Sunday, April 3, 2011

Severe Weather - Round 1 - Today

The above image shows the latest Severe Weather Outlook from the SPC for this afternoon and tonight.  Severe storms are possible anywhere within the area outlined in green (click image to enlarge).  The highest risk of severe storms is forecast within the area outlined in red, which includes the Kansas City Metro area.

Very large hail (i.e., tennis ball size or larger) and tornadoes are likely with the most intense storms this afternoon and evening.  While most any severe storm that forms will be capable of producing a tornado, an enhanced risk will take place within the area outlined in bright green on the image below (which includes Emporia, KS, the Kansas City Metro area, Columbia, MO and eventually the Chicago area).  An even greater risk will be within the area outlined in yellow (which includes the Peoria and Quincy, IL areas):

The greatest risk of very large (i.e., tennis ball or larger) hail will take place within the area outlined in yellow on the image below.  An even greater risk exists within the area outlined in red:

Damaging straight line winds are also possible with any severe storm that forms.  The greatest risk will be within the area outlined in bright orange on the image below (an enhanced risk of damaging winds will exist within the region outlined in darker orange):

Residents of the severe weather threat areas, particularly from the Emporia, Kansas area on into the KC Metro and northwest Illinois, should remain on high alert this afternoon and evening.  Listen to your best local weather source for later statements, watches and possible warnings.

The remainder of this post will discuss the meteorological factors that are expected to come into play to produce this severe weather situation later today.

A very strong disturbance in the upper-atmosphere is currently located over the central and northern Rockies (shown generally within the yellow circled area on the latest water vapor satellite image below):

As indicated by the red arrow on the same image, the system will continue to generally move and develop/expand toward the East/Southeast today and tonight.  Energy from this developing disturbance will begin to overspread the severe weather threat areas by mid to late afternoon today, and increase into the evening hours.

Below is an image showing the latest surface weather features as forecast for 4pm CDT this afternoon.  The computer model that produced this image is called the RUC (or Rapid Update Cycle) model.  A cold front (dark blue line) and dryline (brighter yellow line) will be advancing Southeast and Eastward (respectively) into the severe weather threat areas this afternoon:

At the same time, warm and moist air will continue surging Northward into the threat area from the Gulf of Mexico.  As that airmass heats and destabilizes and as the upper-level energy begins to overrun the area into the mid to late afternoon hours, thunderstorm development will begin.

Initially, the most likely area for development appears to be along and ahead of the cold front near the low pressure center over eastern Iowa and northern Missouri.  Development will then take place southward into Eastern Kansas over time.  All of this activity will then move and develop Eastward.

Thunderstorm development is less certain (during daylight hours) from the surface low/cold front/dryline intersection in extreme southern Kansas, southward into Oklahoma and northwest Texas.  This is due to a strong capping inversion that is forecast to remain in place across this region.

The cap will be weaker across Eastern Oklahoma, and current thinking is that thunderstorm development won't occur along the Oklahoma portion of the dryline until it moves East into this region later this evening and/or tonight.  If, however, an isolated storm is able to break the cap and develop along the dryline earlier in the evening or late this afternoon across western or central Oklahoma, it would rapidly become severe due to the strong instability that will be present.

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