FULL STEAM AHEAD, WITH A SIDE OF STORMS....

July 20, 2017

It was just a matter of time before all the instability created by the heat and extreme instability exploded in thunderstorms over the Midwest. Hardest hit was the region I've been concerned about for several days (SE Minnesota, southern Wisconsin, NE Iowa, and far northern Illinois). A fast moving bow echo produced widespread damaging winds. A possible tornado hit McGregor, Iowa causing extensive damage there. Here's some pictures from Linda Strong.

Torrential rains were also observed in spots with 1-3" totals through early evening.

 

The set-up for severe weather and heavy rain will exist in parts of my area and the central Midwest again Thursday and Friday. Here's the  precipitable water vapor that's forecast by the GFS. More than 2" both days.

 

Thursday:

Friday:

 

Along with the moisture will be enough heat to provide a significant heat index. Here's what the GFS has for Thursday.

Excessive heat warnings and advisories are out for much of southern Iowa and adjoining portions of surrounding states through Saturday.

The heat and moisture will generate significant instability (CAPE) leading to more chances for storms. Here's the CAPE that's forecast Thursday afternoon.

With all the available energy any storms that develop are likely to be strong and big rain producers into Friday night. The Storm Prediction Center has this for a risk area Thursday.

The GFS has this for additional rainfall through Sunday.

Again, the overall pattern remains intact until the ridge aloft over the central U.S. weakens and retrogrades to the west on Saturday. Full steam ahead! Roll weather...TS

 

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© 2019 Terry Swails