March 31st Severe Threat

[pen_artist]

Haven't looked much into the setup myself but have heard some rumblings of a bigger severe threat later this week for western chunk of the subforum. Thought I'd get a thread going for it since it is looking like something will shape up.

[Chicago Storm]

I would bank on this trending slower, and thus trending west.

[A-L-E-K]

smart^

[andyhb]

CSU MLP is going off for Friday with a massive 45% hatched area.

[sbnwx85]

55 minutes ago, andyhb said:

CSU MLP is going off for Friday with a massive 45% hatched area.

Went ahead and stole it from Twitter:

[andyhb]

500 mb presentation on the Euro is a classic for a significant severe event in the Midwest.

[CheeselandSkies]

Looking at Friday as my first chase day of the year. Hope it doesn't trend too much further west, as I have work till noon and will have been up since 2AM (3AM start). I believe the 5-hour positioning drive immediately after my shift clouded my decision-making last April 12th, contributing to me missing the Gilmore City tornado despite being like 10 miles from the storm when it first went severe-warned.

[CheeselandSkies]

3 minutes ago, andyhb said:

500 mb presentation on the Euro is a classic for a significant severe event in the Midwest.

3/28/20 do-over?

[cyclone77]

1 hour ago, CheeselandSkies said:

Looking at Friday as my first chase day of the year. Hope it doesn't trend too much further west, as I have work till noon and will have been up since 2AM (3AM start). I believe the 5-hour positioning drive immediately after my shift clouded my decision-making last April 12th, contributing to me missing the Gilmore City tornado despite being like 10 miles from the storm when it first went severe-warned.

I'll be down at Lake of the Ozarks Thu/Fri so no chasing for me with this.  Will definitely be following it though as it looks pretty interesting.  Nice to see a setup in the forecast.  

[Chambana]

2 minutes ago, cyclone77 said:

I'll be down at Lake of the Ozarks Thu/Fri so no chasing for me with this.  Will definitely be following it though as it looks pretty interesting.  Nice to see a setup in the forecast.  

Ozarks are fun as hell, enjoy cyclone!

[andyhb]

5 minutes ago, cyclone77 said:

I'll be down at Lake of the Ozarks Thu/Fri so no chasing for me with this.  Will definitely be following it though as it looks pretty interesting.  Nice to see a setup in the forecast.  

You could take a... "detour" to Eastern AR perhaps.

[Indystorm]

Looks ominous for a large area and if storms continue to occur with this frequency that we have currently seen and with higher amplitude our Midwest may be in for quite a svr wx season this spring.

[nwohweather]

Picked a bad weekend to be in the Carolina’s. Would’ve chased this for sure

[mnchaserguy]

I would like to think I am going to be chasing this but at this point I don’t think it’s worth the drive from Minneapolis. If it slows down and/or shifts back north then it might be on the table for me.
Right now this is a very progressive system which means fast storm motions. This is backed up by 50+ knot Bunkers right storm speeds. This will make keeping up with the storms difficult. The only area with backed winds are going to be tucked up right up on the center of the low. That really cuts down the area to work with and the window of opportunity to get a storm to produce. That being said, all it’ll take is one or two storms in that environment to go crazy. Very nice low and mid level SRH and 75 knots of effective shear. The biggest question will probably be the quality of moisture return, which the SPC mentions in their D4 outlook.


.

[Chinook]

With the GFS right now, it seems like this would be a northern threat somewhat removed from a southern threat. The 00Z ECMWF doesn't really have the same exact setup. The low pressure placement at 00z (Apr. 1, or, 8:00PM eastern on the evening of Mar. 31) is kind of different from the GFS. Along with this, the surface winds to perhaps 850mb winds much more in the realm of southwesterly rather than southerly. I think there is certainly some disagreement as to the synoptic features.

[CheeselandSkies]

18Z GFS getting the low down to 979MB on the IA/MN border at 21Z Friday. Just southeast of the triple point in east-central Iowa is a pretty screamingly obvious target, square in the left exit region of the mid-level jet. For some reason low-level backing isn't stellar despite the powerhouse low. 18Z NAM, surprisingly, is more progressive and somewhat weaker initially but deepens the low from 21Z to 00Z with better low-level shear, with the target right over MBY into north-central IL.

