Apr 18, 2015 7:33 PM
High pressure will settle over us for Sunday with sunshine, lighter winds and cooler temperatures coming down from Canada with highs only in the 50's and Low 60's.
Marathon Monday will start off cloudy, cool and dry. By midday showers will begin to develop then turn into a steadier rain for later in the afternoon and evening. A deep upper low will be shifting towards the Great Lakes, helping to steer this rain right up into the Northeast along with a warm front. Timing is everything. If you're running in the marathon...the sooner you can finish the better off you will be weather-wise, because conditions will be going downhill in the afternoon.
Cool SE winds will become a bit breezy during the day. The inclement conditions will help keep temperatures near 50. Rain will become heavier Monday night through early Tuesday where heavier downpours will be possible. By Tuesday morning, another wave of low pressure will be developing on a cold front which will track into Southern New England. This will likely aid in helping to keep the rain going through the morning before finally tapering off to showers. Over 1" of rain is expected with this disturbance which could lead to some minor street flooding, as well as rises on area rivers and streams.
An Upper level low over the Great Lakes will be shifting east for most of next week. This will help to suppress warmth south of us, keeping temperatures seasonally cool, along with providing periodic instability showers almost every day as pieces of lift in the upper level flow will enable these periodic showers from time to time. Temperatures will be cool enough in the mountains for even a few snow showers Wednesday or Thursday.
Beyond this the long range forecast is not looking good. It appears that a typical springtime pattern will be setting up which means an upper level Low will cut off from the main flow in the jet stream over southeast Quebec province for about 10 days. That in turn will send plenty of cool air our way along with several days of unsettled conditions, meaning rain or showers will become an almost daily threat through the end of the month as spokes of energy pinwheel around this stalled system.
Bill Gile | Meteorologist
New Hampshire One News