5/21/04 FCST: Upper midwest - Great Lakes - High Plains

[Kevin Scharfenberg]

Didn't see a 5/21 fcst thread, so here goes...

I see two disparate areas of interest today.

First, along the warm front from southeast SD across far northern IA into far southern WI. This area will be north of the strongest cap, and the low level jet will be impinging on the front for widespread inititation as occurred in the same area yesterday.

The second area (and my focus here) will be along the dryline, which should stay on high-enough terrain to break the cap again today, generally near a LBF-GLD-DHT-ROW axis. Today, the flow aloft has improved a little along the length of the dryline, with 0-6 km shear of 35-40 kts progged.

I'm still not convinced about the south-central Nebraska area target, due to the strong residual capping inversion and lack of a sufficiently-strong near-surface boundary, though any storms developing back around LBF/GLD would threaten that area later (probably after dark).

The key negative along the dryline would be high cloud bases, but structure should be good, much like what the Fort Morgan storm provided Thursday. The strongest shear appears progged to develop over the DHT/GUY/SPD part of the dryline, so I will focus my attention on that region.

Sitting in Norman, the warm front storms are 10+ hours away and would probably not be worth the effort anyway. The nearest dryline storms would be 4+ hours away, which might be more playable for a 11am-noon departure.

 

[David Draun]

I looked at the froecast soundings for Chicago today. We have low convective initiation temperatures early (around 65F) They will rise this afternoon. (around 86F) Although there is a another spike in 100mb CAPE values (2700 J/kg), a strong cap will be in place along with high inhibition values. LCL's are low, but LFC's are above 10,000 ft for much of the day. Let me just say I'm confused about SPC's higher tornado risk bulls-eye over this area. I don't see another explosive convection day today, but we can only hope. :wink:

 

[Robert Dewey]

Originally posted by David Draun
I looked at the froecast soundings for Chicago today. We have low convective initiation temperatures early (around 65F) They will rise this afternoon. (around 86F) Although there is a another spike in 100mb CAPE values (2700 J/kg), a strong cap will be in place along with high inhibition values. LCL's are low, but LFC's are above 10,000 ft for much of the day. Let me just say I'm confused about SPC's higher tornado risk bulls-eye over this area. I don't see another explosive convection day today, but we can only hope. :wink:

I think SPC is playing warm front situations safely, ever since the bust you guys had a few weeks back...

SPC -

BEST SUPERCELL POTENTIAL AND GREATEST TORNADO PROBABILITIES SHOULD E
INVOF WARM FRONT -- AND AWAY FROM LARGE CONVECTIVE CLUSTERS -- WHERE
SHEAR/LIFT/VORTICITY ARE MAXIMIZED. MODIFIED MODEL SOUNDINGS OVER
NRN IL AND MI/INDIANA BORDER REGION BY 21Z SHOW LARGE 0-3 KM AGL
HODOGRAPHS WITH 250-400 J/KG 0-3 KM SRH...AND 45-55 KT 0-6 KM SHEAR.

Robert

 

[Angie Norris]

Sitting here in beautiful downtown Norman considering a little trip north today to the Dodge City area. The cap concerns me, but the highs are progged to be just high enough to maybe allow initation. The surface low may be of some help, as will the dry line. Doesn't look tornadic, but stucture and maybe some hail would be worth it!!

Angie

 

[Joel Wright]

A very powerful outflow boundary shows up nicely in IA and IL. I woke up to strong northeast winds and temps in the 50's, while just to the south there's full sun and with 80/72 type readings being reported. Some nice new convection in the northwest tip of IA may end up following this strong reenforced boundary across central IA into northern IL later today. This could become a strong derecho event. With backed winds along the boundary I wouldn't rule out a tornado. The question is, will the storms in NW IA maintain their intensity?

 

[Mike Hollingshead]

I'd keep an eye on the outflow bondary in central NE. You can see it on LBF's radar, hopefully it'll show up on satellite sometime early afternoon.

http://weather.cod.edu/analysis/paulradar.pl?LNX

Mike

 

[David Draun]

A severe thunderstorm with damaging winds and violent CG's just BLASTED through my area at 60 mph! :shock: All this while temperatures are in the chilly lower 50's. New WW to my NW until 4:00 PM. Here we go again. :wink:

I think SPC is playing warm front situations safely, ever since the bust you guys had a few weeks back...

Are you referring to the tornado outbreak on 4/20?

 

[Mike Hollingshead]

I'd really really watch nc NE into SD along that boundary and warmfront. Check out this mid-level dry punch....BAM.

http://weather.cod.edu/forecast/loop.rucus500rh.html

http://weather.cod.edu/forecast/RUC/rucUS_...S_0_cape_12.gif

Mike

 

[Kevin Scharfenberg]

Well, it looks like work-duties are keeping me in Norman today.

Still looks like two distinct risk areas, first along the front from northern NE eastward into the Great Lakes states. Probably a lot of wind and hail reports over a large area in store. The second risk along the high plains from central SD down into western KS, the panhandles and SE NM. The second area will be prone to more isolated supercells due to the stronger cap, but LCLs will be quite high so more of a downburst threat than a tornado risk.

 

[David Draun]

NWS Chicago has LOCALLY upgraded the risk of severe weather to MODERATE, with mention of tornadic supercells rooting on the warm front, mainly west of I39 until after 2pm. It's still cold too. Valparaiso, IN has just CRASHED from 72F to 54F as the severe squall line turned winds off the lake. Our forecasted high temp has just been reduced to 70F at best.


edit: SPC has now upgraded the risk to MDT and expanded the 5% tornado potential. Hail/Wind probabilities are up to 35% Maybe you should chase here today. There will be a lot of grunge though.

 

[Dan Robinson]

We are checking data at the North Platte library now. Cu field to the east, not socked in with clouds today either. T/Td spread is improving. We are also impressed with what appears to be a mesolow from last night's convection moving across NE. All in all it looks like a good chase day in western NE.

Will probably target somewhere north or northeast of North Platte initially.