03/30/05 FCST: Upper Midwest / Great Lakes

[Mike Hollingshead]

http://www.wxcaster2.com/CENTRAL_MESO-ETA_...NDSBLI_00HR.gif

http://www.rap.ucar.edu/weather/surface/sfc_ict.gif

It is amazing how bad the models handle the sfc winds. It can't even initialize them right. They've been backed ahead of the sfc low all afternoon. Yet the 18z eta initialized them as shown above.


http://www.wxcaster2.com/CENTRAL_MESO-ETA_...NDSBLI_24HR.gif

Backed winds ahead of that sfc low would make a hell of a difference tomorrow.

 

[Jeremy Lemanski]

FWIW, the points in eastern ok. are in the mid to upper 50s mostly, so there appers to be some moisture return, but as for the amount we can only wait and see. If there is a good return and points can get to around 60 give or take a degree watch out

As for chase areas, its a lose-lose type of setup for me. A faster moving storm will mean storms firing further east, but also less time for moisture to return and thus less coverage of the storms, poss. none at all? A slower moving storm means more moisture, better chance at severe storms, but also the storms would be further west and would weaken by the time they get within my very limited chase range for tomorrow.

 

[Robert Dewey]

NAM still on track with the slowing trend... Approx. 6 hours slower than the 12Z run. I really wish this thing would speed up some - As I'm not chasing half-way across the country on such a low risk. Instability still remains, decent even up until 12Z THU through the Great Lakes region, which would likely support a strongly forced squall line. Helicity values are also pretty impressive through 12Z as well.

All in all, IN/MI appear to have the threat for a squall line, most likely between 0Z and 6Z (from far western IN to far eastern MI, respectively) - Probably broken and strongly forced. I'm really diggin' the 100knt 500mb speed max moving in from the WSW combined with ESE SFC winds (which could be a moisture killer for OH/far eastern MI). The 500mb jet will likely enhance damaging wind potential...

Best supercell and tornado potential still appears to be central IL, possible extending into the far western reaches of IN, even with the slowing trend. The center of the low is located in southern IA/WI, so they are under a "lull" in the low/mid level kinematics - causing a significant drop-off in helicity. I would put my target area in central IL, just east of the IA border, where initiation will probably occur (should it occur at all)... Upper level winds will be increasing through the day, hitting nearly 80knts at 500mb... So you better have your racing gear ready...

I really wish COD would start working, so I have more fields then just the basic 5 maps...

 

[rdale]

I just don't see anything that would get storms going in MI during the day - and anything at night won't have the instability needed.

 

[Robert Dewey]

I just don't see anything that would get storms going in MI during the day - and anything at night won't have the instability needed.

Well, if the NAM had it's way, it maintains LI down to -4C and CAPES between 1000J/KG-1500J/KG (via COD) through 12Z THU. Forcing is strongest at 500mb, as shown on the VV fields. Looking at RelH fields, the NAM appears to develop a nice dry slot around 6Z across MI, with a nice band of higher RelH's just to the east... Which may indicate that the model is developing some sort of convection. Maybe severe, maybe not... But I do agree that it would be pretty hard since a tight inversion may develop just off the SFC. Ever since December 6th (1999 I believe), I never ignore very strong low level jets, even when it looks like a strong inversion may be in place... SFC temps during that event were in the mid 40's... I can't imagine any instability being present in such an environment.

 

[Mikel Shively]

looks like all the parameters are coming together today for a possible outbreak in IL, and IN. With Dewpoints >55 as far north as Keokuk, IA, looks like moisture return during the day will be no problem. Also the Wind fields appear to be great. IF I were to chase today, I would make a initial target of the Quad Cities, but that might have to be changed eastward as the day progresses and local conditions warrant. Sadly to say, I highly doubt I will be able to chase today So to those that do, Bag one for me! I think you will have good luck!

