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Snow passes to the south Sunday, cold and calm next week

December 7, 2018/1 Comment/by Steven Copertino

Good afternoon!

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Things have once again turned quite calm over much of the Northeast today after a weak upper level disturbance moved through last night and produced some light snow well to the north and west of the New York City metro. Strong northwesterly flow behind this system has cleared out remaining moisture in the atmosphere and has replaced it with cold, dry Arctic air. Despite the cold mid level temperatures, clear skies have allowed for temperatures to rise into the middle to upper 30’s over much of the Northeast, with lower 40’s showing up in the city and portions of southern New Jersey.

The remainder of this afternoon will feature much of the same, with mostly sunny skies and light winds. There may be a chance at some more isolated snow showers if you’re traveling to eastern Pennsylvania and southern New York, but these should be quite tame. As we head into the evening hours and overnight, yet another Arctic shortwave will be passing to our north, which will provide a fresh injection of very dry and very cold air. Additionally, an area of high pressure will be edging it’s way into the Ohio Valley and Northeast. Given the dry air, fresh cold mid to upper level, and light winds, we fully expect radiational cooling conditions to be near-ideal tonight. This should allow overnight lows to drop well into the 20’s and teens over much of the Northeast, with even some single-digit readings possible. If you’re heading out tonight, definitely bring a heavy coast as it will feel more like January than December!

This afternoon’s ECMWF model showing surface temperatures 12-20 degrees below normal Saturday morning (AccuWx Pro)

Snowstorm passes well to the south later this weekend

Weekend Weather Rating | 8/10

As we talked about back on Wednesday and earlier this week, the storm we have been watching for the better part of the last ten days now appears to slide well to the south of the Northeast during the day on Sunday and into Monday. The models have trended even stronger with the confluence over eastern Canada over the past couple of cycles, which has caused an even greater shift to the south.

It now appears that places like Washington DC are unlikely to see any meaningful precipitation from this storm, while locations in southern Virginia and North Carolina may face a very impactful winter storm, with substantial snowfall and dangerous ice accretion. As of this update, the National Weather Service is forecasting snowfall totals of up to 12-18″, with locations in the mountains of NC likely to see over two feet of snow by Monday. Those who live in this region should be prepared to have normal operations and routines severely disrupted at least through Monday night-if not longer.

Back up north in our neck of the woods, Sunday should remain cold and clear, with a chance of increasing clouds towards sunset. Both Saturday and Sunday should feature highs in the middle to upper 30’s, with lows well into the 20’s. Locations well to the north and west should even be able to dip back down into the teens Saturday night.

Loop of this afternoons 3km NAM model showing the significant winter storm passing well to the south of the region this weekend.

Loop of this afternoons 3km NAM model showing the significant storm passing well to the south of the region this weekend. Heavy snow will be likely for portions of the Mid-Atlantic and Southeast

Quiet conditions and below normal temps persist into next weekend

After this weekend’s storm exits off the Southeast coast Monday night, we should see very quiet and cool conditions for the majority of the next week. Temperatures will likely remain 5-15 degrees below normal along the east through Wednesday, with lows sticking well-below freezing for the Northeast.

However, by the time we get to around Wednesday/Thursday, a large and energetic upper level disturbance will be moving into the Rocky Mountains. This upper level disturbance could be our next shot at some precipitation by the time we get to next weekend. At this time the models are showing an area of low pressure developing over the Midwest, which would bring a significant amount of moisture and warmer air up through the southern states and eventually into the Northeast. This would likely result in an increased chance for rain for the NYC area next weekend, but we’ll certainly be keeping an eye on this potential system during the course of next week.

500mb height anomalies from this afternoons ECMWF model showing an unusually deep closed upper level low over the south, with an area of ridging over the East.

Have a great weekend!

Steven Copertino

Unseasonably cold and dry conditions prevail, update on the snow threat this weekend

December 5, 2018/1 Comment/by Steven Copertino

Good evening!

Today was quite the interesting day across the tri-state area as the area of low pressure that we have been talking about for the past few days developed off of the New Jersey coast early this morning. This area of low pressure was spawned by a mid-level disturbance that was able to organize just at the last second as it approached the Mid-Atlantic coast. As both the surface low and the mid-level system both organized this morning, a narrow area of snow broke out over portions of southern New Jersey. This area of snow quickly grew from east to west during the early afternoon hours, extending back into eastern Pennsylvania at its peak. The small, but impressive band of snow virtually stalled over Atlantic county and produced snowfall rates of up to 1.5″ an hour. At the time of this article the highest snowfall totals from southern New Jersey are in the 4-6″ range, but it would not be surprising at all to see a few isolated reports come in higher. Elsewhere, there was a rather steep gradient with accumulations mainly in the 1-3″ range to the north and south of the main axis of heavy snow.

