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Steven Copertino

Warmer Weather On Borrowed Time, Cold and Potentially Active Pattern Shaping Up

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Good Evening & Happy Friday!

 

Today has been a rather cool but cloudy day across much of the Northeast with a couple of scattered showers over the immediate New York City area, but further north conditions are quite messy. An area of low pressure along a frontal wave is pushing through the Ohio Valley this afternoon, and producing a modest area of precipitation across portions of the Northeast.  As we talked about on Wednesday, this area of moisture surging northward from the Gulf of Mexico and into North will be met with the same strong area of high pressure located over southern Canada that has been responsible for the past few cold evenings. As precipitation began to work its way into the region this morning, stubborn low level cold air held its ground as warmer temperatures aloft began to push overhead. This caused a concern for an area of freezing rain to develop over portions of the Lower Hudson Valley and other locations across southern New England. While some ice pellets and freezing rain was observed, the vast majority of the precipitation over New England has been in the form of snow, especially as we head into northern New England, where temperatures are still in the lower 20’s. The models struggled to show the low level cold air holding on as long as it did over portions of New England, and this led to the snow forecasts to be a little more conservative then they should have been. Regardless, moderate to heavy snow continues over portions of New England, with freezing rain and sleet still falling over portions of southern New York and Massachusetts.

This area of precip should begin to diminish as we head into the evening hours as the main area of lift associated with the first frontal wave weakens. Winds from the south will increase to around 5-10 mph as a surface warm front continues to lift northward and over portions of the Mid-Atlantic, but is once again stopped by the same low level cold air. As this cold air presses down once again, a second wave of energy will push to the south of our region and spawn a low pressure system just off the Mid-Atlantic coast. This second system will lead to more widespread rain developing to the south as the evening goes on. Low temperatures this evening will vary heavily based on location, with portions of southern Connecticut remaining at or around freezing, and locations to the south rising into the 30’s and lower 40’s.

This afternoons high resolution visible satellite imagery, regional radar mosiac, and surface observations showing an area of showers over the NYC area, with snow (some heavy) over New England

This afternoons high resolution visible satellite imagery, regional radar mosiac, and surface observations showing an area of showers over the NYC area, with snow (some heavy) over New England

Holiday Weekend Outlook

As mentioned, more steady rain looks to overtake the region around daybreak tomorrow as a warm front lifts northward over the region. Expect mainly dreary conditions tomorrow as temperatures surge into the well-above normal territory with highs in the lower to middle 50’s for locations closer to the coast, with middle to upper 40’s likely as we head farther north and west from the city. These high temperatures will likely happen later in the day as the low level jet strengthens over the Northeast throughout the day, maximizing warm air advection just around sunset. After the sun sets, the game changes once again as a cold front will quickly move from west to east across the East, which has the potential to bring some gusty synoptic winds, rapidly dropping temperatures, the possibility for some leftover snow showers for locations to the north and west of the city before dry air begins to take over. Lows will likely be able to fall into the middle to upper 20’s and lower 30’s across the entire Northeast during the overnight hours.

Sunday will start off much clearer and cooler as dry air from the backside of the cold front takes over. Mainly dry conditions are expected with a few high level clouds possible as the day goes on and some weak mid level energy begins to move through the area ahead of the next disturbance. Highs will likely remain in the middle to upper 30’s during the day on Sunday, which will be only slightly above normal for some locations. Things begin to get quite interesting later in the evening on Sunday evening as a shortwave trough looks to approach the coast and begins to amplify, leading to the likely development of a weak low pressure system off the Mid Atlantic coast by late Christmas eve. The initial shortwave over the Ohio Valley will likely have a modest amount of snow accompanying it late Sunday night and into the evening hours as it heads east. Conditions should remain dry until around dawn or so, until mostly cloudy skies give way to a mix of light rain/snow for early Christmas morning.

This afternoons NAM model showing the progression of a strong cold front over the East, bringing a return to colder conditions.

This afternoons NAM model showing the progression of a strong cold front over the East, bringing a return to colder conditions.

Christmas Day and Beyond 

A mix of rain and snow will be possible for portions of the area during the pre-dawn hours on Christmas day for locations mainly to the north and west of the NYC area. As the low pressure system off of the Mid Atlantic coast begins to intensify and mature by sunrise, a changeover to all snow may be possible for the remainder of the area. This changeover to all snow may be very breif for locations closer to the coast, and any significant accumulations will be hard to accomplish. For locations to the north and west, this changeover may happen earlier in the morning, and a general 1-3″ may be possible for this reason in those areas. The low pressure system will continue to strengthen through the early afternoon hours, as it quickly heads north and east. Any leftover snow will be quick to shut off, with more significant accumulations likely taking place over southern New England and northward. The rest of the day will likely be quite cold, with highs in the middle to lower 30’s and gusty winds possible.

