textproduct: Salt Lake City

KEY MESSAGES

- Dry and mild westerly flow will prevail across the region Thursday through Friday.

- Locally critical fire weather conditions may return to portions of southern Utah Saturday and Sunday afternoons.

- Temperatures will drop to around 10 to 20 degrees below normal Sunday into Monday as a cold storm system moves through the area. Accumulating mountain snow is possible across the northern mountains.

- Freeze conditions will impact most Utah valleys outside the Wasatch Front Monday and Tuesday mornings, and even as early as Sunday morning in the Cache Valley and Wasatch Back. Some areas may see another hard freeze including the Cache Valley, Wasatch Back, west central and southwest Utah and the Sanpete Valley.

DISCUSSION

Mostly clear skies can be seen on satellite early this afternoon, with just a few cumulus buildups over the southern mountains. Largely dry, quiescent conditions will continue today and tomorrow, with high temperatures lower than yesterday, near to just above normal for mid-May.

As cyclonic flow slowly redevelops across the region, conditions will become a little more interesting again, with a subtle shortwave trough bringing isolated to scattered mountain showers on Saturday afternoon, alongside some increased southwesterly flow. This may result in chances for critical fire weather conditions on Saturday afternoon (see Fire Weather section for more details).

Cold air will gradually usher into the region with a very diffuse cold front moving through Sunday into Monday morning as the parent trough swings across the state Sunday night. More stratiform precipitation will develop Sunday into Monday, with the heaviest during the overnight hours. With 700-mb temperatures dropping to -5C to -7C by Monday morning, snow levels could drop to as low as 5000-6500ft. There is still a very wide spread in potential snow amounts, particularly as large uncertainties remain in the large- scale pattern on Monday and beyond. On the low end (75% chance of exceedance), favored areas such as the Upper Cottonwoods and the Uintas may receive only around 1-4 inches of snow, with higher end amounts (25% chance of exceedance) of 8-14 inches of snow. Models have trended higher, though keep in mind that wide uncertainty still remains in the pattern which could trend amounts in the other direction, too.

Another aspect to this cold storm is the return of freezing temperatures across many valleys in Utah, primarily outside of the Wasatch Front and far southern Utah. Freezing temperatures may return as early as Sunday morning across the Cache Valley and Wasatch Back, expanding to more valleys for Monday-Wednesday mornings. Some areas could dip quite low into the low-20s, particularly early Monday morning.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions with clear skies will persist through the TAF period. Winds will remain predominantly light and diurnally driven, aside from typical westerly gustiness at EVW.

FIRE WEATHER

A cooler and more stable airmass is building over Utah this afternoon, with the greatest cooling observed across areas north of I-70. Conditions will stay dry and becoming increasingly mild through Saturday, with highs peaking at 5F above normal for this time of year. Winds will pick up Saturday afternoon ahead of the next approaching storm system, and these breezy winds could combine with the dry conditions to produce locally critical fire weather conditions. The storm system, quite unseasonably cold, will cross the area Sunday into Monday. Temperatures are expected to drop to up to 20F below seasonal normals by Monday morning. Snow levels are forecast to drop to as low as 5000 feet by Monday morning, with up to six inches of snow possible for the highest elevations of the northern mountains. Accumulations look to be far less over central and southern Utah. Drier conditions are then expected to follow Tuesday behind the front, with generally dry conditions persisting through next Thursday.

SLC WATCHES/WARNINGS/ADVISORIES

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