Yet another mostly dry week ahead except Wednesday and Wednesday night; starts cool with isolated frost risk but generally warmer for rest of the week into beginning of June except this Thursday; possible hiccup if slow-moving storm grazes afterward

Plain-language summary:

After the biggest rainfall in weeks for most yesterday and yesterday night, we return to yet another prolonged period of dry weather, except Wednesday and Wednesday night. It will be rather cool on Monday even with abundant sunshine, and some frost is possible Monday night outside of the St. Lawrence and Champlain valleys and areas near bodies of water, but it will not be nearly as cold as last Wednesday night’s freeze. It will quickly warm up for Tuesday and Wednesday with abundant sunshine before it turns sharply cooler with some showers later Wednesday into early Wednesday night. It gradually warms up afterward, but with a complication from a storm that could stall just to the south that could bring cooler weather with more clouds and showers than earlier expected. The pattern still looks to gradually turn more summerlike through at least the beginning of June.

Meteorological discussion:

The somewhat disorganized low pressure that passed through yesterday and yesterday night brought the biggest rainfall in weeks in many areas, though there was a pronounced hole from the southern Adirondacks up to the Champlain and St. Lawrence valleys. This might put a small dent to the abnormally dry conditions developing in parts of the region, but the dry weather afterward will remove any little dent.

 

Source: CoCoRaHS

Source: U.S. Drought Monitor

With that storm out, dry weather has returned. A cold front is plowing southward through southern Quebec this afternoon, but it is actually rather warm ahead of it with dry westerly flow and mostly sunny skies. Some scattered showers developed right ahead of the cold front in southern Quebec, eastern Ontario, northern New York, and northern Vermont due to the sunshine-induced instability. Behind the cold front though, there is a chilly Canadian high pressure that will bring a northerly flow of cool air directly out of Quebec, leading to below average temperatures on Monday even with abundant sunshine. With dry air , clear skies, and lightening winds Monday night, some areas, especially outside the broad St. Lawrence and Champlain valleys and away from any bodies of water, could see a frost or freeze, but it will not be nearly as widespread or as cold as last Wednesday night’s widespread hard freeze.

Source: TropicalTidbits

As the high pressure moves southward and winds turn more westerly, the cool air mass will quickly modify with abundant sunshine, and temperatures will be back above average on Tuesday and Wednesday afternoons. However, another sharp cold front will enter Wednesday afternoon, akin to a less intense version of last Tuesday’s cold front. Once again, with no Gulf of Mexico or Atlantic moisture to tap into, there will not be a lot of rain with the front, with what little rain mostly falling behind the front.

Source: TropicalTidbits

Behind the front, it will be cooler on Thursday. However, this time, there will not be such a quick rebound in temperatures. This is because the disturbance sending the cold front will dig far enough south, cut off, and interact with another system off the Southeast U.S. coast to form a slow-moving cut-off low. The extra clouds and occasional showers will keep it a bit cooler even as warm or even hot air pushes over it to the north, though rainfall amounts are still not expected to be significant. There is even a possibility that the cut-off low eventually pushes northward into New England, bringing even cooler and wetter weather, though that appears to be a less likely scenario for now. Still, there will be a reversed meridional temperature gradient as the warmest air will at least initially go to the north over northern Ontario and central Quebec. This cut-off low presence has only been clear for the past day or two, and the precise evolution that determines how much rainy and cool weather we get and who gets it is still quite uncertain.

Source: TropicalTidbits

Source: TropicalTidbits

With the ridge in Western Canada finally breaking down, with a change to cooler and wetter weather there, the downstream ridging in Eastern Canada should prevent any more surges of cold air coming down from Hudson Bay for a while. Warmth and humidity will also gradually take over as the cut-off low likely pulls away just after next weekend with more flow out of the Gulf of Mexico and possibly western Atlantic. This more summerlike pattern will likely continue into at least the beginning of June, with perhaps the first real thunderstorms of the warm season occurring.

Source: TropicalTidbits