Showers today, back door cold front mostly blocking unseasonable warmth through at least Thursday; some showers on Tuesday and next weekend but no major storms for foreseeable future; cool and unsettled following week?

Plain-language summary:

 

After a few sunny or mostly sunny days with cold nights and low humidity, it is warmer and much more humid today. A few showers are expected tonight with a cold front that will block the unseasonable warmth building just to the southwest from reaching our region at least through Thursday. A few showers could occur again on Tuesday, but rainfall amounts will be light. It will likely turn warmer for Friday and next weekend, with showers and maybe a few thunderstorms likely next weekend, before it turns cooler and perhaps showery and unsettled for a while the following week, but no major storms are expected for the foreseeable future.

 

Meteorological discussion:

After a few sunny or mostly sunny days with cold nights and low humidity, the diffuse warm front that passed through last night, bringing elevated thunderstorms to much of the region except Maine, means that it is warmer and much more humid today, with partly to mostly cloudy skies for most and temperatures reaching 68F (20C) or higher in many lower elevation spots, especially south of the U.S./Canada border. However, a cold front is already approaching from the northwest and is entering southern Quebec now and will penetrate down to central New England by tomorrow morning before stalling out and weakening and then sort of transitioning into a backdoor cold front with maritime influence. Some showers will accompany this front, but rainfall amounts will be light again. The main contribution of the front will be to block the unseasonable warmth and humidity building just to the southwest (a result of the -PNA pattern associated with a trough in the western U.S. and a ridge in the eastern U.S.) from reaching our region on Monday and Tuesday like was expected a few days ago. As such, few if any locations will reach 70F (21C) on either day, as opposed to the 77F+ (25C+) that looked possible a few days ago. Dew points will also drop as the Canadian air mass moves in. Monday looks dry with a mix of sun and clouds for most, but as the backdoor front tries to lift northward again on Tuesday, some showers are likely again, leading to daytime highs cooler than on Monday in cloudy and rainy areas. Still, given how diffuse the front and any disturbance is, rainfall amounts will be light.

Source: College of DuPage

Source: LightningMaps.org

Source: TropicalTidbits

 

By Wednesday, the pressure and temperature gradient weakens, and although lingering low clouds could cause some areas, especially in eastern New England, to still be chilly, it will warm up everywhere through next weekend with the May sun angle and lack of any true cold air mass. The -PNA and associated eastern U.S. ridge will still be dominating, though there may be a backdoor cold front again to block the warmest air mass. Warm advection also dominates again by Friday with southerly flow, though eastern New England will likely be not quite as warm due to some influence from the still cool western Atlantic waters and any possible backdoor cold front, typical for spring. There is some uncertainty for the weather pattern next weekend, but there likely will be a low-pressure system in the northern Great Lakes or northern Ontario bringing in warm and humid air into our region, along with showers or possibly scattered thunderstorms. However, the storm appears to be weakening as it shears out over top of the eastern U.S. ridge, and most of the showers and thunderstorms are likely to be benign.

Source: TropicalTidbits

Source: TropicalTidbits

Afterwards, though not shown well in the NAO or AO indices, there is some indication of high-latitude blocking leading to slow-moving cut-off upper-level lows slowly moving through our region for the following week. As has been the case throughout the cool season, no really cold air mass is expected, but frequent clouds and showers could keep temperatures somewhat below average for a while, particularly during daytime. The upper-level lows will also prevent the warmth over the central and southern U.S. from reaching our region. Summer weather looks to wait for a while. Still, no major storms are expected. Also, without a cool, dry surface high pressure, the risk of frost or freeze looks low.

 

Source: Climate Prediction Center

 

Source: TropicalTidbits