Unfortunately we’ll have to deal with midsummer heat today as southwesterly flow kicks into gear and carries tropical air into the region. High temps will race into the 90s across nearly the entire area, with just the immediate coast (east of Portland) able to hang on to mid/upper 80s. Some spots inland will make a run at 95 under sunny skies and with an assist from downsloping. The mountains won’t be much cooler than inland spots today as the core of the hot air remains to our north (Caribou will make a run at 100 today!).
Humidity will also be on the increase today as dew points rise from around 60 to around 65. This means heat index values will end up in the mid/upper 90s inland which is hazardous for sensitive groups.
The increase in humidity combined with the very hot temperatures means that the atmosphere will become increasingly unstable this afternoon. With CAPE (a measure of atmospheric instability) in the 1500-2000+ J/kg range across most of the region, it won’t take much forcing to get some scattered showers this afternoon. Without any frontal boundary to provide this forcing, we’ll have to rely mostly on the localized forcing from terrain features. So if you’re in the mountains, don’t be shocked if a brief but heavy shower pops up this afternoon. It may even have a rumble or two of thunder.