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Sunday Briefing: Warmer east, snow in Plains, changes continue

Good afternoon, everyone! Much-awaited warm air has finally moved into the Eastern United States, on the heels of a prolonged period of cold. Temperatures today are running well above normal across a widespread area. Meanwhile, a deep trough and associated disturbance moving through the Rockies will eject northward into the Plains States later tonight into Monday, leading to the potential for a significant snowstorm in the Northern Plains.

The National Weather Service in Minneapolis, MN is forecasting a significant snowfall – but the gradient in snowfall totals is expected to be quite sharp. Snowfall totals could be very high underneath areas where impressive banding occurs, but could be much lower outside of those heavy snow bands. A very tough forecast! We explain a bit in our video below. Meanwhile, warm air will surge into the Eastern United States on Monday ahead of the system.

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Light to Moderate Snow Likely Tuesday Into Wednesday

Good evening! 

Most of the Northeast saw another below-average day as the Arctic high pressure system that has been dominating our weather over the past few days has finally begun to head off to the east over portions of southern Canada. As this high pressure system retreated to the east, we saw wind direction flip to a more easterly/northeasterly, with winds in the mid levels becoming more southwesterly ahead of a large disturbance moving south over the Great Lakes region. These southwesterly winds have aided in providing a slightly warmer airmass aloft, with some weak moisture also working into the low to middle levels of the atmosphere. This allowed the development of some mid to upper level clouds over the Mid Atlantic and Northeast during the afternoon hours, with even some scattered flurries being reported within in a weak band of moisture over portions of Pennsylvania. The combination of slightly warmer mid levels, partly cloudy conditions, and easterly low level flow made for slightly warmer highs when comparing them to the past two days. The immediate NYC metro area saw readings in the upper 20’s to lower 30’s, with locations to the north and wets seeing temperatures in the lower to middle 20’s, which is still around five or so degrees below normal. Generally dry and calm conditions are expected for the rest of the evening and into the overnight hours, with a slight chance of some widely scattered flurries. Temperatures will likely fall back into the lower to middle 20’s across the immediate NYC metro area, with teens expected to the north and west.

This evenings latest look at the regional radar mosaic, surface observations, and RTMA 2m Temperatures, showing a rather chilly evening with a disturbance approach from the west

This evenings latest look at the regional radar mosaic, surface observations, and RTMA 2m Temperatures, showing a rather chilly evening with a disturbance approach from the west

Light-Moderate Snow Event Likely Tuesday Into Wednesday 

This afternoons model guidance has come into slightly better agreement regarding a large closed upper level low centered over the Great Lakes region this evening. This upper level low has been meandering in about the same position for the past 36 hours or so, but this will change tomorrow afternoon as an impressive Pacific disturbance crashes into the West coast. This disturbance will act as a “kicker” for the upper level low in the Great Lakes, and cause it to elongate while becoming positively tilted. As it does so, a large upper level jet will extend from the Southeast Unites States and into the Northeast.  Some weak moisture will be involved in this initial setup, allowing for snow to break out just ahead of a frontal system as the upper level jet provides some adequate lift along the front. This frontal system will be located over the eastern third of the country by tomorrow afternoon, with snow likely forming over much of the Mid Atlantic and Northeast during the late morning and early afternoon hours. Some light snow may work its way into the NYC metro area later in the afternoon, but there may be some rain mixed in closer to the coast as surface temperatures hover at or above freezing.

Simulated Radar showing a potential evolution of the snow event on Tuesday/Wednesday

Simulated Radar showing a potential evolution of the snow event on Tuesday/Wednesday

A weak surface front associated with some more robust moisture from the Atlantic will begin to develop off the Mid Atlantic coast during the late afternoon hours and into the evening on Tuesday. This afternoons models have shown more of the moisture becoming super-imposed with the upper level jet streak aloft, which allows a very weak coastal low to develop off of the Delmarva peninsula by 8-10pm tomorrow night. Depending on the track of this low and the associated moisture plume, we could see more moderate snow develop over eastern PA, MD, VA, SNY, eastern NJ and Connecticut during the overnight hours. Again, precip type may be more wet than white closer to the coast, but we could see a gradual shift to snow during the morning commute for locations to the south and east of NYC. This weak low pressure system will be moving at pretty good clip, so as of now we expect that snow will peak in intensity over the NYC area right around 7-9am before very gradually tapering off from west to east during the afternoon. At this time, we expect generally light accumulations to the south of Northern NJ, with light to moderate accumulations further off to the north and east.

There are some uncertainties that remain with this system, as surface temperatures during the height of the storm may be a little too warm for accumulating snow, and this would cause totals to decrease a bit, especially to the south. Another possibility is that we see the coastal low develop a little quicker than originally thought, which would not only brings in more moisture, but would drag more cold air in from the north. Such a solution would yield higher snow amounts area-wide, but at this time we feel that solution is less likely to happen. However, we will be closely monitoring this system over the next day or so, so make sure to check back for future updates!

Expected Storm Total Snowfall from Tuesday Night/ Wednesday Afternoon

Expected Storm Total Snowfall from Tuesday Night/ Wednesday Afternoon

Have a great night!

 

Steven Copertino 

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Anomalous cold’s swan song, moderation lies ahead

Welcome to Five Minute Drill, our new segment where we discuss the weather without bias or favoritism on a local, regional, and national scale as the weather suggests. In the week ahead, we’re discussing the movement of bitter cold away from the Northeast states, but the prevalence of a few weak atmospheric disturbances that may lead to wintry precipitation on Monday evening. We touch on where we’ve been over the past few days, why things are changing, and briefly discuss a Northern Plains winter storm later in the week.

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Brutal Cold Grips Northeast, Changes Are Coming Next Week

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

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

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

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