Stalemate Continues Across Ohio Valley

The battle between scorching heat over the southern Plains and cool air from Canada continue to settle across the Ohio Valley. Record heat in Texas and hot conditions all across the Plains remain locked to the southwest as a trough off to the northeast of the region refuses to budge. In between the result is a storm track that fires up showers and thunderstorms across the zone and slide through at periodic intervals. This pattern resembles the summer regime that has been mentioned for a few months now and will continue for the next two to three days.

On several runs of the North American Mesoscale Model (NAM) and the Global Forecasting System (GFS) have been waffling back and forth on how much ridging would get into the region. One run would show heat building in allowing temperatures to push into the lower to middle 90s only for the next run to temper the northward movement of the ridge and keep temperatures in the middle to upper 80s. That might not sound like a big temperature change but with the cooler temperatures and a slightly weaker ridge, scattered showers and thunderstorms will remain a threat for the Ohio Valley, whereas warmer temperatures and higher heights would likely put a cap in the atmosphere and lead to drier conditions. With the heavy rains over the last couple of months I am favoring the cooler look and thus a daily threat of thunderstorms for the Ohio River northward.

Here is a classic example for Tuesday afternoon, the day that seems most in question:

GFS Middle to Upper 80s; Courtesy of pro.accuweather.com

GFS Scattered Precipitation; Courtesy of NCEP

The GFS indicates a bit less of ridging thus the cooler temperatures. With the cooler temperatures the easier the chance that a few showers and thunderstorms will develop Tuesday and hold temperatures in the mid to upper 80s for most areas.

NAM Lower 90s; Courtesy of pro.accuweather.com

NAM More Ridge, Holds of Precipitation; Courtesy of NCEP

On the other hand, the NAM builds the ridge a bit more and allows temperatures to surge into the lower to perhaps middle 90s. Because of the warmer temperature the precipitation holds off longer allowing for a bit more heat. To the common person this looks like a small difference but in the meteorology of the forecast this is much more.

The point that this is to address is that it cannot get that warm before rain breaks out. Each time warmth tries to over run very wet ground scattered showers and thunderstorms should develop. Take this more as a test in the evolution of the atmosphere and to see if the call is right or wrong.

Turning to the severe weather aspect of things when you have a big clash of air masses, severe weather is always possible. The Ohio Valley has been in the threat for severe weather for three days now and it appears that Sunday and Monday will continue to run that risk. The Storm Prediction Center, much like the modeling, continues to struggle on pin pointing where the best clash will be for potential severe weather. As of Thursday for today (Saturday), the original severe weather was for places mainly north of the Ohio River but with the slow movement and weaker ridge that threat has been pushed back south and west.

Severe Threat through AM Sunday:

Slight Risk for the Western Ohio Valley; Courtesy of SPC

Then for Sunday, which once had the severe threat trending north, it too has been pushed back south and west from the original thinking:

Severe Threat for Sunday Am through Monday AM:

Slight Risk Potential; Courtesy of SPC

This information also leads that on Monday a threat of severe weather will be in place again as uncertainties remain on just how strong this short heat shot should be.

Taking a quick look into the future over the next two weeks, the generally wetter and cooler regime for the summer should continue.

Precipitation Next Two Weeks:

General Amounts of 3 to 6 Inches of Rain; Courtesy of NCEP

Mean Flow Across the United States in Two Weeks:

General Trough In the East; Courtesy of NCEP

So in a nutshell, humid conditions with periodic showers and thunderstorms and cooler than normal temperatures should be expected for the Ohio Valley though the end of June.

By Weather Specialist Josh Ketchen

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