This is our weekly Thursday seven day outlook for the  North Cascades in Washington state. Each week we will pick a region in the Western United States.
These seven day outlooks do bring some challenges and the first one is accuracy of forecasts beyond three days and this can generally be poor. Also, we are now at the  beginning of the shoulder season (fall ) and forecast models can have a difficult time making the transition, thus they can be inaccurate at times.  Finally, this past summer has brought record breaking warm temperatures (and drought) to much of the Pacific Northwest and models might struggle with adjusting from that pattern to “perhaps” a more typical cooler fall.
Having said all the above, we will first discuss this coming weekend Saturday September 26 and Sunday September 27 for areas near Mt. Baker (North Cascades) in Washington. For this Saturday and Sunday a trough of low pressure will be to our south and west of this region so we can expect dry conditions.  The ridge should remain in place for Monday September 28 as well. Then on Tuesday September 29 a trough of low moves in from the south for a slight chance of a few showers for areas well to our south. The forecast confidence for this weekend till Tuesday is medium to high 3.5 confidence level (0 low confidence and 5 high confidence). However from Wednesday September 30 till Friday October 2 much lower confidence (2.). The reason for lower confidence is we have a complicated pattern set up and one can see that on the map below.  The map below is  for Friday October 2 the 500 mb which is for 18,000 foot level. This shows a trough of low pressure just to the north of Washington state and a ridge of high pressure to the west and east of Washington. If this pattern verifies  for Friday October 2 the North Cascades will be cooler than normal but it should remain dry. However if that trough moves further south (towards North Cascades) than a high chance of precipitation. What will happen? Stay tuned!
Sept 24, 2015
Source: European Centre for Medium-Range Weather Forecasts

About the author: Michael Fagin has been providing mountain forecasts for the Pacific Northwest since the mid 1980’s and is currently providing weather forecasts for many of the Seattle Mountaineers Climb and Scramble leaders.  Michael also provides weather forecasts for some government agencies on key weather events in the Puget Sound Region: wind storms, major rain events, and snow events.  Since 2003 Michael has been providing weather forecasts for Mt. Everest for many of the major expedition and for mountaineers climbing the major peaks around the world. Forecast are also provided  for outdoor events like weddings. Finally Michael and his associates are used as expert witnesses in legal proceedings that concern meteorological events..   Michael Fagin is lead forecaster for West Coast Weather ,LLC and its affiliate firms: Everest Weather, Alaska Mountain Weather and Washington Online Weather.


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