SWODY1
SPC AC 150559
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT WED SEP 15 2010
VALID 151200Z - 161200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL PLAINS/UPPER
MIDWEST/LOWER MO VALLEY...
...SYNOPSIS...
A QUASI-ZONAL LARGE SCALE FLOW REGIME WILL PERSIST OVER THE NORTHERN
HALF TO TWO-THIRDS OF THE CONUS THROUGH THE PERIOD. THIS PATTERN
WILL BE HIGHLIGHTED BY THE EAST-SOUTHEASTWARD ADVANCEMENT/MODEST
AMPLIFICATION OF A POTENT SHORTWAVE TROUGH...FROM THE NORTH-CENTRAL
ROCKIES/HIGH PLAINS TO THE MIDWEST/UPPER MS VALLEY BY LATE TONIGHT.
...CENTRAL PLAINS/MIDWEST/LOWER MO VALLEY...
INITIALLY...MULTIPLE ONGOING TSTM CLUSTERS AND POTENTIAL MCS/S WILL
BE ONGOING THIS MORNING...ONE AREA PROBABLY ACROSS EASTERN KS AND/OR
PERHAPS NORTHERN OK/WESTERN MO...IN ADDITION TO A CORRIDOR FROM SD
TO SOUTHERN MN/NORTHERN IA. IT IS POSSIBLE THAT SOME OF THIS
ACTIVITY COULD POSE A MODEST SEVERE HAIL/WIND THREAT THROUGH THE
MORNING...AIDED BY SUSTAINED DUAL SEGMENTS OF A LOW LEVEL
JET/ASSOCIATED WARM ADVECTION REGIME.
OTHERWISE...A WARM/MOIST AIRMASS WILL ATTEMPT TO RETREAT
NORTHEASTWARD ACROSS THE LOWER MO VALLEY/MIDWEST TODAY...AHEAD OF
THE APPROACHING/AMPLIFYING MID LEVEL TROUGH AND A MODESTLY DEEPENING
SURFACE LOW AND EAST-SOUTHEASTWARD ADVANCING COLD FRONT. OF
NOTE...THIS WARM SECTOR RETREAT MAY VERY WELL BE AUGMENTED BY EARLY
DAY/ONGOING TSTMS...WHICH PROVIDES LIMITED CERTAINTY ON THE TRUE
EXTENT OF AN APPRECIABLE WARM/MOIST SECTOR LATER TODAY.
NONETHELESS...IT IS CONCEIVABLE THAT EARLY DAY TSTMS WILL PERSIST
THROUGH THE DAY...WITH S/SW PERIPHERAL AND/OR NEAR-COLD FRONTAL
SUBSEQUENT DEVELOPMENT BY THIS AFTERNOON WITHIN A
RECOVERING/DESTABILIZING BOUNDARY LAYER. AMID UPPER 60S/LOWER 70S F
SURFACE DEWPOINTS AHEAD OF THE ADVANCING COLD FRONT...CURRENT
THINKING IS THAT THE GREATEST OPPORTUNITY FOR AFTERNOON
DESTABILIZATION/SEVERE TSTM DEVELOPMENT WILL OCCUR ACROSS PORTIONS
OF EASTERN KS/NORTHEAST OK TO WESTERN/CENTRAL MO.
FARTHER NORTH/NORTHEAST...GIVEN AFOREMENTIONED UNCERTAINTY REGARDING
PERSISTENCE OF EARLY DAY STORMS/EXTENT OF THE TRUE MARITIME WARM
SECTOR LATER TODAY...SURFACE BASED DESTABILIZATION THIS AFTERNOON IS
MORE UNCERTAIN ACROSS FAR EASTERN NEB/MUCH OF IA INTO THE UPPER MS
RIVER VALLEY. HOWEVER...ASIDE FROM A SEVERE HAIL THREAT EARLY
TODAY...OTHER SOMEWHAT LOWER TOPPED STORMS MAY DEVELOP/INCREASE THIS
AFTERNOON ALONG/AHEAD OF THE ADVANCING SURFACE LOW/COLD FRONT. IF
SUFFICIENT DESTABILIZATION OCCURS IN THESE AREAS /500-1000 J PER KG
MLCAPE OR GREATER/...A MULTI-FACETED SEVERE THREAT WOULD BE POSSIBLE
THIS AFTERNOON INTO THIS EVENING.
OVERALL...STRENGTHENING DEEP LAYER FLOW AND 35-40 KT OF DEEP LAYER
SHEAR WILL SUPPORT ORGANIZED STORM MODES INCLUDING SUPERCELLS/LINEAR
BOWING SEGMENTS WITH DAMAGING WINDS/SEVERE HAIL AS THE PRIMARY
HAZARDS. GIVEN THE SUSTENANCE OF MODERATELY STRONG LOW LEVEL
SOUTHWESTERLY FLOW THROUGH THE PERIOD...SOME TORNADO THREAT MAY
EXIST AS WELL...PERHAPS MAINLY AHEAD OF THE AFOREMENTIONED SURFACE
LOW/S AND/OR IN VICINITY OF THE EFFECTIVE WARM FRONT.
..GUYER/SMITH.. 09/15/2010
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