Snoverkill kicking into high gear

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Snow has rapidly developed over the region over the last several hours and is sticking everywhere. Anywhere from a heavy coating to 1-2" (highest amounts south and to the northwest) has already accumulated throughout the area. Moderate to sometimes heavy snow will continue for the next several hours. South and east of town, some sleet may mix-in, but the predominant precipitation type should be snow.

Radar does indicate that snow decreases in coverage and intensity to the west and southwest of Fairfax County, but there are indications that may fill-in, keeping the snow going...even if it lightens in intensity or becomes more intermittent. The steadiest and heaviest snow will likely fall along I-95 and to the north and northeast of the District. By 11 p.m. -- the time of our next update -- most spots in the metro region should have 2-4" or so of new snow on the ground.

We are sticking with our accumulation map issued yesterday evening for storm totals. Refer to Ian's post from earlier for the outlook for later tonight and tomorrow.

How much new snow have you receive and what's it doing at your house? Let us know in the comment section....

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Winds pick up tonight, gust to around 50 mph on Wed.

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Snow is a bit delayed but it will not be denied and neither will the big winds of Snoverkill. The storm's effects will begin to be felt across the area through evening as precipitation breaks out. Some sleet is possible early as far north as the entire D.C. metro before everyone goes back over to all snow during the late evening or overnight. The heaviest snow of Snoverkill looks to come during the early-morning through midday tomorrow as winds increase, causing near-blizzard conditions throughout the day.

Radar: Latest regional radar shows movement of precipitation over past three hours. Powered by HAMweather. Refresh page to update. Click here or on image to enlarge. Or see radar bigger on our Weather Wall.

Through tonight: Snow and sleet showers developing this evening consolidate into a general area of light to moderate snow into the night. Some mix is possible across much of the area early, still favoring D.C. and southeast, but we should flip over to snow within a short window around midnight. There may be some lulls in activity late with snowfall rates picking up again near sunrise. Lows range from 20 to 25 with winds increasing by morning.

Tomorrow (Wednesday): Snow and blowing snow is the big story of the morning and very strong winds tell the tale of the afternoon. We should see a band of moderate to heavy snow swing through the area through midday before precipitation tapers late. Winds increase throughout the day and gust as high as 50 mph during the afternoon, causing reduced visibilities, drifting of snow and power outages. Highs should rise to the upper 20s and around 30.

Tomorrow night: Any lingering evening flurries or snow showers should depart early. Skies clear thereafter and winds slowly diminish, but still gust to around 35 mph. Lows mainly in the low-and-mid 20s.

Total accumulations: We still expect accumulations to range from 6-10" across much of the area with a band of higher snow totals ranging from 8-16" focused on the northern portion and northeast. The highest accumulation potential is up toward Baltimore and northeast. See our accumulation map.

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Snoverkill's worst impacts expected tonight & tomorrow

2:10 p.m. Update: Radar is still pretty quiet around the region. However, precipitation should blossom by late afternoon or evening. As we mentioned earlier, any precipitation through afternoon should be on the light side and looks to be scattered, with not much accumulation until after sunset. Next full update between 3 and 4 p.m.

*** Latest accumulation map, storm timeline and FAQs ***

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We know there are some widely divergent accumulation forecasts out there, and depending on where you are in the metro area. But as of the latest information coming in this morning, we are staying pat with our forecast of 6" to 16" for the metro area (see our accumulation map to see what part of that range applies to your location). We expect the highest amounts to be north and east of D.C. toward Baltimore.

The calm before the next storm at the National Cathedral yesterday afternoon. By CWG photographer Ian Livingston.

Now through tomorrow: We still expect snow, or a snow/sleet mix for D.C. and points south and east, to begin from southwest to northeast over the next several hours. But precipitation should be on the light side to start, possibly moderate at times, and may be scattered, so accumulation by sunset should be around an inch or less. The heaviest precipitation is expected this evening through tomorrow morning, and may not taper until later in the afternoon. Strong winds tomorrow are likely to down trees and power lines, so widespread power outages are quite possible.

Uncertainties: The models we use to help guide our forecasts are not in as much agreement as for the last storm. With that in mind, there's still some uncertainty to the forecast. Here are our accumulation probabilities as they stand now:

25%: Less than 6"
35%: 6-10"
30%: 10-16"
10%: 16"+

(Again, accumulations are likely to be toward the higher end north and east of D.C. and lower south and west.)

