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Quick-Hitting Snowstorm Likely for Portions of the Northeast Saturday Night

February 16, 2018/by Steven Copertino

Good evening!

Today has been yet another in a string of warmer and unsettled days across the Northeast, with light to moderate rainfall training over portions of the Mid Atlantic and Northeast. Today’s rain was part of the same strung-out and progressive upper level energy that was responsible for the heavy rain and flash flooding that occurred over portions of the Ohio Valley and Mid Atlantic states last evening. The heavy rains last evenings moved quickly along a frontal boundary that remained stationary over the same areas, causing showers and even some embedded thunderstorms to train over the same locations. While the vast majority of these showers and thunderstorms very quite weak in nature, there were some stronger storms over the Ohio Valley and Northeast that produced some damaging wind gusts, along with an EF-1 tornado just to the south and east of Pittsburgh. Regardless, today was a rather dreary day across the entire region as the mid level energy over the Ohio Valley quickly moved east and caused numerous showers to break out once again. The showers have since moved offshore as the majority of the mid level energy moves off to our east, leaving behind mostly cloudy conditions. Despite the mostly cloudy and rainy conditions today, temperatures were able to rise to above-normal levels once again across the Northeast. Readings varied from the lower to middle 50’s over the New York metro area, to middle 50’s to lower 60’s across portions of southern New Jersey. These mild conditions should last until the late evening hours as a cold front begins to approach the area from the west, bringing in cooler temperatures overnight along with Northwesterly winds. High pressure will begin to build in over the Northeast tonight, with lows likely falling quite a bit into the middle to upper 20’s over the majority of the area, with lower 20’s expected to the North and West of the city. Calm conditions will likely prevail through the overnight hours as the high pressure expands over the Northeast.

This evenings latest high restitution water vapor satellite imagery along with regional radar mosaic and surface temperatures from across the area. Note the clearer and more dry air over portions of northern PA and NY.

Quick-Hitting Snowstorm Likely Tomorrow Across Portions of the Northeast

Well, with the way this week has went the last thing you would expect is a snowstorm for this weekend, but that is exactly what looks to be shaping up for portions of the Mid Atlantic and Northeast tomorrow night into Sunday morning. A weak a relatively disorganized area of mid level energy will become trapped in the fast-moving west-to-east flow over the CONUS tomorrow morning and begin to race towards the East. As it reaches the Great Lakes region tomorrow afternoon, it will begin to meet up with some energy from the sub-tropical jet over the Southern Plains states, and this will likely cause numerous showers and some localized thunderstorms to develop over portions of the Tennessee valley. At the same time, the area of high pressure that will be over the region this evening will be moving off of the coast, leaving some stale cold air over the region. Winds will begin to shift to the south over the Mid Atlantic and Northeast, bringing in a slightly warmer low level airmass for tomorrows highs, but overall temperatures look to stay in the middle to upper 30’s. As we get deeper into the evening hours tomorrow, we should see the shortwave trough associated with tomorrows potential storm begin to amplify or strengthen a bit as the ridging over the southeast and western Atlantic causes the system to buckle.

This afternoons NAM model showing the potential evolution of tomorrows snowstorm

As the mid level energy begins to strengthen tomorrow evening, we will also see the upper level jet streak associated with this system begin to expand, allowing precipitation to break out farther north into portions of the Mid Atlantic by sunset. Surface low pressure should then begin to develop over the Mid Atlantic coast tomorrow night, with snow quickly expanding from southwest to northeast over the Northeast. This afternoons model guidance still shows a reasonable amount of uncertainty with the strength of this system, which will be crucial to this forecast. Depending on how deep this low gets will determine how much dynamic cooling will take place as the precipitation is falling. A weaker storm will be warmer at the surface with less precip, and therefore less snow. A stronger system will be able to overcome marginal surface temperatures and have increased snowfall rates, yielding higher snow totals. At this time, a healthy compromise of the two seems plausible. Precipitation may start off as a mix of snow and rain over southern portions of the Northeast, but should turn to all snow by 8-10pm or so with the exception of immediate coastal areas. The snow will quickly become moderate to heavy over portions of Pennsylvania, New Jersey and New York, with an enhanced chance at mixing over Long Island due to easterly winds. Moderate to heavy snow should continue through the overnight hours, likely until 3-5am as the system quickly accelerates to the north and east and moves offshore. Totals will likely vary by location and elevation over the region, but right now we expect a general 3-6″ from southeastern PA through northern NJ, and into SNY and CT. Portions of Long Island may see less than shown here due to prolonged periods of mixing. Travel conditions will likely be quite hazardous if you plan on driving tomorrow evening, so please stay up to the date with your local NWS for any watches or warnings in your area!

