Slight Relief from Wimpy Trough

A weak trough is pushing into northern Utah this morning, bringing in slightly cooler air and just a bit of relief from our recent run of hot weather.  

MesoWest observations this morning show northwest to northerly flow across northwest Utah, especially along I-80, over the western and northern Great Salt Lake, and along the Utah-Idaho border.  

Source: Mesowest

Time series from milepost 29 along I-80 show a wind shift, increase in dewpoint and humidity, but virtually no drop in temperature with the trough passage.

Nevertheless, there is a slight decline in temperature over the 24-hour period, so there is a very slight transition to a cooler airmass.

The HRRR calls for winds in the Salt Lake Valley to shift to NW this afternoon.  This is consistent with both the approaching trough and the usual development of afternoon up-valley flow and lake-breeze effects.  The trough is so weak that it is difficult to entangle these forcing agents.  Perhaps we'll see slightly enhanced northwest flow this afternoon.  

By late afternoon, northwesterlies have penetrated to the southern Salt Lake Valley and into the central Wasatch north of Little Cottonwood and upper Big Cottonwood.  

Firefighters in Parley's canyon will surely be briefed on and alert for this wind shift.  One positive is that the winds are not strong, but are forecast to be around 10-15 knots.  

With the slightly cooler airmass, highs today should be in the low 90s (the NWS forecast for KSLC is 91˚F).  Should that verify, it would be our lowest maximum since July 22nd when it reached only 85˚F.  Since then, we've reached 92 or higher every day, with seven days reaching 100 or more.