Forecast: Watching the pot for storms

Posted at 3:05 PM on June 17, 2009 by Paul Huttner

SPC convective outlook expands today's slight risk for severe storms eastward to include the Twin Cities metro area.

A complex and potentially severe weather scenario is unfolding for the next 48 hours in the Upper Midwest.

A series of upper air impulses will move through between now and Friday. Each one will bring a chance of thunderstorms to the region. The timing of each wave will determine rain chances. But other complex factors will determine how many showers and storms are produced, and if they are severe.

Here are some of the forecast questions over the next 48 hours:

-When will the individual waves move through?
-How strong will each one be?
-Will cloud cover limit surface heating?
-Will thunderstorm complexes to the south rob moisture from potential storms in Minnesota?
-Will a large mesoscale convective system (MCS) form Thursday and produce a "bow echo" like damaging wind event for southern Minnesota?
-Will we see storms with heavy rainfall that have the capability to produce multi-inch flash flood events?

All of these scenarios are possible. This is why severe storms forecasting is just as much art as science. It's also why "nowcasting" or the business of short term forecasts and updates over the next few hours become more important.

The bottom line is to expect the possibility of storms over the next 48 hours, and to keep a heads up for the latest potential watches and warnings.

PH

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