Sunny, Warm and Humid.

It was as though we flipped a switched from spring to summer Thursday night.

After a breezy, cool and damp Thursday – which served as a bit of an exclamation mark on a week’s worth of below normal temperatures – we were greeted by clear skies and mild temperatures Friday morning. And those mild early morning temperatures set the stage for our first truly summer-feeling day of the season. Temperatures soared into the 80s by midday under plenty of blue sky and strong late June sunshine…and there was a noticeable feel of mugginess in the air.

We’ll get a repeat performance today (and for much of the next week or so) with sunshine prevailing through the day and temperatures again climbing into the 80s around the Cape. It’s possible a few backyard thermometers touch 90F. It will remain rather uncomfortable with dew points in the middle and upper 60s for a good chunk of the day and winds will once again be fairly light.

While this overall weather will remain in place through the end of next week, Sunday’s forecast is slightly more challenging.

A complex of showers and thunderstorms will pass through Northern New England tonight and be followed by a small area of high pressure on Sunday. The combination of these two features will force a shallow frontal zone to shift south and westward through the Gulf of Maine and into eastern Massachusetts during the day on Sunday. This shallow frontal zone – a weak backdoor cold front – will slide onto the Cape during Sunday morning, shifting our winds to the northeast and pushing a pocket of marine cooled air westward. As a result, while temperatures may jump into the 80s Sunday morning, we should see a period of refreshing air take hold during the midday and afternoon hours with readings falling into the 70s…especially on the Outer Cape.

It should be noted that these types of meso-scale weather set-ups can yield some wide ranging conditions around the Cape. It’s not uncommon for such a scenario to yield a 15 to 20F temperature difference for a short time between the Outer Cape and the Upper Cape. Consequently, it’s possible that parts of Falmouth, Mashpee, Sandwich and Bourne are between 85 and 90F during midday while Provincetown and Truro are falling through the 70s.

Model guidance doesn’t usually “see” this type of discrepancy too well but this morning’s high-resolution NAM model does illustrate the basic idea quite well:


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