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| News - Snow | |||
| Written by Reed Patrick Timmer | |||
| Wednesday, 21 November 2007 10:11 | |||
A snowstorm will be likely from the northern MS River Valley through the Great Lakes Region this evening through Thanksgiving Day, as a low pressure center gradually strengthens along a strong baroclinic zone stretching across the central U.S. 3-6 inches of snow will be common, especially across southern WI, southern and central MI, and southeast Ontario by Thursday afternoon. The national radar loop from Wednesday afternoon is shown below, with the deformation zone (wrap-around) precip clearly evident across Iowa. Loops of WRF forecast MSLP and surface temperature from Wednesday afternoon through Thursday morning are provided below, with the surface baroclinic zone clearly evident from Michigan southwest to Oklahoma. Cyclogenesis is currently underway across the Southern Plains, with a slowly strengthening low pressure system moving from Northeast OK into MO at this time. As an upper-level trough impinges on the Plains, this low-pressure system will intensify and move northeastward towards the Ohio Valley by tonight. As the cold front continues to move southward, the rain currently over the Great Lakes Region will change over to snow by this evening. Given slantwise convective instability in place, there will be substantial mesoscale banding within the deformation zone precipitation, thus some locations will receive heavy snow tonight across southern WI, central MI, and southeast Ontario.   Based on the WRF forecast precip for Thursday night, a broad area of 3-6 inches will fall across most of the central and northern Great Lakes Region, with the higher amounts falling where mesoscale bands can remain over the same areas. I'm currently located in Grand Rapids, MI, where a snow advisory is in effect tonight. I'll be documenting this event from start to finish, and will post video updates as the heavy snow commences. Stay tuned for updates!  Severe weather and even isolated tornadoes will be possible over the warm sector in eastern AR this afternoon/evening, despite rather limited instability. Shown below are the WRF forecast CAPE and 850 mb flow valid at 00z this evening. As can be seen below, a strong low-level jet will be in place across the entire warm sector, with 30+ knots superimposed in an uncapped environment. The only limiting factor will be marginal instability, with surface-based CAPE values of <750 J/kg from the Gulf Coast north to eastern AR.
  The Storm Prediction Center has issued an MD for most of Arkansas, as surface-based convective initiation is expected soon! Stay tuned for updates on the developing severe weather situation as well! A lot of meteorology today. 
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