Friday, June 6, 2014

Convective system packs a punch Thursday - another today?

UPDATE - 11:00am
Temps are soaring in the metro and are well into the mid 80s with dewpoints (measure of low-level moisture) in the mid 70s. With cloud cover just to our north holding temperatures back in the 70s, a gradient of atmospheric instability (CAPE) has developed right over the metro. Why is this important? Convective complexes like the one moving into western AR now, tend to follow this gradient.

A storm complex (MCS) over western MO will likely move across areas with high atmospheric instability (CAPE - plotted above with red lines). The projected path of the MCS is shown with the red arrow. Memphis is the gold star.
With plenty of heating and available moisture already realized across central and southern AR into the metro and north MS, I expect the MCS thunderstorm complex in west AR to continue moving this way fairly quickly and reach the metro by mid-late afternoon, or maybe a couple hours later than yesterday's. The other difference from yesterday is that the strongest portion of the storm will likely be near and south of I-40 rather than north of I-40 (this does not discount north Shelby or Tipton County however).

Metro residents need to be prepared for storms possibly as strong as yesterday's (since we didn't get the brunt of that system) late this afternoon (after 3pm). The main threat will be high wind of 60+ mph, with a small threat of hail and a very low threat of a tornado. Before mid-afternoon, scattered strong storms with heavy rain, copious lightning, and gusty wind are possible anytime after noon to 1pm.

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A quick-hitting mesoscale convective system, or large thunderstorm complex, swept through the metro yesterday afternoon with the strongest wind hitting in the northern sections of the area. Below are the preliminary storm reports showing a lot of high wind gusts and damage. Trees and power lines were down in many sections of the metro and MLGW reported over 37,000 customers without power at the peak following the storm and still nearly 10,000 as of this writing (8:00am Friday).

You'll see from the storm reports that high wind was reported from near Wichita, KS right through the metro and east to nearly Atlanta. There is some debate about whether this was a "derecho" - a long-lived wind event that must meet several criteria to receive the label. The only one that seems to be in question being multiple well-separated reports of 75+ mph wind, though we're pretty sure a hurricane-force wind was required to throw this ATV into the air near Jonesboro yesterday! In addition, a train was derailed and tractor trailers blown over in northeast AR.

A flying four-wheeler ended up in a precarious position yesterday in Nettleton, AR in one of the more iconic images of the storms!
So what's in store for today? The stalled frontal system continues to linger in the area with a weak northwest flow aloft over the area, allowing upper-level disturbances from the Plains to move into the region. The Storm Prediction Center has placed a large area, including the Mid-South, in a Slight Risk for severe storms, as shown below, with the main threat again being high wind.

Scattered showers and t'storms will become possible mainly this afternoon. In fact, the HRRR high-resolution model (which handled yesterday's storms well) is predicting scattered activity after lunch with another complex of storms (perhaps not as strong as yesterday) moving through around rush hour tonight. Once again, we recommend battening down the hatches and securing outdoor objects that might have been loosened yesterday just in case. Also, a Flash Flood Watch remains in effect until midnight so some areas could see ponding of water or low-lying flooding front heavy rain produced by any storms.

HRRR modeled reflectivity (radar precip) at 2pm showing the chance of scattered storms.

HRRR modeled reflectivity (radar precip) at 6pm showing a line of storms moving through. 
The weekend shows a similar pattern to the past couple of days with a stalled front near the Mid-South. Saturday appears to produce another convective system, but there's a better chance that this one misses the metro, likely pulling to the north. By Sunday, a low pressure system ejects out of the plains and makes a run down the stalled front, perhaps producing more storms for our area. The whole system then tries to slowly advance east early next week, but takes it's sweet time. Thus scattered showers and thunderstorms remain in the forecast through at least the middle of the week. Click here for our complete forecast.

As with yesterday, stay with us on our social media channels (listed below) for the latest info and keep an eye to the sky. Our mobile apps also put the latest information at your fingertips.

Erik Proseus
MWN Meteorologist

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