SWODY1
SPC AC 270557
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1257 AM CDT MON AUG 27 2007
VALID 271200Z - 281200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE UPR MS
VLY AND PLAINS STATES...
..SYNOPSIS...
A BROAD UPR RIDGE ACROSS THE CNTRL/SRN PARTS OF THE COUNTRY WILL
KEEP PRIMARY BELT OF WLYS ACROSS THE PAC NW AND SCNTRL CANADA...
ALONG SRN PERIPHERY OF A HUDSON BAY GYRE. LEAD IMPULSE WITHIN THIS
FLOW...NOW CROSSING NRN MN AND NWRN ONTARIO WILL SHIFT QUICKLY INTO
SERN CANADA MONDAY. NEXT MIDLEVEL WAVE OVER THE PAC NW WILL
TRANSLATE INTO THE NRN PLAINS MONDAY AFTN. MEANWHILE...A SEPARATE
STREAM WILL EXIST AROUND THE NRN PART OF THE HIGH...CARRYING LOW
AMPLITUDE DISTURBANCES NEWD FROM THE GRT BASIN INTO THE CNTRL PLAINS
AND UPR MS VLY THROUGH THE PERIOD.
AT THE SFC...A COLD FRONT...NOW EXTENDING FROM NWRN MN SWWD ACROSS
CNTRL ND...IS FORECAST TO MOVE SLOWLY SEWD INTO NRN MN AND SD DURING
THE AFTN. A LOW ALONG THE FRONT SHOULD MOVE NEWD FROM SD INTO MN BY
MONDAY EVENING WITH THE COLD FRONT ACCELERATING SWD THROUGH THE HIGH
PLAINS MONDAY NIGHT.
..PLAINS AND UPR MS VLY...
SEVERAL CLUSTERS OF TSTMS SHOULD BE ONGOING ACROSS PORTIONS OF THE
UPR MS VLY WWD INTO ND AT THE START OF THE PERIOD. STRONGER
STORMS...TIED TO THE LLJ...WILL WEAKEN WITH TIME DURING THE MORNING
AND SHIFT NEWD WHILE CONVECTION WILL LIKELY CONTINUE DEVELOPING EWD
FROM ND INTO NRN MN THROUGHOUT THE DAY. THIS WILL LIKELY STRENGTHEN
OUTFLOW BOUNDARIES AND/OR THE COLD FRONT ACROSS NRN MN AND ERN ND.
TO THE S AND SE OF THE BOUNDARIES...AIR MASS IS EXPECTED TO BECOME
VERY UNSTABLE AGAIN MONDAY AFTN...OWING BOTH TO RICH BOUNDARY LAYER
MOISTURE AND THE STOUT ELEVATED MIXED LAYER. AIR
MASS...HOWEVER...SHOULD REMAIN STRONGLY CAPPED FOR AT LEAST THE
FIRST HALF OF THE HEATING CYCLE. BUT...PERSISTENT FRONTAL
CIRCULATION...HEATING AND THE APPROACH OF ONE OR MORE UPR IMPULSES
SHOULD YIELD INCREASING SVR THREATS LATE MONDAY AFTN/EVENING. TSTMS
WILL LIKELY FAVOR THE ZONE VCNTY THE OUTFLOW BOUNDARY/FRONT
INTERSECTION OVER CNTRL MN WITH ACTIVITY LIKELY BACKBUILDING SWWD
ALONG THE FRONT DURING THE EVENING.
REGION WILL REMAIN BENEATH 50-60 KTS OF WSWLY FLOW ALOFT... BOOSTING
BULK SHEAR SUFFICIENT FOR SUPERCELLS WITH VERY LARGE HAIL.
TORNADOES WILL BE POSSIBLE...ESPECIALLY WITH DISCRETE STORMS THAT
DEVELOP JUST AHEAD OF THE FRONT AND SOUTH OF THE OUTFLOW BOUNDARY
WHERE LOW-LEVEL FLOW WILL BE POTENTIALLY BACKED AT THE SFC.
ACTIVITY WILL EVENTUALLY DEVELOP/MOVE ENEWD TOWARD THE UPR GRTLKS
REGION MONDAY NIGHT WITH ATTENDANT THREATS FOR HAIL/HIGH WINDS.
FARTHER SW...STG/SVR TSTMS WILL BE POSSIBLE ALONG THE
LEE-TROUGH/FRONT ACROSS PARTS OF CNTRL/NRN NEB LATE MONDAY AFTN/EVE.
HERE...VERTICAL SHEAR WILL BE COMPARATIVELY LESS IN THE WARM SECTOR
THAN FARTHER TO THE N. HOWEVER...BOUNDARY LAYER WILL BE HOTTER AND
DEEPLY MIXED AND WILL AT LEAST SUPPORT DMGG WIND/HAIL THREATS
THROUGH MID-EVENING.
..SCNTRL/SERN STATES...
NUMEROUS TSTMS WILL FORM VCNTY A FRONT SITUATED FROM THE LWR MS VLY
TO THE CAROLINAS MONDAY AFTN. FLOW REGIME WILL REMAIN WEAK...BUT
PULSE MULTICELL CLUSTERS MAY PRODUCE ISOLD DMGG WINDS AND/OR
MARGINALLY SVR HAILSTONES.
..ERN UT AND WRN CO...
IMPULSE OVER THE LA BASIN IS PROGD TO SHEAR ENEWD TOWARD THE CNTRL
ROCKIES MONDAY AFTN. PRECIPITABLE WATER VALUES HAVE RISEN TO NEAR 1
INCH ACROSS THE GREAT BASIN AND WILL SUPPORT A CONTINUED THREAT FOR
NUMEROUS TSTMS THROUGH MONDAY NIGHT AS THIS DISTURBANCE MOVES ACROSS
THE REGION. ENHANCED WSWLY FLOW ALOFT MAY YIELD ISOLD FAST MOVING
TSTM CLUSTERS THAT PRODUCE SVR WIND GUSTS FROM PARTS OF ERN UT INTO
WRN CO.
.RACY/GUYER.. 08/27/2007
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