Warm air is being delayed in moving into the region, but will make substantially more progress today than it did yesterday. Currently we have a sharp frontal boundary located over southern NH, with Keene reading in at 55 and Manchester only 46. Meanwhile, Boston is already at 67! This warm and humid airmass will make slow northward progress today, but as we all know there are numerous ways that promised warmth never comes to fruition this time of year.
The first applies to the coast. Any onshore component to the wind and we cut dozens of degrees off the high temp. For coastal areas northeast of Portland, there will be a stout onshore component to today’s winds, meaning highs stay stuck in the upper 40’s to low 50’s.
The second applies to the foothills and northern mountains. When you add undulations to the terrain, and a little leftover snowpack, it’s just hard to get rid of the cold air. I think we end up doing it outside of the mountains north of Route two only because there’s a moderately strong low pressure system to our north over the St Lawrence valley instead of the high pressure system we usually rely on to “dam” the cold air against the higher terrain. So the mountains will remain around 50 degrees, but most of the foothills especially south of Route two should get into the warmer airmass with highs in the low to mid 60’s.
For those areas in the interior coastal plain that can access the full potential of today’s warmth, your forecast today is looking pretty lovely. Morning clouds and fog should burn off to at least some afternoon sunshine as highs soar into the upper 60’s to low 70’s. Some parts of interior southern NH could even get up into the 75 degree range!
For the entire area, clouds will increase this afternoon as the system to our west slowly closes in. Rain should hold off until around sunset in NH and far northwestern parts of Maine, and will spread slowly south and east after dark. The bulk of the rain arrives tomorrow, and there will be plenty to go around.