8-10 Update - The forecast is still on track (from below), so I figured I'd post an update here for today.
The frontal system is indeed getting itself organized, and it will do well to make the change to seasonably cool weather for the weekend. As far as storms are concerned, the axis of the front will be along I-79 by the time we'd be looking for them to pop. Here's the surface map for the day...
|HPC - Surface Map - Friday PM|
It's been a while since we've had a legitimate frontal system come through here, so this could be more a taste of September coming in. We should all see a thunderstorm today, but for the most part they'll stay under severe levels (the threat is larger for places east/north of us). There will be a 'dry slot' wrapping around the back end of the system that may be suitable for a late-day sliver of sunshine/rainbows, but don't expect that to carry through to Saturday. As the colder air filters in behind the storm system (that Canadian air of high pressure in the High Plains), clouds will pop back up. This means Saturday is a 'transitional day'. Sunday is the real pay-dirt with the sunshine, with Saturday being an in-between kind of day. At least those temperatures will be quite nice. As the mercury struggles to get back to 80, I won't be struggling to get back outside! :-)
Updates Below (most recent 8:00pm)
After a nice run of sunshine and typical August heat it should be no surprise that we're looking to 'give back' as this build-up of untapped energy is going to have more than one opportunity to turn into thunderstorms in the next two days.
Consider it like a one-two punch. Essentially the same upper air system will have two impulses moving along it, each one serving to intensify the main low-pressure area. The second one looks more powerful than the first. Consider the following maps:
|GFS - 500mb Chart - Thursday PM||GFS - 500mb Chart - Friday PM|
|NAM - Thursday PM||NAM - Friday PM|
The first lobe of vorticity (the top left-hand map) isn't as strong as the second, but it will serve to muddy the waters a little bit. The Thursday afternoon event will benefit from more sunshine/heating to kick things off, and the Friday system will suffer from a lack of it. However, Friday's is clearly more well-developed in terms of upper air dynamics, and you can also clearly see more organized convection and storms (looking at the bottom right map).
The system will be developing, organizing, and strengthening on Friday, owing to the decent shot of incoming energy. If you look at the two surface maps for today and tomorrow, you get a similar picture:
|HPC - Surface Map - Friday||HPC - Surface Map - Friday|
Between Thursday and Friday the central pressure of the storm drops about 3 milibars (from 1008mb to 1005mb), which isn't a whole lot but notable. The difference between the area of low pressure and it's attendant high pressure behind it approaches 20mb (1024mb high in southern Canada). This is pretty good for a middle-of-August scenario-- and it will strengthen further through the day Friday.
Front-based forcing is the best kind there is to make sure we all get a piece of the action, so really the most important element left to watch for will be the surface heating. This will pump more thermodynamic strength into the mix. The good news is that it will be fairly easy to tell early on what our potential is: If you've got a sunny, hot mid-day, particularly in our western counties, then you'll be a good candidate for the boomers in the afternoon. On Friday this is not as essential, but having the clouds around to mess things up during the day will help keep the severe weather potential on the lower side. As it is, I'm expecting both days to be under a risk of severe weather. Each day has its strengths and weaknesses to watch for.
One other note-- the payoff!
When a stronger system like this comes through in the summer months, which hasn't happened often this season, we're finally going to get a stretch of below-normal temperatures to enjoy, lined up with a weekend no less! Feast your eyes on the difference:
|GFS - Max Temps - Thursday||GFS - Max Temps - Friday||GFS - Max Temps - Saturday|
Sounds like a well-deserved cool-down indeed. It will take a while to dig the clouds out of here on Saturday, but if we play our cards just right we'll have clearing skies just in time for the Perseid meteor shower's peak late Saturday night. We'll talk about that coming up as well :-)
Update (10:45am) - The Storm Prediction Center has most of our region under a "Slight Risk" for severe weather. Here is the breakdown:
|SPC - Hail Threat||SPC - Wind Threat||SPC - Tornado Threat|
This is a typical set-up for the middle of summer, with the end results that are rather pedestrian in the grand scheme of things. However, we still have to keep an eye out for the gusty wind potential in sections of Ohio. Given the fast-moving wind current aloft out that way, some stronger gusts can be mixed down with the help of heavy rain. One of the give-aways on Doppler that we can see will be if any thunderstorm cluster begins to bow forward. Check back and monitor the maps below to see if storms are heading toward you and if they have that bowing shape. Large hail and tornadoes are not expected to be significant threats today.
Update (8:00pm) - The main line of storms that has developed with today's instability is now approaching our area. The strongest section of it as expected is in interior Ohio, but the greatest threat for severe weather is dwindling already since the primary heating hours of the day are past (and it's not like we got to 100 today or anything). Folks in the north should still get a good show of lightning and thunder, and those south of I-64 should still be on the lookout for an isolated cloud burst (and certainly not be outside in any lightning storm). Feel free to monitor the constantly updating maps below to stay ontop of things. :-)
|Regional Radar/Satellite with Warnings Tracking||
From the Storm Prediction Center (below): Click For a Larger Image
|Activity Overview||Storm Outlook||Watches||Potential Watches||Storm Reports|
|Temperatures||HD Doppler Radar||Estimated Rainfall||Active Warnings|
|Click For Larger||Click For Interactive Radar||Click For Larger||Click For Larger|
Have a great day everyone!