Light wintry mix ahead of another cold weekend

A busy upper air "highway" is keeping conditions unsettled at the surface here in Mecklenburg County. A couple of shortwave troughs zipping across the region this midweek period will bring a mixture of rain and snow, with a slight chance of sleet as well. The wintry precipitation won't amount to much given relatively warm temperatures and a limited amount of available atmospheric moisture.

Skies will be mostly cloudy today (Wednesday), accompanied by a northeasterly breeze generated from a surface low pressure scooting eastward across North Carolina. Afternoon highs will top out near 40º, with local temperatures remaining above freezing until this evening. The snow/sleet combination looks to begin near the dinner hour but won't total up to much. This NWS Wakefield probability graphic shows the area has only about a 30% chance (less than a coin flip) of seeing more than an inch of frozen stuff:

Precipitation will end during the wee hours overnight, and by dawn Thursday skies will be clear. Temperatures will begin the day in the mid-20s, so refreezing of wet surfaces is likely. By tomorrow afternoon local thermometers will again climb to near the 40º mark. Sunshine and a dry northerly wind will aid the melting process.

Then Friday afternoon yet another cold front will cross through, yanking down Arctic air for another cold weekend. This frigid air invasion looks to be brief, and next week then appears to bring relief in the form of more average February temperatures. We can hope!

Will Groundhog Day be a turning point this winter?

The verdict is in: P. Phil has seen its shadow. Does that really mean six more weeks of winter? This graphic likely illustrates a lot of folks' feeling about the issue:

Setting aside the ability of a rodent to predict the weather(!), this - Monday - morning's temperatures around Mecklenburg County bottomed out in the teens. The frigid readings were a result of last night's clear skies, light winds, and the snow-covered ground. The good news is that afternoon highs will climb above freezing to near the 40º mark. Along with light winds and abundant sunshine, the outdoors will feel less glacial later today.

Tuesday morning will start out somewhat less brutal, with local thermometers "only" dipping into the low 20s. Clouds will fill in as the day progresses, and a light southwesterly breeze ahead of the next cold front will bring in warmer air such that afternoon highs tomorrow will top out in the mid-40s. 

Another chance of light precipitation will then move in after dark Tuesday and last into Wednesday night. Mecklenburg County looks to be far enough south that the temperature profile for this event will be warm enough to keep the precipitation as mostly rain. At the moment there is no expectation of accumulating snow locally, but it's something to keep an eye on as the week progresses.

Snowstorm's gone and temperatures will warm...slightly

This weekend's snow storm was predominantly a Carolina event as shown on this map of snow depth reports:

One report from the Ivy Hill boat ramp on Buggs Island / Kerr Reservoir measured 5.5", which verifies the original 4-6" forecast that NWS Wakefield had for Mecklenburg County. Given the very dry air there wasn't a lot of moisture available for this storm to work with. However, the very cold temperatures boosted the snow-to-liquid ratio from the typical 10:1 (10 inches of snow to 1 inch of liquid) to more like 15-20:1. 

Speaking of temperatures the good news is that after today's (Sunday's) chilly regime things will warm up a bit. This afternoon local thermometers will top out near 30º, accompanied by gusty northwest winds as the now fully developed nor'easter pulls away from the coast. After temperatures Monday morning dip again into the teens, much of the work week will feature afternoon highs in the low 40s. That should help with the melt process.

However, the stubborn pattern of an upper level trough across the eastern half of the nation will keep things unsettled. A series of Alberta clippers will arrive every 48-72 hours, bringing chances of light precipitation. Temperatures for the first one on Wednesday look to be warm enough for mostly a chilly rain, with a wintry mix possible during the overnight hours. Friday's could be much the same, but there may be less moisture available for the disturbance to work with.

Welcome to February!

Another weekend, another snow storm

Yes, it's true: Folks have until later this Friday afternoon to prepare for the next round of snow. A low pressure center is currently tracking eastward over the Gulf Coast states. It will make a turn to the northeast after it emerges off the Georgia/South Carolina coast. Given the bitterly cold temperatures in place all the way from the surface to higher levels in the atmosphere, this will be an all-snow event.

Speaking of temperatures, this morning's lows in Mecklenburg County were in the teens and will only rise into the mid- and upper 20s today. Snow showers will become likely late this afternoon, becoming steadier and heavier tonight. The white stuff will be of the light and fluffy variety vs. the typical heavy and slushy stuff thanks to the very cold temperatures. 

Here are the forecast snow totals from NWS Wakefield:

The left panel shows the mostly likely snow totals (although showing them to the nearest tenth of an inch isn't the best, given the uncertainties involved in the numerical forecast models). The right panel shows the probability of seeing six inches or more. Note that the odds of that much snow are less than 50% - a coin flip - for Mecklenburg County.

