3:00 PM Active pattern continues into mid-week; some interesting winter weather notes

Discussion

Active pattern continues There are multiple disturbances headed our way in the Saturday-to-Monday time frame and each one could bring some snow to the Mid-Atlantic region and it is a good bet that we'll have some fresh snow cover by later Monday. The first system rides along the southern branch of the jet stream on Saturday and could produce a light snowfall in the area. The next couple of systems ride in from the west on the northern branch of the jet stream. The first northern system could produce a light snow event around here on Sunday and then the second northern system might have a little more punch to it and it could end up being more than just a “light” event late Sunday night/early Monday; especially, south of the PA/MD border [Canadian model forecast for early Monday]. Finally, the potential exists for a strong system to pull out of the Deep South around mid-week (Wednesday night/Thursday) and head towards the east coast with lots of available moisture.

General notes on the winter weather - Still a lot of cold air around the northern hemisphere… Great Falls, Montana dropped to 34 degrees below zero this morning for their coldest temperature in 18 years and Suhana, Russia bottomed out at 73 degrees below zero - The Great Lakes ice cover extent has now reached ~80% which is at a record high for the date and well above normal - The current US snow cover extent is around 68% - Tokyo, Japan could receive 6-12 inches of snow by tomorrow in the Japanese version of a nor'easter and this would be more than their yearly average. The upper-level trough associated with that storm in the Far East could actually play a role in the development of an eastern US trough around the middle of next week.

7:00 AM |*Multiple chances for snow into Monday and then again by the middle of next week*

6-Day Forecast

Today

Partly sunny, cold, highs in the upper 30’s

Tonight

Partly cloudy, quite cold, lows in the low-to-mid 20’s

Saturday

Mostly cloudy, cold, chance for some snow, low 30’s

Saturday Night

Mostly cloudy, cold, chance for some snow, mid-to-upper 20’s

Sunday

Mostly cloudy, cold, chance for some more snow, mid-to-upper 30’s

Monday

Chance for snow early; otherwise, partly sunny, cold, low 30's

Tuesday

Mostly sunny, very cold, near 30

Wednesday

Mostly cloudy, cold, snow possible late, low-to-mid 30’s

Discussion

A complicated forecast for the Mid-Atlantic as multiple upper-level disturbances could affect the region into early next week and each one of them can bring some snow to the area with light-to-moderate accumulations. The first system will come out of the south on Saturday and help to spawn surface low pressure just off the Mid-Atlantic coastline. Currently, it appears that the heaviest precipitation from this low pressure system will stay to our southeast, but some snow is likely to reach this far north. Another couple of upper-level systems will ride along the northern branch of the jet stream from Sunday into Monday and each could generate some snow around here. Cold air will follow for later Monday and Tuesday and then attention will turn to the Deep South as a storm could pull out of that region by mid-week with lots of moisture and head towards the east coast.

Video

httpv://youtu.be/_jo_zY2rSDQ

1:45 PM | Breakdown of the weekend possibilities

Discussion

Weekend scenario(s) One way to get a significant snowstorm in the Mid-Atlantic region is to have a wave of upper-atmosphere energy in the northern branch of the jet stream “phase” together at just the right time with a wave of energy in the southern branch of the jet stream to generate a strong storm along the Mid-Atlantic coastline (of course, cold air is needed as well). Even though there will be two systems to deal with this weekend – one riding along the southern branch of the jet stream and the other in the northern branch – they appear to be separated by about 24-hours or so. The southern system will arrive on the scene in the Mid-Atlantic region on Saturday while the northern system will move in on Sunday.

In this particular weekend setup, there are still two other ways to get significant snowfall around here – neither of which seems likely at the moment - but still cannot be ruled out completely. The first way would be if the southern system generates on its own a strong storm along the coast. Indeed, it does like a strong low pressure system will form along the Mid-Atlantic coastline by Saturday, but – at least for the moment – its heaviest precipitation shield is just a bit too far to the southeast of the I-95 corridor to create any substantial snowfall around here. The second possibility would be if the northern system on Sunday intensifies rapidly on its own as it reaches the relatively warm waters of the western Atlantic Ocean. While this scenario does not currently seem likely, the upper-level trough associated with the northern system does become “negatively-tilted” as it approaches the east coast and this sometimes signals rapid intensification is about to occur along the Northeast US coastline.

The bottom line: both systems still bear watching. The first system (southern) on Saturday has to be monitored to see if its heaviest precipitation area shifts to the northwest and into the I-95 corridor. The second (northern) system has to be monitored to see if it could experience quick intensification along the Mid-Atlantic coastline on Sunday. If neither happens, then the most likely result would be nothing more than a "light-to-moderate" snowfall with either system. Stay tuned.

