Heavy snow tonight, then mixed precipitation Thursday (LIVE FORECAST UPDATES)

Snow will be heavy at times across the D.C. area over the next few hours, and will pile up very quickly, making travel dangerous to impossible. A special weather statement just issued from the NWS cautions:

A BAND OF HEAVY SNOW OVER THE VIRGINIA PIEDMONT IS EXPECTED TO OVERSPREAD THE WASHINGTON METROPOLITAN AREA BY 2 AM THIS MORNING. THE HEAVY SNOW WILL OVERSPREAD THE BALTIMORE METROPOLITAN AREA BETWEEN 2 AM AND 3 AM THIS MORNING.

HEAVY SNOW WILL PERSIST FOR A COUPLE HOURS WITH VISIBILITY REDUCED BELOW ONE-QUARTER MILE. SNOWFALL RATES OF ONE TO AS MUCH AS THREE INCHES PER HOUR ARE EXPECTED UNDERNEATH THIS BAND. TRAVELLING WILL BE VERY DANGEROUS DURING THIS TIME SINCE ROADS WILL BECOME QUICKLY SNOW-COVERED.

No matter where you are in the area, you can be assured you will wake up to a winter wonderland, even though some places may be mixing with sleet and rain by dawn, especially from around D.C./I-95 toward the east. But keep in mind that those areas that change-over may change back to snow tomorrow afternoon.

Stay home and stay safe tonight. This is the last entry for the live blog for now. But we invite you to keep the conversation going in the comments section of our most recent Capital Weather Gang post right here. Thanks for joining us, and live coverage will resume at 5 a.m.

Here we go pic.twitter.com/4kzBOQWdP8

— Ian Livingston (@islivingston) February 13, 2014

The latest discussion from the National Weather Service’s Storm Prediction Center warns that heavy snow will overspread the I-95 Corridor from D.C. to New York City now through around 7 a.m., with snowfall rates of 1-2″ per hour likely:

THE MOST PERSISTENT BAND OF HEAVY SNOW WILL LARGELY OVERSPREAD THE MEGALOPOLIS THROUGH DAYBREAK. THIS SHOULD GENERALLY LIE JUST NW OF THE TRANSITIONAL CORRIDOR TO RAIN ALONG THE MID-ATLANTIC COASTAL PLAIN. MODERATE TO HEAVY SNOW WILL FIRST INCLUDE THE WASHINGTON/BALTIMORE METRO AREAS SHORTLY AFTER 06Z.

Translation: heavy snow is expected to arrive in the D.C. area in the next couple hours. And in fact, you can see it coming in the radar image below from 12:33 a.m., which shows a heavy band of snow around and east of Fredericksburg, Va., heading north toward Washington.

Radar from 12:33 a.m. (Weather Underground)

This CWG meteorologist is not enjoying the snow in D.C. tonight. It’s not that I don’t like snow. It’s that I’m physically *not* in the D.C. area. Instead, I blog to you live from from a hotel in mild and muggy Orlando. That is where I am now stranded for at least a day or two.

You may ask, how does a meteorologist get stranded by the weather? Well, I sure did try to avoid it. On Monday, knowing my Wednesday afternoon flight back home from Key West with a stop-over in Atlanta would almost certainly be cancelled, I booked a connection through Orlando instead. All was on track this morning, until my flight from Key West to Orlando was delayed *three* hours *not* due to weather whatsoever, but to a maintenance issue. That was long enough to miss my connection and what turned out to be the last flight out to BWI.

I will allow the culprit airline to remain nameless, but needless to say I’m none too pleased.

That said, I am thankful to have a hotel room and not be sleeping at the airport, as I imagine some are doing tonight in more than a few cities directly and indirectly impacted by this massive storm.

Water vapor image from 12:10 a.m. (NOAA)

PS: Hey D.C. snowlovers, I am living vicariously through you as you soak up the joy of the white stuff.

Gotta give credit where credit is due, and it goes to the European model once again. As late as Sunday afternoon the American Global Forecast System (GFS) model was showing this storm barely clipping the D.C. area before heading out to sea. This, at the same time the often ballyhooed European model had already been advertising a more significant storm that would ride up the coast and have a significant impact across the mid-Atlantic and into the Northeast.

