SWODY3
SPC AC 010734
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0234 AM CDT TUE JUL 01 2008
VALID 031200Z - 041200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE OH VALLEY
INTO THE NERN STATES...
...SYNOPSIS...
LARGE SCALE PATTERN WILL REMAIN DOMINATED BY AN UPPER TROUGH OVER
SERN CANADA. AN UPPER RIDGE WILL PREVAIL OVER THE INTERMOUNTAIN WEST
ALONG WITH A LARGE UPPER TROUGH OFF THE WRN U.S. COAST. A SHORTWAVE
TROUGH IS FORECAST TO MOVE THROUGH THE LOWER GREAT LAKES AND NERN
U.S. ALONG SRN PERIPHERY OF UPPER LOW. THIS WILL PROVIDE IMPETUS FOR
THE ATTENDANT COLD FRONT TO MOVE SEWD THROUGH THE NERN STATES.
HOWEVER...TRAILING PORTION OF THIS BOUNDARY WILL LIKELY STALL OVER
THE SRN PLAINS.
...OH VALLEY THROUGH NERN STATES...
SCATTERED THUNDERSTORMS MAY BE ONGOING IN VICINITY OF FRONT FROM THE
LOWER GREAT LAKES SWWD INTO NRN PARTS OF THE OH VALLEY. MOIST AXIS
WITH DEWPOINTS AROUND 60F WILL ADVECT NEWD INTO WARM SECTOR WHERE
SOME BOUNDARY LAYER WARMING MAY OCCUR AHEAD OF ONGOING
CONVECTION...BUT POOR MID-LEVEL LAPSE RATES MAY LIMIT MLCAPE TO
BELOW 1000 J/KG. FLOW IN THE 700-500 MB LAYER WILL LIKELY STRENGTHEN
TO 40-50 KT OVER THE NERN STATES AS SHORTWAVE TROUGH ADVANCES EWD
AND TIGHTENS GRADIENT. A SWLY 40+ KT LOW LEVEL JET IS ALSO FORECAST
TO SHIFT NEWD THROUGH NE U.S. WARM SECTOR. THIS WILL RESULT IN
FAVORABLE UNIDIRECTIONAL WIND PROFILE FOR ORGANIZED STORMS. THE GFS
HAS A SEPARATE LOW LEVEL JET FARTHER WEST OVER THE OH VALLEY...BUT
THIS APPEARS TO BE A FEEDBACK ISSUE. POTENTIAL WILL EXIST FOR STORMS
TO INTENSIFY AS THEY DEVELOP ESEWD ALONG AND AHEAD OF THE FRONT
DURING THE DAY. STRENGTH OF VERTICAL SHEAR WOULD SUPPORT THREAT FOR
BOWING LINE SEGMENTS AND EMBEDDED SUPERCELLS WITH DAMAGING WIND THE
MAIN THREAT. EXPECTED MARGINAL THERMODYNAMIC ENVIRONMENT COULD SERVE
AS A POTENTIAL LIMITING FACTOR.
...SRN PLAINS THROUGH CNTRL AND SRN HIGH PLAINS AND ROCKY
MOUNTAINS...
COLD FRONT IS FORECAST TO ADVANCE SWD INTO THE SRN PLAINS THIS
PERIOD. AN AXIS OF DEWPOINTS IN THE 60S AND STEEP LAPSE RATES WILL
RESULT IN MODERATE INSTABILITY IN VICINITY OF THE FRONT AS THE
BOUNDARY LAYER WARMS DURING THE DAY. VERTICAL SHEAR PROFILES SHOULD
REMAIN MODEST SINCE THE MOIST AXIS WILL HAVE SHIFTED SOUTH OF THE
STRONGER FLOW ALOFT. THIS MAY LIMIT POTENTIAL FOR ORGANIZED STORMS.
HOWEVER...THE THERMODYNAMIC ENVIRONMENT MAY SUPPORT MULTICELL STORMS
CAPABLE OF PRODUCING ISOLATED HAIL AND DAMAGING WIND.
...CNTRL AND SRN HIGH PLAINS AND ROCKY MOUNTAIN REGIONS...
MODELS SUGGEST HEIGHTS MAY RISE SLIGHTLY IN WAKE OF IMPULSE FORECAST
TO MOVE INTO THE CNTRL PLAINS. HOWEVER...A MOIST ELY UPSLOPE
COMPONENT WILL LIKELY EXIST OVER THE CNTRL PLAINS IN POST FRONTAL
ZONE. STRONG HEATING OVER THE HIGHER TERRAIN SHOULD SUPPORT AT LEAST
WIDELY SCATTERED STORMS DEVELOPING. WITH NWLY FLOW ALOFT STORMS MAY
MOVE SEWD OFF THE HIGHER TERRAIN INTO THE HIGH PLAINS. DESPITE
MODEST WIND SPEEDS...THE SELY LOW LEVEL FLOW BENEATH NWLY FLOW ALOFT
MAY CONTRIBUTE TO VERTICAL SHEAR AT LEAST MARGINALLY SUFFICIENT FOR
ORGANIZED STORMS...THE STRONGER STORMS MAY BECOME CAPABLE OF
PRODUCING ISOLATED DAMAGING WIND AND HAIL.
...PACIFIC NW THROUGH NRN ROCKIES...
UPPER TROUGH OFFSHORE WILL RESULT IN 40KT SLY MID LEVEL FLOW IN THIS
REGION. WIDELY SCATTERED STORMS MAY ONCE AGAIN DEVELOP OVER THE
HIGHER TERRAIN AND SPREAD NWD. INVERTED-V BOUNDARY LAYERS WILL
SUPPORT A THREAT OF ISOLATED DAMAGING WIND.
..DIAL.. 07/01/2008
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