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Southeast Ridge Builds, But Not For Long…

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!

 

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First snowfall of the season for the Northeast this weekend

About two weeks ago, it became clear that the weather pattern was set to undergo a significant shift. After many weeks of warmth, a reshuffle was underway in the Pacific Ocean, and the downstream effects of this would lead to colder air with a more wintry pattern in the North-Central and Northeast United States. Two weeks and many forecasts later, here we are. The first snowfall of the winter is set to fall in the Northeast states this weekend, including the metropolitan areas of Philadelphia, New York City, Hartford and Boston.

Forecast models, for all of their benefits, were not keen to signal the potential for snow this weekend until about 24 hours ago. Forecasters had been monitoring this potential quite closely, but a snowfall of any significance always seemed like a long shot in the Northeast States. On Thursday morning, however, it became clear that a significant trend was underway, and forecast model guidance quickly began changing the evolution of the storm system during the weekend ahead.

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Isolated Strong T-Storms Possible for the Northeast Late Today

Good morning and happy Saturday! Good news! Today is now looking pretty good overall for any outdoor plans. Showers and thunderstorms that were associated with a warm front and a mid-level shortwave from overnight are already moving offshore early this morning. Behind it, clouds will clear for more sunshine for the rest of the morning. Then partly sunny skies are expected for most of the afternoon. It will be warm and humid with high temperatures in upper 70s to lower 80s and more southerly winds today. Temperatures may be a little cooler near the shore.

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Saturday’s Rain Threat Gives Way To More Variable Conditions Next Week

Good evening! 

Today started off rather pleasant with clear skies, light winds, and rather moderate temperatures. However, as the broad area of high pressure that remained in control for the past few days began to gradually shift offshore and into the west Atlantic, a broad mid level trough began to edge into the Northeast this afternoon. As this trough gradually progressed east, the airmass change could be felt as dewpoints rose into the middle to upper 60’s across the area, which made for a much more “muggy” feel to the afternoon than the past couple of days. On the lee side of this disturbance, mid levels winds are coming from the southwest, which is acting to advect a good deal of moisture from the south. This moisture has continued to overspread the Northeast this afternoon as a weak warm front moved from north to south across the metro area. With some weak ascent and forcing associated with the front, some showers and thunderstorms have popped up over portions of the Mid Atlantic and portions of Pennsylvania, where severe parameters are supportive of locally severe weather. In fact, an isolated supercell has developed over northern Virginia this past hour, and may eventually reach the DC metro area.

Closer to the NYC metro, the atmosphere remains much more stable than our surroundings (as has been the case this entire year so far). Instead of thunderstorms developing this afternoon, we’ve seen widespread cloudiness take over. Some residual showers from dissipating thunderstorms over Pennsylvania are currently making their way into western New Jersey, but no hazardous weather is expected as any showers/thunderstorms encounter the stable airmass overhead.

As the evening marches on, more leftover showers may entire from the west and bring some brief heavy downpours and occasional lightning, but generally cloudy conditions are likely for the remainder of the night. The combination of the higher dewpoints, southerly winds behind the warm front, and cloudy conditions will almost ensure that raditional cooling will be non-existent this evening. Lows should unanimously mild, reaching the middle 60’s to lower 70’s across the region.

This evenings latest high resolution GOES-16 visible satellite imagery, regional radar mosaic, surface observations, and frontal postilions-showing showers and thunderstorms mainly concentrated to the west of the area this evening (Courtesy of Simuawips)

This evenings latest high resolution GOES-16 visible satellite imagery, regional radar mosaic, surface observations, and frontal postilions-showing showers and thunderstorms mainly concentrated to the west of the area this evening (Courtesy of Simuawips)

