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

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000
FXUS64 KFWD 261739
AFDFWD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
1239 PM CDT SUN APR 26 2015

.UPDATE...

...MESOSCALE FORECAST UPDATE REGARDING THE FORECAST FOR SEVERE
STORMS ACROSS NORTH AND CENTRAL TEXAS TODAY...

12Z UPPER AIR ANALYSIS SHOWED AN INTENSE UPPER LEVEL TROUGH
LOCATED OVER THE SOUTHERN ARIZONA AND NEW MEXICO BORDER. 500 MB
HEIGHT FALLS OF 6 TO 12 DM WERE OBSERVED DOWNSTREAM OF THIS UPPER
TROUGH...AND THE MAGNITUDE OF THESE HEIGHT FALLS IS INDICATIVE OF
STRONG LARGE SCALE FORCING FOR ASCENT TO THE EAST. AT THE 700 MB
LEVEL...A PLUME OF STEEP MID-LEVEL LAPSE RATES WAS OBSERVED...WITH
A TEMPERATURE DIFFERENCE IN THE 700 TO 500 MB LAYER OF 22 DEG C
LOCATED SOUTHWEST OF NORTH AND CENTRAL TEXAS. TO THE SOUTHWEST OF
THIS PLUME OF ENHANCED LAPSE RATES...A 50 KT MID-LEVEL JET CORE
WAS OBSERVED OVER NORTHERN MEXICO. CLOSER TO THE SURFACE...AT THE
850 MB LEVEL...DEEP MOISTURE WAS ONLY OBSERVED OVER SOUTHWEST
TEXAS WITH A DRYLINE SUBJECTIVELY ANALYZED NEAR THE TX/OK
BORDER...EXTENDING SOUTHWEST OVER WEST CENTRAL TEXAS AND INTO
NORTHERN MEXICO ABOUT 60 MILES WEST OF DEL RIO. A 15Z SURFACE
ANALYSIS OBSERVED RICH MOISTURE IN PLACE ALONG THE TX GULF COAST
WITH MID 70S DEW POINTS OBSERVED WEST AND SOUTHWEST OF HOUSTON.

FOR TODAY...NEARLY ALL SHORT RANGE MODEL GUIDANCE INDICATES THAT A
SURFACE LOW PRESSURE SYSTEM WILL INTENSIFY RAPIDLY THIS AFTERNOON
OVER WEST CENTRAL TEXAS. MOST GUIDANCE SHOWS SURFACE PRESSURE
FALLING AT A RATE OF 2-3 MB PER HOUR LEADING UP TO 00Z. AT
15Z...THE LOWEST SURFACE PRESSURE OVER THE SOUTHERN HIGH PLAINS
WAS AROUND 1002 MB...MOST GUIDANCE INDICATES THE SURFACE LOW`S
PRESSURE WILL FALL TO 993 TO 995 MB BY 00Z. THAT MAGNITUDE OF
PRESSURE FALL ASSOCIATED WITH THE SURFACE LOW IS FAIRLY
INTENSE...AND SHOULD RESULT IN A CONVERGENCE OF PARAMETERS THAT
WILL SUPPORT A LOCALIZED SEVERE WEATHER OUTBREAK ACROSS THE
REGION THIS AFTERNOON AND EVENING. ONE OF THE KEY FORECAST
CHALLENGES TODAY WILL BE DETERMINING WHERE THE SURFACE LOW MOVES
AS THE RELATIVE THREATS FOR SUPERCELLS AND TORNADOES WILL VARY
DEPENDING ON THE EXACT POSITION OF THIS LOW LATER THIS AFTERNOON.

THE 12Z NAM AND 16Z HRRR INDICATE THE SURFACE LOW WILL BE LOCATED
JUST SOUTH OF INTERSTATE 20 AND JUST NORTH OF SAN ANGELO. IF THIS
POSITION FOR THE SURFACE LOW IS CORRECT...THE THREAT FOR DISCRETE
SUPERCELLS WOULD BE MAXIMIZED TO THE EAST OF THE SURFACE
LOW...WHERE A TRIPLE POINT WOULD LIKELY SET UP. SUPERCELLS WOULD
BE MOST LIKELY TO DEVELOP NEAR THIS TRIPLE POINT...AND THEN MOVE
EAST IN THE RELATIVELY STRONG SOUTHWESTERLY FLOW ALOFT. STORMS
APPEAR TO BE VERY LIKELY IN A SUPERCELL STORM MODE IF THEY DEVELOP
IN THIS TRIPLE POINT BY 00Z AS CAPE IS FORECAST TO BE ON THE ORDER
OF 3000 J/KG WITH DEEP LAYER SHEAR OF 50 KTS IN THE 0-6 KM AGL
LAYER. THE SHAPE OF THE 0-3 KM HODOGRAPH IS EXPECTED TO BE
CLOCKWISE LOOPING...AND DYNAMICALLY MORE FAVORABLE FOR RIGHT
MOVING SUPERCELLS. AS A RESULT...EXPECT SUPERCELL STORM MOTION TO
BE ALMOST DUE EAST LATE THIS AFTERNOON AND EARLY THIS EVENING.