European model from 7 p.m. Saturday night (forecast for 7 a.m. Thursday morning) was already indicating a significant winter storm for the mid-Atlantic and Northeast

This isn’t the first time the GFS has erroneously shown a storm heading out to sea. You may remember that a few days before Superstorm Sandy struck the Northeast, the GFS suggested it would stay offshore while the Euro correctly showed it hooking left toward the coast.

So is the GFS useless? Absolutely not. In fact, it performs quite well much of the time, and in some situations it can outperform the Euro. In addition, new funding to the National Oceanic and Atmospheric Administration will allow for increased computing capacity and therefore an enhanced GFS model that is run at a higher resolution.

But in the meantime, it’s clear that at least with some storms, the GFS has a tendency to incorrectly push storms out to sea.

When it comes to snowstorms, we all want as accurate a forecast as possible. And of course us meteorologists want to *make* as accurate a forecast as possible. But the reality is that with some storms, we have trouble confidently predicting whether we will get significant snow versus little-to-no snow, let alone exact totals.

While the utlimate totals from this storm are still in question, it is quite clear that it is not a “bust” like last year’s “Snowquester” storm. Further, you may have noticed that our forecasts during the 36 hours or so leading up to the storm were fairly confident in at least several inches of snow. How come? The three main reasons…

Cold air and cold ground to start: This one is often missing for D.C. area winter storms, but not this time.

Lengthy period of solid snow: It was fairly clear we’d see at least a several hour period of steady snow before any chance of warmer air working in and changing some areas to mixed precipitation.

Model consensus: By late Monday and early Tuesday, models mostly agreed on the timing and general track of the storm up the coast, even while differing as to when and how much sleet/rain might mix in.

The result is a quickly developing winter wonderland…

A little snow at the Capitol tonight. #dcwx #PAX cc: @uscapitol @capitalweather pic.twitter.com/Uz2eZfEC6x

— Judd Deere (@JuddPDeere) February 13, 2014

As the snow falls at a light to moderate clip, all signs are that the intensity should really pick up after around 1 a.m.

Here are some useful snippets from the latest discussion from the National Weather Service for our region:

Regarding overnight snowfall

AFTER [1 AM]…WILL START TO SEE STRONGER FORCING AND BANDING POTENTIAL ALONG WITH HEAVY SNOWFALL AT TIMES WHERE SNOWFALL RATES OF 1 TO 2 INCHES PER HOUR MAY OCCUR. SNOW WILL ALSO START TO MIX WITH OR CHANGE OVER TO SLEET/RAIN ACROSS ST MARYS/CALVERT COUNTIES WHICH WILL CUT DOWN ON SNOWFALL ACCUMULATIONS BUT COULD ALSO LEAD TO A BRIEF PERIOD OF ICING BEFORE SURFACE TEMPERATURES RISE ABOVE FREEZING.

Regarding conditions in the morning

SNOW CONTINUES HEAVY AT TIMES THURSDAY MORNING /FOR SIGNIFICANT IMPACT DURING THE MORNING RUSH/…BUT THE RAIN/SNOW LINE IS EXPECTED TO TILT FURTHER NORTHWESTWARD DURING THE DAYTIME AT LEAST TO THE INTERSTATE 95 CORRIDOR PERHAPS EVEN FURTHER WEST. THOSE AREAS THAT RECEIVE ALL SNOW WILL SEE THE HIGHEST ACCUMULATIONS…

Regarding the late afternoon and evening

THE LOW IS EXPECTED TO SLOW DOWN AS IT RAPIDLY DEEPENS ON THU AFTN. THE 12Z ECMWF/NAM SHOWS A WELL-DEFINED TROWAL DEVELOPING…RESULTING IN A MODERATE TO POTENTIALLY HEAVY SNOW BAND AROUND THE BACKSIDE OF THE LOW. ACCUMULATING SNOW COULD LINGER INTO THU EVE ACROSS THE SWRN HALF OF THE CWA AND LATE THU NGT ACROSS THE NERN HALF.

Some more pics:

@capitalweather there’s about an inch on the ground in Woodley Park, but the lion doesn’t seem to mind. pic.twitter.com/jwq0FruZ4z

— Rence (@RenceD) February 13, 2014

Courthouse 10:55pm. Wilson and Clarendon Blvds mostly covered. Cross streets completely covered. @capitalweather pic.twitter.com/TGJirTkD5v

— Michael Raumer (@mindpivot) February 13, 2014

@Efeste Here's some real-time reporting from Iwo Jima for you and @capitalweather on the snow. pic.twitter.com/gBeb0IaRox

— Aaron Menenberg (@AaronMenenberg) February 13, 2014

From SW DC:

All of the models have simulated heavy snow overnight, but the one hold-out has been the GFS which forecast more moderate amounts. While its latest run isn’t as snowy as the NAM and some of the other models, it is certainly snowier than its own earlier predictions.

