washingtonpost.com
Major snowstorm to hit the region

Matt Rogers
Meteorologist, Capital Weather Gang
Thursday, February 4, 2010; 2:00 PM

A major, high-impact winter storm is very likely to strike the metro region with heavy snow Friday and Saturday. This storm has the potential to be as strong as the "Snowpocalypse" storm of Dec. 19-20 earlier in the season. The one difference is that the atmosphere will be modestly warmer this time around, allowing for the possibility that snow will mix with sleet, primarily along and east of I-95. However, the majority of this storm will likely be snow and it is expected that the most probable accumulations will be in the 12 to 20" range or more.

Matt Rogers, meteorologist with the Capital Weather Gang, was online Thursday, Feb. 4, at 2 p.m. ET to discuss the coming storm.

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Matt Rogers: Hi this is Matt Rogers, a meteorologist with the Capital Weather Gang and we're watching this incoming storm very closely. I'm looking forward to your questions.

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Washington, D.C.: With all the hype about the major snowstorm on its way to the Metropolitan area as early as Friday afternoon! Are we actually expecting to get as much as a foot or more of snow? If so, where are the more major areas we should be worried about? For example, I live in Temple Hills, Md., which is a little more southeastern, is that area expecting to be get that much snow?

Matt Rogers: A great place to look is our Capital Weather Gang snow accumulation map at this link http://voices.washingtonpost.com/capitalweathergang/images/feb-06-10_b.gif

We'll be updating that again later this afternoon!

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Washington, D.C.: How probable is it that air travel on Friday morning is disrupted? Do we only need to worry about flights Friday night and afterwards?

Matt Rogers: Yes, I was expecting A LOT of flight questions. My guestimate is that we'll start seeing problems maybe late afternoon tomorrow onward. Prior to that, flights should be ok, but then delays and cancellations will begin to pile on. I wouldn't expect normalcy to return until later on Sunday.

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Takoma Park: The storm is supposed to start Friday morning. At what point do you think we'll see some serious accumulation, or in other words, what time should I leave for home so as to not be stuck at work? Second question, any idea on how much snow we'll get next Wednesday? Thanks.

Matt Rogers: Hi Takoma Park, the timing of the start is a bit in question right now...anywhere from 9am to 1pm around the DC area. With temperatures still on the milder side initially, I believe road problems won't be a concern until late afternoon...maybe toward 4 and 5pm. Next Tue-Wed looks like a lighter event right now, but could still be a number of inches. Wow on this winter!

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Snowmen or Snowdrifts?: Given what we know about the storm, can we expect it to be a heavy, wet snow or a light, dry snow?

I would definitely prefer the latter.

Matt Rogers: I would prefer the latter too, but unfortunately, temperatures look to be warmer than last Saturday's powdery event. I'm afraid this one will be of the heavier, wetter snow variety, especially on Friday and Friday night.

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Reston, Va.: Local forecasters seem reluctant to guesstimate snowfall totals for this weekend. Were you to gaze into your crystal ball, would you predict that this storm will bring more snow, less snow, or the same amount of snow as the December "blizzard"?

Matt Rogers: Good question Reston. I initially thought "less snow", but the guidance over the past 24 hours has been getting wetter and wetter. This El Nino continues to enhance moisture content on these systems. So I think same-or-higher vs. Dec 19th is getting more likely here.

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Alexandria, Va.: We are scheduled to head to Charlottesville tomorrow. We had planned to head out mid-afternoon, but canceled some plans to be able to leave mid-morning instead.

Given that the snow is coming up from the south and therefore the snowpocalypse will start earlier in C'ville, do you think leaving at 11 a.m. gives us enough time to get there before conditions deteriorate too much?

Matt Rogers: You should get there before conditions get too bad...earlier the better!

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Washington, D.C.: Thanks in advance for any advice you can offer re: travel this weekend! I need to get down to Raleigh, N.C., by Sunday night. What do you think driving conditions heading South will be like on Sunday? Do you advise heading out tonight rather than Sunday?

Matt Rogers: I would tend to think tonight is the better option. The storm will be done on Sunday, but travel won't be as nice!

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Alexandria, Va.: It looks like the keep moving up the arrival on Friday. Is mid-morning still the forecast? Will it start lightly or is all hell going to break loose as people try to leave work tomorrow at 2 p.m.?

Matt Rogers: I am on the side of a lighter start and with temperatures right around or even slightly warmer than freezing initially, it shouldn't be much trouble initially.

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Arlington, Va.: With the heaviest snow arriving overnight on Friday night and Saturday morning before sunrise, will the local airports potentially be able to clear any snow during the day on Saturday and allow flights to land even if it's still snowing?

