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Severe Storm Outlook Narrative (AC)
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ACUS01 KWNS 180105
SWODY1
SPC AC 180103

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0803 PM CDT FRI MAY 17 2013

VALID 180100Z - 181200Z

...THERE IS A SLGT RISK OF SVR TSTMS CNTRL AL...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN
PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS OF CNTRL AND N-CNTRL
TX...

...NERN WY EASTWARD INTO ERN SD...
SEVERAL CLUSTERS OF STRONG-SEVERE STORMS LOCATED TO THE N-NW-W OF
THE BLACK HILLS AND OVER THE NEB SANDHILLS AND ADJACENT SD THIS
EVENING WILL CONTINUE TO POSE A MAINLY LARGE HAIL/SEVERE WIND GUST
THREAT THIS EVENING.  THE 00Z/18 RAP RAOB EXHIBITED A MORE THAN
ADEQUATE DEEP LAYER SHEAR PROFILE FOR STORM ORGANIZATION...INCLUDING
BOWING SEGMENTS AND SUPERCELLS.  AS A SURFACE LOW DEVELOPS EWD
TONIGHT FROM NERN WY INTO WRN SD ...AN INTENSIFYING LLJ/WAA OVER THE
CNTRL-NRN PLAINS WILL BECOME MORE FAVORABLE FOR UPSCALE GROWTH FOR
EXISTING CONVECTION.  SUBJECTIVE SURFACE MESOANALYSIS PLACES A
FRONTAL ZONE DRAPED EWD ACROSS SRN SD INTO NRN IA.  AS A
WELL-DEFINED MCV LOCATED S-CNTRL SD TRACKS EWD ALONG THIS
BOUNDARY...A PERSISTENT THREAT FOR LARGE HAIL/DMGG WIND GUSTS WILL
PROBABLY CONTINUE INTO THE OVERNIGHT IN AREAS DOWNSTREAM ACROSS
PORTIONS OF NRN NEB AND SD.

...PARTS OF AL/MS...
REMNANT MID LEVEL CIRCULATION LOCATED OVER THE LOWER OH/TN VALLEYS
WILL CONTINUE TO FOCUS A BELT OF STRONGER LOW LEVEL FLOW FROM THE
CNTRL GULF COAST THROUGH MUCH OF AL.  A STREAMLINE ANALYSIS SHOWS
LOW LEVEL DIFFLUENCE OVER THE LOWER MS VALLEY...SUGGESTIVE OF ANY
REGENERATIVE ACTIVITY WILL FAVOR THE AL/MS BORDER AND LOCALES E.
THE 00Z/18 BMX RAOB SHOWED A RATHER MOIST PROFILE /PW 1.75 IN./
CO-LOCATED WITH A SUFFICIENTLY ENLARGED HODOGRAPH THAT WILL PROBABLY
CONTINUE TO SUPPORT STORM ORGANIZATION...CAPABLE PRIMARILY OF A
LOCALLY DMGG WIND THREAT.

...PORTION OF N-CNTRL AND CNTRL TX...
RADAR MOSAIC SHOWS A FEW DISCRETE SUPERCELLS OVER WRN N-CNTRL TX AND
CNTRL TX EARLY THIS EVENING.  DESPITE A LESS THAN IDEAL SETUP FOR
STORM PERSISTENCE OWING MAINLY TO LITTLE IF ANY LARGE SCALE SUPPORT
ALOFT...A VERY STEEP RATE ENVIRONMENT SAMPLED BY THE 00Z/18 FWD/MAF
RAOBS WITHIN A MOISTURE RICH LOW LEVEL ENVIRONMENT WILL BE FAVORABLE
FOR AT LEAST A SHORT-TERM THREAT FOR LARGE TO VERY LARGE HAIL.
NOCTURNAL COOLING AND INCREASING CINH WILL GRADUALLY ACT TO WEAKEN
THE STORMS AS NEAR-SURFACE INFLOW PARCELS BECOME LESS ABLE TO REACH
THE LFC.  UNTIL THEN...A BRIEF WINDOW FOR LOW LEVEL MESOCYCLONES TO
PRODUCE A TORNADO MAY BE REALIZED.

..SMITH.. 05/18/2013

National Weather Service Regional Office