Transcript

First Snow: Current Conditons and Forecast

The region copes with the season's first round of sleet, freezing rain and ice after Tuesday's snowfall.

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Josh Larson
Forecaster, Capital Weather Gang
Tuesday, January 27, 2009; 2:30 PM

The first snow of the season blanketed Washington and its suburbs with wet, white flakes this morning, prompting several public school systems to cancel classes and raising concerns of a slick, possibly icy, evening commute.

Forecaster Josh Larson of the Capital Weather Gang, was online Tuesday, Jan. 27, at 2:30 p.m. ET to take questions and comments about the snowfall, the latest weather warnings and advisories and what to expect later today and in the morning.

A transcript follows.

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Josh Larson: Good afternoon! I'm Josh Larson from The Capital Weather Gang. Thanks for joining me, and I'll be happy to take your questions. Temperatures are holding steady in the upper 20s at the moment in most locations. As was previously advertised this morning, we're now seeing a pronounced lull in precipitation. This storm system really has two separate pulses, if you will. The first came through this morning. This afternoon we'll largely be in the middle of the two, and then the second round of precipitation will develop this evening and continue into tomorrow morning. The primary precipitation type through midnight will be snow mixing with sleet, but overnight snow will transition to sleet and eventually freezing rain with temperatures rising slowly to near 32. On to your questions...

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Alexandria, Va.: It seems like the snow has stopped for now (it's 2:06 p.m.). I was planning to leave my office on K Street to head into Old Town around 4:30. Do you think it will be a problem to drive home then or will roads be icy?

Josh Larson: Hopefully during this afternoon's lull in precipitation, the road crews will be out full force. Also, I think the heating (despite the cloud cover) from the afternoon sun will help out. I think we'll only see scattered light snow showers or flurries until early this evening, so I don't anticipate much, if any, new accumulation between now and when you'll be leaving work. Bottom line: I don't think it should be too bad. However, pay special attention to bridges and overpasses as well as secondary roads. Safe travels!

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Silver Spring, Md.: Think the feds will be let out early today?

Josh Larson: I'm far better at prognosticating weather than official government decisions. However, I do not think they'll let out early, especially because of the current lull in precipitation.

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Alexandria, Va.: What can we expect tonight and tomorrow

Josh Larson: Precipitation, mostly in the form of snow or a snow/sleet mix will redevelop this evening and last until the early overnight hours. Sometime around or after midnight, the snow/sleet will transition over to freezing rain, with the SE areas changing over first and the NW areas changing over last. Tomorrow morning's commute could be quite treacherous, with freezing rain probable. Sometime tomorrow morning the precipitation should change to all rain, but the exact time frame is hard to say.

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Arlington, Va.: I've got an 8 a.m. flight out of BWI tomorrow morning. How's it looking for me to get there from Arlington if we leave by 5:30?

Josh Larson: I think road conditions, especially north and west of town, may be quite poor tomorrow. I might even allow for more time than that. Drive safe!

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Government employee: What are the odds the government gets a snow day tomorrow? I'd settle for a late start too.

Josh Larson: 50/50 :)

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Carroll County, Md.: Will Carroll county schools be closed tomorrow?

Josh Larson: I'm not going to predict any closings tomorrow -- especially not for individual counties -- but I will say that I think untreated roads, especially north and west of town, may be quite icy/hazardous tomorrow morning.

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Arlington, Va.: How likely is significant ice accumulation tonight and tomorrow? Should we plan to stay off the roads, at least tomorrow morning?

Josh Larson: The threat of significant icing does loom, particularly in the typically colder north and west suburbs. But I even think downtown DC will have to contend with icing problems, at least on some surfaces. I would try to avoid travel from this evening tonight until late morning or early afternoon tomorrow.

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washingtonpost.com: Metro Closings and Delays

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Falls Church, Va.: Where is this 2nd wave now?

Josh Larson: Over extreme southwestern Virginal, West Virginia, Kentucky and southern Ohio.

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Washington, D.C.: I'm heading out to Dulles to meet a 7 p.m. flight. What to expect, road-wise, do you think?

Thanks!

Josh Larson: Tough to say. Depends when the second round of precipitation begins, which we're not entirely sure on (5-7pm??). Just allow extra time for getting there; I don't think major (treated) roadways will be much of a problem.

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Old Town Alexandra, Va.: Do you think the snow, sleet, and freezing rain this evening and overnight will warrant the federal government to close tomorrow?

Josh Larson: Previously answered: tossup.

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Bethesda, Md.: Which parts of the metro area are likely to be hardest hit?

Josh Larson: As with almost all winter storms in the DC metro area, the typically colder north and west suburbs are likely to see the most icing. Generally, areas north and west of a line from northern Montgomery County back through western Fairfax County can probably anticipate more icing than, say, downtown DC.

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Question about our snow: Can you explain why it so rarely stays cold enough to snow? It seems like we get lots of 20-degree weather, but the instant any precip heads this way, nine times out of ten it warms up enough to be rain or sleet.

Josh Larson: Major storm systems change the dynamics of the atmosphere around them and can create a lot of warm air in the process (warm advection aloft, to be technical). In the winter, generally only areas of low pressure that track south of us, will keep the cold air in place. This wave of low pressure will be moving to the north and west of us, allowing for more erosion of the cold air. I understand your frustrations!

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Washington, D.C.: Josh,

How's the long term forecast (e.g., through Feb.)looking for D.C.? Would you guess this will be our main snow/ice event for the winter, or is this just the beginning? Care to make an educated guess?

Thanks for the excellent site.

