SPC AC 121239
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0739 AM CDT SUN JUL 12 2009
VALID 121300Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL HIGH PLAINS
INTO THE MID SOUTH/TN VALLEY...
...CNTRL HIGH PLAINS/CNTRL AND NRN PLAINS/MID-MO VALLEY...
COMPLEXES ONGOING OVER NERN KS AND SERN SD MAY CONTINUE SEWD THROUGH
THE MORNING ALONG PERIPHERY OF SRN HIGH PLAINS MID LEVEL
ANTICYCLONE. REGION WILL REMAIN WITHIN MODERATE TO STRONG NWLY FLOW
ALOFT AND THEREFORE SUSTAIN SUFFICIENT ORGANIZATION FOR SEVERE
THUNDERSTORMS...WITH SEVERITY AND LONGEVITY DEPENDING ON AVAILABLE
INSTABILITY. THERE REMAINS SOME CONCERN ATTM THAT BOWING COMPLEX
APPROACHING NWRN MO AT 13Z COULD SUSTAIN ITSELF AND INCREASE SEWD
TOWARDS THE MID SOUTH TODAY IF SUFFICIENT HEATING CAN BREAK CAP
ALONG SURGING OUTFLOW. THIS WOULD SUGGEST A MORE WIDESPREAD SEVERE
THREAT ACROSS PORTIONS OF MO. REGARDLESS... ADDITIONAL DEVELOPMENT
OF SEVERE STORM CLUSTERS/MCSS CAN BE EXPECTED THROUGH THE PERIOD
EVOLVING TO THE NORTHWEST INVOF HIGHER TERRAIN OVER THE HIGH PLAINS
AND/OR INVOF SURFACE FRONT/BOUNDARIES ALONG FRINGE OF STRONG WNWLY
FLOW ALOFT. CONSIDERABLE UNCERTAINTY REMAINS REGARDING DETAILS OF
ACTUAL SEVERE MCS DEVELOPMENT AND TRACKS. THEREFORE...WILL EXPAND A
BROAD SLGT RISK AND ACCOMPANYING HIGHER SEVERE PROBABILITIES FROM
THE HIGH PLAINS REGION SSEWD INTO THE MID SOUTH/TN VALLEY WITH
LIKELIHOOD OF SEVERAL ROUNDS OF STRONG/SEVERE STORMS CONTINUING
THROUGH EARLY MONDAY.
...ERN CAROLINAS/SE VA/SRN MD...
AN UPPER-LEVEL TROUGH IS FORECAST TO MOVE EWD ACROSS THE NERN STATES
TODAY AS A QUASI-STATIONARY FRONT REMAINS IN PLACE EWD FROM THE
CNTRL APPALACHIANS INTO THE MID-ATLANTIC. ALONG AND SOUTH OF THE
BOUNDARY...MODERATE INSTABILITY IS FORECAST AND SEVERAL MODELS
DEVELOP THUNDERSTORMS ALONG THE INSTABILITY AXIS THIS AFTERNOON.
FORECAST SOUNDINGS LATE THIS AFTERNOON ACROSS SERN VA AND ERN NC
SHOW 30 TO 40 KT OF VERTICAL SHEAR SUGGESTING AT LEAST A THREAT OF
SEVERE STORMS...INCLUDING SUPERCELLS AND SMALL LINES INTO THE
EVENING.
...PACIFIC NW/NRN ROCKIES...
FAIRLY STRONG MID/UPPER LEVEL TROUGH NOW OFF THE PAC NW COAST WILL
OVERSPREAD THE PAC NW THROUGH THE PERIOD...ENHANCING SWLY FLOW ALOFT
ACROSS THE NRN INTERMOUNTAIN REGION/NRN ROCKIES. IN
ADDITION...FETCH OF MODEST PWS EVIDENT THIS MORNING AHEAD OF THIS
IMPULSE WILL SUPPORT SCATTERED TO WIDELY SCATTERED HIGH-BASED TSTMS
ACROSS THE REGION...INCREASING THROUGH THE AFTERNOON.
FORECAST SOUNDINGS INDICATE STRONG VERTICAL SHEAR AND STEEP
MID-LEVEL LAPSE RATES...SUPPORTIVE OF A FEW MARGINALLY SEVERE
STORMS. HAIL AND DOWNBURSTS WILL BE POSSIBLE WITH THE STRONGER
STORMS.
..EVANS/HURLBUT.. 07/12/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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