SWODY1
SPC AC 112000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT SAT JUN 11 2011
VALID 112000Z - 121200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND TONIGHT FOR
THE HIGH PLAINS INTO OK/KS AND THE OZARKS...
...THERE IS A SLGT RISK OF SVR TSTMS FOR CENTRAL/EASTERN PA SWD INTO
VA...
...HIGH PLAINS...
AIDED BY A LOW AMPLITUDE PERTURBATION AS NOTED PER WATER VAPOR
IMAGERY...OBSERVATIONAL GUIDANCE/SHORT-TERM TRENDS SUGGEST THAT
SCATTERED DEEP CONVECTION ONGOING ACROSS SOUTHEAST CO AT MID
AFTERNOON WILL CONTINUE TO INCREASE/EXPAND EASTWARD WITHIN A MOIST
SOUTHEASTERLY UPSLOPE REGIME/INSTABILITY AXIS ACROSS THE
SOUTH-CENTRAL PLAINS. REFERENCE MESOSCALE DISCUSSION 1183 AND
SUBSEQUENT WATCHES/MESOSCALE DISCUSSIONS. FARTHER NORTH...AN UPSWING
IN DEEP CONVECTION IS STILL ALSO EXPECTED ACROSS THE NORTH-CENTRAL
HIGH PLAINS OVER THE NEXT SEVERAL HOURS...REFERENCE MESOSCALE
DISCUSSION 1184 AND SUBSEQUENT DISCUSSIONS/WATCHES.
AS PREVIOUSLY DISCUSSED...GRADUALLY STRENGTHENING FLOW ALOFT/VEERING
WIND PROFILES ARE STILL EXPECTED TO SUPPORT SUPERCELLS CAPABLE OF
LARGE HAIL AND A COUPLE OF TORNADOES. LATER THIS
EVENING/OVERNIGHT...SOME SHORT-TERM NUMERICAL GUIDANCE UNCERTAINTY
EXISTS REGARDING THE SPATIAL LOCATIONS OF POTENTIAL MCS/S AND/OR
ELEVATED TSTMS...BUT THE MOST PROBABLE SCENARIO WOULD APPEAR TO BE
THE DEVELOPMENT OF AN MCS ACROSS SOUTHERN KS/NORTHERN OK WITH AT
LEAST SOME WIND DAMAGE/SEVERE HAIL THREAT...WITH OTHER ELEVATED
STORMS CAPABLE OF SEVERE HAIL POTENTIALLY ACROSS NORTHERN KS INTO
NEB AND ADJACENT PORTIONS OF THE MIDDLE MO VALLEY.
..GUYER.. 06/11/2011
.PREV DISCUSSION... /ISSUED 1138 AM CDT SAT JUN 11 2011/
...HIGH PLAINS THIS AFTERNOON INTO TONIGHT...
A SERIES OF MIDLEVEL SHORTWAVE TROUGHS WILL EJECT NEWD OVER THE HIGH
PLAINS FROM THE MEAN TROUGH OVER THE GREAT BASIN...WITH DOWNSTREAM
LEE CYCLOGENESIS ALREADY UNDERWAY ACROSS ERN WY/CO. EMBEDDED SPEED
MAXIMA ARE EXPECTED TO APPROACH THE WY/MT/SD BORDER REGION THIS
AFTERNOON...AS WELL AS SE CO/SW KS. THESE SPEED MAXIMA WILL COMBINE
WITH DAYTIME HEATING AND A POST-FRONTAL UPSLOPE REGIME TO SUPPORT
SCATTERED AFTERNOON THUNDERSTORM DEVELOPMENT ACROSS THE HIGH PLAINS.
THE RICHEST BOUNDARY LAYER MOISTURE IS CONFINED TO THE FRONT ACROSS
OK...WITH MID-UPPER 50S DEWPOINTS EXPECTED THIS AFTERNOON ACROSS SE
CO/SW KS/TX PANHANDLE...AND UPPER 40S TO LOWER 50S FROM NE CO TO THE
NRN HIGH PLAINS. THE COMBINATION OF LOW-LEVEL MOISTURE/SURFACE
HEATING AND UPSTREAM MIDLEVEL LAPSE RATES AOA 8 C/KM WILL RESULT IN
MLCAPE VALUES NEAR 1500 J/KG ACROSS SE CO/SW KS/TX PANHANDLE WHERE
TEMPERATURES WILL WARM WELL INTO THE 80S...AND NEAR 1000 J/KG WITH
COOLER SURFACE TEMPERATURES FROM NE CO NWD INTO THE NRN HIGH PLAINS.
MEANWHILE...EFFECTIVE BULK SHEAR AOA 40 KT WILL BE SUFFICIENT FOR
SUPERCELLS...WHILE LOW-LEVEL HODOGRAPH CURVATURE/SRH WILL FAVOR
CYCLONIC STORMS.
THE STEEP LAPSE RATES AND SUPERCELL WIND PROFILES SUGGEST THAT LARGE
HAIL WILL BE THE MAIN SEVERE THREAT LATER THIS AFTERNOON...WHILE THE
RISK FOR DAMAGING WINDS WILL INCREASE SOME THIS EVENING WITH STORM
MERGERS AND COLD POOL GROWTH. THE TORNADO RISK IS LESS CERTAIN
GIVEN RELATIVELY LARGE TEMPERATURE-DEWPOINT SPREADS AOA 30 F IN THE
CORRIDOR OF STRONGEST INSTABILITY ACROSS SE CO/SW KS/TX AND OK
PANHANDLES. STILL...A COUPLE OF TORNADOES WILL BE POSSIBLE GIVEN
THE EXPECTATION OF DISCRETE SUPERCELLS FOR A FEW HOURS AND AN
INCREASE IN LOW-LEVEL SHEAR THIS EVENING. FARTHER N INTO SE MT/NE
WY/WRN SD...A COOLER BOUNDARY LAYER WILL RESULT IN LOWER
TEMPERATURE-DEWPOINT SPREADS AND ACCORDINGLY WEAKER INSTABILITY.
HERE...THERE WILL ALSO BE A RISK FOR A COUPLE OF TORNADOES BEFORE
UPSCALE GROWTH OF INITIALLY DISCRETE STORMS INTO ONE OR MORE
CLUSTERS THIS EVENING.
OVERNIGHT...EXPECT THE CONVECTION TO CONTINUE EWD AS AN MCS ALONG
THE FRONT/INSTABILITY CORRIDOR NEAR THE OK/KS BORDER...SUPPORTED BY
WAA WITH THE LLJ. DAMAGING WINDS AND LARGE HAIL WILL BE THE PRIMARY
SEVERE THREATS.
...PA/MD/VA THIS AFTERNOON...
A REMNANT COLD POOL AND MCV ASSOCIATED WITH OVERNIGHT CONVECTION
WILL CONTINUE GENERALLY EWD TOWARD CENTRAL PA/NRN VA THIS AFTERNOON.
STRONG SURFACE HEATING IN ADVANCE OF THE COLD POOL WILL RESULT IN
MODERATE INSTABILITY THIS AFTERNOON /MLCAPE VALUES APPROACHING 1500
J PER KG/...AND WEAKENING CONVECTIVE INHIBITION. DEEP-LAYER
VERTICAL SHEAR WILL REMAIN RATHER WEAK...WITH ONLY SOME MODEST
ENHANCEMENT OF LOW-LEVEL SHEAR ALONG THE WARM FRONT INTO ERN PA.
THUS...EXPECT A FEW DAMAGING GUSTS AND MARGINALLY SEVERE HAIL TO BE
THE PRIMARY SEVERE THREATS THIS AFTERNOON.
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