I have a family member with a cross-country flight scheduled to arrive on late Saturday afternoon and I'm wondering if there is ANY chance it will actually happen.

Matt Rogers: The storm should be tapering off on late Saturday afternoon, but my guess is that previous flight cancellations and delays will make the rest of Saturday very messy with unlikely arrivals.

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Front Royal, Va.: I've heard estimates of up to 48 inches of snow. What is the real deal going to be for us in the outer outer burbs?

Matt Rogers: The highest I've seen on model guidance is 37" out toward Delaware...but that model tends to overdo precipitation. Haven't seen anything pointing toward 48". That would be epic. I don't believe it.

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Arlington, Va.: Hi Matt,

For a typically snow-starved region like D.C., getting all this snow this winter is just wonderfully refreshing! Love it! What factors are contributing to so much snow this year?

Matt Rogers: I've been in DC since spring 1994 and this one is making a run at my snowiest winter here. If we get 20" this weekend at DCA, we'll surpass the modern day max season (95-96...remember that one!?). Two major factors here: El Nino pumping north huge amounts of moisture and Blocking over the North Pole sending persistent cold southward. They seem to really want to meet over the Mid-Atlantic this year.

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Wind?: How bad is the wind supposed to be? Seems to me, wind makes a big difference in storms?

Matt Rogers: Excellent question. The wind is going to be howling toward the Eastern Shore on this one. We should see higher gusts at times late tomorrow night into Saturday, but it may not be as windy as the Dec 19th storm where we saw a Blizzard warning go up...this is something to watch though...especially with a heavier wetter snow on tree branches potentially.

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Union Station, D.C.: On looking at the snow band forecasts, it clearly shows the city in the middle of the largest snow total band (12-16 inches +) but it also looks like the band is pretty narrow and with a little movement we're in 6-12 inches. In fact we're not that far from the 3-6 inch band. But everyone seems to only be calling for the upside number.

Matt Rogers: Check here for our latest thinking: http://voices.washingtonpost.com/capitalweathergang/images/feb-06-10_b.gif

The bands are much broader I think. We may be increasing the low end range some more in our afternoon update after 3pm.

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Alexandria, Va.: Ugh. When will all this snow go away? I heard there is another winter system on its way. Is that expected to bring more snow?

Matt Rogers: Sorry. February is usually our snowiest month in DC and we've just started it. The next storm is looming for Tue-Wed and the models are oscillating on details yet. My first impression is that it will be more like last Saturday's event, so not as big of a system. We'll watch it closely on the Capital Weather Gang blog!

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Columbia, Md.: Matt,

How quickly will the snow fall? Are we looking at most of it coming in at once, or steadily over two (or three )days?

Thanks for taking questions today!

Matt Rogers: Hi Columbia MD, we should see the snow mostly on the lighter/wetter side on Friday with limited road troubles until evening or late afternoon approaches. The heaviest accumulations are overnight Friday into early Saturday morning. A secondary upper level low should continue the snow, maybe moderate at times during Saturday. But we should taper to flurries late Sat afternoon or evening. And then we get a timeout.

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Silver Spring, Md.: Update -- OPM has just announced Unscheduled Leave policy in affect for Friday and Monday.

Matt Rogers: Thanks Silver Spring!

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Rockville, Md.: When are school systems going to start cancelling class? Do you think the fact that most systems have used all their snow days will effect how they make this call?

Matt Rogers: That's a good question. Unless the hype scares them, I don't believe the roads will be a big problem until late afternoon tomorrow.

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washingtonpost.com: Latest Predictions

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Washington, D.C.: Hi,

If it is a wetter snow, are we more likely to lose electricity (since it would be heavier on the power lines?)

Matt Rogers: Yes, I believe that is a bigger concern this time, particularly if you get that heavier snow in addition to higher winds late tomorrow night into Saturday morning.

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Arlington, Va.: Do you think this snowstorm will be strong enough to shut down Metro entirely (including the underground stations)?

What do you predict for Sunday Metro and road travel?

Matt Rogers: I know there is a rule about 8" or more shutting down the outside tracks/stations, but not sure about the underground ones. There may be short-staff issues if we get the maximum totals expected. Tough to say.

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Rockville, Md.: Are we going to have any melting post-storm or are any accumulations we get next week just going to add on to what's on the ground from this weekend?

Matt Rogers: I think we'll see some melt opportunity Sunday and Monday during the day, but with these high totals expected, probably not enough!

