2009.01.27
Precipitation moving in -- can we dodge the ice storm?
Precipitation is moving in rapidly into Southwest Virginia this morning, and so far, it is mostly wet, with a little sleet thrown in. That said, it is close enough that someone, somewhere in the region is probably getting ice, so be vigilant driving this morning, especially on bridges and overpasses, especially traveling north. Temperatures are hovering a few degrees above freezing at Roanoke and Blacksburg, and the question now is whether the evaporation cooling from precipitation will be enough to pull temperatures back to freezing. Blacksburg's dew point is already around 30, so there's not a lot of room for cooling there, while Roanoke's is still near 20, giving much more room for temperatures to drop to meet the dew point. It will be a touch and go situation for a few hours to see if the mercury settles back to near freezing or hovers just above it. If layers of air cool aloft, it's not unheard of in these situations for a brief but heavy fall of sleet or snow to temporarily interrupt the rain, but there is no doubt the upper layers will be considerably warmer than the surface much of the day and the primary precipitation type will be liquid. Whether that liquid freezes on objects near the surface depends on a razor-thin margin of how much it cools in the bottom few feet of the atmosphere, called the boundary layer. That answer will vary with elevation and location across the region.
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I'm seeing a report of 30 degrees at the VT airport now (also light snow reported, but I've learned in the past that this report is often erroneous).
Comment by kevinmyatt — January 27, 2009 @ 7:35 am
Here in SW Roanoke we are sitting at 33.9 degrees at 7:45 and it has been dropping all morning. The roads are slighty wet.
Comment by Ben — January 27, 2009 @ 7:46 am
Lynchburg is 32 with freezing rain ... so those traveling east be alert ... it's not unusual in a weak cold air damming situation for Lynchburg to be faster to the freezing mark than Roanoke
Comment by kevinmyatt — January 27, 2009 @ 7:46 am
Kevin...Blacksburg is getting just rain, but it is freezing to metal surfaces at the VT Airport and CRC area. Cars in the parking lot, along with handrails into the buildings have a light glaze on them, but the roads I drove on were just wet, and I have not seen icing on trees or ground surfaces yet. I did have some rain freeze to my car while driving in this morning, but nothing significant.
Comment by Other John — January 27, 2009 @ 7:51 am
Temp has dropped here in North Roanoke County.. it was 35.6 at 7AM, it is now 34.7 at 7:51 AM... With the dewpoint this low ( 20 ), do you think this rain will now turn into an icing event?
Comment by P. Kelley — January 27, 2009 @ 7:52 am
As we seem to do about twice a winter, we are on the razor-thin margin between a cold rain and ice storm ... at this point the concern for Blacksburg/Roanoke area is primarily above-surface objects like trees and power lines more so than roads, but of course be cautious ... my best guess right now is that most of Roanoke barely escapes while Blacksburg gets spotty ice, but let's keep watching the temperature and see if it falls ... the fact that it is almost all rain now with not even much sleet mixing in shows me the layers above the surface have warmed considerably overnight
Comment by kevinmyatt — January 27, 2009 @ 7:57 am
It was rather slick when I last checked. Some sleet may have mixed in.
Comment by Henry — January 27, 2009 @ 8:04 am
Temps stayed between 33 and 34 on my drive from Roanoke to Blacksburg. I didn't see signs of ice or slick spots, just a very cold rain.
Comment by John Jackson — January 27, 2009 @ 8:04 am
Steady rain and 33 at 8:15 a.m. in Franklin County between Callaway and Rocky Mount.
Comment by Rich D. — January 27, 2009 @ 8:15 am
Roanoke slipped to 34 last hour ... what I'm noticing here is that less rain seems to be reaching than surface than radar would have you believe ... that might indicate some of it is still evaporating, which could be cooling the atmosphere a bit
Comment by kevinmyatt — January 27, 2009 @ 8:19 am
Nothing but cold, dreary rain along I-81 between Christiansburg and Roanoke.
Comment by Ralph — January 27, 2009 @ 8:30 am
Temp dropped from 33 to 30 in about a half hour at the onset of the rain. (we didn't start out with any sleet, either). It is starting to freeze on elevated surfaces now, especially metal surfaces, but roads seem OK ATTM.
