Signs of coming cold become clearer — but mild for weekend
This weekend’s weather: Mild, highs in the 60s to near 70, perhaps a few showers (mostly sprinkles) but no widespread significant rain likely until Monday. Should be a good weekend for outdoor activities. Normal temperatures this time of year run mid 40s-near 50 highs and mid 20s-low 30s lows. Being early December, and with what may be coming down the pike, enjoy it!
When the North Atlantic Oscillation and Arctic Oscillation start tanking in tandem, I pay attention. Model forecasts on each show precipitous drops in the next several days. Almost inevitably, this means a colder weather pattern setting up for the Eastern U.S., as the negative phases of the NAO and AO signal high pressure building over Greenland and the North Pole, respectively, forcing Arctic air southward and buckling the jet stream southward into the Eastern U.S. Whether this means occasional shots of cold, a seasonably cold long-term pattern or something even more long-lasting and extreme depends on some details that can’t entirely be foreseen yet, such as exact placement of the high pressure systems causing the northern latitude “blocking.” A third oscillation we often watch in winter, the Pacific-North America pattern or PNA, is showing no signs of budging from its slighly negative phase, which works somewhat against colder weather parking over us with continued low-pressure in the Pacific Northwest and westerly to west-southwesterly upper-level flow across the U.S. Still, if the forecasts for the NAO and AO are correct in their deep nosedives, that level of high pressure blocking in the far northern latitudes will be likely to overcome the relatively weak PNA- pattern and allow more true shots of 
Arctic air farther south. December 2010 was a month with the same combination — NAO-, AO- and PNA- — that ended up as Roanoke’s fifth coldest December since records began in 1912 and produced a series of small snow events.
The first manifestation of this changing pattern in the northern latitudes will be pushes of Arctic air sliding southward into the central U.S., creating boundaries with the mild air that has dominated since the start of the month, leading to a series of low-pressure systems forming and moving northeastward. Expect these systems about every 3-5 days, starting with Monday and continuing perhaps to Christmas or beyond. The first will bring some rain on Monday (1/2 to 1 inch possible, per latest HPC map), then windy cold and some mountain snow showers by Tuesday. Each one will bring a little more cold farther southward and eastward, with mild weather in between — at least at first. If some of the longer-range models are right, cold air may be dispersed across the nation enough about 2 weeks down the road (Climate Prediction Center holding on to warmer-than-normal lean for most of next 2 weeks) that systems after that may have a chance to do something besides just rain on us. But we have several steps in the process to go before we get to that point, and it can still derail. I expect Monday’s “snow meter” will have pretty low numbers for next week.
December 7, 2012 - 6:06 PM
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Mainly we need WET!!!!!!!
Can you elaborate on what “something even more long-lasting and extreme” would mean for us?
wd: We only get to wetter by getting the cold air and warm air to bump against each other and get these storms forming, and getting the jet stream farther south to scoop up the Gulf moisture. Of course if the cold sets in too deeply, and the jet stream is suppressed to the south, we flip from a mild, dry pattern to a cold, dry one. It does appear we will have 2-4 shots at decent precipitation in the next couple of weeks. A late-week storm next week MIGHT have a chance of being a bigger rainmaker than we’ve seen in sometime.
Toots: Very generally, that would mean a long period (2-plus weeks) of frequent sub-freezing cold (even days) and possibly some nights of single-digits or colder lows. That would be the upper end of what could develop if the Arctic air sinks south and holds in place, getting reinforced by even more entrenched extreme cold from the north. But again, this is only a possibility, requires a lot to happen that isn’t fully evident yet, and would likely be 2 or more weeks away even if it did set up. Quite honestly, because of the ongoing PNA-negative pattern, I’m leaning against the extreme scenario.
Joe, your thoughts on sensors would give VDOT a heads up withou sending a truck out on stand-by. Also would help with what chemicals/abrasives to load. The new section of 221 in Roanoke County could have such sensors included as the final pavement is laid. Another tool in place to facilitate efficienty is always welcome as it normally cuts cost. But, it will always be a call by somebody on the scene as what is needed.
WD…
the whole point of the sensors is
just to save man hours..
Ideally you would want to put the sand down
or take action just before freezing starts..
as you dont want to have it washed off surface.
Its not the end all be all…its effective use
of high tech.
Im not suggesting the sand itself be used in the sensors.
Virgina has over 48000 miles of secondary roads…
VDOT maintains over 57000 miles of state highways.
Im sure they-d be ok with standing outside maybe an
hour less on any given cold rainy night.
..
Im also sure theyd like to know exactly where the nose of a cold front
is..instead of saying its somewhere west of Roanoke and east of Bluefield.
