Hairdryer Conditions

Heat, wind, low relative humidity.  Hairdryer conditions are dominating the weather story over northern Utah this holiday weekend.  

Meteograms for the Salt Lake City International Airport (KSLC) over the 24-hour period ending at just after noon today (Sunday, July 3rd) illustrate this well.  Yesterday afternoon, temperatures hovered near 100˚F (the official high was 101˚F) with dewpoints in the mid 20's and the relative humidity below 10%.  Winds gusted as high as 38 mph.  

Today is pretty much a repeat.  

For drying out the landscape, this is about as bad of a pattern as you can have.  

Sadly, the monsoon moisture isn't that far away.  The NAM forecast for this afternoon shows a sharp contrast in low-level relative humidity between western Utah and western Colorado (see lower left panel below), with considerable shower and thunderstorm activity over the latter.  

Both regions are in southwesterly flow.  The difference is origin.  In western Utah, our flow is moving around the upper-level low off the Pacific Northwest Coast and originates in the dry belt over the eastern Pacific.  In contrast, in western Colorado, the flow is moving around the upper-level ridge centered over the southern Plains and originates over the Gulf of Mexico.  The confluence of these two airstreams creates a sharp contrast in weather.  This is a common pattern during the monsoon and one of the reasons why eastern Arizona, New Mexico, and Colorado are more active than northern Utah.  

Your best option for this weekend is to stay in the shade or at high elevation, drink a lot of water, and don't play with fireworks.