Stay tuned for more updates later today.

Snoverkill: 6-16" of snow and powerful winds

(next update ~11 a.m.)

* Winter Storm Warning thru Wed for most of metro area (map) *
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Today's Daily Digit

 

A somewhat subjective rating of the day's weather, on a scale of 0 to 10.

 

Wednesday should be worse, but we'll be dealing with a mess by late afternoon again.

 

Get tomorrow's 'Digit' on Twitter tonight

EXPRESS FORECAST

Today: Mostly cloudy, snow and/or sleet developing from mid-day into the afternoon. 29-32. | Tonight: Snow likely. 26-29. | Tomorrow: Snow continues into afternoon. Windy. 26-29. | A Look Ahead | Get Express Forecast by E-mail

SETTING THE SCENE

More snow is on the way today into tomorrow as the latest in the series of storms batters the region. Our incoming storm will come in two punches...one this afternoon into tonight and another tomorrow. The first punch will bring snow this afternoon and tonight, which may mix with sleet from D.C. and to the south and east. The second punch will deliver the stronger blow as very gusty winds bring the potential for blizzard conditions, and unfortunately, power outages. Keep your chin up and realize that if we can get through the next two days, it looks as though we'll have an extended break from winter storminess for at least the next week or so.

ACCUMULATION MAP AND TIMELINE

11 AM to 3 PM TUE
Snow develops SW to NE. Possible sleet S & E. Temps 28-31.
3 PM to 8 PM TUE
Snow, possible sleet S & E. Temps 27-30.
8 PM to 1 AM WED
Snow. Temps 26-29.
1 AM to 6 AM WED
Snow, especially north. Temps 26-29.
6 AM to 12 PM WED
Snow increasing, possibly heavy. Windy. Temps 26-29.
12 PM to 6 PM WED
Snow tapering to flurries. Windy. Temps 27-30.

Forecast Confidence: Medium

IMPACT FORECAST

StormCast

TravelCast

SchoolCast (Wed.)

FedCast (Wed.)

STORM FAQs

Radar: Latest regional radar shows movement of precipitation over past three hours. Powered by HAMweather. Refresh page to update. Click here or on image to enlarge. Or see radar bigger on our Weather Wall.

Where is the precipitation now? Check out the national radar for a wide view of the storm. Monitor its approach using the regional radar to the right. Note, parts of the leading edge or precipitation shown on radar may be virga, which is precipitation in the air that is not yet reaching the ground.

When will the precipitation start again? Start time will be most likely be from around midday to mid-afternoon. The precipitation will move in at a fairly rapid clip from the south so we could see snow arriving in the southwest suburbs late morning to noon and the northeast edges of our region by 3pm. Sleet may mix with the snow especially from downtown D.C. and to the south and east.

Keep reading for more FAQs. And if you haven't already, join us on Facebook and follow us on Twitter. Just found us? Visit us 24/7 -- rain, snow or shine -- at washingtonpost.com/capitalweathergang.

More than 12" possible in places; gusty winds

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* Making history? | Today's Q&A | Snowmageddon's incredible output *
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CWG team snowfall forecast for Tues.-Wed. Confidence: Medium.

In many other winters, you might log on the evening before a storm to find us hedging or trending down from an earlier accumulation forecast. Not tonight, and not this winter. The winter of 2009-2010 just won't stop. Its next episode (shall we call it Snoverkill?) arrives tomorrow with more snow (possibly mixed with some sleet, mainly D.C. and south and east) and eventually gusty winds. The end result is expected to be another major snowfall with metro area accumulations from 6" to 16".

FREQUENT QUESTIONS

Could it be more or less than you're predicting? Confidence in this forecast is not as high as for the last storm, mainly because of uncertainties in when and where the storm will intensify as it moves up the coast. If it intensifies further south than we currently anticipate, then totals could be higher. If it intensifies too far north, however, then totals could be lower. Here is our full range of accumulation probabilities:

20%: Less than 6"
35%: 6-10"
35%: 8-16"
10%: 16"+

When will the snow start? Snow (possibly mixed with sleet at times, especially from D.C. toward points south and east) could start as early as around noon tomorrow, but would probably be on the light side through late afternoon.

When will it get really bad? Snow, or a snow/sleet mix especially for D.C. and south and east, is likely to become moderate to heavy in the evening and probably stay that way through Wednesday morning.

