1:45 PM | Now on to the next storm...weekend coastal threat; an update on the impressive and widespread nationwide cold

Discussion

Snow is winding down across the I-95 corridor from DC-to-NYC and road conditions should improve quite a bit in time for the late afternoon rush hour. Very cold and dry conditions will prevail from tonight through Friday with low temperatures in the teens in many of the northern and western suburbs of the big cities, and single digits cannot be ruled out for lows later this week in some of these locations. By the weekend, our attention will turn to the next storm and this could be a significant storm with copious amounts of moisture. Low pressure will pull out of the south-central part of the country at the end of the week and will likely consolidate into a strong storm along the Northeast US coast. While very cold weather prevails through Friday, a wintry mix along the I-95 corridor is a possibility. Stay tuned on this as there are still several days to go before the event (Saturday-into-Sunday time frame) and I believe that the forecast models will likely trend colder as the event time nears which would lead to a greater chance for snow.

In terms of how cold and snowy we have been across the nation over the past week or so, here are some interesting stats from many different locations with a focus on the western US:

• Nationwide: The nationwide average temperature of 14.8°F early Saturday morning was the 5th coldest reading since 2000. Preliminary readings suggest that the CONUS average temperature for the last 6 days was 20.8°F which is about 14 degrees below normal and the coldest since 1979 (source Ryan Maue at weatherbell.com)

• Chicago, IL: This morning featured the earliest sub-zero temperature (-6 degrees at O'Hare) in 18 years

• Philly Airport: has now received about as much snow in the past three days as in the last two winters combined

• Great Falls, MT: low temperature of -33°F this weekend was their coldest ever recorded so early in the season

• Medford, OR: record low last week of 14°F was their coldest temperature in 15 years

• Pullman, WA: Sunday morning's low of -11 degrees was the city's sixth consecutive daily record low and the earliest it has been that cold in 74 years of recordkeeping

• Denver, CO: Record low of -13°F on Wednesday smashed the old record of -5 degrees set in 2008. Thursday's low of -15°F tied the daily record and then Denver dropped to -13 degrees on Saturday morning, tying another record low

• Caspar, WY: Record low of -22°F on Wednesday smashed the old record of -11 degrees set in 1972

• Bishop, CA: recorded a record low of 8°F on Sunday morning

• Spokane, WA: the high temperature held in the teens last week for the first time since 2011

• Ely, NV: Record low of -17°F on Wednesday crushed the old record of -5 degrees. Record lows were also set on Thursday (-23°F) and Friday morning (-19°F).

More bitter cold is in store for much of the nation during the next couple of weeks.

7:00 AM | **A quick dump of 2-4 inches ends at midday**

6-Day Forecast

Today

Cloudy and cold with snow this morning that will come down hard for a few hours, snow ends around midday with accumulations of 2-4 inches, highs in the low 30’s

Tonight

Becoming partly cloudy, very cold, lows near 20 degrees

Wednesday

Mostly sunny, very cold, near 30

Wednesday Night

Mostly clear, very cold, upper teens

Thursday

Mostly sunny and very cold, near 30

Friday

Mostly sunny, cold, mid 30's

Saturday

Mostly cloudy, cold, chance for rain or snow late, near 40

Sunday

Partly sunny, windy, cold, snow showers possible, upper 30’s

Discussion

If you are at work, stay at work; if you are at home stay at home as a wall of snow has moved into the region and it will snow hard through much of the morning. This “fast-moving” and "quick-thumping" system will end by midday after dumping 2-4 inches of snow on the area. Once this storm passes by dry and very cold weather will take over for the Wednesday through Friday time frame. A significant storm will then pull out of the Deep South and head towards the Mid-Atlantic coast this weekend, but it is too early to tell if there will be enough cold air around for snow from that next system so rain is a possibility or some kind of mix.

Video

httpv://youtu.be/AWP36ZHU27I

1:30 PM | **Fast-moving, quick-thumping" snowfall on Tuesday with more accumulations**

Discussion

Here we go again for the Mid-Atlantic I-95 corridor region with more accumulating snow on the way. A temperature gradient boundary zone that has been hanging around the eastern states for several days will again act as a conduit for moisture later tonight and Tuesday. This next batch of moisture will move in a southwest-to-northeast fashion reaching the Mid-Atlantic region early tomorrow. Tomorrow’s event should be primarily, if not completely, in the form of snow in Philly and NYC, but there is a chance that the precipitation begins as sleet in the DC metro region before quickly changing to all snow. Precipitation should break out near or just before daybreak in the DC metro region and then in the early-to-mid morning hours across Philly and NYC. This will be a “fast-moving, quick thumping” type of snowfall with a burst of heavy snow in DC during the morning hours, and in the late morning/mid-day hours in Philly and NYC. The snow should then end quickly from northwest-to-southeast by early tomorrow night.