12Z NAM The latest 12Z NAM computer forecast model run shows (above) the southern wave of energy in the upper atmosphere (500 mb) on Saturday morning well ahead of the northern wave. This southern wave does not phase together with the northern wave, but it does generate quite a strong storm off the Mid-Atlantic coastline that needs to be monitored. The northern wave of energy takes on a “negative-tilt” by Sunday and it could intensify quickly upon reaching the coastal waters. More details available on the 12Z NAM model run in the video discussion (below).

Looking ahead The overall cold weather pattern looks like it will continue in the Mid-Atlantic region for the foreseeable future through much of February. The active nature to the weather pattern also looks like it will continue with another storm threat coming around the middle of next week.

Video

httpv://youtu.be/KV8Fz_NYhUI

7:00 AM | Dry, cold weather in the aftermath of yesterday's storm; weekend update

6-Day Forecast

Today

Mostly cloudy, cold, highs in the mid 30’s

Tonight

Mostly cloudy, very cold, lows not far from 20 degrees

Friday

Partly sunny, cold, near 40

Friday Night

Partly cloudy, cold, middle 20’s

Saturday

Mostly cloudy, cold, chance for a little snow or rain, mid 30’s

Sunday

Mostly cloudy, cold, a period of snow with light-to-moderate accumulations possible, mid 30’s

Monday

Mostly sunny, cold, low 30’s

Tuesday

Partly sunny, very cold, near 30

Discussion

Dry and cold weather will dominate the scene through tomorrow in the aftermath of yesterday’s storm. The weekend situation features a northern wave of low pressure and a southern wave of low pressure and if these two were to phase together at the right time then a strong coastal storm could be the result. However, it currently appears that they will not phase together and, instead of one big storm, there will be two separate and weaker systems. The southern energy could produce a little snow and/or rain around here later Saturday and then the stronger, northern piece of energy is likely to cause a period of snow on Sunday with light-to-moderate accumulations possible.

Video

httpv://youtu.be/KV8Fz_NYhUI

7:00 AM | **Freezing on some surfaces this morning in the northern and western suburbs**

6-Day Forecast

Today

Rain this morning that will continue to freeze on some surfaces north and west of the District, becoming milder this afternoon, highs in the low 40’s

Tonight

Mostly cloudy, cold, lows in the low-to-mid 20’s

Thursday

Mostly sunny, cold, low-to-mid 30’s

Thursday Night

Mostly clear, very cold, low 20’s

Friday

Partly sunny, cold, mid 30’s

Saturday

Mostly cloudy, cold, chance for some snow or rain, mid-to-upper 30’s

Sunday

Cloudy, cold, chance for some snow or rain, mid 30’s

Monday

Partly sunny, cold, low 30’s

Discussion

Rain this morning across the District, but it can still freeze on some surfaces for awhile in the northern and western suburbs. Clearing skies tonight will set us up for a couple of dry and cold days. Great potential exists for a storm this weekend, but the details still need to be ironed out. A storm is likely to develop rapidly by later this weekend along the Mid-Atlantic coastline, but exactly where that forms is still to be determined - and important to any prospective snow accumulation forecast.

2:45 PM | **Most serious threat tonight/early Wednesday is a significant buildup of ice**

Discussion

Ice storm tonight/early Wednesday Yet another storm will impact the Mid-Atlantic region from later this evening through Wednesday morning and the most serious threat from this system is a significant buildup of ice - not accumulating snow. Precipitation should begin as snow in the Philly metro region before midnight and it could accumulate 1-3 inches before changing to sleet and freezing rain after just a couple of hours. Freezing rain is then likely for the remainder of the night generating an icy buildup and slick driving conditions on untreated surfaces. The icy buildup (one-tenth to one-quarter of an inch) will also become a threat to tree limbs and power lines given its weight on top of any residual heavy, wet snow. By early morning, “plain” rain is likely in the city of Philadelphia, but freezing on some surfaces will continue for awhile in the northern and western suburbs. “Plain” rain is likely in the suburbs by mid-morning as temperatures finally creep above freezing in those locations. All areas will see an end to the precipitation during the mid-day hours.

NYC and DC Elsewhere, the NYC region will see a gradual transition from snow-to-ice after midnight with 3-6 inches of snow possible (higher amounts in that range to the north) before any changeover to sleet and freezing rain. A wintry mix is likely to continue through much of the day on Wednesday; especially, in the northern and western suburbs, producing an icy buildup on top of the fresh snowpack.

In the DC metro region, sleet and freezing rain will move in before midnight and generate an icy buildup in the northern and western suburbs in the overnight hours. “Plain” rain is likely in the District by the early morning hours and in the suburbs by mid-morning. All areas will see an end to the precipitation during the mid-day hours.

