1:15 PM | **Late week accumulating snow and bitter cold**

Discussion

The potential continues for an important accumulating snow event on Thursday and Thursday night in the Mid-Atlantic region, but the question is still open as to whether this will be a moderate storm or something more significant. The ingredients that are on the playing field do indeed have the potential to generate a major snowstorm in the Northeast US, but the details of the storm evolution are still to be ironed out. The ingredients that will be part of this developing storm system include the following: (1) an active sub-tropical jet [see water vapor image above] (2) vigorous energy in the upper atmosphere dropping southeastward from western Canada (3) an associated strong upper-level jet streak (4) an upper level low over southeastern Canada that will force that vigorous energy towards the east coast and (5) strong high pressure situated to the north that will be anchoring an Arctic air mass.

It appears that initially there will be multiple low pressure centers in the eastern US on Thursday and then one of these will consolidate near the Mid-Atlantic coastline as the upper level trough approaches the eastern seaboard. The exact timing and phasing of this surface system will determine the extent of the snowfall in the Mid-Atlantic region later Thursday and Thursday night. In terms of the timetable for this upcoming event, while there can be some snow as early as late Wednesday night and Thursday morning, the heaviest snow would likely occur from late Thursday afternoon through Thursday night. In terms of precipitation type, while it is possible that some rain mixes in at the onset of this storm, the majority should fall as snow from the I-95 corridor to points north and west as it will become increasingly colder. In fact, snow can be expected all the way to the coastline as it becomes colder during the duration of the storm. Snow-to-rain ratios, which are normally around 10-to-1, will likely become as high as 15-to-1 in places like NYC as colder air takes over in the upper atmosphere during this storm. Very preliminary snow accumulations estimates are as follows: coating to 2” in the northern and western suburbs of Washington, DC, 2-5” in the Philly metro region, and 5-8” in and around NYC. Bitter cold air follows on Friday and Friday night with low temperatures by early Saturday morning perhaps near 0 degrees in the Philly metro region and even below zero near NYC. Looking ahead, another bitter - and perhaps record-breaking - cold air outbreak will reach the Mid-Atlantic region around Tuesday of next week. A detailed breakdown of the 12Z GFS model run and how it handles all of these ingredients can be viewed in the latest video discussion (below). One final note, in terms of playoff football, temperatures will probably be around 20 degrees at kickoff time for the Eagles game on Saturday in South Philly against New Orleans.

Video

httpv://youtu.be/ZwDzmQv9lcM

1:15 PM | **Snowstorm potential later this week and brutal cold air to follow**

Discussion

Quite an amazing looking weather pattern is shaping up for the central and eastern US during the next few weeks that will bring bitter cold air masses – perhaps even historic cold in some areas - as well as several storm threats. Temperatures today are below zero throughout a good portion of the Upper Midwest and this Arctic air outbreak is only the first of several that will punish the eastern half of the nation well into the month of January. Temperatures in the Mid-Atlantic region will drop to quite cold levels by New Year’s Day (Wednesday) and then attention will turn to a potential snowstorm in the Northeast US from later Thursday into early Friday. The latest GFS model run (12Z) has shifted to a colder solution than its prior runs as the main upper air feature involved in this upcoming event is now coming into better focus for the computer forecast model. In fact, the GFS model forecast now depicts significant accumulating snow in the Mid-Atlantic region – even as far south as the DC metro region. This scenario looks like a classic setup as it will feature a powerful upper-level jet streak (300 mb forecast map above) with major Arctic air intrusion and a banana-shaped high pressure system sitting to the north. The timetable for this late week event in the Mid-Atlantic region is from later Thursday into early Friday with possibly the brunt of the storm on Thursday night. No matter how much snow falls from this storm, there is sure to be bitter cold air in its wake. In fact, temperatures could drop to 0 degrees in parts of the I-95 corridor by early Saturday morning on top of a fresh snowpack. Furthermore, there are signs for another incredibly cold Arctic air outbreak by the middle part of next week. Stay tuned.