Our latest storm total snowfall map

We will have updates tomorrow on this system including a new snowfall map!

Have a great weekend!

Steve Copertino

Mild and Unsettled Pattern Begins to Take Shape

February 12, 2018/by Steven Copertino

Good evening!

The dreary and wet conditions that took over back on Saturday afternoon have finally begun to break as a cold front pushed through the Northeast this morning and early afternoon. Rainfall amounts were in the moderate range for most of the Mid Atlantic and Northeast, with locations closer to the immediate coast seeing totals in the 2-4″ range. Widespread was not recorded due to most of the Mid Atlantic and sections of the Northeast actually being in a drought do to a lack of any substantial precipitation over the past few months. Luckily, this recent rainfall was very beneficial to the area, and may have been able to knock some locations back to around normal precipitation departures. Regardless, most of the area saw their Monday start off rather mild, with highs being recorded in the morning hours over a large portion of the Northeast. This was due to a cold front that has been lagging begin the main system which actually pushed offshore last night with the remaining bulk of the heavy rain. As this cold front moved through portions of the Northeast, the cold air was quick enough on the backside to catch up to the remaining precipitation and cause a very brief mix of rain/snow/grauple. These spotty areas of mixing were quite light and brief in nature, so no accumulations were recorded. Conditions became rather calm, with even some patchy sun showing up for the middle and later afternoon hours, as temperatures over the region leveled off in the upper 30’s to lower 40’s. Conditions should remain quite dry, but occasionally a bit gusty as drier Canadian air filters into the region tonight. A strong area of high pressure will also be gradually building in over the Northeast from west to east, so this will ease winds overnight and cause clouds to gradually subside. Lows should be rather cold, with location around the NY metro area likely seeing temperatures in the lower to middle 20’s, with locations off to the north and west likely getting down into the teens with good radiational cooling.

This evenings latest surface temperatures from the HRRR with surface observations and the regional radar mosaic showing a rather calm, but cooler night taking shape

Tuesday Into Thursday

Tomorrow should start off rather clear and cold, as the aforementioned strong high pressure system continues to move over the Northeast. A fast zonal (west to east) jet streak will still be dominating the pattern across the entire country. This mean that any system over the next couple of days will be moving very quickly across the United States, with no time to amplify or strengthen. This will be the case throughout the entire day on Tuesday as some shredded-off energy from a decaying system over the west moves into the Mid Atlantic and Northeast. This energy is too insignificant to cause anything other than some high-level cirrus clouds during the afternoon hours tomorrow as the jet stream roars overhead. Highs tomorrow should be rather seasonable, with temperatures likely staying in the middle to upper 30’s, with some locations off to the south of the city possibly getting into the lower 40’s. Tranquil conditions will last well into the evening and overnight hours, as radiational cooling allows lows to drop once more into the middle to upper 20’s, with locations off to the north and west in the lower 20’s.

Mid level ridging will begin to build over the Plains during the day on Wednesday, leading to southwesterly flow increasing quite a bit over the Mid Atlantic and Northeastern states. This will begin to cause the classic response of mid level temperatures rising as well as moisture beginning to stream northward from the Gulf of Mexico. Showers and thunderstorms will likely begin to develop over the Southeast Wednesday afternoon, with some of that moisture possibly making it into the central parts of the Mid Atlantic before dark. Conditions will likely turn at least mostly cloudy during the day as increased moisture leads to the development of mid level clouds over much of the Northeast. Despite the clouds, temperatures should be quite mild, with highs likely getting into the middle to upper 40’s, with some locations likely hitting the lower 50’s. The threat for some showers will gradually increase as the night goes on, with showers likely moving in around 10pm or so for the New York metro area. Lows will be much more tame on Wednesday night, with readings likely staying in the upper 30’s to lower 40’s.

