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Steven Copertino

Mild and Unsettled Pattern Begins to Take Shape

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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

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!

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

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

Have a great night! 

Steven Copertino

Steven Copertino

Warmer Conditions Finally Take Hold, Watching This Weekend

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Good Evening! 

Today has been quite the interesting day, as we finally saw high temperatures lift above freezing for the first time in almost two weeks for some locations! Many states across the Eastern third of the country saw their coldest first week of January on record, which is a fitting way to bookend this intense Arctic Outbreak that will likely be remembered for years to come. Although some locations to the south and east of the immediate NYC area saw a return to above-freezing, many locations did not and were once again stuck in the middle to upper 20’s. This combinations led to problems, as a weak mid level disturbance moved in from the Ohio Valley this afternoon and brought a mixed bag of precipitation for the majority of the Mid Atlantic and some Northeastern states. Despite having mid level temperatures just slightly above freezing in the lowest 3,000-4000 feet of the atmosphere, low level temperatures were cold enough and were accompanied by enough dry air to have precipitation start off as a mix of freezing rain and sleet for locations mainly to the north of Philadelphia. As this system quickly headed towards the coast during the late afternoon, we were able to see a change to mainly sleet and snow as mid levels once again cooled enough to end the freezing rain threat. Farther south, the freezing rain threat has stuck around longer due to more stubborn mid level warm air and higher temperatures near the surface. No major ice accumulations have been recorded as of this evening, but it would appear that at least some roads have become slick over the past few hours over southern NJ, southeast PA, and portions of MD/DE.

These slippery conditions accompanied by lingering light freezing rain should continue until around 11pm-1am before completely shutting down as dry air begins to take over the mid levels from northwest to southeast. While precipitation may not be all that heavy, freezing rain accumulates the most when rates are light, so please use caution when driving this  evening, especially on back-roads and roads that usually are not treated. Otherwise, we should see continued gradual clearing through the overnight hours, with temperatures getting into the lower to upper 20’s over the majority of the Northeast.

This evenings regional radar mosaic, surface observations, and RTMA 2m temperatures showing some light rain, snow, and freezing rain over the Mid Atlantic states.

This evenings regional radar mosaic, surface observations, and RTMA 2m temperatures showing some light rain, snow, and freezing rain over the Mid Atlantic states.

Tuesday Into Thursday 

Any mid to upper level clouds associated with tonight’s system should be out of the region and well off the coast in time for the morning commute on Tuesday. Tomorrow will likely start off quite cool, but clear for the entire area. Winds should generally be from the west for the vast majority of the day tomorrow, with temperatures likely getting into the middle to upper 30’s across much of the area tomorrow, with only locations north of southern New England staying below freezing. Calm conditions can be expected tomorrow as a surface high pressure system builds in over the Northeast by tomorrow evening. Conditions will be quite calm and just right for some good radiational cooling to take place tomorrow night, which should bring lows down into the lower to middle 20’s right around the NYC metro area, with teens likely to the north and west.

Wednesday should see much of the same, with a high pressure system remaining in control of the weather for the day. Mid level temperatures will begin to rise from the southwest during the afternoon hours, and with relatively clear skies, we should see highs mainly in the middle to upper 30’s, with some locations to the south and east likely getting into the 40’s. Clouds should begin to increase during the late evening hours and into the night as a mid level warm front will begin to lift over the region, bringing warmer temperatures in overnight. Lows will likely range in the middle to upper 30’s, with some locations to the north and west stuck in the low 30’s.

Thursday will likely be one of the more noticeably warmer days as low to mid level flow continues to increase and draw up warmer temperatures in the process. A growing system located in the Plains that will impact our area this weekend should provide some moisture early in the morning hours and possibly into the early afternoon, but these should generally be light in nature as the bulk of the lift associated with the system remains a great distance away. High temperatures on Thursday are going to be tricky, but the increased humidity and mid level temperatures should yield highs in the lower to middle 40’s across much of the Northeast, with some locations likely to hit that 50-degree mark . Any meaningful precipitation looks to wait until the early morning hours of Friday to move in, so expect relatively dry conditions until that time.

18z NAM models evolution of the surface temperatures over the Northeast, showing a change to a warmer couple of days.

18z NAM models evolution of the surface temperatures over the Northeast, showing a change to a warmer couple of days.

Plain Rain Or A Mix For The Weekend? 

