Meteorologist Mark’s Wx Blog for Sun., Feb. 28

Headlines 

A severe storm threat possibly developing for later today

A low-end threat for severe storms this afternoon, possibly increasing after 6:00 pm

Heavy rain, wind & thunder for Sunday night

Flood Watch in effect

Meteorologist Mark’s Wx Vlog 

48-Hour WX

Five-Day Forecast

Today and tonight will be “weather aware” times, for both heavy rainfall and strong to severe thunderstorms.

Daily Forecast Summary

Today: Partly to mostly cloudy. Afternoon showers and thunderstorms are possible. Breezy. Any storm that develops could be strong.

Tonight: Rain and storms. Some of the storms could be strong to severe. Some of the rainfall could be heavy. Breezy.

Monday: Mainly morning showers.

Tuesday: Mostly cloudy.

Wednesday – Thursday: Dry and mild. Partly to mostly sunny skies.

48-Hour Precip Forecast

Meteorologist Mark’s 5-Day Wx Concerns

Today’s system has slowed and that does not bode well for us when it comes to thunderstorm chances. This slow down means that the rain will be later to arrive, giving us more time to warm up and destabilize ahead of tonight’s cold front. That nearly always spells a bit of trouble this time of year. The main threat is for a damaging wind gust, but an isolated tornado cannot be ruled out. I’ll monitor this through the day (very closely) and let you know if my concern increases. If I’m leaning one way or the other, it would be toward “more concerned.” I’ll keep you posted. Keep in mind we still have a flood threat, as any shower or storm could produce very heavy rainfall.

A low-end threat will be present this afternoon, followed by a possibly higher threat after 6:00 pm.

Meteorologist Mark’s Wx Discussion

Often times, a forecast for heavy rainfall can evolve into a forecast for severe storms (and vice versa). The atmosphere give similar signals for both. Up until today, our main threat with this spring-like system has been heavy rainfall. Now that the system has slowed, our concern for severe storms will begin increasing. The threat that should have stayed west and south of us, may creep too close for comfort with this new forecast.

The slow-down of this system is allowing our atmosphere to warm and destabilize. The more sun we get today, the more unstable we become. We do have some wind shear in place, which is ideal for flooding rainfall potential, but it is also an ingredient with tornado genesis. That tornado threat is low, but it only takes one.

The upper-level dynamics are not the most ideal for severe storms, but that could change as we go through the day. I’ll keep a close eye on things and keep you posted on any changes.

On This Day in Wx History

2012 – The first confirmed February tornado in Nebraska state history struck Lincoln and Logan Counties shortly after 4:00 p.m. The EF-0 tornado was on the ground intermittently for up to six minutes and traveled three miles, before dissipating in southwest Logan County. The path of the tornado was over open rangeland and cropland, where limited damage occurred. Patches of snow were still on the ground at the time.

Almanac

19 Days until Spring!

Yesterday’s National Temperature Extremes

High: 93° at Rio Grande Village, Texas 

Low: -13° at Clayton, Maine

Today’s National Wx Hazards

Heavy rainfall and severe storms threaten parts of the South, while wintry weather threatens areas farther north.

Tomorrow’s National Wx Hazards

The most impactful weather will be accumulating snowfall across the Great Lakes region.

 Sunday Story

Ice

February winter storms brought a variety of precipitation to the plateau. What complicated the forecast most was the presence of bitter cold, arctic air. 

Arctic air is very dense, shallow, and heavy. Cold air literally weighs more than warmer air. That’s why when you open the freezer door on your refrigerator the cold air spills downward. 

That heavier air is hard to move and hugs the ground. When a storm system from the Gulf moves in, it may try to bring warmer air from the south. That warmer air is lighter than the colder air, therefore it tends to glide up and over the shallow cold air. That leads to a layer of warmer air on top of a shallow layer of cold air. 

As snow falls from the cloud above, it will encounter that layer of warmer air and melt. Then, as it falls through the layer of shallow cold air at the surface it will begin to cool. If the layer of colder air is thick enough, the raindrop will freeze into a sleet pellet. If the layer is too shallow, the raindrop will make it to the surface and freeze upon contact with sub-freezing surfaces. That’s how you get freezing rain. 

Across the plateau, we have lots of hills and hollers, as we say. Those lower, sheltered areas can sometimes trap that cold, heavy air and lead to more icing in those areas, even as neighboring areas on hills have risen above freezing. 

On the plateau, our elevation can help us out with ice storms. Sometimes our higher elevation places us up into the warmer air that is on top of the colder air. There have been times when lower elevations had an ice storm, while higher elevations just get rain.

Let’s hope the days of ice and snow are behind us. I think many of us are ready for spring!

You all have a great day and keep lookin’ up!

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