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

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000
FXUS64 KFWD 290917
AFDFWD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
417 AM CDT TUE JUL 29 2014

.DISCUSSION...

08Z SURFACE OBSERVATIONS SHOWED A STALLED OUT FRONTAL BOUNDARY
ALONG A LINE EXTENDING FROM COLLEGE STATION TO AUSTIN...ARCING
BACK TO THE WEST-NORTHWEST TOWARDS MIDLAND. AREA RADAR VAD WIND
PROFILES SHOWED THAT THE 850 MB REFLECTION OF THIS FRONT WAS
LOCATED SOMEWHERE BETWEEN KFWS AND KDYX...EXTENDING SOUTH NEAR
KGRK RADAR. UNFORTUNATELY THE RESOLUTION OF RADAR PLACEMENT IS
SUCH THAT A MORE REFINED POSITION IS NOT POSSIBLE. REGIONAL RADARS
SHOWED LITTLE ACTIVITY EARLY THIS MORNING...BUT THERE WERE SOME
SCATTERED SHOWERS ALONG THE TEXAS PANHANDLE/OKLAHOMA BORDER. THIS
MAY BE CLOSE TO THE 850 MB FRONT...BUT IT IS DIFFICULT TO SAY FOR
SURE. WATER VAPOR SATELLITE IMAGERY CONTINUED TO SHOW ANTICYCLONIC
FLOW ALOFT OVER MUCH OF TEXAS...HOWEVER THE CENTER OF THIS UPPER
RIDGE APPEARED TO BE LOCATED NEAR THE BIG BEND AREA...MOVING
SLOWLY TO THE WEST. NORTHWEST FLOW WAS OBSERVED FROM THE TEXAS
PANHANDLE OVER NORTH TEXAS.

TODAY...THUNDERSTORM CHANCES REMAIN IN THE FORECAST TODAY...MAINLY
FOR LOCATIONS ALONG AND WEST OF THE INTERSTATE 35/35W CORRIDOR.
THE EFFECTS OF DRY AIR ADVECTION WERE EVIDENT OVER THE DFW
METROPLEX AND POINTS NORTHEAST. DEW POINTS WERE IN THE UPPER 50S
TO LOWER 60S IN THESE LOCATIONS EARLY THIS MORNING. EAST TO
NORTHEASTERLY WINDS THROUGHOUT THE DAY TODAY SHOULD KEEP THESE
LOCATIONS DRY OVER THE NEXT 12-18 HRS AS A RESULT OF THIS DRY AIR
ALREADY IN PLACE.

HIGH RESOLUTION MODEL GUIDANCE CONTINUES TO ADVERTISE THE 850 MB
FRONT AS A FOCUS FOR THUNDERSTORM INITIATION AROUND SUNRISE THIS
MORNING. THESE MODELS SHOW 850 MB FLOW OVER WEST CENTRAL TEXAS
VEERING AROUND TO THE SOUTHWEST...PROVIDING SOME GOOD LOW-LEVEL
CONVERGENCE ALONG THIS FRONT EARLY THIS MORNING. LEFT 30 POPS IN
THE FORECAST ALONG AND WEST OF A JACKSBORO TO TEMPLE LINE THIS
MORNING IN CASE THIS PANS OUT. MOST MODEL GUIDANCE SHOWS 850 MB
WINDS COMING BACK AROUND TO THE SOUTH AFTER SUNRISE IN RESPONSE TO
BETTER LOW-LEVEL MIXING DUE TO HEATING...AND LEE SIDE CYCLOGENESIS
RAMPING UP LATER IN THE DAY DUE TO A SHORTWAVE TROUGH ROUNDING THE
BROAD RIDGE AXIS OVER THE CONUS ROCKIES. THIS SHOULD BRING THE 850
MB FRONT AND THETA-E RIDGE WEST A BIT...AND REORIENT IT NORTH TO
SOUTH OVER THE WESTERN CWA TODAY.