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Philadelphia, Pa.: Planning to visit D.C. this weekend for the Georgetown/Villanova basketball game (Go Nova!). We can't leave Philadelphia until around 6 p.m. Friday night, is there any hope we'll get there in one piece?

Matt Rogers: If you're driving, be very very careful. I wouldn't recommend it...could be a very long night!

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Arlington, Va.: Hi folks,

Absolutely LOVE the CWG blog. My question:

If you had to choose ONE NUMBER (not two numbers with a hyphen), what would be the absolute MINIMUM amount of snow we can expect to get from this storm that you feel comfortable saying? 8 inches? 10?

Matt Rogers: Good question, thanks for the CWG compliments. My personal "floor" on this one is probably 12". The two "surprise" risks could be storm shifting south suddenly shifting the heavier snow route south of us or the storm coming too close and giving us more mixed precipitation. The modeling has been remarkably consistent on producing the heavier totals the last 24 hours, so my "floor" may go up to 15-16" soon!

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McLean, Va.: Thanks for the great coverage... big ups to the CWG!

For us budding weather geeks, are there any public/open source data feeds and models available for us to play around with? What data do you guys typically use? How does one start becoming an amateur forecaster?

Matt Rogers: Well, for one thing, keep following us on CWG! I'll be doing a post early next week to describe the weather pattern and how we're getting all this crazy snow. When forecasting tough weather like this, we need to look at all available guidance, so we tend to look at every model we can, but also use our understanding of synoptic meteorology to figure out what is the most reasonable option. I also believe in using past events as guidance and analog for upcoming ones. It's the only way we learn. This answer was too long. Sorry!

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Solomons Island, Md.: Are we going to be seeing an ice mix in lower Calvert?

Matt Rogers: I believe you have a much better chance of seeing that mix down your way which will cut down your overall snow totals by some amount. But the storm track appears far enough south that snow will outweigh sleet/ice on this one.

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Springfield, Va.: Since we had the "Snowpocalypse" storm of Dec. 19-20, do we have a name for this one yet? Snowicane? Snowphoon? SoSickofSnowSuperBowl? Snow Hog Day 2010?

Matt Rogers: Haha, yes, we need to work on that. Go to Capital Weather Gang's blog...here is the link...http://voices.washingtonpost.com/capitalweathergang/2010/02/poll_storm_nametwitter_hashtag.html#comments

They are trying to figure the name our Right Now!

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Abingdon, Md.: When was the last time this area received two big snowstorms (15"+) in the same season? That would seem to be unprecedented. I know 95-96 was bad, but I only remember one really big storm that year. Typically we only get "big ones" once every four years or so around here.

Matt Rogers: This is the subject of another blog posting...it has happened before, but not many times...http://voices.washingtonpost.com/capitalweathergang/2010/02/as_we_edge_closer_to.html#more

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Reagan National: Most airlines have now CANCELED flights starting around 12:30 p.m. Friday through early Sunday morning. So anyone with flights in that window should check with their airlines IMMEDIATELY.

Matt Rogers: Thanks. Everyone is getting ready it seems.

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washingtonpost.com: Name the Storm

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Question: What is "blocking over the north pole?"

Matt Rogers: Good question. When you have a blocked jet stream pattern up there, it means you have lots of high pressure that is pushing cold air down and away from the Pole toward the mid-latitudes where we live. We have had enormous blocking this year (strongest December on record), which has brought cold to Europe, Asia, and us.

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Woodley/Cleveland Park: I'm thinking about making a weekend trip up to CT this weekend to (ironically) avoid the snow.

Two factors weighing on my decision:

1) What time do I need to leave the city by in order to be free of road issues.

and

2) Will the roads be well enough on Sunday for me to be able to return? I do have to work on Monday.

Thanks!

Matt Rogers: Escaping a historic storm!?!? Oh well, I'd leave tomorrow after rush hour. Sunday return could be tricky, but afternoon/evening is your best bet on Sunday.

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washingtonpost.com: Double-digit snows twice in one season: a rarity (Capital Weather Gang, Feb. 4)

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Washington, D.C.: Hi Matt, Do you expect thunder snow with this system?

Matt Rogers: We do tend to get some thunder and lightening with the heaviest winter storms, but I believe the main low pressure will be far enough outside our area to avoid it this time. They have a better chance of that on the Eastern Shore.

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Alexandria, Va. : Dude, Where's My January Thaw?

Matt Rogers: Last month, Dude. We had a high of 67F one day. Seems so long ago now!!

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Rockville, Md.: Blizzard warnings now issued for parts of Delaware and southern Jersey.

