Friday, June 30, 2017

It's Independence Day weekend - who's bringing the fireworks?

It's overused, but apropos for the 4th of July. "Mother Nature's fireworks" could be a concern for the next few days as a frontal system nears our humid region. Upper level flow will favor the passage of disturbances - flies in the ointment, if you will - that will spark scattered showers and thunderstorms as we head into a long holiday weekend. We'll take this a day at a time...


A narrow line of heavy rain and thunder is moving through the metro as I type. The fortunate side to this is that it appears that should mark an end to most precipitation for the day as it pushes the instability east of the area and temperatures sit in the mid 70s behind the line, coincident with normal peak heating hours. Evening activities look to be in decent shape, though the next round of showers and thunderstorms is poised to enter the metro overnight. It'll be humid out, but temperatures should be a bit cooler than the past few evenings, likely in the upper 70s.

A Marginal (level 1/5) Risk of severe weather is forecast through 7am Saturday. This is mainly for storms that are expected overnight tonight and should occur after most evening activities are done. The main threat is isolated strong wind gusts and hailstones. (SPC)


A cold front will slip into the northern portions of the Mid-South tonight as an upper level disturbance sparks a complex of thunderstorms in OK and western AR. Some of that activity is expected to move east into the Mid-South overnight into Saturday morning. Once again, this could be decent timing for afternoon and evening activities as the morning rain could help stabilize the atmosphere a bit. There still is come question on timing of the early day rain and its exact influence on the rest of the day, so at this point, we can't rule out the re-energizing of the atmosphere and some pop-up showers and thunderstorms during the PM hours of the day, so make sure you still have alternate arrangements for any outdoor activities. We're hopeful that fireworks shows Saturday evening will be provided by those paid to put them on!

The surface map for Saturday evening shows a front draped to our north and just a low chance of precipitation in the airmass south of the front. (NWS)

The Marginal Risk of severe weather for Saturday is now southeast of the metro as storms late tonight are expected to stabilize the atmosphere locally. A few thunderstorms are still expected, mainly in the morning, as indicated by the light green ("thunder") area. (SPC)


As we get further out, the forecast becomes a bit murkier. There are no clear signs right now of any formidable systems moving through Sunday, but with the front remaining just to our north, any subtle upper level energy, combined with what is expected to be increasing heat again (approaching 90 degrees) could be enough to result in scattered showers and thunderstorms. At this point, we would expect those to be more heat-of-the-day storms which should wane during the evening in the absence of forcing to keep them going. Rain chances therefore are currently near 30% with heat indices in the mid 90s.


A work day for some, a vacation day for others... models have been leaning on the possibility of a little more organized chance of storms, particularly in west TN, during the day. Again, the situation is a little murky, but we've included a 40% chance of daytime precipitation, with things quickly diminishing in the evening. Being July 3, I know there are multiple choices for evening fireworks and outdoor events. We're crossing our fingers for a dry evening.


July 4th and the following days all look to see a fairly typical summertime patter emerge with plenty of heat and humidity with a chance of afternoon/early evening showers and thunderstorms. No major frontal systems are expected, though a weak front could move close late in the week. The overall pattern favors the potential for widely scattered to scattered diurnal thunderstorms each day. Unfortunately for those who have enjoyed our below normal temperatures in June, summer looks to make a comeback next week with highs in the lower 90s, dewpoints in the lower 70s, and heat indices pushing 100. Time to find a pool.

Erik Proseus
MWN Meteorologist

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