Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS01 KWNS 290615
SWODY1
SPC AC 290613

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0113 AM CDT FRI APR 29 2016

VALID 291200Z - 301200Z

...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PORTIONS OF OK/NORTH TX
TO THE ARKLATEX...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SOUTHERN PLAINS TO
ARKLATEX/LOWER MS RIVER VALLEY...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS THE CENTRAL/SOUTHERN
PLAINS TO ARKLATEX/LOWER MS RIVER VALLEY...

...SUMMARY...
SEVERE THUNDERSTORMS ARE LIKELY TODAY AND TONIGHT ESPECIALLY ACROSS
PARTS OF OKLAHOMA AND TEXAS TO THE ARKLATEX REGION AND LOWER
MISSISSIPPI RIVER VALLEY.

...SYNOPSIS...
AN AMPLIFIED LARGE-SCALE PATTERN OVER MUCH OF THE CONUS WILL BE
HIGHLIGHTED BY THE NORTHEASTWARD-ADVANCEMENT OF A
CLOSED/INCREASINGLY NEGATIVE-TILT TROUGH FROM THE FOUR CORNERS AREA
EARLY TODAY TO THE CENTRAL HIGH PLAINS TONIGHT.

...SOUTHERN PLAINS TO ARKLATEX/LOWER MS RIVER VALLEY...
A HIGHLY COMPLEX FORECAST SCENARIO IS EXPECTED PARTICULARLY ACROSS
OK/NORTH TX THROUGH THE AFTERNOON/EVENING...WITH ADMITTEDLY
BELOW-AVERAGE CONFIDENCE IN FORECAST/SPATIAL DETAILS. THIS IS
LARGELY ATTRIBUTABLE TO UNCERTAINTIES REGARDING THE
EXTENSIVENESS/PERSISTENCE OF EARLY-DAY CONVECTION AND APPRECIABLE
SHORTER-TERM /24-36 HOUR/ DETERMINISTIC AND ENSEMBLE GUIDANCE
VARIABILITY.

SCATTERED THUNDERSTORMS...SOME POTENTIALLY STRONG/SEVERE AND CAPABLE
OF HAIL...ARE EXPECTED TO BE ONGOING THIS MORNING FROM THE TX/OK
PANHANDLES INTO PARTS OF THE BODY OF OK AND THE ARKLATEX REGION.
THESE STORMS WILL GENERALLY BE FOCUSED ALONG A NORTHWARD-SHIFTING
WARM FRONT...WHICH SHOULD ROUGHLY BE SITUATED ACROSS
WEST-CENTRAL/SOUTH-CENTRAL OK AND THE OK/TX RED RIVER VICINITY AND
ARKLATEX THIS AFTERNOON...ALTHOUGH PERSISTENT EARLY-DAY
CONVECTION/CLOUD COVER AND RELATED DIURNAL DIFFERENTIAL HEATING WILL
BE FACTORS IN EXACTLY WHERE THE WARM FRONT IS EFFECTIVELY LOCATED
LATER TODAY. MIDDLE 60S TO NEAR 70F SURFACE DEWPOINTS WILL BECOME
INCREASINGLY ESTABLISHED THIS AFTERNOON NEAR/SOUTH OF THIS WARM
FRONT...EAST OF AN EASTWARD-MOVING TX/SOUTHERN OK DRYLINE...AND EAST
OF A PACIFIC COLD FRONT WHICH WILL ACCELERATE EAST-SOUTHEASTWARD
TONIGHT ACROSS KS/OK AND WESTERN NORTH TX.

DEVELOPMENT/INTENSIFICATION OF SURFACE-BASED STORMS WILL BE POSSIBLE
THIS AFTERNOON/EARLY EVENING AS FAR WEST AS WEST/SOUTHWEST OK IN
VICINITY OF A SURFACE TRIPLE POINT...AND AS FAR EAST AS AR/LOWER MS
RIVER VALLEY WHERE MORNING STORMS COULD PERSIST/POSSIBLY GROW
UPSCALE DURING THE DAY. CURRENT THINKING IS THAT SEVERE HAIL WILL BE
THE MOST COMMON SEVERE THREAT OVERALL...POTENTIALLY FROM A MULTIPLE
ROUND OF STORMS IN SOME SUB-REGIONAL AREAS INCLUDING PARTS OF OK AND
THE ARKLATEX. TORNADO POTENTIAL...AT LEAST IN A CONDITIONAL
SENSE...SHOULD BE MAXIMIZED IN A ROUGHLY WSW/ESE-ORIENTED
NEAR-WARM-FRONT CORRIDOR ACROSS THE SOUTHERN HALF OF OK/FAR NORTH TX
AND PARTS OF THE ARKLATEX. ALTHOUGH LOW-LEVEL SHEAR FORECASTS VARY
CONSIDERABLY AMONG AVAILABLE RAP/GFS AND MORE-AGGRESSIVE NAM
GUIDANCE...SOMEWHAT HIGHER TORNADO PROBABILITIES /10 PERCENT/ APPEAR
WARRANTED NEAR THE WARM FRONT...BUT SUBSEQUENT SPATIAL ADJUSTMENTS
CAN BE EXPECTED PENDING MESOSCALE DETAILS AND A RESOLUTION TO
CURRENT FORECAST UNCERTAINTIES.

FARTHER SOUTH...OF SOMEWHAT GREATER SPATIAL/TIMING FORECAST
CERTAINTY WILL BE FOR STORMS TO DEVELOP/INCREASE THIS AFTERNOON
ACROSS MUCH OF NORTH/CENTRAL TX IN VICINITY OF THE NNE/SSW-ORIENTED
DRYLINE. STRONG VERTICAL SHEAR /40+ KT/ AND MODERATE INSTABILITY
WILL SUPPORT SUPERCELLS CAPABLE OF LARGE HAIL AND POSSIBLY A COUPLE
OF TORNADOES THIS AFTERNOON AND EVENING.

..GUYER/PICCA.. 04/29/2016

$$


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