The upper level pattern for this upcoming event is rather impressive with a strong jet streak playing a key role. It appears that the I-95 corridor region will be in the right/rear quadrant region of a strong upper level jet streak which is conducive to upward motion. Snow accumulations should be on average in the 3-6 inch range from DC-to-Philly, and 2-4 inches in the New York City metro region. We’ll have to see if any small-scale heavier snow bands set up on Tuesday which is quite possible given the expected strong dynamics associated with this powerful upper level jet streak. [12Z NAM 300 millibar winds forecast map for early Tuesday depicting the strong upper level jet streak at 150+ knots across the Northeast US (purple region)].

A few notes about yesterday's snowfall in Philly...Philly Int’l Airport officially recorded 8.6 inches which was only the 8th time in which 8 inches or more has fallen in the month of December and 3 of those 8 events have occurred in just the last 5 years. Also, yesterday's 8.6 inches of snow at PHL was more than recorded for the entire 2012-2013 winter season.

Finally, another storm threatens the Mid-Atlantic region this weekend with more significant snow and/or rain possible.

7:00 AM | **More snow accumulations on Tuesday with several inches likely**

6-Day Forecast

Today

Cloudy and cold with occasional rain or drizzle, highs near 40 degrees

Tonight

Cloudy and cold, maybe a little rain or snow towards dawn, watch for slippery spots on untreated surfaces, lows near 30 degrees

Tuesday

Cloudy, cold, periods of snow with several inches of accumulation possible, low-to-mid 30’s

Tuesday Night

Becoming mostly clear, very cold, low 20’s

Wednesday

Mostly sunny and very cold, mid 30’s

Thursday

Mostly sunny and still very cold, low 30’s

Friday

Partly sunny, very cold, low-to-mid 30’s

Saturday

Cloudy, cold, snow showers possible, mid 30’s

Discussion

Slightly milder air moved in overnight changing our wintry precipitation to plain rain and we'll continue to have some light rain or drizzle for part of the day. More moisture to our southwest will ride up an old frontal boundary zone on Tuesday in a southwest-to-northeast fashion and it looks like it'll be cold enough for primarily snow for this event across the DC metro region. Snow is likely to begin during the early morning hours on Tuesday and continue for much of the day with preliminary accumulation estimates on the order of 3-5 inches. Once this next system passes by, the second half of the week will be dry and very cold for this time of year.

Video

httpv://youtu.be/BhdnmTUmsQM

10:00 AM | ***Accumulating snow has reached DC and is headed to Philly, NYC***

Discussion

The first accumulating snow of the season has arrived in the DC metro region and it will move into the Philly metro region by late morning or early afternoon and then reach New York City by late afternoon or early evening. The general scenario at all three metro regions will be for a several hour period of accumulating snow followed by a several hour period with icing (i.e., sleet and/or freezing rain) and this will add a layer of ice on top of the snow. Finally, enough milder air will move in to change all of the precipitation to plain rain later tonight and early Monday from the immediate I-95 corridor to the coast. Areas north and west of I-95 will see a longer period of frozen precipitation perhaps into the early morning hours on Monday.

Snow accumulations of 2-4 inches can be expected across the DC metro region and I believe this 2-4 inch range, perhaps even isolated 6" amounts, will extend northward to the region between Philly and New York City based on current radar observations which suggest a heavier band of snow will set up later today in that region. Travel conditions will deteriorate for an extended period of time into the overnight hours in all three metro regions given the accumulating snow and ice and with surface temperatures holding at or below the freezing mark. By tomorrow morning, plain rain should help to improve travel conditions along I-95 and to the coast. Stay tuned, tricky forecast.

One final note, there will be snow and/or bitter cold across the board today for the NFL in places like Philly, Baltimore, DC, Green Bay, Denver, etc., etc.

1:15 PM | **Accumulating snow and ice on Sunday/Sunday night throughout the Mid-Atlantic region**

Discussion

The average temperature at 9am this morning across the continental US was 18.0°F which was nearly a degree colder than the lowest average CONUS temperature recorded all of last winter – and winter hasn’t even begun yet. While much of the nation has been in a deep freeze, the Mid-Atlantic region has been quite mild for the past couple of days, but colder air is now oozing into this part of the country following the passage of an Arctic front. Around here, our temperatures will continue to gradually drop this afternoon and evening as rain continues to fall from one wave of low pressure riding along the stalling Arctic frontal boundary zone. By late tonight and early Saturday, it could get just cold enough in the northern and western suburbs for the rain to mix with or change to ice and/or snow before ending early Saturday. More significant snow will fall later tonight across places like central and northeastern Pennsylvania and skiers will be happy for that.

