Area Forecast Discussion
Issued by NWS Dallas/Fort Worth, TX

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000
FXUS64 KFWD 262305 AAA
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
605 PM CDT FRI SEP 26 2014

.AVIATION...
VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH 06Z SUNDAY.

AN UPPER LEVEL LOW THAT WAS OVER SOUTHWEST TEXAS AT 6 PM...WILL
MOVE EAST DURING THE NEXT 24 HOURS. AS THIS SYSTEM TREKS ACROSS
SOUTH CENTRAL TEXAS SATURDAY...THERE WILL BE LOW CHANCES OF
SHOWERS AND ISOLATED THUNDERSTORMS SOUTH OF A COMANCHE /KMKN/ TO
HILLSBORO /KINJ/ TO ATHENS /KF44/ LINE. THE RAIN CHANCES AT THE
WACO TAF SITE ARE TOO LOW TO INCLUDE IN THE FORECAST. EXPECT EAST
TO SOUTHEAST WINDS AT 5 TO 10 KNOTS TO PREVAIL.

58

&&


.PREV DISCUSSION... /ISSUED 334 PM CDT FRI SEP 26 2014/

EARLY AFTERNOON WATER VAPOR SATELLITE IMAGERY SHOWED UPPER LEVEL
LOW PRESSURE SYSTEMS OVER SOUTHWEST TEXAS...NORTHERN MISSOURI...
AND JUST OFF THE SOUTH CENTRAL CALIFORNIA COAST. THE SOUTHWEST
TEXAS UPPER LOW HAD NOT MOVED MUCH FROM THE MORNING UPDATE
FORECAST DISCUSSION...BUT WEAK LARGE SCALE FORCING FOR ASCENT WAS
STILL EVIDENT EAST OF THIS FEATURE...OVER WEST CENTRAL TEXAS AND
THE HILL COUNTRY. 12Z UPPER AIR ANALYSIS INDICATED THAT THE
SOUTHWEST TEXAS AND NORTHERN MISSOURI UPPER LOWS WERE EMBEDDED
WITHIN A LARGER SCALE UPPER RIDGE AXIS IN PLACE OVER THE EASTERN
TWO THIRDS OF THE CONUS...WHICH EXPLAINS WHY THEY ARE NOT MOVING
MUCH. THE UPPER LOW/STRONG SHORTWAVE TROUGH JUST WEST OF
CALIFORNIA WAS LOCATED AT THE BASE OF A LARGER SCALE TROUGH THAT
WAS MOVING SLOWLY EAST OVER THE WESTERN THIRD OF THE CONUS.

FOR THE SHORT TERM FORECAST...BASICALLY THROUGH SUNSET...LEFT LOW
CHANCE POPS FOR SHOWERS AND ISOLATED THUNDERSTORMS IN PLACE FOR
LOCATIONS WEST OF A LINE FROM JACKSBORO TO GATESVILLE TO CAMERON.
WATER VAPOR AND VISIBLE SATELLITE IMAGERY INDICATED THAT LARGE
SCALE LIFT WAS OCCURRING WEST OF THIS LINE...SO A FEW
THUNDERSTORMS CANNOT BE RULED OUT BEFORE SUNSET. IF NOTHING
MATERIALIZES BY SUNSET...THUNDERSTORM CHANCES SHOULD DIMINISH WITH
THE LOSS OF HEATING THROUGH THE OVERNIGHT HOURS.

SATURDAY...THE WEST COAST UPPER TROUGH IS EXPECTED TO START MOVING
EAST...AND ALL MODEL GUIDANCE SHOWS THAT THIS IS SUFFICIENT TO
MOVE THE PERSISTENT WEST TEXAS UPPER LOW EAST...OUT OF THE
REGION. THE UPPER LOW IS EXPECTED TO REMAIN JUST SOUTH OF THE CWA
AS IT MOVES EAST TOMORROW...HOWEVER MODELS SHOW THAT THE SOUTHERN
THIRD OF THE CWA WILL BENEFIT FROM LARGE SCALE FORCING FOR ASCENT
ASSOCIATED WITH THIS LOW FOR MUCH OF THE DAY. WENT AHEAD AND KEPT
THE 20 POPS IN PLACE FOR LOCATIONS GENERALLY ALONG AND SOUTH OF A
LINE FROM COMANCHE TO PALESTINE SATURDAY AFTERNOON AS A RESULT OF
THIS FORECAST LIFT. EXTENDED THE POPS TO INCLUDE SATURDAY MORNING
AS MODELS START TO RAMP UP MID LEVEL ISENTROPIC LIFT (STRONGEST AT
THE 310K LEVEL) BY 15Z/10AM TOMORROW MORNING. WITH THE BEST
MOISTURE AND LIFT HOLDING SOUTH OF THE CWA...DO NOT EXPECT MUCH
MORE THAN ISOLATED COVERAGE OF SHOWERS OR THUNDERSTORMS AT THIS
TIME.