Comment by Julie — January 27, 2009 @ 8:43 am
I think Roanoke is going to pull through with a 33/34-degree escape ... wouldn't be surprised if there were some spotty ice on metal here or there, especially around the rim of the city and in higher elevations ... Lynchburg is now 30 degrees, so the ice could get troublesome over that way ... I have seen times when we've continued to creep ever slowly downward, so maybe not a total all clear yet, but definitely not a major ice storm for the Star City, and probably not for most of New River either.
Comment by kevinmyatt — January 27, 2009 @ 9:11 am
Thirty-two degrees and raining here on the Bedford side of SML. A few pings of sleet at the onset around 6:30 am, but primarily just rain. The rain is not freezing on anything that I can see from my perch.
Comment by Jp — January 27, 2009 @ 9:32 am
since it is probably going to be just a rain storm, how much rain are we looking at for the next few days?
Comment by Mike — January 27, 2009 @ 9:34 am
Kevin,
It seems unusual for us here in Fredericksburg to be colder than you guys. We've been getting a steady snowfall since about 8:00 a.m. and have almost two inches on the ground. The back edge of the precip. is already east of the Blue Ridge, so this first system is about done. The main storm is supposed to dowse us with sleet and freezing rain this afternoon and tonight, hopefully turning to rain tomorrow without significant icing accumulation.
Comment by Chris — January 27, 2009 @ 9:42 am
Kevin...I am a frequent viewer of your page and appreciate the explainations you provide for your readers. As a teacher, I reference some of your descriptions. Just wanted to let you know that where I live, in Rockingham County (central Shenandoah Valley), we have 26 degrees and a steady snow falling. It's been mixed with sleet from time to time. We have a little over 1 inch at the moment. Keep up the good work!!!
Comment by Lee S. — January 27, 2009 @ 9:44 am
When I left (Goodview) for work at 9:15, it was 31.3...I see it's 30.4 now. The fir and pine trees were starting to droop with a light coating of ice. There was a light coating on the glass tabletop on the deck and the drips hanging off the deck railing were beginning to freeze.
Comment by thinksnow — January 27, 2009 @ 10:03 am
Too bad we got nothing but rain, although rain is still good. No school for a rainy day!I was looking at TWC's radar and it shows it's snowing in Richmond.Is there a reason why we are getting rain while they get snow?
Comment by Ben — January 27, 2009 @ 10:17 am
Up in Lexington it's raining right now (10:50AM)- some sleet/snow is still on the ground but appears to be melting
Comment by Matt — January 27, 2009 @ 10:50 am
Roanoke down to 33 degrees now ... and reports of light icing on trees in Salem, according to the National Weather Service. So we may not be entirely out of the woods yet in the Roanoke Valley.
Richmond is reporting sleet and 32, Lynchburg still freezing rain and 32 ... the cold, dry air was deeper to the east so more evaporational cooling has been able to produce sleet and even snow in locations esat of us, but it should be brief.
Hydrometeorological Prediction Center is forecasting rainfall amounts of about an inch over most of the area ... here's the HPC's 48-hour rainfall forecast map: http://www.hpc.ncep.noaa.gov/qpf/d12_fill.gif
Comment by kevinmyatt — January 27, 2009 @ 10:58 am
Will all of this rain/freezing rain that we are seeing now, will it refreeze tonight and cause travel problems tomorrow morning?
Comment by Jessie — January 27, 2009 @ 11:09 am
Here just north of Charlottesville, the temp is 28 deg with a 26 deg dewpoint. It has been primarily a snow/sleet event with about 1/2 inch accumulation. The sleet has definitely kept the accumulation down since it all started at about 6:30 this morning. They are calling for 1-3 inch accumulation before it changes to frz rain.
Comment by John — January 27, 2009 @ 11:32 am
Hi Kevin,
What an inch of liquid could do in a snow event! Another miss for us but on the whole the NWS did well predicting this storm. Here on Peakwood at 11:49AM it is 32 with light freezing rain. Back deck is coated with thin ice and shrubbs and trees have some ice as well. Nothing dramatic, but looking at radars to the west we have a lot of precip to go through. You are right, radar not matching surface observations in intensity.
