8/9/2004 FCST: MIDWEST/GREAT LAKES/NORTHERN OHIO VALLEY

[Robert Dewey]

Threat still looks decent...

Unmodified 12Z ETA soundings for 03Z TUE at LAN does indicate some good low level directional shear, but this looks more like a bow echo sounding than tornado... Typically, tornado soundings would yield good directioanl shear all the way through the 0-6KM layer (usually)... Where-as bow echoes usually have the best directional shear located in the 0-3KM layer, with little directional shear above that. Still, supercells often develop in these environments, then transition/morph into bow echoes.

The sounding also shows CAPE values of 2000J/KK, which would definately support severe thunderstorms...

 

[Jeremy Lemanski]

latest SPC outlook added 5% tornado area in eastern U.P and NW lower.

 

[rdale]

That's closer to the track of the upper-level system which is where yesterday's tornadoes were associated.

 

[Robert Dewey]

Dewpoints seem to be rising nicely across the region... OBS already show low to mid 60's across lower MI, with mid to upper 60's across WI. The moisture across WI should advect into the region later on this afternoon...

15Z RUC is looking decent, though directional shear is not as good as the ETA was showing (helicity below 100m2/s2), speed shear is still good. Modified the LAN sounding for a parcel of 77F/64F at 00Z, which yields close to 2500J/KG...

 

[Geoff Boyle]

We got some action in Canada. Chasers in Nova Scotia are reporting isolated severe weather and funnel clouds. Environment Canada has only put some watches up, but it looks like things are going to develop pretty fast. Might want a NOW thread with Canada included.

 

[mikegeukes]

National Weather Service Grand Rapids in their latest HWO at 453 PM EDT still mentions:

AN ISOLATED TORNADO IS ALSO POSSIBLE.

Latest Hazardous Weather Outlooks:
http://kamala.cod.edu/offs/KDTX/0408092002.flus43.html -Detroit
http://kamala.cod.edu/offs/KGRR/0408092107.flus43.html -Grand Rapids
http://kamala.cod.edu/offs/KMKE/0408091941.flus43.html -Milwaukee

Mid Level Lapse Rates still around 6 deg C, last check on SPC site
http://www.spc.noaa.gov/exper/mesoanalysis...is/s1/laps.html

Mike