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

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FXUS64 KFWD 222027
AFDFWD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
327 PM CDT FRI MAY 22 2015

.DISCUSSION...
A WARM FRONT IS MOVING THROUGH NORTH TEXAS AT THIS TIME WITH
TEMPERATURES AND DEWPOINTS STEADILY CLIMBING AS THE SURFACE WINDS
ATTAIN A SOUTHERLY COMPONENT. WEAK ISENTROPIC LIFT AND WARM
ADVECTION ABOVE THE SURFACE WILL CONTINUE THROUGH THE OVERNIGHT
HOURS...WHICH WILL ENSURE LOW CLOUD COVER AND A FEW SHOWERS OR
STORMS. THIS ACTIVITY SHOULD GENERALLY BE WEAK WITH NO RISK FOR
SEVERE WEATHER AND LIMITED RAINFALL. TEMPERATURES TONIGHT WILL
STAY MILD AND HUMID WITH LOWS ONLY IN THE 60S.

AN UPPER LEVEL LOW CURRENTLY NEAR LAS VEGAS WILL LUMBER EASTWARD
DURING THE NEXT COUPLE OF DAYS AND SET THE STAGE FOR A ROUND OF
HEAVY RAINFALL AND SOME SEVERE STORMS OVER THE REGION SATURDAY
AFTERNOON THROUGH SUNDAY AFTERNOON. PRECIPITABLE WATER WILL
APPROACH 2 INCHES WHICH WOULD BE UNUSUALLY HIGH FOR MAY. PERHAPS
MORE IMPORTANTLY THE UNIDIRECTIONAL SOUTHERLY WIND PROFILE IS ONE
THAT PORTENDS HEAVY RAINFALL EVENTS...BECAUSE IT FOSTERS CELL
TRAINING OR SLOW MOVING LINES OF STORMS. ALSO OF NOTE OUR LOW
LEVEL WINDS INCREASE TO NEAR 40KT WHICH WOULD QUICKLY REPLENISH
THE ATMOSPHERIC MOISTURE THAT IS PRECIPITATED OUT. UNLIKE OUR
PREVIOUS STORM EVENTS DURING THE LAST 3 WEEKS...DIRECTIONAL WIND
SHEAR AND INSTABILITY WILL BE MUCH LOWER WHICH WILL TEND TO
MITIGATE THE SEVERE WEATHER THREAT. HOWEVER THE LOWER INSTABILITY
AND UNIDIRECTIONAL SHEAR WOULD INCREASE CELL PRECIPITATION
EFFICIENCY. ALTHOUGH...AS WE SAW...THOSE SLOW MOVING SUPERCELLS
HAD THE ABILITY TO DUMP EXTREME AMOUNTS OF RAIN...THE HIGHEST
AMOUNTS WERE FAIRLY LOCALIZED. IN THIS UPCOMING SITUATION...THERE
IS A GREATER POTENTIAL FOR EXTREME RAIN AMOUNTS OVER A LARGER
AREA. THUS IN ADDITION TO FLASH FLOODING...RIVER FLOODING IS
LIKELY TO BECOME A SIGNIFICANT IMPACT...ALSO EXACERBATED BY THE
FACT THAT THERE IS LITTLE ROOM FOR WATER IN AREA LAKES.

AS FOR THE SPECIFICS...SCATTERED TO NUMEROUS THUNDERSTORMS WILL
DEVELOP TO OUR WEST AND HEAD NORTHEAST INTO THE WESTERN PORTIONS
OF THE CWA DURING THE AFTERNOON HOURS. THE SEVERE WEATHER THREAT
WILL BE GREATEST FROM MID AFTERNOON TO MID EVENING...WHEN
CONVECTION IS MORE CELLULAR AND THERE IS A LITTLE MORE
INSTABILITY AVAILABLE. GENERALLY EXPECT STRONG WINDS AND HAIL TO
BE THE MAIN SEVERE WEATHER THREAT...BUT THERE REMAINS A LOW
TORNADO POTENTIAL. OTHERWISE CONVECTION SHOULD START TO
CONSOLIDATE INTO A LINE OR BAND THAT TRAINS AND DUMPS AN AVERAGE
OF 2-4 INCHES OF RAIN ACROSS THE NORTHWESTERN CWA SATURDAY
EVENING. AS TIME WEARS ON A COLD POOL WILL DEVELOP SATURDAY
EVENING...WHICH WILL HELP PUSH THE LINE SLOWLY SOUTHEAST TOWARD
THE I-35 CORRIDOR DURING THE OVERNIGHT HOURS AND INTO SUNDAY
MORNING. RAINFALL ACROSS THE CENTRAL ZONES AND SOUTHERN ZONES WILL
AVERAGE 1 TO 3 INCHES. SEVERE WEATHER THREAT OVERNIGHT FOR THE
I-35 CORRIDOR WOULD MAINLY BE STRONG WINDS AND PERHAPS A BRIEF
WEAK TORNADO...BUT THE OVERALL LIMITED INSTABILITY WILL LESSEN
SEVERE POTENTIAL. THE BAND OF RAIN SHOULD CONTINUE TO HEAD
EASTWARD THROUGH THE MORNING HOURS SUNDAY...LIKELY CLEARING THE
CWA BY LATE AFTERNOON. AN AVERAGE OF 1-2 INCHES IS EXPECTED OVER
THE EASTERN ZONES. SOME MODEL GUIDANCE SUGGESTS MORE CONVECTION
WILL FIRE OVER THE WESTERN ZONES IN THE AFTERNOON...BUT THE
AIRMASS MAY BE TOO WORKED OVER FOR ANOTHER ROUND SO WILL KEEP
SUNDAY AFTERNOON/EVENING POPS LOW.

