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

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FXUS64 KFWD 290501 AAC
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
1201 AM CDT MON SEP 29 2014

.AVIATION...
THE WINDS THAT SHIFTED TO THE NORTHEAST BEHIND A BOUNDARY THAT MOVED
THROUGH LATE SUNDAY AFTERNOON VEERED BACK TO THE EAST BY LATE EVENING.
EXPECT WINDS TO BACK AROUND TO THE NORTHEAST AGAIN TOWARD DAYBREAK
/12Z/. WINDS SPEEDS WILL REAMIN LIGHT AT LESS THAN 10 KNOTS.

FOR THE WACO TAFS...LIGHT NORTHEAST WINDS WILL PREVAIL THROUGH THE
FORECAST PERIOD.


58

&&

.UPDATE...
THICK HIGH-BASED CUMULUS FROM EARLIER THIS EVENING HAVE ALL BUT
DISAPPEARED ACROSS NORTH TEXAS...GIVING WAY TO MOSTLY CLEAR
SKIES. RADIATIONAL COOLING SHOULD ALLOW TEMPERATURES TO STEADILY
DROP OVERNIGHT...LEADING TO LOWS IN THE 60S AREA-WIDE MONDAY
MORNING. THE DRY WEATHER PATTERN CONTINUES EARLY THIS WORK WEEK
WITH RAIN CHANCES RETURNING LATE WEDNESDAY AND THURSDAY.

30

&&

.PREV DISCUSSION... /ISSUED 350 PM CDT SUN SEP 28 2014/

12Z UPPER AIR ANALYSIS SHOWED UPPER LEVEL LOW PRESSURE SYSTEMS
OVER THE SOUTHWEST CONUS...OVER SOUTH CENTRAL CANADA...AND OVER
IOWA AND MISSOURI. THE IOWA/MISSOURI UPPER LOW WAS EASILY
DISCERNABLE ON WATER VAPOR SATELLITE IMAGERY...BUT APPEARED TO BE
VERY WEAK AND NOT ASSOCIATED WITH ANY SIGNIFICANT LIFT BASED ON
12Z UPPER AIR OBSERVATIONS. THE SOUTHWEST CONUS AND SOUTH CENTRAL
CANADIAN UPPER LOWS APPEARED TO BE THE STRONGEST LOW PRESSURE
SYSTEMS NEAR THE CONUS. SHORTWAVE RIDGING WAS EVIDENT OVER THE
SOUTHERN HIGH PLAINS PER EARLY AFTERNOON WATER VAPOR SATELLITE
IMAGERY...AND A WEAK UPPER LEVEL DISTURBANCE WAS EVIDENT OVER FAR
EAST TEXAS...ALTHOUGH THERE WAS NOT MUCH INDICATION OF THIS
FEATURE IN THE MORNING RAOB ANALYSIS.

THIS EVENING THROUGH TUESDAY...THE SOUTHWEST CONUS AND SOUTH
CENTRAL CANADIAN UPPER LOWS ARE EXPECTED TO WORK TOGETHER TO HELP
BREAK DOWN A LARGE SCALE UPPER LEVEL RIDGE IN PLACE OVER THE
EASTERN TWO THIRDS OF THE CONUS. CLOSER TO HOME HERE IN NORTH
TEXAS...RIDGING WILL ACTUALLY INCREASE IN MAGNITUDE THROUGH
TUESDAY AS THE SHORTWAVE RIDGE OVER THE SOUTHERN HIGH PLAINS
BUILDS EAST OVER THE NEXT 48-60 HRS. WITH SHORTWAVE RIDGING IN
PLACE...EXPECT TEMPERATURES TO CLIMB 5-10 DEGREES ABOVE NORMAL
UNDER MOSTLY CLEAR SKIES.