RIGHT MOVING SUPERCELLS LOOK MOST LIKELY SOUTH OF INTERSTATE 20
BASED ON THE FORECAST POSITION OF THE SURFACE LOW. THIS PLACES
MUCH OF CENTRAL TEXAS IN THE PRIMARY THREAT CORRIDOR FOR DISCRETE
SUPERCELLS. THE ENVIRONMENT IS SUPPORTIVE OF WELL-ORGANIZED
SUPERCELLS CAPABLE OF PRODUCING VERY LARGE HAIL...DAMAGING WIND
GUSTS AND TORNADOES. THE RESIDENTS OF CENTRAL TEXAS ARE ENCOURAGED
TO PAY VERY CLOSE ATTENTION TO THE WEATHER THIS AFTERNOON AND
EVENING AS A RESULT. OF COURSE IF THE SURFACE LOW IS FARTHER NORTH
...THE PRIMARY THREAT CORRIDOR FOR DISCRETE SUPERCELLS WILL MOVE
NORTH WITH IT. AWAY FROM THIS PRIMARY THREAT CORRIDOR...IT IS
CERTAINLY POSSIBLE FOR SUPERCELLS TO DEVELOP JUST ABOUT ANYWHERE
IN THE WARM AIR ADVECTION REGIME INDICATED BY THE CLOCKWISE
LOOPING LOW-LEVEL HODOGRAPH. THIS LIFT/FORCING IS NOT AS STRONG
AND FOCUSED...SO IT IS SIMPLY MORE DIFFICULT TO KNOW IF...WHEN
AND WHERE A SUPERCELL MAY DEVELOP IN THIS WARM AIR ADVECTION
REGIME.

AFTER 00Z...THE VERY STRONG FORCING FOR ASCENT ASSOCIATED WITH THE
UPPER TROUGH OVER SOUTHERN ARIZONA AND NEW MEXICO IS EXPECTED TO
LIFT OUT OVER THE SOUTHERN PLAINS. THE LATEST MODEL GUIDANCE IS
CONVERGING ON A SOLUTION THAT SUGGESTS A VERY WELL ORGANIZED
SQUALL LINE WILL DEVELOP NEAR CHILDRESS...AND MOVE SOUTHEAST
TOWARDS NORTH TEXAS THIS EVENING. THERE ARE HINTS IN THE MODEL
MASS FIELDS THAT THIS SQUALL LINE COULD POTENTIALLY BE VERY WELL
ORGANIZED...AND MAY POSE A WIDESPREAD DAMAGING WIND THREAT AS IT
MOVES SOUTHEAST ACROSS NORTH TEXAS OVERNIGHT. IF THIS SQUALL LINE
DOES INDEED ORGANIZE...IT MAY PERSIST LONG ENOUGH AND PRODUCE
ENOUGH STRAIGHT LINE WIND DAMAGE TO QUALIFY AS A DERECHO BY THE
TIME IT EXITS THE CWA TO THE EAST WELL AFTER MIDNIGHT. THE PRIMARY
TIME THIS SQUALL LINE/BOW-ECHO IS EXPECTED TO MOVE OVER NORTH
TEXAS IS FROM 10 PM TO 3 AM. THE EXISTENCE OF THIS SQUALL LINE IS
FAR FROM 100 PERCENT CERTAIN...BUT IT WILL PROBABLY ORGANIZE BASED
ON THE CONSISTENT SIGNAL IN THIS MORNING`S HIGH RESOLUTION MODEL
GUIDANCE. THE PRIMARY THREATS WITHIN THIS SQUALL LINE WOULD BE
DAMAGING STRAIGHT LINE WINDS. ASSUMING THE SQUALL LINE MOVES
THROUGH THE AREA AFTER SUNSET AS CURRENTLY FORECAST...THIS MAY
REDUCE THE POTENTIAL FOR HIGH-END DAMAGING WINDS. REGARDLESS...
WIND DAMAGE WOULD STILL BE LIKELY AS THIS SQUALL LIKE WOULD
PROBABLY BE VERY WELL ORGANIZED. LARGE HAIL AND A BRIEF TORNADO
MAY ALSO OCCUR IN THIS LINE...ASSUMING IT DEVELOPS.

