Dry, warm, and mostly sunny with cool nights through Wednesday; breezier Thursday, major rainfall possible Friday to Saturday, then much cooler and mostly dry for a few days; warm up again afterward, but still with occasional cooldowns and rainfall chances to ease drought

Plain-language summary:

 

It will be warm but not hot, dry, and mostly sunny through Wednesday with light winds, low humidity, and cool nights. It will not be as warm or hot as expected several days ago. It will turn cloudier and breezier on Thursday before substantial rain is likely on Friday to possibly Saturday, though the exact timing and amount of rain is still uncertain. It will turn much cooler for next weekend into following Monday, but not as chilly as farther west, with drier weather but some clouds and scattered showers still being possible. It will warm up and stay dry for a few days afterward, but warm and dry weather is unlikely to be sustained for more than a few days at a time, with at least occasional cooler air masses and opportunities for rainfall likely to start easing the drought, though the weather pattern could favor warmer than average temperatures overall.

 

Meteorological discussion:

Dry, warm, and mostly sunny through Wednesday with cool nights 

 

After a cut-off upper-level low brought unseasonably chilly weather and more showers than expected on Friday and Saturday, a large Canadian surface high-pressure system, a familiar sight over the last month, has settled into the region, which will provide dry, sunny, and seasonably warm but not particularly hot weather through Wednesday. Isolated afternoon showers are possible in the higher terrain of southeastern Quebec and western Maine on Wednesday. Nights will be rather cool due to the dry air, clear skies, and lengthening nights, especially in the usual cold hollows away from urban areas. The warmup will not be as pronounced as models showed a few days ago due to the surface high-pressure system staying near or to the east of our region, which means that the winds will never turn southwesterly to westerly, which is necessary for the advection of hot air from the western and central U.S. into the currently still slightly cool air mass behind the big cooldown earlier in the week.

 

Source: TropicalTidbits

 

 

 

 

Breezier and cloudier Thursday, potential major rainfall Friday, much cooler and mostly dry next weekend

 

It also appears as if the upper-level ridging along the North American West Coast extending all the way into Alaska will be stronger and more persistent than originally expected. All-time September high temperature records could be broken in British Columbia and the Northwest U.S. Interestingly, it is too far west to register as a +PNA, with the PNA actually being slightly negative. At the same time, a downstream trough will deepen and become unseasonably strong for the beginning of September as it plows southeastward into the Great Lakes by Thursday, eventually closing off into a broad, closed upper-level low that meanders northeastward into Quebec and slowly weakens by next weekend. Also a bit surprisingly, the weather pattern is configured such that it does not really register as a -NAO or -AO, perhaps due to the lack of true high-latitude blocking despite the rather amplified weather pattern.

 

 

Source: TropicalTidbits

 

 

 

Source: Climate Prediction Center

 

 

Our region will initially be on the eastern side of the trough, leading to strengthening southerly flow which would bring modified marine air from the western Atlantic instead of true hot and humid air from the southern U.S. or Gulf of Mexico. It will also turn cloudier with some showers possible in the upslope areas in the southeastern slopes of the Adirondacks and Green and White Mountains. A cold front will first pass early Friday, bringing a period of showers and possibly scattered thunderstorms, though meager instability should prevent any storms from becoming too strong. Then, late Friday into possibly Saturday, a disturbance rotating around the Great Lakes cut-off low will spawn another low-pressure system closer to our region, strengthening and tapping Atlantic moisture to likely produce at least moderate rainfall for someone, perhaps the most widespread substantial rain in over a month. However, models disagree on the exact timing and strength of the system, and it is possible that it is too weak and far north to produce much rain for our region. That system will move to the northeast by Saturday night with even cooler air behind it, though the cold air will not be as pronounced as in the Midwest U.S. due to the trajectory of the cold air first going into the Midwest U.S. and then getting modified as it moves east and northeastward into our region, as opposed to coming directly from the north or northwest. That tends to happen a lot in the fall and early winter. It will also likely dry out as well, though perhaps with some clouds and scattered showers due to the cold air aloft triggering low-level instability, especially during the daytime.