Video

httpv://youtu.be/zii5KNQqmGg

7:00 AM | *Cold air returns over the next couple of days; snow/rain threat later this week*

6-Day Forecast

Today

Mostly cloudy, becoming breezy, chilly, highs peak this morning in the mid 40's

Tonight

Mostly clear, cold, lows in the mid 20’s

Tuesday

Partly sunny, cold, near 40

Tuesday Night

Partly cloudy, quite cold, low 20’s

Wednesday

Mostly sunny, cold, upper 30’s

Thursday

Becoming cloudy, cold, snow and/or rain likely, near 40

Friday

Partly sunny, windy, very cold, windy, mid-to-upper 20's

Saturday

Partly sunny, cold, mid 30’s

Discussion

Temperatures are currently well below zero across portions of the Upper Midwest and the overall weather pattern shaping up for the next few weeks looks to be very cold for much of the eastern half of the nation. In fact, there could be some historic cold air outbreaks as we progress through the first half of the month of January in parts of the central and eastern US. Around here in the short-term, temperatures will get colder by the time New Year's Day (Wednesday) rolls around and then we will likely have to deal with a winter storm from Thursday into Thursday night. The details still need to be ironed out for this late week storm as there could be a mixture of snow and rain. Very cold air will follow this storm at the end of the week and more storms and even bitter cold are likely through the first half of January for much of the central and eastern US. In fact, the next storm threat for us comes early next week and that system is likely to be followed by some bitter cold air.

2:30 PM | *Wintry week in store for the region with cold and snow in the offing*

Discussion

After a mild Saturday and a very rainy Sunday (1-1.5"), the weather in the Mid-Atlantic region will look much more like winter during the upcoming week with cold and snow in the offing. Much colder air will move into the Mid-Atlantic region by Tuesday and temperatures will be confined to well below normal levels during the mid-week time frame. By Thursday, an area of low pressure is likely to be moving over the Ohio Valley and then it should consolidate into a strong system near the Mid-Atlantic coastline. This system, combined with a strong, cold high pressure system to our north, will raise the odds for significant accumulating snow in the I-95 corridor from Thursday into early Friday; especially, north and east of the PA/MD border. The potential is certainly there for a widespread winter storm event as this scenario looks like a classic setup as it will feature a double upper-level jet structure with major Arctic air intrusion and a banana-shaped high pressure system sitting to the north. Once this strengthening storms pulls of the Northeast US coastline on Friday, bitter cold air is likely to follow into the Mid-Atlantic region at the end of the week. Stay tuned.

7:00 AM | Rain on Sunday will be followed by very cold air by mid-week

6-Day Forecast

Today

Mostly sunny, chilly, highs near 45

Tonight

Mostly clear, cold, lows in the upper 20’s

Saturday

Partly sunny, milder, low 50's

Saturday Night

Partly cloudy, cold, low-to-mid 30’s

Sunday

Mostly cloudy, chilly, periods of rain, low 40’s

Monday

Becoming partly sunny, cold, near 40

Tuesday

Partly sunny, colder, low-to-mid 30’s

Wednesday

Partly sunny, very cold, near 30

Discussion

A cold front passed through the region on Thursday causing a burst of snow during the morning hours in parts of the I-95 corridor. High pressure will build back into the area for today and tomorrow and then an area of low pressure will move northeastward from the Gulf of Mexico later this weekend. Rain is likely on Sunday from this system and then high pressure will return early next week bringing more chilly weather to the region. In fact, by New Years Day (Wednesday), temperatures may struggle to get out of the 20's.