Snow will continue all Saturday and last until at least dawn Sunday. The snow, however, isn't the only major weather story for this weekend. Temperatures won't budge much above 20º all day tomorrow. And, as the low pressure center intensifies off the Outer Banks, the winds will strengthen as well. Coupled with the frigid temperatures, gusts up to 25 mph will drop wind chills below zero early Sunday morning.

Sunday will turn out sunny, blustery, and cold, with afternoon highs struggling to reach the freezing mark. Northwesterly winds will continue to gust up to 25 mph as the low pressure center - by then a nor'easter - pulls away over the North Atlantic waters. Folks shoveling off sidewalks and driveways will thus need to protect against frostbite.

Happy Friday!

Midweek "mildness", then another snow storm?

The "mildness" in the blog post title is a relative term. Average Mecklenburg County daily highs and lows are 51º and 28º at this point in January. Thus, the forecast for Wednesday and Thursday of mid-30s highs followed by morning lows in the low teens seems like it should be labeled "frigid" instead. But wait 'til the weekend...

Today - Wednesday - will feature clearing skies as more cold and dry air pours in behind last night's weak cold front passage. The sunshine will help boost temperatures into the aforementioned mid-30s this afternoon, with only a light westerly breeze to stir the air. Clear skies, light winds, and the persistent wintry ground cover will help thermometers plunge into the low teens overnight.

Thursday's conditions will resemble a cut and paste of today's, with similar temperatures and clear skies. Then the weather will go from relatively "mild" to another chance of snow for the weekend. This setup will be different from the previous storm, with the precipitation looking to be all snow this time. Per the graphic this next winter storm will be a "Miller A" situation (vs. last week's "Miller B"):

At the moment snow looks likely to start late Friday afternoon, last all day Saturday, and end Sunday morning. Forecast snow totals will come into better focus later today as the numerical models (hopefully) zero in on the exact storm track. However, several inches of the white stuff are likely.

Keep the snow shovels handy!

This could well be the coldest week of the winter

This past weekend's winter storm had plenty of Gulf and Atlantic moisture to work with. This graphic shows the snowfall totals across the lower 48 states through 7 o'clock Sunday evening: 

Local snow totals were minimized as sleet took precedence, thanks to an above-freezing air layer sneaking in over top the dense Arctic air at the surface. That frigid air isn't going anywhere anytime soon.

Today - Monday - temperatures will only range from morning lows in the upper 20s to afternoon highs in the mid-30s. Arctic air will continue to pour into Mecklenburg County today via westerly winds gusting up to 20 mph. Wind chills will make it feel about ten degrees below the air temperatures, so kids (and adults!) heading out to play in the snow and sleet will need layers of clothing. 

Those local thermometer readings will nosedive into the single digits by dawn Tuesday. Thus, the region is under a Cold Weather Advisory from 9 p.m. tonight until 10 a.m. tomorrow. Sunny skies will provide a false hope of warmer conditions as chilly breezes continue. Forecast high temperatures in the mid-30s Tuesday afternoon may be optimistic given the wintry ground cover.

An additional blast of Arctic air will follow behind another cold front midweek. Keep that cold weather gear handy, and check on neighbors periodically.

Winter storm updates, and a peek at a frigid week ahead

Winter has firmly asserted itself across Virginia this Sunday morning. Locally, precipitation over Mecklenburg County has mostly switched over to sleet (it bounces!), with freezing rain (sticks to what it touches) not far behind. How can it not be snowing when surface temperatures are in the teens? Check out this sounding from this morning's weather balloon launch in Greensboro NC:

This is known by weather geeks as a "Skew-T Log P" plot, where height above ground is indicated by the logarithm of the air pressure on the left vertical axis. Temperatures are in degrees Celsius and are skewed from lower left to upper right. The notations on the above chart show that the air temperatures between 900 millibars (~2500 ft overhead) and 700 millibars (~10,000 ft overhead) are above freezing.

Thus snowflakes dropping out of the clouds pass through this warm layer and melt. Then, falling back into below freezing air they refreeze, either as sleet (before hitting the ground) or as rain which freezes when it contacts the ground or any another surface. The latter precipitation type is the concern for the rest of today, as ice will accumulate and create very slippery conditions along with possible power outages.

Precipitation will finally dwindle after sunset this evening. Following afternoon "highs" in the mid-20s tonight's temperatures won't budge much. Monday actually looks like it could warm to slightly above freezing but the winds will pick up as well, gusting over 20 mph at times. The combination of icy tree limbs and power lines coupled with wind could enhance the potential for power outages.

The remainder of the week won't be any warmer. Tuesday could also feature afternoon highs near the freezing mark, but that would be after morning lows in the single digits. The next chance for highs at or above freezing won't be until next weekend.