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10/5/05 FCST: MIDWEST / GREAT LAKES

WED looks pretty interesting across this region... Strong height falls, very strong frontal boundary, and decent low level moisture should all act together to produce a decent line of thunderstorms. Wind fields are decent, with the latest 18Z NAM showing >50KNTS at 850MB across the Great Lakes between 06Z and 12Z THU morning. Instability doesn't look significant (500J/KG in the 06Z to 12Z timeframe), but the forcing along the front should be enough to get things going. This event has all of the markings of a strongly forced, low topped, intense line of thunderstorms.
 
Waiting to see what the 00Z GFS has, but the NAM looks concerning. Main mode of convection still appears to be a low topped squall line situated right along, or perhaps just behind the front. NAM has 50-70KNTS in the 3K to 8K FT AGL layer combined with a LI of -3C all through WED night (good SFC moisture, with Td's in the low to mid 60's). Height falls are rather significant, and forcing along the cold front is rather intense (strongly baroclinic), so a band of thunderstorms should have no problem developing.

Again, if things panned out as the NAM shows, I would suspect a rather widespread wind damage event - perhaps with a thunderless line of convection. With the strength of the wind field and forcing involved, I doubt instability will play a major factor in deciding the severe weather threat. It will be very interesting to see how this plays out.
 
Chase target for October 5

Chase target:
Rhinelander, WI.

Timing:
Warm sector storm initiation 3 PM CDT.

Primary severe risk:
Winds below severe limits and heavy rains of 1â€￾-2â€￾ locally.

Discussion:
Seasonably strong fall system with attendant shallow ana CF is affecting the upper-Midwest today. 15Z SFC front extended along an HYR/RST/DSM line with extensive precipitation primarily behind this feature, while H85 front was 150mi behind from FFM to MJQ to AIO. Strong divergence is lifting ahead of 100kt streak in H3 trough. A significant limiting factor in severe weather today will be poor mid-level lapse rates in the 6C/km range, however the aforementioned upper-level forcing will partially make up for this. Best SVR potential will exist along and just N of WF along US-8 in WI, where MLCAPE’s of 500-1000J/kG will be juxtaposed with marginal shear parameters (0-3km SRH to 200m^2/s^2, and 0-6km shear of around 30kts). RUC appears to have initialized well to on-going precipitation as well as surface features, and it suggests storm initiation in the warm sector around 20Z.

- bill
 
This is turning into a significant non-event. As I had feared in the other thread (the 10/04/2005 thread), the system wound up too far west. The system deepened like I wanted it to, but once it closes off at 500MB west of the MS River (and occludes), you might as well forget the chances of anything significant further east.

Oh well, maybe a November bomb will surprise us Great Lakes folks.
 
The main threat now looks like, exists in the northern WI vicinity. The jet stream is right over that area, and there is an impressive Low Pressure System and Trough, in/near the area, where severe thunderstorms are possible. There have already been many storms going up along this boundary in OK/KS. If you look at GOES SAT, it will show a very deep cumulus field, some towering as well. There is about 1200 J/KG of MLCAPE, which would make for some potentially damaging winds, along with the moderate shear of about 38 knots. I think damaging wind is possible due to the strong veering/backing winds, but I am not sure about Hail, but if there were to be any, it would be along the extreme NE WI border. Supercells look extremely possible along NE WI, looking at the supercell indices...you might even see a small spin up along this area, but I doubt it...
 
This storm lacked the severe weather in the upper Mississippi Valley/Western Great Lakes area, but it did produce a fairly large amount of snow for the northern High Plains. For example, total snow accumulations of 22 inches were expected to be reached in the E MT county of Wibaux.....pronounced we-bow. The blizzard also prompted a civil emergency message to be issued by the Dawson county Disaster and Emergency Services telling people to only use water for emergencies as the storm had downed power lines in the area thus no power to the water plant for the time being. http://www.wrh.noaa.gov/warnings.php?wfo=g...GENCY%20MESSAGE

Pat

Sorry if this post is a little off for this board.
 
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