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

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000
FXUS64 KFWD 261740 AAB
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
1240 PM CDT SAT JUL 26 2014

.AVIATION...
/18Z TAFS/

CONCERNS...NONE.

VFR CONDITIONS WILL PREVAIL THROUGH SUNDAY. A FEW AFTERNOON CU
WILL DOT THE TOP OF THE BOUNDARY LAYER 6-7KFT AGL. OTHERWISE...
SKIES WILL BE CLEAR. STEADY SOUTH WINDS WILL CONTINUE.

A COLD FRONT IS STILL ON TRACK TO ARRIVE IN THE METROPLEX MONDAY
MORNING...SHIFTING TRAFFIC TO NORTH FLOW. ACCOMPANYING
THUNDERSTORMS MAY RESULT IN SOME BRIEF DISRUPTIONS TO OPERATIONS.
HOWEVER...THE CONVECTIVE ACTIVITY IS NOT EXPECTED TO BE WIDESPREAD
OR PROLONGED.

25

&&

.UPDATE...
TEMPERATURES ARE WARMING STEADILY ACROSS NORTH TEXAS THIS MORNING
UNDER FULL JULY SUN. AFTERNOON HIGHS SHOULD HAVE NO PROBLEM
REACHING THE UPPER 90S TO AROUND 103. A SOUTHERLY BREEZE SHOULD
OFFSET THE HIGH HUMIDITY A BIT AND PROVIDE AT LEAST SOME RELIEF
FROM THE HEAT.

THE CURRENT FORECAST IS IN GOOD SHAPE SO NO CHANGES ARE NECESSARY
AT THIS TIME.

79

&&

.PREV DISCUSSION... /ISSUED 402 AM CDT SAT JUL 26 2014/

00Z RAOBS SHOWED AN UPPER LEVEL HIGH PRESSURE SYSTEM CENTERED
ROUGHLY OVER CHILDRESS TEXAS AT THE 500 MB LEVEL. EARLY MORNING
WATER VAPOR SATELLITE IMAGERY CONFIRMED THAT THIS FEATURE REMAINED
IN PLACE WITH DISTINCT ANTICYCLONIC FLOW OVER THE SOUTHERN PLAINS
AND THE SOUTHERN HIGH PLAINS. THE 00Z FWD RAOB OBSERVED A
PRECIPITABLE WATER (PWAT) OF 1.07...WHICH IS BELOW THE 25TH
PERCENTILE FOR THIS TIME OF YEAR ACCORDING TO THE BUNKERS PWAT
CLIMATOLOGY DATABASE.

FOR TODAY AND TOMORROW...WITH AN ABNORMALLY DRY AIR MASS IN PLACE
AND UPPER LEVEL HIGH PRESSURE DOMINATING OUR REGIONAL
WEATHER PATTERN...MAINTAINED A DRY AND HOT FORECAST THROUGH THIS
WEEKEND. CONFIDENCE IN A HOT AND DRY FORECAST IS FAIRLY HIGH AT
THIS TIME...BUT EVEN SO...THERE ARE A COUPLE OF AREAS TO WATCH FOR
SMALL THUNDERSTORM CHANCES OVER THE NEXT 36 TO 48 HOURS.

THE FIRST FEATURE TO KEEP AN EYE ON IS THE SEA-BREEZE BOUNDARY.
REGIONAL RADARS TRACKED THE SEA-BREEZE MOVING NORTH TOWARDS BELL
COUNTY RIGHT AROUND SUNSET YESTERDAY. THERE WERE NO THUNDERSTORMS
ALONG THIS BOUNDARY YESTERDAY LATE AFTERNOON/EVENING...BUT IT DID
MAKE IT TO THE CWA BORDER. WITH SOUTHERLY WINDS EXPECTED OVER THE
NEXT 48 HOURS...THERE WILL BE AT LEAST SOME SHALLOW MOISTURE
RETURN TO THE REGION THROUGH THE WEEKEND. WITH SOME DEEPER
MOISTURE TO WORK WITH...WILL HAVE TO WATCH THE SEA-BREEZE BOUNDARY
AS IT MOVES NORTHWEST THIS AFTERNOON AND SUNDAY AFTERNOON TO
MONITOR FOR ISOLATED THUNDERSTORM CHANCES ACROSS THE SOUTHERN CWA.
DID NOT INCLUDE THUNDERSTORMS IN THE FORECAST AT THIS TIME AS THE
UPPER LEVEL RIDGE WILL STILL BE IN PLACE...AND IT IS UNKNOWN
WHETHER THE SEA-BREEZE WILL BE ABLE TO MAKE IT FAR ENOUGH NORTH TO
RESULT IN LATE AFTERNOON THUNDERSTORM CHANCES BEFORE SUNSET. HIGH
CONFIDENCE IN THE RIDGE AND ITS ASSOCIATED FORCING FOR SUBSIDENCE
SUPPORTS A DRY FORECAST A THIS TIME.

