severe wx update/forecast

[WXBUFFJIM]

Looking ahead through this weekend, It's expected to be an active time period as far as severe weather is concerned in the midwestern United States. The main threats today are large hail and damaging winds. However an isolated tornado is possible if storms interact with the warm front today. On Sunday, a more widespread and significant severe weather event could potentially occur with possible tornadoes and widespread very damaging winds as well as large hail. Significant severe weather is possible on Sunday and thus a higher probability severe weather threat is likely to occur on Sunday across portions of the upper midwest.

Taking a look at today reveals a severe weather threat, most likely starting across Iowa later in today as a warm front, which is situated from the Great Lakes into the Upper Mississippi Valley now is expected to move north ahead of a developing cyclogenesis across the north central Plain States. At the same time that's happening, a western U.S. shortwave trough will eject northeastward into the south central Rockies.

Severe thunderstorms are expected to inititate later today across eastern Nebraska, eastern South Dakota and across most of Iowa as the warm front slolwly moves north, the cyclogenesis ejects east, and the low level jet intensifies enhancing the severe threat. The main threat early in the convective period later this afternoon will be very large hail. Later this evening, damaging winds could potentially become the main threat as storms are expected to congeal into a mesoscale convective system. The area where damaging winds could occur maybe across southern Mnnesota, parts of Iowa and into Wisconsin as the evening progresses. An isolated tornado is possible in the midwest today as well, especially in areas where storms interact with the warm front. Further east into the Great Lakes region and Ohio Valley, isolated strong to severe storms could develop later on today into tonight as a warm front and several outflow boundaries will be in the vicinity. The main threats will be isolated large hail and isolated wind damage through mid evening.

There is also another area across the Oklahoma and Texas Panhandle where storms could go severe later today. These storms will develop along the dryline as instability increases. At the same time, the shortwave trough in the west now will track further east. Hail and damaging winds are the main threats in the OK/TX Panhandles later today into this evening.

One feature of interest on Sunday will be the evolution of the shortwave trough, which is now over California. This trough is expected to track toward the central and southern Rockies later today and across the north central Plains and upper Mississippi Valley on Sunday. Preceeding this shortwave trough will be a cyclogenesis across the upper midwest. Surface low pressure is expected to be centered over the Minnesota, South Dakota, Iowa, and Nebraska border on Sunday afternoon. Showers and thunderstorms are expected to develop throughout the day Sunday, especially across Minnesota, Wisconsin, northern Iowa and into eastern South Dakota and eastern Nebraska as well. Atmospheric instability and shear combined are favorable for supercells, especially along the warm front across Minnesota and Wisconsin during the afternoon. The main threats will be very large hail and possibly widespread damaging winds as well as a few tornadoes.

Further south, theere could be a deep/dry boundary layer, which could preclude a warm sector tornado threat. However severe thunderstorms are possible along the dryline later Sunday across the central Plains from Manhattan, KS, Topeka, KS northward through southwestern Iowa as moderate instability is expected. Any storms that form in this area will likely be supercells. The main problem this far south is the fact there is a capped warm sector east of the dryline. Thus severe weather should be limited to isolated severe only across southwestn Iowa, and east central kansas. The main threats with these storms if they do develop will be large hail and damaging wind.


A very active weekend coming up, especially in the midwest.

Jim

[rainstorm]

thanks for the update

[Wnghs2007]

Yeah thanks for the update...looks to be getting active for the mid-west...

[WXBUFFJIM]

http://radar.weather.gov/radar/latest/D ... kmpx.shtml

First storms maybe firing in northern iowa as we speak. Storms could intensify explosively in the next hour or two as the cap weakens and the low level jet strengthens from the south. These storms will be mostly elevated and high based. But with extreme shear in place, cannot rule out a tornado during the beginning evolution of this. Large hail is the primary threat with baseball sized hail possible and 70 mph gusts this evening after sunset for northern Iowa and southern Minnesota.

A more serious situation could be developing on Sunday. In the meantime, expect a severe weather watch to be posted shortly from the SPC if further development occurs on the doppler radar as you see from that link above.

Jim