Stormy Season Changer

An upper level low pressure system passes through the region this weekend and with it might come the end of the freezing levels that soar above the mountain.  A 7500 foot freezing level predicted on Friday seems to be the coldest and a big change from 15,000 foot freezing earlier this week.  There's also quite a bit of wind generally associated with a flux in temperature this large.  It's not a great idea to be up on the upper mountain when there's high winds or a swirling cloud cap.  Here's a blurb from the latest Recreational Forecast:

.SYNOPSIS...Cooler weather on the way beginning Thursday. A weak 
upper level trough will move through the park Thursday night  
with the flow aloft becoming northwesterly. The combination of low
level onshore flow and northwesterly flow aloft will clear most 
of the smoke out of the area by Friday. Weak systems embedded in 
the northwesterly flow aloft will cross the area over the weekend 
for a slight chance of showers.

 

An example of clouds building near Mount Rainier from a couple years ago.

With the fall equinox still a month away it's hard to believe that autumnal weather has already arrived, but the sun has started to dip lower in the sky and the long term forecast has a cooling trend to it.  It's the time of year to start packing warmer clothes for a summit attempt and to be prepared for longer, more intense storms.  Also, be cautious on the now steep and firm late-August snow when it refreezes.  The slushy booting conditions of mid-summer can become dicey and treacherous before the new soft snow of winter falls. 

Here's a link to some of the more useful weather resources to help predict what conditions will be like when you're on the mountain.  Remember to check in with rangers when you register at the ranger station and the evening before you climb at high camps for the latest forecast.