LAST BUT NOT LEAST...WE WILL ALSO BE MONITORING FOR HEAVY RAINFALL
AND FLASH FLOODING POTENTIAL THIS AFTERNOON AND EVENING. IF A WARM
FRONT SETS UP ALONG THE INTERSTATE 20 CORRIDOR...SCATTERED
THUNDERSTORMS COULD DEVELOP ALONG THIS BOUNDARY AND TRAIN OVER
AREAS TO THE NORTHEAST. THIS MAY EVOLVE INTO ANOTHER LOCALIZED
FLASH FLOODING EVENT NORTH OF INTERSTATE 20 AND GENERALLY EAST OF
INTERSTATE 35...VERY SIMILAR TO WHAT HAPPENED ON FRIDAY. WILL HOLD
OFF ON A FLASH FLOOD WATCH FOR NOW AS CONFIDENCE IN THIS TAKING
PLACE IS NOT HIGH AT THIS TIME. IF IT OCCURS...THESE LOCATIONS
HAVE ALREADY RECEIVED QUITE A BIT OF RAINFALL ON FRIDAY...SO
FLOODING WOULD TEND TO OCCUR QUICKLY IF STORMS BEGIN TO TRAIN OVER
THIS REGION THROUGH TONIGHT.

WILL CONTINUE TO MAKE SHORT TERM FORECAST UPDATES FOR CONVECTION
MODE THROUGH THIS EVENING. EXPECT STORMS WILL START DEVELOPING
NEAR THE SURFACE LOW AND EVOLVE INTO DISCRETE SUPERCELLS BY/AFTER
4 PM/21Z.

CAVANAUGH


&&

.AVIATION...
/ISSUED 637 AM CDT SUN APR 26 2015/
FIRST CHALLENGE IS IFR STRATUS THAT IS MOVING NORTHWARD FROM
CENTRAL AND SOUTHEAST TEXAS. THIS CLOUD DECK SHOULD AFFECT DAL
AFTER 13Z...AND MAY CLIP GKY/DFW AS WELL. THIS MOISTURE LAYER IS
THIN AND STRATUS SHOULD ERODE BY 15Z OR 16Z.

VERY STEEP LAPSE RATES MOVE INTO THE AREA BY MIDDAY AND THERE IS
ACTUALLY REALLY GOOD MODEL AGREEMENT IN BRINGING A PLUME OF MID
LEVEL MOISTURE AND LIFT INTO THE AREA EARLY-MID AFTERNOON. THIS
SHOULD BE SUFFICIENT FOR HIGH BASED OR ELEVATED THUNDERSTORMS AS
THERE IS ABOUT 400-700 J/KG OF INSTABILITY FROM PARCELS LIFTED
NEAR 12000FT. DRY AIR BELOW THIS ACTIVITY WILL EXIST AND WOULD
ENHANCE TURBULENCE AND SURFACE WIND GUSTS...EVEN IF THERE IS
LITTLE RAINFALL. WILL SHOW A 2 HOUR WINDOW OF VCTS FOR THIS WAVE
OF ACTIVITY FROM 20-22Z...BUT TIMING IS NOT CERTAIN AT THIS POINT.

THE SURFACE AIRMASS WILL CONTINUE TO DESTABILIZE DURING THE LATE
AFTERNOON AND EVENING HOURS AS MOISTURE INCREASES. THIS WILL OPEN
THE DOOR FOR SURFACE BASED CONVECTION MOVING IN FROM THE WEST
AFTER IT FIRES ON THE DRY LINE. CONFIDENCE IS NOT ESPECIALLY HIGH
THAT THIS ROUND OF ACTIVITY WILL IMPACT TAF SITES...BUT SINCE
THERE IS THE POTENTIAL FOR SEVERE STORM WILL SHOW VCTS FROM 00Z TO
04Z. RAIN AND THUNDERSTORM CHANCES INCREASE IN THE LATE EVENING
AND OVERNIGHT HOURS WHEN A MORE SOLID LINE OF STORMS SHOULD
DEVELOP AND MOVE IN FROM THE WEST. THIS IS WHEN UPPER FORCING WILL
BE STRONGEST. WILL SHOW TSRA FROM 4Z-9Z.

