Sunday, September 7, 2014

September 9-10 Potentially Strong Severe Weather Event

A multi-day severe weather event looks to unfold this Tuesday and Wednesday.

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The image above, from the Storm Prediction Center, shows the severe weather outlook for Tuesday, September 9th. In this image, we see the states of Kansas, Nebraska, Iowa, Minnesota, Wisconsin, Illinois and Missouri under the Slight Risk demarcation. The outlook from the SPC indicates a strong low pressure will traverse the Midwest and Plains, with a large airmass of warm, humid air battling a swath of cold, dry air from the north.

Instant Weather Maps
Although there won't be too much instability to provoke a huge severe weather event, the strengthening of the low pressure system as it pushes northeast, combined with the high precipitable water values across the Plains and Midwest, should lead to the chance for severe weather. Initially, individual cells should be the primary threat, before congealing into a squall line, potentially with damaging winds.

On Wednesday, the SPC outlooks some of the same areas that were threatened on Tuesday, highlighting Illinois, Wisconsin, Michigan, Indiana, Ohio, Pennsylvania, and New York for potential severe weather. As the low pressure system previously discussed continues to push northeast, it should lead to a more enhanced risk of severe weather, possibly more than on Tuesday.

Instant Weather Maps
The GFS model shows the low pressure system rapidly strengthening by Wednesday afternoon, now displaced into northern Michigan. The minimum pressure has dropped to about 995 millibars, not atypical of autumnal low pressure systems that drive through the Upper Midwest and Plains with tremendous strength.

The set-up on Wednesday will be considerably different than that on Tuesday. The wind field on Wednesday is expected to be more 'charged', due to the rapid cyclogenesis occurring with that low pressure system in northern Michigan. Consequentially, the SPC is indicating a severe wind threat may evolve over the highlighted regions, as a squall line may form and bring potentially widespread damaging winds to the Midwest and Great Lakes.

Additional updates on this event will be posted in the near future.