Tuesday, May 10, 2011

Severe weather threat for Tuesday

Tuesday is looking to be an active day for the southern half of Minnesota later on the day Tuesday.  Still expecting an outbreak of severe weather, a 2 and 10 chance for any location south of Interstate 94 where the CAPE values will be the highest.  There will be plenty of “juice” for storms to work with.  The gasoline will be in place with plenty of instability as a result of temperatures  now there needs to be the spark.  Not expecting a widespread outbreak as there will be pockets of instability where there is a weak cap.

CAPE values at the surface approaching 5000 J/kg south of Interstate 94 illustrated below at 7 PM Tuesday.  There is where the storms will initiate if able to over the cap.  The cap (warm air at all layers of the atmosphere preventing cloud growth) will be the contingency with the severe weather setup on Tuesday.  It will be all or nothing as temperatures approach 80 degrees.  I expect us to be in the sun much of the day before storms roll in during the evening/overnight hours.  Any time after 4 PM is when storms may fire.


The GFS and NAM forecast models below at 7 PM are in agreement that western Minnesota, from Worthington northwards to Fergus Falls, will have the weakest cap (red and white shading – values closer to zero indicates a weaker cap) near the intersection of a warm and cold front on the Minnesota/Dakotas border.  Based on this observation, there will be a greater likelihood of severe weather over the western half of Minnesota with the Twin Cities seeing storms towards midnight.



You’ll want to stay tuned to this blog and local media for possible watches and warnings throughout the day on Tuesday, especially if you have outdoor interests.  With this unfamiliar warm stretch of weather this spring, many people will be out enjoying themselves not realizing the possibilities of strong to severe thunderstorms with all this heat and humidity.  Like a local television weatherperson around here says, you’ll want to stay sky aware!


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