This area of low pressure and the associated surface trough are now beginning to pull to the east, causing any residual snow along the coast to wind down. We should see this low continue off the coast this evening, with calm and decreasingly cloudy conditions through the overnight hours for the vast majority of the Northeast. Usually a storm pulling away from the coast would produce near-ideal conditions for radionatal cooling all the way to the coast, but there appears to be a chance that stubborn mid/upper level clouds will hang on just enough, at least for the immediate New York City area. Accordingly, lows will likely stay in the middle to upper 20’s tonight, with middle to lower 20’s likely for locations to the north and west.

Latest high resolution water vapor imagery, surface temperatures, surface winds, and regional radar showing the area of low pressure responsible for the NJ snow beginning to head east

Unseasonably cold and dry conditions to continue through the weekend

Thursday morning should start off like every other morning so far this week, with mostly sunny conditions and cold temperatures in the middle to upper 20’s for the AM commute. Clear and cold conditions should continue through the afternoon hours before a broad area of upper level energy approaches the region from the northwest. While this system should remain relatively dry given the fact the associated airmass is continental arctic, there may be just enough lift to spark the development of light to moderate snow showers towards the evening hours tomorrow night. While the bulk of this activity should stay over portions of New York state and Pennsylvania, it would not be all that surprising to see some narrow bands extend all the way back into portions of New Jersey and possibly even NYC. Otherwise, increasing cloudiness will put a lid on low temperatures tomorrow night, with temperatures likely staying in the middle to upper 20’s for the majority of the tri-state area.

By the time we get to Friday morning, yet another shot of cold/dry air will quickly move through the Northeast, likely clearing out any residual clouds from the previous night. Temperatures should stay in the upper 20’s to lower 30’s during the day on Friday, but occasionally gusty winds may make conditions feel a good 10-15 degrees cooler. Winds will likely calm down during the afternoon hours on Friday as an area of high pressure begins to edge into the East. With high pressure in control and all levels of the atmosphere very dry, we should see excellent conditions for radiational cooling to occur. Lows on Friday night will be quite cold, with readings dropping well into the 20’s, with teens likely for portions of NW New Jersey and southern New York. All in all, temperatures over the next few days will range anywhere from 5-15 degrees below normal across the entire Northeast, which is much more like January as opposed to early December.

Loop of the 18z 3km NAM showing unseasonably cold conditions persisting throughout the next few days.

Late weekend storm likely to stay south of the NYC area

Over the past five days or so we have been watching numerous pieces of energy in the atmosphere located over the Arctic, the Pacific, and Alaska which will likely interact with one another by the time we get to Saturday afternoon over the Southern Plains. As these pieces interact, a large area of heavy rain and snow will gradually develop and begin to produce a swath of significant snow that could extend from Oklahoma to the Mid-Atlantic coast when all is said and done. While we do know that these various pieces for the storm will likely come together, what we don’t have nailed down yet is exactly how and when they will do so.

As of right now, the most likely scenario is that the main upper level system over Texas will begin to strengthen during the day on Saturday, while another piece of energy from the Arctic dives into the Northern Plains, causing the main storm to speed up. Additionally, another area of energy will likely be located over Southeastern Canada, which will be injecting very dry air over portions of the Mid-Atlantic and Northeast. This dry air will essentially act as a wall during the day on Sunday as the main surface low moves through the Southeastern US and tries to make some northward progress. At this point, the forecast will be dependent on just how strong the disturbance over Southeast Canada is at the time. If the system is weaker, there is a chance that meaningful precipitation is able to make its way north and impact DC to Philadelphia. However, the model runs from this afternoon showed increased dry air and “confluence”, forcing the main impacts down into portions of KY, WV, VA, and NC.

While there is still time left before Saturday, we feel that there will likely not be significant enough changes with the predicted upper air pattern to cause any major changes with this forecast for the NYC area.

In summary, it appears increasingly likely that the immediate NYC area will remain well to the north of any potential impacts, with only increasing clouds and cold temperatures during the day on Sunday.

Current states at highest risk for significant winter weather impacts: KY, NC, SC, VA, WV

Current states at risk for some impactful winter weather, with high uncertainty: MD, DE, PA, NJ

Current states with lowest risk for impactful winter weather: NH, VT, ME, MA, CT, NY, RI

51-member ensemble from the European model showing the probability of 3″ or greater of snow. At this time significant impacts from this system are quite low.

Make sure to check back in during the day tomorrow for more updates on this system!

