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Some T-Storms Are In The Forecast This Week ... Evaluating The Severe Threat

Record breaking heat will introduce Spring tomorrow, then the temperatures will gradually get a bit cooler as we move toward the weekend. There is a storm moving through on Friday / Saturday that will bring the cold front through and I want to mention if it has any severe weather chances.


Evaluating Any Severe Weather Threat Friday


We do have a low pressure system approaching on Friday. The system does have some wind energy, so I feel it is worth chatting about. Let's start by looking at the severe weather ingredients.


Severe Ingredients



The forcing mechanism from this storm is a low pressure that will be moving across our area on Friday. This low is not that strong, but it is definitely considered forcing.


GFS Mid Level Disturbance Friday

Notice the mid level low moving toward us on Friday. This is a "closed" low meaning it has cut itself off from the jetstream. These lows are not traditionally associated with large severe weather risks in our area.





Wind Shear

The mid level flow on this system is sufficient to support organized severe weather. Remember we need to see mid level flow of about 35 knots / 40 mph or greater to support an organized severe weather threat.


GFS Mid Level Flow Friday

Notice the mid level flow is actually pretty good on Friday. The mid level winds are about 75 - 90 mph on Friday and you can see the mid level jet diving right across our area..


As good as the winds are in the mid levels on Friday, the lower part of the atmosphere doesn't have great wind energy at all.


GFS Winds 1 Mile Above The Ground Friday

Notice the winds in the critical lower part of the atmosphere are not strong at all. We see only 25 mph winds in this part of the atmosphere on Friday. On strong events, these winds can be 80 mph at this height.

Gfs_850_winds 1


The instability is really the question on Friday which is a bit odd considering how warm we have been. The problem with a closed low pressure system is that they normally don't have much cold air in the mid levels of the atmosphere. Since instability is a combination of warmth at the surface and relatively colder air aloft, we have very warm days that can have lower instability values. The GFS is pointing toward one of these days on Friday.


GFS Instability Friday

Notice the GFS is only showing 500 units of instability despite showing a high of 77. It is conceivable that we could go to as high as around 81, but that still would only result in instability values of near 1000 units.

Gfs CAPE 1



Let's put this all together.



My Thoughts On Severe Weather Friday


There is some forcing on Friday for storms and to be honest it is sufficient to produce some strong to severe storms. The mid level wind energy is actually pretty strong, but in the critical lower levels of the atmosphere it is not nearly as strong. This normally precludes any severe weather event even if the other parameters are good. The instability is just not going to be very supportive on Friday. In my opinion, I think the setup does not support a severe weather event, but it is possible a slight risk could be placed in our area on Friday. The primary threats would be hail and damaging winds, but as stated it doesn't look like an event.


Timing will be important as we evaluate if a slight risk will be necessary. Right now, the GFS does show storms at 1 pm moving through our area which is a time that would probably limit our severe weather potential.





With a setup like this, it really is important for us to get sun early to warm things up a lot and at this point it is just not possible to time that out accurately enough. We will be watching.



Remember my facebook is a great place for weather info anywhere / anytime. It is your source for 24/7 weather information... at home, on your smart phone, or even if the power ever goes out during storms.


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