Vencore Weather
3Mar/15Tue

7:00 AM | **Another round of snow and/or ice later today…milder tomorrow with plain rain…significant snow possible on Thursday**

6-Day DC Forecast

Today

Cloudy, cold, snow or a wintry mix breaks out during the early-to-mid afternoon hours, slick travel conditions possible for the evening commute with a coating to an inch of snow and ice accumulations, highs in the low-to-mid 30’s

Tonight

Wintry mix changes to plain rain as temperatures slowly rise, some fog possible late

Wednesday

Becoming noticeably milder with rain likely at times, some fog possible, quite breezy, near 50 degrees

Wednesday Night

Rain likely early, but it should change to snow by morning, turning colder, mid-to-upper 20’s by morning

Thursday

Snow likely with significant accumulations, much colder than Wednesday, upper 20's for highs

Friday

Mostly sunny, breezy, very cold, upper 20's

Saturday

Mostly sunny, still cold, but not as harsh, low 40's

Sunday

Mostly sunny, chilly, near 45 degrees

Discussion

Clouds will thicken up this morning and another round of snow and/or ice is headed our way. Precipitation should break out by early afternoon - probably as a mix of snow and sleet - and then freezing rain will likely mix in by the end of the day. There can be some slick travel conditions for the evening commute with a coating to an inch of snow/ice accumulations possible. The wintry mix should change to plain rain during the evening hours as temperatures rise slowly and some fog is possible late. Wednesday promises to be a milder day with occasional rain and some fog; however, the more important story will be the approach of yet another Arctic cold frontal system. That front will pass through the region late Wednesday and this will begin a downward trend in temperatures that could set the stage for significant snow on Thursday.

Once the Arctic front reaches the east coast, it will stall out due to the alignment of the upper-level winds which will prevent any significant movement to the southeast. At the same time, copious amounts of moisture will begin heading northeast along the stalled out frontal boundary zone and colder air will be pushing in from the northwest. The result could very well be a significant snow event on Thursday with preliminary estimates in the 4-8 inch range for the I-95 corridor. Very cold weather closes out the work week.

Video

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2Mar/15Mon

1:30 PM | ****Wow, talk about “coming in like a lion”!!****

I_nw_g1_EST_2015030212_076
[12Z Canadian model forecast map for mid-day Thursday (blue=snow].

Discussion

Overview
March began with snow and ice on Sunday, more snow and/or ice is coming for tomorrow afternoon and evening and then, after a temporary warmup on Wednesday, a significant snow event is possible from late Wednesday night into Thursday. Before we get into the details on the very active next few days, let us first throw out some new numbers regarding the amazingly cold February which just ended.

February recap for DC, Philly, NYC
At Reagan National Airport in Washington, DC (DCA), February 2015 was the coldest month at any time of the year since January 1994. DCA saw seven days completely below freezing which is the most in any month since 1979. Dulles Airport in Virginia (IAD) recorded its 2nd coldest February ever and BWI Airport in Maryland saw its coldest February since 1934 (source Washington Post/Capital Weather Gang).

In Pennsylvania, February 2015 was the coldest February ever in State College, Erie, Williamsport and Harrisburg. At Philly International Airport (PHL), this was the 7th coldest February ever recorded going back to 1874 and the coldest month at any time of the year since December 1989 (source phillywx.com).

In New York City, February 2015 turned out to be the third coldest February ever and the coldest since 1934. It was the 2nd coldest February ever recorded in Newark, NJ.

Finally, here is just a sampling of places which set their all-time monthly (cold) temperature records: Buffalo (NY), Islip (NY), Hartford (CT), Bridgeport (CT), Syracuse (NY) and Bangor (ME).

Tuesday afternoon and evening - snow, ice threat
After a very cold night in which temperatures drop into the teens, clouds will thicken up early Tuesday ahead of the next precipitation event. Precipitation is likely to break out during the mid-day or early afternoon hours in DC, mid-to-late afternoon hours in Philly and New York City, and it should be cold enough for that initial precipitation to be of the frozen variety. In DC, the precipitation could start as all snow, but a wintry mix is more likely whereas in Philly and NYC the precipitation is liable to begin as all snow. In all areas, any initial snow will change over to a wintry mix fairly quickly later tomorrow or early tomorrow night and, yes, there can be some snow and ice accumulations by midnight. Temperatures tomorrow night should slowly rise and any mixed precipitation is likely to change to plain rain by early Wednesday.

Wednesday – milder with plain rain
Wednesday promises to be a milder day with periods of rain. Temperatures could even flirt with the 50 degree mark on Wednesday in portions of the I-95 corridor. The more important story; however, will be the approach of another Arctic cold frontal system. This front will pass through the region late Wednesday and this will begin a downward trend in temperatures that could set the stage for significant snow on Thursday.

Late Wednesday night/Thursday – potential significant snowfall
Once the Arctic front reaches the east coast, it will stall out due to the alignment of the upper-level winds which will prevent any significant movement to the southeast. At the same time, copious amounts of moisture will begin heading northeast along the stalled out frontal boundary zone and into the I-95 corridor. At the same time, colder air will be pushing in from the northwest and the result could very well be a changeover rain early in the day to an accumulating snow and significant accumulations are possible up and down the I-95 corridor.

