4/07/06 FCST: MS, LA, AR, TN, AL, KY, GA

It appears that Friday is shaping up to be a very rough day to be a resident across the SRN US. Forecast conditions and parameters seem to be pointing to a pretty major severe weather episode, yet again.

It appears that by tomorrow, a very unstable atmosphere should exist over much of this area. A mid-level dry punch should work into the area sometime tonight, which will create steep lapse rates. I would expect the clouds from any overnight convection to be diminished or out of the area soon after the sun comes up, so heating should begin right away. It appears SB CAPE should climb into the 2000-3000 range over most of the area by early afternoon. LI's to -7 should be possible over much of the area. And dewpoints will likely reach into the mid 60's. All of these ingredients combined should set the stage for intense severe thunderstorm development and will only need some lifting mechanisms to arrive to kick off the show.

Things should remain capped for the most part until the afternoon, when an 80 knt jet streak should begin to arrive. This should create for explosive thunderstorm development across the WRN portions of the threat area. And with the strength of the forcing that will be present, I don't see any cap worries. There should be more than enough available forcing to erode even a fairly strong cap. Also of note is the boundary/s that could be left over from tonight's activity. These could become a focus for new development tomorrow, in areas farther to the E within the threat area. As such, we may witness two or more waves of severe convection firing.

The dynamics again look very good, with that 80 knt (or more) mid level flow. Both deep layer shear and low level shear look good. Directional shear over the outer edges of the threat area could be better, but for the most part should be adequate over the SPC's moderate risk area. The 0-1 km shear looks more than favorable for supercell storms. And in areas just to the E of the secondary low that is suppose to develop over SERN MO and NERN AR, where winds will back......as well as along any boundaries that may be out there, the tornado risk should be enhanced.

Climatologically, this general area is very favored for significant outbreaks of severe weather this time of year. Some recent ones include Apr 8 and Apr 16, both events in 1998 that each resulted in a violent, F5 tornado. While I am not going to predict the formation of any violent tornadoes at this time, I will say I would not be at all surprised to see a few that are strong to violent over this area, based both on the expected conditions and parameters, as well as the area's climatology.

Some of the larger towns and cities I feel are most at risk include:

In Tennessee: Memphis, Jackson, Nashville, Columbia, Clarksville

In Mississippi: Tupelo, Columbus and Jackson

In Alabama: Birmingham, Hamilton, Florence, Decatur, Huntsville and Tuscaloosa

And in addition to the threat of large hail, damaging winds and tornadoes, the threat for flooding will also exist, due to the multiple waves of storms that may develop over the threat area, as well as PW values that range from 2.5 to 3.5. And this isn't just limited to the moderate risk area. Heavy rain may also pose a threat of flooding all the way up into KY, IN and OH.

In short, unless we see drastic changes, I expect tomorrow to be a very busy day for folks across these areas of the south. But one can never be sure. It seems recently the models have been fairly consistent with these systems right up until the night before...then they paint a totally different picture than they had the previous few days. But we'll see.
 
HIGH RISK


Well it appears that tomorrow will be bad. Anybody ever seen a High Risk on day 2 outlooks?

I understand the reasoning. Tds should be very high in the upper 60s. Shear will be amazing as the jet streak works through.

NAM has capes of 3000... does anybody like to chase in the trees? :D
 
Please remember the FCST threads are for discussing FORECAST aspects of severe weather not happening yet. This is not the place to go over terrain quality, places to eat in the area or who you will be visiting if you decide to chase this day. Terrain quality of the potential chase area can be discuused in a DISC thread about the day, but let's leave out your vacation plans all together please.

Thanks.

EDIT: NOR TO DISCUSS YOUR PLANS TO GO HUNTING TURKEYS. :rolleyes:
 
i dont know the history or accuracy of the WRF but the 21z sampling out of nashville is quite scary.

