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

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FXUS64 KFWD 211744 AAC
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
1144 AM CST FRI NOV 21 2014

.AVIATION...
/18Z TAFS/

CONCERNS...CONTINUING LIFR-LOW END MVFR CONDITIONS THROUGH THE
PERIOD. INCREASING RAIN/STORM CHANCES SATURDAY.

SIGNIFICANT IMPACTS TO AVIATION OPERATIONS ARE EXPECTED OVER THE
NEXT 24-30 HOURS BUT CONFIDENCE IS UNFORTUNATELY LOW IN THE TIMING
AND SOME OF THE TRENDS MAKING THIS A DIFFICULT TAF FORECAST
PERIOD.

CIGS AND VSBY CONTINUE TO SLOWLY IMPROVE LATE THIS MORNING AND
EXPECT HIGH-END IFR/LOW-END MVFR CIGS TO PREVAIL THROUGH THE
AFTERNOON PERIOD. SOME BRIEF LIGHT RAIN IS POSSIBLE AT ANY OF THE
AIRPORTS THROUGH THE AFTERNOON BUT THE CHANCES ARE TOO LOW TO
MENTION IN THE TAF. AFTER SUNSET...EXPECT CONDITIONS TO
DETERIORATE BACK INTO LIFR CATEGORY. SOME SHOWERS ARE POSSIBLE
ACROSS THE REGION THIS EVENING AND OVERNIGHT BUT THE EVOLUTION AND
COVERAGE OF THE SHOWERS IS DIFFICULT TO FORECAST AT THIS TIME.
THINK KACT HAS A BETTER CHANCE OF EXPERIENCING SHOWERS AS THE
HIGHEST MOISTURE SHIFTS FROM SOUTHEAST TO NORTHWEST TONIGHT IN
ADVANCE OF AN APPROACHING SHORTWAVE. WILL MENTION VCSH FROM
22/03-22/10Z AT KACT BUT THE WINDOW FOR SHOWER ACTIVITY WILL
LIKELY BE SMALLER.

AS THE SHORTWAVE CONTINUES TO APPROACH THE REGION
OVERNIGHT...ANTICIPATE MOST OF THE RAIN AND STORM ACTIVITY WILL
REMAIN WEST OF THE AIRPORTS UNTIL LATE SATURDAY MORNING. SOME
SHOWERS OR POSSIBLY ISOLATED THUNDERSTORMS MAY OCCUR CLOSE TO THE
DFW TAF SITES OVERNIGHT AND WILL KEEP A VCSH MENTION AFTER 10Z
AT THE METROPLEX TAF SITES...BUT THINK THE METROPLEX AIRPORTS WILL
REMAIN MOSTLY DRY OVERNIGHT. THUNDERSTORMS WILL BECOME MORE
NUMEROUS AND CONTINUOUS AT THE DFW AIRPORTS BY MIDDAY WITH THE
HIGHEST RAIN CHANCES IN THE AFTERNOON HOURS. KACT`S BEST RAIN
CHANCES WILL BE IN THE AFTERNOON HOURS...JUST BEYOND THE VALID TAF
PERIOD. THE RAIN WILL END FROM WEST TO EAST SATURDAY EVENING/NIGHT
AND CONDITIONS WILL QUICKLY IMPROVE. HEAVY RAINFALL IS POSSIBLE
WITH THESE STORMS AND SOME OF THE STORMS NEAR KACT COULD REACH
SEVERE LIMITS DURING THE DAY ON SATURDAY.

82/JLD

&&

.UPDATE...
NORTH AND CENTRAL TEXAS CONTINUE TO EXPERIENCE LOW LEVEL WARM
ADVECTION THIS MORNING WITH STRONGER ISENTROPIC ASCENT OCCURRING
ACROSS FAR EAST AND SOUTHEAST TEXAS LATE THIS MORNING. ANY PATCHY
EARLY MORNING DENSE FOG HAS MOSTLY LIFTED OUTSIDE OF A FEW
ISOLATED LOCATIONS...WITH THOSE AREAS EXPECTED TO SHOW A GRADUAL
IMPROVEMENT INTO EARLY AFTERNOON.

