Too much rain? Not where I live

Summer thunderstorms can be capricious, dumping big amounts of rainfall in some places and leaving nearby areas dry. That's especially true in the Southeast, where summer is loaded with what meteorologists call "pulse" storms that strengthen and weaken quickly.

Those hit-and-miss storms have been a staple product of the Charlotte area's weather this week.

It seems as if there have been daily thunderstorms in parts of the foothills, and areas to the east of Charlotte have received more than 3 inches of rain this week. But in much of Mecklenburg County, little or no rain has fallen.

Thunderstorms repeatedly have formed in the foothills and moved very slowly into the Piedmont, drying out as they reach Mecklenburg County.  At my house, no rain has fallen this week (through Friday afternoon).

Now the pattern is getting ready to change. A weak cold front is expected to slip southward across the Carolinas on Saturday, and that will serve two purposes.  It will drop temperatures a few degrees late this weekend and early next week. And it will decrease thunderstorm chances, especially Sunday and Monday.

Computer models indicate thunderstorm activity will be a bit lower on Friday afternoon and evening than the past two days, but storms are predicted to be more numerous Saturday as the front pushes southward.

But if you need rain and don't get hit by a storm Saturday, it'll be time to get the sprinkler out.

Temperatures, which have climbed into the low and mid 90s on a daily basis this week, will fall back a bit. Charlotte has been in the 90s for five straight days, and it could climb into the low 90s again Saturday, before the cold front arrives. But highs are predicted to hold in the upper 80s from Sunday into Tuesday of next week.

Slight change in weather pattern is coming

The late-afternoon thunderstorms that have developed on a daily basis this week are a good-news/bad-news kind of thing.

Just about everyone appreciates that the storms drop temperatures to more tolerable levels and produce rainfall, to compensate for the very high levels of drying that take place at this time of year.

But nobody is a big fans of the damage these storms sometimes produce. That has been the case each day so far this week, and the power of summer thunderstorms was on display Wednesday afternoon in Lincoln County. Strong winds blew trees onto houses, and there also was damage in York, Iredell, Alexander and Catawba counties.

We can expect more of the same over the next few days, forecasters say. The only difference is a slight decrease in temperatures.

Charlotte had a high of 93 degrees Wednesday, and the temperature was climbing toward the mid 90s again Thursday at the time of this writing (mid-afternoon). Forecasters say that by Thursday or Friday, high pressure responsible for this mid-June heat wave will slide off the Gulf Coast, and its grip over the Carolinas will lessen.

If you've been watching to the north over the past few days, you've seen several clusters of thunderstorms sweep from west to east across the Midwest and Great Lakes. As high pressure weakens over the Carolinas, those clusters of storms will take a more southerly track and will affect the Charlotte region by Friday or Saturday.

What does all that mean?

It means highs probably will be closer to 90 than 95 this weekend and early next week, and it means the scattering of afternoon and evening thunderstorms will increase. Some of those thunderstorm clusters moving out of the Midwest could arrive in the overnight hours, so we could get an overnight storm or two.

If you've lived in the Carolinas for any length of time, you know that this is typical summer weather. It's how we get our rainfall at this time of year.

Summer's off to a hot start

Summer doesn't officially begin until this weekend, but meteorological summer started June 1, and it's off to a hot start in the Carolinas.

Wednesday marks the third straight day of 90-degree-plus weather, and it appears as if we're in for at least three to five more days of 90 degrees or hotter before there's a change in the pattern.

By mid-afternoon Wednesday, temperatures were in the low to mid 90s across the Piedmont and Sandhills of the Carolinas. An automated thermometer in Camden, S.C., about 80 miles south of Charlotte was showing 99 degrees at 2:30 p.m.

Technically, a heat wave is a string of three or more days with 90 degrees and above, so this is officially a heat wave.

The National Weather Service forecast a high of 94 Wednesday in Charlotte. That would be the hottest temperature in the city in two years, since a reading of 94 degrees at the end of the Democratic National Convention in Charlotte -- on Sept. 1, 2012.

