Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS01 KWNS 261629
SWODY1
SPC AC 261628

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1128 AM CDT SUN APR 26 2015

VALID 261630Z - 271200Z

...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF NRN AND CNTRL
TX...

...THERE IS AN ENH RISK OF SVR TSTMS FROM NRN INTO CNTRL AND ERN
TX...

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE SRN PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS OVER THE SRN PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS OVER A PART OF THE FL
PENINSULA...

...THERE IS A MRGL RISK OF SVR TSTMS OVER SC...

...SUMMARY...
SCATTERED SEVERE THUNDERSTORMS ARE EXPECTED OVER PARTS OF THE
SOUTHERN PLAINS THIS AFTERNOON THROUGH TONIGHT...WITH THE STORMS
SPREADING SOUTH AND EAST TOWARD THE TEXAS GULF COAST EARLY MONDAY.
VERY LARGE HAIL...TORNADOES...A COUPLE OF WHICH COULD BE
STRONG...AND DAMAGING WINDS WILL ACCOMPANY THESE STORMS. ISOLATED
STRONG TO POTENTIALLY SEVERE STORMS ALSO MAY OCCUR THIS AFTERNOON
OVER PARTS OF SOUTH CAROLINA AND FLORIDA.

...SYNOPSIS...

THE SRN SEGMENT OF AN AMPLIFIED TROUGH OVER THE INTERIOR WEST WILL
FORM A CLOSED UPPER LOW WHICH WILL DEVELOP FROM THE SRN ROCKIES INTO
SRN HIGH PLAINS BY 12Z/MONDAY.  AN ASSOCIATED 70-80 KT MID-LEVEL JET
STREAK CURRENTLY ROUNDING THE TROUGH BASE OVER NWRN MEXICO WILL
DEVELOP EWD INTO CNTRL TX WITHIN THE SRN SEMICIRCLE OF THE EVOLVING
LOW.

AT THE SURFACE...A LEE CYCLONE OVER ERN NM WILL DEVELOP GENERALLY
ESEWD INTO CNTRL TX IN RESPONSE TO THE EVOLVING UPPER LOW WITH A
DRYLINE BECOMING ESTABLISHED BY AFTERNOON FROM THE VICINITY OF THE
SURFACE LOW SWD INTO THE EDWARDS PLATEAU.  MEANWHILE...A BACKING AND
STRENGTHENING LOW-LEVEL FLOW REGIME WILL PROMOTE THE NWD MOVEMENT OF
A WARM FRONT THROUGH THE RED RIVER VALLEY.

...SRN PLAINS TODAY THROUGH TONIGHT...

MID-MORNING SATELLITE DATA INDICATE A BELT OF IMPLIED ASCENT
SPREADING EWD THROUGH FAR WRN TX AND FAR ERN NM IN ASSOCIATION WITH
A LEAD VORTICITY MAXIMUM PRECEDING THE MAIN UPPER-AIR SYSTEM.  AT
THE SAME TIME...AN INCREASINGLY MOIST BOUNDARY LAYER IS RAPIDLY
DEVELOPING NWD THROUGH W-CNTRL TX ALONG AND TO THE S OF THE WARM
FRONT AND BENEATH A PLUME OF STEEP MID-LEVEL LAPSE RATES /SEE 12Z
DRT SOUNDING/.  THE OVERLAP OF THESE PROCESSES SHOULD FOSTER AN
INCREASE IN MAINLY ELEVATED TSTMS LATE THIS MORNING INTO AFTERNOON
NWD THROUGH THE RED RIVER VALLEY.  INCREASING CLOUD-BEARING SHEAR
AND THE DESTABILIZING ENVIRONMENT WILL PROMOTE VIGOROUS UPDRAFTS
WITH A RISK FOR PRIMARILY LARGE HAIL.  FOR ADDITIONAL
INFORMATION...SEE MCD 465.

IN THE WAKE OF THIS EARLY-DAY ACTIVITY OR ALONG ITS SRN
FLANK...SURFACE-BASED STORM DEVELOPMENT IS EXPECTED TO OCCUR BY MID
TO LATE AFTERNOON INTO EVENING FROM THE VICINITY OF THE SURFACE
TRIPLE POINT OVER NWRN TX SWD ALONG THE DRYLINE.  THIS ACTIVITY WILL
BE ENCOURAGED BY THE FORCING FOR ASCENT WITHIN THE EXIT REGION OF
THE MID-LEVEL JET STREAK EMERGING FROM SWRN TX WHERE THE COMBINATION
OF 1500-2000+ J/KG MLCAPE AND STEADILY STRENGTHENING LOW-LEVEL AND
DEEP-LAYER SHEAR WILL PROMOTE INTENSE SUPERCELLS CAPABLE OF VERY
LARGE HAIL AND TORNADOES...SOME OF WHICH COULD BE STRONG.

EXPECT STORMS TO GROW UPSCALE INTO ONE OR MULTIPLE MCSS OVERNIGHT
WITH THE RISK FOR POTENTIALLY MORE WIDESPREAD DAMAGING WINDS
INCREASING ACROSS PORTIONS OF CNTRL INTO ERN TX.  LARGE HAIL AND A
FEW TORNADOES WILL ALSO REMAIN A CONCERN.

...FL TODAY...

TSTMS HAVE INCREASED IN AREAL COVERAGE THIS MORNING ALONG A RESIDUAL
OUTFLOW BOUNDARY/CONFLUENCE ZONE FROM THE FAR NERN GULF OF MEXICO
EWD ALONG AN OCF-DAB LINE.  TO THE SOUTH OF THIS ACTIVITY...DIABATIC
SURFACE HEATING IN CONJUNCTION WITH BOUNDARY-LAYER DEWPOINTS IN THE
LOWER 70S SHOULD RESULT MODERATE AFTERNOON INSTABILITY AMIDST A
KINEMATIC ENVIRONMENT EXHIBITING A RELATIVELY STRONG WLY DEEP-LAYER
WIND FIELD.  AS SUCH...THE POTENTIAL WILL EXIST FOR SOME SUPERCELL
AND/OR BOWING STRUCTURES CAPABLE OF MAINLY DAMAGING WIND GUSTS.

FOR ADDITIONAL NEAR-TERM GUIDANCE...SEE MCD 464.

...SC THIS AFTERNOON...

HEATING OF A MOIST AIR MASS PRECEDING A SWD-MOVING COLD FRONT WILL
SUPPORT THE DEVELOPMENT OF STEEP LOW-LEVEL LAPSE RATES AND AT LEAST
A MARGINALLY UNSTABLE AIR MASS LATER TODAY.  DIRECT THERMAL
CIRCULATIONS ARISING FROM DIFFERENTIAL HEATING ALONG THE FRONT
SHOULD FOSTER A FEW STORMS BY AFTERNOON WITH LOCALLY STRONG WIND
GUSTS POSSIBLE OWING TO THE DOWNWARD TRANSPORT OF STRONG WNWLY FLOW
ALOFT.

..MEAD/GLEASON.. 04/26/2015



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