A SHORTWAVE DISTURBANCE MOVING EAST ACROSS NEBRASKA IS EXPECTED
TO MOVE READILY INTO THE UPPER MIDWEST...WHILE THE STRONGER
SHORTWAVE OVER AZ/CA MOVES SOUTHEAST OVER NORTHERN MEXICO.
INCREASING SHORTWAVE RIDGING WILL DEVELOP IN BETWEEN THESE TWO
UPPER FEATURES ACROSS OUR FAR WESTERN COUNTIES THIS AFTERNOON AND
IS ALREADY NOTED BY SOME DISSIPATION OF MORNING CLOUD COVER.
NEVERTHELESS...LATEST UPPER AIR ANALYSIS INDICATES LITTLE SUBSIDENCE
WITH THIS FEATURE. APPROACHING HEIGHT FALLS LATE IN THE DAY WILL
LIKELY PULL THE CURRENT BATCH OF SHOWERS AND ISOLATED THUNDERSTORMS
OVER SOUTHEAST TEXAS BACK TO THE NORTHWEST WITH THE BEST CHANCES
BEING ACROSS THE SOUTHEAST HALF OF THE CWA. SOME BREAKS OF THE
CLOUD COVER OUT WEST WILL HELP TEMPERATURES WARM INTO THE LOWER
AND MID 70S AND CANNOT RULE OUT ISOLATED...STRONG TO SEVERE STORMS
THIS AFTERNOON ACROSS THESE AREAS DUE TO A INCREASINGLY UNSTABLE
THERMODYNAMIC ENVIRONMENT.

A MARGINAL RISK FOR SEVERE STORMS IS IN PLACE NORTHWEST OF A
COMANCHE...FORT WORTH... GAINESVILLE LINE. OUTSIDE OF THE ISOLATED
THREAT FOR STORMS THIS AFTERNOON...WE EXPECT THE MAIN TIME FRAME OF
STORMS ACROSS THE RISK AREA TO BE DURING THE OVERNIGHT HOURS...WHEN
THE LEADING EDGE OF STRONGER LARGE-SCALE ASCENT CORRELATES WITH THE
WESTERN EDGE OF INCREASING WARM ADVECTION IN THE 925MB-850MB LAYER
FOR AN INCREASING HAIL THREAT.

05/

&&

.PREV DISCUSSION... /ISSUED 359 AM CST FRI NOV 21 2014/
MORNING SATELLITE IMAGERY SHOWS EXTENSIVE LOW CLOUD COVER HAS NOW
SPREAD ACROSS ALL OF NORTH TEXAS WELL IN ADVANCE OF A VIGOROUS
SHORTWAVE TROUGH THAT WILL BRING RAIN AND THUNDERSTORMS TO THE
REGION THROUGH SATURDAY. 9Z SURFACE ANALYSIS INDICATES A WEAK
SURFACE LOW PRESSURE CENTER SOUTHWEST OF WICHITA FALLS WITH A
STATIONARY FRONTAL BOUNDARY EXTENDING NORTHEAST ACROSS SOUTH
CENTRAL OKLAHOMA. MID 50S DEWPOINTS HAVE SPREAD AS FAR NORTH AS
THE RED RIVER THIS MORNING. A SECONDARY BOUNDARY OF HIGHER
MOISTURE EXISTS ACROSS SOUTH CENTRAL TEXAS WHERE DEWPOINTS HAVE
RISEN INTO THE LOW AND MID 60S. WATER VAPOR IMAGERY SHOWS A LEAD
SHORTWAVE TROUGH NOW MOVING THROUGH THE TEXAS PANHANDLE. THIS
FEATURE WILL QUICKLY MOVE EAST OF THE REGION BY MIDDAY. THE SECOND
MORE POWERFUL SYSTEM IS CURRENTLY DIGGING INTO SOUTHERN CALIFORNIA
AND WILL ARRIVE IN TEXAS DURING THE DAY TOMORROW.