As is common, the Old Farmers Almanac is going to miss this weekend big time.
Dec 8-9: Flurries, seasonable.
joe it would seem that VDOT is driven just as much by public perception as by sensors in the road. Although sensors would be very helpful the tax paying public want to see the plow trucks at every corner with plows and spreaders ready to go and some want them running up and down the road spreading cacl and number 8 stone. Have been out all night long just to watch it rain and have been only truck on 220 for two hours
Ah, I see that the Rickster is mentioning one of our whipping boys, the Old Farmer’s Almanac. Nice going. Rick, have you purchased (or been given) the 2013 version? I bought it yesterday, and I think that KM has glimpsed at it, too.
Big headlines for this winter in their monthly forecasts (which is the only thing I pay attention to re: their weather outlooks/forecasts) is that they are predicting an icebox for February for “The Appalachians,” and a sunbath for March. Details: February will be 6 degrees colder than average, and March will be 3.5 degrees warmer than average. Then again, “the Appalachians” covers a vast and diverse area from a bit north of Elmira, NY all the way to a point SW of Asheville, NC. So we all can take their predictions with a grain of salt the size of the Space Shuttle.
Oh, they actually had a great November forecast {HOW DID THAT HAPPEN??}. They predicted it would be 4 degrees cooler than normal (A+ for that for ROA) and 1 inch below normal for rain (a B, at least they got the dry month correct).
They (OFA) are predicting DEC to be 0.5 degrees colder than normal (if that is to verify, an Arctic outbreak may be required for SW Virginia) and 1 inch ABOVE normal for rain equivalent in the southern Appalachians, which is definitely where ROA and BBURG fit in. January will be normal for both temps and precip (My take on that? “NO WAY!”). FEB will be extremely cold but also very dry (2 inches below normal). That forecast could easily verify, IMHO. That would be DEC 2010 all over again.
I exclaimed “NO WAY” above because I think there is a high probability that the PNA will relent and the NAO and AO will hang negative a bit longer, and JAN will be quite cold. Either that or a freak will occur and the NAO will do an unexpected flip to +, causing warmth. I just don’t see JAN being close to normal for temps here.
Sorry to again divert the discussion off of VDOT stuff, but there were badly blown forecasts all over the place for ROA today. I think WDBJ7 was forecasting a high of 59, WSLS had the same high at least during last night’s broadcasts, and TWC also had a high of about 59 or 60. Actual high? 51. You guessed it, an east wind and some cold-air damming. According to WDBJ7′s 5 PM weathercast, it was in the 60s at that time in Wytheville and Bluefield. Were they speaking the truth, Rick?
I worked for VDOT for a few years, and one year pushed snow in Pulaski County since I had my CDL (had been a part-time bus driver while in college). I’m also a transportation/traffic engineer with a decent educational background in asphalt pavement design…so while I missed the original questions (though I’ll try to find them), I’d like to throw out my thoughts.
VDOT has worked with Virginia Tech at the VTTI/Smart Road on some in-road sensors that can relay quite a bit of information back to a central location. These systems are uber-expensive though, hence why they are rarely used except in some applications on bridges where freezes and ice-ups are a common problem. The issue with in-road sensors are that the traffic driving over them will eventually cause them to fail, especially with heavy truck traffic. Cars don’t wear down a road…they weigh between 1-3 tons for almost all passenger vehicles (cars, pick-ups, vans)…while dump trucks frequently weight in at 15-25 tons, and a fully loaded tractor trailer tops out at 40 tons regulated, over that for special permits. Trucks cause a lot of pavement flexing, and that flexing of the pavement makes it difficult to place sensitive equipment in the road bed. Over time, asphalt roads with high truck volumes experience all manner of deformations: shoving, rutting, cracking, potholing, etc. That’s also part of why VDOT and many localities no longer use in-road inductive loop sensors at traffic signals, and instead now prefer overhead video detection cameras.
When I pushed snow out of the Dublin AHQ, the supervisor and other staff would drive around and check road temperatures with an infrared thermometer (basically like the one from TWC I got as a gift years ago). They would monitor the air temps, radar, and surface/road temperatures to determine how and when to deploy plow trucks, and to where. For big and expected storms, they would try to call in plow drivers a few hours in advance of the storm, to give them time to do pre-trip checks on the trucks, spreaders, and plows…and to load the plows with the gravel/salt blend. We’d get our assignments and be on our way then (drivers usually had assigned areas they were responsible for, working in 12-hour shifts). Sometimes we’d sit and wait for the storm to arrive, so that when the snow started flying we could hit the road immediately. Other times we’d drive around, checking conditions if things were spotty rather than a large, well-organized storm.
