANSAS...WITH SCATTERED SHOWERS AND THUNDERSTORMS DEVELOPING ALONG
AND AHEAD OF THE FRONT ACROSS THE TEXAS PANHANDLE BUT DON'T EXPECT ANY
OF THIS STORM ACTIVITY TO MOVE INTO THE BIG COUNTRY UNTIL LATER
THIS EVENING AND OVERNIGHT HOURS...WITH THE MOST LIKELY AREA BEING
NORTH OF THE INTERSTATE 20 CORRIDOR. THE 12Z MODELS RUNS WERE MUCH
DRIER FOR TONIGHT AND SUNDAY. SO HAVE TRIMMED POPS TONIGHT...WITH
ONLY 30 TO 40 POPS ACROSS THE NORTHERN BIG COUNTRY NORTH OF
INTERSTATE 20 AND ONLY 20 POPS ACROSS THE REMAINDER OF THE BIG
COUNTRY.
FOR SUNDAY OUTFLOW BOUNDARIES FROM TONIGHT'S ACTIVITY AND THE FRONT
WILL BE A FOCUS FOR THUNDERSTORM ACTIVITY SUNDAY AFTERNOON. THE 12Z
MODEL RUNS WERE SLOWER WITH FROPA THAN THE 06Z MODEL RUNS.THE NAM
HAS THE FRONT APPROACHING THE INTERSTATE 20 CORRIDOR LATE MORNING
THE CONCHO VALLEY AND HEARTLAND MID AFTERNOON AND THE INTERSTATE 10
CORRIDOR SUNDAY EVENING...WHILE THE GFS IS A LITTLE BIT FASTER...FOR
NOW HAVE GONE WITH THE SLOWER NAM SOLUTION. GIVEN THE UNCERTAINTY
DRIER MODEL SOLUTIONS AND THE SCATTERED COVERAGE EXPECTED...HAVE
LOWERED POPS ON SUNDAY INTO THE 20 TO 30 PERCENT RANGE...EXCEPT
ACROSS THE NORTHEASTERN BIG COUNTRY AND HEARTLAND WHERE HAVE 40
POPS.
THE TIMING OF FROPA AND CONVECTION WILL BE A FACTOR IN SUNDAY'S
TEMPERATURES...MORE CONVECTION AND FASTER FROPA MEANS
COOLER TEMPERATURES...WHILE SLOWER FROPA AND LESS CONVECTION MEANS
WARMER AFTERNOON TEMPERATURES. THE GFS IS COOLER THAN THE NAM AS THE
GFS IS FASTER WITH FROPA AND MORE AGGRESSIVE WITH CONVECTION THAN
THE NAM...AS OF NOW I HAVE TRENDED TOWARDS THE NAM FROPA TIMING AND
CONVECTION COVERAGE...SO ALSO HAVE LEANED TOWARDS NAM TEMPERATURES...WITH
AFTERNOON HIGHS IN THE UPPER 80S TO A FEW LOWER 90S ACROSS THE BIG
COUNTRY AND MID TO UPPER 90S ELSEWHERE ACROSS WEST CENTRAL TEXAS FOR
SUNDAY AFTERNOON.
28
LONG TERM...
FORECAST CHALLENGES IN THE LATER PERIODS FOCUS ON CONVECTIVE
CHANCES EARLY THIS WEEK.
UPPER LEVEL RIDGING THAT HAS BEEN IN PLACE OVER TX THE PAST COUPLE
OF DAYS WILL BE BREAKING DOWN AND SHIFTING WEST TEMPORARILY AS A
TROUGH DIGS SOUTHEAST ACROSS THE MID MISSISSIPPI VALLEY. AN
ASSOCIATED FRONTAL BOUNDARY NOW DROPPING SOUTH OVER THE
CENTRAL/SOUTHERN PLAINS WILL EVENTUALLY SETTLE SOUTH ACROSS TX
THIS WEEKEND AND WASH OUT EARLY NEXT WEEK. THE FRONT WILL BRING
CHANCES FOR SHOWERS/STORMS TO W CNTRL TX WITH THE BETTER CHANCES
ON SUNDAY INTO SUNDAY NIGHT. SIMILAR TO WHAT OCCURRED EARLY THIS
WEEK...A DEEP LAYER MOIST AXIS WILL REMAIN IN PLACE OVER THE
REGION LONG AFTER THE FRONT WASHES OUT. WITH THE MOIST AXIS IN
PLACE...SCATTERED SHOWERS AND STORMS WILL CONTINUE TO AFFECT THE
REGION THROUGH TUESDAY. WITH NORTHWEST FLOW IN PLACE EARLY NEXT
WEEK...THERE IS ALSO A SMALL CHANCE THAT AN MCS ORIGINATING OVER
THE SOUTHERN HI PLAINS COULD MOVE SOUTHEAST INTO THE FCST AREA.
IN THE GRIDS...WILL KEEP THE HIGHER CHC POPS SUNDAY NIGHT INTO
MONDAY NEAR THE FRONT...AND THEN GRADUALLY TREND THEM DOWN THRU
TUESDAY.
THE UPPER LEVEL RIDGE IS THEN EXPECTED TO REDEVELOP OVER THE
CENTRAL/SOUTHERN ROCKIES AND HI PLAINS DURING THE LATTER PART OF
NEXT WEEK...WITH A RETURN TO TYPICAL HOT AND DRY JULY WEATHER. THE
GFS/ECMWF SUGGEST THE RIDGE WILL BUILD BACK EVEN STRONGER...WITH
PROGGED 500MB HEIGHTS APPROACHING 600 DECAMETERS. UPPER HEIGHTS BEGIN
TO BUILD OVER W CNTRL TX AS SOON AS WEDNESDAY AND CONTINUE INTO
THURSDAY. THE 500MB HIGH IS THEN EXPECTED TO GRADUALLY BECOME
ORIENTED WEST TO EAST OVER THE CENTRAL PLAINS TOWARD NEXT WEEKEND
WITH THE UPPER FLOW TRANSITIONING FROM NORTHEAST TO EAST OVER TX.
HIGH TEMPS WILL RISE TO NEAR 100 DEGREES FOR THE LATTER HALF OF
THE WEEK...BUT WILL GRADUALLY BACK OFF SOME NEXT WEEKEND AS THE
COOLER EASTERLY FLOW SETS IN AND THE 850MB THERMAL RIDGE SHIFTS
NORTH OF THE FCST AREA.
LACY
PRELIMINARY POINT TEMPS/POPS
ABILENE 73 88 69 90 70 / 60 40 30 30 20
SAN ANGELO 72 93 69 91 69 / 10 30 40 30 20
JUNCTION 74 97 71 93 73 / 10 20 40 30 20
SJT WATCHES/WARNINGS/ADVISORIES
NONE.
99/04/99
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