 

[Ben Cotton]

I'm actually a bit suprised to see the 1300Z SWODY1 still MDT. The current Tds are lower than I would like, but there's still time. I'm going to stick with my current target of BMI. I plan on leaving around 11am (skipping Dynamics and Political Science for this), so I might end up with a lot of time to kill. If that's the case, I'll find a free wifi location and check back in.

From the 6Z NAM, I can see the reasoning for the shift in the tornado outlook. More SRH would be nice, but I think there's enough to work with, assuming sufficient low-level moisture. Otherwise, things still look to be in good shape. This might be another of those good-setup-busts. We shall see.

 

[Robert Dewey]

I would still say the best threat is in central IL, somewhat near the IA border, as depicted here: http://www.waveformpc.com/outlook.JPG

WV loop shows a strong dry punch slowly working through central MO as of 14Z, which may help get things going a little later today. RUC advects Td's of 55F into southern IL by 21Z (60F on the NAM)... This will result in SFC based CAPE of 1000J/KG or 1500J/KG, with LI down to -5C. At the same time, the 500mb jet max will be entering the region from the southwest, while SFC winds remain SSE. Speed shear is quite impressive for 0-3KM and 0-6KM, and directional is decent. Helicity (0-3KM) reaches 200-300m2/s2 all the way into central IL at 21Z, increasing the further east you go, as winds will be more backed. Forcing doesn't actually appear to be all that strong in the beginning, so supercells definately a possibility before shear allows things to evolve into short lines, or a single "broken" line. Instability and shear persist well into the night time, remaining around 1000J/KG... So any linear stuff should persist well into the night across IN/MI and possibly northwest OH. The 700mb jet really starts cranking by 6Z, at 60-70knts, so I could very well imagine a low topped and/or thunderless line persisting.

I am somewhat concerned about moisture, NAM returns things very fast, so it's kind of suspect, but, 14Z SFC obs do indicate Td's as high as 57F already in southern IL, and a very narrow toungue of +54/55F Td's extending through MO, getting ready to head into IL - The one hour RUC forecast (valid 14Z) is quite low with these readings, only showing upper 40's across those areas.

RUC initiates convection around 21Z near the red "target" area, which is where I think the greatest potential for any tornadic activity will be. This also coincides with the dry slot moving through... Given the speed of winds aloft, these storms will be moving fast, possibly in excess of 50mph.

 

[Glen Romine]

Morning soundings revealing a far better than expected environment. Topeka sounding in particular showed very little CIN and steep lapse rates through a good depth. Convection fired early this morning - and could be surface based by late morning. Near the sfc low, the deep shear may be weak enough to slow the motion of storms to chaseable speeds, but will hopefully be adequate to suppport storm rotation. I'd be most interested in tracking ~ 75 miles SE of the surface low along weak trough axis. RUC maintains convergence along this most of the day. Further east - potential is less certain. Perhaps a better idea for that region's potential can be assessed later today.

Glen

 

[Bill Schintler]

Chase target for today, March 30

Chase Target:
Cedar Rapids, IA

Timing:
Storms will reach the area around 3 PM

Storm type:
Isolated severe winds to 70 mph. There is also a small possibility of a weak tornado although the tornado threat is small today.

Discussion:
A strong surface and upper level system tracking west to east through IA, and an associated front/trough will serve as the focus for severe weather today. Ongoing convection in SW IA will continue to develop to the east through the early afternoon. An E/W oriented boundary was noted on visible satellite at 15:30Z, while the front/trough in SW IA and WRN MO was surging to the east. Expect the triple point to line up in East Central IA by 21Z. MLCAPE’s to 1000 J/kg, coupled with BL-6km shear values of 50 kts and 0-3km SRH’s to 200 m^2/s^2 will create an environment favorable for severe weather.

- bill

 

[Jeremy Lemanski]

Dewpoints are now near 60 across southern ill. with temps near 70 in full sun. This could be one of those sneaky type outbreaks with mini sups.

Cent. and southern ill. looks to be the best place to target for tornadic storms before everything forms a squall line and races NE