We were directed to try to use as little of the salt/gravel blend as possible, so as to not waste precious materials…but also because quite often they weren’t needed until snow rates picked up…in which case prior applications of salt and gravel would get flung off the road when the plow blades were down…negating previous efforts. It was a fine balancing act to determine how fast the application rate should be, when to drop the blade, and when to let nature and traffic help the process. The pre-storm brining that is done can really help with smaller and lighter events where the rate of snowfall doesn’t exceed the chemical melting ability of the salt, but most moderate snows are simply too much for that to work in most cases.
It was a great learning experience to work with those guys in the winter of 2004-05. During my time at VDOT I worked with practically every division, getting a feel for the work they did…but my time with the maintenance folks and pushing snow were among the best and most informative. And being a weather geek I was watching things with a much different eye then because the work I was doing was more directly impacted by the weather than any job I’d worked previously, except perhaps when I did golf course maintenance.
John ..
thanks for that real life insight.
I used to work in material testing (aggregates, concrete.)
Have for the last 25 years been in commercial aviation.
(think aircraft braking on snow covered runways)
What I suggested was not having sensors in active roads..
but to have them in adjacent areas as test pads..(areas with the same ambient temperatures).
(I also used to test concrete test pads placed onsite)
Measuring temperature on a traveled road wouldn’t be accurate
anyway , as its heated by the traffic traveling over it.
I’m just thinking of ways to both benefit the public..
and at the same time further meteorological data gathering.
Granted..not out of the box thinking..as I have no knowledge of Techs work ,,and have been out of the area long before the Smart Road came about.
I know its a week away but what is the initial forecast for the Stagg Bowl on Dec 14th? We can usually count on bad weather on Stagg Bowl day.
Excellant eval and description of the snow dog work Other John. The balancing act is always the key to real success. Most folk don’t appriciate how much thought goes into the planning and exicution of snow removal or ice management.
41* at midnight, 56.7* now.
I don’t have time right now to look at all of your comment, OJ, but it looks interesting. I will read it later today.
41* here and cloudy, sort of damp air for a change, no wind that I could feel.
Ok everyone….let’s take a deep breath and exhale…
If you haven’t heard by now, the “Weather Weenies” have cancelled winter officially after the Saturday 0Z GFS & Euro ensembles came out this morning. If you go over to Americanwx, they are all in “Mayan Calendar End of the World” mode saying that the pattern change will not occur until January.
As in the words of the EPSN Monday Night Pre-game crew….”C’MON MAN!!!”
Yes, the 0Z ensembles are Awful Arthur’s but it is only 1 run. If this trend continues, then maybe. I’m not buying it and neither should you.
Scott Saunders…I hope that I am not one of those “hypsters” you were ranting about on DT’s FB page. I try to make my site as real as it gets without the BS and lots more fact. It’s another reason why I hang out here. KM keeps it real.
Let’s see what the next few days say. In the meantime, enjoy the weekend!
Peace out! Quags
Haven’t seen these ensembles yet, Quag. But I don’t think it’s out of line at all for the pattern to take til January to entirely change. PNA- is stubborn.
very stubborn indeed is the -PNA.
Even worse is the Saturday 12Z GFS & Euro operational runs.
Not good. Looks like Sam Oakey & Doug are working overtime
with the latest model runs. Sorry Snow Lovers but looks like the
pattern is not changing anytime soon. Still have Jan & Feb.
No…Quags, was in no way, shape or form talking about or insinuating you with the “winter is over” hype. I was talking about Accuweather, many…many of Dave Tolleris blogger comments from all kinds of people going on and on incessantly about the models NOT knowing a thing of what they talk about. You, Kevin and Dave know your stuff! I even complimented Dave and Kevin on their astute abilities of predicting long range forecasts. People on there asking Dave, when is it going to snow in Connecticut, when is it going to snow here or there….how much…I was like ENOUGH ALREADY! DT is not the GOOD LORD above, how does he know when it’s going to snow weeks in advance. I was mainly railing against some of the incredibly ridiculous questions he gets and thats were my sarcasm was reflected in the end statement asking when is Greater Roanoke going to get snow, exactly how much and will there be virga. I must admit, the constant weather jargon…PNA, NAO, etc….confuses me a bit, but some people on there ramble on and on and DO NOT know what they say…you, Dave and Kevin do!!
Pattern looks VERY active across nation next couple of weeks as Arctic air and mild flow get in a massive fight. Operational models can’t decide where to place the storms run to run, varying 1,000 miles sometimes.
Probably no immediate fun for SW Virginia snow lovers, but our chances to quench the drought some are going to improve as some of these storms scoop up Gulf moisture.
