Steven Copertino

Weekend of Unsettled Conditions and Temperature Swings, Potential Cool Shot Next Week?

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Good Evening! 

Today has has been a rather decent end to the work week with above-normal temperatures and light winds from the east. A warm front moved through the region the other night and introduced much warmer temperatures and higher dewpoints across much of the Northeast. This increased moisture from the southwesterly flow also allowed for more clouds to develop as well, but this did not stop highs from reaching into the middle 60’s to middle 70’s, which is a good deal above normal for this time of year. However, changes are on the way this evening, with a cold front currently located moving through central Pennsylvania. While this cold front isn’t all that strong, it will be strong enough to drop temperatures later tonight as well as knock dew points down to more seasonable levels. Additional, high pressure will begin to build in behind this front, so this will set up a strong enough pressure-gradient to create some gusty winds in the 15-25 mph range late tonight and into early tomorrow morning. Temperatures should be able to drop into the lower to middle 40’s tonight, with locations more north and west of the city likely seeing lows in the middle to upper 30’s. while conditions would otherwise be quite favorable for radiational cooling and some frost, the potential for gusty winds across the area should limit both of those possibilities.

High resolution visible satellite imagery, surface observations, and regional radar mosaic (Courtesy of SimuAWIPS)

High resolution visible satellite imagery, surface observations, and regional radar mosaic (Courtesy of SimuAWIPS)

Saturday Into Sunday

Saturday should have a nice and crisp start to the day as the northwesterly flow from Canada kicks in over the Northeast with winds still gusting in the 15-20 mph range. High pressure will also continue to build over the area, which should help promote sunnier skies and calm weather during the first half of the day. As we move deeper into the day tomorrow, winds should gradually shift from northerly to easterly, which will signify the start of another warm from passage. Dewpoints will also begin to increase once again as marine air works its way west, which will also work to gradually increase clouds by the late afternoon hours. Highs will likely reach the middle to upper 50’s tomorrow, with some locations closer to the coast likely making it to the 60’s. As the warm front begins to work its way inland, some weak low level energy will be present, which may help to increase the threat of showers across the area. These conditions should last into the evening hours, with lows staying in the middle to upper 40’s-some locations closer to the coast will likely be stuck in the 50’s due to warmer marine air aloft.

Sunday should start off quite the opposite of how Saturday did, as an approaching mid level warm front will increase moisture and available lift. This will cause an increased threat for showers, especially across western New Jersey and portions of eastern Pennsylvania. The overall progression of the front is still in question, but Sunday certainly looks to be quite a few degrees warmer than the previous day, with highs making it up into the middle to upper 60’s, which will be above average once again despite the increased threat for showers and cloudiness. Lows will likely stay rather mild with temperatures dipping into the upper 40’s and lower 50’s.

This afternoons high resolution NAM model showing showers located over eastern PA and potions of NJ early Sunday morning

This afternoons high resolution NAM model showing showers located over eastern PA and potions of NJ early Sunday morning

A Look Into Next Week

By Monday, most of the Northeast should be well within the warm sector of the warm front, so expect warmer temperatures once again for the region, with 70’s quite likely-which will be a good deal above normal. Later in the day on Monday, an area of energy associated with a trough in southern Canada will be moving our area and will enhance southwesterly flow ahead of an approaching cold front. While this front will be weakening quite a bit from when it moves on in from the Ohio Valley, it certainly will have the potential to bring some showers later in the day as it approaches the coast. As the front pushes offshore by Monday evening, dry northwesterly winds will once again take over and provide a chillier airmass for the entire Northeast as Canadian high pressure builds in.

Conditions will then turn rather zonal from Tuesday until Thursday, with the jetstream generally blowing from west to east across the nation. This should allow the area of high pressure to stick around for a majority of the week, with mainly dry conditions expected over the region. Temperatures should generally stay near-normal during this period as cooler air from Canada bleeds south ever-so-slightly. Thursday may have a shot at rather cold lows as an approaching trough from Canada starts to move southward.

By Friday, things begin to get interesting as the models have been keying in on a deep trough moving in over the East and bringing a nice shot of unseasonably cold weather. Western ridging will improve just enough to allow the cold that has been trapped to our north to quickly come down south by Friday night in the form of an arctic front, which will likely drop lows below freezing across the entire zone, with some locations well off to the north and west seeing lows in the 20’s and even teens. Depending on how much low level moisture hangs around before this Arctic front moves through, some locations could actually see flurries or snow showers, but this is something that we will have to revisit next week. Regardless, the chances of a widespread freeze are increasing for the later part of next week.

This afternoons ECMWF model showing a sharp shot of cooler temperatures over the Northeast by the end of next week

This afternoons ECMWF model showing a sharp shot of cooler temperatures over the Northeast by the end of next week

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Have a great night!

Steve Copertino

Steven Copertino

Cool Conditions Give Way To Warmer Weekend Weather

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Good Evening! 

