SWODY3
SPC AC 170643
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0143 AM CDT MON SEP 17 2007
VALID 191200Z - 201200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
INTENSE UPPER TROUGH CENTERED OVER THE PACIFIC NW IS FORECAST TO
BECOME INCREASINGLY CUT OFF FROM THE POLAR BRANCH OF WESTERLIES AS
IT DIGS SWD INTO NV/CA. NUMERICAL GUIDANCE IS CONSISTENT IN
INDICATING THAT A SHORT WAVE TROUGH WILL EJECT NEWD FROM THIS
EVOLVING UPPER LOW INTO THE NRN PLAINS WEDNESDAY NIGHT. IN THE LOW
LEVELS...FRONTAL ZONE FROM THE GREAT LAKES SWWD INTO THE SRN HIGH
PLAINS WILL WEAKEN THROUGH THE PERIOD OWING TO CYCLOGENESIS OVER THE
NRN HIGH PLAINS. WRN PORTION OF THIS BOUNDARY IS EXPECTED TO REFORM
OVER THE NRN PLAINS AS A WARM FRONT DURING THE LATTER HALF OF THE
PERIOD.
..MT/WY EWD INTO THE DAKOTAS...
STRENGTHENING SLY/SELY LLJ OVER THE HIGH PLAINS WILL ENHANCE THE NWD
TRANSPORT OF AN INCREASINGLY MOIST BOUNDARY LAYER BENEATH A PLUME OF
STEEP MID-LEVEL LAPSE RATES PRESENT OVER THE REGION. THESE
DIFFERENTIAL ADVECTIONS WILL RESULT IN RELATIVELY FAST AIR MASS
DESTABILIZATION OVER PORTIONS OF WY AND CNTRL/ERN MT EWD INTO THE
DAKOTAS. FORECAST SOUNDINGS SUGGEST THAT CAPPING MAY INHIBIT THE
DEVELOPMENT OF ANY DIURNAL TSTM DEVELOPMENT WEDNESDAY AFTERNOON AND
EVENING INVOF DEEPENING SURFACE LOW AND WARM FRONT.
TSTM /MAINLY ELEVATED/ APPEAR MORE LIKELY WEDNESDAY NIGHT INTO
THURSDAY MORNING MAINLY OVER ND...TO THE N OF SURFACE WARM FRONT
WHERE WAA/ISENTROPIC ASCENT WILL BE MAXIMIZED ALONG NOSE OF
EWD-MIGRATING LLJ. THE COMBINATION OF MODEST INSTABILITY AND
VERTICAL SHEAR THROUGH THE CLOUD BEARING LAYER SUGGEST A THREAT OF
SOME HAIL WITH THE MORE INTENSE STORMS.
.MEAD.. 09/17/2007
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