Josh Larson: January has been colder than normal, and it's tough -- though not impossible -- to get two back to back colder than normal months (it seems these days) in DC. My hunch is that February will not be as cold as January, but that does not close the door for future winter precipitation events. My gut feeling is that there will be at least one more this winter (after the current system). But don't hold me to it!

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Havre de Grace, Md.: I used to live in D.C. and am still an avid follower of the Capital Weather Gang, even though I am now north of Baltimore. What do you think we'll get in the way of precip north and east of Baltimore? Ice/snow, or will we turn to rain Wed a.m. as well? Thanks!

Josh Larson: Areas north of Baltimore will generally stay in the cold air longer than spots in the immediate DC area. You may have significant icing, which is why a Winter Storm Warning (as opposed to a less serious Advisory) has been issued for your area. You will still change over to rain eventually, but it may not happen until late tomorrow morning...

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Alexandria, Va.: Is driving to Howard County. Maryland tomorrow morning a very bad idea?

Josh Larson: All I can say is that many places are likely to be treacherous tomorrow, especially those north and west of the downtown area.

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Washington, D.C.: I'm confused. What is going to make it change from snow to sleet/freezing rain if the temps remain the same (below 32)?

Josh Larson: Great question! While temperatures at or below freezing (at the surface) will stay with us through sometime tomorrow morning, what's happening is warming aloft. So instead of snow being produced higher up in the atmosphere, warming will change that precipitation over to liquid variety which (if the surface area of cold air is thick enough) will re-freeze to sleet and (if the surface area of cold air is shallow) will freeze on contact. So, it's really what's happening "upstairs" that's dictating the precipitation change rather than what your thermometer might read.

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In the loop: With temperatures so close to freezing, why is it that the snow seems a bit fluffier that I would normally expect? This close to freezing usually produces snow that collects like a pile of wet cement (and makes a darn good snowball, too). What is the snow to water ratio with the storm?

Josh Larson: You're right that the warmer the temperatures the wetter the snow, but it also depends somewhat on the temperatures at other levels of the atmosphere. I would make an educated, though hardly scientific, guess that the snow to water ratios will be around 10:1 or 12:1

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Silver Spring, Md.: Once again it seems we're right on the snow/rain line. It seems to me that it has moved further north (towards D.C.) in the last few years as we used to get much more snow (20 inches or so per season.) Have your weather watchers seen the same thing and is it cyclical?

Josh Larson: Some people have anecdotally reported this seeming northward movement of the "typical" rain/snow line, but I'm not sure that there's any hard/scientific evidence of this -- that I'm aware of, at least.

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Washington, D.C.: Hi,

I'm "essential personnel" at a hospital, so no snow days, ever. If I am scheduled to work I have to be there, as on time as possible. I WISH I got a snow day, but....another way of looking at it is -- when everyone else has a snow day, traffic on the roads is lighter.

Josh Larson: Looking on the bright side of things, eh? Not a bad idea.

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Falls Church, Va.: Statistically speaking, how far north or west of here would I need to move to get a REAL chance of consistent winter snows? (I'm pretty tired of these D.C. winter disappointments!)

Josh Larson: Depends what your idea of "REAL chance of consistent winter snows" is, but probably close to the MD/PA border, or western Maryland, or West Virginia. But some winters we luck out even in downtown DC. So it's hard to say.

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Herndon, Va.: Josh: do you expect rain anytime tomorrow for western Fairfax County? Will the temps hold at or below 32?

Josh Larson: I think all areas will eventually change over to plain rain tomorrow. But you may not change over until mid to late morning, whereas other locations further south and east may change over as early as pre-dawn hours tomorrow.

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Potomac, Md.: I was planning on going to the Maryland game tonight. Do you think it might be better to stay home and watch it on TV? I'm concerned about driving at night on icy roads.

Josh Larson: Everyone's comfort level with driving in inclement conditions varies, but my suggestion is generally to avoid travel, if possible, from this evening through at least mid-morning tomorrow.

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VA to BWI again: Would we be better off going up tonight and staying in a motel? Or will the roads be just as bad tonight? We're off to Jamaica and I don't want to miss my flight!

Josh Larson: Hard to say. All I can say is that roads are likely to be snow covered tonight versus icy tomorrow morning. Driving on both can be dangerous but in my personal experience, driving on ice is far worse than in snow.

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Safe to eat the snow?: So is it safe to eat the snow as it falls, or is it too filled with pollutants?

Josh Larson: Depends how adventurous you are ;)

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Warm advection aloft: Thank you. I have wondered about this for decades, since moving here from the Midwest.

Josh Larson: Glad to have cleared things up for you!

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Rockville, Md.: Hi,

Thank you for all your hard work. Where does the line start when you are referring to northern Montgomery county?

Josh Larson: You're welcome. Unfortunately, it's impossible to pinpoint closer than to say that the further north and west you go from downtown DC, the longer temperatures will stay below freezing, and the more icing is likely. In fact, I'm not even sure the "line" is going to be over northern Montgomery County -- it may be in central Montgomery County -- or it may be even further north and west than northern MoCo. Sorry I can't be any more exact.

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Charlottesville, Va.: When do you think it will be safe to drive up to Fairfax tomorrow from Charlottesville?

Josh Larson: The morning hours may be quite slick. I would think that after noon the vast majority of the area will have changed over to rain and conditions should improve thereafter.

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Josh Larson: That about wraps it up here. Thanks for your questions during this chat; I hope that I clarified some confusions and curiosities. On another note, I'm beginning to think that the second round of precipitation might come a little earlier than expected, most likely before the bulk of the evening rush hour. So drive safe this evening and tomorrow morning -- slow down and leave plenty of space between your car and the car in front of you. Do try to enjoy the snow, too! Keep glued to the Capital Weather Gang for continued around-the-clock coverage. Thanks!

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