High pressure that brought in the chilly weather for Thursday will be well off the coast by Saturday.
Low pressure advancing towards us will develop as it moves in our direction. Depending upon the model, it will be right over us or just to our south Saturday night.
A return flow of moisture ahead of this low pressure system will bring considerable cloudiness for Saturday, but no rain expected during the daytime.
Update: Saturday will be sunny in the morning, then thickening high clouds. Mostly cloudy by about 3-4 PM Saturday.
Rain should develop Saturday evening. Rain starts about 6-8 PM. Fairly heavy rain at night. Rain starts about 9-11 PM. Total amounts have decreased to about 0.6-0.9 inches of rain.
There are some differences between the Canadian and US models, but the US models have been consistent that we get about 0.75 + inches of rain Saturday night. (The Canadian GDPS has less development and much less rain.) High about 68º NBM Blue Bell with low spread (uncertainty) of 0.8º
The big question is how much development, how quickly the storm leaves and how much of an increase in its size due to intensification on Sunday. The models have varied. The NAM has some clearing Sunday morning. The GFS, Canadian and Model Blend (NBM) have lingering showers and clouds into late morning or early afternoon.
Update: Most models are showing the rain ending in the early to mid morning Sunday with gradual clearing.
High about 65º NBM Blue Bell with moderate uncertainty of 2.8º Very Windy.
An upper air low pressure system will combine with a surface low pressure system off of Cape Cod. This somewhat static pattern with upper air low pressure systems nearby should continue to affect our weather over the weekend.
A cyclonic flow around the low will bring instability and cloudiness as disturbances rotate around the low for Saturday.
Saturday will be mostly cloudy. A quick, widely scattered sprinkle can’t be ruled out, but the day will essentially be dry. Chilly temperatures. High 53º as 2.1º (NBM Model, Blue Bell)
The Sunday forecast is more uncertain. The same low pressure system should gradually move eastward, bringing less of a cyclonic flow. However some models are suggesting another upper air disturbance will move through from the west. Some sun in the morning. Considerable cloudiness, especially in the afternoon.
The GFS again cranks out a widely scattered sprinkle around 4 PM. The ICON model is also showing this upper air disturbance and a chance of sprinkles, especially far northern areas. High of 61.1º sd 3.0º (NBM Model, Blue Bell)
The forecast for the weekend continues to evolve regarding timing of the rain. Based on the latest GFS, we may luck out and have most of the rain fall Friday evening and Saturday evening, leaving much of the daytime hours cloudy, but rain-free.
A blocked weather pattern has been in place for the past several days with low pressure stuck in the middle of the country as well as low pressure system stuck in the Atlantic. This blocking pattern will evolve into a classic “omega block” (the jet stream flow resembles the Greek letter omega “ Ω “) by Friday.
The latest GEFS model shows this Atlantic low pressure system remaining even more entrenched as the low pressure in the central US tries to move east. High pressure caught in the middle will bring a moist, easterly wind flow and cloudiness to our area from Friday through Sunday.
Periods of showers and rain are most likely Friday and again Sunday.
Additionally, the Central US low pressure may induce secondary low pressure formation off the Delaware coast. This coastal secondary low may make the rain on Sunday moderately heavy (the ICON model cranks out almost 1.5 inches of rain Sunday.)
The models have backed away from heavy rain. The rain is looking less continuous over the weekend. Indeed there may be periods of cloudy, but dry weather. The exact timing of the rain over the weekend has shifted. Sunday’s rain may occur mostly before daybreak.
Blocked weather patterns result in long stretches of persistent weather. We never really know when the block will break down until we see some kicker system appear. So the block will be in place…until it isn’t. The models aren’t all that good at showing that moment in advance. As a result, long range forecasts sometimes become totally undone.
According to the GEFS that persistent low in the Atlantic and its effects on our weather may be with us much of next week!