Massive, historic storm tearing through Midwest

By Jason Samenow

* Warm before storm: Full Forecast | Later: Storm to impact D.C.? *

* Upper Midwest radar | Ohio/Tennessee Valley radar | National radar *



Surface weather map showing historically deep low pressure over Minnesota. Circular brown contours are lines of equal pressure (isobars). These tightly packed lines indicate a strong pressure gradient and hence powerful winds. Source: NOAA

What may become one of the strongest fall storms on record, will rapidly intensify as it cuts through Minnesota today, landing at the Canadian border Wednesday morning.

This high impact, severe storm is already producing widespread damaging winds in the upper Midwest and Great Lakes. High wind warnings are in effect across parts or all of at least 10 states where sustained winds of 30-50 mph are likely, with gusts to over 60 mph possible. Significant airport delays and cancellations are likely in Minneapolis, Milwaukee, Chicago, Indianapolis, Detroit (especially later today) and smaller surrounding airports. Already more than 125 flights have been canceled at Chicago's O'Hare.

In addition to the vast, intense wind field associated with the storm, severe thunderstorms -- with the potential for damaging winds over 70 mph and significant tornadoes - are developing out ahead of the storm from western Indiana into the Ohio Valley.



Risk for severe thunderstorms today (Tuesday, October 26, 2010). Source: Storm Prediction Center

Several tornadoes and wind damage reports have already come in today from eastern Illinois resulting from a squall line that passed through the region early this morning. In addition, a tornado touched down near Milwaukee causing damage to buildings but no injuries according to the Weather Channel.

Numerous tornado and severe thunderstorm warnings are active for this same squall line now cutting across Indiana and Ohio. The Storm Prediction Center has placed much of the central and western Ohio Valley in a moderate-to-high risk zone for severe thunderstorms late this morning through the afternoon. Tornado watches extend from Michigan to Mississippi.

The storm's barometric pressure is equivalent to a Category 2 or 3 hurricane, likely to plunge all the way down to 28.34 inches or 960 mb by tomorrow morning. Meteorologist Paul Douglas from the Star Tribune in Minneapolis indicates the storm's central pressure may drop to the lowest on record for the state of Minnesota. [Update, 11:54 a.m.: The Weather Channel reports a new state low pressure record of 962.1 mb was set in Minnesota this morning]. Even well to the east of the storm center, meteorologist Tom Skilling from WGN in Chicago suggests the Windy City could set a record for its lowest pressure reading observed in the month of October, dipping to around 29.05".

On the back side of the storm in northern Great Plains, colder air is pouring southward, changing the rain to snow. Blizzard warnings are in effect for much of North Dakota, where fierce winds combined with 4" or more of wet snow stir up the possibility of near whiteout conditions.

Although this fall storm will likely go down in the record books as one of the worst of its kind, the Midwest and Great Lakes have experienced ones like it in the recent and distant past. On November 11, 1998 a storm with similar characteristics moved through Minnesota, packing wind gusts over 60 mph in multiple locations in the Upper Midwest and Great Lakes while setting low pressure records. (I personally recall recording a wind-gust of 70 mph with a hand-held anemometer atop the Atmospheric Sciences building at the University of Wisconsin-Madison).

Thirty three years before practically to the date (November 8, 1975), an intense storm moving through the Upper Midwest caused the sinking of the Edmund Fitzgerald shipping vessel on Lake Superior, killing 29 crew members.