Friday, September 16, 2016

Rain for weekend activities? And what about this heat?

I spent a very worthwhile several days in Norfolk, VA this week at the National Weather Association Annual Meeting. The NWA is one of two professional organizations for meteorologists, geared primarily towards operational forecasters. There were lots of great presentations and networking opportunities, but I'm glad to be back! Here's one of my favorite pics - Jim Cantore really is a great guy!

As we get deep into mid-September, it's about time for the heat to depart! This week has been another cooker with highs in the mid to upper 90s. Fortunately, dewpoints have been a bit lower than when we had these same temperatures in the midst of summer, so heat indices have remained below 100 for the most part. As we head into a busy weekend for outdoor events, such as the Cooper Young Festival, a Memphis Tigers football game, and of course Friday night high school football, there are a couple of changes to the past week's pattern - a bit less heat and a bit more rain!

Starting tonight, things are looking good, but warm, for football. Temperatures will settle into the 80s by dusk and rain chances are minimal. Wear your favorite school's t-shirt and leave the umbrellas at home.

By Saturday morning, the ridge of high pressure that has dominated our pattern this week will move east as a large upper-level trough moves closer. That will push a front into the area and rain chances go up. There could even be showers around by dawn tomorrow, but the best chances look to be from mid-morning through early afternoon. Rain chances right now stand at about 50% but a complete washout is not expected.

If you have plans to go to Midtown for either of the two big draws tomorrow, bring your poncho and have a good time, but expect some rain at some point and keep your eyes and ears open for lightning and thunder. Your MWN app will come in handy, even though the NWS Doppler is down. Our radar will continue to show you what's headed your way. Rain amounts will generally be in the 1/2" range with some areas seeing a bit more or less.

The American GFS model showing expected rainfall totals through 7pm Saturday. Heaviest rain, and highest rain chances will be to our north, but scattered showers and a few thunderstorms are also expected locally, mainly in the middle part of the day. (PivotalWeather)
The Storm Prediction Center severe weather outlook for Saturday shows a risk of "general" (non-severe) thunderstorms in the metro. Severe weather is more likely well to our west. (NOAA/NWS/SPC)
As mentioned, thunderstorms are also possible, but severe weather is not anticipated. There's just not going to be enough upper level wind energy or low level instability to generate strong wind or hail. If lightning is nearby, take your lightning safety precautions. Your car is the best place to be if a sturdy structure is not accessible, but indoors is best. They'll put you on the concourses at the Liberty Bowl if lightning threatens, but trust me, that's only marginally safer than the exposed bowl. If you can find a way to get walls around and over you, that's better.

Rain chances go down in the evening as the upper level wave responsible for the daytime activity moves east. Levitt Shell and other evening activities have a better chance of remaining dry than those earlier in the day, but a shower is still possible well into the evening.

Sunday is questionable. Some models dry us out, others hang some atmospheric energy back and keep rain chances in the forecast. With the core of the upper level trough moving overhead, the prudent forecast maintains at least a chance of showers or a thunderstorm, which I have done. Probability of precipitation is 30-40% Sunday, subject to change. If you're picking the drier day this weekend for outdoor stuff, Sunday is your best bet.

The American GFS model at 500mb (18,000') shows the trough moving through Sunday evening that ends rain chances as high pressure builds quickly in behind it, escorting heat back into the Mid-South next week. (PivotalWeather)

Heading into next week, unfortunately a summer-like ridge of high pressure builds over the central U.S. once again and we heat back up. The MWN Forecast is carrying 90's throughout the week with mid 90s quite possible in the middle of the week, and virtually no rain chances.

The mid-level weather pattern for the middle of next week, as shown by the American GFS model, is dominated by anomalously high pressure over much of the CONUS and centered over the Southern Plains. This will lead to hot conditions. (WeatherBell)
The good news is that in the long-term (a week to 10 days out), I'm seeing a fairly strong pattern shift that should bring more autumn-like weather to the region for the end of September. It can't come soon enough!

Erik Proseus
MWN Meteorologist

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