Video

httpv://youtu.be/ssP47o-nFlA

12:00 PM | Weather and the Battle of Trenton on December 25-26, 1776

Discussion

Morale was low, hope for winning the war was diminishing, and the cause for independence was fading in December of 1776. The Continental Army led by George Washington was thinning in numbers after many battles lost to the British. December began with lots of rain and muddy travel conditions for the men which did not help with their spirits. After retreating through New Jersey, they set up camp in Valley Forge, Pennsylvania where the army was met with very cold weather that led to plenty of ice on the Delaware River. All in all, things were not looking good for Washington's army.

However, George Washington devised a plan that would change the course of the war and the history of our nation. With only a week before his soldiers' enlistments expired, Washington had to do something fast. He decided he would attack Trenton, New Jersey, which the Hessians (German soldiers fighting with the British) controlled. He planned to cross the Delaware River on Christmas Day and invade Trenton before sunrise on December 26th. Washington thought this action could catch the Hessians off guard and create a better possibility of victory, thereby boosting the morale of his army.

So the day came, Christmas 1776. The weather was actually quite tranquil for most of the day. The morning started off with a mixture of sun and clouds, very cold temperatures in the upper teens, and light northerly winds. By the afternoon, clouds started to increase with temperatures now peaking in the upper 20s. These clouds were associated with a powerful nor’easter that was rapidly strengthening off the coast. This storm brought freezing rain to the Delaware Valley that then changed to sleet and snow. The crossing of the river began at 5pm on the 25th with temperatures in the upper 20s. As the 2,400 soldiers, 18 cannons, and 75-100 horses crossed the Delaware, they had to deal with the icy river conditions. During the crossing, one of the soldiers described the weather conditions as a “violent storm of rain, hail, and snow [the nor’easter] coupled with the ice flows and high winds, slowed operations.” Meanwhile, George Washington patiently watched his soldiers implementing his dramatic plan in these extreme conditions. One of his officers wrote, “He [Washington] stands on the bank of the stream, wrapped in his cloak, superintending the landing of his troops. He is calm and collected, but very determined. The storm is changing to sleet and cuts like a knife.” All the men finished crossing the river at 3am on the 26th, 3 hours behind schedule due to the weather and sheets of ice on the river. The plans to attack under cover of darkness were ruined, but Washington and his men marched to Trenton anyway, undeterred by the conditions.

Temperatures were now in the low 20s with wind driven snow and sleet coming down as the march continued to Trenton. Many soldiers were suffering and one even froze to death during the 9 mile trek. At 8 AM, hidden by heavy snow, the surprise attack on the Hessians began. Although the sleet and snow provided cover, it also made many of the muskets misfire, so cannons and bayonets were used by Washington’s forces. Washington’s plan had worked and the American army captured 900 Hessians with only a few revolutionary troops wounded. Trenton had been taken and the fight for Independence would survive.

In the end, Washington and his army endured the extreme weather conditions and the weather conditions helped with the surprise attack since the Hessians did not expect an assault in such weather. This is now thought of as the turning point in the American Revolution and another example of how weather influenced history.

7:00 AM Wet weather as we transition back to cold; snow showers possible later Christmas Eve

6-Day Forecast

Today

Mostly cloudy with periods of rain, heavy at times, temperatures falling through the day reaching the 40’s by early evening

Tonight

Mostly cloudy, colder, showers ending early, lows in the upper 20’s

Tuesday

Partly sunny, breezy, cold, chance for snow showers, near 40

Tuesday Night

Partly cloudy with snow showers possible during the evening, very cold, near 20

Wednesday

Mostly sunny, very cold, low 30’s

Thursday

Partly sunny, not as cold, low 40’s

Friday

Partly sunny, cold, upper 30’s

Saturday

Partly sunny, cold, near 40

Discussion

Yesterday’s warmth will give way to another cold shot of air and the transition will bring some heavy rain to the region. By tomorrow, temperatures will be confined to the 30’s and an upper level disturbance could bring some snow shower activity to the area. Christmas Day will be very cold for this time of year with temperatures holding to near freezing for highs.

