We are sure you’ve heard about it by now, showers and thunderstorms are likely to impact the Halloween forecast. Here’s an early breakdown of that day and what we could expect. As the week goes on, we’ll have even more finite times for our strongest showers and thunderstorms but this will still give you a good idea of what could happen on Thursday.
We’ll start Thursday morning on the dry side with breezy winds and mostly cloudy skies. Temperatures will also be warm to start the day. Lows should be in the upper 50s that morning. But the closer we get to the noon hour, the better chance for showers and thunderstorm across the state.
I’ve grabbed a few weather model images to help paint the picture here. The model you’re looking at to the left is the European model and it’s been pretty consistent on timing with this storm. The time shown is 18Z, which locally is 2 PM EDT. The strongest storms would be out in Illinois and further south in Kentucky. But this will bring a good chance for rain for the majority of the state in the early afternoon hours. Also in this time, it would be very windy as the storms start to move in. Winds at 15 to 25 mph and gusting even higher than that will be possible.
Let’s fast forward to later Thursday evening. The next model picture you are looking at is the European again but this time it’s at 8 PM (0Z for my weather nerds!). As you can see, the state is still in the bulls-eye of widespread rain and this would probably produce our stronger storms and heavier rainfall amounts too. Unfortunately this means that rain looks likely for trick or treat hours regardless if you start as early as 5 PM or wait as late as 10 PM. It will also be very windy still at this time. As with any thunderstorm, lightning is also a threat to anyone outside. We obviously can’t keep the masses away from trick or treating but you need to be smart about this on Thursday. Meteorologist Brian Wilkes will be following these storms throughout Thursday evening and he’ll have the latest on where we are picking up lightning and the heaviest rain.
So here is my honest opinion as it stands today on Thursday. Rain is likely that evening and temperatures will be in the mid to low 60s during trick or treat hours. This time frame will also be very windy, so hold on tight to any hats that go along with your costume!
SEVERE WEATHER CHANCE:
Here are a few more things that our weather team continues to monitor with this system. Our weather models are already picking up that this is going to be a heavy rain system. The model average is already coming in over 1″ of precipitation on Thursday. But the intensity and duration of these storms could result in higher amounts than just 1″ of rain. Here’s a look at the Canadian weather model. It places anywhere from 1 to 2.5″ of rain in Central Indiana by 2 AM Friday.
Finally, let’s talk about the chance for severe weather. As of right now, the Storm Prediction Center only includes the extreme southwestern part of the state in their severe weather discussion. But that doesn’t mean we shouldn’t be looking at it throughout the entire area. Even our local National Weather Service office in Indianapolis says in the morning discussion that “a strong cold front is poised to cross the region late Thursday evening bringing the potential for heavy rainfall and possibly the threat for severe weather.” Here are the main threats we are looking at with this system:
1. Heavy rain – This is more or less likely with this system. Deep moisture starts building as early as Tuesday night.
2. Damaging winds from a squall line or QLCS – We should see some instability ahead of the line of storms and this coupled with our strong wind at the surface, helicity and shear, it could be enough to produce stronger storms or even severe storms.
Helicity: The turning of winds with height and increase in wind speed in that same height as well. When this value increases, you go from the potential for supercells or even tornadoes. But it takes multiple elements to make either of those thing happen.
Shear: This is what is necessary to sustain and tilt and updraft of a thunderstorm.