textproduct: Salt Lake City

KEY MESSAGES

- Isolated showers and thunderstorms will impact from roughly I-70 to a line roughly north of Cedar City to north of Bryce Canyon to north of Bullfrog as well as the Raft River Range and the higher terrain of northern and central Utah Saturday afternoon and evening.

- There is a 20-30% chance for southerly winds to gust in excess of 45 mph across a portion of western Utah on Tuesday, and upwards of a 60% chance on Wednesday for a broader area.

- Locally critical fire weather conditions due to strong wind and low humidity will occur across portions of southern Utah as early as Tuesday in areas where fuels are critically dry.

DISCUSSION

This morning's satellite imagery reveals building low-level cloud cover primarily over the mountainous terrain in central/ southern Utah, with indication of mid/high-level cloud cover draped over a portion of northern an southern Utah. As Utah remains in a relatively unsettled quasi-zonal flow pattern, this little bit of moisture will help to provide a touch of mid-level instability, allowing for continued chances for isolated showers and thunderstorms over a portion of the forecast area. Given the observed and modeled location of the moisture, thinking that the low end threat for these showers and thunderstorms will be (in general) for an area that extends from Cedar City northward to the I-70/I-15 merge, and from the Capitol Reef region westward to the Nevada border. Given how dry the lower level environment appears, flash flooding will be unlikely. Additionally, the lack of shear and deep instability will limit any potential for strong/ severe thunderstorms to develop... just your run of the mill showers with a chance for a rumble of thunder.

Sunday will bring more or less the same general setup with chances for showers and isolated thunderstorms increased to around 15-30% across northwest Utah, as well as the high Uinta Mountains. Chances will be generally less than 15% in the southern/ central areas. Otherwise, anticipate temperatures to warm by another 2-4 degrees across the northern area with little change in the south as a ridge axis lifts into the region during the late morning and afternoon hours on Sunday.

This broad, loosely defined ridge will remain a dominant weather feature over the region through Monday, bringing further warming of the environment. Peak temperatures for the next 7 days are expected by Memorial Day as a result, with highs reaching 7-12 degrees above normal across the north and 0-5 degrees above normal in the south. Moisture streaming into the area on the western periphery of this ridge will help to increase chances for showers and thunderstorms on Monday afternoon, primarily in the high terrain and adjacent valley areas across southern, central, and northeastern Utah. Lower level moisture still appears to be lacking by Monday which will likely limit widespread heavy rainfall potential.

After Monday, models maintain solid agreement on an anomalous upper level low dropping out of the PacNW region and into the Great Basin Tuesday forward. Anomalously warm temperatures and dry conditions ahead of this low will help set the stage for potential fire weather conditions across a portion of Utah from Tuesday onward as winds increase out of the south. Ensemble probabilities for wind gusts greater than 45 mph have decreased for Tuesday, showing a low probability (20-30% chance) of gusts exceeding 45 mph over western Utah. That said, guidance is still in support of a moderate probability (40-60% chance) of wind gusts exceeding 45 mph on Wednesday afternoon and Thursday afternoon as this low lingers to our west. There are still some uncertainties to work through with the position of this low which will influence how much, if any, precipitation we see across the area.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions will persist for the entire airspace through the period. Dry conditions with some mid level clouds will continue with winds relatively light and diurnally driven.

FIRE WEATHER

Isolated showers and thunderstorms are expected to develop across a portion of central/ southern and northwest Utah this afternoon, primarily over the high terrain. There is a low chance that these showers produce a wetting rain as surface moisture is inadequate. Otherwise, temperatures will remain anywhere from 4-10 degrees above average alongside minimum humidity in the 10-20 percent range.

Continued warming is expected through Monday as an area of high pressure builds into Utah, with highs reaching upwards of 8-12 degrees above normal in the northern area and 1-5 degrees above normal in the southern area. Humidity will increase by around 5 percent across northern Utah heading into Sunday as chances for showers and isolated thunderstorms increase, then dry again by 5-10 percent on Monday while southern Utah will experience little in the way of change. An area of low pressure is expected to push into the Great Basin from Tuesday forward, bringing an increase in southerly winds. For at least Tuesday, elevated to critical fire weather conditions are anticipated to develop across a portion of western, southern, and eastern Utah during the afternoon hours. There is higher confidence that elevated to critical fire weather conditions persist in eastern Utah through the mid to late week.

SLC WATCHES/WARNINGS/ADVISORIES

UT...None. WY...None.