 

Source: TropicalTidbits

 

 

Warming up again for following week, but likely not for very long, with at least occasional cooldowns and rainfall chances expected 

 

After next weekend, the closed upper-level low will push farther northeastward, allowing for a Canadian surface high-pressure system to move into the eastern U.S. on the following Monday, perhaps briefly turning the flow enough to the northwest for a more direct and therefore stronger cold shot. But shortly afterward, the surface high-pressure system will move to our southeast, allowing for several days of dry, mostly sunny weather with southwesterly flow and a warming trend for the following week. However, sustained warm and dry weather appears unlikely given the upper-level ridging in western North America is not likely to truly reverse (though occasional troughs are possible) and the mid-latitude jet stream strengthening and making its seasonal progression southward into our region. This would lead to at least occasional, if not frequent, cold fronts and opportunities for at least some rainfall, even if the tropical moisture for producing torrential rains is lacking. The tropical Atlantic is very quiet right now for being close to the climatological peak of the hurricane season, but even with any tropical storms or hurricanes that do develop in the long-range, the troughs, usually accompanied by strong westerlies aloft, moving into our region will likely make any tropical storms or hurricanes that turn northward to then turn eastward away from our region. Unlike many recent years, summer appears to have ended early around a week ago, not long after the incredible heat in mid-August. The drought will likely stabilize or ease a bit with the cooler weather and increased chances of rain; droughts typically do not last very long in our region. Still, models actually do show temperatures being above average in the net sum after next weekend with the West ridge/East trough easing at least somewhat, even if true summer heat and humidity is unlikely to return.

 

Source: TropicalTidbits

 

Showers and scattered thunderstorms with unimpressive rainfall today into Monday; cool and dry Tuesday through early Thursday; cool and showery late Thursday to Saturday; dry again with worsening drought afterward with gradual warmup

Plain-language summary:

 

Showers and possibly scattered thunderstorms are likely today into Monday, though like it always has been for the past few weeks, rainfall amounts for most will be rather unimpressive. It then turns cool and dry Tuesday through early Thursday, then cool and showery late Thursday through possibly Saturday. Afterward, it gradually warms up but stays dry, worsening the drought.

 

Meteorological discussion:

Scattered showers and thunderstorms today into Monday with unimpressive rain, then cool and dry Tuesday and Wednesday 

 

A broad upper-level low is pushing east across James Bay today, with disturbances rotating around it. The first disturbance is currently over the region, generating clouds and showers, a rarity recently. A second disturbance associated with the main cold front will trigger more showers and possibly thunderstorms Monday mainly from Vermont eastward. Both today and Monday, the majority, but not all, of showers and thunderstorms will occur in the afternoon and evening when daytime heating and instability is maximized. Even then, as is typical for the past few weeks, there isn't a good surge of tropical moisture, and the air aloft is still relatively dry, limiting the intensity and coverage of showers. As such, rainfall will be unimpressive for most, with only isolated locations receiving >1" (25 mm). Behind the cold front, it will be cool and dry on Tuesday and Wednesday as another broad surface high-pressure system moves into eastern North America. 

 

Source: Aviation Weather Center and TropicalTidbits

 

 

Source: TropicalTidbits

 

 

Cool and unsettled with slow-moving disturbance late Thursday through Saturday 

 

Another upper-level disturbance/cold front will arrive Thursday into Friday, with a brief slight warmup ahead of it. Unlike previous model runs, most of today's models, except the GFS, show upper-level ridging building overtop the disturbance quickly enough to make the disturbance almost cut off over our region, making it move much slower than otherwise. In this scenario, cool, cloudy, and showery weather would extend from Thursday afternoon all the way through Saturday before finally moving off to the east by Sunday as a broad, cool, Canadian surface high pressure moves in. There is always considerable uncertainty in timing with these cut-off systems though. Despite the clouds and showers, with no deep, rich moisture return ahead of the system once again, rainfall will not be impressive. This stretch of cool weather is powered by a classic +PNA pattern with upper-level ridging and hot weather near the West Coast of North America and upper-level troughing and cool air in eastern North America. The slightly negative -NAO and associated high-latitude blocking is also helping to push the mid-latitude jet stream southward, allowing the cool Canadian air to push southward deep into the U.S., though the slightly positive +AO might be preventing the coldest Arctic air from reaching our region. 

