Lots of Heat but Limited Humidity

On paper right now this heat wave appears to be intense but probably of a relatively short duration. Temperatures in the upper 90s will be common Monday and Tuesday but dew points will struggle out of the low 60s.

The atmosphere remains very dry and that made today’s 94º at BDL and 97º at BDR feel much more bearable. In fact when winds at BDR switched offshore, and the mercury shot up, the dew point plunged into the 40s! That’s very Phoenix-like with a relative humidity of 20%.

Tomorrow should be even warmer. +20 or +21 air at 850mb, deep mixing, and offshore winds will allow temperatures to soar. The deeply mixed boundary layer will also mix down drier air from aloft along with downsloping/compressional flow that will do the same. Dew points should remain in the 55º-60º range tomorrow.

Tuesday will be more humid and will likely be our most oppressive day with air temperatures near 100º and dew points in the 60º-65º range. This is nothing terribly out of the ordinary (happens probably every other year) but it will be very uncomfortable with heat index values over 100º.

Past Tuesday the forecast is showing signs of changing. The European model has been all over the place in recent days but one feature that has been presistent is a retrograding upper level low from south of Nova Scotia to near the Mid Atlantic. This serves to break down the ridge and effectively break down the heat pump. That said, temperatures will remain warm and humidity will crank up.

The 18z GFS (500mb 72 hour chart on the left) now shows the upper level low making a dramatic swing back to the coast bringing with it moisture and maybe even some showers Thursday and Friday. This could result in an early end to the heat wave but will keep us in a soupy, humid, and unsettled weather pattern.

Wednesday now is our wild card day and will depend on how fast the ridge starts to break down. The sooner it does so the faster cooler temperatures will move in. I currently have 97º forecasted on Wednesday but there is fairly high “bust” potential with this forecast.

Ryan

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