textproduct: Salt Lake City

KEY MESSAGES, Issued 134 PM MDT Sat Sep 5 2026

- Gusty winds out of the southwest persist through at least Sunday across much of Utah and southwest Wyoming, with an emphasis on areas west of I-15.

- Tropical moisture advects north into Utah Sunday increasing chances for precipitation.

- Threats for both flash flooding and isolated severe weather look to develop on Sunday with the arrival of tropical moisture.

- The active upper air pattern continues into next week (50-60% chance), potentially resulting in more precipitation by mid-week following an early week lull.

DISCUSSION, Issued 134 PM MDT Sat Sep 5 2026

Similar to yesterday, a large upper low continues to slowly move into the Pacific NW, deepening with eastern extent. A tight southwest-northeast oriented pressure gradient remains in place across nearly all height levels resulting in another afternoon of enhanced southwesterly flow overhead. With another clear and dry afternoon where daytime surface heating is favorable, elevated winds are forecast to mix to the surface yielding gusty conditions through much of the afternoon statewide. Most areas across UT and SW WY can once again expect to see gusts in the 25-35mph range, though areas west of I-15 may see gusts approach (and potentially exceed) 45mph given stronger winds aloft with higher surface temperatures to encourage stronger mixing. This general pattern is expected to continue into Sunday with enhanced afternoon southwesterlies developing around the 10AM-12PM timeframe each day, though a slight decrease in magnitude is expected Sunday given preceding cloud cover which may inhibit mixing for areas east of I-15.

Come Sunday, moisture associated with Hurricane Marie is forecast to phase into the mean upper flow as as the southern stream pushes north and increases in magnitude. PWAT anomalies on the order of 0.5- 0.8 above seasonal normals (potentially exceeding 200% normal values) are forecast to push north across much of Utah with this increase in southwesterly flow. Widespread ascent will overspread as the strengthening southern stream phases into the mean flow with the aforementioned upper low, with a quick eastern progression of the main precipitation axis through the afternoon hours. As such, widespread showers and thunderstorms are forecast to develop in the morning hours across much of southern and central UT, potentially nudging into northern UT as well. Despite enhanced flow aloft suggesting fast moving storms, robust moisture content within the atmosphere continues to yield concern for flash flooding across central and southern UT, where a slight risk (level 2/4) for excessive rainfall has been outlined by the Weather Prediction Center (WPC). Current guidance suggests hourly rainfall rates ranging from 0.4-0.6"/hr, with some isolated rates nearing 0.6- 0.8"/hr rates possible.

Regarding the severe threat, it appears to have become more isolated in nature given ample cloud cover from the morning hours into the afternoon resulting in a stable layer across much of the state. Ample shear exists on the order of 40-50kts, though only modest buoyancy develops in the midst of persistent cloud cover and moist boundary layer with robust convection likely struggling to develop in the afternoon hours. If any stronger convection were to develop, the most probable locations would be far northwest UT where frontogenetic forcing is forecast to be strongest, and perhaps southeast UT where a mid-level impulse is forecast to traverse in the afternoon hours, particularly along Castle Country. The main hazards will be isolated gusts to around 58mph and instances of sub- severe hail less than 1".

Come Monday and Tuesday, the upper low progresses east leaving the forecast area in a dry westerly flow regime keeping conditions calm to start the week. On Wednesday, ensemble guidance has come to better agreement with roughly 50-60% of all ensembles supporting moisture return in some capacity to UT. However, all members within cluster guidance support moisture return in some capacity through the remainder of the week, resulting in timing being the only uncertainty with this forecast rather than *if* moisture will return.

AVIATION, Issued 134 PM MDT Sat Sep 5 2026

KSLC...Southerly winds will continue at the SLC terminal through the day. Southerly winds will continue overnight, increasing once again Sunday morning around 13-15Z.

REST OF UTAH AND SOUTHWEST WYOMING...Breezy southerly winds will continue to impact most terminals through 02-03Z this evening. An area of showers and embedded thunderstorms will move into far southwestern Utah around 12Z and quickly shift north and east through the morning. Expect occasional MVFR conditions in heavier rain.

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FIRE WEATHER

Moisture will continue to gradually increase into sunday as southwesterly flow pushes moisture further north. This afternoon, expect locally critical fire weather conditions primarily across the West Desert and Great Salt Lake Desert where humidities have been observed dropping below 15%. Additionally, strong wind gusts across areas primarily west of I-15 will range from 30-45mph each afternoon into Sunday.

On Sunday, a stronger push of moisture arrives to Utah with widespread showers and thunderstorms across the state, though primarily across central and southern Utah. The highest rainfall totals are expected across higher terrain of central and southern Utah, though lower elevation areas further east may see higher isolated totals from stronger storms. For lower lying areas west of I-15, generally a trace or less of precipitation is expected on Sunday. A drying trend is expected to develop Monday and Tuesday with more precipitation expected after midweek next week across at least southern and central Utah.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Flood Watch from Sunday morning through Sunday evening for UTZ113-114-116>120-122-124>128.

WY...None.