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First Chance for Severe Weather this spring (3/17/21)


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 Model data is showing the potential for the first chance of severe weather in Kentucky next Wednesday. For now the timing is from late morning to the evening hours. First the GFS EHI shows the conditions could be favorable for the formation of strong to severe starting in western Kentucky to portions of central Kentucky. Conditions will weaken as the system moves across the state from west to east during the day.


This next map shows the precipitable water that will be present for the storms. You can also see the low pressure system up in Wisconsin and the front that will trail from the low. 



This is the GFS radar showing the system as it progresses across Kentucky. Even though the chance for severe weather decreases as it moves across the state those in central Kentucky around the I-75 corridor  could still expect some heavy rain.



I will update as we get closer.



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On Wednesday a substantially unstable environment encompassing a large area is likely. A moist Gulf airmass will stream northward. Conditions could be favorable for scattered severe storms.  For now, the Storm Prediction Center has a broad 15% risk area. All severe weather hazards will be possible. Portions of Kentucky west of I-65 are included.





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During the day on Wednesday, showers will be ongoing.  By afternoon, a closed-off upper system moves out of the Plains into Missouri heading towards Kentucky. The system is forecast to pass to the north of Kentucky. A warm front will pass through the state and temperatures could rise some Wednesday evening. A trailing cold front will move through after the warm front. The section between the two fronts is where the potential for the strongest storms to form. 

The jet stream will be moving out of the southwest at 65 to 75 mph. At the surface, the winds will be out of the southeast. This will cause some twisting in the atmosphere which is need for the formations of tornadoes. How much of a threat we will see remains to be seen.

Jet Stream


Surface winds


Wednesday evening the temps could rise into the low 60s around 8 pm EDT. For now this is mainly from around I-65 westward. This will come into more focus as we get closer to Wednesday. 



Dew points could reach the low 60°s in southcentral Kentucky. This is where I'm watching for the best chance for the formation of tornadoes. Word of caution, the exact area is unknown at this time. It is also not a given that tornadoes will form.



The time period I'm looking at is between 8-11 pm EDT Wednesday. Check back for updates as we get closer. 



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Just wanted to touch base with everyone. My thinking is that most if not all of the possible severe weather will Wednesday evening, will be west of I-65. I've been doing a lot of studying on the ingredients for severe weather. 
First, let's look at the CIN or convection inhibition. This is what is called the capping of the atmosphere. A layer of warm air aloft could inhibit the rising of air that thunderstorms need. The period I'm watching is 5 pm EDT Wednesday to 2 am EDT Thursday. Also, I'm going to use just the NAM for this update.

Starting around 5 pm EDT the air will be mildly unstable. The potential instability will increase as the evening goes on. This will allow the thunderstorms to grow. Values under 100 mean potential instability. The values shown on the map are from around -0 to around -150.



Next lets look at the CAPE. This is the convective available potential energy. This is the amount of fuel available to a developing thunderstorm. Also it describes the instability of the atmosphere. It is showing values around 372-1280 which mean the atmosphere will be moderately unstable. 


Now lets look at the 500mb Vorticity map. This shows us the spin in atmosphere. You can see there will be the spinning with height that could potentially form tornadoes.



The simulated radar shows the precipitation for the same time.



So the potential is there for strong to severe storms. As of today, the Storm Prediction Center has a category 1 Marginal Risk Area from basically I-65 back westward to the Land between the Lakes area. A category 2 Slight Risk area west of the Marginal Risk Area



I will post an update tomorrow. For now it looks like this will be an late evening into the night time hours event. 



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This will be very quick. It appears this morning that we could be facing a multi-day event. The SPC has issued a cat 3 Enhanced Risk Area for extreme southwest Kentucky. A category 2 Slight Risk Area now covers most of western Kentucky. A cat 1 Marginal Risk Area extends eastward to around I-65. This is for Wednesday evening.

We now  could possibly see another round of strong to severe storms on Thursday. A category 1 Marginal Risk Area has been issued for portions of Kentucky from just west of Madisonville to around I-65. A category 2 Slight Risk Area covers the rest of Kentucky east of I-65.


I will update later today.

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After an initial round of showers and thunderstorms Wednesday afternoon a second line of storms will  move into western Kentucky over night. This appears to be the one to bring the severe weather to that portion of the state. For now all aspects of severe weather will be possible. If this trend continues I will issue a severe weather alert day in the morning.

I'm using the NAM 3km for this update because there is only 1 hour between each frame. It will give us a clear indication of when  the possible severe weather will move into western Kentucky. The time period is from 3 pm EDT Wednesday to 1 am EDT Thursday morning.





Update will be in the morning.

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