Tuesday, May 1, 2012

SPC Widens Threat Across Great Lakes for Tomorrow, May 2nd

The Storm Prediction Center has widened the area expected to receive severe thunderstorms from the Plains to the Mid Atlantic. This move essentially covers the entire Great Lakes region, with the exception of New York.

The area being watched for this situation includes the areas of northeast Nebraska, northwest Iowa, extreme southeast South Dakota, as well as southern Minnesota. Those are the areas most at risk, as of now. The latest 12z SPC NAM Parallel model shows an abundance of showers and thunderstorms breaking out across the areas mentioned above. These storms look to be in a cluster, so a tornado threat does not appear incredibly high for now. The proximity to the warm front does have me concerned, however.
Considering that the low pressure area will be in western Nebraska, I am watching for the wind field in that area. It does appear that a counterclockwise wind field is setting up, primarily in Iowa and southern Minnesota, as well as eastern Nebraska. This increased speed and different direction may provide a leg up for tornado threat in comparison to other areas, where the lower level wind field looks to be mainly south to north in accordance with the warm air being pulled towards the areas to the east of the highest risk. Looking over bulk shearing values is indicating to me that there will be a narrow corridor of fairly high shearing rates in the late evening into the overnight hours. I am warning this- small, mesoscale areas are not to be trusted. Yes, they are to be watched, but models are not exactly 'spot-on' when you are looking for a small area's tornado risk.
The main areas I would project the most intense convection to be would definitely include Wisconsin, extreme north Illinois for the overnight hours. I don't need to mention the higher risk areas, as they are already higher risk. Anyhow, judging by 500mb relative humidity values, it is clear that the areas mentioned above will have ample supplies of moist air that may be able to be significantly lifted to the point of severe convection. Should this happen, residents in the mentioned areas should prepare for an intense evening, primarily in Wisconsin.

I'm sorry that there is a lot of writing here, but I'm trying to get as much information out without clogging it up with multiple images.



Anonymous said...

I saw that Maryland is also in the yellow zone. Are they going to be getting any severe weather?

ERN WX said...

Very busy day today. And a VERY busy remainder of the week for most of the CONUS (in terms of severe t-storms). A lot of severe t-storms yesterday & today! All I got was a bit of light rain early this morning. Looks like a very large portion of the CONUS will be threatened by severe storms tomorrow. Andrew, I must say you have done an excellent job covering this. Thursday the threat slides Ewd. It looks like a lot of us may get 2 days of potential severe storms!!! Now I want to talk about my romping grounds. Based heavily on the GEFS, SREF, and NAM. Friday and Saturday offer the potential for severe t-storms across the Mid Atlantic and portions of the NE. Factors... reasonable shear (I would prefer a little higher), CAPE AOA 2000 j/kg, PWATs AOA 1.25 inches, surface dewpoints AOA 60, decent lapse rates, and also warm surface temps. I expect a slgt risk out for Friday & Saturday for most of the Mid Atlantic. And I hope to go storm chasing. I will send everyone any severe reports. So stay safe, enjoy the exciting weather, and have a great week evryone!!!!!!!! Andrew, thanks again for all you do!!!!!!!

ERN WX said...

Hello, Mike. Early this morning my area got the remains of the storms that went through your area last night. All I got was a little light rain. Take care!!!

ERN WX said...

Anonymous, Maryland may see severe storms. Mostly wind and hail.