DURING THE DAY ON TUESDAY...AN UPPER LEVEL LOW PRESSURE SYSTEM
THAT CURRENTLY EXTENDS FROM THE BAY OF ALASKA TO THE SOUTH OVER
THE OPEN WATERS OF THE PACIFIC IS EXPECTED TO MOVE SOUTHEAST OVER
THE NORTHWESTERN CONUS COAST. THIS UPPER LEVEL LOW PRESSURE SYSTEM
IS FAIRLY LARGE AND CONTAINS WHAT MODELS INDICATE ARE THREE STRONG
SHORTWAVE TROUGHS. THE FIRST ONE IS EXPECTED TO SWING OUT OVER THE
CENTRAL PLAINS BY TUESDAY NIGHT...KICKING THE SOUTHWEST CONUS
UPPER LOW WELL OFF TO THE NORTH OVER SOUTH CENTRAL CANADA. WHILE
THIS WILL NOT HAVE MUCH OF A DIRECT IMPACT ON WEATHER ACROSS NORTH
TEXAS...IT WILL EFFECTIVELY BREAK DOWN THE UPPER RIDGE OVER THE
PLAINS...ALLOWING THE JET STREAM TO DIP SOUTH OVER THE CENTRAL
PLAINS BY MID-WEEK.

THE NEXT PIECE OF ENERGY/SHORTWAVE TROUGH IS EXPECTED TO DIG
SOUTHEAST TOWARDS THE SOUTH PLAINS WEDNESDAY NIGHT INTO THURSDAY
MORNING. AS THIS NEXT UPPER TROUGH APPROACHES...THE PLACEMENT OF
THE JET STREAM SOUTH OVER THE SOUTHERN CONUS ROCKIES COMBINED WITH
THE FORCING FOR ASCENT ASSOCIATED WITH THE APPROACHING UPPER
TROUGH WILL RESULT IN STRONG LEE SIDE CYCLOGENESIS NEAR THE TX/OK
PANHANDLES WEDNESDAY AFTERNOON. THIS WILL RESULT IN SOME STRONGER
MOISTURE ADVECTION FROM THE GULF...THE ADVECTION OF AN ELEVATED
MIXED LAYER FROM THE HIGH TERRAIN OF NORTHERN MEXICO...AND A
EASTERLY PUSH OF THE DRYLINE TOWARDS THE WESTERN CWA WEDNESDAY
AFTERNOON.

ALL OF THESE FACTORS COMBINED WILL RESULT IN PARAMETERS THAT
APPEAR TO BE SUPPORTIVE OF ORGANIZED THUNDERSTORMS ALONG THE
DRYLINE WEDNESDAY AFTERNOON/EVENING. THE PRIMARY LIMITING FACTORS
WITH REGARDS TO THUNDERSTORM CHANCES APPEAR TO BE THE LACK OF
LARGE SCALE LIFT...AND THE PRESENCE OF THE ELEVATED MIXED LAYER
(EML) OVER THE REGION. THUNDERSTORM CHANCES WILL BE DEPENDENT UPON
SUFFICIENT LIFT ALONG THE DRYLINE OVERCOMING THE EML CAP. THE
DRYLINE ITSELF IS EXPECTED TO BE LOCATED NEAR A WICHITA FALLS TO
ABILENE LINE...OR JUST WEST OF THE CWA.

AT THIS TIME...WITH THE SHORTWAVE TROUGH EXPECTED TO BE WELL OFF
TO THE NORTHWEST OF THE DRYLINE DURING THE PEAK HEATING HOURS OF
THE DAY WEDNESDAY...THE MOST LIKELY SCENARIO IS FOR THE CAP TO
HOLD RESULTING IN NO STORMS WEDNESDAY AFTERNOON...OR FOR THE
DRYLINE TO SET UP FARTHER WEST THAN MODELS CURRENTLY
INDICATE...KEEPING ISOLATED STORMS WEST OF THE CWA. WENT AHEAD AND
BACKED OFF ON POPS A BIT FROM 20 PERCENT TO 10 PERCENT TO ACCOUNT
FOR THIS DROP IN CONFIDENCE IN THUNDERSTORMS IMPACTING THE CWA ON
WEDNESDAY. PARAMETERS CONTINUE TO SUPPORT A SUPERCELL STORM MODE
IF ANYTHING CAN GET GOING. IF THE SHORTWAVE TROUGH IS
CLOSER/FASTER ON WEDNESDAY...THUNDERSTORM CHANCES WILL INCREASE
AND PUSH EAST BACK TOWARDS GRAHAM AND BRECKENRIDGE/OUR WESTERN
CWA.