The end of next week will have the potential to be quite interesting as well as very deep sub tropical moisture will begin to crash into a deep polar airmass located over the northern half over the country by Tuesday. The models have been shifting quite a bit with regards to the surface features, but are rather consistent with the overall synoptic features. The pattern shown from Thursday into late next weekend will be one to watch, as similar ones have produced some rather substantial snow amounts in the past, and it would not take all that much luck to be able to see some plowable snow across the Northeast by the end of the week next week. We”ll have updates on this potential system and the Christmas storm over the weekend with a special announcement sometime around Christmas day!

This afternoons European Ensembles Mean, which shows a pattern in the mid levels that is quite supportive of cold and potentially snowy conditions across the east.

This afternoons European Ensembles Mean, which shows a pattern in the mid levels that is quite supportive of cold and potentially snowy conditions across the east.

Have a great night!

 

Steven Copertino

Southeast Ridge Builds, But Not For Long…

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Good evening! 

 

Today was another relatively mild day with some decent mid-upper level cloud cover that faded throughout the day as a weak disturbance to our south quickly moved eastward. High pressure over central and eastern Canada remains in control of the weather over much of the northern tier of the United States and has prevented the northward progression of the weak disturbance over the southeast US. This same high pressure system has also ushered in a colder airmass into the mid levels of the atmosphere, with the surface temperatures lagging behind. This lag-time between the surface and mid levels has allowed highs today to reach into the lower to middle 40’s across much of the New York metro area, with some locations in southern NJ reaching into the upper 40’s. As the evening goes on, we should see clouds continue to decrease in earnest, with only a few high cirrus clouds sticking around through the night as dry air continues to sink into the Northeast. With the relatively clear conditions expected, a renewed source for cold air, and light winds, conditions this evening will become quite favorable for radiational cooling to occur over the entire Northeast. We should see lows drop a good 15-20 degrees, with readings getting into the middle to upper 20’s across most of the metro area. Low 20’s and possibly teens will also be acheiveable to the north and west of the city due to excellent radiational cooling conditions in the valleys of NY state.

Snapshot of todays weather across the Northeast with regional radar mosiac, surface observations, and 500-meter high-resolution visible satellite data from GOES 16. Note the sharp cutoff of cirrus clouds just to the south of NYC

Snapshot of todays weather across the Northeast with regional radar mosiac, surface observations, and 500-meter high-resolution visible satellite data from GOES 16. Note the sharp cutoff of cirrus clouds just to the south of NYC

Thursday Into the Holiday Weekend 

Thursday looks to start off rather cold and clear as high pressure to our north remains in control of the weather. Temperatures during the morning commute will likely start off in the middle to upper 20’s, but as the day goes on tomorrow we should see clear skies and light northerly winds result in highs heading into the lower to middle 30’s, with upper 30’s to lower 40’s possible across southern New Jersey. Downsloping winds will cause of good amount of subsidence over the region tomorrow, so expect generally dry and clear conditions for the vast majority of the day. As we head into the evening hours tomorrow, ridging ahead of a growing system out in the plains will cause heights to rise over the East, which should bring an increase in mid level moisture. Clouds should gradually increase as darkness falls tomorrow, likely becoming mostly cloudy as the night progresses. With the increase mid level heights will come a more stout southwesterly flow over the region, which will work to increase mid level temperatures. Despite a marked increase of about 5-10 degrees in the mid levels, the high pressure to our north will continue to pump colder surface air into the Northeast. This more-dense cold air should win out against any potential warm air intrusions Thursday night, so look for lows to range in the middle to upper 20’s once again, with warmer lows in the 30’s expected to the south and west.

By Friday morning, we should see a significant amount of energy in the desert southwest that should help to pump the much-talked-about “southeast ridge” over the southeast. Moisture will begin to stream in over the ridge on Friday and pool ahead of a slow-moving cold front over the Tennessee valley. Southwest flow will increase throughout the day on Friday, leading to increasing temperatures and a threat for showers during the day. It is important to note that some of the precipitation at the onset of this system may actually be in the form of sleet/freezing rain/snow across locations to the north and west of the city due to stubborn low level cold air trying to hold on. Depending on how much this cold holds on, we could see a period of a light wintry mix into the early afternoon which may cause for slippery travel conditions. Regardless, expect much of the day to be unsettled with cloudy conditions and a chance at showers. Highs will be slightly warmer over the area on Friday, with temperatures in the 40’s expected for much of the Northeast.

