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Big Changes Next Week, Cold and Potentially Active Pattern Shaping Up

Good Afternoon! 

Welcome to December folks! Today was a relatively cool and calm day as another area of high pressure has edged its way into the Northeast after a cold front passed through the region last night and brought some light rain to most locations. This area of high pressure has ushered in some cooler temperatures aloft and at the surface, in addition to some drier air that allow temperatures today to drop to near-normal levels, with most of the Northeast staying in the middle to upper 40’s, with locations closer to the coast getting into the 50’s. Despite the near-normal temperatures, the air did have some bite to it this afternoon as winds gusted up to 20 mph in some locations, which certainly made conditions feel a little cooler than they actually were. Regardless, this was a rather beautiful start to December with mainly clear skies area-wide. With high pressure still in control as we head into the evening hours, conditions will be quite favorable for radiational cooling to take place across the entire northeast. There may be come high clouds from some weak remnant upper level energy passing by, but we expect temperatures to drop into the low 30’s and upper 20’s for the immediate New York suburbs, with middle to lower 20’s possible for locations to the north and west of the area.

A look at the RTMA this evening showing cooling and clear conditions over the entire Northeast. Lows tonight are expected to fall sharply into the 20's and 30's across much of the area (Courtesy of Simuawips)

A look at the RTMA this evening showing cooling and clear conditions over the entire Northeast. Lows tonight are expected to fall sharply into the 20’s and 30’s across much of the area (Courtesy of Simuawips)

This Weekend 

Saturday should start off quite clear and cool in the morning hours, as the area of high pressure begins to move up and out of the Northeast. As the high gradually shifts east during the day, surface winds should begin to respond and shift to a more southerly/southeasterly component. This should allow slightly warmer temperatures to move in tomorrow for the southern portions of New England and the Mid Atlantic states where highs in the upper 40’s to lower 50’s will be possible closer to the coast. Highs in the northern and western locations of the Northeast should stay in the low to middle 40’s as more stubborn cold air holds its ground. Tomorrow looks rather pleasant as the entire nation is stuck in this progressive west to east flow that has dominated the pattern of the past few weeks. A weak shortwave trough will be embedded in this fast west to east flow tomorrow, and should pass over the Northeast by the early afternoon hours. This shortwave trough will be highly sheared and moisture starved, so only some high clouds are expected from this system. Calm and clear conditions will extend into the evening and overnight hours as the aforementioned shortwave rockets off the east coast. With light winds, dry mid levels, and cool mid level temperatures, conditions will once again be supportive of efficient radiational cooling to take place. Expect lows to once again drop down into the low  20’s for locations well removed from the coast, with upper 20’s and lower 30’s as you get closer to the New York City metro area.

Sunday also looks to be another nice and quiet day across much of the Northeast. Previously, there was a chance at some light rain showers from a weak disturbance moving through Canada, but since Wednesday model guidance has been trending weaker and drier with that system, so at best this system may be able to increase clouds throughout the afternoon hours. With the zonal flow still in place and no real airmass change in site, we expect temperatures to remain generally right around average for this time of year, with highs in the lower to upper 40’s across much of the area. some locations closer to the coast may once again be able to nudge into the lower 50’s if sunnier conditions and offshore winds persist. High clouds may last into the evening and overnight hours on Sunday, but this should have relatively little impact on the overall sensible weather. Expect lows to drop into the low to middle 20’s north and west, with upper 20’s to low 30’s likely across the New York Metro area. Overall, this weekend looks to be a quiet one with seasonable temperatures, so if you’re planning to get the holiday decorations up, this weekend would be an excellent time to do so!

This afternoons ECMWF model showing the zonal flow pattern that the CONUS has been stuck in for a while now. The west to east flow does not allow for systems to slow down and strengthen, leading to relatively dry and quiet conditions across s the country

This afternoons ECMWF model showing the zonal flow pattern that the CONUS has been stuck in for a while now. The west to east flow does not allow for systems to slow down and strengthen, leading to relatively dry and quiet conditions across s the country

Big Changes In the Pattern Moving Up In Time

We are still on track for a substantial and total change in the overall synoptic pattern across the Northern Hemisphere starting as early as next Wednesday. By this time, a massive area of mid level ridging will balloon over the west coast and up into the Yukon territories of Canada. As this ridge goes up, we’ll also see another area of anomalous riding go up near Greenland. As these features build and establish themselves during the middle of next week, we should see the atmosphere respond in a rather big way. A large storm system should take shape in the central part of the country, and then move north into Canada. Large storm systems that cut up the central part of the country are usually tell-tale signs that change is coming to the pattern. As the low pressure area quickly heads up into Canada, Arctic air will rush down on the western side of the low thanks to the aforementioned area of ridging that will be established over the west coast. This blast of colder air will move quickly behind a strong cold front associated with the decaying low pressure that will move well into the northern portions of Canada by the end of next week. This cold front may have some significant precipitation associated with it as the mid level trough accompanying it is able to dive all the way down into the Gulf of Mexico.

This afternoons EPS showing the difference between the zonal flow we have been stuck in compared to the much more amplified pattern we're heading into

This afternoons EPS showing the difference between the zonal flow we have been stuck in compared to the much more amplified pattern we’re heading into

After the initial cold shot by the end of the week, we should begin to see a near-constant feed of Arctic air into the central and eastern portions of the country, with the possibility of numerous northern stream disturbances diving down from Canada. Since we should have an established block by this period, we may have to watch as these systems will have the chance to slow down, and strengthen close to the east coast. This is an idea that is supported by this afternoons latest model guidance and fits the pattern of years past as well. Regardless, we are going to be moving into a much more winter-like pattern by the end of next week, with the initial setup taking place by the middle of next week. This cold and potentially active pattern should last at least into the middle of December, with the potential for the pattern to reload and strengthen throughout the rest of the month. We will have more updates early next week on this pattern!

This afternoons GFS model showing the initial cutter that kicks off the pattern change and brings in much colder air into the CONUS with a potentially active storm track across the country over the next few weeks

This afternoons GFS model showing the initial cutter that kicks off the pattern change and brings in much colder air into the CONUS with a potentially active storm track across the country over the next few weeks

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Have a great night!

Steve Copertino 

 

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