textproduct: Salt Lake City

KEY MESSAGES

- High pressure will result in dry and unseasonably warm conditions through early Tuesday.

- A warm Pacific system brings rain and mountain snow generally above 8000 feet to northern Utah Tuesday through late Wednesday. - High pressure is expected to move back in Thursday, with dry and mild conditions persisting through at least the first half of the weekend.

DISCUSSION

Another dry and mild day is on tap across the region today as high pressure persists across the western US. High temperatures running around 10 degrees above seasonal averages are expected areawide as a result.

A landfalling atmospheric river is expected to bring a shift in the pattern across northern Utah and southwest Wyoming on Tuesday, bringing widespread rain and high elevation snow to the area through Wednesday. An associated stout upper-level jet moves overhead early Tuesday, which will first bring enhanced westerly winds across the region, especially for northern Utah mountains. Recent high-resolution guidance shows an onset of precipitation across far northern Utah beginning around mid- morning Tuesday, spreading south through the day as the jet slowly sags southward. Lift maximizes over northern Utah late Tuesday into early Wednesday as the jet max moves overhead, which will result in a period of high precipitation intensity. Strong warm air advection is also expected during this period, which will result in rapidly increasing snow levels. Snow levels beginning around 6500 feet at the onset of precipitation will climb to around 8000 feet by Tuesday afternoon, maxing out around 8500-9000 feet early Wednesday morning. As such, snow accumulations will overall remain confined to high elevations across the northern mountains and will limit any travel impacts to slushy conditions across high mountain routes like Logan Summit, the Upper Cottonwood Canyons, and Wolf Creek Summit. The warm nature of this storm also means any snow accumulation will be very heavy and wet. With already dangerous avalanche conditions in place per the Utah Avalanche Center, extra caution is advised for those planning to head into the backcountry.

Precipitation will taper through Wednesday afternoon as an upstream ridge amplifies across the west coast, effectively cutting off our moisture tap. High confidence exists for this ridge to persist through at least Saturday, keeping dry and mild conditions in place through this period. More uncertainty arrives Sunday as a closed low approaches the California coast, with a rough 50/50 spread in ensemble clusters for two different scenarios. The first scenario would see increased southwest flow aloft, allowing modest moisture associated with the low sneaking into northern Utah on Sunday and bringing increased chances for rain and high elevation snow showers. The other scenario keeps the stout ridge parked across Utah, which would maintain the status quo of continued dry and mild conditions.

REST OF UTAH AND SOUTHWEST WYOMING

Diurnally typical winds expected on Monday, with magnitudes light (generally less than 15 kts outside of exposed higher elevation terminals). At southern terminals, anticipate just some SCT VFR cloud cover. At northern terminals an approaching system will result in thickening and lowering VFR clouds Monday into Tuesday night, with further lowering to near mountain obscuration level by morning. Shower chances then begin to increase through Tuesday afternoon, with snow levels generally above 7500-8000 ft.

SLC WATCHES/WARNINGS/ADVISORIES

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