7:00 AM | **Stormy week continues with freezing rain tonight that can cause a significant ice buildup; especially, in suburban locations; weekend storm threat continues**

6-Day Forecast

Today

Mainly cloudy, cold, highs in the mid 30’s

Tonight

Freezing rain developing this evening that will buildup on some surfaces; especially, north and west of the District, lows near 30 degrees

Wednesday

Primarily plain rain in the District, but freezing can continue on some surfaces for awhile in the N and W suburbs with additional ice buildup possible, low-to-mid 40's for highs in the District, upper 30's in the N and W suburbs

Wednesday Night

Mostly cloudy, cold, low teens

Thursday

Mostly sunny, cold, low 30’s

Friday

Mostly cloudy, cold, mid 30’s

Saturday

Becoming cloudy, cold, chance for snow or rain late in the day or at night, mid 30’s

Sunday

Mostly cloudy, cold, chance for snow or rain, mid 30’s

Discussion

If I could give some advice to the National Weather Service, it would be to just put a “winter storm watch” out for much of the Mid-Atlantic region until mid-February. One storm began the work week and we are not even close to being done with the stormy pattern that will last right into mid-month. A second and complex storm will spread frozen precipitation our way tonight and there will be an accumulation of ice by morning and freezing rain could continue for awhile on Wednesday in the N and W suburbs, expect a changeover to plain rain in the District on Wednesday. Slick road conditions are possible later tonight and early tomorrow with this latest batch of snow and ice; especially, in the N and W suburbs. Dry and cold air follows for Thursday and Friday and then attention will turn to the Deep South. A storm looks like it will pull out of the southern states later this weekend and head towards the east coast with lots of moisture, but there are still lots of details left to be ironed out for this system.

Video

httpv://youtu.be/ugKo36O1mHo

6:00 AM | **The farther north and west one goes - the more the signficant snow; rain in the District**

6-Day Forecast

Today

In the District: rain, heavy at times, possible changing to sleet and snow for a brief time later this afternoon, little or no accumulations; In the nearby northern and western suburbs (e.g., Rockville, MD, Leesburg, VA): rain changes to sleet and then snow later this morning with snow continuing into the early afternoon, 2-4 inches of snow accumulations; In the far northern and western suburbs (e.g., Frederick, MD, Winchester, VA): snow, heavy at times, into the early afternoon hours with 4-8 inches of accumulation, temperatures holding in the low-to-mid 30’s for much of the day in the suburbs and mid-to-upper 30's in the District

Tonight

Gradual clearing and quite cold, lows near 25 degrees

Tuesday

Some sun then increasing clouds, cold, upper 30’s

Tuesday Night

Cloudy, freezing rain and/or sleet developing and there can even be some buildup of ice in the northern and western suburbs, cold, lows near freezing

Wednesday

Mostly cloudy, becoming a bit milder, precipitation changes to plain rain, low 40’s

Thursday

Mostly sunny, colder, low 30’s

Friday

Partly sunny, cold, mid 30’s

Saturday

Mostly cloudy, cold, chance for rain or snow, upper 30’s

Discussion

A gradual changeover from rain-to-snow is occurring from north-to-south and the result will be big differences in snow accumulation amounts depending on specific location. In the District, much of the storm will feature rain, heavy at times, but it is possible that the rain changes briefly to sleet and snow this afternoon - little or no accumulations. In the nearby northern and western suburbs (e.g., Leesburg, VA, Rockville, MD), the transition to snow will occur late this morning and snow accumulations should end up in the 2-4 inch range. In the far northern and western suburbs (e.g., Frederick, MD, Winchester, VA), snow will fall into the early afternoon and 4-8 inches of snow can accumulate the end of the storm. There will be no snow at all just south of the District (e.g., southern Maryland). Another storm will bring a period of ice (freezing rain and/or sleet) to the region on Tuesday night before a changeover to plain rain on Wednesday and there can be some accumulation of ice before the changeover in the northern and western suburbs. A third storm threatens for the weekend and it is too early to give details on precipitation type, but it promises to be a powerful storm loaded with moisture and it could turn out to be an all-out blizzard for parts of the Mid-Atlantic.

12:10 PM | **Several inches of snow on Monday from the DC metro region-to-Philly-to-NYC**

Discussion

Overview A snowstorm is in store for the Mid-Atlantic I-95 corridor region on Monday from the DC metro region-to-Philadelphia-to-New York City. Fresh, moderately cold air will slowly filter into the region late tonight and early tomorrow following the passage of a cold frontal system. Precipitation will begin in most areas well after midnight in the form of rain and then transition briefly to sleet and then ultimately to all snow on Monday with several inches of snow accumulation expected from the northern and western suburbs of DC to New York City. The NAM computer forecast model from NOAA has indeed shifted northward with its precipitation shield for tomorrow’s storm [precipitation totals shown below for the 24-hour period between tomorrow morning and Tuesday morning from last night’s model run versus this morning’s model run].