ALL OPERATIONAL GUIDANCE SHOWS THAT THE WEST TEXAS UPPER
LOW...AND THE CYCLONIC SHEAR AXIS ALOFT THAT LOOSELY CONNECTS THAT
LOW TO THE NORTHERN MISSOURI UPPER LOW...WILL PUSH EAST OF THE
REGION BY SUNDAY MORNING. ASSUMING GUIDANCE IS CORRECT IN THAT
TIMING...THE ENTIRE AREA SHOULD BE DOMINATED BY LARGE SCALE
FORCING FOR SUBSIDENCE...FAVORING A DRY FORECAST BEGINNING SUNDAY
HEADED INTO THE WORK WEEK. SUBSIDENCE SHOULD ALSO SUPPORT LESS
CLOUD COVER...AND TEMPERATURES WILL LIKELY CREEP UP INTO THE LOW
90S AS A RESULT OF THE ADDITIONAL SUNSHINE. ALTHOUGH THIS PATTERN
BEGINS ON SUNDAY...IT LOOKS TO HOLD OVER THE CWA THROUGH MID-
WEEK...SO EXPECT SOME WARMER THAN NORMAL CONDITIONS UNDER MOSTLY
SUNNY SKIES TO START NEXT WEEK.

BY WEDNESDAY A STRONG UPPER LOW...CURRENTLY LOCATED OVER/NEAR THE
ALEUTIAN ISLANDS OF ALASKA...IS EXPECTED TO MOVE SOUTHEAST OVER
THE NORTHWEST CONUS. THIS SYSTEM IS EXPECTED TO CONTINUE SOUTHEAST
OVER THE NEXT 24 HOURS...SENDING A RELATIVELY STRONG COLD FRONT
SOUTH ACROSS THE CWA ON THURSDAY. SEEING AS THIS SYSTEM IS
THOUSANDS OF MILES AWAY AND SEVERAL DAYS OUT...THERE IS SOME
INHERENTLY LOW CONFIDENCE IN THE DETAILS OF THE EVOLUTION OF THIS
SYSTEM. HOWEVER...ALL MODELS AT LEAST AGREE ON THE LARGE SCALE
EVOLUTION AND BRING A WELL DEFINED COLD FRONT ACROSS THE AREA.
MODELS DISAGREE ON THE TIMING OF THIS FRONT...AND THE PASSAGE OF
THE UPPER LOW...BUT THAT IS FAIRLY COMMON THIS FAR OUT.

MODELS BRING THE FRONT INTO NORTH TEXAS ANYTIME FROM LATE THURSDAY
MORNING THROUGH LATE THURSDAY NIGHT A THIS TIME. THEREFORE...
CONFIDENCE IN A CHANGE FROM ABOVE NORMAL TEMPERATURES TO NEAR OR
SLIGHTLY BELOW NORMAL TEMPERATURES BY FRIDAY IS FAIRLY HIGH. DUE
TO UNCERTAINTIES REGARDING HOW FAR SOUTH THIS ALEUTIAN ISLAND
UPPER LOW WILL PUSH OVER THE CONUS BEFORE KICKING EAST OVER THE
PLAINS...CONFIDENCE IN THE COVERAGE OR AMOUNT OF RAINFALL
ASSOCIATED WITH THIS SYSTEM IS CURRENTLY LOW.

MOST 12Z MODEL GUIDANCE INDICATED THAT THE BULK OF THE DYNAMIC
LIFT ASSOCIATED WITH THIS UPPER LOW WILL REMAIN NORTH OF TEXAS. IF
THAT IS THE CASE...WE WILL STILL SEE SOME RAIN SHOWERS AND
THUNDERSTORMS ALONG THE FRONT...BUT THE COVERAGE AND INTENSITY OF
THE PRECIPITATION WILL LIKELY BE LIMITED. IF THE UPPER LOW AND ITS
ASSOCIATED DYNAMICS SINK SOUTH...PRECIPITATION AMOUNTS AND
COVERAGE WOULD INCREASE QUITE A BIT. THIS IS SOMETHING WE WILL
CONTINUE TO WATCH CLOSELY AS THIS SYSTEM APPROACHES THE CONUS. FOR
THIS FORECAST...JUST MAINTAINED BROAD-BRUSHED 20 TO 30 POPS ON
THURSDAY WHEN MOST GUIDANCE AGREES THE COLD FRONT WILL PUSH ACROSS
THE CWA.

CAVANAUGH


&&



.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  68  89  68  90  68 /   5  10   0   0   0
WACO, TX              64  89  64  90  64 /  10  20   5   5   5
PARIS, TX             65  84  64  84  64 /   5   5   0   5   0
DENTON, TX            63  87  61  88  62 /   5   5   0   0   0
MCKINNEY, TX          62  88  62  89  61 /   5   5   0   0   0
DALLAS, TX            69  89  69  90  69 /   5  10   0   0   0
TERRELL, TX           66  90  66  91  66 /   5  10   0   5   0
CORSICANA, TX         66  89  65  89  66 /  10  10   5   5   0
TEMPLE, TX            65  88  65  90  64 /  10  20   5   5   5
MINERAL WELLS, TX     63  87  63  88  63 /  10  10   0   0   0

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

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