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Steven Copertino

Light Wintry Mix Likely Thursday Night, Coastal Storm Possible Sunday into Monday

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Good evening! 

Today has been a rather cold and typical winter day across the entire Northeast after the system that impacted the region on Monday left some fresh snow cover for eastern locations. A large area of energy associated with the tropospheric polar vortex has been meandering just to the north of the Northeast, which has allowed for some light snow flurries to break out earlier this afternoon and into this evening. These flurries were mainly confined to the northern sections of upstate New York and portions of northern New England as moisture and forcing was rather meager with this system. Regardless, some limited moisture in the middle to upper levels of the atmosphere allowed for some spotty clouds to break out during the afternoon hours. Despite the peaks of sun during the day, high temperatures were pretty cold across the entire Northeast, with most of the New York metro area seeing readings stay in the upper 20’s to lower 30’s. Locations to the north and west were a little colder, with highs in the lower to middle 20’s. Calm and cold conditions will last through the evening and into the overnight hours tonight as an area of high pressure located to our south exits off the Mid Atlantic coast. As this area of high pressure moves to the south and east, surface winds winds will begin to shift to a more southerly component as mid level winds turn to the southwest. This mid to low level flow will allow slightly warmer mid level temperatures to work in from the south, allowing surface low temperatures to only drop into lower to middle 20’s for the vast majority of the region. The increased southwesterly flow will also allow for more mid to high level clouds to take over as the night progresses.

This evenings latest 2m RTMA temperatures, surface observations, and regional radar mosaic. Note the weak area of light snow and flurries over New England associated with some disorganized energy over southern Canada.

This evenings latest 2m RTMA temperatures, surface observations, and regional radar mosaic. Note the weak area of light snow and flurries over New England associated with some disorganized energy over southern Canada.

Thursday Through Friday

Thursday will likely start off cold, but rather cloudy across the majority of the Northeast as stout southerly flow continues to pump in and over the region. The majority of the day should be generally quiet as we await the passage of a weak cold front that will be moving in from west to east over the area. Ahead of this front temperatures will likely rise above freezing by the mid afternoon hours, with highs likely getting into the lower to middle 40’s across much of the Northeast. Some light rain showers will be possible over southern portions of New Jersey and Pennsylvania tomorrow afternoon as low level moisture continues to increase. The best chance for precipitation will come towards the late evening hours as all levels of the atmosphere become saturated as the front briefly interacts with some residual moisture off of the Mid Atlantic coast. Temperatures will be above-freezing to start off, but this afternoons model guidance has become a little more bullish in showing sub-freezing temperatures arriving just a little after the mid-way point in the precip. Areas from west to east should see a rather gradual shift from rain to snow, with some light accumulation possible. Trace amounts are expected, but 1-2″ cannot be ruled out in some of the higher terrain. The main threat with this front will be any untreated roadways quickly freezing over as temperatures quickly drop behind the front.

The cold front and any remaining precipitation should be moving quickly off of the coast on Friday morning, leaving much colder temperatures and gusty winds in its wake. Fresh Polar air will be blasting through the East during the morning and early afternoon hours, easily making Friday the coldest day for at least a week. The combination of the fresh Polar airmass, dry mid levels, and gusty winds will leave highs in the lower to middle 20’s with upper teens likely off the north and west. There may be some isolated strands of snow showers during the afternoon hours on Friday due to the upper level trough being directly overhead. These snow showers may be capable of temporarily reducing visibility, but any accumulations should be insignificant. Friday night will be a very cold night as an area of high pressure builds just to our south overnight, allowing for near-perfect conditions for radiational cooling to take place. Expect for lows to drop down in the lower to middle teens across the NYC metro area, with single-digits likely off to the north and west.

This afternoons high resolution NAM model showing the passage of a cold front and the impressive Polar airmass looming behind it

This afternoons high resolution NAM model showing the passage of a cold front and the impressive Polar airmass looming behind it

A Messy Super Bowl Sunday Possible Across the East 

Surface high pressure will continue to dominate the weather over the east coast on Saturday with clear skies and cold temperatures. Highs will likely be a couple degrees warmer than Friday, but still in the middle 20’s to lower 30’s across the entire Northeast. As we head deeper into the day on Saturday, the bigger story becomes focused on energy diving into the Plains states as our high pressure begins to retreat to the east. As the high leaves us, southerly flow will begin to overspread the region as a low pressure begins to form over the Ozarks. Temperatures will begin to rise steadily on Sunday as the low pressure system approaches from the southwest, leaving the majority of the Northeast above freezing. At this time, it appears likely that precip will start later in the afternoon on Sunday, becoming rather steady by the evening hours. As of right now, this setup does not look to be supportive of widespread snow at all due to the lack of a high pressure to the north to provide some kind of cold. Additionally, this system will be moving very quickly as the mid level energy remains broad and disorganized. For now we expect mainly rain on Sunday, with the possibility of a changeover towards the end of the evening. We will continue to monitor the progress of this system carefully over the next couple of days and provide updates when necessary!

This afternoons European model showing a rainy Sunday evening across the NYC metro area, with some snow off to the far NW regions

This afternoons European model showing a rainy Sunday evening across the NYC metro area, with some snow off to the far NW regions

Have a great night! 

Steve Copertino

Steven Copertino

Major Air Mass Change This Week, First Flakes Possible!