 

Source: TropicalTidbits

 

 

Source: Climate Prediction Center

 

 

Dry weather returns Sunday and beyond with gradually warming temperatures and worsening drought 

 

After the cool, unsettled weather later next week, models generally agree that the upper-level ridge in western North America will weaken as a strong, possibly cut-off upper-level low approaches the Northwest U.S. coast. This will promote a downstream upper-level ridge to build in central and likely also eastern North America, especially over Canada, and the amplified or even cut-off nature of the pattern means that the continental-scale pattern will likely move quite slowly. The pattern appears to be configured to bring yet more big and dry surface high-pressure systems across eastern North America, with no storms or any flow of moisture from the western Atlantic or Gulf of Mexico. It will also likely turn gradually warmer as we lose the shots of cold air and it stays rather sunny, though not as hot as earlier in August given the lower sun angle in September, and nights will likely remain cool with longer nights in September and relatively dry air. There is also no strong wind to advect hot air either, and it is possible that most of the warm weather stays to the west while backdoor cold fronts straight from the north or even northeast keep our region cooler. Actually, the upper-level low approaching the northwest U.S. coast fizzles, and we are just left with a broad upper-level ridge over most of Canada with a near-neutral PNA and a neutral NAO (losing the Greenland blocking leading to the amplified troughs in the near-future). This is not a favorable configuration for big heat and humidity, but favors well below average rainfall in our region for a while still, making the drought just worsen after what is among the driest Augusts on record for some. Of course, long-range precipitation forecasts are always iffy, and models are not unanimous on an extremely dry forecast for now at least.

 

Source: TropicalTidbits

 

Summer heat mostly over for this year; sharp cold front with showers today; cool and dry through Thursday except showers Wednesday; briefly warm to hot Friday and Saturday; showers and thunderstorms Saturday night into Sunday; then cool and dry for several days again

Plain-language summary:

 

A sharp cold front is bringing some showers and much cooler air into the region today, marking the end of summer weather for the region for the most part. It will be rather cool Monday through Thursday, with tonight being especially cool, and it being dry except some showers with unseasonably cool daytime temperatures on Wednesday. It briefly turns warm to hot Friday into Saturday before a cold front with showers and possibly thunderstorms Saturday night into Sunday brings in another unseasonably cool air mass for several days, with more dry weather.

 

Meteorological discussion:

  

An unusually strong and sharp cold front by summer standards is plowing southward through our region today, with quickly falling temperatures even in the middle of the day. While southern Vermont to southern Maine is seeing temperatures approaching 90F (32C) with mostly sunny skies, behind the cold front, it is only around 60F (16C) in southern Quebec and northern Vermont! Only 90 miles (145 km) separates 89F (32C) from 57F (14C) in Vermont this afternoon. A line of showers marks the front, but the low-level cold air will come in so quickly that it will generally not allow for particularly strong thunderstorms, especially with the front arriving in the morning in most spots.