PERSISTENT LOW LEVEL WARM MOIST ADVECTION CONTINUES THIS MORNING
ACROSS MUCH OF TEXAS. THE AXIS OF STRONGEST LIFT IS EXPECTED TO BE
ACROSS THE SOUTHEAST PART OF THE CWA THROUGH MIDDAY. THIS LINES UP
WELL WITH ONGOING SHOWERS WHICH CURRENTLY EXTEND FROM NEAR
VICTORIA THROUGH BRYAN/COLLEGE STATION AND INTO THE PALESTINE
AREA. SCATTERED SHOWERS AND POSSIBLY SOME THUNDERSTORMS ARE
EXPECTED TO CONTINUE FOR THE NEXT SEVERAL HOURS ACROSS THESE
AREAS. LATER TODAY...LOW LEVEL WINDS WILL BEGIN TO BACK IN
RESPONSE TO THE STRONG UPSTREAM SHORTWAVE. THIS WILL ALLOW THE
WARM MOIST ADVECTION TO SHIFT WESTWARD THROUGH THIS AFTERNOON.
WHILE THIS WOULD TYPICALLY INDICATE A WESTWARD SHIFT IN ANY
ONGOING PRECIPITATION...THE DEPARTING LEAD SHORTWAVE CURRENTLY
OVER THE PANHANDLE WILL LEAVE WEAK SUBSIDENCE IN ITS WAKE. ALL OF
THE MODEL GUIDANCE INDICATES WEAK HEIGHT RISES CONTINUING INTO
THIS EVENING ACROSS MOST OF NORTH TEXAS. THIS SETS UP A BATTLE
BETWEEN THE WEAK SUBSIDENCE ALOFT AND LOW LEVEL FORCING FOR ASCENT
SPREADING WESTWARD THROUGH THIS EVENING. FORECAST SOUNDINGS
INDICATE MODERATE INSTABILITY DEVELOPING BY THIS AFTERNOON MAINLY
SOUTH OF I-20 AND WEST OF I-35 AS STEEPER LAPSE RATES FROM WEST
TEXAS ADVECT EASTWARD INTO THE AREA. WHILE THIS COULD POTENTIALLY
SUPPORT SOME STRONG TO SEVERE THUNDERSTORMS THIS AFTERNOON AND
EVENING...THE LACK OF SIGNIFICANT FORCING ALOFT APPEARS TO BE THE
MAIN INHIBITING FACTOR...ESPECIALLY SINCE SIGNIFICANT CLOUD COVER
IS EXPECTED TO LIMIT HEATING THROUGH THE AFTERNOON HOURS.