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Good Evening! 

Well we hope that all of you have been enjoying the relatively warm temperatures over the past few weeks, because it looks like things are about to change in a big way over the next few days across the entire east. Today was the last in the series of warmer days across the Northeast as an area of low pressure moved eastward across New York state. Southwesterly flow at the surface allowed warmer mid level temperatures to funnel in, as well as some leftover moisture from yesterdays severe weather outbreak over the Ohio Valley. This moisture was responsible for producing some clouds and showers over much of the Northeast, but much of the rain was on the light to moderate side of things. Despite these clouds and showers, temperatures were able to head into the middle to upper 60’s, with some locations in southern New Jersey actually reaching the 70 degree mark once again! The area of low pressure moving to the north of the New York Metro area has a rather strong cold front associated with it, and is currently moving over Pennsylvania and into portions of New Jersey. Winds have begun to shift to a more westerly/northwesterly component, which will mark the beginning of cooler temperatures and lower dew points leaking into the region.

Any leftover showers will quickly head east and dissipate over the next few hours, and this should give way to more clear conditions as we head into the night. An increasing pressure gradient from an area of high pressure building to our west will begin to create some gustier winds from the north, which should range in the 15-20 mph area. Overall, lows this evening will likely drop into the upper 30’s and lower 40’s across much of the area, with some middle 30’s possible in the interior locations of NJ, PA, and NY.

RTMA temperature analysis, surface observations, and regional radar mosaic showing the progression of relatively strong cold front moving through the area this evening (Simuawips)

RTMA temperature analysis, surface observations, and regional radar mosaic showing the progression of relatively strong cold front moving through the area this evening (Simuawips)

Tuesday Into Wednesday 

Tuesday morning should start off quite chilly, with some gusty winds still sticking around at least through the morning commute. The area of high pressure moving eastward will likley keep the majority of the day quite clear and calm, with highs generally in the lower 50’s across much of the New York metro area-though lower temperatures will likely be found to the north and west. The main story for tomorrow will be a weak wave of low pressure moving along the leftover cold front that will be located over portions of the southern Mid Atlantic states by tomorrow afternoon. As this system quickly slides along the front tomorrow, it should bring an area of light to moderate rain over portions of the Mid Atlantic states like Maryland, Delaware and Virginia by 5-7 pm. The northern fringes of this weak system will likely also impact the New York Metro area as well, but this setup will be especially interesting to watch for those located in NW New Jersey, NE Pennsylvania, southern New York, as well as the higher elevations of Connecticut as the wave of low pressure begins to head off the coast. As the system moves off the Delmarva late Tuesday and into the very early morning hours of Wednesday, the system will begin to strengthen just a bit, and this should help to cause a more uniform wind pattern at the surface, which could be capable of tapping the new/colder Canadian air just to the north.

This evenings NAM model, a colder solution, showing snow mixing in on the NW fringes of the precipitation tomorrow evening

This evenings NAM model, a colder solution, showing snow mixing in on the NW fringes of the precipitation tomorrow evening

Some of the higher resolution models have just enough cold air filtering in at the lower levels of the atmosphere, that we will indeed have to watch for a mix to possible changeover to snow across portions of Northeastern Pennsylvania, Northwestern New Jersey, southern New York, and Connecticut around midnight. While the thermal profiles of today’s models do show a good chance at a mix of wet snow/rain, there also could be some graupel mixed in as well, making roads a bit slick for any persons traveling. Precipitation should be light enough in these locations that any wet snow that does fall will likely melt on impact with the ground, but if the cooler solutions of the other models verify, there could be some locations well to the north and west of the city that wake up with a trace of wet snow in the grass that melts away by the morning commute. Further south and east, this event looks to be mainly a “33 and rain” type of event, where there just isn’t enough low level cold to support anything but light rain with little fanfare. Lows tomorrow night will be rather cold, with temperatures ranging from the lower to upper 30’s-with warmer temperatures located near the coast.

This system will quickly move away by Wednesday morning, leaving some high clouds and light winds in its wake. A very weak area of high pressure will try to build over portions of Pennsylvania during the day, which should keep winds light, and skies clear for the rest of the day. Temperatures will be on the cool side for highs, with most of the Northeast likely staying in the upper 40’s to lower 50’s. Lows will be quite cool as well, as conditions set up for radiational  cooling to take place, so expect temperatures to drop into the lower to middle 30’s-with warmer lows closer to the coast.

This afternoons GFS model showing a very impressive cold shot blasting through the Northeast on Friday and into Saturday morning

This afternoons GFS model showing a very impressive cold shot blasting through the Northeast on Friday and into Saturday morning

Thursday and Beyond 

By Thursday, a strong upper level trough will be moving east over Canada, carrying very cold air with it from the northern regions of Canada. This cold and dense Canadian air will begin to sink south into the Northeast in the form of an Arctic front. This front should quickly move through the region late Thursday, bringing lows in the 20’s and 30’s, with a shot at some snow showers across the entire Northeast. This cold shot should last into Friday evening, where lows may drop well into the 20’s. Temperatures will moderate a bit by Sunday, but should stay somewhat below-normal.

12z ECMWF overnight lows Friday PM/Saturday AM

12z ECMWF overnight lows Friday PM/Saturday AM

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Have a great night!

Steve Copertino