 

Source: Aviation Weather Center

 

Source: TropicalTidbits

 

 

The -NAO associated with the strong Greenland ridge, along with a strengthening broad upper-level ridge in the western and central U.S., is promoting rather pronounced upper-level troughing in Quebec and Atlantic Canada early this week, leading to a surge of cool and dry air directly from the north into our region. Some places could approach 41F (5C) tonight, while almost everyone along and northwest of the Appalachians will struggle to get past 70F (21C) on Monday, even with almost full sunshine. Given the Greenland blocking, the continental-scale weather pattern won't shift a whole lot for several days, as the boundary between hot and cool gets stuck just to our south. It will be somewhat warmer on Tuesday with the cool air mass modifying, but then a weak disturbance will move east-southeastward along the boundary, reaching our region Wednesday with widespread cloudiness and light rain. Though the weak dynamics will mean relatively little rain for most places, the widespread thick clouds will mean especially cool daytime temperatures, below 68F (20C) for most. Sunshine and dry and somewhat warmer weather will return on Thursday.

 

Source: TropicalTidbits

 

 

Source: Climate Prediction Center

 

A piece of the central U.S. ridge will push east into our region Friday and Saturday, leading to briefly hotter temperatures, but not nearly as hot as earlier in August. By Saturday night or Sunday, another reinforcing trough and unseasonably cool air mass will move into our region, with some showers and possibly thunderstorms along the preceding cold front. All this troughing will cause Erin to make a sharp right turn just off the North Carolina Outer Banks mid-week, with the trough not digging far enough south and/or amplified enough to promote southerlies to pull Erin northward into our region; instead, the westerlies on the southern edge of the trough will simply steer Erin to the east, well south of our region.

 

Source: TropicalTidbits

 

By the following week, a big cool surface high pressure will have set in from the northern U.S. Plains to eastern Canada, similar to at the end of July, drying things out again, only likely cooler given the more robust cool air masses in late August coming from the northwest. As the surface high pressure slides eastward, it could warm back up somewhat while staying mostly dry, with the -NAO easing a bit, but a bit of upper-level ridging maintaining in the western U.S. will make it difficult to sustain more than a day or two of true hot weather before another upper-level trough and cold front beats the heat back down again. Although occasional hot days are still possible through mid-September, I think the truly hot part of summer is over.

 

Source: TropicalTidbits

 

Intense heat wave through Wednesday; still hot most days afterward, perhaps cooling down the following week with up-and-down temperature pattern; unusually dry for over a week except scattered t-storms Wednesday

Plain-language summary:

 

An intense heat wave will affect our region through Wednesday, with Tuesday being the hottest day for most. The unusually dry weather in the past 2 weeks, along with the dryness of the heatwave through Tuesday, is leading to a developing flash drought, along with unusually low humidity and nighttime lows for an intense heat wave. Scattered showers and thunderstorms are likely on Wednesday before turning dry again as well as cooler for Thursday and Friday. Heat returns next weekend, but will likely not be as intense or long-lasting as the current heat wave. A more up-and-down temperature pattern is likely for the following week, still leaning warm with some hot days likely. It will likely still be predominantly dry, unless a hurricane in the western Atlantic tracks into our region the week after next week, bringing strong winds and heavy rain, which is just one of many possible scenarios for now.

 

Meteorological discussion:

 

Intense heat wave through Wednesday with relatively low humidity, dry and sunny except some scattered showers and thunderstorms Wednesday 

 

An upper-level trough that was over the Rockies yesterday is now lifting into the northern U.S. Plains and central Canada, promoting an upper-level ridge downstream over eastern Canada. It has been incredibly dry across the region over the past 2 weeks outside of scattered afternoon thunderstorms over higher terrain, with many lower-elevation locations having received little or no rain during that period with dry surface high pressure dominating after the push of a big area of cooler, drier air into eastern North America at the end of July. Although the air was cool initially, the lack of replenishment of the cool air, along with plenty of sunshine and some westerly flow advecting warm but still relatively dry air into the region, without any southerly component bringing moisture from the Gulf of Mexico or western Atlantic, it has become hot but with low humidity, somewhat unusual for the middle of summer in our region. With the low humidity, plentiful sunshine, and lack of rain, the ground has rapidly dried out, with a flash drought potentially starting. The U.S. Drought Monitor already showed much of northern New England being abnormally dry even by this past Tuesday, before the dry heat wave. This is allowing it to heat up more during the daytime than otherwise, with less of the sun's energy going into evaporating ground moisture. It is also leading to lower humidity, lower heat indices, and lower nighttime temperatures (especially combined with clear skies and rather light winds with the surface high pressure) than typical for a heat wave in August.

