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

Miguel Pierre

Wednesday Briefing: Wintry threats begin in the Northeast this weekend

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Good morning! Tranquil weather has taken over in the Northeast states today, as high pressure takes control. With it has come the cold – temperatures will only reach the lower to middle 30s this afternoon in many spots. Some passing clouds will be the only story today as a weak disturbance passes through.

Unsettled weather is expected to return later tonight and Thursday as a broad upper-level trough moves into the Northeast. A warm front associated with this trough will be lifting northward late tonight and tomorrow morning, bringing increased cloudiness and some showers. A stronger cold front will be approaching from the west on Thursday – with mostly cloudy skies and light precipitation possible.

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John Homenuk

Tuesday Briefing: Snow exits, wintry and colder pattern awaits

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Every so often, we come across a storm that is quite humbling for meteorologists – one that defies most of our common practices and goes against the grain of what we are expecting. Last nights storm system was exactly that, as we expected the storm to pass mostly without fanfare. Just yesterday, regional observations and short term model guidance suggested the system would pass fairly harmlessly seaward, with light snow along the coast and Long Island with light accumulations on the East End.

As you may have already heard, much more than light accumulations occurred, with parts of Eastern Long Island reporting 6-9″ of new snowfall — a significant, warning criteria winter weather event. While these numbers were relegated to the Eastern part of Long Island, their occurrence was significant in its own right, as our forecasters were not anticipating numbers anywhere close to those to occur. As it turns out, forecast model guidance did a very poor job in resolving mesoscale features of the storm system, which allowed banding to pivot further westward and develop last night with moderate snowfall on Long Island. Another learning experience for all involved, in a profession that requires near constant learning to stay ahead of the curve – which we intend to do.

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Steven Copertino

Close Call Tonight, Another Snow Threat Possible Later This Week

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Good Evening!

Today started off with a mix of sun and clouds over much of the Northeast, but quickly turned mostly cloudy as a broad mid level disturbance began to move in from the west. Despite the cloudy conditions, today has been above-normal for this time of year, but still reasonably chilly. Highs were mainly in the upper 30’s to middle 40’s region-wide, as a stale mid level airmass worked into the Northeast. As we move into the late evening and overnight hours, the broad mid level disturbance centered over the Ohio Valley will continue to gradually move eastward. As it does so, it will bring very meager amounts of moisture from the south over portions of the Mid Atlantic and Northeast. If you take a look at the raw radar reflectivity over the Northeast, you may think that most of the region would be under light to moderate rain, however the moisture in place is not deep enough to overcome all of the dry air which is causing most of this precipitation to dissipate before it even reaches the ground. This is the same system that we talked about last week, and since that time the more conservative scenario has indeed played out, with the trough axis remaining too broad and disorganized to tap the impressive tropical moisture feed off of the East Coast. Regardless, an impressive upper level jet streak over the Northeast in excess of 170 mph will aid in the development of more mid level moisture later tonight that should be able to moisten the atmosphere enough so that we see some light to moderate rain along portions of MD/DE/NJ/CT/LI.

Temperatures will likely remain too mild for any pure snow to fall before midnight, however a very light mix of rain/snow may be possible over the farther NW locations of New Jersey and Connecticut. As we move past midnight and into the overnight hours, colder temperatures in the mid to lower levels of the atmosphere will begin to filter into the region, and this is when the best potential for some light snow will exist for the area. However, the vast majority of the precipitation will be centered well-offshore and thus precip rates will be very light. Given the light precip rates, mild temperatures, and meager overall moisture, no significant accumulations are expected for the immediate New York Metro area. Some locations over eastern Long Island and portions of New England will have a better shot at some light snow, but trends with this system will have to be monitored overnight.

This evenings latest RTMA 2m temperatures, surface observations, and regional radar mosaic. Note that despite all of the rain showing up, only stations south of the Mason-Dixon line are actually reporting any rain. This is due to dry air in the mid levels of the atmosphere.

This evenings latest RTMA 2m temperatures, surface observations, and regional radar mosaic. Note that despite all of the rain showing up, only stations south of the Mason-Dixon line are actually reporting any rain. This is due to dry air in the mid levels of the atmosphere.