LI's: -11
cape: 1810
LCL: 147.4
Lapse Rate: 7.8 c/km
SRH: 281.6

The only negative is the CINH: -36.9
i dont know enough about forcasting to know if that is breakable or not. if anything can break it then watch out. ofcourse with an 80kt jet nosing into the region at about the same time i would think there wouldn't be any problem with forcing to break the cap. and the cap might be what helps keep the storms discrete.

any comments would be greatly appreciated.
 
Yeah the cap is something im working with myself but I think this cap is not too robust & plenty of dynamics should overcome that progged cap.If I could position myself in target, Id pick NW Alabama. Should be interesting there. Todays lesson seemed to be the highly charged jet stream that tore potentially dangerous supercells apart or suppressed them. Tomorrow I believe that wont be the case with alot more reports of tornadoes pouring in. Especially bad if NW Tennessee gets hamered again. SPC has a substantial threat for that region.
 
Yeah the cap is something im working with myself but I think this cap is not too robust & plenty of dynamics should overcome that progged cap.If I could position myself in target, Id pick NW Alabama. Should be interesting there. Todays lesson seemed to be the highly charged jet stream that tore potentially dangerous supercells apart or suppressed them. Tomorrow I believe that wont be the case with alot more reports of tornadoes pouring in. Especially bad if NW Tennessee gets hamered again. SPC has a substantial threat for that region.
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Based on the amount of wind shear aloft, and the high CAPE tendencies, I would probably target Nashville, TN it looks like strong, to severe tornadoes will be spawned just short south of there given the jet streak and LCL's. How can they word something so strongly on a day 2? They are EXPECTING a outbreak......wow....
 
HOLY CRAP!!! just checked the 0z NAM and its showing 3000-3500 cape in Nrn MS at 18z.

and the 0z NAM profiler from nashville, TN is showing at 21z
LI's: -8.2
CAPE: 3738 j/kg!!!!
CINH: 0.0

LCL: 819.3
Lapse Rate: 7.0 c/km
SRH: 158
 
TN looks extremely dangerous as highlighted the 0z nam. Earl Barker's page is plotting 3500+ Jkg SBCAPE with 200-300 1km SRH values across the western and central parts of the state from 18z through 0z. 1km EHI values are from 4 to 5.5, which suggests violent tornado potential as per SPC's Day 2 wording.
 
After looking at the 00Z NAM, My target is my hometown, Hernando, MS.


18Z forecast for Tunica, 40 miles south of Memphis:

CAPE 3844j/kg!!!!!!!!
SWEAT 453!!!!!
LI -9.2
0-3km EHI 5.2
CINH 0.0 j/kg
 
Just a quick update to yesterday's forecast. As is already fairly obvious by looking at the SPC's Day 1 Outlook, conditions remain highly favorable for the development of severe and tornadic thunderstorms this afternoon and evening over areas of the south. A high risk outlook has been issued by the SPC for areas of SRN TN, NRN MS and NRN AL.

Conditions appear to look just as favorable today as yesterday. In fact, if anything, today's potential looks even better now.

Taking a look at sfc obs across the area, temperatures are already into the low 70's and dewpoints vary from the mid 60's in MS to the low 60's as far N as SRN IL/IN! This is at 10:14 AM CDT! So the previous concerns that the ETA might be overestimating the dewpoints a bit seems to now be a non-issue.

Also of note, much of the morning precip expected to be over the ERN areas of the outlook never materialized, thus these areas may be at a greater risk later this evening and tonight, because the atmosphere won't be as "used up" with the extra amount of sfc heating that should be able to take place.

Attm, there is quite a bit of cirrus overspreading the region, visible on satellite imagery. But it appears that despite this, plenty of sunlight is making it to the sfc, as is ecvidenced by the sfc obs.

Currently there is an area of conevction firing over WRN TN, with an isolated severe hailer among them. This action appears to be racing on off to the NE. Just as I type this, a new tornado watch has been issued for WRN KY and TN. So from this point further, it looks like the discussion will be most appropriate for the NOW thread. Looks like a big day.
 
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