 

Source: NOAA and U.S. Drought Monitor

 

 

As the upper-level ridge slowly pushes to our east, leading to weak southwesterly flow, it will remain sunny and continue to get hotter but only slightly more humid through Tuesday, with still no strong flow of moisture from the Gulf of Mexico or western Atlantic. The hottest locations just to the northeast of the Adirondacks, in far southern Quebec and northern Champlain Valley, with downsloping warming due to the weak southwesterly wind, could approach 100F (38C), the hottest in all of eastern North America east of Texas! This is similar to the late June heat wave, though this heat wave will last longer but also feature lower humidity. The more southerly nature of the low-level flow this time, though weaker, means that coastal New Hampshire and Maine will see more ocean moderation than with the late June heat wave. By Wednesday, a surface low pressure will travel into central Quebec, with its associated cold front triggering scattered showers and thunderstorms over the region, though the best dynamics look to be off to the north, limiting the coverage and severity of the storms. Still, the clouds and any rain that does fall will keep temperatures at least slightly lower than Monday and Tuesday.

 

Source: TropicalTidbits

 

 

Cooler and drier Thursday and Friday, turning hot again next weekend 

 

The cold front will be relatively weak, with the progressive pattern with the strong jet stream retreated to northern Canada (common with the +NAO we currently have) not allowing much surges of cool, Arctic air into our region. Still, the Canadian surface high pressure behind the front will lead to weak northerly flow on Thursday, leading to noticeably cooler (but still near or slightly above climatological average) temperatures for Thursday and Friday, especially along and northwest of the Appalachians, and with dry weather returning. However, another upper-level trough will dig into western Canada by Thursday and Friday, promoting an upper-level ridge in eastern North America again next weekend with it heating up again to perhaps very hot values again next Sunday. It seems doubtful that it will be as hot as this upcoming Monday and Tuesday, with less time for the cooler air mass to recover and the sun angle weakening as we head past mid-August, but the dry ground will likely boost daytime temperatures again.

 

Source: TropicalTidbits

 

 

Source: Climate Prediction Center

 

 

More up-and-down temperature expected after next weekend, still leaning warm with some hot days, likely still dry 

 

Although long-range ensembles continue to show some upper-level ridging prevalent in eastern North America through even late August, the upper-level troughs in western Canada could subside and get replaced by upper-level ridges at times, with a neutral or slightly positive PNA. Also, the NAO is expected to turn to neutral, which could allow the mid-latitude jet stream to penetrate south of our region at times, allowing cooler air masses from Canada to enter our region. These cool air masses are also getting stronger as daylight hours and sun angle start to really decrease quickly after mid-August, making it difficult to sustain hot weather after next weekend. There are signs that surface high pressure systems will frequently travel from Hudson Bay into our region or Atlantic Canada, bringing with them cooler, drier air masses into our region directly from the north, even if these setups tend to not allow the cooler air masses to penetrate much to our south. However, I do still expect temperatures to be overall above average with some hot days, especially given the current dryness, though the more up-and-down temperature pattern could promote more storminess, and it will also take time for the hot air to return after a surge of cooler air. 

 

Source: TropicalTidbits

 

 

One potential caveat to the dry pattern is a tropical disturbance currently in the eastern Atlantic that is highly likely to develop into at least at tropical storm if not a hurricane next week (in which case, it will be named Erin) as it heads into the western Atlantic. There is the potential for the storm to track up the U.S. East Coast and bring strong winds and heavy rain to our region for the following week if the track is perfect, but it is way too early to have any confidence on the track, and ensembles currently show a wide range of possible solutions, as you would expect this far out, though most of them show the hurricane going east of our region.

 

Source: Weathernerds