March 23: Strong Storms Thursday, Daily Links

WEATHER

Another warm and breezy day in store for us today — we won’t see as much sunshine as we did yesterday, but temperatures will still end up about 10 degrees above average:
PAUL DAYPART GRAPH tumblr_inline_mzxir4Rmas1s4v4p9

Sustained southwesterly winds of 15-20 mph will occasionally gust up to around or even over 30mph:
PAUL RPM WIND GUSTS tumblr_nbmy5grjng1tozkiyo8_500
I’m leaving the forecast dry today, but a sprinkle or two is within the realm of possibility.  I wouldn’t worry about it.

A good chance (near 100%) of rain is on the way for Thursday.  As always seems to be the case, the severe weather threat is complicated — there are some factors that point to a good chance of severe thunderstorms, and there are some factors that do the opposite.  Let’s break it down…

ELEMENTS FAVORABLE FOR SEVERE WEATHER:
1) There will be storms.  This one seems obvious, but you can’t have severe thunderstorms unless you have thunderstorms in the first place.
2) The wind profile in the atmosphere looks like it will be very favorable for stronger thunderstorms to become even more organized, and thus more capable of producing severe weather (“severe” defined as wind gusts over 60mph, hail over 1″ across, or a tornado).
3) The most-likely timing of the storms will be from midday through the afternoon, which is also when the atmosphere is the warmest and the most-unstable.

ELEMENTS NOT FAVORABLE FOR SEVERE WEATHER:
1) Even the most-unstable time of day won’t be that unstable on Thursday.  Dew points will only climb to the upper 50s on Thursday, which means the humidity (or lack thereof) could be a significant limiting factor.
2) Early morning showers and non-severe storms could further reduce the instability available to fuel severe thunderstorms later in the day.  I’m forecasting a high of 70, but if we stay even a few degrees cooler, it would help.
3) The timing is still uncertain!  I’m modestly confident in the timing I’ll outline below, but some forecast models are bringing the storms through earlier (when the atmosphere wouldn’t quite be as “ready to go” for severe weather).

With the usual caveat that there will be forecast revisions as we get more data, here’s what I’m thinking right now in terms of the “most likely” scenario.  We’ll see thickening clouds overhead tonight, with scattered showers and non-severe storms developing in the morning.  The RPM forecast model shows that pattern:
RPM 4A THU RPM 6A THU RPM 8A THU RPM 10A THU

Stronger thunderstorms will develop in western Middle Tennessee by late morning to around midday, and they’ll move west-to-east throughout the afternoon and into early evening:
RPM 12P THU RPM 2P THU RPM 4P THU RPM 6P THU RPM 8P THU

Like I said above, the atmosphere won’t be ideally set up for those midday and afternoon storms to become severe.  But it doesn’t have to be ideally set up — conditions just have to be “good enough.”  The Storm Prediction Center’s SREF (short-range ensemble forecast) model shows a 50-70% chance of those “good enough” conditions coinciding with the timing of the storms:
SREF_prob_combined_supercell__f039 SREF_prob_combined_supercell__f042

But even the “good enough” conditions will be borderline.  The Supercell Composite Parameter forecast shows values around or above 3 during the afternoon Thursday — I don’t get too amped up about that statistic until it reaches 6:
SREF_SCCP_MEDIAN_MXMN__f039 SREF_SCCP_MEDIAN_MXMN__f042

I expect that the main severe weather threat around here will be the potential of damaging straight-line winds.  Because our instability levels will be so borderline, large hail or tornadoes aren’t the primary concern.  The SREF’s forecast for the Significant Tornado Parameter shows values around 1 — and that means we can’t cross the tornado threat off the list completely:
SREF_SIGTOR_MEDIAN_MXMN__f039 SREF_SIGTOR_MEDIAN_MXMN__f042
I think the greatest risk of large hail or tornadoes will shape up down to our south, but you can be sure we’ll keep an eye on any local thunderstorms for signs of rotation.

The Storm Prediction Center has outlined a “Slight Risk” (level 2 of 5) area for severe thunderstorms over much of the Midstate tomorrow — basically, the eastern two-thirds of the Midstate:
PAUL SEVERE RISK REGION
If the favorable elements I outlined above begin to more dramatically outweigh the unfavorable elements, it’s possible that the SPC could bump parts of that Slight Risk up to an Enhanced Risk (level 3 of 5).

The analog forecasts, which compare the current weather pattern to similar historical patterns, show a just-over-50% chance of at least one severe weather report in the Midstate…
SVRall_N1_110km_nam212F060
…and a 20-30% chance of at least five severe reports, with the higher chances in the southern half of the Midstate:
SVRall_N5_110km_nam212F060

BOTTOM LINE: You should plan on staying weather-aware on Thursday, but there isn’t any reason to go into panic mode.
1fGFBA

There’s still a significant chance that this will be a severe thunderstorm chance that fizzles out — let’s hope so!  But it’s always a good idea to plan for the worst and hope for the best.  Any watches/warnings that are issued will be automatically posted to Twitter (links below).  Twitter has recently started messing with showing you tweets out of order — if you want to reset your stream to chronological order, I pinned a tweet with instructions to the top of my profile.

I always say it, but I’ll say it again: Facebook is NOT a reliable source of severe weather information.  Would you want the same service that shows you someone’s birthday message two days late to deliver a severe thunderstorm warning two days late as well?
tumblr_n3lnedONnr1smcbm7o1_400

Once Thursday’s storms move through, a cooler pattern will settle in for Friday and Friday night…but a nice warm-up will kick in again Saturday — in fact, Saturday looks nothing short of spectacular!  (Let’s hope that part of the forecast stays consistent.)
WSMV 7 Day AM
Notice the good chance of showers and storms on Easter Sunday — I’m hopeful that Easter morning will still be dry, with the better chance of storms arriving later in the day.  Some of those storms could be feisty as well — we’ll keep you updated on all of that as the weekend approaches.

 

LINKS

Your daily dose of weather, space and other nerdiness…

 

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Social media links

Twitter: @WSMVweather, @PaulHeggenWSMV, @WSMVLisaSpencer, @WSMVDanThomas, @WSMVNancyVanC, @NWSNashville

Facebook: 4WARN Weather, Paul Heggen WSMV, Lisa Spencer, Dan Thomas WSMV, Nancy Van Camp WSMV, NWS Nashville

Instagram: PaulHeggenWSMV

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About paulheggen33

Morning meteorologist for WNCN-TV in Raleigh.
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One Response to March 23: Strong Storms Thursday, Daily Links

  1. Pingback: March 23 Evening Update | 4WARN Weather Blog

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