Tuesday, November 30, 2010

Severe Weather Risk: Late Tuesday - Early Wednesday

There is growing concern today for the threat for severe weather late tonight into early Wednesday morning. A potent storm system will track across the Carolinas tonight increasing the severe weather threat for central and eastern North Carolina between 10pm Tuesday night and 8am Wednesday morning. This is the same storm system that has already produced tornadoes in Louisiana, Mississippi, and Alabama.

One of the big concerns with this severe weather threat is the timing. Many people will be asleep and may not hear warnings. Storms could be moving quickly, and there may be little time to act. We mention it time and time again, but it will be very important for everyone in central and eastern North Carolina to have a NOAA Weather Radio tonight. These special radios will sound an alarm when a severe weather warning is issued. Models with SAME technology can be programmed to only alert you when warnings are issued for where you live.

The greatest risk from storms overnight may come from damaging straight line winds. A thunderstorm does not have to produce a tornado to cause wind damage. Straight line winds can cause extensive damage similar to tornadoes. The Storm Prediction Center says there is a 30% probability for damaging winds in the area --

The tornado probability is given at 10% --

10% may not sound like a lot, but keep in mind that is a much higher chance than what is expected out of most November storm systems. A few tornadoes will be possible overnight.

While it does not happen that often, North Carolina does have a history of strong overnight tornadoes in November. We cited a few examples in yesterday's blog post. Many longtime Raleigh residents will remember the November 1988 tornado. That tornado reached F4 intensity and stayed on the ground for 84 miles.

We expect the overnight storm threat to be ending by 6am in the Triangle and Sandhills and by 8-9am in coastal North Carolina.

Our team of meteorologists will continue to follow the latest weather information coming into the forecast center. We'll have around the clock coverage of tonight's storm threat. Stay tuned for Weather on the Ones updates on News 14 Carolina.

Lee Ringer
News 14 Carolina Meteorologist

Monday, November 29, 2010

Strong Storms Possible Tuesday Night into Wednesday Morning

Central and eastern North Carolina could be in for a round of stormy weather late Tuesday night into Wednesday morning. A warm front will lift through the state Tuesday bringing a much warmer day with highs in the upper 60s to low 70s in the region. We don't expect much in the way of rain during the day Tuesday except for a few spotty light showers. That will change Tuesday night as a cold front moves across the state meeting up with warm, humid air.
Locally heavy rain along with strong storms will be possible just ahead of the front. The biggest threat from any strong storms will be damaging winds, but at this point, isolated tornadoes cannot be ruled out.

The severe weather danger will be higher since this chance for storms will come overnight when many people will be sleeping. Unfortunately, North Carolina does not have a good history with overnight severe weather. The state leads the country in the number of fatalities from nocturnal tornadoes.

There are several examples of overnight tornadoes in November:
While this is just a slight risk for severe weather at this point, it is a good time to make sure you have a working NOAA Weather radio with fresh batteries. Weather radios will sound an alarm alerting you to severe weather warnings in your area.

Stay tuned to News 14 Carolina and news14.com for updates.

Thursday, November 18, 2010

Turning Colder after Thanksgiving?

The latest 7-day outlook shows a nice warm up just before Thanksgiving with highs reaching the 70s in parts of central and eastern North Carolina. Big changes could be on the way just after Thanksgiving though. Models have been showing some consistency in forecasting colder air moving into the eastern U.S. from just after Thanksgiving through early December. The Climate Prediction Center is also predicting colder than normal temperatures for the eastern U.S. in the latest 8 to 14 day outlook --Time will tell just how much cold our temperatures will drop during that time period. December through February is forecast to be warmer than average, but there can always be a few cold snaps in a winter that is colder than normal. Looks like we'll be reminded of that heading into December.

Lee Ringer
News 14 Carolina Meteorologist

Friday, November 05, 2010

What is the Difference Between a Frost and a Freeze?

Last weekend we had advisories for the possibility of frost, especially for low-lying and rural areas outside of Raleigh, Wilmington and Morehead City. This weekend we face our first freeze of the season.

What is the difference between a frost and a freeze? Frost occurs on a clear, still night, as heat radiates from surfaces (like your car window, a field, etc.) to the sky. The temperature drops below 32 degrees and water vapor freezes on those surfaces (a process called sublimation..or gas being converted to a solid while bypassing the liquid stage). The temperature won't go much below freezing, because energy is released as the water freezes.

Most plants that aren't tropical can handle temperatures a few degrees below freezing with no problem, and if you have plants up against a house (even tender plants) they can usually be spared as heat will be trapped by any overhang.

Clouds or fog will trap heat, usually preventing a frost.

A freeze, however, is caused by cold, Arctic air moving into a region. It is a relatively dry air mass that is much colder than freezing, and you can have moving wind in cases of a freeze.

Much of the damage we see on plants from a freeze is called desiccation -- severe drying of the foliage.

Due to the fact that this involves a chance of air mass, there is less protection for plants by ways of cover or overhangs, so they need to be brought in if at all possible.

Usually a hard freeze marks the end of a growing season. In central North Carolina, we typically see our first freeze of the autumn season anytime from mid-October for the extreme north/northwest Triangle region to after November 1st for the southern Sandhills and Coastal Plain.