Finally, a large area of energy will be over the southern Plains states by Friday morning, and this will help to pump copious amounts of low level moisture into the East during the day. As of right now, it appears that we may see one heavy burst of rain start to move from the south and over the Mid Atlantic and Northeast early Friday morning and into the afternoon hours. Rain intensity may dwindle a bit in the late afternoon hours and into the evening, but at least some showers are likely during this time. The next batch of steady rain looks to occur right around Saturday morning as the mid level energy begins to strengthen and take on more of a negative tilt over the central US. This kind of setup promotes the development of a primary low pressure system over the Ohio Valley, with moderate precip extending from Illinois from Boston. This will be a large system in nature, so the impacts will already be large, however this afternoons European model has shown a more interesting solution as the surface low pressure system bumps into a strong area of Arctic high pressure located over southern Canada. Such a solution would create the threat for snow/sleet/freezing rain as the more dense cold air runs into the strong warm air advection from the south.

As of this evening, it appears that portions of New England would be at greatest risk from any significant frozen precipitation, but this is still five days out at this moment, and these situations usually continue to change up until the event is occurring. We will be closely monitoring the potential for heavy rain and possibly some frozen precipitation this weekend and will provide numerous updates over the next couple of days!

This afternoons ECMWF model showing a large winter storm centered over the Ohio Valley bringing a wide range of possible impacts.

This afternoons ECMWF model showing a large winter storm centered over the Ohio Valley bringing a wide range of possible impacts.

Have a great evening!

Steve Copertino 

Steven Copertino

Warmer Conditions Arrive Tuesday, How Does Thanksgiving Day Look?

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Good Evening! 

Today was another cold and breezy day across much of the Northeast, as the strong low pressure area that affected our region earlier this weekend continues to move off to the east and over the martime regions of Canada. The interaction between this low pressure system and a high pressure system to our south has created a steep pressure gradient which has been the source for these gusty conditions over the past day or so. Strong northwesterly flow in the mid levels of the atmosphere has also contributed to colder air aloft blowing over the Great Lakes, which has produced some lake effect snow showers that have mainly been focused across far northern New York state and Pennsylvania. However, some of these “lake-effect” snow showers moved over portions of the New York metro area, producing some of the first flakes of the year for most locations. While surface temperatures over the area were not at or below freezing, cold mid level temperatures allowed precipitation to remain mostly frozen, with ice pellets also being recorded in northern New Jersey. While these snow showers did catch some people by surprise, they weren’t anything more than “mood flakes”, or just some light flurries that do not stick to any surfaces-allowing travel to proceed as usual.

The rest of our Monday was rather chilly, with a mix of clouds and sun keeping our temperatures limited to the lower to middle 40’s across much of the area. Winds have really begun to weaken over the entire northeast as the pressure gradient between the two surface systems really diminishes with time as the systems grow further apart. As we head into tonight, the area of high pressure located over eastern Carolina will remain in control of our weather, bringing lighter winds out of the southwest and clearer skies. Lows tonight will likely have a range to them, with the far northwestern locations likely dropping below freezing and into the upper 20s, while locations near New York City willy likely get down into the lower to middle 30’s.

RTMA Analysis of the current temepratures over the Northeast, with surface observations finally showing a change from the gusty NW winds we have been seeing for the past day or so (Credit: Simuawips)

RTMA Analysis of the current temperatures over the Northeast, with surface observations finally showing a change from the gusty NW winds we have been seeing for the past day or so (Credit: Simuawips)

Tuesday morning will likely start off rather cool, but mostly sunny as the area of high pressure that we’ve been following moves offshore and into the western Atlantic by the morning commute. This will mean that as the day goes on, warmer mid level air from the southwest will move into the Northeast, allowing temperatures to moderate quite a bit when compared to today. Additionally, a vigorous area of mid level energy will be diving down from Canada by the afternoon hours of tomorrow, which will be accompanied by a moisture-starved area of low pressure at the surface. As this system heads east with time, it will increase the strength of the southwesterly flow, leading to an increase in winds across much of the Mid Atlantic and Northeast by the late afternoon hours. The relatively clear and conditions and warmer mid level temperatures from the south will allow highs to climb into the lower to middle 50’s tomorrow, with the warmest readings likely just inland from the coast.

As we progress into Tuesday evening, we should see moisture being to develop in the southern states as another messy batch of disorganized mid level energy moves in behind the first system in the Great Lakes. As this takes place, a cold front associated with the system in the Great Lakes region will continue to move east and into the Northeast by the end of the day. This front will remain relatively dry as it moves over the Northeast due to the system to the south and west of it stealing most of the moisture deep in the Gulf of Mexico.

