Monday, September 3, 2012

Atmosphere recharging for Tuesday

Sunset has brought an end to the stormy weather which rocked the Charlotte region on Labor Day, and we should be in for a relatively quiet night.

A few showers are possible for the next few hours, but it will be much lighter than the thunderstorm activity responsible for a number of warnings and some reports of flooding during the late-afternoon hours Monday.

The atmosphere remains unstable and very moist, however.  It's simply recharging for Tuesday.

The rainfall total from the storms at Charlotte-Douglas International Airport was about 2/3 of an inch, but much heavier totals were reported elsewhere. There were radar estimates of more than 3 inches of rain falling Sunday afternoon in Albemarle, where streets flooded for about 90 minutes.

Look for more of the same Tuesday, although the showers and thunderstorms might start developing earlier in the day -- perhaps before noon.

I plan to have a new blog entry around 3 a.m. Tuesday.

6:30 p.m. update ... The thunderstorm responsible for the severe weather warning in Charlotte has weakened and moved north of the city.

As I thought, the strongest part of the storm remained west of the uptown area, which was good, considering the large crowds gathered for CarolinaFest.

The urban and small stream advisory remains in effect until 8 p.m. for Mecklenburg and parts of Union, Cabarrus, Lincoln, Gaston and York counties.  Lancaster County is not in the advisory but should be. Up to 2 inches of rain has fallen since 5 p.m. in some of those areas.

At 6:30 p.m., Doppler weather radar showed another line of showers and heavy storms in the Greenville-Spartanburg area.  Like the rotating bands of precipitation in a tropical system, those storms are pinwheeling up toward Charlotte.  It's not clear if the gradual loss of daytime heating will weaken the storms before they get to the Queen City, but we might not be done with the rain tonight.

And as I've been saying ... Tuesday and Wednesday look like repeats of today.  If this heavy rain pattern continues, look for a wide flash flood watch to be issued. The ground is getting saturated in some places.

5:40 p.m. update ... The strong thunderstorms that have battered areas surrounding Charlotte for much of the afternoon are now taking aim at the Queen City.

A Severe Thunderstorm Warning has been issued until 6:15 p.m. for Charlotte.  The National Weather Service says winds of up to 60 mph and 1-inch hail is likely with this storm, so you should seek shelter.

Truth be told, it looks from radar as if the worst of the storm might stay west of the uptown area, but if you're in the big crowd at CarolinaFest, listening to James Taylor, I'd consider seeking a dry and lightning-proof location.

The bigger problem over the next two hours might be flooding. The strong storm moving into Charlotte will be followed by a number of other showers and thunderstorms, and several inches of rain could fall between now and 7:30 p.m.

"Runoff from this excessive rainfall will cause minor flooding ... especially along small streams in the Charlotte metro area," meteorologist Larry Lee, of the National Weather Service office in Greer, S.C., said about 5:20 p.m.

No flooding reports have been received yet from York County, where this storm came from. But very heavy rainfall is being reported down there.  That precipitation is headed for eastern Gaston and Mecklenburg counties.

By the way, we'll be getting more of this again Tuesday and Wednesday.

Earlier post ... Thunderstorms are developing quickly Monday afternoon across the Carolinas, and if you're attending CarolinaFest at the Democratic National Convention or doing anything else outdoors, keep an eye to the sky.

The atmosphere is very unstable and rich with tropical moisture.

Translated: When storms develop this afternoon, they're dropping torrential rain and sometimes causing some wind damage.  The strong winds are a surprise.  We didn't expect that.  The torrential rain is not.

These are the remnants of Hurricane Isaac, and they've settled over our region. Give the atmosphere a little bit of sunshine -- which happened Monday morning -- and you have instant instability.

One strong thunderstorm developed shortly after noon in Union County and trudged slowly into Stanly County, northeast of Charlotte. That storm dropped more than 2 inches of rain in an hour over Albemarle, and a flash flood warning has been issued.

I also see flash flood warnings to the north of Charlotte, where slow-moving storms have developed.

A look at the radar early Monday afternoon shows bright yellows and a few reds -- indicative of strong storms -- blossoming everywhere.  So far, Mecklenburg County has avoided the activity, but that will end eventually.

In fact, at 2 p.m., the radar showed a strong storm to the southwest of Charlotte, in York County, moving toward Mecklenburg County.  If that system holds together, it could affect the uptown area by 3 p.m.

Heat and humidity has been a problem so far Monday for those attending CarolinaFest, and Medic officials held a special news conference shortly after noon, to remind people of the dangers of heat exhaustion. In a word ... drink water.  And if you feel yourself getting dizzy or light-headed, get into shade quickly.

At 2 p.m., it was 90 degrees in Charlotte, with a heat index of 96. That isn't in the heat advisory level, but it's enough to cause problems for people in a big crowd, where there's little air movement.

Eventually, the heat exhaustion concerns will be replaced by thunderstorm worries.  If you're outdoors and the storms approach, seek shelter -- even if James Taylor is about to take the stage. Lightning is a serious threat, and North Carolina is among the national leaders in lightning deaths.

My big concern is flash flooding, and the bad news is that the threat actually might increase Tuesday and Wednesday.  The type of weather we're experiencing today will probably get locked in place for at least the next 48 hours.

Obama speech update ... The forecast for Thursday, for the President's outdoor acceptance speech at Bank of America Stadium, is going downhill.  The latest computer-generated forecasts indicate the Isaac moisture might not be so quick to leave.  Thunderstorm chances have been increased for the day and into the evening.