SWODY1
SPC AC 271934
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0134 PM CST THU NOV 27 2008
VALID 272000Z - 281200Z
...NO SVR TSTM AREAS FORECAST...
...SOUTHWEST DESERTS...
AN UPPER-LEVEL LOW IS EVIDENT ON WATER VAPOR IMAGERY CENTERED OVER
THE LOWER CO RIVER VALLEY. SOUTH AND EAST OF THE LOW...A DRY SLOT IS
LOCATED FROM THE NRN SECTION OF BAJA CA ENEWD ACROSS NW MEXICO INTO
SE AZ. A SHORTWAVE TROUGH...ANALYZED WELL BY THE MODELS...EXISTS
NEAR THE LEADING EDGE OF THE DRY SLOT. THIS FEATURE IS LIKELY
ENHANCING LARGE-SCALE ASCENT OVER SRN AZ WHERE SCATTERED
THUNDERSTORM ACTIVITY IS ONGOING. AS SFC TEMPS CONTINUE TO
WARM...THUNDERSTORM COVERAGE SHOULD GRADUALLY EXPAND. THUNDERSTORM
DEVELOPMENT WILL ALSO BE POSSIBLE FURTHER NORTHWEST CLOSE TO THE
UPPER-LEVEL LOW CENTER AND EAST ACROSS THE SRN ROCKIES WHERE
LARGE-SCALE ASCENT WILL BE PLENTIFUL THIS AFTERNOON AND EVENING.
CONCERNING THE SEVERE THREAT...OBJECTIVE GUIDANCE SUGGESTS STEEP
MID-LEVEL LAPSE RATES ARE PRESENT AROUND THE UPPER-LEVEL LOW WHERE
500 MB TEMPS GENERALLY RANGE FROM -18C TO -22C. THIS COMBINED WITH
INCREASING INSTABILITY THIS AFTERNOON MAY BE SUFFICIENT FOR HAIL
WITH THE STRONGER UPDRAFTS. ALTHOUGH A MARGINAL SEVERE THREAT COULD
EXIST OVER A WIDESPREAD AREA ACROSS SRN AND CNTRL AZ...THE GREATEST
THREAT FOR SMALL HAIL WOULD APPEAR TO BE SOUTHEAST OF PHOENIX WHERE
THE COMBINATION OF VERTICAL SHEAR AND INSTABILITY SHOULD BE
MAXIMIZED LATE THIS AFTERNOON.
..BROYLES.. 11/27/2008
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