THE SECOND FEATURE TO WATCH IS THE SPEED OF A COLD FRONT MOVING
SOUTH FROM THE CENTRAL PLAINS TOWARDS THE RED RIVER SUNDAY
AFTERNOON. CONFIDENCE IN THIS FRONT PUSHING SOUTH ACROSS THE
PLAINS THIS WEEKEND IS VERY HIGH BECAUSE THE UPPER LOW THAT WILL
SEND THE FRONT TO THE SOUTH IS PROMINENT AND VERY STRONG LOOKING
ON WATER VAPOR SATELLITE IMAGERY EARLY THIS MORNING. THIS STRONG
UPPER LOW WAS IN PLACE OVER SOUTHERN SASKATCHEWAN AS OF 08Z/3AM.
NEARLY ALL GUIDANCE SHOWS THIS UPPER LOW MOVING SOUTHEAST OVER THE
GREAT LAKES REGION THIS WEEKEND...WHICH IS A BIG PART OF THE
REASON WHY THERE ARE CONSECUTIVE DAYS OF SPC MODERATE RISK
OUTLOOK AREAS ACROSS THE UPPER MID-WEST TO THE MID-ATLANTIC
STATES.

THE PRIMARY CONCERN FOR NORTH TEXAS IS WHETHER THE FRONT WILL
REMAIN NORTH OF THE RED RIVER LATE SUNDAY AFTERNOON OR NOT. THE
CONSENSUS OF GUIDANCE DOES SLOW THE FRONT DOWN QUITE A BIT ON
SUNDAY...SO LEFT THE NORTHERN CWA DRY FOR NOW SUNDAY AFTERNOON.
HOWEVER IT IS A BIT CONCERNING THAT NON-CONVECTION ALLOWING MODELS
ARE SHOWING SIGNS OF SHALLOW CONVECTION BEING TRIGGERED IN THEIR
VARIOUS CONVECTION PARAMETERIZATION SCHEMES OVER THE NORTHWESTERN
CWA SUNDAY AFTERNOON. (THAT IS...THERE`S NO MODEL QPF...BUT THERE
IS COOLING AND SATURATION IN THE MID-LEVELS THAT SHOWS UP FOR NO
PARTICULAR REASON.) AT ANY RATE...WILL NOT BE TOO CONCERNED ABOUT
THUNDERSTORM CHANCES UNLESS THE FRONT DOES NOT SLOW DOWN SUNDAY
AFTERNOON. IF THE FRONT CROSSES THE RED RIVER...WE WILL NEED TO
PLACE THUNDERSTORMS IN THE FORECAST.

SUNDAY NIGHT AND MONDAY...MOST MODELS SHOW THE COLD FRONT PUSHING
SOUTH OF THE RED RIVER AFTER MIDNIGHT SUNDAY NIGHT. WENT AHEAD
WITH SOME 20 POPS OVER THE NORTHERN CWA AS A RESULT. FORECAST
SOUNDINGS SHOW THAT SURFACE BASED STORMS ARE VERY UNLIKELY DUE TO
THE NOCTURNAL INVERSION...HOWEVER MID-LEVEL LAPSE RATES ARE STEEP
ENOUGH THAT WITH SOME MID-LEVEL MOISTURE...ELEVATED SHOWERS AND
THUNDERSTORMS LOOK LIKELY NEAR OR NORTH OF THE COLD FRONT AS IT
MOVES OVER THE CWA. EXTENDED 20 POPS TO THE SOUTH OF THE DFW AREA
MONDAY MORNING...AND THEN BUMPED UP POPS TO 30 PERCENT FROM THE
DFW AREA SOUTH ACROSS CENTRAL TEXAS FOR MONDAY AFTERNOON.

