Damaging Wind Threat Sparks Moderate Risk Issued for Today, May 2

Overall Risk

Hail Risk

Tornado Risk

Damaging Wind Risk

A moderate risk of severe weather has been issued for eastern Nebraska, western Iowa today as a slight risk of severe weather spans half of the country.

This moderate risk has been issued on account of an elevated damaging wind threat. It does appear that supercells will evolve into a cluster of storms. It can be expected that these storms will be intense and may have powerful downdrafts (a flow of storm-cooled air from the storm- the opposite of an updraft) that could cause damage.
Because of the proximity to the low pressure center, as well as the frontal boundary, there is a tornado threat for the 30% area today. It is somewhat elevated, so a brief spin-up is possible in areas in the 5% tornado graphic.
Farther out to the east, strong showers and storms will develop and become several clusters that will be roaming the area. No significant severe weather is expected, but some small hail and gusty winds are possible.

Andrew

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.

Andrew

Thursday Severe Threat Similar to Wednesday

Probability of Severe Weather

The Storm Prediction Center has outlined an area of severe weather from the central Plains to Michigan for Thursday in the midst of a frontal boundary closing in on a moist and warm area of high temperatures brought north by the warm front associated with this event. Instability values on the order of up to 3000 j/kg will be present in the Great Lakes for this event, but shearing will be a problem. There is expected to be a weak swath of winds in the lower levels that may help to energize the storms, but with little help from the Lower Level or main jet streams, there are limits to this event.

I'm sorry for the shortness and vagueness of this briefing, but I am rushed on time this morning. I will make it up this afternoon with both Wednesday and Thursday discussions. Both risks are over my area, so I will be sure to get pictures if I can.

Andrew

Discussion Concerning Multi-Day Severe Weather Threat (Tuesday-Wednesday)

This is a discussion concerning the multi-day severe weather potential for Tuesday and Wednesday. Further dates will not be included due to a lack of confidence.

Overview
Zonal flow of the jet stream aloft will carry several disturbances along its track. One of these disturbances will involve the lifting of a warm front north into the northern US, engulfing the Midwest and Plains in the warm sector of hot temperatures and humid air. As this happens, a cold front will eventually become present in the western portion of the Plains states before moving eastward.

Factors
Because this will be a zonal flow jet stream, indicating that the jet stream will be on the Canada/US border, that is where we will find the dynamics of shearing associated with this event. Bulk shearing will take place in Wisconsin, which is a reason for the slight risk included in the entire area of Wisconsin. However, slightly lower temperatures and associated dewpoints will act to level out the severe aspect. Nonetheless, the remains potential for some intense weather in that area.
Farther to the south, in north Illinois and the like, hotter temperatures and higher dewpoints will make for a hot, muggy day. Because dry air requires more heat to rise, expect convection to be fairly quick to get started. This may very well be hampered, however, especially without the aid of the jet stream, which will be displaced to the north. However, temperatures in the 70s-80s may be able to ignite some convection. If this happens, the main threats would include damaging wind and large hail. Tornadoes do not appear to be a concern south of Wisconsin, in north Illinois.

Caveats
As mentioned previously, dry air requires more heat to rise. This normally would push down convection chances in Wisconsin, but the presence of the jet stream will cover that loss.

Summary
In the end, I find it more likely that the Wisconsin/Illinois border and north will get in on some of the strongest convection, while areas like North Illinois and possibly southern Iowa may be slotted out of this event. Time will tell.

Storm Prediction Center Issues Slight Risk for Wednesday; Higher Risk Possible

Probability of Severe Weather

The Storm Prediction Center did issue a slight risk today, which was not a surprise to me. However, in the discussion associated with these images, they did mention the potential of a higher risk upgrade in the future. That said, I think there is potential for some more intense weather than what is being pictured here.

I do not have a lot of time to write this, but I can tell you that I will be following this event closely, as it originally started out in the 4-8 day range- something reserved for eventual moderate risk areas or the like.