Overnight lows will drop to the upper teens and low 20s tonight under partly cloudy skies. Even though winds have settled a bit, wind chill values will still dip to the single digits early Thursday morning.
Much of Thursday will be sunny with afternoon highs approaching the upper 40s to near 50° in spots. Clouds will arrive late in the evening as a storm spins toward the Mid-Atlantic states, delivering a chance at a wintry mix, including moderate icing (freezing rain) for some areas.
The first chance will arrive just before the Friday morning commute, then another chance during the evening drive. Like most of our winter events this season, it's complicated.
Setting the stage
We're in the perfect setup for a wintry mix with cold air at the surface, and storms coming from the south, bringing a layer of warm air a few thousand feet up. This scenerio means the snowflakes melt on their way down to the ground, then refreeze into sleet pellets. That's one side of the wintry mix.
The more likely option with Friday's event is the threat of freezing rain. This is where the snowflakes completely melt, then fall into subfreezing temperatures at the surface forming a glaze on objects. An easy way to remember the two is, freezing rain clings, while sleet "pings" or bounces.
Friday Morning Event
A storm will develop across Texas, then move through the southern states before sliding toward the Mid-Atlantic late Thursday night, with most of the moisture arriving Friday morning before sunrise.
At this point, models have moisture starting as FREEZING RAIN in far southwest Virginia and the New River Valley around 4AM, then spreading to the northeast toward the Roanoke Valley by 6AM.
FREEZING RAIN: Falls as rain, but freezes on contact. You typically see the ice forming first on elevated surfaces such as trees and signs.
The Highlands and Greenbrier may also see sleet mixed in with the freezing rain at times.
By MID-MORNING FRIDAY, surface temperatures should be above freezing with plain rain expected into early afternoon. The exception would be the higher elevations along/north of Interstate 64, where freezing rain may linger.
Rain will taper off during the afternoon, with highs reaching the mid and upper 30s.
Friday Evening Event
Friday evening may pose an even greater threat for icing, as more moisture is expected to accompany the storm through the Mid-Atlantic.
Models are suggesting rain will return around 5PM Friday in the New River Valley and southern Virginia, then move into the Roanoke Valley, Highlands and Central Virginia through 7PM. The rain will transition to pockets of freezing rain after sunset Friday evening with additional freezing rain accumulation.
Freezing Rain Amounts
It's still too early to forecast freezing rain amounts, but early estimates indicate a coating to as much as .25" of freezing rain (clinging ice) through parts of the New River Valley and along the Interstate 77 corridor.
We will continue to update the weather section of WDBJ7.com with details on the Friday freezing rain potential.