Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 291946
SWODY1
SPC AC 291944

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0244 PM CDT FRI APR 29 2016

VALID 292000Z - 301200Z

...THERE IS AN ENH RISK OF SVR TSTMS ACROSS CNTRL AND NRN TX...SRN
OK...AND THE ARKLATEX...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN PLAINS INTO THE
LOWER MS VALLEY...

...THERE IS A MRGL RISK OF SVR TSTMS FROM TX TO AL...

...SUMMARY...
SEVERE THUNDERSTORMS ARE LIKELY TODAY AND TONIGHT FROM PORTIONS OF
THE SOUTHERN PLAINS EASTWARD ACROSS THE ARKLATEX REGION TO THE LOWER
MISSISSIPPI RIVER VALLEY.

...SRN PLAINS INTO THE LOWER MS VALLEY...
NUMEROUS AREAS OF THUNDERSTORMS CONTINUE TO EVOLVE ACROSS THE SRN
PLAINS AND LOWER MS VALLEY WITH THE MAIN SEVERE THREAT CENTERED OVER
CNTRL AND NRN TX...SRN OK...AND INTO THE ARKLATEX.

AN EXTREMELY MOIST AND UNSTABLE AIR MASS REMAINS IN PLACE E OF THE
ADVANCING DRYLINE WHICH CURRENTLY EXTENDS SWWD FROM A LOW OVER SWRN
OK ACROSS W CNTRL TX...AND S OF A WARM FRONT LOCATED ACROSS SRN OK.
18Z SOUNDING FROM FWD ALSO SHOWS A FAVORABLE HODOGRAPH FOR
SUPERCELLS WITH SUFFICIENT LOW-LEVEL SHEAR AND STRONG INSTABILITY.
HAIL IS THE MOST LIKELY THREAT...WITH A FEW TORNADOES POSSIBLE
DEPENDING ON THE DEGREE OF STORM INTERACTION.

TO THE N...A CLUSTER OF CELLS IS RAPIDLY EVOLVING OVER SWRN
OK...CLOSE TO THE SFC LOW. THESE CELLS HAVE LARGELY BEEN N OF THE
MAIN COLD FRONT...BUT HAVE SHOWN SIGNS OF EWD PROPAGATION WHICH MAY
MAINTAIN DEVELOPMENT CLOSE TO THE SFC-BASED INFLOW. IN
ADDITION...THETA-E ADVECTION CONTINUES OVER SRN INTO CNTRL OK AS
WELL. VERY LARGE HAIL WILL BE POSSIBLE WITH SOME OF THESE
CELLS...ALONG WITH DAMAGING WINDS. STORM MODE IS COMPLEX BUT A
TORNADO OR TWO IS POSSIBLE ESPECIALLY WITH CELLS MAINTAINING
POSITION ALONG THE SW-NE ORIENTED BOUNDARY.

..JEWELL.. 04/29/2016

.PREV DISCUSSION... /ISSUED 1130 AM CDT FRI APR 29 2016/

...SRN PLAINS TO LOWER MS VALLEY THROUGH TONIGHT...
A MIDLEVEL SHORTWAVE TROUGH OVER NM THIS MORNING WILL PIVOT ENEWD
OVER THE SRN HIGH PLAINS THIS AFTERNOON...AND REACH THE I-35
CORRIDOR IN OK/KS LATE TONIGHT.  AN ASSOCIATED SURFACE CYCLONE WILL
DEVELOP ENEWD FROM NW TX TO SW OK THIS EVENING...AND THEN CONTINUE
NEWD INTO KS OVERNIGHT.  FARTHER E...A BAROCLINIC ZONE HAS BEEN
REINFORCED BY OVERNIGHT/MORNING ELEVATED CONVECTION FROM OK INTO AR.
S OF THE BOUNDARY...NEAR SEASONAL MAXIMUM BOUNDARY LAYER MOISTURE IS
PRESENT /LOW-MID 70S DEWPOINTS AND MEAN MIXING RATIOS OF 15-19 G PER
KG/.  THIS MOISTURE...COMBINED WITH RESIDUAL STEEP MIDLEVEL LAPSE
RATES AND SOME SURFACE HEATING IN CLOUD BREAKS...WILL SUPPORT STRONG
BUOYANCY TODAY IN THE WARM SECTOR.

