Tuesday, June 3, 2008

Thunderstorms & More Thunderstorms

As you can tell by the title, those thunderstorms are not going to stop. During the overnight hours, a fairly weak wave of energy moved across the plains states allowing for thunderstorm development. As the storms continued to move across the state of Iowa, a bowing line of thunderstorms became evident across central Iowa. This bowing line of storms continue to move through the remainder of the the state, affecting mainly southeast Iowa during the morning hours as well. Reports throughout the night had mainly damaging winds involved with this line of storms, although a few hail reports were received near LeMars, IA and then again around the Des Moines metro, and its' surrounding. These storms have since moved out of the state, however, still posing a severe weather threat for parts of Illinois, and should continue to do so for the remainder of the day.

Back to the forecast, the risk for severe weather across the state of Iowa is nearly a guarantee for both Wednesday and Thursday. Currently both days are still highly variable when it comes to model consistency, so the area of most concern is hard to define even for tomorrow. Currently it is believed that a warm front will extend east/northeast from a low in northern Kansas. This warm front will set the stage for thunderstorm development during the afternoon hours, potentially closer to the low as a substantial capping may be in place over the remainder of the warm sector. With developing storms likely in central/eastern Nebraska, shear values remain substantial to warrant a belief of supercells capable of both very large hail and tornadoes. As the thunderstorms move into areas along the Missouri River and into Iowa during the evening and early overnight, cooling should take place at mid-levels to allow continued development and growth of thunderstorms. A large complex of storms (MCS) is likely to travel across the state, capable of large hail and damaging winds. Currently, the best threat for this MCS should be over the southern half of the state, however, given current model inconsistencies this area is not well guaranteed. Later SPC outlooks within an hour, as well as tomorrows' early outlooks should be able to have a better handle on this storm system and I will update accordingly.

Thursday's setup looks even more favorable for significant severe weather across much of the state of Iowa, and other areas in the plains. The low pressure system should be situated in eastern South Dakota at the surface, with associated warm front across central Minnesota. A cold front and dryline will be located south of the low, draped across extreme eastern South Dakota and Nebraska, as well as central Kansas, Oklahoma, and even northern Texas. Substantial capping may be present to the areas south of I80, making thunderstorm development questionable through the evening hours. North of there however, expect significant instability and lift to allow thunderstorm development along and just ahead of the cold front and dryline. These thunderstorms are forecasted to have significant moisture and lift, combined with moderate to strong shear values. Indicating that supercells capable of very large hail, damaging winds, and tornadoes are likely. This threat covers a vast majority of the state at this time, later outlooks and forecasts should be able to better define an area of enhanced severe weather with upgrades in risk category via the SPC are likely. Once again, updates on this situation will be posted as warranted...

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