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Seasonable pattern to gradually transition to cold and active

Yet another period of rain hit the area last night, which has been a staple of the weather pattern this month. No big Arctic air intrusions as the Arctic air has remained bottled up near the Poles, and plenty of rain. Today was a mild afternoon as westerly flow in a merely stale chilly airmass led to downsloping flow and temperatures in the low 50s. Temperatures so far this month have actually been running around seasonable or only slightly above normal, but without true plunges of cold air and warmth in Canada, snow has been hard to come by.

This theme is expected to continue for the next week or so as the pattern finally truly shuffles and transitions to one where Arctic blasts are much more frequent across the US. But in the transition period itself, snow is generally still tough to come by.

Cold air advection will finally take shape tonight as temperatures aloft drop. But in a stale airmass, temperatures will generally only fall to around freezing in suburbs, and mid 30s in urban areas. This is a few degrees above average.

Moving forward to tomorrow, the airmass will be moderately chilly, but once again a northwesterly flow will downslope and help temperatures warm into the mid to upper 40s for most regions. Skies will remain mostly sunny throughout the day, with perhaps a few more clouds during the afternoon — though not a true overcast like we saw this afternoon. It will also be a bit blustery at times as well, with winds between 10 and 20mph.

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Changing pattern could lead to multiple storm threats

We warned you that this was coming. Now, the pattern change is finally beginning to appear on medium and long range model guidance from late December into January. Thanks in part to changes in the stratosphere and retrograding mid and upper level atmospheric features, the pattern over the next week or two will become much more favorable for not only colder than normal air, but winter weather in our area as well. Contrary to what it may seem, the pattern currently is quite unfavorable for cold air and winter weather. Warmer than normal air has settled in to Southern and Central Canada over the past week or so, muting any potential shots of cold air with northwesterly winds.

But the notable feature around the Northern Hemisphere will begin retrograding over the next several days. It begins with the troughiness over the Gulf of Alaska and ridging in the Eastern Pacific. Both of this features will progressively retrograde westward over the next 7-10 days. The end result will bring a mean trough to the Aleutian Islands and a ridge to the West Coast of the United States and British Columbia (also known as a +PNA). Further securing the changing pattern will be the development of a +EPO ridge in Western Canada and the potential for ridging to develop over Eastern Canada, Greenland and the Western Atlantic.

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Gradually improving, slightly warmer weather

The same mid-level cutoff low that helped bring the heavy rain and strong winds on Tuesday, as well as multiple days of snow showers since, is still meandering in the vicinity of the Northeast US today. This has helped to keep an island of cold in an otherwise sea of warmth across much of the US, as well as instability and moisture to produce wrap-around snow showers.

Impressive lapse rates have remained over the region over the past few days, allowing for the continuation of snow showers and squalls. They’ll be much more isolated on Friday, however, as the upper level low finally begins to pull away. As it does so, it will remove our area from the pocket of stronger instability. So, we expect highs in the upper 30’s to near 40 on Friday with a much lower chance of snow showers — in fact, cloudy to partly cloudy skies should be the general rule.

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Multi-hazard Nor’Easter expected Tuesday

A significant storm system, characterized by a deepening low pressure with prolific moisture, will move from the Western Atlantic to a position very near New York City on Tuesday. As a result of a mid level atmospheric phase, the storm system will feature intense mid and upper level dynamics. The system is forecast to strengthen with a minimal central pressure near 1012mb today, falling into the mid 990’s mb by Tuesday. With a storm track near our area, and the dynamics involved in the system, multiple weather hazards are anticipated both near our area shores and even inland throughout the interior portions of the area.

Precipitation could begin as early as Monday morning along the coasts of New Jersey and New York as moisture streams inland, owing to an onshore flow. But as the storm system is tugged inland from the Western Atlantic, as a result of the phase in the mid levels of the atmosphere, warm air advection and increased moisture will surge heavier and steadier precipitation toward the coast and eventually into New York City, New Jersey, Southeast New York and Connecticut. Enough low level cold air could hold on across the higher elevations of the interior to allow precipitation to begin as snow, sleet or freezing rain — but this will only be brief as mid level and low level warming transitions precipitation to rain quickly.

The event will create multiple potential hazards throughout our area on Tuesday as the low pressure system tracks nearby. We’ve broken them down here.

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Coastal storm likely early next week

Although it may seem like we’re beating the same old drum, here we are again — a significant coastal storm looks increasing likely early next week. Forecast models have come into much better agreement on the evolution of the mid and upper level atmospheric pattern across the Continental United States from late this week into this weekend. After a weekend rain event and weak disturbance, two additional disturbances in the mid levels of the atmosphere will move eastward from the West Coast. The first will settle into the Southeast States, while the second will be dropping southeastward from the Northern Plains into the Mississippi Valley. The two disturbances will interact, and possibly phase, early next week — and the end result will be a strengthening Nor’Easter on Tuesday.

The questions, now, become more related to specifics and the sensible weather that these features will bring. The strengthening coastal storm is likely to feature tremendous amounts of moisture and impressive dynamics aloft, but the exact track and intensity of the storm system will obviously significant impact what we see in our area. At this time, the potential is heightened for a multi-hazard Nor’Easter to impact our area from Tuesday into Wednesday, but our confidence in the areas impacted highest and the hazardous weather that our entire area experiences is low.

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