SWODY1
SPC AC 211953
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0253 PM CDT THU OCT 21 2010
VALID 212000Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SOUTHERN HIGH
PLAINS...
...SRN HIGH PLAINS...
IN ADDITION TO THE CONVECTIVE TRENDS INDICATED IN THE SPC MESOSCALE
DISCUSSION #1958...VISIBLE SATELLITE IMAGERY/LIGHTNING DATA SHOWED
CONVECTION DEEPENING OFF THE HIGHER TERRAIN OF SOUTHWEST TX AND NWD
INTO PARTS OF CENTRAL NM. ADDITIONAL CU WAS DEVELOPING OVER ERN NM
TO THE NORTH OF THE SERN NM SURFACE LOW AND ALONG SWRN EXTENT OF
ONGOING TX PANHANDLE MCS.
A COUPLE OF CHANGES HAVE BEEN MADE WITH RESPECT TO THE SEVERE
WEATHER PROBABILITIES AND CATEGORICAL SLIGHT RISK AREAL COVERAGE--
1. THE 15 PERCENT SEVERE WIND AND HAIL PROBABILITIES AND 2 PERCENT
TORNADO THREAT HAVE BEEN EXTENDED INTO SWRN OK TO ACCOUNT FOR THE
ENEWD MOVING MCS THAT APPEARS TO BE EVOLVING INTO A LINEAR MCS. THE
LEAD BAND OF STORMS EXTENDING FROM ARMSTRONG TO FLOYD COUNTIES TX
WAS MOVING ENE AT 30 KT WITH A 46 KT WIND GUST AT KPVW /HALE COUNTY/
AT 1845Z. GIVEN DOWNSTREAM DESTABILIZATION INTO SWRN OK...THE
SLIGHT RISK /MAINLY A WIND THREAT/ HAS BEEN EXPANDED SPATIALLY TO
INCLUDE MORE OF SWRN OK.
2. GIVEN INSTABILITY HAS INCREASED TO VALUES AT OR EXCEEDING 1500
J/KG FROM THE TX SOUTH PLAINS /GENERALLY S OF THE ONGOING MCS/ TO
THE PECOS RIVER AREA AND TX BIG BEND...AND EFFECTIVE BULK SHEAR IS
BECOMING STRONGER ATTENDANT TO STRENGTHENING SWLY MIDLEVEL WINDS...
A SIGNIFICANT HAIL THREAT HAS BEEN ADDED TO THIS OUTLOOK.
..PETERS.. 10/21/2010
.PREV DISCUSSION... /ISSUED 1101 AM CDT THU OCT 21 2010/
...SOUTHERN HIGH PLAINS...
ONGOING MCS ERN NM/TX BORDER REGION BEING SUPPORTED BY AN
INCREASINGLY MOIST/UNSTABLE SELY FLOW OF GULF AIR AND LARGE SCALE
DIVERGENCE IN ADVANCE OF THE SRN AZ UPPER LOW. MODEL WORLD HAS HAD
SOME PROBLEM NOT ONLY FORECASTING BUT INITIALIZING FOR THIS MCS.
GIVEN THE PRESENCE OF STEEP MID LEVEL LAPSE RATES IN PLACE SRN
PANHANDLE INTO SWRN TX AND EXPECTED DAYTIME HEATING IN ADVANCE OF
THE MCS...MLCAPES SHOULD BE ABLE TO CLIMB TO AOA 1500 J/KG PRIOR TO
REACHING CONVECTIVE TEMPS BY MID AFTERNOON. IT NOW APPEARS THAT THE
INITIAL FOCUS FOR SEVERE THUNDERSTORMS INCLUDING POSSIBLE SUPERCELLS
WILL BE ASSOCIATED WITH THE LOW LEVEL CONVERGENCE ACROSS SRN TX
PANHANDLE ON THE OUTFLOW OF THE ONGOING ACTIVITY THEN SWD NEAR DRY
LINE THRU SWRN TX.
ATTM THE FACTOR FOR NOT ADDING SIG HAIL AND A GREATER TORNADO THREAT
IS THE MARGINAL LOW LEVEL SHEAR AND SOMEWHAT LIMITED INSTABILITY.
HOWEVER WITH BRN SHEAR INCREASING TO 50KT WITH APPROACHING JET MAX
NOW ACROSS NRN MEX AND POTENTIAL FOR GREATER INSTABILITY THAN NOW
EXPECTED WILL REEVALUATE THE THREAT AT 20Z.
REDEVELOPMENT OF STRONG/SEVERE THUNDERSTORMS IN WAKE OF MORNING
ACTIVITY IS LIKELY ACROSS ERN NM AS THE UPPER LOW NOW SRN AZ TRACKS
INTO SWRN NM BY THIS EVENING. AGAIN HAIL WILL BE THE PRIMARY THREAT
BUT WITH POTENTIAL FOR SUPERCELLS...LARGE HAIL AND ISOLATED
TORNADOES WILL BE POSSIBLE.
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