Waning sky faucets

There has been little need for outdoor water faucets the last few weeks across the northwestern portion of the inland northwest as the cool and damp regime that rounded up the last half of May has continued through the first half of June.  These conditions have delayed the curing of fuels and commencement of fire season for 2-4 weeks in the Northern Rockies.  Patrick Gocke, a Grangeville smokejumper chimed in with his thoughts:

“The rains changed what some thought was going to be a potentially early start to the fire season. We have pushed a few jumpers up to AK and several more down to the South West.”

And for good reason, as dry conditions have been the rule for most of the rest of the western United States including central and southern Idaho. The sub par moisture this month has further compounded already critical fuel moistures across the southwest and central and southern Rockies enabling wildfire activity and necessitating the reallocation of firefighting resources.

While the commencement of summer might be the summer solstice or the end of the school year, climatologically summer is the dry season for much of the inland northwest.  From a climatological perspective, the start of summer signifies the beginning of fair weather. The following figures help illustrate the transition from the long rainy season to “summer” by showing average daily precipitation amounts by calendar date (x-axis) for Boise, ID and Spokane, WA. Note the abrupt drop off in daily precipitation over the month of June.

The ratio of precipitation accumulated over the last half of June to the first half of June across the western United States paints a broader picture of this transition.  Land areas in white have been masked out as they had less than a tenth of an inch of precipitation climatologically over the second half of June.

The dynamics behind this abrupt drop off include a northward retraction of the storm track as well as an overall weakening in the jet stream due to a reduced pole-to-equator temperature contrast.

Of course, this transition to summer is rarely a smooth one. This year is no exception. A strong jet stream and cold front passing into Alberta and grazing the northern parts of the inland northwest is bringing sustained strong winds across the region with temperatures falling behind the front. Several spots will see their record coldest maximum temperature be threatened by todays high temperatures in the 50s.

The Idaho panhandle, eastern Washington and western Montana look like they will have to wait a bit longer for summer to officially arrive as weather systems flirt with the region. In time, the faucets from the sky will fade and be replaced by faucets that bring water our vegetable gardens. Fortunately, reservoir levels across Idaho are at or near capacity due to respectable water year precipitation and strong carryover from the previous year.

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