Just knew this was going to turn into last winter! We can start the pattern change will be next week and then well its going to be another month montra! Wow, incredible how things just repeat itself sometimes. Guess I better go load up on the chill pills! Looks like I’m going to need them this winter! LOL
Pattern change is starting next week, Jared — it’s just not going to be a snowy pattern on your doorstep.
There’s really not much new here. Arctic air punching south at times to collide with the mild pattern and firing up storm systems over the next couple of weeks. That will be a different weather pattern than the placid, mild one we’ve seen. Just not known how long this will play through to whatever’s on the other side.
If we get to Feb. 8 and it’s still looking like this for the next 2 weeks, I’ll warm up to the “just like last winter” talk. On Dec. 8, it’s just too early.
In the meantime, let’s see if we can get some respectable RAIN in here with one of these storm systems to ease this drought. A couple of inches of rain will do us a lot more good than 6 inches of snow would right now.
Yes Kevin, a couple inches of rain is sorely needed. Let’s hope it makes it here and does not jump the Blue Ridge or split and go around us. I agree with you too that if it gets to Feb. 8 and it is still like this then we might as well call this winter a wrap. Let’s hope that when Feb. 8 arrives, we have had some replenishing moisture ie. rain.
Unfortunately … doesn’t look like the next system Monday is gonna be that kinda rainmaker here.
Joe, I’m onboard with ya.. I’m a concrete supplier here in Rocky Mount. Funny how I became a weather fan, but it’s mostly because I need to know when a truck may get stuck in the mud, a finisher may get caught in the rain, or freshly poured concrete may freeze and ruin. Funny how a job can lead to a weather hobby!
Jared, Jared, what are we going to do with you?? Just teasing you.
Did you see my comment on either Wed. evening or Thursday? Denver reached 69 on Wednesday, 53 and 52 for yesterday and today, but tomorrow morning’s low? How does a low tomorrow morning of 9 degrees with light snow sound for a “PATTERN CHANGE??!!” High tomorrow of only 18 with some very light snow still possible, north winds 5-15. Luckily the Broncos played Thursday night.
It will warm back up by Wed. to a slightly warmer than normal high of 47, but back down they go, to 43 on Thursday (just about normal high) and 40 and 38 for next Friday and Saturday. (All that was from wunderground)
You didn’t really take your chill pill, did you? Either that, or you need a stronger dosage. Kevin, please help him out.
Other John, what a fascinating comment late last night!! What a wonderful background you have! Gosh, when I am concerned about what the road situation is likely to be for winter weather conditions, I’ll just get in touch with you.
Quags, in your 3:04 comment you are giving my most valuable snow hater Sam Oakey and I too much credit (or blame) for all this warmth. Sam is still in “comment hibernation” here, and I have been one of the most bullish commenters here on a much colder than normal remainder of winter. And I still firmly believe that. I’ll stop believing it when the NAO goes + and shows signs of staying there or neutral.
Matt…
Funny you say that..
Its all science you know!!
Concrete and aggregates were
where I learned a lot about testing.
We would always sample sand and the larger
stone at the stockpile and again at the batch plant
to make sure it was within specs. The job I was on
manufactured its own sand. The sand plant ran 24 hours a day.
When I moved to the batch plant much the same but larger aggregate.
Our delivery point was far away and one site was on top of a mountain.
We had to put a little less water and quite a lot of ice in the mix
to keep the mix from beginning to set while in transport.
Remote job..but one of the most fun of my life there in Va.
Then there was being underground with diesel fumes and dynamite blasting! Weather seems to be involved in a heckuva lot of jobs.
Can anybody spot the low pressure in South Dakota?
http://hint.fm/wind/
… and there’s a blizzard raging just west of it.
I just looked at the current drought monitor map, and then clicked on Virginia, and as we all know it ain’t pretty. By doing that, the Univ. of Nebraska – Lincoln folks have a chart showing what the drought situation is and has been statewide. One year ago 100% of the state was drought-free, not a single area was even “Abnormally dry.” On 1-1-12, a tiny 1.56% of the state was in D-zero, Abn. Dry.
On the Sept. 25th map, 54.3% of state was not in any drought, but of course 45.7 was at least D-0, and 12.2% was in D-1, Moderate Drought.
Now? Only 36.3% is drought free (Northern Virginia, eastern Virg. and the counties that border Kentucky). 28% is D-0, and an alarming 35.7% is in D-1, Moderate Drought. Including Roanoke area, Montgomery County, and Patrick, Floyd, Henry, Franklin, Bedford, and Pittsylvania Counties and City of Lynchburg, to name the places closest to Roanoke.