SWODY1
SPC AC 280551
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1251 AM CDT TUE AUG 28 2007
VALID 281200Z - 291200Z
..THERE IS A SLGT RISK OF SVR TSTMS FROM THE CNTRL PLAINS TO THE
UPR GRTLKS...
..SYNOPSIS...
FAST POLAR WLYS WILL REMAIN ALONG THE US-CANADIAN BORDER TUE WITH
THE SPEED MAX OVER THE NRN ROCKIES TRANSLATING TOWARD THE UPR GRTLKS
REGION BY TUE NIGHT. MEANWHILE...A SEPARATE STREAM WILL ARC ALONG
THE NRN PERIPHERY OF THE SUBTROPICAL RIDGE. WITHIN THIS
JET...NUMEROUS LOW-AMPLITUDE IMPULSES WILL EJECT ENEWD AHEAD OF THE
PRIMARY POLAR TROUGH. ONE SUCH SUBTROPICAL DISTURBANCE...NOW OVER
WRN CO...WILL SHEAR ENEWD...ARRIVING ON THE CNTRL PLAINS BY TUE AFTN
AND THE CORN BELT TUE NIGHT.
AT THE SFC...COMPLEX ARRAY OF OUTFLOW BOUNDARIES AND SEGMENTED
PRE-FRONTAL TROUGHS WILL PRECEDE A COLD FRONT FROM UPR MI SWWD
ACROSS WI...IA...NEB AND INTO THE CNTRL HIGH PLAINS TUE AFTN/EVE.
THE PRIMARY COLD FRONT WILL BEGIN TO OVERTAKE THESE FEATURES LATE IN
THE DAY...MOVING TO A POSITION FROM NRN LWR MI SWWD INTO CNTRL IA
AND NRN KS BY 12Z WED. A WEAK SFC LOW OVER THE UPR MS VLY WILL
TRANSLATE NEWD INTO THE UPR GRTLKS REGION...WHILE ANOTHER LOW FORMS
OVER PARTS OF WRN KS AHEAD OF THE APPROACHING CNTRL ROCKIES IMPULSE.
..CNTRL PLAINS TO THE GRTLKS REGION...
A RIBBON OF MID/HIGH-LEVEL CONVECTION WILL LIKELY BE MAINTAINED FROM
THE CNTRL ROCKIES ACROSS NEB/SD INTO MN AND NRN WI TODAY. PERIODIC
BANDS OF TSTMS MAY EVOLVE FROM THIS MOISTURE SOURCE THROUGH THE
DAY...PARTICULARLY FROM PARTS OF THE MO VLY NEWD INTO THE UPR GRTLKS
REGION ALONG THE NE PERIPHERY OF A STRONG CAPPING INVERSION. SOME OF
THIS ACTIVITY MAY PRODUCE LARGE HAIL AND GUSTY WINDS.
WARM SECTOR S OF THIS ACTIVITY WILL ONCE AGAIN BECOME VERY WARM AND
UNSTABLE DURING THE AFTN/EVE FROM UPR MI SWWD INTO THE CNTRL PLAINS
STATES. SFC DEW POINTS IN THE MID-60S TO LWR 70S BENEATH THE STEEP
LAPSE RATE PLUME ALOFT WILL CONTRIBUTE TO MLCAPES OF 2000-3500 J/KG.
BUT...CINH WILL BE QUITE ROBUST AND TSTM INITIATION WILL LIKELY
REQUIRE STRONG HEATING AND DEVELOPMENT OF DEEPER MASS CONVERGENCE
ALONG/BEHIND THE SEWD MOVING COLD FRONT.
STRONGEST LARGE SCALE ASCENT WILL LIKELY BE ACROSS THE UPR MS VLY
AND UPR GRTLKS REGION AHEAD OF THE NRN STREAM DISTURBANCE.
HERE...ACTIVITY WILL LIKELY STRENGTHEN AND/OR DEVELOP ALONG THE SRN
EDGE OF MORNING STORMS. BULK SHEAR WILL BE STRONGEST ACROSS THE
REGION AND BE FAVORABLE FOR SUPERCELLS AND/OR FAST MOVING TSTM
CLUSTERS CAPABLE OF DMGG WINDS/LARGE HAIL.
FARTHER SW...MORE STORMS ARE EXPECTED TO INITIATE AHEAD OF THE LWR
AMPLITUDE WAVE MOVING EWD FROM THE CNTRL ROCKIES. PARCELS WILL
LIKELY BE FORCED TO THE LFC AS THEY ENCOUNTER THE DEEPENING FRONT
INTERFACE TUE AFTN/EVE FROM NWRN IA SWWD INTO PARTS OF KS. STORMS
WILL BE EMBEDDED IN COMPARATIVELY LESS BULK SHEAR THAN FARTHER
NE...BUT STEEP LAPSE RATES ALOFT WILL BE FAVORABLE FOR LARGE HAIL
PRODUCTION AND PERHAPS STRONG WIND GUSTS.
WHILE ACTIVITY ACROSS THE GRTLKS LARGELY DIMINISHES AND/OR MOVES
INTO ONTARIO TUE NIGHT...SOME SEMBLANCE OF AN MCS OR TWO MAY PERSIST
ACROSS THE CORN BELT AND CNTRL PLAINS OVERNIGHT. ISOLD GUSTY
WINDS/MARGINALLY SVR HAIL MAY CONTINUE TO BE A THREAT WITH THIS
ACTIVITY.
.RACY/GUYER.. 08/28/2007
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