Thursday, June 16, 2011

Two chances for thunderstorms, then even more heat

The Mid-South will have a couple of chances of thunderstorms over the next 12 hours or so, then a ridge of high pressure builds, bringing oppressive heat to the area for Father's Day weekend.

The first of a couple of thunderstorm chances is developing now.  At 1:45pm, StormView Radar is showing a few cells already popping over eastern AR and northwest MS.  These cells should continue to develop as a stationary front lies just about over the metro area and temperatures in the 90s and dewpoints in the 70s contribute to a very moist and unstable atmosphere.

Earlier today, a thunderstorm complex fell apart over the Ozarks of northwest AR, but a mini-low pressure system (mesoscale convective vortex) remains and is moving towards the region along the stationary front. This MCV will be the catalyst for scattered thunderstorms.  The image below shows the swirl of clouds over NW AR representing the MCV and the available energy in the region for thunderstorms (yellow lines). Basically, the MCV is moving into an area of high available energy, which should be enough to trigger storms during peak heating hours.  The region is under a SLIGHT RISK for severe weather again today, with high wind possible, as well as large hail.

A vortex generated by dying storms to our west will encounter available convective energy this afternoon

These storms should weaken and move out this evening, but high-resolution model data indicate that another upper-level low will move along the front from southeast MO into the Mid-South, bringing another possible thunderstorm complex during the overnight hours.  Even the traditional models are now coming on board with this solution, so don't be surprised to hear more thunder overnight.  The model output below indicates the distinct possibility of storms somewhere around midnight.

High-res model data showing the likelihood of additional storms overnight
After the stationary/warm front moves north of the region by tomorrow, aided by a building ridge of high pressure, heat and humidity continue to build into the Father's Day weekend. In fact, the string of 90s will continue into next week, with 100 possible Sunday as the ridge peaks over the region. A pattern change looks to be forthcoming by the middle of next week, which could bring more cloudiness (and somewhat cooler temps) as well as higher rain chances.  Details are available in the MWN Forecast.

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