Thursday will be the first much above normal day in the period as a trough over the Western US states continues to cause the downstream strengthening of ridging over the East. Moisture from the Gulf will continue to move northward over the entire Northeast, likely leading to a wet start to the day on Thursday. As mentioned earlier, the mid level disturbance responsible for this rain will be so disorganized and moving so quickly that only light rainfall amounts are expected. The exact temperature forecast is a little complicated at this time and will depend on just how quickly the rain showers will be able to move out, but it certainly looks like highs should be able to rise well into the upper 50’s and lower 60’s across much of the Mid Atlantic and southern portions of the Northeast. Conditions will likely remain unsettled with spotty showers possible throughout the rest of the evening and overnight hours, as another in a series of weak disturbances pass through the Ohio Valley

This afternoon European ensembles showing a high probability of temperature anomalies reaching 20 degrees above normal on Thursday!

Mixed and Mild Weekend Ahead

The same pattern looks to almost certainly continue through this weekend as the southerly flow increases once more on Friday ahead of a large area of disorganized energy out over the Plains . A more moderate rain event may be in the cards starting on Friday as more Gulf moisture becomes available over the South. A cold front behind this system looks to temporarily cool things down a bit late in the day on Friday, but Saturday looks to still be a slightly above normal day across the East as mid level ridging starts to buil over the Plains once more. This area of ridging looks to strengthen quite a bit over the east on Sunday, allowing high pressure to get pushed off of the east coast and provide strong southerly flow once more for the entire area. This looks to set the stage for an even larger warm-up next week as some models are depicting a very deep trough to set up in the west, which would be strongly supportive of much above average temperatures lasting through the week next week. In fact, this afternoons European model had many locations across the Northeast well into the 70’s by next Thursday! This can very easily change over the next couple of days, but we will continue to monitor this period of prolonged above normal temperatures!

This afternoons European ensembles showing a very warm pattern shaping up in the medium range across the East

Have a great night!

Steven Copertino

Heavy Rain Likely This Weekend, Mild and Unsettled Through Next Week

February 9, 2018/1 Comment/by Steven Copertino

Good evening!

Today has been another cold, but relatively calm day across much of the Northeast and Mid Atlantic. Some weak lift associated with a frontal boundary over the region has spark some patchy areas of light snow and snow flurries, mainly confined to the western parts of New York State as well as southern New York and northern New Jersey. These areas of precipitation will gradually shift north over the rest of the evening as the frontal boundary and lift also begin to gain more latitude. Since precip rates will be rather low and conditions are not ideal for snow accumulations, only a trace is expected for the locations that manage to see more sustained light snow. Otherwise, high pressure retreating off of the Mid Atlantic coast will contribute to more southerly flow this evening, which will begin to bring in a more mild airmass in the mid levels of the atmosphere. Additionally, moisture will begin to increase and this will likely cause the rest of the evening to remain rather cloudy. Lows this evening will come quite early in the evening as the warm air moving into the mid levels of the atmosphere will also help to warm things up tonight after midnight. Most of the area will see lows in the upper 20’s to middle 30’s, but these will rise into the middle to upper 30’s during the overnight hours, with come locations in southern New Jersey likely reaching the 40’s.

This afternoons current surface observations, regional radar mosaic, and high resolution satellite imagery showing a cold day across the region with areas of light snow

Heavy Rain Likely Sunday

Saturday will likely start off rather mild and with substantial overcast as mid to low level warm air and moisture continue to stream in over the region from the south. This surge in mild temperatures and moisture will be thanks to a large, but disorganized area of mid level energy extending from the West coast, all the way into the Great Lakes. Additionally, the sub-tropical jet stream will also be getting involved by pumping moisture-rich air from the Gulf of Mexico into the southeast United States, creating a large area of showers and thunderstorms. These showers and thunderstorms will gradually work their way north during the day on Saturday, likely working their way into the Mid Atlantic and Northeast by the late afternoon hours. Conditions will almost certainly remain unsettled with a chance of showers lasting well into the evening hours. Highs on Saturday will be quite mild, with most of the Mid Atlantic and Northeast likely getting into the lower 40’s, with some locations to the south possibly seeing highs in the lower 50’s! We’ll have the same situation tomorrow night as we did tonight, were temperatures during the overnight hours actually rise, with temperatures likely getting well into the 40’s and even middle 50’s for portions of the Mid Atlantic and southern New Jersey.