Steve Copertino

Brutal Cold Grips Northeast, Changes Are Coming Next Week

January 5, 2018/by Steven Copertino

Good Evening!

Yesterday we saw an extremely impressive Nor’easter impact much of the Northeast with heavy snow, highs winds, and extremely dangerous coastal flooding for the majority of the day. Snow totals varied quite a bit from west to east, but the highest totals for the region occurred from portions of eastern New Jersey, Long Island, Connecticut, and into New England, where amounts in the 10-20″ range were common. Totals over central and western New Jersey were lower, with numbers generally in the T-8″ range, as was common in PA and SNY. Overall, this was a very impressive and possibly historic storm due to its ferocity and sheer amount of power. Conditions came together in the atmosphere in just the right way to let this storm go from a rather weak 1010mb system off of Florida, to a monster 951mb blizzard off of the Delmarva coast. This extreme pressure drop contributed to the very strong winds we saw over the entire east coast and continue to see today and this evening.

As the storm pulled away last night, a deep Arctic airmass dove down from northern Canada and has caused temperatures to once again drop into the lower to middle teens across much of the tri-state area. Much colder reading were seen over portions of New England, with some locations staying 10-12 degrees below zero! A strong pressure gradient will continue to exist between the Arctic area of high pressure over southern Canada and our blizzard that continues to move over portions of southeast Canada. Winds tonight will continue to gust into the 15-30 mph range and when coupled with lows in the only a few degrees above zero in the immediate NYC metro area, wind chills will become very dangerous. Wind chills will likely drop into the -15 to -25 range for NYC and the immediate north/west suburbs and -20 to -30 for locations in Southern New York and Northeastern PA. These kinds of readings can cause frostbite within 20-30 minutes of exposure, so please use caution if you must go outside late tonight and into the overnight hours and make sure to layer-up!

Animation showing the progression of tonight’s expected wind chills from the HRRR model. Readings will be at their lowest around 6-8am Saturday

This Weekend

Saturday looks to be yet another brutally cold and well-below normal day across the Northeast as Arctic high pressure builds into the region. Conditions should start off very cold and cool as mid-low level dry air takes over and limits any potential for any clouds besides upper-level cirrus. Winds may attempt to subside a bit during the day, but will likely still gust into the 20’s, which will still bring brutal wind chills in the -20 to -10 range during the early morning and afternoon hours. Highs across the NYC metro area will likely struggle to get out of the single-digits, with lower to middle teens expected to the south over portions of Pennsylvania and New Jersey. Frigid and dry conditions will last into the evening and overnight hours as we see lows drop off once again in the 5 to -10 range. Winds will continue to diminish, but wind chills will still be able to stay in the -10 to -20 range pretty much area-wide. Again, take the necessary precautions if you have to head outside tonight and Saturday night.

Sunday will be another cold and dry day across the Northeast as the Arctic high pressure system is directly overhead. Mid level dry air should ensure that conditions stay mostly sunny, with only a few passing high clouds expected. Despite the Arctic high being overhead, mid level flow will begin to modify ahead of a developing system in the Plains. This should cause temperatures to not be as brutally cold, with highs in the upper teens to middle 20’s expected across the entire area. Lows will likely not fall all that much as the high pressure system begins to exit off the Mid Atlantic coast and the entire region sees return flow from the south.

Animation showing the last of the brutal cold moving through the Northeast tonight and Saturday

Major Changes Likely By Next Week

After one of the most impressive and longest cold-spells in recent memory for the Northeast, one would think that things would eventually have to break down. Last week I asked this same question, but now it seems like the brutal cold will indeed gradually fade to relatively warmer conditions across the east. After the Arctic high pressure system exits the country by Sunday night, the upper level flow will become more east to west based, which is a strong departure from the highly amplified pattern we have been accustomed to over the previous 10 days. This pattern should allow for multiple shots of warmer air from the south and west to overtake the Northeast, with highs in the 30’s and 40’s likely to make a return. As of right now, there does seem to be a chance that we could get temperatures into the upper 40’s and possibly lower 50’s, but this is around a week away and will likely need to be revisited next week. Regardless, while we may see slightly above-normal temperatures at times, we do have to keep in mind that this is still January and the potential for snow will always remain present. Would could see a rather active period with above normal precipitation through the middle of January as deep tropical moisture may occasionally try to nose its way into the country. We will be watching this potentially warmer and wet period closely over the next couple of days and will provide updates when they are available!

This afternoons ECMWF ensembles showing the potential for above-normal temperatures next week across the central and eastern US

Have a great weekend!

-Steve Copertino

Another Round of Records May Fall, Any Chance of Warmer Weather Soon?

December 29, 2017/by Steven Copertino

Good Afternoon!