DEEP-LAYER VERTICAL SHEAR WILL BE FAVORABLE FOR SUPERCELLS IN THE
WARM SECTOR WITH EFFECTIVE BULK SHEAR AOA 45 KT.  A SUBTLE LEAD WAVE
NOTED IN VWP DATA ACROSS W/NW TX IN THE 850-700 MB LAYER WILL LIKELY
HELP FOCUS NEW THUNDERSTORM DEVELOPMENT THIS AFTERNOON IN THE WARM
SECTOR NEAR THE I-35 CORRIDOR IN TX.  STRONG BUOYANCY...RICH
LOW-LEVEL MOISTURE...AND SUFFICIENT LOW-LEVEL SHEAR /EFFECTIVE SRH
OF 150-200 M2 PER S2/ WILL SUPPORT THE RISK FOR TORNADOES...ISOLATED
VERY LARGE HAIL...AND A FEW DAMAGING GUSTS.  FARTHER N...THE
BAROCLINIC ZONE MAY DRIFT NWD AS A WARM FRONT INTO SRN OK...THOUGH
CONTINUING ELEVATED CONVECTION AND WIDESPREAD CLOUDS WILL LIKELY
LIMIT NWD PROGRESS OF THE WARM SECTOR UNTIL THE SURFACE CYCLONE
MOVES FARTHER N BY TONIGHT.  LOW-LEVEL SHEAR WILL BE STRONGER INVOF
THE WARM FRONT...AND THERE WILL BE A RISK FOR SUPERCELLS/TORNADOES
WITH STORMS INTERACTING WITH THE WARM FRONT/OUTFLOW.  LOW-LEVEL
SHEAR WILL BE MOST FAVORABLE FOR ROTATING STORMS ALONG THE RED RIVER
FROM ABOUT I-35 EWD INTO SW AR.

THE SEVERE THREAT BECOMES A BIT MORE UNCERTAIN CLOSER TO THE SURFACE
LOW INTO SW OK.  NWD PROGRESS OF THE WARM SECTOR IS A BIT
UNCERTAIN...AND VWP/S ARE ALREADY BEGINNING TO SHOW THE INFLUENCE OF
THE LEAD WAVE ON WIND PROFILES WITH THE MIDLEVEL BACKING.  THERE IS
SUBSTANTIAL DISAGREEMENT AMONG NUMERICAL GUIDANCE REGARDING THE
DETAILS OF BUOYANCY AND VERTICAL SHEAR ACROSS SW AND S CENTRAL OK
THROUGH THIS EVENING...SO THE SPECIFIC EXPECTED STORM STRUCTURES ARE
LIKEWISE UNCERTAIN.  WILL MAINTAIN PART OF ENH RISK INTO SW OK FOR
SUPERCELL POTENTIAL WITH HAIL/WIND...AS WELL AS A COUPLE OF
TORNADOES...SINCE RECENT MESONET OBS DO SUGGEST WARMING AND
MOISTENING IS OCCURRING.

FARTHER E IN AR...THE LARGE OVERNIGHT MCS PERSISTS WITH AN MCV OVER
N CENTRAL AR...AND STRONGER CONVECTION ALONG THE OUTFLOW BOUNDARY
ACROSS SRN AR.  IT SEEMS LIKELY THAT THIS OUTFLOW WILL REMAIN
QUASI-STATIONARY OR EVEN DRIFT SWD/SEWD AS A RESULT ON CONTINUING
OUTFLOW REINFORCEMENT BY CONVECTION THROUGH THE AFTERNOON.  OTHER
WARM SECTOR STORMS HAVE FORMED IN NW LA WITHIN THE MOIST AXIS...AND
MORE SUCH DEVELOPMENT MAY OCCUR THROUGH THE AFTERNOON INTO NE TX AND
NW LA.  BUOYANCY/SHEAR PARAMETER SPACE WILL FAVOR A HAIL RISK WITH
ANY SUSTAINED STORMS...ALONG WITH DAMAGING GUSTS AND A FEW
TORNADOES.

$$



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