Christmas Day – Heavy Rain, Areal Flood Watch Williamson Co., Thunderstorms Also Possible – Early 61° High 65°
Heavy rain is on the way.
Flooding potential remains high in areas in and around the Watch area. Here’s the official text of the Watch:
Rainfall will be heavy. Forecast soundings show all time high precipitable water values for Christmas Day: 1.7″. Think of precipitable water like this. If you stuffed a towel in a giant tube, sent the tube straight up in the air through the atmosphere and let it soak up the moisture, then squeezed it out, you’d get 1.7″ of water.
Rain will arrive in the morning. HRRR thinks just after sunlight:
This rain will continue, off and on (mostly “on”), throughout the day and night.
Turn around, don’t drown. Even a little water can wash out roads or carry away any vehicle. Here’s the GFS model’s 24 hour rainfall total for Christmas Day:
Rain totals should increase to 1.5″ to 2″ through Saturday morning.
In addition to the rain, thunderstorms remain a concern. The HRRR model, below, has heavy rain and probably thunderstorms as early as 8 AM:
The Storm Prediction Center thinks a “few transient supercell structures and short quasi-linear segments capable of isolated damaging winds and a brief tornado or two” anywhere inside the brown area. The concern is greater in the morning and afternoon than it is at night. Yes, we are included, but it’s a huge area. Do not worry, but stay informed.
This severe risk is substantially lower than Wednesday’s was, but you need to have a half-eye on this system tomorrow. Don’t let it get in the way of your Christmas joy, but do not forget about it, either. We’ll be on Twitter, as always.
The bulk of the rain should end Saturday morning as the front lifts north of us.
Saturday’s going to be humid, even sticky, as dew points return to summer-time-sweaty mid-60°s level.
By Sunday, the same front that will have lifted north on Saturday is expected to return, delivering more rain. In fact, a LOT more rain. The Titans game looks to be bog.
The Next Storm System
Flooding concerns will be heightened Monday with the next storm system. From now to Monday night, 3″ to 5″ additional inches is forecast.
4" to 5" rain forecast next 5 days. Flooding may be an issue by the end of the weekend-Monday. pic.twitter.com/RU3z0bjMvV
— NashSevereWx (@NashSevereWx) December 24, 2015
In addition to the rain, severe weather remains possible as a closed low is expected to pass to our NW (see 1, below), allowing powerful winds aloft to wrap around the south side of it, then curve into Middle Tennessee (2). See below:
In broad terms, this is a good setup for severe weather. But, remember, severe weather requires the precise placement of specific ingredients. This system is way too far away to know if those will come together. The predictability is just too low.
Storm Survey Results
There were three tornadoes in Middle Tennessee last night. The first, in Linden, was an EF-2, maxing out with 115 MPH winds. It traveled 14 miles. Along the way, it struck a home and killed two people.
The second tornado struck the Lutts community in Wayne County. It was an EF-3, with 157 MPH winds, and was 800 yards wide. It was on the ground for exactly 60 minutes, having traveled 50.6 miles, and ended in Maury County.
The third tornado came out of Alabama into Wayne County. It was rated EF-1 for 110 MPH winds. It traveled 3.6 miles.
This website supplements @NashSevereWx on Twitter, which you can find here.
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