STORMS MONDAY AFTERNOON SHOULD TRANSITION FROM ELEVATED TO
SURFACE BASED WITH SUFFICIENT HEATING SOUTH OF THE FRONT. FORECAST
SOUNDINGS SHOW A THERMODYNAMIC ENVIRONMENT THAT LOOKS VERY
SUPPORTIVE OF THUNDERSTORMS PRODUCING STRONG MICROBURSTS.
KINEMATIC FIELDS ARE WEAK AND NOT SUPPORTIVE OF ORGANIZED
THUNDERSTORMS...SO PRIMARILY SINGLE CELL STORMS WITH A MICROBURST
THREAT ARE EXPECTED NEAR AND SOUTH OF THE FRONT MONDAY AFTERNOON.
STORMS WILL LIKELY STILL OCCUR NORTH OF THE FRONT MONDAY
AFTERNOON...BUT STRONG MICROBURSTS ARE NOT AS LIKELY AS CLOUD
COVER WILL REDUCE LOW-LEVEL LAPSE RATES THEREBY LIMITING THE
INTENSITY OF DOWNDRAFTS. THE FRONT IS EXPECTED TO CONTINUE SLOWLY
TO THE SOUTH/SOUTHWEST MONDAY NIGHT...AND MAINTAINED 20 TO 30 POPS
BASED ON ITS CONSENSUS LOCATION THROUGH TUESDAY MORNING.

TUESDAY THROUGH WEDNESDAY...BEHIND THE FRONT THE CONSENSUS OF
GUIDANCE SHOWS FAIRLY DEEP LOW-LEVEL NORTHEASTERLY FLOW INTO NORTH
AND CENTRAL TEXAS THROUGH TUESDAY EVENING. THIS NORTHEASTERLY FLOW
REPRESENTS FAIRLY STOUT DRY AND COOL AIR ADVECTION...WHICH SHOULD
EFFECTIVELY DRY OUT THE LOWER TROPOSPHERE WHILE COOLING US OFF
SEVERAL DEGREES FOR TUESDAY AFTERNOON. OUR FLOW ALOFT IS EXPECTED
TO SHIFT FROM WEAK ANTI-CYCLONIC TO NORTHWEST BY TUESDAY
AFTERNOON...HOWEVER AT THIS TIME THERE ARE NO SHORTWAVE TROUGHS
EVIDENT THAT WILL SPREAD LIFT OVER THE CWA TUESDAY THROUGH
WEDNESDAY. WITHOUT ANY OBVIOUS LIFTING MECHANISM AND WITH MUCH
DRIER AIR IN PLACE...WENT AHEAD AND REMOVED THE BROAD BRUSHED 20
POPS THAT WERE IN THE FORECAST FROM TUESDAY THROUGH WEDNESDAY
AFTERNOON. DID LEAVE SOME SMALL CHANCE OF THUNDERSTORMS OVER THE
FAR NORTHWESTERN CWA FOR WEDNESDAY AFTERNOON AS MODELS ARE HINTING
AT SOME MOISTURE RETURN OVER THE HIGH PLAINS BY THIS TIME. THERE
IS A SMALL CHANCE THAT SOMETHING MIGHT DEVELOP JUST OFF TO OUR
NORTHWEST AND MOVE INTO THE CWA BEFORE SUNSET ON WEDNESDAY.

