SWODY1
SPC AC 241958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT SUN JUN 24 2007
VALID 242000Z - 251200Z
..THERE IS A MDT RISK OF SVR TSTMS OVER SOUTH CENTRAL/SERN MT AND
SWRN ND...
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF MT INTO THE NRN
PLAINS...
..MT/NWRN SD/ND/NWRN MN...
UPPER LEVEL PACIFIC TROUGH WILL SHIFT INLAND OVER THE NWRN STATES...
WITH BAND OF 50 KT SWLY MID LEVEL FLOW EXTENDING FROM THE BASE OF
THIS TROUGH OVER NRN CA INTO ERN MT. THIS FLOW SHOULD STRENGTHEN
FURTHER AS UPPER TROUGH BECOMES MORE NEGATIVELY TILTED THIS FORECAST
PERIOD AND THUS MAINTAIN STRONG DEEP LAYER SHEAR ALREADY IN PLACE
FROM THE NRN ROCKIES EWD TO ND/NRN MN. EARLY AFTERNOON SURFACE
ANALYSIS PLACE A FRONT FROM FAR NWRN MN SWWD BISECTING ND AND THEN
INTO FAR NRN WY...AND NWWD INTO WRN MT.
AIR MASS HAS BECOME MODERATELY TO VERY UNSTABLE /MLCAPE 2000-3000
J/KG/ IN THE VICINITY OF THIS BOUNDARY AND ALSO NWD INTO PARTS OF
CENTRAL/ERN MT. UPSLOPE FLOW INTO THE HIGHER TERRAIN OF SWRN MT
INTO NRN WY AND SWD TO SERN WY/CO COMBINED WITH STRONG SURFACE
HEATING HAS ALLOWED CU TO FORM OVER THIS TERRAIN. ADDITIONAL CU/
TSTM DEVELOPMENT IS LIKELY THIS AFTERNOON...GIVEN FURTHER SURFACE
HEATING. TSTMS WILL EVENTUALLY MOVE OFF THE HIGHER TERRAIN INTO THE
STRONGER INSTABILITY AT LOWER ELEVATIONS AND STRONG DEEP LAYER SHEAR
RESULTING IN SEVERE TSTMS. GIVEN DEGREE OF INSTABILITY/ SHEAR
VALUES...POTENTIAL EXISTS FOR TORNADOES...VERY LARGE HAIL AND
DAMAGING WINDS...ESPECIALLY WITH INITIAL ACTIVITY IN THE FORM OF
SUPERCELLS. DAMAGING WIND THREAT SHOULD BECOME MORE PRONOUNCED ONCE
STORMS EVOLVE INTO ONE OR TWO MCSS/BOW ECHOES AND RACE NEWD INTO ERN
MT/WRN MT AND POSSIBLY NWRN SD. SHOULD COLD POOL BECOME
WELL-ESTABLISHED WITH MCS MOVING OUT OF THE NRN HIGH PLAINS...WIND
DAMAGE THREAT WOULD CONTINUE NEWD OVER MUCH OF ND OVERNIGHT.
ADDITIONAL SEVERE MCS WITH ELEVATED SUPERCELLS MAY EVOLVE OVER
CENTRAL/ERN ND OVERNIGHT ALONG NOSE OF 40+ KT SLY LLJ. LARGE HAIL
AND ISOLATED WIND DAMAGE MAY ACCOMPANY THESE STORMS.
SEVERE PROBABILITIES HAVE BEEN INCREASED FARTHER S INTO PARTS OF ERN
WY/WRN SD AND NWRN NEB...AND ADDED TO THE SLIGHT RISK AREA... GIVEN
GREATER POTENTIAL FOR SEVERE STORMS WHERE STRONG SURFACE HEATING
WILL LIKELY ERODE CAP FOR AT LEAST A FEW SURFACE BASED STORMS THIS
AFTERNOON AND EVENING.
..SRN PLAINS INTO THE OZARKS/MID SOUTH TO THE SOUTHEAST COAST...
WATER VAPOR IMAGERY CONTINUED TO SHOW SEVERAL SLOW MOVING IMPULSES
OVER THE SRN PLAINS INTO THE MID SOUTH/OH RIVER VALLEY...AND ONE
TRACKING EWD ALONG THE LA COAST. CLUSTERS OF TSTMS HAVE ALREADY
DEVELOPED IN THE VICINITY OF EACH OF THESE IMPULSES AND ALONG SEA
BREEZE BOUNDARIES FROM FL TO THE CAROLINAS. WEAK DEEP LAYER SHEAR
WITH MODERATE INSTABILITY AND STEEP LOW LEVEL LAPSE RATES SUGGEST
GREATEST THREAT WITH THESE PULSE-TYPE TSTMS SHOULD BE LOCALLY STRONG
WIND GUSTS. ALTHOUGH A FEW STORMS MAY PRODUCE HAIL...WARMER AIR
ALOFT SHOULD CONTINUE TO TEMPER THIS THREAT.
.PETERS.. 06/24/2007
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