Saturday, September 20, 2014
Inquirer Daily News

Bolaris: Get ready for heavy rains, flooding

Flooding from Irene in 2011; some stream flooding in the Philadelphia region is likely the next few days. (Alejandro A. Alvarez/Staff)
Flooding from Irene in 2011; some stream flooding in the Philadelphia region is likely the next few days. (Alejandro A. Alvarez/Staff)

A massive sprawling storm system centered over the Ohio Valley is producing a violent mix of surging warm temperatures, crashing into unseasonably chilly air.

The result is the first deadly outbreak of tornadoes that has hit Arkansas, Mississippi, Oklahoma, and Alabama. An EF3 tornado dropped down about 10 miles west of Little Rock, Ark., with winds in excess of 136 mph, and ran a path of 80 miles, tossing trucks, cars, splintering homes and killing at least 17 people who were not able to escape the tornadoes' brutal force. It's been a late start to the tornado season due to the unseasonably cool spring, but that is starting to change as the Gulf of Mexico is now open for business. The unstable warm, moist air a key ingredient for severe storm development is now in progress.

What does this storm mean for us?

It's going to bring intense rain amounts of 3-5 inches generally along and west of the I-95 corridor. The massive circulation and structure of this storm will transport very warm and moist air directly from the Gulf of Mexico surging northward to create a band of intense rain.

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  • The first surge will take place by early Wednesday morning and then continue throughout the day with 1-3 inches of rain by 5 p.m. Wednesday. The thunderstorm and/or severe storm threat will be at minimal risk during the day, but then increase to a moderate level threat for Wednesday night.

    Flood watches that are now in effect for the entire region will most likely be upgraded to flash flood warnings by Wednesday night into Thursday morning.

    The second surge of the true warm, moist and unstable air will arrive Wednesday night, this will allow for a significant chance of thunderstorm activity and some severe cells are possible. An additional 2-3 inches of rain is possible, especially in any convective activity.

    You will feel that second surge as temperatures will actually hold steady or rise Wednesday night into the 70s by Thursday. Showers and scattered storms can still linger into Thursday as well.

    Stream, creek, and possibly river flooding is something you need to monitor closely for neighborhoods prone to flooding and the best chance of this occurring would be Wednesday night into Thursday.

    Coastal residents will experience tidal flooding due to the strong onshore winds and high astronomical phase. Right now. I'm anticipating minor coastal flooding - starting today.

    By Friday we will start to dry out with a return to a decent amount of sun and temps in the 60s.

    Saturday could see a return to scattered showers, although the second half of your weekend is looking good with dry conditions and temperatures near 70

    Be safe.

    John Bolaris

    John Bolaris For Philly.com
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