Saturday Into Saturday 

Tomorrow morning will likely start off quite unsettled as the mid level warm front to our south and west begins to move over the area with deep tropical moisture entrenched within. Precipitable water values will also increase markedly, into the 1.5-2″ range, so any showers and thunderstorms that develop early Saturday morning have the potential to produce very heavy rainfall in a short period of time. Though, with weak mid level lapse rates, any updrafts that do go up tomorrow morning will be extremely short-lived, and will likely form and die over the same location. Later in the morning, the warm front should lift through the region, possibly clearing out any residual showers and weak thunderstorms out of the area, and allowing for a brief period of sun poking through the clouds. Depending on how much sun the area sees late tomorrow morning and early afternoon will determine just how much the area can destabilize, which will have implications on the rest of the day. Model guidance suggests that the western portion of the New York metro area does in fact clear out enough during the afternoon hours that instability on the order of around 1000-1500j/kg^2 develops. By this time, it appears likely that a mid level trough will begin to nose into the Northeast, with a favorable upper level jet streak also making an appearance.

The combination of these factors could possibly lead to the development of some scattered showers and thunderstorms-some of which may be strong to severe. As of this evening, it appears locations west of NYC will have the best potential to see any robust thunderstorms, with the main threats being gusty winds, sub-severe hail, frequent lightning, and very heavy rains. This activity will be highly dependent on the timing of the best forcing arriving from the west, as well as just how much we can clear up and destabilize tomorrow after the initial batch of rain in the morning. Overall, widespread severe thunderstorm development does not appear likely tomorrow.

As we head into the evening, any residual showers and thunderstorms should gradually head east and weaken as the frontal system associated with the mid level trough begins to push over and out of the area. Behind the front we should have a less humid airmass, but with the risk of cloud cover, temperatures are not that likely to fall all that much-with lows generally in the low to middle 60’s.

Sunday looks to be a huge improvement over today and Saturday, as the shortwave trough that moves through on Saturday heads to our east and begins to usher in a cold front. This cold front not only looks to clear out any substantial cloudiness that may linger over the area, but should also be quite efficient at greatly reducing dewpoints from the 70’s, to lower 60’s over the entire area. With sunny skies, light winds, and low humidity, Sunday will be near-perfect for any outdoor activities , though there may be a risk of rip-current’s along the coasts, so please make sure to monitor beach conditions if you are planning a beach day. Highs will likely be comfortable-with temperatures reaching into the upper 70’s to lower 80’s, and lows getting down to the low to middle 60’s.

This evenings RPM model showing the progression/development of showers and thunderstorms later this evening and into tomorrow afternoon, followed by an eventual clearing on Sunday (Courtesy of WSI)

This evenings RPM model showing the progression/development of showers and thunderstorms later this evening and into tomorrow afternoon, followed by an eventual clearing on Sunday (Courtesy of WSI)

Monday and Beyond 

Previous model guidance runs had Monday being the next potential period for heavy rain, but have since backed off this idea quite a bit. This is due in part to the models incorrectly handling a weak tropical system that has been tormenting forecasters for the better part of the last nine days or so. This low was originally forecast to interact with a stalled frontal boundary located to the south of the region on Monday, which would in turn spawn another wave of low pressure. The tropical low pressure system has once again failed to develop, and this had lead to some significant changes in the model guidance for next week. It now appears that the same frontal boundary will not be able to push as far north as previously thought, mainly due to a lack of a surge in precipitable water values/moisture associated with the tropical system. So in short, this means that any precipitation on Monday will likely be much more spotty in nature than previously thought, with very meager amounts of instability and lift to work with over our area. At this time, we would not be surprised at all if this rain threat continued to deteriorate over time and does not amount to much of anything north of the Mason-Dixon line.

Otherwise, it appears that the northern stream will remain quite active for this time of year and could potentially lead another disturbance down our way by the middle of next week, with moisture surging ahead of this disturbance as we have seen many times before. However, at this time it seems that these rain threats will be transient in nature, with ridges likely building in behind-leading to a brief period of calm weather before the next rain chance.

This afternoons European ensembles, showing another unsettled period shaping up next week, with a trough over the central part of the US, and a ridge positioned over the south. This would lead to multiple disturbances rolling over the ridge, and into the Northeast.

This afternoons European ensembles, showing another unsettled period shaping up next week, with a trough over the central part of the US, and a ridge positioned over the south. This would lead to multiple disturbances rolling over the ridge, and into the Northeast.

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Have a great evening!

Steve Copertino