WEDNESDAY NIGHT AND THURSDAY...LOW-LEVEL FLOW IS EXPECTED TO VEER
FROM NORTHEASTERLY ON TUESDAY TO SOUTHEASTERLY BY THURSDAY
MORNING. THIS VEERING OF THE LOW-LEVEL FLOW WILL RESULT IN LOW-
LEVEL MOISTURE RETURNING TO THE SOUTHERN HIGH PLAINS FIRST ON
WEDNESDAY...AND THEN BUILDING BACK TO THE EAST ACROSS NORTH AND
CENTRAL TEXAS ON THURSDAY. MODELS ARE SHOWING A FAIRLY CONSISTENT
SIGNAL THAT AN MCS WILL ORGANIZE OVER THE HIGH PLAINS WEDNESDAY
NIGHT AND MOVE SOUTHEAST TOWARDS THE RED RIVER EARLY THURSDAY
MORNING. WENT AHEAD AND KEPT 30 POPS OVER THE NORTHWEST CWA...AND
EXPANDED 20 POPS EASTWARD ACROSS THE ENTIRE AREA THROUGH THURSDAY
MORNING DUE TO UNCERTAINTIES WITH REGARDS TO TIMING AND STRENGTH
OF THIS MCS. THIS MCS IS EXPECTED TO OCCUR OUT AHEAD OF A
SHORTWAVE TROUGH EMBEDDED IN THE NORTHWEST FLOW ALOFT...SO
CONFIDENCE IN THE MCS IS HIGH...IT`S JUST NOT CLEAR WHETHER IT
WILL HOLD TOGETHER AS IT MOVES TOWARDS NORTH TEXAS THURSDAY
MORNING.

OUR BEST CHANCE OF RAIN/STORMS LOOKS TO OCCUR ON THURSDAY AS THE
SHORTWAVE TROUGH MOVES SOUTHEAST AND SPREADS SOME FORCING FOR
ASCENT OVER THE CWA. THE BULK OF THE ENERGY ALOFT LOOKS TO REMAIN
NORTH OF THE CWA...SO HELD HIGHER POPS OVER THE NORTHERN COUNTIES
VERSUS CENTRAL TEXAS. SOME MODELS HAVE A WEAK FRONT MOVING SOUTH
ACROSS THE CWA WITH THE SHORTWAVE TROUGH...AND IF THIS IS THE CASE
POPS WILL NEED TO BE INCREASED IN LATER FORECASTS. ASIDE FROM
PRECIPITATION CHANCES...THURSDAY SHOULD BE OUR COOLEST DAY OF THE
WEEK AS MOSTLY CLOUDY SKIES SHOULD KEEP TEMPERATURES IN THE MID TO
UPPER 80S FOR MOST LOCATIONS. IF WIDESPREAD RAIN PANS OUT...HIGHS
WILL BE EVEN LOWER ACROSS THE AREA.

FRIDAY INTO NEXT WEEKEND...WITH THE POSSIBILITY OF A STALLED
FRONTAL BOUNDARY ACROSS THE CWA ON FRIDAY...MAINTAINED BROAD
BRUSHED 20 POPS IN THE FORECAST FOR FRIDAY. WENT AHEAD WITH A DRY
FORECAST FOR NEXT WEEKEND FOR NOW AS DRY EASTERLY FLOW ONCE AGAIN
IS EXPECTED TO ADVECT COOL DRY AIR INTO THE AREA. UPPER LEVEL
TROUGHING OVER THE EASTERN CONUS ACTUALLY BUILDS WEST NEXT
WEEKEND...WHICH SHOULD HELP KEEP TEMPERATURES ABNORMALLY COOL FOR
THIS TIME OF YEAR. IF THIS FORECAST HOLDS...NEXT WEEKEND LOOKS DRY
AND RELATIVELY COOL...WHICH SHOULD ALLOW FOR A VERY PLEASANT
WEEKEND TO HEAD OUTDOORS.

CAVANAUGH



&&


.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 100  79  99  78  94 /   0   0   0  10  30
WACO, TX              99  75  98  75  98 /   0   0   0   5  30
PARIS, TX             97  75  97  74  90 /   0   0   0  20  30
DENTON, TX           100  76  99  76  91 /   0   0   0  20  30
MCKINNEY, TX          99  75  99  75  91 /   0   0   0  20  30
DALLAS, TX           100  80  99  79  95 /   0   0   0  10  30
TERRELL, TX           98  77  99  75  96 /   0   0   0  10  30
CORSICANA, TX         98  76  97  75  96 /   0   0   0   5  30
TEMPLE, TX            99  73  97  73  97 /   0   0   0   5  30
MINERAL WELLS, TX    101  74  99  74  94 /   0   0   0  10  30

&&

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

&&

$$

25/79





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