AFTER THAT WILL LEAVE THUNDER OUT OF TAFS DUE TO LOW
CONFIDENCE...BUT KEEP SHOWERS MENTIONED WITH MVFR CIGS PREVAILING
BEHIND THE FRONT.

TR.92


&&




.SYNOPSIS...
THE FIRST PORTION OF TODAY WILL BE QUITE SIMILAR TO
SATURDAY...WITH VERY WARM AND PLEASANT CONDITIONS. ONE DIFFERENCE
WILL BE THE INCREASE IN LOW LEVEL MOISTURE IN RESPONSE TO THE
APPROACH OF AN UPPER LEVEL LOW. THIS WILL SET THE STAGE FOR ACTIVE
WEATHER THIS AFTERNOON THROUGH MONDAY...THEREAFTER...A MORE
TRANQUIL PATTERN IS IN STORE FOR NORTH/CENTRAL TEXAS.

&&

.SHORT TERM...
THE MAIN CHALLENGE FOR THE SHORT TERM FORECAST WILL
BE THE POTENTIAL FOR MULTIPLE ROUNDS OF CONVECTION /SOME STRONG TO
SEVERE/ ACROSS THE WESTERN TWO THIRDS OF NORTH/CENTRAL TEXAS. WATER
VAPOR IMAGERY AT THIS HOUR REVEALED THAT THE MAIN UPPER LOW THAT
WILL BE RESPONSIBLE FOR TODAY/S SEVERE WEATHER CHANCES WAS LOCATED
ACROSS SOUTHERN ARIZONA. THIS VERY DYNAMIC TROUGH WILL CONTINUE
TO MOVE EASTWARD BEFORE CLOSING OFF LATER TODAY. LOW LEVEL
MOISTURE WILL CONTINUE TO STREAM NORTHWARD INTO THE AREA BENEATH A
STOUT EML THAT IS SIMULTANEOUSLY ADVECTING EASTWARD OFF OF THE
HIGHER TERRAIN. THE STEEP LAPSE RATES ASSOCIATED WITH THE EML IN
CONJUNCTION WITH THE ASCENT PRODUCED BY THE APPROACHING UPPER
LOW /AS EVIDENCED BY 30 TO 40 METER HEIGHT FALLS/ SHOULD SUPPORT
THE DEVELOPMENT OF ELEVATED CONVECTION MID TO LATE MORNING MAINLY
ALONG AND WEST OF A BOWIE TO GLEN ROSE TO KILLEEN LINE. THE STEEP
LAPSE RATES COMBINED WITH SUFFICIENT EFFECTIVE LAYER SHEAR MAY
SUPPORT A MARGINALLY SEVERE HAIL THREAT IN THE MORNING...SHOULD
STORMS DEVELOP.

DURING THE AFTERNOON HOURS...ADDITIONAL CONVECTION IS EXPECTED TO
DEVELOP AS A 100 KT UPPER LEVEL JET NOSES INTO THE SOUTHERN TX
PANHANDLE AND A VORTICITY LOBE ROTATES AROUND THE BASE OF THE MAIN
TROUGH OUT INTO WESTERN NORTH TEXAS. DURING THIS TIME...THE DRYLINE
WILL CONTINUE TO SHARPEN NEAR THE BIG COUNTRY. THE STRONG
LIFT...DIURNAL HEATING...AND INCREASING MOISTURE SHOULD ERODE
SURFACE BASED CONVECTIVE INHIBITION. VERY HIGH CAPE VALUES ON THE
ORDER OF 2500-3000 J/KG....MID LEVEL LAPSE RATES APPROACHING 8
C/KM AND 0-6 KM BULK SHEAR VALUES ON THE ORDER OF 45 TO 50 KNOTS
WILL EASILY SUPPORT A LARGE AND DAMAGING HAIL THREAT. AS THE
STORMS MOVE EAST AND NORTHEAST...GENERALLY BEYOND A BOWIE TO
MINERAL WELLS TO WACO LINE THIS AFTERNOON...THE LOW LEVEL AIRMASS
WILL BECOME INCREASINGLY DRIER WHICH INCREASES THE POTENTIAL FOR
DESTRUCTIVE STRAIGHT LINE WINDS.

