Wednesday, October 30, 2013

Halloween Eve forecast update: Tricks... or treats?

Seems there is a holiday or great importance tomorrow... everyone with children want to know if they will be able to trick or treat! This is our 3rd blog in 3 days on the Halloween storm system that seems to be bringing a bag of tricks with it.  I'll try and provide more specific impacts and timing in this edition.  Pictures tell the story well, so I've included several.

Severe Weather Outlook

Since this past weekend, the Storm Prediction Center, who monitors severe weather across the nation, has been warning that this storm was coming and had the potential to bring strong to severe storms to the Mid-South.  As it turns out, it's not only the Mid-South under the gun, but a very large area from the central Gulf Coast to the southern Great Lakes region.  However, the highest probability of severe storms (30%, which is not insignificant) lies over the Mid-South and up into the Ohio Valley.  See graphic below.

Probability of severe weather within 25 miles of a point (such as your house), courtesy NWS/SPC.

The main threat with any strong storms will be straight-line wind of 60 mph or higher. However, the wind speeds over the Mid-South from the lowest couple thousand feet all the way up to the jet stream level will be strong and wind shear will be high. This means that there is also a CHANCE of a few tornadoes.  While not the greatest threat, we can't leave it out of the conversation. Hail does not seem to be a major threat.  The most likely time for severe weather will be in the afternoon, or roughly from 1-5pm, though thunderstorms will be likely throughout the day.

The other point worth mentioning is that it will be windy all day long, even outside of thunderstorms. South winds will peak in the 15-25 mph range with gusts above 30 mph likely.  Any items you do not want to have blown around outside should be secured tonight.

Rainfall Amounts

The amount of moisture in the air is high and is loading up as we head into the day Thursday.  Rainfall amounts could be heavy from individual showers and storms and collectively throughout the day.  We will likely see rain start in the metro overnight tonight, likely after midnight, and continue off and on throughout the day.  Models are hinting at a lull in the mid-late morning hours with rain and maybe a few claps of thunder early in the morning, then rain and storms in the afternoon.  Overall, rainfall amounts will likely be 1-2"+ area-wide with some locations possibly seeing 3-4".  Most steady rain will end by 5-6 pm, though a few showers could linger into the prime trick-or-treat hours, as the cold front will move through between ~7-9pm.  Plan accordingly. While widespread flash flooding is not expected due to a lack of recent rainfall, areas that tend to fill up first will likely do so, including streams and small rivers, drainage ditches, and low-lying areas in the concrete jungle.  Monitor these areas, especially if they are near your trick-or-treat route.

Forecast rainfall amounts from NWS from 7pm tonight to 7pm Thursday. The Mid-South is generally in line for 1.5-2"

The images below show one model's representation of what radar COULD look like at a few specific times tomorrow.  These are not official forecasts, but represent one possibility which looks fairly reasonable to the trained eye.  The images are of the high-resolution NAM model courtesy of  As you can see, if this model is fairly close to accurate, rain will be over the metro by morning rush hour, then some storms and heavy rain would be possible by lunch, and most precipitation would be east of us by 6pm with a few lingering showers hanging back to our west.

Hi-Res NAM model "future radar" at 7am Thursday

Hi-Res NAM model "future radar" at noon Thursday

Hi-Res NAM model at 6pm Thursday

Bottom line: how to prepare

Secondary (fall) severe weather season is real and this event likely marks the beginning of it.  While severe weather is not guaranteed by any means, everyone in the area should prepare for the possibility, particularly during the afternoon hours Thursday.  Severe Thunderstorm or Tornado Watches are possible.  If a Tornado Warning is issued and sirens sound, what will you do?

One suggestion: go to the Android or iPhone app store now and download the app if you haven't already. Thousands of people rely on it for the latest weather info specifically for our area.  You'll find the latest radar loop, our updates throughout the day sent to our Twitter nowcast stream (without subscribing to Twitter), plus you can relay any severe reports back to us via the app as well.  Also in the app, you should go ahead and make the one-time purchase of StormWatch+, which will notify you if severe warnings or watches are issued for your specific location. It's easy to set up and it's the cheapest way to get peace of mind we are aware of.  Links to the apps & more info on them are below.  If you don't have or want to get a smartphone app, stay in touch with the weather conditions in some way tomorrow.  Our social media feeds are another good way to do that.

Definitely plan on heavy rain, perhaps during both rush hours and school drop-off and pick-up.  Take your time when driving in heavy rain. And by all means, keep children away from high or swiftly-moving water and don't drive across areas where water covers the road!

Regarding trick-or-treating, at this point I would suggest just monitoring the weather as the afternoon goes on tomorrow.  My educated guess is that, armed with an umbrella or poncho for the stray showers, trick-or-treat bags will get filled tomorrow evening after 6pm.  If I'm wrong, you won't find me.  I'll be in the custody of federal marshals entering the Witness Protection Program.

"You don't know me" - photo courtesy Wikipedia, public domain

Be safe and stay weather aware!  Hit us up on Facebook, Twitter, or the blog comments below if you have specific questions.

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1 comment:

Anonymous said...

Thanks, Erik! Question. Is the new siren system for G'town already in place? Or are they still working on it?