This afternoons NAM model showing the building mid level ridge over the central part of the country, followed by a large supply of Polar air developing over southern Canada.

This afternoons NAM model showing the building mid level ridge over the central part of the country, followed by a large supply of Polar air developing over southern Canada.

 

Holiday Weekend Outlook and Beyond! 

More rain steady rain is likely for Saturday and into Sunday before things clear out on Sunday morning. A large piece of Pacific energy will be carving out a trough in the central United States that will work to pick apart the southeast ridge. A polar airmass will then flow into the back end of this trough, which should create a tight gradient between the warmer SE ridge and the cold over the Plains. The models begin to differ late on Christmas eve when a low pressure may develop over the Tennessee valley. This afternoons European model has trended colder and more to the south and east with this low, and would bring a rather significant snowfall on Christmas day as the low rides the temperature gradient, then quickly strengthens. Some of the other model guidance places this initial temperature boundary a little farther south, which causes the bulk of the system to ride out to sea with little fanfare for the Northeast. While the details still need to be worked out quite a bit, condition’s on Christmas are looking to be colder than originally forecast with the potential of a wintry day across the Northeast. This will be looked at much closer on Friday when most of the model guidance will be in their more-reliable range.

By Tuesday, we should see the polar cold begin to bleed into the Northeast as a large high pressure system takes over much of the eastern US. This cold will be setting the stage for a potentially wintry end to 2017 as the medium range models are beginning to sniff out a potential system arriving on the west coast  by next Wednesday. There will be the potential for another Polar airmass to invade the country, with a massive high pressure system over much of southern Canada. This high pressure system over Canada would then lead to any potential system developing in the Plains states to ride generally east. This kind of track would allow precipitation to break out over a large portion of the country as moisture streams northward from the Gulf of Mexico. With Continental Polar air filtering into the Northeast, there would be a heightened threat for snow as we draw closer to the 12/27-12/31 time frame. We will also be keeping a very close eye on this period over the next couple of day and provide updates when they’re available.

 

This afternoons European Ensembles showing a potentially cold and active period coming in the next 10-15 days as mid level ridging increased over the Arctic regions.

This afternoons European Ensembles showing a potentially cold and active period coming in the next 10-15 days as mid level ridging increased over the Arctic regions.

Stay tuned for further public updates! . Also join us at 33andrain forums for free discussion on everything weather-related.

Have a great night!

 

Steven Copertino

Zonal Pattern Gives Way to More Extremes Across the Country

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Good Evening! 

A weak area of mid level energy moved quickly through the Northeast last evening and into the early morning hours today, which had just enough kick left to it to bring  some isolated and relatively light areas of precipitation. Depending on your location, this precipitation varied from plain rain, freezing rain, or even some light snow. Any frozen precipitation accumulations were extremely light, but still made for a slick morning commute today. The quick-moving west to east flow that has become established over the majority of the country will be responsible for bringing some more weak mid-level energy over the region through the rest of the day, which has led to a rather dreary and  warmer day than the past couple of days. West/southwesterly flow has allowed mid level temperatures to rise over much of the Mid-Atlantic and Northeast, which has allowed surface temperatures to respond accordingly throughout the day. We have seen highs across much of the Northeast rise into the lower to middle 40’s across the majority of the area, with higher readings around the 50’s observed in portions of southern New Jersey. These mostly cloudy and slightly-above normal temperatures should continue into the evening hours, with a chance of some patchy fog across the area as some moisture may become trapped within a low level inversion.

Expect temperatures this evening to fall back into the upper 30’s and lower 40’s across the immediate NYC metro area, with cooler temperatures likely well to the north and west.

