SPC AC 282012
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0312 PM CDT FRI JUL 28 2006
VALID 282000Z - 291200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SRN NEW ENGLAND TO THE
MID ATLANTIC REGION...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS A PART OF THE NRN PLAINS
INTO THE NRN GREAT LAKES...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF AZ...
...MID ATLANTIC INTO SRN NEW ENGLAND...
STRONG FORCING FOR ASCENT AHEAD OF SHORT WAVE TROUGH...NOW LOCATED
FROM SRN QUEBEC TO THE CENTRAL APPALACHIANS...WILL MAINTAIN LINE OF
THUNDERSTORMS EXPECTED TO MOVE EWD ACROSS SRN NEW ENGLAND AND THE
REMAINDER OF THE MID ATLANTIC REGION INTO EARLY-MID EVENING.
MODERATE INSTABILITY EAST OF ONGOING LINE OF STORMS COMBINED WITH
STRONG DEEP LAYER SHEAR WILL CONTINUE TO SUPPORT ORGANIZED SEVERE
STORMS WITH DAMAGING WINDS BEING THE PRIMARY THREAT INTO THE
EVENING.
...NRN PLAINS INTO THE NRN MS VALLEY AND NRN GREAT LAKES...
EARLY AFTERNOON SURFACE ANALYSIS SHOWED A COLD FRONT EXTENDING FROM
NERN MN SWWD TO ALONG THE ND/SD BORDER...WITH A PRE-FRONTAL TROUGH
HAVING MOVED INTO THE WRN U.P. OF MI AND NWRN WI/PARTS OF EAST
CENTRAL MN. COLD FRONT WILL CONTINUE TO MOVE SWD AND SHOULD
OVERTAKE THE PRE-FRONTAL TROUGH BY THIS EVENING. STRONG SURFACE
HEATING ALONG/S OF THESE BOUNDARIES WITHIN VERY MOIST AIR MASS HAS
ALLOWED AIR MASS TO BECOME VERY UNSTABLE ACROSS THE SRN THREE
QUARTERS OF MN WITH AN AXIS OF MODERATE INSTABILITY EXTENDING EWD
ALONG THE PRE-FRONTAL TROUGH. THE COMBINATION OF THE SURFACE
HEATING AND ASCENT WITHIN THE RIGHT ENTRANCE REGION OF A 50 KT NWLY
MID LEVEL JET...NOW LOCATED OVER NRN MN...ARE EXPECTED TO AID IN
FURTHER WEAKENING OF INHIBITION. THUS...THUNDERSTORMS SHOULD
CONTINUE TO DEVELOP WWD ALONG THE PRE-FRONTAL TROUGH...AND ALSO
ALONG THE COLD FRONT AS THIS BOUNDARY MOVES SWD INTO CENTRAL MN/NRN
WI AND THE U.P. OF MI. OBJECTIVE ANALYSES INDICATED EFFECTIVE BULK
SHEAR VALUES HAVE INCREASED SUPPORTING ORGANIZED SEVERE STORMS WITH
A FEW SUPERCELLS POSSIBLE. LARGE HAIL AND DAMAGING WINDS WILL BE
THE PRIMARY THREATS. HOWEVER...GIVEN MOIST BOUNDARY LAYER COMBINED
WITH AN INCREASING SWLY LLJ EXTENDING INTO EAST CENTRAL MN/NRN WI BY
EARLY EVENING...LOW LEVEL SHEAR IS EXPECTED TO INCREASE POTENTIALLY
SUPPORTING AN ISOLATED TORNADO OR TWO. THIS LLJ WILL VEER TO WLY
OVERNIGHT AND SHOULD MAINTAIN A CLUSTER OF STORMS SPREADING EWD
TOWARD NRN LOWER MI/ERN U.P. OF MI. WEAKER INSTABILITY AHEAD OF
THIS OVERNIGHT ACTIVITY SHOULD LIMIT THE ERN EXTENT OF SEVERE
STORMS.
BY LATE EVENING...SEVERE THREAT IS EXPECTED TO SHIFT WNWWD INTO ND/
NRN SD AS WAA INCREASES NORTH OF SURFACE FRONT AND ALONG NOSE OF
STRENGTHENING NRN PLAINS SLY LLJ. THIS LLJ IS EXPECTED TO
STRENGTHEN IN RESPONSE TO A SHORT WAVE TROUGH...NOW LOCATED OVER
NERN MT/SRN SASKATCHEWAN...RIDING THE TOP OF THE RIDGE ACROSS SRN
CANADA/ND TOWARD NRN MN. SUFFICIENT INFLOW OF MODERATE ELEVATED
INSTABILITY AND 50-60 KT OF EFFECTIVE BULK SHEAR SUGGEST LIKELIHOOD
FOR MCS DEVELOPMENT WITH EMBEDDED ELEVATED SUPERCELLS PRODUCING
LARGE HAIL. THE LLJ SHOULD VEER TO SWLY ALLOWING THE MCS TO MOVE
ESEWD INTO PARTS OF NRN/CENTRAL MN BY 12Z SATURDAY. DAMAGING WINDS
MAY BECOME A THREAT IF STORMS CAN ROOT INTO SHALLOWER STABLE LAYER
NEAR THE SURFACE LATER TONIGHT WHICH WILL CONTINUE INTO THE DAY 2
FORECAST PERIOD.
...AZ...
WELL DEFINED MID/UPPER LEVEL CIRCULATION...CURRENTLY CENTERED ALONG
AZ/NM BORDER...WILL CONTINUE TO PROGRESS SLOWLY SWWD THIS FORECAST
PERIOD. ASCENT AHEAD OF THIS FEATURE AND SURFACE HEATING WILL
SUPPORT ADDITIONAL THUNDERSTORM DEVELOPMENT ACROSS THE HIGHER
TERRAIN OF CENTRAL/NWRN AZ INTO SWRN UT/SRN NV. NLY STEERING FLOW
SUGGESTS STORMS ARE EXPECTED TO MOVE/PROPAGATE SWD TOWARD THE LOWER
ELEVATIONS...WITH DAMAGING WINDS POSSIBLE. IN ADDITION... 25-30 KT
OF DEEP LAYER SHEAR COMBINED WITH MODERATE INSTABILITY WILL SUPPORT
A FEW SUPERCELLS PRODUCING LARGE HAIL AND STRONG WIND GUSTS.
..PETERS.. 07/28/2006
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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