textproduct: Salt Lake City

KEY MESSAGES

- Record warm temperatures will continue through Thursday.

- Wind gusts in excess of 45 mph will continue across western Utah through at least Thursday afternoon.

- Very heavy rain across southwestern Utah Wednesday evening into Thursday morning will continue to cause enhanced runoff, with all streams, slot canyons, and other waterways running high.

- A general 6 to 12 inches, with locally up to 20 inches for the upper Cottonwoods and Bear River Range can be expected Friday through late Saturday across the higher terrain of Utah.

- There is a 40 to 50 percent chance of measurable snow for valley floors of northern Utah Saturday night into Sunday morning.

DISCUSSION

A prolific southern Sierras landfalling atmospheric river event continues across southwestern Utah. Some notable storm totals thus far: 4.44" Forsyth Burn Scar sensor, 3.40" Gardner Peak SNOTEL, 3.53" I-15 at MP 37, 4.10" SUU Ranch SNOTEL, 2.74" Lava Point RAWS. Rivers are running much higher than normal, with the mainstem Virgin River, North Fork of the Virgin River, Santa Clara River from near Pine Valley to Baker Reservoir, Coal Creek all showing significant rises. While mainstem river flooding is not expected, all area rivers, streams, creeks, normally dry washes and slot canyons will be running high through much of the day today and potentially into early Friday. Do not drive across flooded roads!

Early morning satellite and upper air analysis indicates a cold upper level low and associated trough remain off the California Coast. This system will become quite messy at landfall, with the northern portion splitting and shifting east across Montana and the southern split shifting across southern California and gradually being absorbed into the northern split as the trough digs into the Interior West Saturday.

Temperatures have already reached record levels this morning, with KSLC tying the record high for the date at midnight. Expect many temperature records to fall once again through the day today...but today is the last day of record warmth for the Beehive State.

For today, expect moderate to heavy precipitation to gradually shift toward a more showery mode across southwestern Utah through around 15Z Thursday. A lull in any organized precipitation is expected this afternoon into this evening.

As the cold front associated with the northern split crosses into northern Utah Friday afternoon, a much more typical for winter airmass will shift into the region. An organized, somewhat frontogenetic band of precipitation will shift across the region with this front, reaching the Wasatch Front by Friday evening. Depending on how quickly snow levels fall, there is about a 10-15% chance rain will change to snow to valley floors across the Wasatch Front by Saturday morning. Given exceptionally warm antecedent conditions, any snow will likely struggle to accumulate on any surfaces.

HOWEVER...

The second part of this system is expected to bring another round of precipitation through northern Utah Saturday night into Sunday morning. This will be associated with much colder temperatures (perhaps as cold as -16C at 700mb) and potential for some lake enhanced precipitation. This has increased the threat of measurable snow for the valley floors of northern Utah to around 40-50% overnight Saturday night into Sunday morning. Current forecast has around a 0.2-0.3 inches of snow at KSLC, with up to 4 inches for the benches. So while the probability of measurable snow is lower than it has been for Saturday morning, this second shortwave trough has really increased the chance we don't make it past this weekend without measurable snow.

Winter weather advisories continue through Thursday evening for the southern mountains and western Uinta mountains. Additional winter weather advisories are now in effect for all the mountains of Utah Friday into at least Saturday evening. Will need to monitor the Wasatch Back for potential addition to the going advisories.

Wind Advisories continue for most western valleys except the Tooele Valley, where a High Wind Warning is in effect. Day shift will need to monitor whether there is enough threat to keep wind advisories going through Friday...as guidance has reduced the wind gust potential, with only a few pockets of probability greater than 30 percent for gusts over 45 mph.

Looks like the weather will give us a break for most of next week.

REST OF UTAH AND SOUTHWEST WYOMING

Precipitation will likely continue through ~16-18z across much of the forecast area, with only a few isolated mountain showers developing during the afternoon. Still, with any remaining precipitation, brief periods of MVFR VIS are possible within any heavier showers. Gusty southerly to southwesterly winds will persist, similar to the past several days, with the highest gusts of 30-40kts expected across western valleys. Localized areas may see even higher winds, such as KTVY.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Wind Advisory until 5 PM MST Friday for UTZ101-115-122.

High Wind Warning until 8 PM MST this evening for UTZ102.

Winter Weather Advisory from 11 AM Friday to 5 AM MST Sunday for UTZ110>113.

Winter Weather Advisory until 11 PM MST this evening for UTZ112- 125.

Winter Weather Advisory from 5 PM Friday to 5 PM MST Saturday for UTZ125.

WY...None.