Denver hit a record high of 80 degrees on Monday; two days later, Colorado’s Front Range has been bombarded by heavy, wet snow.
(Associated Press photo of wet snow on golden leaves in Colorado at left … larger version by linking here).
Roanoke hit 74 degrees today, which was not close to a record (86 in 1939 is the Oct. 26 record). Two days from now … I don’t think we’re going to see anything close to what Colorado has been experiencing, though it will be much colder.
We’ve been focusing much of this week on a potential low pressure system moving up the East Coast that might pull down enough cold air and throw back enough moisture for some snow in Southwest Virginia this weekend. Before we get to that, let’s note that we have one more mild day on Thursday, with increasing showers late in the day and overnight as a low-pressure wave moves in from the west. That low will pull a cold front through, leaving us with a raw, windy, maybe showery day on Friday — temperatures will likely get no higher than the low 50s on Friday anywhere in our region, with many places sticking in the 40s. There might be some snowflakes flying on the wind in higher elevations on Friday.
The same upper-level impulse that has dumped snow in Colorado will dive south and east, then lift north and east around a deep southerly dip in the jet stream this weekend. It is expected to help spin up a surface low pressure system that will move very near the East Coast Friday and Saturday. Forecast models are starting to come into alignment that this will happen — there had been a wider variance of projections before. As the low passes east of us near Cape Hatteras, its counterclockwise circulation will be drawing down cold air from the north as it continues flinging moisture inland, and it may be cold enough for snow to develop for a time, especially in higher elevations.
I do NOT think this will mature into a more widespread early-season (try pre-season) snow event for Southwest Virginia for the following reasons:
* Too much above-freezing air at the surface to overcome before precipitation arrives;
* Low likely too weak as it passes our latitude to pull down the cold air needed for widespread snow in lower elevations (below 2,000 feet);
* Low likely to pass a little too far offshore, just east of what would be a prime track for snow in our region, even in mid-winter.
* Both the weakness and eastward track of the low likely to keep the storm from throwing sufficient amounts of moisture inland to (1) cause heavy enough precipitation to pull colder air down from aloft and (2) to allow for sufficiently heavy snow to overcome preceding warm ground conditions for widespread significant accumulations. (Inset precipitation map for Friday evening to Saturday evening from Hydrometeorological Prediction Center shows the lightest green color, or less than 0.10 inch, over most of our region, with no more than 0.25 inch east of the Blue Ridge. If every bit of that were snow and it was cold enough for every flake to stick, that would be 1-3 inches at best … and of course, as I’ve noted above, it’s not likely all of it will be snow and absolutely certain that not all of it would stick.)
I do expect there to be some snow in higher elevations (3,000-feet plus) late Friday night and Saturday morning, maybe even some light accumulations, with snow showers and flurries gradually working down to lower elevations. Blacksburg, at just over 2,000 feet, will probably see some snowflakes, maybe even a dusting of white on grass and exposed objects. Roanoke, at 850-1,100 feet on the valley floor, might even get a few flakes at the end.
All of this is subject to change pending later developments.