SWODY1
SPC AC 011948
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0248 PM CDT TUE SEP 01 2009
VALID 012000Z - 021200Z
...NO SVR TSTM AREAS FORECAST...
...NRN/CNTRL HIGH PLAINS...
LATEST SATELLITE IMAGERY CLEARLY DEPICTS CENTER OF UPPER VORT/LOW
OVER SERN MT...ROUGHLY 45E OF BIL...MOVING SLOWLY ESEWD. CU FIELD
IS BEGINNING TO EXPAND/DEEPEN ALONG LEADING EDGE OF THIS COMPACT
SYSTEM FROM NEAR MLS...TO WEST OF GCC. THUNDERSTORMS WILL GRADUALLY
INCREASE ACROSS THE NRN HIGH PLAINS AHEAD OF THIS
FEATURE...ESPECIALLY FROM THE NRN BLACK HILLS REGION INTO SERN MT
WHERE LAPSE RATES HAVE NOW STEEPENED TO NEAR DRY ADIABATIC IN THE
LOWEST FEW KM. HAIL OR PERHAPS GUSTY WINDS MAY ACCOMPANY THE
STRONGER STORMS...IN LINE WITH EARLIER THINKING.
...ELSEWHERE...
SCATTERED THUNDERSTORMS ARE DEVELOPING AS EXPECTED ACROSS MUCH OF
THE HIGHER TERRAIN FROM AZ...NEWD ACROSS THE 4-CORNERS REGION INTO
SWRN CO. WEAK MCV IS EVIDENT IN SATELLITE IMAGERY JUST EAST OF EED.
THIS FEATURE MAY ENHANCE CONVECTION ACROSS THE HIGHER TERRAIN BUT
INSTABILITY IS QUITE WEAK AND DO NOT EXPECT ACTIVITY NORTH OF THE
DESERT VALLEYS TO PRODUCE MORE THAN SMALL HAIL OR GUSTY WINDS.
..DARROW.. 09/01/2009
.PREV DISCUSSION... /ISSUED 1101 AM CDT TUE SEP 01 2009/
MUCH OF CONUS UNDER LATE SUMMER RATHER SLUGGISH FLOW PATTERN AS
PRIMARY WESTERLIES REMAIN ACROSS CANADA. COMPACT UPPER LOW CENTRAL
MT CONTINUES SLOWLY E/SE AROUND UPPER HIGH CENTERED VICINITY
4-CORNERS. A LITTLE STRONGER WESTERLIES S OF MT LOW CIRCULATION IS
PROVIDING SUFFICIENT SHEAR ALONG WITH THE PRESENCE OF AN ELEVATED
MIX LAYER TO SUPPORT A FEW STRONGER STORMS LATER THIS AFTERNOON.
...HI PLAINS...
JUST AHEAD OF THE MT UPPER LOW AND SWD VICINITY THE WEAK N/S SURFACE
TROUGH INTO CENTRAL HI PLAINS...SCATTERED STRONG THUNDERSTORMS WILL
BE POSSIBLE BY MAX HEATING. SUFFICIENT LOW/MID LEVEL MOISTURE
ALONG/E OF SURFACE CONVERGENCE ZONE TO DEVELOP MLCAPES TO 1000 J/KG.
WITH THE PRESENCE OF STEEP MID LEVEL LAPSE RATES AND 30 KT DEEP
LAYER SHEAR...A FEW STORMS CAPABLE OF HAIL AND ISOLATED DAMAGING
DOWNBURSTS WILL BE POSSIBLE ONCE SURFACE BASED INITIATION OCCURS
LATER THIS AFTERNOON. STORMS WILL THEN MOVE SLOWLY EWD INTO HIGH
PLAINS PRIOR TO WEAKENING THIS EVENING WITH LOSS OF HEATING.
...SRN AZ...
MONSOON MOISTURE CONTINUES TO SLOWLY INCREASE NWD ACROSS SRN AND WRN
AZ. WHILE DEEP LAYER SHEAR/STEERING FLOW REMAINS GENERALLY
WEAK...STEEP LAPSE RATES COUPLED WITH HIGH LCL/S SHOULD AGAIN
SUPPORT LOCALLY DAMAGING DOWNBURSTS INTO THE DESERT VALLEYS LATE
THIS AFTERNOON AND EVENING. SEVERE THREAT WILL REMAIN MARGINAL
BASED ON NOT ONLY THE RELATIVELY WEAK SHEAR PROFILES...BUT ALSO
LIMITED CAPE WITH THE STILL LACK OF LOW LEVEL MOISTURE/INSTABILITY.
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