Matt Rogers: Thanks. That makes sense. This storm is going to explode off the Delmarva coast and high winds will be a bigger problem over there.

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Volume of rain vs snow?: How do you calculate how much snow, or rain, we'll get? I was in a flooding rain in N.H. one year, and they said that if it'd been snow it'd've been 14 feet -- which made a foot and a half of rain look much better. How could you figure that out?

And how do you tell what kind of snow we'll get -- heavy and wet, light and fluffy, or in-between?

Matt Rogers: Precipitation type is always tricky. One has to consider so many factors and the entire column of air above us. Right now, our surface temperatures will be closer to the freezing mark initially, so at least the first half of the storm could be the heavy wet variety. That is what makes me more worried about power outages compared to our previous snows this winter.

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Colleges are cancelling games: For the Phila person driving down -- check to see if the game is still scheduled before making the trip. And if you do travel, please be sure you have all the emergency winter gear you might need with you in case of trouble en route.

Matt Rogers: Good points!

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Mt. Vernon, Va.: Heavier north or south of town? (My location clues you in as to why I'm asking.) Or, consistent throughout the region?

Matt Rogers: Usually with coastal storms, the western suburbs see heavier totals due to some "upslope enhancement"...otherwise, slightly higher elevations west of the fall line. But this storm track should suggest we don't see as much of a gradient and Mt. Vernon could very well also be on the high side of our forecast range.

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Groundhog Hole, Puxatwaney, Pa.: Seems to me that by President's Day, winter here begins to wind down. Of course, President's Day is a little earlier this year than most, thanks to the first being a Monday. Any prediction as to when we will finally see temperatures moderate?

Matt Rogers: Good question. This cold pattern developed at the very end of January and early February. Usually, blocking-based patterns like this one can last for 4-6 weeks, so unfortunately, we may see more cold than warm weather through Feb and into a decent chunk of March yet. :(

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Brookland - Washington, D.C.: What constitutes a blizzard vs. a heavy storm and what do you think the chances are that this storm is categorized as a blizzard?

Thanks!

Matt Rogers: Wind is the answer. When winds get above a certain threshold, it is considered a blizzard. To be honest, I cannot remember the exact threshold, but high and sustained winds are the qualifier. I believe the Eastern Shore will see the biggest blizzard conditions on this one.

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D.C.: When do you think Metro will close its above-ground stations? Thanks.

Matt Rogers: Based on their 8" rule, maybe between 7-10pm tomorrow night?

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Anonymous: OH, my. The NWS just upped the possible start time to 6:00 a.m. and is estimating 20-28 inches possible. NOAA.

Matt Rogers: Wow! They are more confident than we are. I agree there are models at this level and we need to be prepared for that, but there are still risks to this forecast. We all know about last minute forecast surprises from this past week (last two storms). Also, that start time is much too early in my opinion.

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Falls Church, Va.: Is there a general conversion rate for inches of rain to inches of snow? That is if 20 inches of snow accumulate in this storm, what would the equivalent be in inches or rain? I imagine it depends on light or heavy snow, how soon it begins to accumulate vs. melting on contact, etc., but is there a rule-of-thumb on this?

Matt Rogers: Good question. It varies depending on temperature...usually you think about an 8:1 ratio, but we can get as high as 10:1 or even 12:1, which I think happened last Saturday. Essentially, the drier the air, the higher the ratio. My guess is that if have 1" of liquid equivalent, we'll get 10 inches of snow. The current models are as high as 2-3" liquid inches so the ratio makes a big difference. The warmer temperatures argue for a 10:1 or 8:1 ratio.

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Anonymous: Please, please, please weather guys, don't tell anyone to stay inside. We should all get out and shovel our walks, our neighbor's walks, the bus stop and the nearest mailbox. Then take a walk and check out the neighborhood businesses -- buy a paper and a cup of coffee at least. This is just weather, not the end of the world.

Matt Rogers: Good point!

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Damascus, Md.: Is this winter's total snowfall and bitter temperatures just one of those statistical "jags" that we hear occur from time to time, or can it be attributed more to global climate change and this is what it will be like for winters to come?

Also, has anybody else noticed that there are a lot of robins around this winter? I've seen quite a few (even this morning) in the Gaithersburg/Damascus area despite the snow and cold. Is climate change having a big effect on bird migration?

Matt Rogers: I've posted about climate change before and I am more in the skeptical camp about long-term climate projections. Climate has and always will change though. I'm sure we can all agree on that!

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Matt Rogers: Thanks everyone for your excellent questions. I have to get back to work now. Be careful this weekend!

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