Enhanced Risk: details on our severe weather threat tonight

I’ll excuse you given the current circumstances if you have not stepped foot outside yet this morning, but my gosh is it sticky! With dewpoints near 70 and temperatures already crossing the 80 degree mark at noon as the sun starts peeking out, it’s feeling like early summer.

What if I told you that tomorrow afternoon will be about 20 degrees cooler with the humidity long gone and a northerly breeze? You might rejoice, but also think, “something must be happening between now and then to cause that…?” And you’d be right – that something would be a potent cold front arriving around midnight tonight.

Given the conditions ahead of the front, and the potency of the front itself, it’s not surprising that thunderstorms are thus expected. A few other contributors make this event into one with potentially higher severe chances. Very cold air aloft is moving in, which contributes to the instability but also to ice formation aloft (=> hail below). Also, wind energy is pretty stout as well. Taken together, we have been placed under a Level 3 (of 5) threat for severe weather, an Enhanced Risk, by the Storm Prediction Center.

How it should play out

Storms will form well to our north near the Ohio River and likely become severe. As the front pushes quickly south, additional storm development takes place and likely congeals into a squall line or multiple line segments as it nears the metro. If there are multiple lines, they likely consolidate by the time it pushes into north MS and exits the area.

Timing

Approximately 10pm-1am. The storms likely enter the northern metro around 10pm, move through the city in the 11pm hour, then cross the state line and exit the metro after midnight. All times are +/- an hour or so. It’ll be quick-hitting as the storms will be fairly progressive in their motion, if not their politics. You may experience less than 30 minutes of heavy rain and other impacts as it drops south.

Threats

  • Very heavy rain and lightning/thunder.
  • Strong and gusty wind with the potential to briefly exceed 60 mph. 
  • Large hail, like we haven’t seen in a long time. The Storm Prediction Center places our area in a “hatched” zone, meaning there is a 10% chance of hail to 2″ in size.
  • Isolated tornado. The threat is pretty low, especially if the line is fully formed as it moves through. However, if we see any renegade storm cells that don’t want to get in line, the threat goes up a bit.

Severe weather probabilities for tonight’s event, within 25 miles of you. The black hatched area in the hail panel indicates a 10% probability of hail stones 2″ or larger occurring. (NOAA/SPC)

Boom/bust potential

The forecast timing seems fairly cut and dry, but there is still a potential bust scenario (which for people rooting against severe storms is actually a good thing). One of our “trusted models,” the HRRR, runs every hour and has yet to move a line through the metro. It keeps the bad stuff just north and east of us. It’s cousin, the NAM3 model, only runs four times a day, but the last couple of runs hit us pretty good with a squall line. Given the ambient conditions ahead of the front, I unfortunately side with the latter. Other less-high-res models agree too. But don’t be shocked (and do be pleased!) if this thing misses us entirely. Thus, our severe threat is CONDITIONAL on storms actually moving through the metro. If they do, they’re likely to be strong.

The 10am run of the HRRR model showing simulated radar data from 3pm-4am indicates that the main line will just miss us to the northeast. It’s been consistent with this trend and is good news. (WxBell)

The 7am run of the NAM3 model showing simulated radar data for the same timeframe indicates that the main line will move right over us. It’s also been consistent with this trend and is not as great news. (WxBell)

Preparedness

Garage your vehicles if able when the sun goes down tonight. Tie down anything outdoors that weighs less than a small child and which you wish to keep. Make sure storm drains are clear of the crap that is falling from the trees. If it’s garbage day tomorrow, take the trash can out in the morning lest your neighbors shake their fists at you when your trash is all over their yard.

Finally, in all seriousness, have multiple ways of getting warning information tonight. If you’re not staying up, they need to be the type to wake you up. NOAA Weather Radio is great. Severe weather apps are great*, including SW+ Alerts in our very own MemphisWeather.net app, available in the App Store. Social media is fine too, but likely won’t be as timely and storms will be moving quick tonight. Not recommended unless you are following the right people and continuously updating your feed. (Our Twitter feed will be a good source!) And of course, since it won’t go deep into the night, you can always stay up and keep the TV on. Sirens are not good – they won’t warn you of large hail or high wind, and they likely can’t be hear by most people who are asleep in a well-insulated home.

* Note that most severe weather apps, including MWN, and also Wireless Emergency Alerts require that you have your volume ON and Do Not Disturb OFF to get audio alerts that you can actually hear. Here’s more on how to configure your settings for SW+ Alerts, available in the MWN app.

After this passes, much cooler but not unpleasant weather is expected for a few days. Then, we’ll be watching Easter Sunday like a hawk. It holds our next potential for severe weather. Then more unusually cool weather.

Erik Proseus
MWN Meteorologist

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MWN is a NOAA Weather Ready Nation Ambassador Meteorologist Erik Proseus is an NWA Digital Seal Holder

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