MKX remaining noncommittal, understandable at this point given the usual uncertainty with warm fronts in this region this time of year.

Quote

The main question is how far north
will the warm front get as this will play a major role in the
weather we see Friday. Bumped temperatures down from what the NBM
had due to this uncertainty keeping the northern half the the CWA
several degrees colder. The initial warm air advection will bring
mainly rain chances to the area as the atmosphere warms. Heading
into Friday we have better chances for instability and with the
low level jet in the area plenty of shear. If the variables come
together we will have the potential for some strong to severe
storms Friday afternoon and evening.

 

[CheeselandSkies]

Also notable that the 00Z NAM forecast dewpoint in east-central Iowa for 21Z tomorrow is 7 degrees. In 48 hours that's supposed to be nearly 60.

In fact, last couple of NAM runs (especially 00Z) suggesting the northern end of this setup might struggle with moisture return moreso than previously thought. That cold high pressure tomorrow is really gonna wipe it out. OTOH it is the NAM so... And the precip fields even appear to be popping an arc of semi-discrete convection in that classic sweet spot just southeast of the surface low.
 

[andyhb]

1 hour ago, CheeselandSkies said:

Also notable that the 00Z NAM forecast dewpoint in east-central Iowa for 21Z tomorrow is 7 degrees. In 48 hours that's supposed to be nearly 60.

In fact, last couple of NAM runs (especially 00Z) suggesting the northern end of this setup might struggle with moisture return moreso than previously thought. That cold high pressure tomorrow is really gonna wipe it out. OTOH it is the NAM so... And the precip fields even appear to be popping an arc of semi-discrete convection in that classic sweet spot just southeast of the surface low.
 

Probably because it's almost -20 degrees at 500 mb and below freezing at 700 mb yielding extreme 0-3 km CAPE and low-level lapse rates.

[andyhb]

Huge D3 enhanced/30 hatched area issued.

Quote

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0236 AM CDT Wed Mar 29 2023

   Valid 311200Z - 011200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE MID-MISSISSIPPI VALLEY TO THE MID-SOUTH...

   ...SUMMARY...
   Potentially intense and widespread severe thunderstorms are expected
   Friday afternoon into the overnight hours across portions of the
   Middle Mississippi Valley and Mid-South vicinity, eastward to the
   Lower Ohio and Tennessee Valleys. Damaging gusts and tornadoes will
   be the main hazards with this activity.

   ...Arklatex to the Mid-MS Valley and eastward to the OH/TN
   Valleys...

   Widespread, regional episode of severe thunderstorms is possible on
   Friday.

   An intense mid/upper trough is forecast to eject eastward across the
   Plains to the central U.S. on Friday. Intense deep-layer
   southwesterly flow will accompany this system, with a 100+ kt 500 mb
   jet expanding over much of the Midwest. As the upper trough deepens
   during the afternoon and evening, a 60-70 kt southwesterly low-level
   jet will overspread much of the risk area. These flow fields will
   favor a fast-moving squall line shifting across the Mid-MS
   Valley/Mid-South toward the Lower OH and TN Valleys. 

   At the surface, strong southerly low-level flow will transport 60s F
   dewpoints northward. Near-60 F dewpoints are expected as far north
   as eastern IA to northern IL and then central IN as the surface low
   tracks east/northeast from IA early in the day, to southern Ontario
   by Saturday morning. While some questions remain regarding moisture
   with north and east extent into the OH Valley, forecast soundings
   indicate at least a few hundred J/kg MLCAPE will exist during the
   evening as far east as the I-65 corridor in KY/TN. Given intense
   flow fields, a threat for damaging gusts will persist from MO/IA
   into the Lower OH Valley.

   Across IA/MO, initial supercell development is possible near the
   surface low/triple point. Fast moving storms may produce possibly
   significant damaging gusts and tornadoes. Upscale growth into a QLCS
   is expected to occur rapidly given strong forcing/vertical shear.

