textproduct: Salt Lake City

KEY MESSAGES

- Mild temperatures with highs around 10 to 15 degrees above normal will persist through Friday.

- A broad system approaches the area Friday into Saturday, resulting in increasingly gusty conditions Saturday. There is a 40-50% chance of wind gusts in excess of 45 mph across portions of Utah's West Desert Saturday afternoon.

- Unsettled conditions return Saturday, initially bringing periods of rain and thundershowers as well as high elevation snow. A colder system will reinforce widespread precipitation chances, lower snow levels, and bring a period of more substantial mountain snow.

DISCUSSION

Visible satellite this morning shows some high clouds filtering through overhead, working around the periphery of the ridge extending through the Great Basin. A very weak boundary will be draped into portions of southern Utah as a result of a departing grazing type system. With little to no moisture available, not really anticipating shower activity from it this afternoon, but likely some cumulus development off the terrain at least. Otherwise, biggest change from yesterday is just highs across northern Utah and southwest Wyoming running a degree or two lower than yesterday, and at areas further south a degree or two warmer. Overall though, temperatures areawide remain well above seasonal normal for this time of year.

Anomalous warmth will continue to build through Friday, with temperatures day to day increasing a degree or two. In general, expect afternoon highs around 10-15 degrees above normal. On Thursday the combination of whatever remnants exist of the aforementioned weak boundary with daytime heating and some modest energy advecting overhead within southwest flow will trigger some isolated to scattered afternoon showers/t-storms. These will be most focused over the northern high terrain. Friday will also see some afternoon shower development as midlevel heights fall and a Pacific trough begins to push inland along the Pacific coast.

Saturday will mark the start of a more pronounced pattern shift as a broad Pacific trough advances further inland. Within the increasing southwesterly flow, 700 mb winds push more into the 35-45 kt range or so. While cloud cover may limit mixing to some extent, any downward momentum transfer either from thermal mixing or precipitation will bring potential to see gusty winds realized at the surface. The best odds of seeing wind gusts in excess of 45 mph is currently across portions of Utah's West Desert (around 40-50% chance), with more modest gusts anticipated elsewhere around the region.

Additionally on Saturday, increasing forcing and ample moisture will result in increasing precipitation chances. PWATs for example will be around 100-150% of climatological normal, with some higher pockets at areas of southern Utah. Models also support some level of destabilization Saturday, with mean SBCAPE generally on the order for 100-300 J/kg. In addition to more widespread shower activity, this will support the development of thunderstorms, especially across portions of southern Utah. What little CAM guidance is available already shows some semblance of more spring like convection. With the PWATs and instability, may need to keep an eye on rain sensitive areas such as burn scars, typically dry washes, slot canyons, and slickrock areas.

The majority of deterministic models and ensemble members then continue to support the pattern evolving such that another shortwave digging southward from the PacNW will further deepen the broader trough, allow a tap of colder air to be established, and subsequently pushing a cold front through the area locally. Timing still favors the Sunday/Monday time frame, though spread is still noted in exact timing, trough depth/strength, and just how cold the corresponding airmass is. Models do at least continue to favor good moisture transport, with the NBM still indicating around a 20-40% chance of water in excess of 1" for most of Utah's mountains. Snow levels ahead of the front will likely be around 8500 feet or so, but decrease behind the front and fall closer to 6000 feet. As such, will see favorable chances of some accumulating mountain snow. Given the aforementioned uncertainty, accumulation amounts are still in flux, but current probabilities suggest about 40-60% chance of 6" or more for most of Utah's mountains. These amounts increase at northern areas, with around a 50-70% chance of 12" or more in the Upper Cottonwoods and Western Uinta Mountains. Ultimately, will have to continue to watch the trends. With colder temperatures behind the front, there will also be some potential for areas of freezing temperatures where the agricultural growing season has already started, but given uncertainty in just how cold the airmass is, low confidence on the exact chance or areal extent this far out.

REST OF UTAH AND SOUTHWEST WYOMING

Winds will remains light outside of some terrain driven higher winds. VFR throughout the period with just FEW to SCT mid to high clouds if not SKC.

SLC WATCHES/WARNINGS/ADVISORIES

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