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2Mar/15Mon

7:00 AM | ***Week starts off on the cold side…much milder by mid-week, but the warm up will be short-lived and preceded by a wintry mix and then plain rain…cold air returns later this week possibly with significant accumulating snow on Thursday***

6-Day DC Forecast

Today

Becoming partly sunny after early clouds, winds will intensify at mid-day and for the afternoon, cold, highs in the low 40’s

Tonight

Partly cloudy, quite cold, lows in the lower 20’s

Tuesday

Becoming cloudy, cold, snow or a wintry mix arrives during the afternoon, mid-to-upper 30’s

Tuesday Night

A wintry mix becomes plain rain, cold, but temperatures should slowly rise through the 30's

Wednesday

Becoming noticeably milder with showers likely early, breezy, low 50’s

Thursday

Cloudy, breezy, much colder, rain changes to snow early with significant accumulations possible, low-to-mid 30’s

Friday

Mostly sunny, cold, mid 30’s

Saturday

Mostly sunny, milder, mid 40’s

Discussion

Our active weather pattern will continue for the next several days with a potpourri of weather conditions including snow, sleet, freezing rain, plain rain, and the chance for a substantial snow accumulation. The new work week start off on the cold side and the winds will intensify during the mid-day and afternoon hours. After a very cold overnight, clouds will thicken up early Tuesday and snow or a wintry mix is likely to arrive during the afternoon hours. Incoming milder air will gradually change the precipitation to plain rain tomorrow night as temperatures slowly rise through the 30's. Wednesday promises to be quite mild ahead of the next Arctic frontal system with periods of rain and temperatures reaching the 50 degree mark.

That Arctic frontal system will slow down as it reaches the east coast and will set off a chain of events that could bring a significant snowfall to the I-95 corridor. Copious amounts of moisture will ride along the frontal boundary zone Wednesday night and Thursday as colder air pushes into the Mid-Atlantic region. This type of setup could feature a cold rain that changes to snow by early Thursday with significant accumulations possible. Very cold conditions will follow for the end of the work week.

Looking ahead, next weekend looks to be moderately cold and then another shot of Arctic air is possible early next week. Beyond that, there are signs for an important break in the pattern centered around the middle of the month with several days of milder weather conditions. However, it is quite likely that we'll return to a colder-than-normal pattern - perhaps stormy as well - during the latter part of the month and going into April.

Video

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1Mar/15Sun

8:45 AM | ***Accumulating snow and the threat for a significant buildup of ice***

us3comp
[US radar image with plenty of moisture headed to the Mid-Atlantic region; NEXRAD image courtesy University of Wisconsin]

Discussion

Overview
Dense, cold Arctic air sits on top of the Mid-Atlantic region this morning and copious amounts of moisture (radar map) is streaming in from the west – a bad combination that spells big trouble for the I-95 corridor region from DC-to-Philly-to-NYC. Accumulating snow is likely in all areas along I-95 at the onset of today's precipitation event, but that ultimately will not be the biggest problem. Milder air moving northward in the upper part of the atmosphere will generate a changeover from the snow to sleet and then to freezing rain in most areas and there can be a significant buildup of ice on untreated surfaces (e.g., trees, grass, untreated roadways) with slick travel conditions. While the upper atmosphere turns milder, the dense, cold and below-freezing Arctic air at ground level will be reluctant to retreat; thereby, setting the stage for some serious ice buildup later today and early tonight in portions of the area.

Details
Snow is likely to break out by mid-morning in the DC metro region perhaps even mixed with some sleet in southern sections, in the late morning to mid-day hours across Philly, and then during the early afternoon in the NYC metro region. Then, after a period of accumulating snow, there will then be a transition later today from south-to-north of the snow to sleet and then to freezing rain although snow will hang on for much of this event in higher elevation locations north of I-80 (e.g., NE PA). Before the changeover to ice, snow should accumulate from a coating to an inch or two in and around the DC metro region, 1-3 inches in the Philly metro region, and 2-4 inches in the NYC metro region. The higher amounts in those snowfall accumulation estimates will occur to the north in a given metro region and the lesser amounts to the south. A significant ice-buildup (quarter to half an inch) is possible later today into early tonight in the entire I-95 region from DC-to-Philly-to-NYC. Precipitation winds down by or shortly after midnight in most of the I-95 corridor.

“Banding” could enhance snow (or ice) totals in parts of the area
One final word of caution on today’s event…there will be an impressive thermal gradient in the Mid-Atlantic region and strong upward motion in the atmosphere as a powerful upper-level jet streak (purple area on 300 millibar map) plows through the region from west-to-east. As a result, in this type of dynamic atmosphere, “banding” is likely to develop in the precipitation field later today causing varying rates of precipitation and there could be an enhancement of the snow (or ice) in a given area in a short period of time. We’ll monitor the precipitation pattern as the day progresses and make adjustments to accumulation totals if necessary.

300mb_sf
[Sunday AM 300 millibar winds showing powerful jet streak (purple) which is headed right into the Mid-Atlantic region; courtesy NOAA]

Another interesting and complicated threat at mid-week
Another complicated precipitation event is likely to occur in the I-95 corridor from Tuesday into Thursday. Precipitation ahead of another strong Arctic frontal system is likely to arrive late Tuesday and it could start as a wintry mix in the I-95 corridor. However, as milder air pumps in from the south, the precipitation is likely to change to plain rain for Tuesday night and early Wednesday and some of the rain can be heavy. Temperatures could climb into the 50’s in portions of the I-95 corridor during the day Wednesday before colder air returns. The Arctic frontal system may then stall as it reaches the east coast on Wednesday night and there is a chance low pressure develops along the frontal boundary and rides up along it into the I-95 corridor region. If this takes place, it could very well turn cold enough for significant snow around here in the late Wednesday night/Thursday time frame. Stay tuned on that one.

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