After a break in the action on Saturday, a classic “cold air damming” event will take place on Sunday and Sunday night in the Mid-Atlantic region where cold air funnels southward from high pressure situated to the north. Snow is likely to break out in the morning across the DC metro region, then by mid-afternoon in Philly, and by early evening in the NYC metro region. The DC region could see snow accumulate in the 2-4 inch range before a changeover to sleet and freezing rain adds a singificant layer of ice on top of the snow. The Philly and NYC metro regions could see snow accumulations on the order of ½ to 2 inches before a changeover to sleet and freezing rain adds a significant layer of ice on top of the snow in those locations. Travel conditions will no doubt be adversely affected for an extended period of time during this event in much of the Mid-Atlantic region from Virginia to New York as temperatures hold at or below the freezing mark and significant icing results. Ultimately, by late Sunday night/early Monday, the wintry precipitation changes to plain rain along the immediate I-95 corridor and to points south and east, but it is still a pretty close call and frozen precipitation will very likely last into early Monday just to the north and west of the big cities.

7:00 AM | **Significant winter weather event on Sunday with snow and ice accumulations**

6-Day Forecast

Today

Cloudy with periods of rain, after peaking early in the day temperatures will fall through the afternoon reaching the mid 40’s by day’s end

Tonight

Cloudy with periods of rain, there is a small chance that the rain could mix with or change to sleet and/or snow after midnight well to the N and W of the District before winding down, lows by morning in the low-to-mid 30’s

Saturday

Becoming partly sunny, cold, breezy, low 40’s

Saturday Night

Mostly cloudy, colder, upper 20’s

Sunday

Cloudy with snow arriving during the morning hours then mixing with or changing to sleet and freezing rain, up to a couple inches of snow and ice accumulations are possible on Sunday with tricky travel conditions for awhile, mid 30’s

Monday

Mostly cloudy, cold, rain likely, mid 40’s

Tuesday

Mostly cloudy, windy, cold, chance for some rain or snow early in the day, mid 30’s

Wednesday

Partly sunny, very cold, near 30

Discussion

An Arctic front that has been progressively sweeping across the nation will slow down and then stall out today in a southwest-to-northeast fashion near the east coast allowing for a couple waves of low pressure to ride along its temperature gradient boundary zone. The first wave will generate periods of rain around here today and tonight and as the colder air continues to filter into the region in the overnight hours, there is a small chance that the rain could mix with or change to sleet and/or snow in the far northern and western suburbs before ending.

After a break in the action on Saturday, a classic "cold air damming" event will take place on Sunday and Sunday night. Another wave of low pressure will spread wintry precipitation into the region on Sunday that will continue into Sunday night before changing to plain rain. The current thinking on the timetable and precipitation type is as follows (subject to change): snow is likely to arrive during the morning hours and then it should mix with or change to sleet and/or freezing rain before a change to plain rain later Sunday night. Accumulations of up to a couple of inches of snow and ice are possible on Sunday and travel can get tricky for awhile as there is likely to be an extended period with temperatures near the freezing mark. By Monday, milder air should win out along the I-95 corridor where the precipitation is likely to fall as plain rain, but not too far to the north and west of the big cities, frozen precipitation could linger. By Tuesday, the next Arctic invasion will begin and very cold conditions will persist through the mid-week in the Mid-Atlantic region as well as across much of the country. [A detailed video description of "cold air damming" is available on our "Meteorology 101" page].

One final interesting tidbit: there is a report this morning that the 8am average temperature across the continental US was 18.1 deg F which is colder than at any time during last winter. According to weatherbell.com, the lowest average CONUS temperature at any time last winter was 18.9 deg F.

Video

httpv://youtu.be/ZZNm_JFtR0A

1:45 PM | **Amazing weather across the western 2/3 of the nation; two chances for wintry precipitation in the Mid-Atlantic region this weekend**

Discussion

Quite an incredible weather pattern across the western two-thirds of the nation during the past couple of days and some of the fun will spread to the eastern states this weekend. From California to Texas to the Great Lakes, there has already been an influx of brutal Arctic air and some of these areas have received a boat load of snow to go along with it. In addition, one of the worst ice storms in years is now unfolding in the region between Texas and Kentucky and icing problems are likely to hit the Mid-Atlantic I-95 big cities later this weekend…more on that threat below. Here are a few of the highlights of this amazing winter weather across the nation in the last 48 hours or so:

1) West Yellowstone, Montana reached 31 degrees below zero 2) Denver set a record low on Wednesday of 13 degrees below zero which shattered the old record by a whopping 8 degrees. Denver bottomed out at 15 degrees below zero this morning which is the coldest ever this early in the season. All of this bitter cold was accompanied by several inches of snow in the metro region. 3) Record low temperatures, frost and hard freezes hit California this morning and will again early tomorrow. Also, significant snow will fall in some of the California higher elevations later today and tonight. 4) More than 30 inches of snow fell in some areas between the Colorado Rockies and upstate Minnesota.