GFS model simulates over 0.5″ of liquid equivalent precipitation between 1 a.m. and 7 a.m. alone. The solid blue line is an approximation of the snow/sleet line at 7 a.m. (StormVistaWxModels.com)

It now forecasts 0.81″ of liquid equivalent precipitation at Reagan National Airport through 7 a.m. which would be roughly 8 inches of snow (compared to around 5″ in its simulation for the same time period 6 hours ago). The model does suggest the snow will mix with and changeover to sleet along the I-95 corridor, but not until between 7 and 10 a.m.

Up until now, the intensity of snow has generally been light in the D.C. area, but radar shows a band of moderate snow working into the region.

Radar view as of 10:25 p.m.

Ground reports confirm that the snow is picking up in central and northern Virginia:

@capitalweather blowing here at Potomac TRACON / FAA Command Center. 20187 near Warrenton. pic.twitter.com/VNCrQK7XOf

— John Kosak (@Defender13) February 13, 2014

@capitalweather columbia heights @10:30pm pic.twitter.com/BafqWBcseA

— CaliGRLnDC ♓ (@nte77) February 13, 2014

@capitalweather Deicing at DCA. pic.twitter.com/5EYAqGsGH0

— Graham Campbell (@GrahamCC) February 13, 2014

@capitalweather the snow is crashing down here in Cville at #UVA #noclasses #manyinchespredicted pic.twitter.com/qv3McloYdd

— Brooke Hering (@Pikasurf2013) February 13, 2014

The NAM and short-range models are going bonkers with their snowfall simulations overnight, and it’s snowing to beat the band in areas to our south. Something tells me some locations, especially west of the District, are going to exceed our most likely snowfall range, and enter BOOM territory.

Mike LaPrade, a reader from Charlottesville, says: Been snowing … since 5 p.m. Approx 4 inches so far and snowing hard. Big surprise: light fluffy snow when heavy wet snow was predicted.

Totals around Richmond are also near 4 inches, so far.

Farther south, into southern Virginia, around 5 inches have fallen in Lynchburg.

Just measured 4.8" here in Midtown Lynchburg.

— Sean Sublette (@SeanSublette13) February 13, 2014

Even more has fallen near Roanoke:

I have 7.1" of snow on my snow board in SW Roanoke county as of 9:55PM and still snowing hard….a… http://t.co/W8GeuJ8e4x

— LeoHirsbrunner (@LeoHirsbrunner) February 13, 2014

Snow totals through 10pm from NWS and viewer reports. Are yours close to these? pic.twitter.com/w1HERMOmVo

— Brent Watts (@wattsupbrent) February 13, 2014

The National Weather Service reports 8 inches in Danville. Good resource: List of snow totals by state.

Around Richmond, thundersnow has been reported this evening and there were reports in North Carolina earlier today.

“I think that’s a real thing that can happen tonight in our area,” says Wes Junker, Capital Weather Gang’s winter weather expert. “As moist as it is and with the vertical motions we’re getting, it’s a legitimate possibility.”

Reports of thundersnow western Chesterfield. Storm tops shows elevated possible convection heading NE. pic.twitter.com/5XQLUmpsxj

— Jim Duncan (@JimDuncanNBC12) February 13, 2014

@capitalweather it's extremely heavy in Midlothian VA. About 4 inches so far. Crazy white out.

— Mrs. Jenn S. (@VTDiva01) February 13, 2014

Thundersnow is simply a thunderstorm with snow falling to the ground instead of rain. Thundersnow is often extremely intense, with snowfall rates of 1 to 3 inches per hour. For a more technical overview of the phenomenon, follow this link: What causes thundersnow?

The NAM model has insisted the region is going to get a ton of snow and sleet tonight into tomorrow morning. Its latest run – hot off the presses – is pretty remarkable.

Between 1 a.m. and 7 a.m., it simulates 0.98″ of liquid equivalent precipitation at Reagan National Airport and even into Leesburg, Va., which would be about 10 inches of snow in 6 hours if correct. The wrinkle is that close to I-95, it introduces the possibility the snow *may* mix with or change to sleet as early as 5 a.m. which would cut down those totals. But – especially in our western areas – a period of heavy, potentially crippling snow is quite possible late tonight through the early morning hours.

