Memorial Day Weekend Outlook

Mass exodus from northern Utah begins shortly with the annual pilgrimage to southern Utah and other environs for Memorial Day weekend.  I'm not traveling this weekend, but am taking a keen interest in the staycation forecast. 

Today looks to be a hot, dry one, but a closed low lurks over California.  This closed low will drift eastward and be located over Nevada tomorrow.  Thus, tomorrow is a transition day for Utah, with cooler air spreading in from the east.  The southeast part of the state will continue with dry, warm, windy conditions, but the western half of the state should be cooler tomorrow afternoon.  Northern Utah has a slight chance of a late day shower or thunderstorm. 

NAM 700-mb temperature (color contours), 500-mb geopotential height (black contours), 700-mb wind (barbs) and 3-hour accumulated precipitation (color fill) forecast valid 0000 UTC 27 May (1800 MDT 26 May) 2018.

The closed low drifts slowly eastward through the Memorial Day weekend.  By 1200 UTC 28 May (0600 MDT Monday), the low is centered over northwest Utah.

NAM 700-mb temperature (color contours), 500-mb geopotential height (black contours), and 3-hour accumulated precipitation (color fill) forecast valid 0000 UTC 27 May (1800 MDT 26 May) 2018.

By and large, I don't think this is a disastrous forecast for the weekend.  This is not an especially cold trough, although we will see a cooling trend through the period.  It is also not going to produce widespread rainfall, although there are going to be showers and thunderstorms (more on where in a minute) and the possibility that a persistent rainband gets going that might prove to be a real annoyance for a few hours if it sets up right over your location of interest. 

Forecasts from the SREF illustrate where precipitation is most likely for the period through 1800 UTC (Noon MDT) Monday.  Precipitation odds are lowest in southeastern Utah.  Northern Utah has higher precipitation odds, including a small number of ensemble members generating more than an inch of precipitation in a few regions. 

The plume for the Salt Lake City International Airport shows most members generating less than 0.2" of precipitation, but one member puts out 0.7".  Thus, while heavier precipitation isn't likely, it could happen if there's a strong thunderstorm or a slow moving precipitation system parks over you.

Bottom line: Tomorrow is probably the day for long-duration outdoor activities in northern Utah, with a mindful eye on how things evolve late in the day and in the evening.  While there is a chance of showers the rest of the weekend, keeping an eye on the forecast and the radar should allow you to get most activities in, provided that you're not skunked by a slow moving area of precipitation or thunderstorm. 

A quick reminder that lightning is Utah's top weather-related killer.  When thunder roars, head indoors.  Tents and awnings provide no lightning protection.  Move to your car or RV if you are camping.  If caught in a storm hiking, move quickly to lower terrain (avoiding areas that might pose flash flood threat), avoid large trees, crouch low on the balls of your feet, and spread your group out.