12:15 PM | "An island of warmth in an ocean of cold"...big changes coming early next week

Discussion

After possible record-breaking warmth on Sunday in the I-95 corridor, big changes are coming early next week that will bring a return to an overall cold weather pattern likely to last right into 2014. A strong cold front will drift slowly southeastward on Monday and it’ll get hung up along the east coast as low pressure develops along a rather tight temperature gradient frontal boundary zone. Periods of rain are likely on Monday as colder air slowly filters into the Mid-Atlantic region. There is even a small chance that the rain changes to light snow before ending on Monday night in areas north of the PA/MD border as the cold air finally makes a significant push into the region.

Tuesday (Christmas Eve) is looking like it’ll be a far cry from Sunday which will be the culmination of the current warm spell. In fact, temperatures on Tuesday will do no better than the 30’s for highs in most Mid-Atlantic locations after possibly reaching the 70 degree mark on Sunday. There will also be a noticeable chilly breeze later Tuesday and an upper-level disturbance threatens to bring some snow shower activity to portions of the Mid-Atlantic region. The cold weather will be firmly entrenched in the region by the time Christmas morning rolls around and numerous Arctic air outbreaks are in the offing as we close out the month of December and begin 2014. In fact, the GFS computer forecast model has been consistently generating brutal Arctic air outbreaks at the end of the month and into the first week of 2014 for the northern US and, given the overall weather pattern, this is quite believable.

7:00 AM | Very mild weekend, but colder air returns for Christmas Eve and Christmas Day

6-Day Forecast

Today

Mostly cloudy, very mild, highs near 60 degrees

Tonight

Mostly cloudy, mild, lows near 45 degrees

Saturday

Mostly cloudy, even milder, mid 60’s

Saturday Night

Mostly cloudy, mild, upper 50’s

Sunday

Mostly cloudy, very mild, showers likely later in the day and at night, cannot rule out a thunderstorm, low 70’s

Monday

Mostly cloudy, turning cooler, showers still possible, low-to-mid 50’s

Tuesday

Mostly sunny, colder, near 40

Wednesday

Partly sunny, cold, near 40

Discussion

Our major warm up will peak on Sunday afternoon with high temperatures on that day likely reaching the 70 degree mark. A strong cold front will increase our chances for showers on Sunday; especially, during the latter part of the day and at night. That threat of showers will continue into Monday as well as cooler air filters into the region. By Tuesday (Christmas Eve), the cold air will be firmly established around here and high temperatures will be close to 40 degrees and that chill will continue on Christmas Day. Looking ahead, a cold pattern is quite likely as we close out the month of December and begin the new year.

Video

httpv://youtu.be/tEOxvKjO3Vg

7:00 AM | 70+ degrees likely on Sunday; much colder air returns by Christmas Eve (Tuesday)

6-Day Forecast

Today

Mostly sunny, milder, highs near 55 degrees

Tonight

Mostly cloudy, chilly, lows near 40 degrees

Friday

Partly sunny, even milder, near 60

Friday Night

Mostly cloudy, cool, near 45

Saturday

Mostly cloudy, very mild, low-to-mid 60’s

Sunday

Mostly cloudy, very mild, rain likely, low 70’s

Monday

Mostly cloudy, colder, showers still possible, low 50’s

Tuesday

Mostly sunny, even colder, near 40

Discussion

A major warmup has begun and it will culminate on Sunday afternoon with high temperatures likely to reach the lower 70s. The mild weather will also bring some shower activity to the region with an increasing threat as the weekend progresses and fog could break out given the combination of the milder air and still-cold grounds. The mild weather will come to an end early next week following the passage of a strong cold front. Much colder air begins to filter into the region on Monday, but will be fully felt around here by Christmas Eve (Tuesday). Highs on Tuesday and Wednesday (Christmas Day) will likely be confined to near 40 degrees. Longer term, there are signs for very cold weather as we close out the month of December and begin the new year.

Video

httpv://youtu.be/WOrEaRiaObc