This evenings latest regional radar mosaic, GOES 13 visible satellite imagery, and surface observations showing a more mile and dreary end to the day across much of the Northeast

This evenings latest regional radar mosaic, GOES 13 visible satellite imagery, and surface observations showing a more mile and dreary end to the day across much of the Northeast

Tuesday Into Thursday 

A deep cyclone moving through portions of central and eastern Canada will continue to drag a rather stout southwesterly flow over the Northeast tomorrow afternoon, which should also bring in more dry air to clear out the low-mid levels of the atmosphere. This should allow for a vast majority of the clouds to dissipate as the day goes on tomorrow. This deep southwesterly flow and relatively clear skies across the area should allow temperatures to rise into the “well-above normal” territory as highs will likely get into the middle-upper 40’s-with some 50-degree readings possible. Thankfully, moisture will be quite limited across the east, so we expect a generally calm and mild day tomorrow for much of the Northeast. Later in the day, a cold front associated with the same cyclone in Canada will begin to creep into the Northeast. This front will work east through the area throughout the overnight hours, but will likely bring lows down into the upper 20’s to low 30’s just in time for the morning commute on Wednesday.

Wednesday  should be a much cooler day by contrast as northwesterly flow behind the cold front ushers in fresh, Canadian air. A vigorous little area of mid level energy will be opening up from its time as a closed upper level low and will begin to quickly head east across the southern half of the country. This strong west to east flow across the nation will ensure that this area of energy becomes sheared out, with all of its rain staying well to the south of the Northeast. In fact, conditions will remain very dry across the Northeast, and there may be a couple of strong post-frontal wind gusts in the early part of the day. The renewed northwesterly flow, clear skies, and dry air should allow temperatures to stay relatively cool across the majority of the region, with highs in the middle to upper 30’s likely. Locations to the north and west may in fact see highs stuck in the lower to middle 30’s as some deeper Canadian air becomes trapped. These calm and cooler conditions will last into the evening hours on Wednesday before another weak cold front begins to move into the east. This front will be severely moisture starved, but will be capable of reinforcing the cold air already in place. With dry low/mid levels, cold air aloft, and light northerly winds, conditions should be supportive of some radiational cooling to take place. This should bump lows down into the middle to upper 20’s , with upper teens to middle 20’s likely off to the north and west.

Thursday morning will see the reinforcement of colder air over the Northeast, with the morning commute likely starting off quite crisp in the 20’s. A mid-level ridge will begin to build over the Ohio Valley in response to an area of Pacific energy digging into the west coast, but conditions over much of the Northeast will likely remain quite cool and clear as high pressure begins to build and expand over southeastern Canada. This should lead to another pleasant day with highs mainly in the upper 30’s to lower 40’s. Mid level flow will begin to shift to the southwest during the evenings hours on Thursday, which will begin to set the stage for another above-normal period of temperatures.

Loop of this evenings NAM model showing a brief period of cooler temperatures over the Northeast, followed by another warm surge by the end of the week.

Loop of this evenings NAM model showing a brief period of cooler temperatures over the Northeast, followed by another warm surge by the end of the week.

Uncertainties Arise for Christmas Weekend 

If you’re on social media and follow some of the various weather pages out there, you’ve likely seen the numerous maps and forecasts that show a massive area of Arctic air dropping into the west, while a large area of warmth rises over the east. While the exact details of how this weekend will play out are still a couple days from being hashed out, what we know about this setup is that there will be a substantial amount of Pacific energy dumping into the west by Friday. All this energy injected into the flow will begin to carve out a large trough over the western/central US, while the downstream response will likely result in a ridge forming over or just off the southeast coast. This pattern will be supportive of increased heavy precipitation over the Southeastern to Northeast US as the gradient between the cooler airmass over the central US clashes with the relatively warmer airamss over the east on Friday and Saturday. Shortly after, the models begin to diverge on just how much the trough and accompanying cold is able to move east by Sunday/Monday. The other major question here will be where exactly does the ridge over the southeast set up? A ridge over the southeast will almost certainly guarantee an above-normal Christmas day, while a ridge off the eastern seaboard may allow cold to creep into the picture just in time for Christmas. These details will take a couple more days to flesh out, and we will certainly be monitoring them over the course of the week.

This afternoons European Ensembles showing a rather significant amount of spread in the overall 500mb pattern for Christmas day, showing nothing is set in stone yet.

This afternoons European Ensembles showing a rather significant amount of spread in the overall 500mb pattern for Christmas day, showing nothing is set in stone yet.

Stay tuned for further public updates! . Also join us at 33andrain forums for free discussion on everything weather-related.

Have a great night!

Steven Copertino

First Widespread Snowfall of the Season Likely Saturday!

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Good Evening Folks! 