AFTERNOON SHOWERS AND THUNDERSTORMS ARE POSSIBLE ALONG AND WEST
OF THIS BOUNDARY...WITH THE BEST CHANCES REMAINING WEST OF A LINE
FROM GRAHAM TO GATESVILLE THIS AFTERNOON. WENT AHEAD AND LEFT SOME
20-30 POPS IN PLACE FROM WACO TO PALESTINE AND LOCATIONS SOUTH
BECAUSE LOW-LEVEL DRY AIR ADVECTION NEVER REALLY MADE IT THAT FAR
SOUTH...AND DEW POINTS REMAIN IN THE LOWER 70S EARLY THIS MORNING.
DRY AIR ADVECTION WILL BE SHUT OFF FOR CENTRAL TEXAS ONCE THE 850
MB FRONT BECOMES REORIENTED TODAY...SO STORMS MAY BE POSSIBLE ONCE
AGAIN DURING THE PEAK HEATING HOURS OF THE DAY WITHIN THIS LOW-
LEVEL MOISTURE RESERVOIR. AS MENTIONED ABOVE...FROM THE DFW AREA
NORTHEAST...DRY AIR IN PLACE WILL NOT BE HELPED BY ANY SIGNIFICANT
POSITIVE MOISTURE ADVECTION TODAY...SO THESE LOCATIONS SHOULD
REMAIN DRY.

THE SHORTWAVE TROUGH THAT IS RIDING ALONG THE CONUS ROCKIES UPPER
RIDGE IS EXPECTED TO MOVE OUT FROM OVER THE ROCKIES AND OVER THE
SOUTHERN HIGH PLAINS BY SUNRISE WEDNESDAY MORNING. THE NAM SEEMS
TO HAVE A VERY GOOD HANDLE ON THIS SHORTWAVE TROUGH...WHICH WAS
FAIRLY WELL DEFINED OVER NORTHERN ARIZONA ON 08Z WATER VAPOR
SATELLITE IMAGERY...MOVING NORTH TOWARDS UTAH. IN RESPONSE TO THIS
TROUGH...LEE SIDE CYCLOGENESIS IS EXPECTED TO MOVE FROM
SOUTHEASTERN COLORADO OUT OVER THE TX PANHANDLE THROUGH WEDNESDAY
MORNING. THE 850 MB FRONT WILL MOVE EAST WHILE BECOMING
REORIENTED FROM WEST TO EAST OVER OKLAHOMA WEDNESDAY AFTERNOON.

FOR NORTH TEXAS...MOST MODEL GUIDANCE INDICATES THAT THIS
BOUNDARY WILL MOVE FROM WEST TO EAST OVER THE CWA FROM LATE
TONIGHT THROUGH WEDNESDAY MORNING. PRECIPITATION CHANCES ALONG
THIS RETREATING FRONT ARE NOT THAT GREAT BECAUSE THE LOW-LEVEL
ATMOSPHERE IS REALLY JUST REORGANIZING FOR THE NORTHERN ARIZONA
SHORTWAVE TROUGH AND ASSOCIATED SURFACE LOW PRESSURE SYSTEM
DEVELOPING OVER THE HIGH PLAINS. EVEN THOUGH THE FRONT IS
MOVING OVER THE CWA...THE LOW-LEVEL FLOW REGIME FAVORS
FRONTOLYSIS...SO THERE IS REALLY NO SIGNIFICANT FORCING FOR ASCENT
ASSOCIATED WITH THIS BOUNDARY. THE CHANGE IN LOW-LEVEL WIND
DIRECTION WILL RESULT IN SOME FAIRLY SUBSTANTIAL POSITIVE MOISTURE
ADVECTION...BUT THIS BY ITSELF DOES NOT GUARANTEE ANY
PRECIPITATION WILL DEVELOP OVER THE CWA. AT ANY RATE...LEFT SOME
SMALL PRECIPITATION CHANCES IN THE FORECAST ALONG THE AXIS OF BEST
POSITIVE MOISTURE RETURN...AS MOISTURE CONVERGENCE MAY OFFER JUST
ENOUGH LIFT TO RESULT IN SOME ISOLATED TO SCATTERED RAIN SHOWERS
AND THUNDERSTORMS ALONG AND NORTH OF THE INTERSTATE 20 CORRIDOR
FROM TONIGHT THROUGH WEDNESDAY MORNING.