When will it end? Best estimate is around late afternoon Wednesday -- later north and east.

How bad will the winds be? During the day Wednesday, sustained winds may reach 25-35 mph, with gusts to near 45 mph possible. Assuming there is still snow falling, this could create blizzard conditions, and would likely take down some trees and power lines.

What about other forecast details? Highs only get to the upper 20s to low 30s tomorrow, and stall in the 20s on Wednesday. See Jason Samenow's forecast for Thursday through the weekend.

What if my power goes out? Power outages are again a major concern when considering the snow left over from the last storm, the new snow about to come and the strong winds expected with it. To prepare, here are some some tips from followers of our Twitter feed:

@Melvin_Frohike : battery powered "lamp."

@Sunfire2109: Write down the power co numbers NOW. I just lost power for a little while and realized I hadn't copied them.

@soleysomma: beyond obvious (batteries,flashlight,etc) warm blankets&clothes,radio,items for kids,charged portableDVD,carphone charger

@omgapony: Chrg phones, have battery op lites(not just flashlites), have canned food & manual opener, outdoors is a good fridge if nec

@brucecarton: Firewood

@sonjasugira: batteries. blankets. bread. and wine to stay extra warm.

@mamory: firewood, heat packs, and a big essential - a car charger for your iPhone!

Any other safety/preparedness tips? It wouldn't be a bad idea to shovel at least some of the snow off your deck or balcony (if you have either). And watch out for those ice dams!. Dr. Gridlock has the top 5 driving hazards, and check out these winter weather driving tips. Do you have a good safety/preparedness tip? Feel free to share with the group with a comment below.

When's your next update: 5 a.m. tomorrow.

SchoolCast (Tue.) FedCast (Tue.)

What do you think about all this snow? Love it? Tired of it? Let us know, or start a different conversation, with a comment below. And if you haven't already, join us on Facebook and follow us on Twitter.

*** Latest storm update: S'now joke: Another major storm coming ***
(next update around 11 p.m.)

* Federal government closed tomorrow: Federal Eye *
* Winter Storm Warning Tues.-Wed. for most of metro area (map) *
* Making history? | Today's Q&A | Snowmageddon's incredible output *
* Watch out for ice dams | Measuring Snowmageddon's depth *
* Power outage maps for Dominion Electric | Pepco | BG&E *
* Outside now? Radar, temps & more: Weather Wall *
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As our previous update indicates, we're calling for 5-10" in D.C. and to the south and west, and 8-16" to the north and northeast for the upcoming storm. Our accumulation projections are less than the National Weather Service's (10-20"), Topper Shutt's (1 to 2 feet), Doug Hill's (12-16"), and Bob Ryan's (8-12"). The reason for this is that we see the possibility of a dry slot impacting southern half of the metro region. Having said that, we're going to analyze some data coming in between 9 and 11 p.m. tonight and will adjust our accumulation map in our 11 p.m. update as necessary.

Before we do so, it's your chance to weigh in by indicating how much snow you think will fall at Reagan National (DCA), and giving this storm a name. See the polls below....

Blizzard conditions and significant accumulation possible

* Winter Storm Warning Tues.-Wed. for most of metro area (map) *
* Making history? | Today's Q&A | Snowmageddon's incredible output *
* Watch out for ice dams | Measuring Snowmageddon's depth *
* Power outage maps for Dominion Electric | Pepco | BG&E *
* Outside now? Radar, temps & more: Weather Wall *
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There is still way too much snow outside to know what to do with and it is now increasingly likely we will be adding a big pile on top. The National Weather Service has now issued Winter Storm Warnings for tomorrow and Wednesday. As if that was not enough, this looks like quite the windy event, with blizzard conditions possible. Highs near freezing today and similar expected tomorrow will ensure that our snow base at the beginning of the event remains quite deep.

Through tonight: We see mostly clear skies early becoming cloudier as the night wears on. Temperatures fall to near 10 in the coldest spots to the mid-or-upper teens in the warmest.

CWG team snowfall forecast for Tues.-Wed. as of 3:30 p.m. Confidence: Medium.