A FLASH FLOOD WATCH IS IN EFFECT FOR THE ENTIRE AREA GIVEN THE
POTENTIAL FOR HEAVY RAINFALL AND FLOODING...BUT AGAIN WE ARE MOST
CONCERNED ABOUT THE REGION JUST NORTH AND WEST OF THE DFW
METROPLEX FOR SIGNIFICANT FLOODING SATURDAY NIGHT. THERE STILL IS
SOME UNCERTAINTY...AND IT IS POSSIBLE THE TRAINING BANDS OF
CONVECTION WILL SET UP IN A DIFFERENT LOCATION...OR MOVE MORE
SLOWLY SUNDAY MORNING ACROSS THE CENTRAL AND EASTERN ZONES...SO
THE FLASH FLOOD WATCH IS NEEDED EVEN THOUGH OUR DETERMINISTIC QPF
FORECAST HAS LOWER AMOUNTS IN THE EAST.

OTHERWISE...THE PRIMARY CHANGE IN THE FORECAST CONCERNS MONDAY
AFTERNOON AND MONDAY NIGHT WHEN ANOTHER SHORTWAVE TROUGH WILL MOVE
THROUGH THE STATE. PREVIOUSLY MODEL GUIDANCE HAD FOCUSED CONVECTION
ALONG THE TEXAS COASTLINE WHICH PROTECTED US FROM ROBUST
CONVECTION THIS FAR NORTH. CONVECTION ALONG THE GULF COAST WOULD
HAVE INTERCEPTED OR PREVENTED GULF MOISTURE RETURN...AND WOULD
HAVE PLACED OUR REGION IN A ZONE OF SUBSIDENCE. MODEL GUIDANCE
DURING THE LAST DAY HAS WEAKENED THE GULF COAST CONVECTION MONDAY
MORNING...AND THEREFORE BRINGS THE HIGH MOISTURE BACK INTO THE
REGION MONDAY AFTERNOON. IF THE 70 DEWPOINTS DO ARRIVE BACK INTO
THE AREA...IT WOULD CREATE AN EXTREMELY UNSTABLE ATMOSPHERE OVER
THE REGION. BOTH THE NAM/GFS INDICATE WIDESPREAD SURFACE BASED
CAPE IN EXCESS OF 5000 J/KG. THIS AMOUNT MAY BE OVERDONE...BUT
NONETHELESS THERE IS A SIGNAL THAT HIGH INSTABILITY WILL BE
AVAILABLE MONDAY AFTERNOON AS FORCING FROM THE SHORTWAVE ARRIVES
LATE IN THE DAY. THUS HAVE INCREASED POPS TO 60 PERCENT...AND WE
ARE FORECASTING THE POTENTIAL FOR ANOTHER ROUND OF HEAVY RAINFALL
AND SEVERE WEATHER MONDAY EVENING AND NIGHT. THE HIGH INSTABILITY
WOULD LIKELY MEAN A MCS OR SQUALL LINE WOULD FORM...WHICH WOULD
MOVE FAIRLY QUICKLY OVER THE REGION AND HOPEFULLY HELP LIMIT
RAINFALL AMOUNTS TO 1 TO 2 INCHES. WE WILL GET MORE INTO THE
SPECIFICS REGARDING THIS EVENT DURING THE NEXT COUPLE OF DAYS.

THE REGION WILL REMAIN IN A WEAK FLOW REGIME WITH BROAD TROUGHING
TUESDAY INTO THURSDAY. WILL CONTINUE TO CARRY JUST A GENERIC LOW
CHANCE OF CONVECTION...WHICH WILL BE DIURNALLY DRIVEN. LOW SHEAR
WILL LIMIT ORGANIZATION...BUT ENOUGH INSTABILITY WILL BE AVAILABLE
FOR PULSE SEVERE OR LOCALLY HEAVY DOWNPOURS WHERE THESE STORMS DO
POP UP. TEMPERATURES WILL CONTINUE TO MODERATE DURING THE WEEK
WITH HIGHS BENEFITING FROM MORE SUNSHINE AND REACHING THE MID 80S
BY WEDNESDAY AND THURSDAY. THE NEXT SYSTEM IS SLATED FOR FRIDAY
WHEN THE REGION WILL LIKELY SEE ANOTHER ROUND OF WIDESPREAD RAIN.

TR.92

&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  65  79  67  75  69 /  20  50  80  90  30
WACO, TX              69  81  68  75  69 /  20  50  70  80  30
PARIS, TX             60  80  69  74  67 /  20  40  80  90  60
DENTON, TX            65  78  66  75  66 /  20  60  90  90  20
MCKINNEY, TX          64  80  69  74  66 /  20  50  80  90  30
DALLAS, TX            67  80  67  75  69 /  20  50  80  90  30
TERRELL, TX           68  81  70  74  68 /  20  40  70  90  50
CORSICANA, TX         69  81  70  75  69 /  20  40  50  90  50
TEMPLE, TX            69  81  69  76  69 /  20  40  70  80  30
MINERAL WELLS, TX     66  77  66  77  65 /  20  60 100  70  20

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY EVENING
FOR TXZ091>095-100>107-115>123-129>135-141>148-156>162-174-175.


&&

$$


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