WHILE TORNADOES WILL BE POSSIBLE WITH STORMS NEAR AND JUST EAST OF
THE DRYLINE THIS AFTERNOON...THIS THREAT ACTUALLY INCREASES DURING
THE EARLY EVENING HOURS AS LOW LEVEL WINDS INCREASE AND BACK IN
RESPONSE TO THE UPPER LOW MOVING INTO WEST TEXAS. THIS SHOULD
RESULT IN LARGE HODOGRAPHS WHILE CINH IS STILL LOW. AN ENHANCED
TORNADO RISK MAY DEVELOP ACROSS OUR SOUTHWESTERN ZONES THAT WOULD
INCLUDE THE WACO/TEMPLE/KILLEEN AREAS.

UNLIKE MOST SEVERE EVENTS...WE EXPECT CONVECTION TO CONTINUE TO
FIRE THROUGH THE OVERNIGHT HOURS AS THE UPPER LEVEL LOW REMAINS
SITUATED ACROSS THE REGION. THIS WILL ALSO FOSTER AN INCREASING
HEAVY RAIN THREAT AS CONTINUED ADVECTION OF WARM MOIST AIR INTO
THE REGION IS EXPECTED.

THE BOTTOM LINE IS THAT ALL INTERESTS ACROSS NORTH AND CENTRAL TEXAS
NEED TO PAY PARTICULARLY CLOSE ATTENTION TO WEATHER CONDITIONS TODAY
AS THE POTENTIAL EXISTS FOR HIGH IMPACT SIGNIFICANT SEVERE WEATHER
IN THE FORM OF LARGE HAIL...DESTRUCTIVE WINDS...AND A FEW TORNADOES.

&&

.LONG TERM...
ADDITIONAL CHANCES FOR PRECIPITATION WILL REMAIN ON MONDAY AS THE
CLOSED LOW MEANDERS ACROSS THE REGION. A FRONTAL BOUNDARY WILL
STALL OUT NEAR THE RED RIVER AND MAY EVEN DRIFT SOUTHWARD. STRONG
LOW LEVEL THETA-E ADVECTION WILL CONTINUE TO TRANSPORT WARM MOIST
AIR NORTHWARD INTO PORTIONS OF NORTH/CENTRAL TEXAS. WITH THE LACK
OF A STRONG CAP...EXPECT WIDESPREAD TO NUMEROUS SHOWER AND
THUNDERSTORM ACTIVITY. THE WIDESPREAD NATURE OF SHOWERS AND STORMS
MAY MITIGATE THE LARGER SEVERE WEATHER POTENTIAL ON
MONDAY...EXCEPT ACROSS FAR SOUTHERN ZONES WHERE SOME HEATING WILL
BE POSSIBLE. PERHAPS THE LARGER THREAT WILL BE THE POTENTIAL FOR
HEAVY RAIN ON MONDAY AS PWAT VALUES ARE EXPECTED TO CLIMB TOWARDS
THE 1.15-1.25 INCH RANGE. FOR NOW WILL HOLD OFF ON ANY FLOOD
WATCHES PARTICULARLY FOR THE NORTHERN ZONES UNTIL WE GET CLOSER
TO THE EVENT. RAIN CHANCES SHOULD TAPER OFF BY TUESDAY MORNING AS
THE COLD FRONT PUSHES TOWARDS THE SOUTH AND THE UPPER FORCING
DEPARTS THE REGION. COOLER CONDITIONS CAN BE EXPECTED ON TUESDAY
AND WEDNESDAY WITH LITTLE TO NO CHANCES OF PRECIPITATION AS THE
OMEGA PATTERN ESTABLISHES ITSELF. THE NEXT CHANCE FOR RAIN MAY BE
TOWARDS THE BEGINNING OF MAY.

15-BAIN/TR.92

&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  84  61  71  54  64 /  40  70  70  60  20
WACO, TX              85  65  76  54  67 /  50  60  50  40  10
PARIS, TX             83  57  67  53  62 /  30  70  70  70  30
DENTON, TX            83  60  67  52  64 /  40  70  70  60  20
MCKINNEY, TX          83  59  68  53  64 /  40  70  70  70  20
DALLAS, TX            85  61  70  54  64 /  40  70  70  60  20
TERRELL, TX           85  61  71  55  64 /  40  60  70  70  20
CORSICANA, TX         85  65  73  54  65 /  30  60  60  60  20
TEMPLE, TX            86  65  80  54  67 /  50  60  40  40  10
MINERAL WELLS, TX     82  62  74  55  65 /  50  70  60  40  10

&&

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

&&

$$


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