Conditions should really deteriorate during the early morning hours of Sunday morning, as warm/moist air surges ahead of semi-stationary frontal boundary out over the Ohio Valley. Early Sunday morning and into the afternoon hours should virtually be a washout, with a threat of heavy downpours across much of the Mid Atlantic and Northeast. The main batch of moderate to heavy rain should gradually push north and east off the coast during the middle afternoon hours, but there will still be a threat of some steady showers ahead of the last concentrated batch of rain. This last batch looks to come into the Northeast around 6-8pm on Sunday, with some locally heavy rainfall likely. This area of showers will also have a chance at producing some gusty winds as the low level jet streak a few thousand feet above the ground begins to strengthen. Rainfall totals should be above an inch for interior sections of the Northeast, with higher amounts around 1.5-2″ closer to the coast. The threat for stream flooding is rather low at this time, but there could be some urban flooding in locations that are prone to poor drainage. However, this will be highly dependent on just how much rain falls over the six to twelve hours or so on Sunday. Highs on Sunday will be quite impressive, with readings likely breaking into the 50’s areawide ahead of the cold front. Some locations to the south may even make a solid run at the 60’s later in the evening on Sunday.

This afternoons NAM model showing the progression of the heavy rain set to impact the region into Sunday night

Unsettled and Mild Next Week

A frontal boundary will move across the Northeast and off the Mid Atlantic coast by Monday afternoon, which should be able to kick most of the moist/unstable airmass out of the region temporarily. Temperatures should moderate back into the upper 30’s to lower 40’s for the most part on Monday and Tuesday, but the large and disorganized area of mid level energy out over the west will begin to undergo a change. This system will gradually drift south and begin to break off from the main upper level flow, causing another period of zonal winds to rage from west to east over the country. As these zonal winds take over, we’ll see more moisture begin to surge northward from the Gulf of Mexico by Wednesday. As this moisture moves over the region, temperatures will once again return to well-above normal across the Northeast. In fact, this afternoon European model even shows the potential for the NYC to get into the 60’s by Thursday, which would likely challenge some records. The best threat for rain appears to be on Thursday as the bulk of the Gulf moisture moves up and over the Northeast. It is too early to say whether or not there will be a heavy rain threat from this system, but we will certainly be monitoring things over the next week or so and provide updates when needed!

The European Ensembles probability of reaching/exceeding 50 degrees by next Thursday-showing a rather high chance over portions of the Mid Atlantic and Northeast

Have a great weekend!

Steve Copertino

Wintry Mix Exits, Unsettled Pattern Sticks Around Through Next Week

February 7, 2018/1 Comment/by Steven Copertino

Good Evening!

The area of low pressure that moved inland over much of the Northeast is finally beginning to wind down, with precipitation shutting down from west to east. The storm initially came up from the southwest early this morning, producing a wide area of snow and mixed precipitation over much of the Mid Atlantic and Northeast. The areas that did start off as snow around the New York metro area this morning gradually saw the snow change to sleet, and then light to moderate patches of freezing rain as warmer air in the mid levels began to push north. As mentioned on Monday, there was a chance that the low level cold would be under-modeled as it has many times in the past, and that is exactly what happened this morning/afternoon. Despite mid level temperatures above freezing a few thousand feet above the ground, surface temperatures remained at or below freezing just long enough to allow for quite a bit of freezing rain to fall across southern portions of New England as well as portions of the Mid Atlantic states. This freezing rain caused very hazardous travel conditions for the morning commute, with many folks getting caught off-guard by the unexpected slick conditions. As the area of low pressure continued to move to the north and east this afternoon, warm air began to surge in at all levels, and this caused most, in not all of the precipitation in the area to turn to plain rain. Some locations in southern New England are still dealing with light to moderate freezing rain, while locations well to the north are dealing with moderate to heavy snow.