THE PRIMARY FOCUS FOR PRECIPITATION OVER THE NEXT 24 TO 36 HOURS
WILL BE OVER THE HIGH PLAINS OF EASTERN NEW MEXICO AND COLORADO AS
POSITIVE MOISTURE ADVECTION INTERACTS WITH OROGRAPHIC LIFT. BY
WEDNESDAY MORNING...THE RETREATING FRONT WILL LIKELY BE WELL
DEFINED FROM THE HIGH PLAINS EXTENDING EAST-SOUTHEAST OVER
OKLAHOMA AND SHOULD BE A SECONDARY FOCUS FOR VERY GOOD RAINFALL
CHANCES AND HEAVY RAINFALL. THE PRIMARY FORECAST CHALLENGE AFTER
WEDNESDAY AFTERNOON WILL BE THE EVOLUTION OF THE LOW PRESSURE
SYSTEM AS THE NORTHERN ARIZONA SHORTWAVE MOVES EAST-SOUTHEAST FROM
COLORADO OUT OVER THE HIGH PLAINS THROUGH WEDNESDAY EVENING.

MOST GUIDANCE SHOWS THAT AS THE SHORTWAVE TROUGH MOVES OFF THE
HIGH PLAINS IT WILL MOVE EAST-SOUTHEAST...FROM THE TEXAS PANHANDLE
AND THEN OVER SOUTHERN OKLAHOMA WEDNESDAY EVENING. MODELS SHOW A
CONCENTRATION OF HIGH QPF OVER THE INTERSECTION OF THE PATH OF
THIS UPPER TROUGH...AND THE 850 MB FRONTAL BOUNDARY ON WEDNESDAY.
THIS MAKES SENSE AS THIS IS WHERE LOW AND UPPER LEVEL FORCING FOR
ASCENT OVERLAP WITH VERY DEEP MOISTURE. HOWEVER THE CONSENSUS OF
MODEL GUIDANCE ALSO SHOWS THE SURFACE LOW MOVING EAST-SOUTHEAST
DRAGGING THE FRONT SOUTH TOWARDS THE RED-RIVER WEDNESDAY NIGHT.

MODELS KEEP A SIGNIFICANT AMOUNT OF QPF WEDNESDAY NIGHT ALONG AND
NORTH OF THE FRONT...WHICH APPEARS TO BE LARGELY DOMINATED BY
NEUTRAL TO NEGATIVE THETA-E ADVECTION...AND RESIDES IN WHAT SHOULD
BE SUBSIDENCE NORTHWEST OF THE UPPER TROUGH. THE MODELS FAIRLY
CONSISTENTLY HAVE THE 850 MB THETA-E RIDGE OVER THE NORTHEASTERN
PORTIONS OF THE CWA EXTENDING INTO NORTHEAST TEXAS. MODELS ALSO
ADVERTISE THIS AREA...NORTHEAST OF THE DFW METROPLEX...TO HAVE
PWATS IN EXCESS OF 2 INCHES WITH GOOD LOW-LEVEL CONVERGENCE. IF
THE MODEL MASS FIELDS ARE CORRECT...IT WOULD SEEM LIKE THAT THE
WEDNESDAY NIGHT HEAVY RAINFALL AXIS SHOULD SLIDE SOUTH OF WHERE
RAW MODEL OUTPUT IS SHOWING ITS BULLS-EYE OF QPF. AS A
RESULT...WENT AHEAD AND BUMPED POPS UP TO 80 PERCENT NORTHEAST OF
THE METROPLEX WEDNESDAY NIGHT AND MENTIONED HEAVY RAINFALL IN THE
WORDED FORECAST AS MODEL QPF SEEMS MISPLACED...AT LEAST IN THE 12
HOUR WINDOW FROM WEDNESDAY NIGHT TO THURSDAY MORNING.