Things may become a little more interesting during the very early morning hours on Wednesday when the upper level jet streak from the Great Lakes system begins to interact with the energy over the south and moisture begins to flow more northerly. The question with this time period is just how much will the precip expand and move west as the new low develops to the south? Today’s model guidance diverges a bit on the extent of the precipitation shield on Wednesday, but as of right now it looks like the immediate coasts of NJ and LI could see some steadier rain, with showers possible further North and West. Since these two systems will remain mostly independent from one another, this is very unlikely to be a big deal, but even slightly more interaction with these systems and a healthier upper level jet streak could promote the development of precipitation further inland, and this will have to be monitored. Otherwise, highs on Wednesday will likely remain in the lower to middle 50’s despite the incoming cold front. The front should clear the area by late Wednesday afternoon, with any residual shower activity quickly leaving the scene as well. Wednesday evening should be a cold one, with lows likely dropping into the middle to upper 20, with warmer readings near the coast.

18z NAM 500mb loop showing the initial energy with Wednesdays cold front quickly moving east while more energy drops down into the Gulf of Mexico and becomes "stuck"

18z NAM 500mb loop showing the initial energy with Wednesdays cold front quickly moving east while more energy drops down into the Gulf of Mexico and becomes “stuck”

Thanksgiving Day and Beyond

A colder airmass from Canada will be in place over the Northeast behind Wednesdays cold front, which should cause the day to start off rather cold in the upper 20’s and lower 30’s. Left over dry air in the wake of the cold front should allow mostly sunny conditions to take over on Thanksgiving day. A colder airmass, clear skies, and calm winds should only allow temperatures to rise into the upper 30’s and lower 40’s across much of the New York metro area, with warmer readings located over portions of Long Island. From a historical standpoint, this Thanksgiving should be a rather cold one, as highs will likely come in 10-15 degrees below-normal! Conditions during the remainder of the day should be quite pleasant as a weak area of high pressure moves in from the west. This area of high pressure will cause winds to shift back to a more southeasterly component by the evening, which will signal the arrival of another warmer mid level airmass. Lows during the evening hours should drop into the middle to upper 20’s, with some warmer temperatures likely across locations closer to the coast.

Calm and cool conditions are expected through Saturday afternoon, before another strong area of low pressure over southern Canada drags a cold front through the region early on Sunday. As of right now, this cold front also looks to be moisture-starved, but the big deal with this system will be the temperatures, not the precipitation. With a large area of high pressure over the western Unites States, this cold front will have the potential to dump some impressive cold over the east, which could drop the area down into the lower 30’s and upper 20’s for highs. Though its just under a week out right now, this cold shot does look to be on the quick-hitting side, as the upper level trough associated with the cold air will quickly move out by the middle of next week.

This afternoons ECMWF model showing the potential for a potent, but quick-hitting cold shot by the end of next weekend.

This afternoons ECMWF model showing the potential for a potent, but quick-hitting cold shot by the end of next weekend.

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Have a great night!

Steve Copertino 

Steven Copertino

Public Analysis: Oppressive Heat and Humidity, Strong Thunderstorm Threat Thursday and Friday

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Good Evening! 

As we stated earlier this week, conditions were once again going to become unstable as a deep tropical airmass works its way over the region over the next few days. This was quite noticeable today as dew points rose into the uncomfortable (66-70) and oppressive (71-75) degree ranges! Coupled with highs in the mid to upper 80’s, heat indices were able to climb into the middle 90’s in some locations, promoting the issuance of a Heat Advisory for counties in Pennsylvania, New Jersey, and New York-for now. A Heat Advisory is issued when the combination of heat and humidity is expected to make it feel like it is 95 to 99 degrees for two or more consecutive days, or 100 to 104 degrees for any length of time.-NWS 

With this increased instability and plentiful moisture trapped in the atmosphere, all we needed today was a little daytime heating to really destabilize the atmosphere. The first in a series of quick-moving shortwaves in a general west to east flow was today’s trigger mechanism that set off numerous strong to severe thunderstorms over portions of southern New England, and even portions of Connecticut. These storms were mainly very heavy rain producers as the atmosphere did not have enough energy in place to keep the significant amount of moisture lofted within the low to mid levels of the atmosphere. As the updrafts that held all of this moisture began to collapse, they created very high rain rates, with some nearing close to 2″/hr! As the more robust updrafts quickly collapsed  and the rain cooled air rushed to the ground, this created localized instances of wet microbursts, which were the cause of some tree damage in Connecticut.

As the forcing mechanism for this afternoon convective outbreak begins to quickly move off to our east, showers and thunderstorms should gradually sink further south and east with time. As they do so, they will also encounter a slightly less favorable environment needed to sustain themselves, however it would not be out of the realm of possibilities that a few more short-lived cells go up near sunset, capable of small hail, heavy downpours, and occasional lightning.

