Wintry Mix This Weekend?

Over the past couple days, computer data has been hinting at the possibility of wintry weather this weekend. I just got done looking at the latest data this evening, and it continues to show this scenario.

A few rain showers could clip the area during the day Saturday, especially in southern VA. Precip will intensify Saturday night into early Sunday as an upper-level storm system approaches. During this time, central VA could see a mix of sleet (ice pellets) and rain. Northern VA could see a mix of wet snow and rain.

A lot can change from now until Sunday, so we will continue to track this system and bring you more updates over the next couple days.

Legend for the maps below: Rain (green/yellow), Mix (pink), Snow (blue).



Technical Discussion

The key to the forecast in central VA will be the mid-level temperatures. I've posted a Skew-T diagram below. This shows temperatures and humidity from the ground (bottom of the diagram) all the way up 50,000 feet (top of the diagram). I've marked the freezing line in red. You can see the temperature line (pink line) is very close to freezing at 6000 feet, then much below freezing at around 4000 feet. This is your typical sleet profile (snow melts at 6000 feet then refreezes at 4000 feet). This will be something to watch when the new data comes out tomorrow.

Strong Storms Likely Wednesday Evening

Strong to severe thunderstorms are likely in central Virginia beginning late this afternoon in northern and western Virginia and lasting into this evening as a low pressure storm system sweeps into the region and forces a strong cold front through the Commonwealth late tonight.

The first piece of the puzzle you'll notice today for our severe weather setup is the wind shift back to the southwest as yesterday's cold front lifts back northward through the Commonwealth as a warm front.

With a warmer, moist air-mass in place by late this afternoon in central Virginia, along with sufficient upper lift ahead of the approaching low pressure storm system, conditions will be ripe for storms to initiate during peak heating. You can see by 4PM, our first storms should be developing in the mountains and begin tracking southeast toward central Virginia:

The first round of storms could reach the Metro by 5PM at the earliest and affect us through 11PM. Some of those storms could be severe.



The strongest storms could become severe, capable of damaging winds in excess of 60 mph. Any of these thunderstorms could also have hail, frequent lightning, and heavy downpours.

As soon as the cold front passes your location, your severe threat will end. This front should move quickly through the Commonwealth tonight, clearing the Metro by Midnight.

Locations that get the strongest storms will also likely receive the most rainfall from the heaviest downpours, anywhere from a half an inch to near an inch. Stay with CBS6, we'll keep you ahead of the storm.
--Carrie Rose

From the Moon to the Sun: Cool Astronomy Events This Weekend!

We have a couple of interesting astronomical events this weekend, from the Moon to the Sun. The Full Moon is Saturday night, rising in the east in Richmond at 7:40 PM.
This will be a rare perigee full moon, meaning that the Moon is at its closest proximity to the earth in its elliptical orbit around us. As a result of literally being closer to the Earth and also being a Full Moon, it will be 14% bigger and 30% brighter than when the Moon is at apogee (farthest away from Earth in its elliptical orbit).

In addition, there is an optical illusion that occurs when the moon is at the horizon: it looks to our eyes to be huge, even though it really isn't (camera photos can prove this illusion by showing the moon is the same size at the horizon as when it's higher aloft)!

(Image above: Lloyd Kaufman & James H. Kaufman)
So this combination of literally being bigger and brighter plus merely appearing to be bigger should lead to a great Full Moon viewing Saturday at sunset. It looks like cloud-cover on Saturday should be moving out of the area by sunset, so hopefully we'll get to see this Full Moon on the eastern horizon as it rises.

Our second astronomical note for this weekend is the Vernal Equinox.
This is the official astronomical start of Spring on Sunday at 7:21 PM EDT.
This is the exact moment when the Sun's most direct rays are over the Earth's Equator. After this, the most direct rays continue to creep northward into the Northern Hemisphere, leading us into our Spring and Summer months until the Autumnal Equinox, when the most direct rays are back over the Equator on their trek southward into the Southern Hemisphere.