The hottest temperature in Charlotte last year was 93 degrees. That's a testimony to the frequent and heavy rain we got in the summer of 2013.  The rain and clouds kept the heat under wraps.

Thursday storm threat is wait-and-see for forecasters

Meteorologists in the Carolinas have a very tricky call to make, regarding the possibility of a severe weather outbreak Thursday.

There actually could be a pair of threats, with the first developing in the early-morning hours and the second on Thursday afternoon.

A clusters of strong thunderstorms was moving across the Midwest on Wednesday morning. That mesoscale convective system (MCS), a fancy word for a batch of storms, is forecast to continue moving eastward during the day, crossing Illinois, Indiana and Ohio. Then the MCS is expect to curve southeast, and that's where it starts getting tricky.

Some of the computer models predict the storms will move across Kentucky, West Virginia and Virginia overnight. Other models predict the storms will curve far enough southeast to affect the Carolinas in the early-morning hours Thursday. That MCS could bring damaging wind gusts, so the track of the storms is important.

The path of the storms also could have a big impact on what happens Thursday afternoon, when a weak cold front is predicted to move into the Carolinas.

The atmosphere in areas affected by early-morning storms will become relatively stable afterwards. That would discourage the development of afternoon thunderstorms.

So if the overnight batch of storms curve far enough southeast to affect the Charlotte area, there are questions about whether the atmosphere really will become unstable enough for another round of stormy weather in the afternoon.  If the MCS stays farther north and crosses Virginia tonight, then the Charlotte area's atmosphere will be plenty unstable in the afternoon.

Justin Lane, from the Weather Service's office in Greer, S.C., said it probably won't be until 3 or 4 a.m. Thursday before forecasters have a good idea on what will happen in the afternoon across the Charlotte region.

This time, the cold air wedge does Charlotte a favor

The cold air wedge has done it again -- but this time, we should be thankful.

The wedge -- a pocket of cool, damp but relatively stable air that is pushed into the Carolinas Piedmont by high pressure systems over New England -- usually causes us plenty of problems. In winter, areas inside the wedge are prone to ice storms and snow.

In spring, the wedge often contributes to those chilly, rainy days. Does anyone remember the day before Easter?

A wedge of cool air was locked in place Monday across the northern half of North Carolina. While Charlotte was in the lower 80s on Monday afternoon, temperatures were 20 degrees cooler in Raleigh and Greensboro. Computer models, as they usually do, vastly underestimated the strength of the wedge. The models predicted the cool air would remain north of Charlotte.

It didn't. About 11 p.m. Monday, the wedge front pushed south of Charlotte. Dew point temperatures, which measure the level of humidity and instability in the atmosphere, dropped sharply. The wind shifted from south to northeast.

And at that moment, Charlotte was protected from the severe weather to the west.

As is often the case, the wedge of cool air was pushed up against the mountains. Cooler air sinks, and so it often is lodged against the mountains. That is why strong storms dumped several inches of rain overnight in Burke, Caldwell, McDowell and Catawba counties -- areas that were along, or just outside of, the cool air pocket.

So the big question is how long the cool air will remain in place?

Once again, the compute models predict the cooler and more stable air will retreat northward Tuesday. I enjoyed the comment from Justin Lane, a meteorologist at the National Weather Service's office in Greer, S.C. Talking about the predicted northward movement of the cooler air, he said, :"I don't have a lot of faith in that."

More likely, it will be late Tuesday night or early Wednesday before that happens.

Eventually, the severe thunderstorms probably will reach the Charlotte region. But the presence of the cool air wedge in Charlotte has prevented a couple inches of rain from falling overnight. That will decrease the overall storm total for the area and lessen the threat of flash flooding from whatever rain falls Tuesday night and Wednesday.

Is storm threat for real? And what about Quail Hollow?