We had quite the chilly start to the day today after the area experienced near ideal conditions for radiational cooling that allowed temperatures to drop well into the 30’s across much of the area. Some frost was reported in locations that saw lows drop into the low 30’s which lasted until just before the morning commute-a sign that we’re quickly approaching the start of the winter season. As the rest of the day went on, the area of high pressure that had been in control over the past three days finally began to lift out of the Northeast. This caused low level warm air to funnel in behind the high, which brought in not only numerous clouds over the area, but also some mid level moisture surging northward that helped to create some spotty showers over the western areas of the Northeast. The combination of thick cloud cover and increased shower activity allowed temperatures to stay relatively cool today, with most stations reporting mid day highs in the lower 50’s to middle 60’s. The large temperatures dependency over portions of southern New Jersey is due to an approaching surface warm front that will likely be working over the area later this evening and into tomorrow.

Given then increasing low level moisture and cool air trapped just below the warmer layer aloft, there may be some patchy areas of fog developing late tonight which could possibly last into the early morning hours. Some light showers may also be possible highly dependent on the exact timing of the warm front. If the front is quick to overspread the area, then showers may become more likely, but if the front crashes into the cooler/more dense air over Pennsylvania, then showers will become much less likely this evening and into the early morning hours. Regardless, expect mostly cloudy conditions continuing into sunset, with lows tonight topping off around the middle 50’s for most of the area. again, depending on the progression of the front, areas west of the city may see cooler temperatures if the front begins to slow down over Pennsylvania.

Surface pressures, surface observations, and surface fronts, showing a rather large temperature differential as the high pressure system in purple lifts out

Surface pressures, surface observations, and surface fronts, showing a rather large temperature differential as the high pressure system in purple lifts out

Thursday Into the Weekend

Thursday morning will likely start off cool for most of the area, but with increased mid level riding beginning to develop overhead, any fog or leftover stratus clouds should quickly dissipate as more stable air gives way to clear skies by the mid morning hours. With clearing skies and warmer mid level temperatures, highs tomorrow will likely be a good deal warmer than they were today, with highs likely ranging in the upper 60’s to lower 70’s. Tomorrow should also remain free of precipitation throughout the entire day, so expect calm and mild conditions to last into the evening hours where lows should only be able to drop into the lower to middle 50’s across much of the area.

As we work our way to the end of the work week on Friday, relatively clear conditions are expected during the day, and with an enhanced southwesterly flow in the low level, we expect the day to get a head start on warmer temperatures than Thursday. Low level flow will likely be maximized ahead of another approaching cold front that should be located over western portions of Pennsylvania by Friday afternoon, so the day should have a nice and warm feel to it, with highs likely reaching into the 70’s across much of the area. Locations closer to the ocean like Long Island and coastal Connecticut may have to deal with some cooler offshore winds that may bring highs down a bit, but overall Friday will likely be the nicest day of the week for any outdoor activities. Later in the day, the cold front should begin to pass over the region, with a chance at some scattered/isolated showers with the front. Most of the energy associated with this front will be disjointed and weak, so widespread rainfall is not likely at this time. High pressure should begin to build back in during the night on Friday, so expect conditions to be cooler behind the front with lows dropping into the middle to upper 40’s.

This afternoons GFS model showing above-average temperatures across the area over the next 48 hours

This afternoons GFS model showing above-average temperatures across the area over the next 48 hours

Saturday will likely start off rather calm and cool, with winds coming mainly from the cooler Atlantic. These cooler winds will likely run into some residual moisture from the weak cold front, so it will not be out of the realm of possibilities for some broken/scattered clouds to make an appearance during the day. Despite some cloudier conditions, Saturday will likely remain dry, with highs likely staying in the 50’s area-wide.

On Sunday, a warm front looks to march back over the region from the south, putting a cap on the short cool period. This front looks to come through during the very early morning hours, and could carry some lift with it, so we may have to watch for spotty showers to develop as the warm front takes over. Sunday may feature some partly cloudy conditions, but this will ultimately depend on just how strong the warm front is, in addition to how far inland it can advance. Overall, expect highs to rise into the lower to middle 60’s during the day, with only a slight chance of rain at this time.

An early look into next week shows that we may have to watch an area of low pressure and associated mid level trough for the next measurable rain potential across the east. Additionally, heights will likely rise considerably once again along the coast, which should elevate temperatures into the 70’s-with a shot at middle 70’s at some location early in the week.

This afternoons ECMWF model showing the tail end of an area of ridging parked over the east for this weekend, with slightly above-normal conditions expected.

This afternoons ECMWF model showing the tail end of an area of ridging parked over the east for this weekend, with slightly above-normal conditions expected.

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Have a great night!

Steve Copertino

John Homenuk

AM Update: Warmth returns to east, but for how long?