Well the close-call we warned you about on Monday has trended much closer to the coast over the past 48 hours, and looks to deliver the first light to moderate snowfall for many locations long the I-95 corridor! The setup for this storm has been a cold one, as a weak area of high pressure attempted to build over the Mid Atlantic states this afternoon. This area of high pressure has brought a more substantive portion of the Arctic airmass that lies just to our north, and this could certainly be felt today as the air had more of a “bite” to it. This Arctic air is also noticeably more dry than the previous stale airmass that has been in place, and will play a role in the snowfall forecast for tomorrow. Regardless, today’s highs were a bit colder than the past few days due to the reinforcement of the colder air and some mid to high level clouds streaming in overhead. The vast majority of the Northeast saw highs in the lower to middle 30’s, with middle to upper 30’s closer to New York and Philadelphia. This is just below normal for this time of year, and should be the norm for the next couple of days.

As we head into the evening hours, skies should remain mostly cloudy as more mid to low level moisture streams in thanks to a stout mid level jet transporting rich tropical moisture northward. As I mentioned earlier, there is a good amount of dry air in the mid to lower levels of the atmosphere, this should hold off the snow until the very early morning hours of Saturday. Locations farther south in portions of New Jersey may see an earlier start time due to more available moisture. In fact, Cape May New Jersey is currently seeing moderate snow, but this may be due to a moist marine airmass in that area. Overall, expect the mostly cloudy conditions to continue overnight, with lows likely dropping into the upper 20’s and lower 30”s across much of the New York city area. There is the possibility that the dry air will not be able to hold on for as long as the models expect, and portions of New Jersey, Maryland, Delaware and Pennsylvania could see some light snow before sunrise. Only light accumulations around a trace to two inches would be expected if this were to occur.

This evenings last-light visible satellite imagery, surface observations, and regional radar showing precipitation starting to work north into the Northeast.

This evenings last-light visible satellite imagery, surface observations, and regional radar showing precipitation starting to work north into the Northeast.

 Moderate Snowstorm Likely Saturday

The massive area of tropical moisture that we talked about back on Wednesday has certainly left its impact across the south over the past 36 hours, with snow being reported in all of the Gulf Coast states except for Florida. This system is being aided by a very strong and anomalous upper level jet streak overhead, which is working to promote the development of intense precipitation over the southeastern states. This system is not the only player for our storm tomorrow, as we have also been tracking an energetic piece of energy diving down from the far northern regions of Canada. As this system continues to move south and into the Great Lakes region, it will begin to interact with the system over the southeast and begin to create a favorable environment for the development of a coastal low to form just off the southeast coast. As this low continues to take shape and the two systems begin to interact further, we should see the bulk of the precipitation begin to move north and expand quite a bit over the Northeast by the early tomorrow morning. This expansion of the precipitation was something that was not well-handled by the models a couple days ago, and is likely to due to the very strong upper level jet streak aiding to the development of precipitation over the area. Snow should start from south to north tomorrow morning, and eventually making its way into the NYC area by 11am or so.

This evenings latest RPM model showing the potential evolution of tomorrows snowstorm across the Mid Atlantic and Northeastern states

This evenings latest RPM model showing the potential evolution of tomorrows snowstorm across the Mid Atlantic and Northeastern states

We may see a period tomorrow morning where the radar looks to have snow over certain locations, but nothing is actually falling at the surface. This is due to the dry air in the mid to low levels of the atmosphere that  causes snow to evaporate before it reaches the ground, but the radar beam still detects it when its far above the ground. This dry air will likely give way once the coastal low begins to intensify off of the Carolinas late tomorrow morning and into the afternoon hours. Expect the snow to start off rather light during the onset, but transition to a more steady rate for the duration of the storm. Portions of eastern New Jersey, southern New York, Long Island and Connecticut may see a few hours of heavy snow, with rates possibly nearing .5″-1″ an hour. Snow should continue through the late afternoon hours and into the evening, before tapering off from southwest to northeast during the early morning hours on Sunday.

As of right now, we are expecting a large swath of accumulating snow totals around the 3-6″ range from southeastern Pennsylvania, through most of New Jersey, and into New England. There may be localized amounts greater than six inches, but this may be confined to southern and eastern portions of the area where heavier snow bands may set up. Road conditions will likely be quite messy tomorrow as the snow is likely to create slippery conditions as it begins to ramp up in intensity. Travel may become hazardous during the afternoon hours during the peak of the storm, so it may be a good day to stay inside and get some work done and stay off the roads unless necessary. We will have updates on this storm after this evenings model runs come in as well as throughout the day tomorrow!

Storm total snowfall forecast

Storm Total Snowfall Forecast Map

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Have a great evening!

-Steve Copertino