Convective Addiction

FCST: 05/12/10 – KS/MO/IL

Posted on 11. May, 2010 by Jesse in Forecasts, Uncategorized

Continuing the active weather pattern, Wednesday has the potential to bring another round of severe weather to the Midwest.  The noxious trough that has been responsible for the past few days of active weather on the Plains will start to eject eastward towards the Great Lakes on Wednesday.  With the ejection of the trough, a low pressure system will move into the Kansas City area by midday Wednesday.  A coterminous warm front will be draped across the Missouri Valley, extending roughly along the U.S. 36 corridor from St. Joseph, MO to near Springfield, IL.

While both the NAM and the GFS are fairly harmonious in regards to the position of the warm front (per the 12z run on Tuesday), the GFS is a soupcon south of NAM in it’s placement of the frontal boundary at 21z on Wednesday.  Per the surface maps shown below, the triple point is progged to move across northern Kansas, and should eventually reach the KC/Cameron area by 00z.

GFS MSLP - 21z Wednesday

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WRF MSLP 21z Wednesday

An 850 mb LLJ axis will allow a patulous advection of rich Gulf moisture into the region ahead of the surface cold front.  The WRF projection for 21z Wednesday is shown below.

WRF - 850 mb Heights/RH at 21z Wednesday

While not as robust as Monday’s setup, the upper air dynamics will promote storm top divergence, allowing for a greater likelihood that supercell updraft and downdraft regions will be segregated, yielding a potential for more obstinate, discrete storm modes.  Less vigorous mid and upper-level winds (see images below) will promote more tolerable storm motions on the order of 25-35 kts.

WRF - 250 mb winds at 21z Wednesday

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WRF - 500 mb winds at 21z Wednesday

As often is the case in these areas, the efficacious removal of any remnant overnight convection will be critical for promoting a more favorable thermodynamic environment in which any potential supercells might be embellished on Wednesday afternoon.  Obviously the progged SBCAPE values will be dependent on any heating that takes place throughout the day on Wednesday, so should overcast conditions prevail, forecast instability parameters will be lessened, thus minimizing or effectively squelching the SVR threat until the arrival of the cold front.

SBCAPE at 21z Wednesday per the WRF

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700 MB Relative Humidity at 21z Wednesday

While 700 mb temperatures will be increasing throughout the day Wednesday, due to a more studious EML advecting into the region, if storms do develop in the warm sector they should be isolated or scattered in nature.

700 mb Temps at 00z Thursday

Although upper-level dynamics are not overly vivacious, low-level hodographs will enhance the ability of storms to become tornadic in the vicinity of the warm front, should any storms develop in the warm sector and interact with the frontal boundary.

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LI values at 21z Wednesday per the WRF

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K Index at 21z Wednesday per the WRF

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SREF Significant TOR Ingredients - 00z Thursday

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Columbia, MO SKEW-T (WRF) at 00z Wednesday

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Quincy, IL SKEW-T (WRF) at 00z Wednesday

The bottom line:  Wednesday is another day that holds some hidden potential to produce classic Spring severe weather in the vicinity of existing frontal boundaries in or near the warm sector of a vernal cyclone.  However, this will definitely be a day where interested parties will want to pay particularly close attention to mesoscale features early in the day, focusing specifically on the location of the warm front, along with the juxtapostion of any SBCAPE and of course any potentially remnant OFBs from overnight crapvection.

Jesse Risley and Ryan Wichman