textproduct: Salt Lake City

UPDATE

Overnight hi-res guidance is in strong agreement developing enhanced southerly winds across southwest Utah by mid- morning, then spreading into portions of west central Utah west of I-15 late morning and afternoon. Gusts in excess of 45 mph are likely (80% probability), and there is a 30% chance gusts exceed 60 mph in downslope-prone areas near Cedar City this morning. Given this trend in the models have issued a Wind Advisory for these areas from 15Z this morning until 01Z this evening. Otherwise the general forecast idea remains unchanged. Updated key messages as well as aviation and fire weather discussions are included below.

KEY MESSAGES

- A Wind Advisory is in effect for west central and southwest Utah from mid morning through this afternoon, where southerly winds will gust in excess of 50 mph at times.

- A Red Flag Warning is in effect for portions of south central and southeastern Utah, where gusty south winds and very low relative humidity will result in critical fire weather conditions this afternoon and again Thursday afternoon. This threat may spread northward into the San Rafael Desert region Thursday.

- A low pressure system will bring cooler temperatures Friday into Saturday. Showers and thunderstorms may accompany this system across northern Utah and southwest Wyoming.

- High pressure will bring warm and dry conditions early next week.

DISCUSSION

A broad low pressure system continues to wobble around the Great Basin this evening. The proximity of this low has brought a steep pressure gradient into western Utah, which brought widespread gusts to 40 mph with isolated gusts to 50 mph across the western third of Utah. Winds have started to diminish and will continue to do so this evening. Going Wind Advisory covers the threat well. Earlier showers and thunderstorms brought some periods of gusty winds, primarily for northern Utah, but these showers have also diminished considerably and should not be a threat overnight. Temperatures were on the mild side once again, particularly over northern Utah where maxes averaged 10F above seasonal normals.

The low is expected to pivot slightly eastward for Wednesday into Thursday, and the position of the low will allow drier air to advect in as gusty winds become more widespread across the area, though peak gusts will tend to decrease. This will temporarily suppress shower and thunderstorms development over the area but will bring increasing fire danger, particularly for southeast Utah. See the fire weather section of the AFD for more details.

Eventually, the low will be on the move again, tracking across Utah and southwest Wyoming. The latest suite of guidance continues to trend slower with when the system will move across the area, with the consensus now looking more like Friday into early Saturday as opposed to late Thursday into Friday. The models generally struggle with closed low features, so confidence in timing and overall impacts is lower than usual for this time period. The main impact of the low will be on temperatures, which will drop to values near or just below seasonal normals by Saturday. Anticipating some scattered convective development on Friday, but as the center of the low moves through, showers will become more widespread and focused over northern portions of the area late Friday into Saturday.

The overall consensus in guidance is to bring a slow warming trend for early next week, with most ensemble members showing a trailing system grazing northern Utah late Sunday into early morning. Beyond that, increasingly dry and warm conditions are anticipated through day seven and beyond as high pressure moves in.

REST OF UTAH AND SOUTHWEST WYOMING

Predominant VFR conditions will prevail across the region today. Gusty southerly winds will develop during the 15-16Z timeframe at all TAF sites, and continue through the afternoon. Gusts will likely exceed 40 kts around KCDC by mid-morning, and continue through at least early afternoon.

FIRE WEATHER

An upper low spinning over the western Great Basin of Nevada will remain in place through at least Thursday. With this low parked to the west, a warm, dry and breezy airmass will reside across much of Utah. Very dry air will spread across portions of central and southern Utah east of Highway 89 today with daytime RH values falling to near 10 percent. This combined with these gusty south winds will result in critical fire weather conditions across Zone 494 and eastern portions of zone 498 today and again Thursday. Yesterdays rainfall helped raise fuel moisture further north into zones 489 and 484, where a Fire Weather Watch remains in place for Thursday if fuels can dry sufficiently.

This Nevada low will finally move east and pass through Utah later Friday through Saturday. Cooler temperatures, higher RH, and an elevated chance for wetting rains will accompany this low across the northern half of Utah. Drier air will remain in place across the south. High pressure looks to strengthen across the region heading into early next week resulting and hot and dry conditions areawide.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Fire Weather Watch from Thursday afternoon through Thursday evening for UTZ484-489.

Wind Advisory from 9 AM this morning to 7 PM MDT this evening for UTZ115-122.

Red Flag Warning from noon today to 9 PM MDT Thursday for UTZ494- 498.

WY...None.