We hope everyone out there has been bundled-up over the past couple of days as we continue to endure a record-breaking temperatures across much of the Northeast. Today was a little warmer than yesterday, but warmer in this sense is still relative. Temperatures were stuck in the upper teens to middle twenties across the entire New York Metro area, with some middle to lower teens further north and west of the city. The same stout northwesterly flow in the mid levels of the atmosphere are still prevalent across the entire northern tier of the country, which continues to pump dry, Continental polar air into the country. Mainly dry conditions can be expected for the rest of the afternoon and into the evening hours before a weak shortwave trough begins to move into the Ohio Valley later tonight. This system looks to be too weak and too far west to really bring any precipitation into the region, but we should see an increase in mid to upper level clouds during the overnight hours. These clouds will work to dampen the maximum amount of radiational cooling we can achieve, but lows tonight will still be downright frigid once again. Middle to lower teens are expected tonight for the immediate NYC area, with single digits likely just to the north and west.

This afternoon high resolution visible satellite imagery, regional radar mosaic, and surface observations showing yet another bitterly cold day across the entire Northeast.

Light Snow Possibly Saturday

The weak shortwave trough that we mentioned earlier will continue to move east overnight and into the early morning hours on Saturday, likely bringing some very light snow to portions of the Mid Atlantic states. This system will be seriously moisture-starved, but any snow that falls will be high-ratio snow. This means that even if you see around .1″ of liquid, you could still manage to see about 1.5″ of fluffy snow. Scattered light snow should begin to overspread portions of eastern PA and NJ by the early morning hours tomorrow, with more concentrated bands possible over MD/DE. Light snow should then move over the rest of the area by the late morning and afternoon hours as a secondary low begins to develop just off of the Mid Atlantic coast. Once this secondary low begins to mature, snow should be ending over much of NJ and points west, with trace to maybe an inch of snow possible. Our secondary low should have more of an impact further east over portions of Long Islands and Connecticut where it should act to rejuvenate snow over those areas and possibly add a boost to the intensity. Slightly higher accumulations may be possible in these areas, with 2-4″ possible before the low quickly races off to the east and precip shuts down by 8-10pm. Note: Due to the extensive dry air ahead of this system, we could see prolonged periods of virga over the area leading to the possibility of little to no snow at all in some places.

The rest of the night looks to be very cold, with scattered snow showers possible over much of the Northeast as another shot of Polar air moves into the region overnight. Lows will drop down into the middle to lower teens around the city, with single-digits likely to the north and west.

This afternoons RPM model showing a light area of snow overspreading the region on Saturday morning

Sunday will compete to be the coldest day of the year on the last day of the year as Polar high pressure builds into the Northeast during the morning hours. Highs during the day will be bitterly cold, with readings likely in the middle teens to right around 20. Strong northwesterly flow should keep enough dry air in the column to keep any clouds at a minimum. Dry and cold weather can be expected to last into the evening hours, just in time for New Years Eve. This should be one of the colder New Years Eve’s in recent memory, with the potential for quite a few records to fall across the Northeast. NYC may come very close to breaking a record low minimum temperature of around 9F. Readings across the entire area will be exceedingly cold, around the low teens to single digits area, with wind chills a good 5-10 degrees colder. We would seriously advise against being out for a prolonged period of time in this kind of cold, but if you are planning on it, make sure to wear multiple layers of clothing and cover up any exposed skin. Bare skin will be very susceptible to frost-bite during the evening hours!

National Weather Service forecasted lows on New Years Eve, with the circles representing possible records being tied or broken!

New Years Day & Beyond!

We look to start off 2018 with another frigid and potential record-breaking day as very strong northerly flow dumps the remaining Polar air right into the Northeast. Most locations near the City will likely not be able to reach the 20’s, with middle to upper teens likely as highs during the day. Locations even further to the north and west will also struggle to see highs come out of the single-digits, making Monday an excellent day to just stay inside and enjoy a nice warm beverage!

Will things improve and warm up later next week? The short answer is absolutely not. We could see temperatures briefly come back into the upper 20’s, but most of the Northeast may be stuck below-freezing for at least the next 10 days or so! To further complicate things, a coastal storm may past to the east of the region on Wednesday, which would bring down another extremely cold airmass from deep in Canada. At this time, this system appears to have a low chance of impacting the East, but we will be monitoring this system very closely since some of yesterdays guidance did show the potential for a rather high-impact storm if all the pieces come together at just the right time and place (thread the needle type of system)

This afternoons ECMWF model showing a reload of the cold weather with a shot of true Arctic air next week.

Have a great weekend and we’ll see you in 2018!

Steve Copertino

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