Tuesday Through Thursday

Tomorrow looks to be an interesting day across portions of the Northeast as the mid to upper level trough associated with this weak coastal system begins to swing eastward and over the region. Some remaining light snow will likely be over portions of Long Island and eastern New England by the morning commute tomorrow, but a more interesting situation will be taking place over PA. As the bulk of the upper level energy moves over upstate NY and PA, lower to mid level forcing will become very strong and we should see at least one band of intense snow squalls develop over central PA. This band will be aided by very steep mid level lapse rates (change of temperature with height) which should allow any squalls to be quite heavy in nature around 8-10 am. As this band head eastward over Pennsylvania, some locations may see brief whiteout conditions with gusty winds and very heavy snow rates capable of dropping a quick 1-3″ locally. As we head into the early afternoon hours, this area of convective snows should be located over far eastern PA and perhaps over portions of Western NJ. This will all depend on how long the mid level energy is able to support this area of snow, but the general brief burst of heavy snow will be possible. Things look to calm down later in the afternoon as the temperature differential begins to even out, so expect any remaining snows to gradually dissipate just to the east or over the NYC metro area. Please use caution if driving through these heavy bands tomorrow, as visibility could drop to around-zero within a few minutes or so!

Evolution of the weak coastal storm as well as the convective snows tomorrow on the latest RPM model (courtesy of WSI)

Evolution of the weak coastal storm as well as the convective snows tomorrow on the latest RPM model (courtesy of WSI)

Wednesday looks to be a generally dry day across much of the Northeast as a weak area of high pressure looks to setup over the Mid Atlantic states. Wednesday looks to be much colder than the past few days as a brief shot of Canadian air makes its way into the Northeast. There may be some high clouds during the afternoon, but high temperatures look to get into the lower to middle 30’s. Later in the evening a weak area of energy will be moving well to the north of the area, with a chance at some snow showers possible for upstate New York and portions of New England. This weak system will help to bring in some warmer air aloft along a frontal boundary, but lows look to stay in the lower to middle 20’s due to radiational cooling.

Thursday is going to likely be a decent warmup from the previous day as stout southwesterly flow works in during the morning hours. This will work to greatly increase the amount of mid level moisture available, which should create a rather cloudy day overall. Some weak mid level energy associated with the Polar jet will also work into the Northeast during the day, which should work to enhance cloudiness and potentially a rain shower or two ahead of a frontal boundary that will be located over the Ohio Valley by Thursday afternoon. This frontal boundary will be the main focus for Thursday night into Friday, as the temperature differential along the front will support at least some moderate precipitation to breakout as it heads east and into the Northeast by Thursday evening. This afternoons model guidance is not in good agreement with regards to just how strong/how much precip this frontal boundary will have, but any light precipitation should begin to work its way into portions of Pennsylvania by late Thursday early Friday.

This afternoons European model showing light to moderate mix precipitation breaking out over portions of the Mid Atlantic and Northeast on Thursday night.

This afternoons European model showing light to moderate mix precipitation breaking out over portions of the Mid Atlantic and Northeast on Thursday night.

Some Snow Possible Into Friday Morning 

The threat for light snow will continue into the morning commute on Friday as the frontal boundary will likely be located right over the I-95 corridor. A strong upper level jet streak will be accompanying this system, so it would not be all that unlikely to see the models become more bullish with the amount of precipitation that develops over the area Thursday and Friday. At this time, this does not appear to be an all-snow event, but rather a mix of rain and snow to start, with light to moderate snow until the front clears. Accumulations looks generally light at this time, but this could change in either direction over the next couple of days, so make sure to check back for further updates!

Much colder and drier air looks to blast into the Northeast Friday afternoon and evening as the front begins to move offshore. Strong zonal flow looks to dominate the country for the majority of the weekend, but we may have to keep an eye on yet another progressive system moving across the country late Sunday and into Monday for the potential for some additional light snow.

This afternoons European Ensembles showing a rather cool, but progressive pattern taking shape over North America with a strong tropospheric vortex centered over Canada.

This afternoons European Ensembles showing a rather cool, but progressive pattern taking shape over North America with a strong tropospheric vortex centered over Canada.

Have a great evening!

Steve Copertino