June 20, 2013: Seasonable Weekend, Then Hot, Humid

Forecast Highlights:

A high pressure remains in control through the late week and weekend, with temperatures slowly warming up and generally remaining near average along with mostly sunny skies. A warmer air mass will spread in by Sunday, with heat and humidity returning for the Sunday-Wednesday time frame along with a risk of isolated thunderstorms, increasing by mid-late next week.

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Tonight - Saturday: Mostly Sunny, Seasonable

The high pressure that moved over the region today continues to gradually slide offshore, setting up for a SW flow for the next few days with temperatures gradually warming up but remaining near average without humid conditions. Mostly sunny skies will continue again for Friday and Saturday, with highs on Friday reaching the upper 70s to low 80s inland and the low to mid 80s elsewhere, and Saturday's highs reaching the low to mid 80s across the area.


Sunday - Next Week: Hot, Humid, Some Storms

After a seasonable start to the weekend, a hot and humid air mass will spread in from the west, with 850mb temperatures in the 15-20c range along with a continued SW flow and dew points in the mid 60s-low 70s range resulting in hot and humid conditions starting on Sunday. At this time, there is relatively high confidence for the Sunday-Tuesday time frame, with highs on Sunday likely in the mid to upper 80s along with an increase in humidity, with the warming trend continuing into Monday and Tuesday with highs in the upper 80s to low 90s, with isolated mid 90s not out of the question in the warmer case scenario, along with humid conditions and heat index values likely in the low to mid 90s range. Partly sunny skies are expected for both days; most of the area will be dry, although isolated afternoon-evening thunderstorms can't be ruled out especially north of NYC.

Uncertainty increases in the outlook by Wednesday into the late week, with a variety of solutions shown on the models, ranging from the ECM and 12z GFS which bring a back door cold front through with rain and much cooler temperatures to the 18z GFS which shows even hotter temperatures for this time frame, potentially well into the 90s. At this time, the latest expectation is for heat and humidity to continue into Wednesday and/or Thursday, when a cold front may affect the region with thunderstorms and cooler temperatures, although the outlook is subject to some changes over the next few days. Going into the longer range, ridging is likely to settle in the western half of the US, which if verifies would result in troughing returning into the region along with cooler temperatures and the possibility of more rain/thunderstorm events to end the month.