THE SECOND SHORTWAVE TROUGH IS EXPECTED TO CONTINUE EAST ACROSS
THE CENTRAL PLAINS DURING THE DAY ON THURSDAY...SENDING A COLD
FRONT SOUTH ACROSS THE REGION IN ITS WAKE. OUR BEST PRECIPITATION
CHANCES FOR NORTH AND CENTRAL TEXAS SHOULD REMAIN FAIRLY CLOSE TO
THE FRONT...UNLESS THE SHORTWAVE TROUGH CAN DIG FARTHER SOUTH THAN
CURRENTLY EXPECTED. FORCING FOR ASCENT ALONG THE FRONT WILL STILL
HAVE TO CONTEND WITH THE EML CAP...HOWEVER LIFT ALONG THE FRONT IS
EXPECTED TO BE STRONGER THAN LIFT NEAR THE DRYLINE ON
WEDNESDAY...SO AT LEAST SOME ISOLATED TO SCATTERED STORMS ARE
EXPECTED ALONG THE FRONT ON THURSDAY.

UNFORTUNATELY THE COVERAGE OF STORMS/RAIN ARE EXPECTED TO BE
LIMITED TO ABOUT 30 PERCENT...SO DID NOT MAKE ANY SIGNIFICANT
ADJUSTMENTS TO POPS AT THIS TIME. THE CANADIAN SOLUTION IS THE
ONLY ONE THAT CONTINUES TO ADVERTISE A MORE SOUTHERLY PUSH TO THE
UPPER LEVEL DYNAMICS. IF THIS MODEL VERIFIES...POPS WILL HAVE TO
BE INCREASED QUITE A BIT...AS WELL AS RAINFALL AMOUNTS. THE
CANADIAN SIMPLY APPEARS TO REPRESENT THE LEAST LIKELY SOLUTION AT
THIS TIME...AND SO WAS LARGELY IGNORED IN THIS FORECAST.

BEHIND THE FRONT...A VERY DRY AIR MASS IS EXPECTED TO BUILD OVER
THE REGION. WHILE TEMPERATURES BEHIND THE FRONT ARE NOT REALLY
SIGNIFICANTLY COOLER...THE CHANGE OVER TO A VERY DRY AIR MASS WILL
RESULT IN SOME OVERNIGHT LOWS IN THE MID 50S THIS WEEKEND...WHICH
WILL HELP KEEP DAYTIME HIGHS AT LEAST 10 DEGREES COOLER THAN WHAT
WILL BE IN PLACE TO START THE WEEK. TEMPERATURES FROM FRIDAY
THROUGH SUNDAY SHOULD TOP OUT IN THE LOW 80S AND SKIES ARE
EXPECTED TO REMAIN MOSTLY CLEAR WITH DRY AIR IN PLACE.

CAVANAUGH



&&


.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  68  89  69  91  71 /   5   0   0   0   5
WACO, TX              64  89  65  93  71 /   0   0   0   0   5
PARIS, TX             64  85  64  89  67 /   5   0   0   0   5
DENTON, TX            63  88  64  91  68 /   0   0   0   0   5
MCKINNEY, TX          63  89  64  90  69 /   5   0   0   0   5
DALLAS, TX            69  90  70  91  73 /   5   0   0   0   5
TERRELL, TX           66  91  68  91  70 /   5   0   0   0   5
CORSICANA, TX         65  90  68  91  70 /   0   0   0   0   5
TEMPLE, TX            65  90  67  92  69 /   0   0   0   0   5
MINERAL WELLS, TX     63  88  64  90  69 /   0   0   0   0   5

&&

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

&&

$$

58/30




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