Simulated liquid equivalent precipitation by the NAM model between 7 a.m. and 1 p.m. Thursday. The solid blue line cutting through D.C. is a rough approximation of the snow-sleet line. (StormVistaWxModels.com)

The model suggests precipitation will decrease a little in intensity late morning through early afternoon and will probably be mixed (sleet and freezing drizzle) even into western Fairfax and Montgomery county.

Simulated liquid equivalent precipitation by the NAM model between 7 a.m. and 1 p.m. Thursday.  The solid blue line cutting through western Fairfax and Montgomery counties is the snow-sleet line. (StormVistaWxModels.com)

But it then forecasts colder air to wrap into the area with the mix changing back to snow from west to east from mid-afternoon into the evening, with additional snow accumulation.

Simulated liquid equivalent precipitation by the NAM model between 7 p.m. Thursday and 1 a.m. Friday. Precipitation is all snow at this time in this model (StormVistaWxModels.com)

The model suggests it may still be snowing as late as 10 p.m. or so in the metro region.

Even after we get through tonight’s potential snow blitz, tomorrow promises to be a changeable, interesting day.

In some of our big winter storms (e.g. the blizzard of 1993) coming out of the Gulf of Mexico, severe thunderstorms form on their southern flanks and tear across the Florida as tropical air and arctic air collide. This is happening tonight, with a nasty squall line ripping across the Peninsula.

Radar view of Florida Peninsula at 8:45 p.m.

A severe thunderstorm watch is currently in effect for South Florida through 11 p.m.

There have been several reports of damaging winds, and at least one tornado touched down near Ft. Meade, Florida at 6 p.m.

Just in: #tornado was reported at 6pm near Ft Meade, FL; "roof porch blown away".

— TWC Breaking (@TWCBreaking) February 12, 2014

It’s hardly been snowing more than hour in many places, yet due to the cold temperatures and frozen ground, the snow is accumulating everywhere.  Here’s an assortment of reports:

@capitalweather 14th st nw in Petworth, 1/4 or more, roads salted/sanded but still covered pic.twitter.com/TZTFWAfDUZ

— Jess Pic (@Jesswithacamera) February 13, 2014

Getting bad already in Crystal City/DCA @capitalweather @dougkammerer pic.twitter.com/or5XnOr9bo

— David Seay (@DaveJSeay) February 13, 2014

Piling up in Clarendon @capitalweather pic.twitter.com/Vu8sAxR4sE

— Manena Bernasconi (@manesconi) February 13, 2014

We can get a sense of what’s coming at us by examining conditions to the south. First it was snow in central North Carolina, now it’s a wintry mix:

@JimCantore 8″ snow front porch Pinehurst NC. Now freezing rain. #weatherchannel #weather pic.twitter.com/S1FE0DkDBj

— Barto (@Bartoshred) February 13, 2014

While snow remains mostly light to occasionally moderate — and very fluffy — radar and short range models indicate we’re on track for the overnight “thump” of snow which we expect to drop at least 4-8 inches if not more.

Here’s a recent run of the HRRR at midnight tonight. It shows moderate to heavy snow over the area:

(Weatherbell.com)

Once the heavier bands move in, they should continue in most of the region for at least several hours, and maybe into the dawn period.

When it comes to the transition to mixed precipitation there is still some disagreement. Another short range model, known as the RAP, warms things considerably as we head into sunrise, mixing spots near I-95 and flipping to rain south and east.

(Weatherbell.com)

However, the HRRR is is considerably slower with the advance of warm air, and it keeps the I-95 corridor in the snow at least through the sunrise period, all while dumping lots of the white stuff.

(Weatherbell.com)

It’s going to take some time to figure out which is right as small changes can have big impacts. We’ll be watching as the low begins to climb the coast.

Radar capture as of 7:30 p.m. (NOAA)

We’ve received reports of flurries to light snow throughout most of the area at this point. It’s perhaps covered the entire region on the early side of expected, but within the general window.

While much of the snow is light around here so far, small bands of moderate activity are developing within the snow shield. The intensity will also continue to increase in the next few hours from south to north.