Tomorrow (Tuesday): The day starts mostly cloudy before snow begins to arrive during midday and afternoon. Snow will pick up in intensity as we head into evening with the heaviest expected late at night and a possible lull prior to sunrise. Some mix with sleet is possible from around D.C. and to the south. Winds increase late at night, with gusts near and past 35 mph -- blizzard conditions are possible by morning. Highs should reach the upper 20s to lower 30s with lows in the low-or-mid 20s.

Wednesday: There may be a lull in the snow, or just some lighter stuff during the very early morning, but a second dose of moderate or heavy snow is possible as the storm pulls off to the east and the upper-level energy swings through. Highs probably rise to the upper 20s most spots. Strong northeasterly winds continue to be a concern through much of the day.

See Jason Samenow's forecast through the rest of the week and weekend.

What do you think about all this snow? Love it? Tired of it? Let us know, or start a different conversation, with a comment below. And if you haven't already, join us on Facebook and follow us on Twitter.

* Serious snow/wind risk late Tues into Wed | Live chat at 2 p.m. *

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Seasonal snowfall over the last two decades. 45" have fallen so far in 2009-2010, the most since 1995-1996.

With the impending storm for tomorrow and Wednesday, we have a legitimate chance for an all-time (since records have been kept in the late 1800s) seasonal snow record.

Our big weekend storm surged Reagan National Airport's seasonal total to 45" with the balance of February and March yet to go. This places our current winter in position number three for the snowiest winters on record, behind 1995-96 (46") and the big one, 1898-99 (54.4"). Of course, that all-time record was set at a more downtown location (M Street), so some may argue the higher elevation and location away from the Potomac was an easier accomplishment. But in my mind, that makes this potential record season all the more notable.

The chart above tracks seasonal totals since the 1990-91 snow season. Just look at that volatility. Get this: our 45" this season is more than the last four winters COMBINED (which was only 35.5").

Keep reading for more on the chances for 2009-2010 to make snowfall history...

Blizzard conditions may return, especially N & E

* Our Full Forecast thru weekend | Snowmageddon's incredible output *
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* Watch out for ice dams |Measuring Snowmageddon's depth *
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This morning's 12z Global Forecasting System model simulating snow over the region Wednesday morning and very strong winds (depicted by the closely packed lines of equal pressure or isobars in black).

The new data we're analyzing portrays a rather ominous picture for the region, beginning tomorrow afternoon. Two areas of low pressure, one from the north and one from the south, will likely merge off the mid-Atlantic coast developing into a very powerful storm Tuesday night and Wednesday. Though this storm will not have the same amount of moisture as Snowmageddon, models suggest a deeper storm (i.e. more intense meteorologically) which will pose a significant risk of high winds and additional power outages.

The probability of potentially dangerous conditions is highest north and east of the beltway and especially as you head towards Baltimore and Philadelphia. However, even our southern suburbs may experience periods of heavy snow and wind.

FREQUENT QUESTIONS

When will the snow start? Between mid-day and mid-afternoon tomorrow.

When it will end? Probably around late afternoon Wednesday -- later north and east.

How much?: Our best bet is 5-10" in the metro region, but 8-14" as you head north and east towards Baltimore. South and southwest of the Fairfax County, 3-6" is most likely.

Could it be more or less? Yes. Double digit totals (10" or more) remain a possibility throughout the metro region (25% chance). By the same token, if the coastal storm forms too far north, lighter amounts from 1-5" or so might do it.

How bad will the winds be? By very late Tuesday night and into Wednesday, sustained winds may reach 25-35 mph, with higher gusts. Assuming there is falling snow, this could create blizzard conditions.

Feb. 3-6, 2010: Simulations, satellites, radars, and maps

*** Remarkable winter brings new threat: Full Forecast ***

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Radar estimated liquid equivalent totals (generally 1.5-2.5" inches of liquid) from the historic Snowmageddon which dropped as much as 2 to 3 feet of snow across the region. Note, radar does not always accurately demonstrate real totals; numbers on the edges of the radar scope are likely underestimated. Image courtesy: Weather Underground.

After Snowpocalypse in December, it would have been hard to imagine it would only end up "one of the biggest" storms of winter 2009-2010. But that was before Snowmageddon came along with its massive amounts of moisture. While the large-scale pattern was similar, and aided us in our high level of forecast confidence that a historic storm was in the offing, the way it came together was a little different. The moisture sources it tapped were far-reaching, ultimately helping it produce historic amounts of snow over the area.

Continue on for more imagery related to the historic February 2010 storm.