Continued moderate rain will be likely over portions of the Mid Atlantic and southern portions of the Northeast through at least 8pm, with precip gradually ending from west to east. Colder air will be working its way east as well behind a frontal system, so there will be a slight chance that the precip could end as light snow or a light mix. Temperatures will once again drop below freezing this evening, with much of the area seeing lows drop back into the middle 20’s, with locations off to the north and west likely flirting with teens due to the snow cover. Regardless, conditions will remain hazardous for travel during the evening commute, so please use caution while driving on untreated roads!

This evenings latest high resolution visible satellite imagery, regional radar mosaic, and surface temperatures over the Northeast showing a wide variety of weather conditions

Thursday Into Friday

Conditions will start off rather cold on Thursday morning as an area of high pressure builds off to our west over the Ohio Valley. Temperatures will have likely dropped quite a few degrees below freezing during the overnight hours, so expect any puddles or standing water to have frozen over, making for another potentially slippery commute. Black ice may be rather prevalent over the area tomorrow morning as well, so please use caution! Regardless, the rest of the day looks rather calm as the area of high pressure over the Ohio Valley continues to build, leaving most of the Northeast rather sunny. Colder and drier air will be working its way down in the mid levels of the atmosphere from Canada, so we expect highs to generally stay in the middle to upper 20’s. Conditions will remain calm and cold through the evening hours as the area of high pressure continues to move over the Mid Atlantic. As it does so, conditions will become rather favorable for radiational cooling to set up over the Northeast, allowing for lows to drop into the middle teens and 20’s across much of the area.

Friday looks to be rather similar to Thursday, just with a chance of more clouds and significantly less windy. The Pacific jet stream will begin to go zonal over the entire country (west to east), which will signal the start of a warmer period, but also an unstable one. This west to east pattern will allow for multiple impulses of energy to quickly move from one coast to the other rather quickly, but a lack of anything to slow them down along the way will keep each disturbance weak and disorganized. One such disturbance looks to be over the northern Plains on Friday afternoon, which could cause some very light rain or snow to break out over northern portions of the New York metro area later in the day before quickly moving to the east. Major changes will be underway by Friday night, as strong low level flow begins to establish itself from the southwest, ushering in warmer mid level temperatures. This will allow for lows on Friday to mainly stay in the middle to upper 20’s, with some locations staying in the 30’s.

This afternoons NAM model showing significant warm air advection over the Northeast on Friday afternoon, leading to a change to warmer temperatures

Unsettled Conditions This Weekend

Starting on Friday, the subtropical jet stream will begin to expand over the Gulf of Mexico, creating abundant latent heat release which will eventually get caught up in the strong southwesterly flow over the eastern US. Our next system will begin to take shape over the southern Plains on Saturday morning as moisture-rich air runs into cooler mid level temperatures, sparking a large area of precipitation. The zonal jet streak will still be present over the northern tier of the country, and this will only work to enhance precipitation growth and intensity over the south. Snow will be possible over portions of the Mid West through the Ohio Valley where the colder air can hang on longer, as high pressure dives into the central Plains states. Mid level ridging over the western Atlantic will only help to enhance the northward transport of moisture into the Northeast on Sunday morning as light to moderate rain begins to break out. Rain looks to last pretty much all day on Sunday, likely making the day a washout. Due to the progressive nature of this system, flooding does not look all that likely in the Northeast, however there still may be some heavy downpours as precipitable water amounts will be quite high for this time of year. Temperatures this weekend will also be quite anomalous, with highs likely getting into the 40’s and lower 50’s across much of the Mid Atlantic and Northeast.

Another wave may develop along a stalled frontal boundary to our west on Monday, leaving us with another threat at some moderate rain to start the work week. At this time, it appears that the threat for substantial snowfall from either system is rather low, but we will continue to monitor these systems as they draw closer!

This afternoons NAM model showing an impressive moisture feed setting up directly from the Gulf of Mexico

Have a great evening!

Steve Copertino

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