   Further south into the Mid-South and vicinity, large-scale ascent
   will be somewhat weaker further removed from the upper trough.
   However, flow fields will remain intense and a mixed mode of
   supercells and linear convection is expected. All severe hazards
   (damaging gusts, tornadoes and isolated hail) are expected by late
   afternoon into the evening hours.

   ..Leitman.. 03/29/2023

[frostfern]

15 hours ago, CheeselandSkies said:

Also notable that the 00Z NAM forecast dewpoint in east-central Iowa for 21Z tomorrow is 7 degrees. In 48 hours that's supposed to be nearly 60.

In fact, last couple of NAM runs (especially 00Z) suggesting the northern end of this setup might struggle with moisture return moreso than previously thought. That cold high pressure tomorrow is really gonna wipe it out. OTOH it is the NAM so... And the precip fields even appear to be popping an arc of semi-discrete convection in that classic sweet spot just southeast of the surface low.
 

It looks like a more of a cold-core setup that's more dependent on steep lapse rates than high dewpoints.  If you can get large CAPE with surface temperatures only on the upper 60s, that's not a big dewpoint depression.  I think early spring 70/58 ttd can be more of a tornado threat than 85/64 ttd late spring, given the same CAPE and shear.

[CheeselandSkies]

Yeah @andyhb that 3CAPE is a big red flag screaming "CHASE THIS!"

[frostfern]

7 hours ago, CheeselandSkies said:

Yeah @andyhb that 3CAPE is a big red flag screaming "CHASE THIS!"

Cells will be moving crazy fast though.   I'd definitely study the road networks ahead of time in the target area.

[Malacka11]

@A-L-E-K @Chicago Storm Would you chase this? Assuming making the drive over to Iowa isn't an issue?

[andyhb]

Early 3 km NAM runs certainly don't do anything to suppress this potential. Impressive parameter space across the entire warm sector.

[Chicago Storm]

1 hour ago, Malacka11 said:

@A-L-E-K @Chicago Storm Would you chase this? Assuming making the drive over to Iowa isn't an issue?

I've been watching... Still a bit too far out to make a final decision, but personally I may sit this one out to save days off for other opportunities down the road (Events without 50-75MPH storm motions and potential upscale growth issues). We'll see...

Nonetheless, as it looks now there most definitely is quality potential across portions of IA/MO/IL, and possibly some adjacent areas as well.

[andyhb]

HRRR solutions later are likely going to be pretty nuts if the 3 km NAM is already this aggressive across the warm sector (with supercellular storm modes).

[SchaumburgStormer]

2 hours ago, Malacka11 said:

@A-L-E-K @Chicago Storm Would you chase this? Assuming making the drive over to Iowa isn't an issue?

I had previously taken the week off (kids on spring break), but I will probably stay hyperlocal and let the storms come to me. Not much margin for error if you target the wrong spot with 50+ mph storm motions. 

[Malacka11]

1 minute ago, SchaumburgStormer said:

I had previously taken the week off (kids on spring break), but I will probably stay hyperlocal and let the storms come to me. Not much margin for error if you target the wrong spot with 50+ mph storm motions. 

That's what I'm saying. I have a decent amount of stuff in the books for Friday and while I could reschedule all of it to make room for a full day trip to Iowa or WC IL, I'm really not sure I want to do that for the reasons you mentioned. My other option is to be free by 2 and then see if anything remains more discrete in nature in the vicinity but I am currently under the impression that the chance of that is much lower.

[IWXwx]

7 minutes ago, Malacka11 said:

That's what I'm saying. I have a decent amount of stuff in the books for Friday and while I could reschedule all of it to make room for a full day trip to Iowa or WC IL, I'm really not sure I want to do that for the reasons you mentioned. My other option is to be free by 2 and then see if anything remains more discrete in nature in the vicinity but I am currently under the impression that the chance of that is much lower.

I'd vote for option 2 and let 'em come to you. (Well, maybe a short trip just to get into a good position based on radar so you can wave at them as they scream by.)

[andyhb]

Come on, seriously now. You just don't see output like that from the 3 km NAM.