Plain-language summary:
After a few light scattered showers today, it will dry out again, with dry and mostly sunny conditions expected through Thursday with a gradual warmup. Thursday and Friday could feature summerlike daytime heat, though with low humidity and cool nights. It will then cool down substantially, still with not much rain, for a few days before warming back up for the following week, with most days being warmer than average, especially during the daytime. Little rain is expected over the next 10 days, with the drought continuing to intensify, before possibly turning wetter at least temporarily, though it is unlikely to mark a shift to a longer-term wetter weather pattern yet.
Meteorological discussion:
Dry and sunny with gradual warmup through Thursday
A very weak disturbance/cold front is passing through today, with just some increased clouds earlier today. A few days ago, some models showed there being an upper-level low bringing more substantial rain, but instead, it is a much weaker and stretched out disturbance. Both dynamics and moisture lacking (there is no moisture flow from the Gulf of Mexico or western Atlantic), with almost no rain falling and reaching the ground anywhere. Another broad Canadian surface high-pressure system is moving into our region, with slightly cooler air directly from the north, but it has no access to real cold air with only a weak temperature gradient.
Upper-level troughing moving into the western U.S. in the next day or two will promote the already dominant upper-level ridge across Canada to focus its strength in eastern North America instead of farther west, where it has been most of the time over the past few weeks. This is despite a +PNA that is continuing, but likely, the +PNA is powered by the intense ridging still present in western and central Canada instead of the western U.S. The -NAO is also associated with the ridge being centered at a rather high latitude over Quebec, with a very weak cut-off low to the south over the coastal southeast U.S., leading to a slow-moving blocking pattern. The eastward expansion of the ridge will cause dry, sunny weather to continue in our region but with a gradual warmup muted by the lower September sun angle but aided by the very dry ground leading to all of the sun's energy going to heating the ground instead of evaporating ground moisture. Daytime temperatures will reach summerlike levels, with highs exceeding 80F (27C) on Wednesday and Thursday in lower elevation locations. It would have been even hotter if there had not been the coastal upper-level low that is a bit close, weakening the westerly flow of hotter air. Once again, the westerly flow will not allow for any Gulf of Mexico or western Atlantic moisture, leading to relatively low dew points and still cool nights.
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| Source: TropicalTidbits |
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| Source: Climate Prediction Center |
Stronger cold front Thursday night with little rain expected, cooler afterward and remaining dry for at least a few more days before possibly turning wetter
A stronger cold front will push into our region directly from the north Thursday night or around that time, beating down the upper-level ridge in our region somewhat. Once again, the upper-level disturbance responsible for the cold front will be mostly to the northeast, leading to our position being in the dry side of the upper-level wave train, especially with no Gulf of Mexico or western Atlantic moisture. There is still some time for the overall configuration to change, but it appears unlikely again for anything more than a few light showers from this front. Another stronger, cooler Canadian surface high-pressure system will establish itself over Quebec next weekend and may transition into a cut-off upper-level ridge, leading to more dry weather. The surface high-pressure will eventually move to the east, leading to the cool air mass modifying and a gradual warmup through the middle of the following week as upper-level ridging builds back into our region, though it will likely not get as warm as this upcoming Wednesday and Thursday. With all this dry, sunny, and mostly warm weather over the next 10 days promoting rapid evaporation of what little ground moisture there is left, the drought will continue to intensify. After that, it is not clear if the high-pressure system will continue to sit over our region, blocking any storms from reaching our region for another several days or more into the following week, or if the high-pressure system will push far enough to the northeast for some storminess slowing approaching from the U.S. Plains to throw in more clouds, moisture, and eventually rain into our region. The storminess could also just weaken, leading to cloudier skies but only light rains. Upper-level ridging appears to be dominant in eastern Canada through the end of September, which will likely any wetter period temporary.
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| Source: TropicalTidbits |
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| Source: TropicalTidbits |
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| Source: U.S. Drought Monitor and Canadian Drought Monitor |
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