THERE ARE THINGS THE MODEL MAY BE RESOLVING THAT ARE NOT EVIDENT
IN THE MASS FIELDS AT THIS POINT. CONVECTIVE FEEDBACK IN MODEL
OUTPUT IS GENERALLY REGARDED AS BAD...HOWEVER LONG-LIVED LATENT
HEAT RELEASE CAN RESULT IN THE DIABATIC CREATION OF A MID-LEVEL
LOW PRESSURE SYSTEM THAT CAN DISPLACE MOISTURE AND CONVERGENCE
FIELDS. THIS DOES NOT APPEAR TO BE THE CASE...BUT IT IS SOMETHING
THAT HAPPENS DURING LONG-LIVED PRECIPITATION EVENTS...AND IT IS
VERY LIKELY TO RAIN HEAVILY FOR MANY HOURS ALONG THE 850 MB FRONT
ACROSS OKLAHOMA DURING THE DAY ON WEDNESDAY. UNFORTUNATELY WE WILL
NOT KNOW IF A STRONG MID-LEVEL LOW PRESSURE SYSTEM DEVELOPS FROM
THIS PRECIPITATION UNTIL WEDNESDAY AFTERNOON...SO AT THIS TIME
JUST SIDED WITH THE MODEL MASS FIELDS WHICH INDICATE A HEAVY
RAINFALL EVENT IS POSSIBLE FOR THE NORTHEASTERN CWA WEDNESDAY
NIGHT. IF MODELS TREND IN THE DIRECTION OF HEAVY RAIN SHIFTING
SOUTH WEDNESDAY NIGHT...A FLASH FLOOD WATCH MAY BE NECESSARY
NORTHEAST OF THE DFW AREA IN LATER FORECASTS.

BEHIND THE UPPER TROUGH...THE SURFACE LOW IS EXPECTED TO MOVE
EAST-SOUTHEAST OVER LOUISIANA BY THURSDAY AFTERNOON...DRAGGING THE
NOW COLD FRONT SOUTH ACROSS THE ENTIRE CWA DURING THE DAY ON
THURSDAY. WHILE THIS WOULD NORMALLY SEEM LIKE A GOOD SCENARIO FOR
A WIDESPREAD RAINFALL EVENT FOR NORTH TEXAS...MODEL GUIDANCE
STRONGLY SUGGESTS THAT IT IS NOT. UNFORTUNATELY AS THE SURFACE LOW
PULLS AWAY TO THE EAST-SOUTHEAST...MODELS ARE IN STRONG AGREEMENT
THAT STRONG 700 MB SUBSIDENCE PUSHES OVER THE CWA FROM NORTHWEST
TO SOUTHEAST ON THURSDAY. THIS SHOULD RESULT IN AN ABRUPT END TO
PRECIPITATION FROM NORTHWEST TO SOUTHEAST ALONG THE COLD FRONT ON
THURSDAY.

