at 8:20 PM by Pierce Larkin

WxRecap: Morgantown Flooded

Well, today did not go completely as expected.

h/t giphy.com
h/t giphy.com

My forecast of “…scattered storms possible” should have been a likely, and had the words, “heavy rainfall/flash flooding is possible with any slow moving storm” associated with it. Hindsight is 20/20, though.

Let me breakdown the set up for this afternoon’s weather, and then I’ll give you the basic result of it. First of all, and likely one of the more important aspects of this event, there has been a fairly stationary boundary located across the Midwest and eastern US.

This shows the boundary that has been set up across the region the past few days. h/t COD Weather
This shows the boundary that has been set up across the region the past few days. h/t COD Weather

This boundary hasn’t been very significant, but has separated two different air masses. On the southwestern side, there was deep, deep boundary layer (from the surface to about 1.5 km off the ground) moisture present, and on the other side, it was much drier. This boundary was the initial portion of sparking these thunderstorms off.

The reason the thunderstorms were able to produce as much rain as they did was because of the amount of moisture present in the atmosphere. Precipitable water is basically just how much rain would fall if you squeezed all of the moisture out of the atmosphere out. Precipitable water values are very key in forecasting heavy rainfall, and are a good indication of how much moisture is in the atmosphere. Well, they were very high today.

To give you some perspective, the average precipitable water value for Nashville is only 1.31″ for this day (climatologically speaking). We saw values here of between 1.9″ and 2.1″, and 1.95″ is the record for the day in Nashville!

The precipitable water climatology for the Nashville sounding location. h/t SPC
The precipitable water climatology for the Nashville sounding location. h/t SPC

Add in dewpoints well in the 70s across the region, temperatures hitting 91°F here in BG (nailed my forecast), and a weak shortwave moving in, everything was there for a cluster of storms to move slowly, and drop high amounts of rainfall in a short amount of time. 

Landon reported that his dad saw 2.5″ of rain in an hour in Morgantown, and many other reports have come out like that. There were plenty of reports have crazy flash flooding in the town, and there were even some reports of wind damage.

Rainfall like that is dangerous, and it is always imperative that you all avoid flooded roadways, and never drive into flowing water.

Just as a heads up for the next couple of days, we could be seeing similar scenarios across the region tomorrow and Thursday. The atmosphere will have plenty of low level moisture in place both days, and we will be seeing a weak shortwave move through tomorrow, and a stronger one on Thursday.

The first, weak shortwave forecast to move through tomorrow. h/t pivotalweather.com
The first, weak shortwave forecast to move through tomorrow. h/t pivotalweather.com
The stronger shortwave forecast to move through on Thursday. h/t SPC
The stronger shortwave forecast to move through on Thursday. h/t SPC

With both of these moving into very warm, moist and unstable environments, multiple rounds of strong to severe thunderstorms are likely. At this time, I foresee Thursday afternoon and evening having a greater chance at seeing severe convection, as a cold front will be passing through the region, with an increasingly sheared atmosphere.

The convective outlook for Thursday. h/t SPC
The convective outlook for Thursday. h/t SPC

However, I don’t know that thunderstorm coverage will be as good on Thursday as it is tomorrow. Tomorrow, we are looking at less shear, but just as much instability across the region. With a weak shortwave moving in, this could cause some of the same issues to arise across the region as did today. We look to have plentiful moisture across the region, and should have plentiful instability.

The SPC convective outlook for tomorrow. h/t SPC
The SPC convective outlook for tomorrow. h/t SPC

Either way, the next few days look to be active. Flooding, damaging winds, and lightning look to be the biggest threats with the storms. Be sure to keep abreast with the latest information, and follow @WxOrNotBG on Twitter for the latest information on the weather.