May have to go into February for the 1 inch snow. How is Ground Hog Day looking this year? That's this coming Monday, day after the Super Bowl.
Steve in Roanoke
Comment by Steve Murray — January 27, 2009 @ 11:53 am
Kevin,
A comment on an earlier blog entry - I believe the NWS radar site is actually on Coles Knob in Floyd Co., some 13 miles SW of the TV transmitters on Poor Mt.
Keep up the good work. Surely the odds are this cruddy pattern that has us in a snow deficit is bound to break soon. Maybe in February.
Comment by martinj — January 27, 2009 @ 12:00 pm
It looks like accuweather is still calling for us to have treacherous ice tonight - Wednesday. How is that possible if the temperatures are supposed to rise? They must be wrong!
Comment by Bradley — January 27, 2009 @ 12:39 pm
Back from a short drive seeing where the ice line is south Roanoke County ... about 1600 feet, I'd say ... thickest ice was around Happy Hollow Gardens and Valhalla Vineyards on Mount Pleasant Road, 1/10 inch on most trees, fencelines, etc. ... spottier ice on elevated objects along Roselawn Road, where Buck Mountain Road crosses under the Blue Ridge Parkway, even some near the Summit Apartments on US 220 and and the upper extent of the Branderwood neighborhood ... I know these don't places don't mean a lot to folks away from the southern Roanoke Valley ... I will be posting some photos shortly and discussing why it is the weather service is holding onto ice through tonight in the forecast
Comment by kevinmyatt — January 27, 2009 @ 1:04 pm
Martin: NOAA weather radio identifies the radar site as being in Roanoke County, but I think it's very near the county line ... you are correct that it to the south of the highest part of the mountain, though ... in fact, the tall part of Poor Mountain creates a radar shadow that extends over western Roanoke County and widens up near the Va-Wva border north of Hot Springs, which often shows a noticeable gap in precipitation when none exists
Comment by kevinmyatt — January 27, 2009 @ 1:12 pm
North of Charlottesville, we had some dry air spill in from the NE and nothing is falling now except for some mist. I'd guess our brief snow event is over.
Comment by John in Charlottesville — January 27, 2009 @ 1:32 pm
John, what you bring up could be a key to what may happen down here ... that would indicate a building cold air wedge southward ... if that builds in during the afternoon and evening, we might chop another couple of degrees off and have more widespread ice ... what a complicated system
Comment by kevinmyatt — January 27, 2009 @ 1:42 pm
The NWS Radar dome is in Floyd County at Cole's Knob, which is in the northeast part of the county and just a few miles from me. It's not too far from the Roanoke Co. border, maybe 10 mi. as the crow flies, but is actually closer to the Montgomery Co. line. If you are watching the radar in loop mode, you can zoom in on the spot on the map where it looks like no precip. (sometimes looks like a beam emanates from there, b/c it really does) and that's the dome. As Kevin notes, there are a couple of higher points around like Poor Mtn. that do cause radar shadowing, but NWS has a good handle on these 'blind spots' and there are several spotters in the area that can help fill in the gaps.
Comment by Julie — January 27, 2009 @ 1:49 pm
OK, my bad ... the NOAA weather radio transmitter is on Poor Mtn. in Roanoke County ... the radar dome is where Julie and Martin say it is in Floyd County
Comment by kevinmyatt — January 27, 2009 @ 1:59 pm
That dry air gap filled in quickly and we are now getting freezing rain and sleet. I see some yellow echoes west of I-77, maybe some sleet is headed your way.
Comment by John in Charlottesville — January 27, 2009 @ 3:07 pm
Advisory upgraded to a WS Warning for my area (Goodview, just east of the parkway). It's 31.1 and has hovered around 31 all day. According to relatives (I'm still at work), all trees and such (no roads yet) are completely covered by around .15 to .20 inches of ice.
Comment by thinksnow — January 27, 2009 @ 4:28 pm