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FXUS64 KOHX 070710 AFDOHX

Area Forecast Discussion National Weather Service Nashville TN 210 AM CDT Tue May 7 2024

New SHORT TERM, LONG TERM

SHORT TERM
(Today through Tonight)
Issued at 202 AM CDT Tue May 7 2024

Radar is clear at forecast time. Same goes for the satellite.
With small to almost zero dew point depressions, fog has already started to develop in many areas across Middle TN. Right now, only a couple of spots are showing anything dense, but this may change over the next couple of hours. Winds at about 1kft are 20 kts off the OHX VAD profiler and this may be enough to keep us from getting widespread dense stuff, but an advisory may become necessary in the next couple of hours.

Well, I'm glad I bumped PoPs from what the NBM gave me yesterday morning. However, storms WAY overperformed yesterday afternoon from what I was seeing in the models at this time yesterday morning. CAPE was near 2000 J/Kg as expected, but even with meager shear, storms were able to produce large hail, damaging wind and from the look of it, possibly a couple tornadoes. That does not bode well for the next couple of days because forecast soundings over the next 72 hours look much more severe than yesterday.

Let's start with today. Remnants of yesterday's High Risk area over the Plains merged into a QLCS last night, which is now wreaking havoc over western Missouri. This QLCS feature will continue pushing eastward through the morning hours and while latest CAMs have it falling apart upstream from us late this morning, the residual outflows from this system may very well provide us with the lift I thought we may be missing today. Forecast soundings are healthy.
2500+ CAPE values, lapse rates similar to yesterday and much better shear values than I was seeing for yesterday's storms. For these reasons, while I think damaging wind gusts (60+ mph) and large hail will be the main threats, any storms that develop will likely be rotating, so while lower on the totem pole, I can't rule out a tornado threat. In addition, with the amount of rain we've received over the last couple of days and PWs in the 90th percentile this afternoon, localized flash flooding is also possible. Please don't sleep on the flash flood threat and heed any warnings that may be issued. Ok. That's just the afternoon. Almost across the board, CAMs are showing additional development tonight as another wave passes through the region. While we lose some of the heating of the day, CAPE values only fall into the 1000-1500 J/Kg range. This means we'll hold onto plenty of instability during the overnight hours.
Deep layer shear holds steady around 40 kts and helicities are such to sustain updrafts. This means we'll hold an overnight severe threat, as well, with any additional storms that develop. It also means that we're going to be dealing with overnight severe potential two nights in a row.

LONG TERM
(Wednesday through next Tuesday)
Issued at 202 AM CDT Tue May 7 2024

While today and tonight's severe threat is healthy, that might make Wednesday's severe potential super human. In fact, with the forecast soundings I'm seeing I am becoming a little worried. As tonight's storms wane towards daybreak, the boundary created by them is actually being picked up in some of our models. This is unusual and may serve as a quasi-warm front that is expected to slowly lift back to the north during the late morning and early afternoon hours on Wednesday. As it lifts, there is some signal of convection developing along this boundary. With forecast soundings showing 3000+ CAPE south of the boundary, plenty of shear and mid-level lapse rates closing in on 7.0 deg/km, there is some concern of discrete supercell development Wednesday afternoon. Supercell composites closing in on 10.0 and STP values nearing 2.0 suggest a fairly decent chance of tornado development. In addition, lapse rates only get worse through the afternoon. This means large hail (1.5 inches or larger) is going to be possible. While the afternoon potential for severe weather is more on the isolated to scattered level, yet another round of much more widespread storms is still expected Wednesday night. Again, this is an all-mode severe weather threat overnight Wednesday into early Thursday morning, with damaging wind gusts, large hail, tornadoes and flash flooding all possible.

The next 48-60 hours is going to be VERY active across Middle TN.
This is not a time to fret, however. Take this morning and review your safety plan for you and your family. Know where you need to go for shelter if you go under a warning. Wherever that shelter may be, have essential items in there waiting for you. Phone chargers, NOAA Weather Radios, helmets for the kiddos, just to name a few.
If you need additional support for making a plan, please visit ready.gov/plan to help you put one together. Don't wait until you go under a warning. Be prepared. Especially with overnight severe threats for the next two nights. Don't go to bed without having your phone fully charged and the volume turned up so you can wake up and get to shelter.

Once we get through early Thursday morning, I think the severe threat is over. There is an outlier signal from the NAM that the front may not get all the way through Middle TN on Thursday and we could see additional storms Thursday night across our south, but let's deal with that once we get through the next two days. By Friday, temperatures relax back into the 70s and while the GFS is suggesting some showers and storms on Saturday, most models do not, so hopefully we can remain dry for several days after Thursday morning.

AVIATION
(06Z TAFS)
Issued at 1231 AM CDT Tue May 7 2024

Patchy to locally dense fog has developed early this morning, especially for CSV/SRB. Expect this trend to continue through the early morning, before returning to VFR across the area. May have a few periods of low cigs near sunrise as well. VCTS will be in the area through this afternoon, but not enough confidence to include TSRA for any specific terminals at this time. Winds will remain from the S/SW, becoming gusty up to 20 to 25 kts in the afternoon.

PRELIMINARY POINT TEMPS/POPS
Nashville 85 70 85 69 / 30 60 80 100 Clarksville 83 68 83 67 / 40 60 90 90 Crossville 80 64 80 63 / 30 70 70 90 Columbia 84 68 86 66 / 30 70 70 100 Cookeville 81 66 81 65 / 30 70 70 100 Jamestown 82 64 80 64 / 30 70 70 90 Lawrenceburg 83 68 85 66 / 40 70 70 100 Murfreesboro 85 68 85 66 / 40 60 70 100 Waverly 83 68 85 66 / 30 70 90 100

OHX WATCHES/WARNINGS/ADVISORIES
None.

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