There are two shots at wintry precipitation in the I-95 corridor between DC and NYC during the upcoming weekend. The first shot will come late Friday night/early Saturday morning as rain winds down from one low pressure system. Temperatures will likely peak tomorrow morning and then will drop during the afternoon and evening hours on Friday in this region. By late tomorrow night, just as the precipitation is ending, it is possible that the rain mixes with or changes to sleet and/or snow in the northern and western suburbs of the big cities.

The second threat comes on Sunday and this one is a more significant threat than the first one. This appears to be setting up as a classic "cold air damming" event with very strong Arctic high pressure system situated in the Northeast US by Sunday that will act as an anchor for dense, cold low-level air which will be able to penetrate southward on the eastern side of the Appalachian Mountains. Snow, sleet and freezing rain is likely to reach the DC metro region on Sunday morning, and then Philly by Sunday afternoon, and New York City by Sunday evening. The snow will likely not be a big player in these areas during this upcoming event; however, the icing could last for an extended period as temperatures will only grudgingly rise above the freezing mark. By late Sunday night or early Monday, enough milder air should move into the big cities to change the precipitation to plain rain, but it is still a close call, and areas just to the N and W of I-95 may hold onto frozen precipitation for awhile longer on Monday. More Arctic air moves into the Mid-Atlantic region for Tuesday and Wednesday.

Finally, it is not often one sees a 6-10 day temperature forecast by NOAA (above) with colder-than-normal weather (blue) expected from coast-to-coast.

7:00 AM | Very mild today, but colder this weekend and Sunday will feature ice/snow before a changeover to rain

6-Day Forecast

Today

Mostly cloudy, mild, highs in the mid 60’s

Tonight

Mostly cloudy, cool, occasional showers, lows by morning in the low 50’s

Friday

Mostly cloudy, cooler, rain likely, highs in the lower 50’s during the morning hours and then temperatures drop in the afternoon

Friday Night

Mostly cloudy, colder, rain likely, possibly mixing with sleet and/or snow in the northern and western suburbs before ending, low-to-mid 30’s

Saturday

Some sun followed by thickening clouds, cold, near 40

Sunday

Mostly cloudy, cold, ice, snow and/or rain, mid 30’s

Monday

Mostly cloudy, cold, rain likely, upper 40’s

Tuesday

Partly sunny, windy, cold, mid-to-upper 30’s

Discussion

Very cold air has gripped the nation from California to Texas to the Great Lakes, but here in the East, mild air has made a return. In fact, today will be the mildest day of the week, but this warm up will be rather short-lived. After a day with highs near 65 degrees, a strong cold front will slide through the region by early tomorrow and reverse our temperature trend. In fact, temperatures may peak in the morning on Friday and then drop slowly during the afternoon hours. This gradual transition from mild-to-cold will be accompanied by periods of rain from tonight into tomorrow night. It could get just cold enough by late tomorrow night for the rain to mix with or change to sleet and/or snow before ending in some of the northern and western suburbs.

After a dry Saturday afternoon and early evening, attention will turn to the Deep South as moisture will head our way from that part of the country at the same time strong Arctic high pressure settles in to our north. The end result could be an extended period of ice in this area as there will likely be below freezing temperatures at ground level, but above freezing in the upper parts of the atmosphere. The precipitation is likely to change to plain rain by Sunday night or early Monday and then we’ll be looking to our northwest for the arrival of another very cold Arctic air mass on Tuesday.

1:00 PM | *Ice/snow threat continues for Sunday*

Discussion

The threat continues for a period of ice and/or snow on Sunday in much of the Mid-Atlantic region before a likely changeover to plain rain. Strong high pressure will set up shop to our north by Sunday morning and it will anchor a cold, dense Arctic air mass that will have no trouble advancing southward on the eastern side of the Appalachian Mountains and into the big cities from DC to NYC. This classic “cold air damming” setup often leads to icing around here, at least for a several hour period, as milder, moist air is initially forced aloft on top of the cold, dense surface air. The 12Z GFS model run suggests that while the surface freezing line will be way down across southeastern Virginia come Sunday morning, above freezing air will already be working its way to the north in the upper part of the atmosphere. This potential setup will likely lead to a several hour period of frozen precipitation in much of the region in the form of sleet, freezing rain and/or snow before the milder air finally wins out and changes the precipitation to plain rain – at least from I-95 to the coast. Surface cold air will hang on even longer across places like central and northeastern Pennsylvania and an extended ice storm is a real threat in those areas. One final note, there has been a slight trend towards a colder and colder solution for this upcoming event and we’ll continue to monitor that over the next few days.

Video

httpv://youtu.be/1cwVdp79fy0