BY TONIGHT AS THE SHORTWAVE GETS CLOSER...SUBSTANTIAL HEIGHT
FALLS WILL BEGIN TO OVERSPREAD NORTH TEXAS. THERE SHOULD BE A
SHIFT WESTWARD IN PRECIPITATION ALONG A SURFACE TROUGH AXIS WHICH
WILL LIKELY BE ACROSS THE NORTHWEST COUNTIES. SHOWERS AND
THUNDERSTORMS WILL INCREASE IN COVERAGE THROUGH THE MORNING HOURS
SATURDAY AS A SURFACE LOW BECOMES ESTABLISHED AND STARTS TO MOVE
EAST AHEAD OF THE UPPER TROUGH. PRECIPITATION COVERAGE ACROSS
NORTH TEXAS WILL LIKELY BE 100 PERCENT DURING THE DAY SATURDAY AS
THE SURFACE LOW AND BEST FORCING FOR ASCENT TRACKS RIGHT ACROSS
THE REGION. GIVEN THE PROXIMITY TO THE UPPER LOW...WIND FIELDS
WILL BE RATHER STRONG WITH THIS SYSTEM...YIELDING MODERATE TO
STRONG DEEP LAYER SHEAR VALUES. THE MAIN CONCERN REGARDING SEVERE
WEATHER POTENTIAL REVOLVES AROUND THE AMOUNT OF INSTABILITY THAT
ACTUALLY DEVELOPS DURING THE DAY SATURDAY. MOST OF THE GUIDANCE
CONTINUES TO SUGGEST THAT THE BEST INSTABILITY WILL REMAIN ACROSS
CENTRAL AND SOUTH TEXAS DURING THE DAY...WITH OUR SOUTHERN
COUNTIES HAVING THE BEST CHANCE FOR SEVERE WEATHER. FORECAST
SOUNDINGS FOR SATURDAY AFTERNOON INDICATE NEARLY MOIST ADIABATIC
PROFILES WITH VERY LITTLE CAPE SUGGESTING A LOW THREAT FOR SEVERE
STORMS. WIDESPREAD CONVECTION ACROSS NORTH TEXAS WILL LIKELY BE
WELL AHEAD OF THE COLD TEMPERATURES ALOFT ASSOCIATED WITH UPPER
TROUGH. THE MAIN CONCERN WITH THIS IS THAT IT WOULD ONLY TAKE A
LITTLE BIT OF WARMING OR A LITTLE MORE MOISTURE THAN ADVERTISED BY
THE MODELS TO SUBSTANTIALLY INCREASE SURFACE INSTABILITY IN A
STRONGLY SHEARED ENVIRONMENT. SO...CONFIDENCE REMAINS LOW
CONCERNING THE SEVERE POTENTIAL ACROSS OUR CWA. THE HIGHEST THREAT
FOR SEVERE STORMS WILL BE SOUTH OF INTERSTATE 20 THROUGH SATURDAY
EVENING. IF MORE ROBUST INSTABILITY DOES DEVELOP SATURDAY
AFTERNOON...THERE WOULD BE A THREAT FOR PRIMARILY DAMAGING WINDS
AND EVEN TORNADOES GIVEN THE STRONG SHEAR.

CONCERNING HEAVY RAINFALL POTENTIAL...PRECIPITABLE WATER VALUES
CLIMB IN EXCESS OF 1.25 INCHES WITH THIS SYSTEM LATER TONIGHT AND
APPROACH 1.5 BY SATURDAY WHICH IS QUITE HIGH FOR THIS TIME OF
YEAR. WIDESPREAD RAINFALL AMOUNTS OF 1 TO 3 INCHES APPEARS LIKELY
ACROSS A GOOD PORTION OF NORTH TEXAS. THE SPEED AT WHICH THIS
SYSTEM MOVES THROUGH AND EXTENSIVE DROUGHT CONDITIONS ACROSS NORTH
TEXAS SUGGEST THAT WE WILL BE ABLE TO HANDLE THAT AMOUNT OF RAINFALL
WITHOUT ANY SIGNIFICANT FLOODING CONCERNS. URBAN FLASH FLOODING
WILL REMAIN A THREAT THROUGH SATURDAY.

ALL OF THIS ACTIVITY WILL MOVE EAST OF THE AREA LATE SATURDAY
NIGHT WITH DRIER AIR MOVING IN FROM THE WEST. SUNDAY WILL BE NICE
WITH TEMPERATURES WARMING INTO THE 70S WITH MAINLY WESTERLY FLOW
IN PLACE. THE COOLER AIR WILL ARRIVE ON MONDAY WITH TEMPERATURES
FALLING BACK TO UPPER 50S AND LOWER 60S. THE REMAINDER OF NEXT
WEEK SHOULD BE MOSTLY DRY AND SEASONAL.

DUNN



&&


.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  69  60  67  54  72 /  20  70 100  70   5
WACO, TX              71  61  69  52  74 /  40  60 100  60   0
PARIS, TX             64  54  65  55  69 /  40  70  90 100  10
DENTON, TX            69  59  66  51  70 /  20  80 100  70  10
MCKINNEY, TX          67  58  66  51  70 /  20  70 100  90  10
DALLAS, TX            69  59  67  56  72 /  20  70 100  70   5
TERRELL, TX           68  58  68  54  72 /  40  60 100  90  10
CORSICANA, TX         71  58  69  55  74 /  50  40 100  80   5
TEMPLE, TX            71  61  69  52  75 /  40  50 100  50   0
MINERAL WELLS, TX     71  59  67  49  71 /  20  80 100  30   5

&&

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

&&

$$

82/05





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