Some early imagery of the snow sticking across the area:

@capitalweather Driveway and sidewalks white in Vint Hill already. pic.twitter.com/84JGfXjfps

— Joel Housman (@joelhousman) February 13, 2014

@capitalweather One eighth inch down, 159 to go in NE Fauquier: pic.twitter.com/N6jfNF6TC5

— Kevin (@thefolkist) February 13, 2014

@capitalweather got some light coatings in #SilverSpring pic.twitter.com/bHrMVPYlNC

— nina lior (@ninalior) February 13, 2014

mPING display as of 6:15 p.m.

If you’ve never participated in mPING, you really should. Apps are available for Apple and Android devices — check ‘em out!

What is mPING? Let’s start with what it stands for: Meteorological Phenomena Identification Near the Ground. Basically, a quick few seconds of your time can help advance radar technologies and techniques.

While it’s useful to report all the time when there is precipitation, it’s particularly helpful to those analyzing the data if you report if and when snow mixes or changes over.

You can also watch the reports as they come in on their website.

While this storm might be starting on the kind side, it’s going to turn mean (or awesome if you’re a snow lover) as we get into the night. The Storm Prediction Center is now monitoring the area for heavy snow rates of 1-2 inches per hour as we get into the overnight.

SPC expects the heaviest to move toward us, perhaps focusing on the immediate area, in the hours around midnight.

Here’s a snippet, and check out the whole thing (note: technical, and times are in UTC)

SUMMARY…A LARGE SWATH OF MODERATE TO HEAVY SNOW WILL DEVELOP NEWD THIS EVENING WITH RATES OF 1-2 IN/HR. THE MOST PERSISTENT BAND SHOULD EXIST ALONG THE BLUE RIDGE MOUNTAINS AND ADJACENT PIEDMONT FROM NWRN NC TO CNTRL VA THROUGH ABOUT 03Z [10 p.m.] AND INTO THE WASHINGTON DC METRO AREA BY 06Z. [1 a.m.]

Radar is great, but ground reports are even better as a storm is getting underway. Folks on the blog, Facebook, and Twitter are indicating that flurries have indeed overspread a good chunk of the region, at least in spotty fashion.

Down towards Charlottesville, a report of 1/2 inch has come in. Snow started there a bit more than an hour ago.

It’s only just begun. Here’s a sample from Twitter:

@capitalweather Snowing in Stafford!!

— Artise (@tise66) February 12, 2014

Snow flakes just started in Fairfax City. Very light. CC @capitalweather

— Keith Robertory (@krobertory) February 12, 2014

@capitalweather light flurries north of Dulles – it has begun!

— Shawn Benham (@terp1018) February 12, 2014

Where’s the snow? It’s coming in from the south and southwest. Reports indicate light snow is now falling in places like Warrenton and around Fredericksburg, Va. It matches pretty well with the leading edge on NWS Baltimore/Washington’s radar.  Additional snow is also being reported north of that zone, mostly very light and still being missed by radar.

6:18 p.m . local radar (Weather Underground)

Short term models, like the most recent run of the RAP seen below, continue to indicate that snow should overspread most of the area in the next few hours. It will stick immediately, but probably mostly remain light for a while.

RAP model simulated radar for 9 p.m. tonight. Note: since this is a composite radar, the lighter colors of green are likely virga/not reaching the ground. Darker green covers most of the D.C. region at this point. (Twisterdata.com)

Your reports help us keep up with what’s going on. Let us know what you see!

Although the main focus as the storm gets underway will be snow, turning heavy overnight. We’re also looking at increasing winds, particularly as the low pressure nears the area late tonight and into tomorrow. We briefly detailed that in our PM Update.

You’ll really notice winds kicking up from the north as we get past midnight, and in the hours around sunrise it could be sustained as high as 20 mph or higher, with some gusts to 35 mph. While this isn’t a classic setup for a big wind maker, and true blizzard conditions are not terribly likely, periods of near whiteout visibility are possible at times.

Here’s a snapshot for the area at 6 a.m. (winds shown in knots):

High resolution NAM forecast for 6 a.m., winds in knots. (Weatherbell.com)

Winds may diminish a bit during the day, but stay gusty. As we get into evening (7 p.m. forecast shown below) they might pick up again, this time from the northwest:

High resolution NAM forecast for 7 p.m., winds in knots. (Weatherbell.com)

In all cases, the strongest winds are likely to be right near the water, and over the higher elevations, but pretty much everyone could see big gusts here and there.