UNFORTUNATELY IF THIS PANS OUT...MUCH OF THE DFW AREA MAY MISS
OUT ON ANY HEAVY RAINFALL ASSOCIATED WITH THIS STORM SYSTEM
BECAUSE THE MID-LEVEL SUBSIDENCE BUILDS IN QUICKLY STARTING LATE
THURSDAY MORNING. ON THURSDAY...THE BEST CHANCES FOR THUNDERSTORMS
ALONG THE COLD FRONT LIKELY RESIDE OVER THE FAR SOUTHEASTERN
CWA...OR THOSE LOCATIONS FARTHEST REMOVED FROM THE MID-LEVEL
SUBSIDENCE. FOR THOSE FOLLOWING ALONG LOOKING AT MODEL DATA...JUST
LOOK AT 700 MB RELATIVE HUMIDITY PROGS TO TRACK THIS MID-LEVEL
SUBSIDENCE...IT WAS VERY EASY TO SEE ON 29/00Z MODEL GUIDANCE. THE
BEST CHANCE FOR THE DFW AREA TO RECEIVE HEAVY RAINFALL IS IF THE
SURFACE LOW AND 850 MB FRONT SINK MUCH FARTHER SOUTH THAN
CURRENTLY EXPECTED. IF THIS OCCURS...THE DFW AREA COULD GET INTO
SOME OF THE HEAVIER PRECIPITATION AMOUNTS WEDNESDAY NIGHT. THIS
DOES NOT LOOK LIKELY RIGHT NOW...BUT WEDNESDAYS PROLONGED RAINFALL
EVENT OVER OKLAHOMA MAY CHANGE THE STRENGTH OF THE COLD AIR BEHIND
THE FRONT...PUSHING IT FARTHER SOUTH THAN EXPECTED FOR WEDNESDAY
NIGHT.

FRIDAY THROUGH EARLY NEXT WEEK...ASSUMING THE STRONG MID-LEVEL
SUBSIDENCE IS CORRECT IN THE MODELS...THE REMAINDER OF THE
FORECAST SHOULD BE DRY. TEMPERATURES WILL REMAIN BELOW NORMAL
BEHIND THURSDAYS FRONT...BUT WILL MODERATE BACK UP TO NORMAL
LEVELS BY EARLY NEXT WEEK DUE TO PERSISTENT SUNSHINE THROUGH THE
WEEKEND.

CAVANAUGH


&&

.AVIATION...
/ISSUED 1152 PM CDT MON JUL 28 2014/

A COLD FRONT CURRENTLY SOUTH OF THE KACT REGION WILL REMAIN NEARLY
STATIONARY OVERNIGHT...BUT THE WESTERN END SHOULD BEGIN TO LIFT
NORTHWARD ON TUESDAY. THIS WILL RESULT IN LIGHT NORTHERLY WINDS
OVERNIGHT AND TUESDAY MORNING THEN WINDS WILL GO EASTERLY 10 KNOTS
OR LESS AROUND MIDDAY AND THEN SOUTHEASTERLY IN THE LATE AFTERNOON.

OTHERWISE...THE TERMINALS WILL REMAIN VFR THROUGH THEM FORECAST
WITH SCATTERED CIGS AROUND 12 KFT POSSIBLE ACROSS THE METROPLEX AT
TIMES TONIGHT. AS FOR CONVECTION...IT SHOULD REMAIN WEST OF THE
TERMINALS TONIGHT. HOWEVER...WITH THE COLD FRONT SO CLOSE TO
KACT...THERE COULD BE SOME ISOLATED TO WIDELY SCATTERED ACTIVITY
LATE TONIGHT (08-12Z) AND ON TUESDAY. LOW CONFIDENCE IN THIS
OCCURRENCE PRECLUDES US FROM ADDING IT TO THE TAF. 75


&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  93  75  90  73  81 /  10  20  20  40  30
WACO, TX              93  73  97  75  89 /  20  10  10  10  30
PARIS, TX             90  70  80  67  76 /  10  30  40  80  50
DENTON, TX            90  72  87  71  81 /  10  30  20  50  40
MCKINNEY, TX          91  72  84  70  80 /  10  30  30  60  50
DALLAS, TX            93  75  90  73  81 /  10  20  20  40  30
TERRELL, TX           94  73  87  72  79 /  10  20  20  50  40
CORSICANA, TX         91  73  93  74  84 /  10  10  20  20  40
TEMPLE, TX            93  71  97  74  90 /  30  20  10  10  40
MINERAL WELLS, TX     92  72  96  71  83 /  40  20  20  20  20

&&

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

&&

$$

 /




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