Since late last week, meteorologists have been beating the drum -- increasingly louder every day -- about the threat of severe weather and flash flooding this week in the Carolinas.

There is a group of people that complains about weather stories that forecast doom and gloom, and I understand all that.  The critics are tired of having their fears built about bad storms (or their hopes built over winter snow) ... only to have the bad weather not develop. 

This time around, the threat seems legit.  This isn't a localized situation of a few severe storms developing on a hot summer afternoon.

Radar image from Monday morning.

A very big low pressure system that has been cut off from the main jet stream flow is slowly meandering eastward across the United States. There's enough heat and humidity in the South, and enough of a spin in the atmosphere, for severe thunderstorms to break out.

There also will be a warm front in the Carolinas later Monday, and those fronts tend to serve as triggers for severe storms.

If nothing else, look at what happened Sunday in Arkansas, Oklahoma, Nebraska and Missouri. And then watch developments Monday, especially in northern Mississippi and southern Tennessee.

Flash flooding might wind up being the biggest problem from the next three days' bad weather. Regardless of whether there are severe storms, we'll see repeated rounds of heavy showers and thunderstorms. The Carolinas have received well-above-average rainfall since December, and it won't take much to trigger flooding.

So, yes ... this appears to be a legitimate threat.

Now, will it have an impact on the Wells Fargo Championship out at the Quail Hollow Club this week?

It looks as if the four competitive rounds, Thursday through Sunday, have a reasonable chance of being played without a lot of interruptions. There still might be a shower or two in the area around daybreak Thursday, but the chances seem good of everyone getting in their first rounds. The next problem would be Saturday, with a chance of showers again. But that looks like a scattered shower situation.

Temperatures won't be summer-like.  We'll be looking at daily highs around 70 degrees and morning lows around 50. It'll feel more like early April.

As for the pro-am tournaments and practice rounds early this week ... Monday's pro-am should make it through without big problems. But any activity scheduled for Tuesday and Wednesday looks mighty unlikely.

Tornado, flood threat looms this week

A slow-moving and massive low pressure system is expected to cause a wide variety of stormy weather across the Carolinas from Monday evening into Wednesday night.

Severe thunderstorms, tornadoes and flash flooding will be threats for the Charlotte region this week, and National Weather Service forecasters say it's a foregone conclusion that the area will be under various severe weather watches and warnings over the next few days.

"This will be a very active weather week," said Scott Krentz, of the National Weather Service office in Greer, S.C.

The severe thunderstorm and tornado threat began Sunday in the Midwest and is expected to shift eastward Monday into the Tennessee Valley and Mid-South. By later Monday, that threat will reach the western Carolinas.

"I think most of the day Monday will be OK, with a few showers around," Krentz said. "But things will start to degenerate around sunset Monday.'
The severe thunderstorm and tornado threat will be at its greatest in the Charlotte region from Monday evening through Tuesday. Forecasters say a warm front that will stretch east to west along the Carolinas border Monday morning will push slowly north during the day and evening. That front will be the focal point for trouble.

"The wind shear will really increase after dark and continue to be high during the night," Krentz said, referring to a weather condition in which winds blow from different directions at various levels of the atmosphere.

Often, especially during the warm season, thunderstorm activity dissipates in the evening, with the loss of daytime heating. That will not be the situation Monday night and early Tuesday, due to the advance of low pressure and the presence of the warm front. Krentz said areas north of Interstate 40 probably will escape the severe threat Monday night, but the warm front is forecast to push northward into Virginia on Tuesday, so all parts of the Carolinas will be at risk then.

The nature of the threat changes as we go through Tuesday, Krentz said. He said severe storm will remain a possibility, but repeated episodes of heavy showers and storms will cause a flooding threat.

"I think that we'll probably be under a flood watch by then," he said, referring to Tuesday and Wednesday.

Krentz said computer models indicate about 3.5 inches of rain will fall in Charlotte from Monday night until precipitation tapers off later Wednesday. About 4.5 inches is expected in the South Carolina Upstate.