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Another Stormy Wednesday, Severe Storms Possible

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TONIGHT – OVERNIGHT – WEDS MORNING

  • Scattered rain will be off and on late Tuesday night through Wednesday morning. Lightning and gusty winds possible. Not worried about tornadoes and not worried about severe straight line winds. Here’s the HRRR model through noon Weds:
  • We’re watching for flood potential for this rain tonight – Wednesday morning. That concern is mostly W and NW of us. Yes we got a lot of rain in the last 24 hours. It wouldn’t take much more to push creeks and streams back up. But this doesn’t look like enough rain to raise overnight/morning flood concerns. We’ll see. There’s a Flash Flood Watch just to our west and northwest.

SEVERE SYSTEM DEVELOPS OUT WEST WEDNESDAY

  1. Quiet Wednesday afternoon.
  2. West of us, during the day Wednesday, a significant severe weather event will be ongoing.

SEVERE SYSTEM GETS HERE . . . BUT HOW BAD WILL IT BE?

  • That significant severe event will congeal into one or maybe two lines. It will move east into Davidson and Williamson Counties. ETA could be as early as 6 PM. It could be as late as just after midnight Wednesday night.
  • The initial line should carry the primary severe storm threat because it would arrive with the highest CAPEs and shear.
  • So if there are two lines, the first would arrive here late afternoon/early evening and carry the higher straight line wind, hail, and tornado threat. If a second line comes in behind it closer to midnight it would be primarily for damaging straight line winds (tornado less likely with the second line because the first line will have used up the main source of storm fuel).
  • Or, it’s possible there will just be one big ole line. Here’s what the HRRR shows, just one line, with a 9-10 PM arrival.
  • The initial (only?) line will deliver probabilities for damaging straight line winds (30% probability within 25 miles of you), large hail (5% probability within 25 miles of you), and tornadoes (5% probability within 25 miles of you). Flooding is also possible but the line should move quickly enough to reduce the probability of a significant flash flooding event.
  • The above run of the HRRR shows the line weakening — perhaps weakening significantly — as it arrives here 9-10 PM. That would be outstanding if it happens. But if the line arrives earlier (closer to 6-7 PM), it should be tapping more storm fuel and be stronger. Models have been going back and forth on an early evening vs late evening event. Either could happen.
  • Know today where your safe space will be tomorrow night. Do not leave yourself uninformed, vulnerable, and far from shelter should a warning be issued. Questions? This link may help.
  • This forecast may change, especially the timing, so check our Twitter and other reliable sources of information for updated/new information.

Quick References:

Weather changes constantly.
Follow @NashSevereWx on Twitter for any changes to this forecast.

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Examining “it’s a three out of five weather day tomorrow oh noes,” what it means and what it does not mean, alt. title: respirating into a paper bag

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  1. WINDY. A storm line will arrive Wednesday night, but before that, south winds will howl 20-30 MPH and could gust over 40 MPH. Then when the storm line comes through those winds may briefly intensify and blow from the west/southwest so maybe yeah, tie down your things unless you want them in your neighbor’s yard.
  2. RANT ABOUT /OH NOES IT’S GONNA BE A THREE OUT OF FIVE/. You may have seen/heard breathless exclamations “it’s a THREE out of FIVE” threat based on the below SPC map. It is factually true on the SPC scale this is a 3 of 5 but that is like saying “the Titans are playing an NFL team tomorrow” and getting scared for no good reason — the Titans could be playing any NFL team. For example, Jacksonville (they suck, why worry because /checks notes/ they’re the Jaguars). Or, the Bengals (ruh roh, they are now featuring a competent offensive line and they franchise tagged their interception-making safety). Or, the Colts (whose QB carousel landed on 37 year old Matt Ryan so if the Titans were ever down 28-3 are we worried yet). The point is “three out of five” is like saying “an NFL team is coming to Nissan,” you don’t know whether to be concerned until you hear/read more about the opponent. (Note I considered using a Broadway play analogy but I am uncultured and would have made a mistake ranking the plays, although for sure The Scarlet Pimpernel would have been bottom).

3. TIMING. A squall line is going to come speeding through here probably early evening Wednesday night. “7-8 PM” is NWS-Nashville’s thought which seems about right to me (HRRR model agrees, below) tho that ETA could wiggle earlier or later than that, so look for an update (changes?) tonight and tomorrow. read more