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Good morning and Happy Wednesday to you all. There is something oddly special about the first day of November in the meteorological community. It’s not a holiday, it’s not the start of any official season. But it has significance for many who forecast or follow the weather – it’s the beginning of “winter season” per se, where the forecasts for the weeks and months ahead start to have more significant implications on what we can expect during winter.

As we move into November this year, the weather pattern will be dominated by a large -EPO ridge, developing in the Pacific Ocean as we speak. We discussed yesterday in detail how these EPO ridges can impact the weather pattern throughout the hemisphere. In this case, the large ridge in the Northern Pacific Ocean will act to dislodge colder than normal air from the arctic regions into British Columbia, and eventually the Northwestern United States as well.

Read more

Steven Copertino

Cooler Conditions Hanging On, Changes Coming This Week

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Good Evening! 

The storm that bombarded portions of the Northeast over the past day is quickly moving out over eastern Canada, but the storm certainly left its mark. Most of the Northeast saw heavy rainfall totals in the range of about 2-5″, but the main event from this system were the winds that roared in overnight last night. As the low pressure area rapidly deepened and moved ashore over NJ and eventually progressed into New York state, it carried a large an impressive area of high winds just above the surface over portions of Long Island, Connecticut, Rhode Island, Massachusetts, Vermont, and Maine. As the storm began to fill in with warmer air and weaken, these winds just above the surface were able to rapidly crash down to the ground and cause an impressive amount of tree damage. Hundreds of thousands of folks are still without power in many of the states above, with over 400,000 customers without power in Maine alone. While these winds were rather impressive, the main story west of the immediate area of low pressure were the torrential rains that fell. Deep tropical moisture streamed northward into the Mid Atlantic and Northeast states, and when this moisture was met with the strong dynamics aloft, heavy rain became focused over New Jersey and portions of New York for several hours. Some locations were able to rack up rain totals in the 4-5″ range when all was said and done, with some minor street and river flooding noted. As we stated last week, the reason that these rains were not a bigger story was because an existing minimal drought muted out the overall impacts.

Sunday nights radar near the peak of the coastal storm that brought heavy rains and high winds over the region

As day broke today, a strong westerly jet associated with the backside of the low pressure system was working its way over the Northeast. Due to more mixing of dry air in the atmosphere, this low level jet was able to bring gusts down to the surface in the range of 30-40 mph, which brought some additional tree damage to the region. It also made for a cooler and more classic fall day as cooler Canadian air was briefly tapped. With partly sunny skies and cooler temperatures aloft, highs were able to make it into the middle 50’s across much of the region, but cooler conditions to the north and west kept highs down in the low to upper 40’s-with some stations in New York state even reporting snow showers! As the massive low pressure system continues to pull away this evening, wind have shifted from northwest to southwest as high pressure begins to build in from the south. As the winds shift, the gusty 20-30 mph conditions will begin to die down as the pressure gradient from the two opposing systems weakens with time. Given the clear skies and low humidity, conditions will be marginally supportive for radiational cooling to occur tonight which should knock temperatures down into the upper 30’s and lower 40’s across the area.

High resolution visible satellite imagery and surface observations over the northeast showing cooling and windy conditions

High resolution visible satellite imagery and surface observations over the northeast showing cooling and windy conditions

Tuesday and Beyond

The area of high pressure just south of the area will continue to build north throughout the day tomorrow, which will allow for dry conditions and generally clear skies. Highs will likely be limited to the middle to upper 50’s  during the day tomorrow despite winds coming from southwest winds at the surface, but cooler Canadian air continues to work in at the lower levels of the atmosphere. Winds will also likely die down completely by tomorrow afternoon, so as we work our way into the evening hours, we should see ideal conditions for radiational cooling to take place over the entire area. Low level temperatures will likely be below freezing already, so expect lows to drop into mid to upper 30’s, with some of the more interior locations possibly even dropping below-freezing and into the upper 20’s. With little to no winds, frost will be increasingly likely the farther away from the coast you move.

By Wednesday some changes will be in the works as a large area of low pressure begins to move towards the Great Lakes region. As this low heads northeast, it will bring a surge of warmer air along a warm front over the area, which should work to bring highs back into the upper 60’s and lower 70’s once again. Given the breadth of this system, we will likely be in between the cold front and warm front until Friday, when the cold front will finally pass, bringing a marginal chance of showers during the afternoon hours. Highs will likely remain in the upper 60’s to lower 70’s through this period, before the cold front knocks temperatures back down to more seasonable levels.

By this weekend temperatures should once again cool down with northwesterly flow returning from Canada, but we may have to watch for a threat of showers once again later in the weekend as a potential wave of low pressure rides north along a stalled cold front over the area. There is still considerable uncertainty with this solution and we’ll have more details by Wednesday as the model guidance converges on a more clear solution.

Snapshot from the 12z ECMWF model showing slightly above normal temperatures during next weekend with the return of higher heights in the east

Snapshot from the 12z ECMWF model showing slightly above normal temperatures during next weekend with the return of higher heights in the east

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 night!

Steve Copertino