Specific forecast details by region follow: DC: 1-3 inches in the District; 3-6 inches in the northern and western suburbs; a sharp cutoff to the snow accumulation just south of the District (e.g. southern Maryland gets little if any). Rain begins after midnight and transitions to a brief period of sleet before changing to all snow in the northern and western suburbs during the early-to-mid morning hours. Snow will fall heavily at times in the northern and western suburbs during the latter stages of the morning and into the early afternoon, and for a brief period of time in the District. Snow winds down in all areas by late afternoon.

Philly: 4-8 inches of snow accumulation with the lesser amounts in that range in the city of Philadelphia and the higher amounts in the northern and western suburbs; less overall at the shore in southern New Jersey (1-3 inches). Rain begins well after midnight and transitions briefly to sleet before ultimately changing to all snow during the early-to-mid morning hours. Snow falls heavily at times from mid-morning through the early afternoon hours before winding down by late afternoon.

NYC: An average snow accumulation of 3-6 inches in and around the NYC metro region. There will be a brief period of rain and/or sleet towards morning before a changeover to all snow during the early-to-mid morning hours. Snow falls heavily at times from late morning to mid-afternoon before winding down late in the day.

Other info One difference between this storm and recent snow events is that temperatures will just be marginally cold enough for snow on Monday (ie low-to-mid 30’s). As a result, the snow will be of the “wet” variety and will have some trouble sticking on treated roadways in the initial hours of the storm, but that will likely change rather quickly as soon as the snow begins to fall heavily.

Looking ahead Monday’s snowstorm is just the first storm of what will likely be a very active 10 days or so. Another storm will move into the Mid-Atlantic region on Tuesday night and will continue through Wednesday morning. It appears that storm will bring a period of frozen precipitation to the I-95 corridor before a changeover to plain rain. Most likely scenario in the DC metro region is for ice (ie freezing and/or sleet) on Tuesday night, at least in the northern and western suburbs, before a changeover to plain rain by Wednesday. There can be some ice buildup in the northern and western suburbs of DC before the changeover to rain. In Philly and NYC, there can be ice and/or snow on Tuesday night before a changeover to plain rain on Wednesday. The ice and/or snow can accumulate some in those metro regions on Tuesday night before the changeover to rain. Finally, another storm threatens the entire region next weekend and, while it is too early to say exactly what the precipitation-type will be, it does look like it will be a powerful system loaded with moisture and it could turn out to be an all-out blizzard for parts of the Mid-Atlantic.

Update on the sun On a completely different note, the sun currently has an active and large sunspot region that is directly facing the Earth. For more details on today’s arrival of a coronal mass ejection from a recent solar flare, check the “Climate Info” section of the weather web site.

2:00 PM | **Still the threat for several inches of snow on Monday in the I-95 corridor from DC-to-Philly-to-NYC**

Discussion

Despite the thaw this weekend, there is still the good possibility of a snowstorm on Monday with several inches of snow in much of the I-95 corridor from DC-to-Philly-to-New York City. A cold frontal passage on Sunday will end our brief spell of mild weather and then moisture will ride along the frontal boundary zone into the Mid-Atlantic region on Monday. The US computer forecast models (NAM, GFS) have indeed started moving northward with their precipitation field from their earlier forecasts with little in the way of significant precipitation north of the PA/MD border. The European and Canadian forecast models have had pretty significant precipitation amounts all along and as far north as the NYC metro region.

Still a couple days to go to this event, but here are some of the possibilities (still subject to some revisions). First, the likeliest "bullseye" region for the heaviest snowfall is across northern Maryland, northern Delaware, Philly and all of SE PA, and interior sections of central New Jersey (somewhat similar to the December storm with the “Eagles snow” game). [The District of Columbia may be limited some by mixing issues and the NYC metro region may be limited a tad by being on the northern fringes of the heaviest precipitation amounts]. In the Philly area, the precipitation could begin briefly as rain and/or sleet early Monday, but will then change to snow and be primarily a snow event with several inches likely. In DC, the precipitation will begin as rain and/or sleet early Monday and it could take a while to changeover to snow in the District, but comparatively less time across its northern and western suburbs (e.g. northern Maryland). As a result, the District may end up with “moderate” snow accumulation amounts while its northern and western suburbs get hit quite hard. NYC may have a brief period of rain and/or sleet, but then it should be primarily a snow event up there with several inches possible.

Next week will bring us two additional storms after the Monday event. The second storm looks like it will feature a period of frozen precipitation (ice and/or snow) on Tuesday night then there will be a changeover to plain rain on Wednesday and some of the rain will be heavy. A third storm threatens the Mid-Atlantic region next weekend and it could be quite strong – too early to say with respect to precipitation-type. Both of these storms will have copious amounts of moisture to work with.

All in all, not the best news for all of those freshly-washed cars out there.