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Severe Storm Outlook Narrative (AC)
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ACUS03 KWNS 260730
SWODY3
SPC AC 260729

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0229 AM CDT SUN MAY 26 2013

VALID 281200Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS FOR A LARGE PORTION OF THE
PLAINS EASTWARD INTO THE WESTERN GREAT LAKES...

...SYNOPSIS...
THE UPPER PATTERN ON TUESDAY IS CHARACTERIZED AS COMPROMISING OF
SEVERAL SHORTWAVE IMPULSES EMBEDDED WITHIN BROAD SWLY FLOW OVER THE
PLAINS/MIDWEST DOWNSTREAM OF AN AMPLIFYING WRN U.S. UPPER TROUGH.  A
SURFACE LOW OVER THE CNTRL HIGH PLAINS WILL REMAIN QUASI-STATIONARY
AS MOIST SLY LOW LEVEL FLOW INTENSIFIES --E OF A NORTH-SOUTH
DRYLINE-- FROM TX NWD INTO THE CNTRL PLAINS AND MIDWEST DURING THE
PERIOD.  A WARM FRONTAL ZONE IS FORECAST TO ADVANCE NWD OVER A
PORTION OF THE MIDWEST AND INTO THE GREAT LAKES REGION.  FARTHER
W...A SURFACE TROUGH WILL EXTEND TO ANOTHER LOW OVER WY.

...PLAINS...
STRENGTHENING H5 FLOW OVER A LARGE PORTION OF THE PLAINS AND
WIDESPREAD MID 60S BOUNDARY LAYER DEWPOINTS E OF THE DRYLINE WILL
POTENTIALLY BE MORE FAVORABLE FOR STRONG/SEVERE STORMS TUESDAY
COMPARED TO PRIOR DAY/S.  MODELS SHOW A PLUME OF STEEP H7-H5 LAPSE
RATES /IN EXCESS OF 8 DEG C/KM/ ENVELOPING A LARGE PART OF THE
SRN-CNTRL PLAINS INTO THE MID MO VALLEY REGION.  COUPLED WITH STRONG
DIURNAL HEATING IN WAKE OF ANY EARLY DAY TSTM ACTIVITY --MOST LIKELY
OVER THE MID-LOWER MO VALLEY-- WILL PROBABLY RESULT IN A MODERATE TO
VERY UNSTABLE AIRMASS BY PEAK HEATING /2000-3500 J/KG MLCAPE/.
ORGANIZED STRONG-SEVERE STORMS CAPABLE OF LARGE HAIL/DMGG WINDS AND
A FEW TORNADOES WOULD BE POSSIBLE WITH THE MORE INTENSE
SUPERCELLS/LINEAR STRUCTURES.  A 50 KT LLJ IS FORECAST TO DEVELOP
OVER THE CNTRL PLAINS BY EVENING...AND LIKELY AID IN SUSTAINING AN
ISOLD SEVERE THREAT INTO THE OVERNIGHT.

...MIDWEST/WRN GREAT LAKES...
A BELT OF STRONG SWLY H85 FLOW WILL SERVE AS THE PRIMARY IMPETUS FOR
INCREASING LOW LEVEL MOISTURE WITH DEWPOINTS RISING INTO THE 60S.
THIS WILL OCCUR COINCIDENT WITH A NWD ADVANCING WARM FRONT AND
RESULT IN A DESTABILIZING AIRMASS.  ISOLD OCCURRENCES OF LARGE HAIL
AND DMGG WINDS WILL BE THE PRIMARY THREATS WITH THESE STORMS...BUT A
FEW TORNADOES ARE POSSIBLE...ESPECIALLY IF SURFACE-BASED STORMS CAN
DEVELOP/ROOT NEAR THE WARM FRONT IN A STRONGER LOW LEVEL SHEAR
ENVIRONMENT.

..SMITH.. 05/26/2013
National Weather Service Weather Forecast Office
