2013-05-28 FCST: NE, KS, OK, E TX PHNDL

[Mike Smith]

Tuesday looks like a "day before the day" setup to me.

While SPC has multiple states in the SLGT risk, they also have a 30% area on roughly a LNK to PPA axis. If it were me, this area would be hatched and with an east boundary of OMA - MHK - ICT - END to PPA where it would join the west boundary as drawn.

Zero to 1km EHI's are forecast to be near 5 in Kansas with more than 2,500 j of CAPE. In some ways, this reminds of of last Saturday through Monday where this would be day one.

I'm very surprised at SPC's limited outlook for Wednesday. This looks like it is a high risk day to me.

 

[Brian McKibben]

Tuesday through Thursday looks interesting. The winds are there in all levels. I haven't checked any forecast soundings, but the NAM and GFS are both showing a 50kt+ LLJ across the plains. Wed looks really good with the winds, but that is for another thread for 5/29. I anticipate the risk for Tuesday to be expanded in subsequent outlooks.

Tue has impressive thermo as well with very unstable airmass (3000-4000j/kg). 45kt LLJ at 00z increases to 60kt at 03z. It is interesting to see the NAM with precip along the DL starting around 18z near OK/TX border.

This could become an active few days.

Are we going to have capping issues?

 

[Jeff Duda]

Tuesday through Thursday looks interesting. The winds are there in all levels. I haven't checked any forecast soundings, but the NAM and GFS are both showing a 50kt+ LLJ across the plains. Wed looks really good with the winds, but that is for another thread for 5/29. I anticipate the risk for Tuesday to be expanded in subsequent outlooks.

Tue has impressive thermo as well with very unstable airmass (3000-4000j/kg). 45kt LLJ at 00z increases to 60kt at 03z. It is interesting to see the NAM with precip along the DL starting around 18z near OK/TX border.

This could become an active few days.

Are we going to have capping issues?

Keep in mind that the current Day 3 CO was issued at about 2 AM, so they weren't looking at 12Z model data. Also, I think there is a bit of uncertainty as to the type and location of the boundary that will provide for forcing as well as the degree of capping and shear. It looks like there will certainly be a great amount of instability (CAPE up to 4000) but the GFS shows shear will be aligned almost parallel to the forcing boundary (looks like a SW-NE oriented dryline with bulges) and not all that strong in magnitude. The NAM shows more of a warm front arcing across NW KS with better directional shear, although little speed shear. The SREF is more in line with the NAM, although it really doesn't give the setup much respect in terms of shear. Quite a robust LLJ is forecast to develop from all models especially after 00Z, but if storms haven't formed by about then, it's unlikely surface based development would commence after 00Z. Elevated supercells may end up being the story north of the front.

Given the uncertainties mentioned above, I would have a hard time justifying a high risk at this point. Things should clear up over the next 12-36 hours, though.

 

[Mike Smith]

The more I look at Tuesday, the more convinced I am that it will be a big day in Kansas and Oklahoma. I don't have any concerns, based on current models, about shear. Per the 12Z NCEP WRF 4km, there will be a surface boundary that will move from around the I-70 in the morning to the US 54/400 area in the afternoon/evening. That should back surface winds nicely (exactly the same thing happened in Greensburg).

Here is the 18Z NAM's forecast for 21Z Tuesday for 850 and 500mb winds.


And, for 00Z (7pm Tuesday):


And, the 0-1km EHI at 7pm Tuesday.


Again, I think Tuesday is the "day before the day" type setup-up. Within the area I outlined at the top of this thread, I don't have a particular area where I thinking convective initiation will occur -- too soon. But, I do think that significant tornadoes as well as very large hail are possible from supercells.

 

[Jeff Duda]

The more I look at Tuesday, the more convinced I am that it will be a big day in Kansas and Oklahoma. I don't have any concerns, based on current models, about shear. Per the 12Z NSSL 4km, there will be a surface boundary that will move from around the I-70 in the morning to the US 54/400 area in the afternoon/evening. That should back surface winds nicely (exactly the same thing happened in Greensburg).

Where are you getting such data? The NSSL 4km WRF only goes out 36 hours, which, as of this morning, would be 00Z on Tuesday (i.e., 7 PM on Monday). That's 24 hours before this day.

 

[Mike Smith]

Jeff, you are correct..thank you. I've corrected my posting.

 

[Brian McKibben]

Forecast sounding for Alva at 00z (per 00z 20120527 GFS). Is this sounding depicting a storm right over Avk?

 

[Jeff Duda]

Probably. Check the accumulated precip field at that time.

 

[Adam Adkins]

The 00z NAM is showing very healthy parameters around the NW and far W Kansas, SW Nebraska, and E Colorado area. Latest 00z NAM and RAP models generally move things west a bit with higher dpts into far eastern Colorado and the other mentioned areas. Bulk shear exceeding 50kts along with helicity values over 350 and 3500 J/kg CAPE all in this region at 6PM. No appreciable cap. Bases should be low enough as well with dewpoints around 60 degrees at the CO border. Shaping up to be a more organized day then the past few right in the heart of "Hail Alley".

 

[chrisbray]

Can we add Illinois to the thread? May be an opportunity for a backyard chase today in Northeast Illinois. While there won't be many triggeres other than outflow boundaries, models are showing around 2000 cape, 3km EHIs from 3-5, bulk shear 35-50 knots in the late afternoon. If anything does fire locally from about 1pm - 6pm I will try to chase.

 

[BBauer]

Nice hook on storm just south of Seneca, KS.