Update on Trick-or-Treat Rain/Storm Chances

Today – Breezy & Warmer – High 61

10a 44 . 1p 57 . 4p 60 . 7p 55 . 10p 50

Here’s how cold we were at 4 a.m. this morning:

Our official low was 29 (at 5 a.m. and 7 a.m.).

We are rapidly warming up. A few clouds will stream in, but no rain.

Sunday – Pleasant – 44/62

7a 45 . 10a 53 . 1p 60 . 4p 61 . 7p 55 . 10p 49

No overnight freeze! Scattered clouds. No rain.

Next Week – Mid-Week Rain/Storms?

Warm Air: Monday’s high is 63. Tuesday, we warm to 73; by Wednesday, 77! All this is driven by south winds driving in warmer air. This process is called “warm air advection.”

Cold Front: A cold front trailing from a strong low pressure center will drag across the central U.S., and collide into our warm air.

Our NWS wrote this morning: “Models continue to show differences [about when this will get here], with the GFS about 18 hours faster with the main band of moisture [rain/storms] than the ECMWF. . . . We continue to see some potential for strong storms sometime from late Wednesday through late Thursday.”

The GFS thinks this rain will arrive Oct 31 in the afternoon, ending mid-evening (see below). The ECMWF starts the rain near the end of trick-or-treating.

NWS & other weather sources (and probably your apps) are dealing with the ETA uncertainty by spreading rain chances of 20% to 50% from Wednesday through Friday. When trying to express rain/storm chances in percentages, this is the way to do it. Just keep in mind this was done to “hedge their bet,” because we don’t know when the rain/storms will be here.

The Storm Prediction Center is also watching this system. Model differences prohibit any substantive forecast, but the ingredients for strong or a few severe storms may be present.

So, What Should We Do About Trick-or-Treating? With the models unable to settle on a consensus, there’s no reason to move the designated night, at least not yet. But, you should be thinking about Plan B. Here’s how the GFS predicts the precip October 31 at 7 p.m.:

We’ll update this forecast tomorrow. Questions about Davidson or Williamson Co.? We’re on Twitter @NashSevereWx.