The rest of the evening will likely remain quite muggy, as the tropical-like airmass remains locked in place due to rather stout low level winds from the west/southwest. Lows this evening will be lucky to get down into the lower 70’s, so expect a rather muggy night ahead with a slight chance of some showers in the very early morning hours.

This evenings latest regional radar mosaic, regional surface observations, and high resolution visible satellite imagery, showing left-over showers and thunderstorms over the area gradually moving to the east/southeast (Courtesy of Simuawips.com)

This evenings latest regional radar mosaic, regional surface observations, and high resolution visible satellite imagery, showing left-over showers and thunderstorms over the area gradually moving to the east/southeast (Courtesy of Simuawips.com)

Thursday Into Friday 

Thursday is likely to start off with a few broken or scattered clouds, with some “hazy” conditions likely as well. As the daytime heating gets off to a rather quick start tomorrow morning, temperatures will quickly shoot into the upper 80’s to lower 90’s once again, and when factoring in the very high dewpoints, conditions will become quite miserable in some locations. Heat indices may swell into the upper 90’s and even into the lower 100’s during the peak heating hours of the afternoon! As another in a series of mid level disturbances rushes over from the Great Lakes region, mid level shear ahead of this wave will begin to increase in earnest, creating a conducive initial environment for afternoon thunderstorms to fire in over the area.

While the initial setup of parameters over the area will be primed and ready for thunderstorm development by the afternoon, the main question is regarding the timing and location of the mid level disturbance that would be able to trigger thunderstorm development. What may wind up happening is that the initial thunderstorms may fire over portions of southern New England (like they have many times this year before) and then begin to sag southward along a frontal boundary to our north. The problem with this is that by the time that the showers and thunderstorms begin to propagate to the south, the best parameters over our area will begin to fade. This would mean that as any storms move south, they would gradually weaken with time, which would mitigate the overall severe threat. Regardless, the setup tomorrow looks to support at least torrential downpours, frequent lightning, gusty winds-with the potential for more damaging wind gusts and hail in the strongest cells.

This afternoons RPM model showing the progression of the frontal boundary tomorrow morning and through the afternoon hours (Courtesy of WSI)

On Friday, a broad area of low pressure will begin to stretch over into our area, likely starting the day off with rather thick cloud cover and cooler temperatures. Though the model diverge on this quite significantly, there does appear to be a rather good chance that a frontal boundary will be stalled somewhere along the Metro area, or just to our north-which will dictate much of Friday’s weather. This stalled frontal boundary will act as a near-perfect source for lift, as deep low-level flow ushers in PWATS of around 2.25″-2.5″. Additionally, CAPE will also become quite plentiful due to this tropical airmass, and this instability will be met with increasing low to mid-level shear from the stalled frontal boundary. Due to the amount of dynamics riding on this frontal boundary, even a small deviation would be able to turn a potential severe weather event into a heavy rain/flooding threat with very little notice-or vice versa.

The first threat of thunderstorm development will likely be in the early afternoon hours, with the second, and more impactful taking place towards the late afternoon/early evening hours. Regardless, all modes of severe weather will be possible on Friday, with damaging wind gusts, large hail, and even an isolated tornado being quite possible. Very heavy rain will also be a large concern as the atmosphere will be “water logged”-for the lack of a better term. Both time frames will likely need adjusting over the next 36 hours or so, so make to stay up to date with our daily updates.

This afternoons European model, showing very high precipitable water vales (PWATS), modest mid level winds, and an approaching mid level trough to help kick off a two-pronged event on Friday with severe weather and localized flooding possible.

This afternoons European model, showing very high precipitable water vales (PWATS), modest mid level winds, and an approaching mid level trough to help kick off a two-pronged event on Friday with severe weather and localized flooding possible.

This Weekend and Beyond

Improving conditions are looking likely heading into the weekend, with some clouds or showers may linger into Saturday morning as shortwave trough and frontal boundary exits the region. Otherwise high pressure from Ohio Valley builds into region with a drier northwesterly flow, for rest of the weekend. It will be more pleasant, with lower humidity, more sunshine and high temperatures in the lower to middle 80s. Latest GFS and ECMWF models are keeping the next chance of more scattered showers and thunderstorms with cold front and upper-level trough coming from Great Lakes, away until Monday or Tuesday. Temperatures will likely be at seasonable levels through early next week.

For more information and posts like this one, make sure you sign up for Premium Forecasts — where multiple detailed articles, videos, and interactives are posted each day. Also, come interact with our staff and many other weather enthusiasts at 33andrain.com!

Have a great evening!

Steve Copertino & John Homenuk