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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 

Steven Copertino

Brief Warm-up This Weekend, Colder and Potential for Some Snow Early Next Week

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Good evening! 

Today has been another cold, but seasonable day across the entire Northeast as an area of high pressure continues to push off the Mid Atlantic coast this afternoon. Mid level heights have been rising over much of the East coast ahead of a large, but a disorganized mass of energy moving through the central Plains over the past 24 hours or so. These mid level height rises have allowed warm mid level temperatures to move in from the south and over much of the Mid Atlantic region and Northeast, which is the beginning of a more above-normal airmass arriving. With relatively clear skies, stout southerly mid level flow, and light surface winds, we were able to see much of the Northeast rise up into the middle to upper 30’s, with locations off to the south seeing highs get back into the 40’s. Generally clear and calm conditions will exist into for the rest of the evenings and into the overnight hours as dry air exists throughout the low to mid levels of the atmosphere. We should see low temperatures drop a good deal this evening as high pressure remains in control for the most part. Winds will be light from the south, and when coupled with cool and dry mid levels of the atmosphere, we should see readings range from the lower to upper 20’s across much of the NYC area, with lower to middle 30’s possible over southern New Jersey.

This afternoons latest high resolution visible imagery, regional radar mosaic, and surface observations showing a cold, but seasonable day across much of the Northeast

This afternoons latest high resolution visible imagery, regional radar mosaic, and surface observations showing a cold, but seasonable day across much of the Northeast

This Weekend 

Saturday will likely start off as another cold and clear morning as the area of high pressure off the Mid Atlantic coast hangs on for control of the weather for our area. Stout mid level flow from the southwest will continue to pour in from the southern Plains, which will finally cause surface temperatures to respond in a big way. The combination of clear skies, southerly winds and stronger mid level flow should cause highs to get into the middle to upper 40’s across much of the region, with some locations likely breaking into the lower 50’s during the afternoon hours. This will be quite a bit above normal for this time of year and should make for an excellent day to spend outside.  Calm and warm conditions will last through the late afternoon hours and into the evening as the mid level ridging begins to wane to our east. As the mid level ridging backs away, a cold front will begin to make its way into the Northeast by 8-10pm. Cloud cover should rapidly begin to increase as moisture streams in from the south and begins to saturate the lower levels of the atmosphere. Showers should gradually overspread the Northeast overnight, with more steadier rain working its way from west to east by around 2-4 am. Though this front will have Gulf moisture linked to it, the moisture content will not be all that deep, so precip rates and amounts should generally remain in the light to moderate range. We could also see some gusty winds ahead of the front, with winds clocking in around 20-35 mph at times.

Light to moderate rain should last into the early morning hours of Sunday as the cold front continues to move rapidly from west to east. By the afternoon hours the front is expected to be located offshore and we should begin to see dry air from the west begin to fill in behind the front. This should lead to gradually clearing skies and a more westerly/northwesterly winds for the remainder of the day. As skies clear, we should still see temperatures be capable of rising into the lower to middle 40’s with some locations seeing highs in the upper 40’s once again due to warmer low level air lingering around. Sunday night should be rather pleasant as continued clearing and winds from the northwest will remain prevalent over the Northeast.

This afternoons high resolution NAM model showing the progression of the cold front progged to move across the Northeast from Saturday night and into Sunday

This afternoons high resolution NAM model showing the progression of the cold front progged to move across the Northeast from Saturday night and into Sunday

Watching the Coast on Monday and Tuesday 

Things turn interesting starting Monday morning as mid level energy begins to dive into the southern Plains and Ozarks as an area of ridging begins to amplify over the West coast. As this area of energy continues to dig to the south and east, a healthy upper level jet streak will begin to develop overhead. This will promote the development of precipitation off of the southeast coast, which will in turn help to form a weak area of low pressure moving to the northeast by late Monday afternoon. What happens from this point is highly uncertain at this time, but there do appear to be two scenarios that stick out at this time. The first scenario is that the energy in the Tennessee Valley is not far enough south and compact to support the weak area of low pressure strengthening close to the Mid Atlantic coast. In this scenario, the upper level jet streak would be the main driving feature for any precipitation, which would likely be confined to the immediate coast and should be light in nature by Monday night and into Tuesday morning. The next scenario is that the area of energy is stronger and more amplified that what the current computer models are showing, therefore allowing the development of a stronger low pressure system close to the Mid Atlantic coast. As the storm strengthens, the already favorable upper level jet streak would enhance precipitation over the Northeast and some locations could be looking at a light to moderate snowstorm from Monday evening and into Tuesday afternoon.

As of this afternoon, the models are not in agreement with one another, with a wide variety of scenarios being shown. Given the lack of upstream blocking to slow down the mid level energy and allow the low to strengthen, this would usually be a pretty cut and dry forecast, however we have seen a very distinct trend this Winter where snowstorms like to trend more amplified and closer to the coast inside of two days. As of right now we are leaning on the side of caution and using a blend of some of the models that have been performing particularly well this winter. Henceforth, there is a possibility of accumulating snow along coastal and interior locations late Monday evening and into Tuesday. Amounts should generally be light, with coastal locations likely seeing a period of mixing due to the weaker nature of the low pressure system.

However, we must say that there could be some significant model shifts in the next 48 hours that could potentially bring more moderate snow into play, and therefor we will be closely monitoring this system so make sure to check back for updates!

This afternoons European Ensembles showing a low-medium potential for a moderate impact from the potential Nor'Easter on Monday night

This afternoons European Ensembles showing a low-medium potential for a moderate impact from the potential coastal low on Monday night

Have a great weekend!

Steve Copertino 

 

John Homenuk

Friday AM Briefing: Changeable weather in the East, wintry threat next week?

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Good morning, and Happy Friday! Finally. Cold and dry weather built back into the Northeast states on Thursday, and temperatures dropped near or below normal in many locations thanks to a transitional trough moving through Southeastern Canada. Such has been the nature of this pattern over the past week or two – relatively fast moving, without any slow or cutoff storm systems. As we look ahead to the weekend, things are likely to warm up across the Northeast States.

A ridge rolling eastward from the Central Plains, which is bringing above normal temperatures to a large majority of the Central United States today, will move towards the Eastern United States this weekend. While surface temperatures won’t exactly be torching, temperatures will rise well above seasonal averages over a large area. A frontal system will then bring the opportunity for rain on Sunday across the Tennessee Valley, Mid Atlantic and Northeast.

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