textproduct: Salt Lake City

KEY MESSAGES

- An isolated flash flood threat will persist over southeast Utah to start the week as monsoon moisture lingers.

- Breezy winds will develop once again on Sunday ahead of an approaching cold front, bringing wind gusts to 40 mph to portions of western Utah as well as Uinta county, Wyoming.

- The front will move through the northwestern half of the forecast area late Sunday into Monday, bringing noticeably cooler and drier conditions behind it. Warmer temperatures and elevated moisture will persist over southeast Utah.

DISCUSSION

Continuing to see southwest flow over Utah and southwest Wyoming this evening between weak ridging centered near the Utah/Idaho border and a closed low over the Pacific Northwest Coast. In this flow, moisture remains elevated over southern and eastern Utah, with satellite derived PW values in the 0.7 to 0.9 inch range, with a dry tongue dropping PWs into the 0.4 to 0.6 inch range over western Utah. The elevated moisture and a bit of shortwave energy allowed for the development of isolated showers and thunderstorms over eastern Utah, including a couple of strong to severe cells during the early evening in Castle Country. Temperatures remain on the high side, with maxes having run 5-10F above seasonal normals across the area.

The Pacific Northwest system is expected to be on the move tonight into tomorrow, with its center approaching Montana by the early evening. The trough is expected to just graze the area Sunday evening into Monday, dropping a mostly dry cold front through. Guidance indicates it will push through the northwestern half of the state through Monday morning before stalling and weakening. Ahead of the front, winds will pick up further across the forecast area, with a decent chance of gusts to 40 mph during the afternoon for western Utah as well as Uinta county, Wyoming. The lingering moisture should also bring a few more showers and thunderstorms to southeast Utah, but overall instability looks a bit more limited than today.

For Monday, the drop in temperatures from the front will be quite noticeable over northern Utah and southwest Wyoming, with maxes running up to 10F below seasonal normals, bringing a taste of fall, along with further drying of the airmass. Ahead of the boundary, however, the decrease in temperatures is only expected to be a few degrees, with the deeper moisture remaining in place over southeast Utah, allowing for another round of showers and thunderstorms capable of producing heavy rain that could lead to isolated flash flooding.

As the Pacific Northwest trough ejects to the east by Tuesday, the forecast becomes a bit murkier. With the flow most likely to stay westerly to southwesterly, it is looking increasingly likely there will not be much change in the moisture profile through at least midweek, with the deeper moisture remaining over southeast Utah as the remainder of the area stays drier. With the rebuilding of high pressure looking less likely, northern Utah and southwest Wyoming temperatures are expected to rebound modestly for Tuesday, with maxes staying around 5F below seasonal normals for much of the remainder of the week. A subset of guidance continues to show the possibility of a trough returning to the Great Basin for the latter half of the week, with many other solutions showing a quieter pattern.

AVIATION

KSLC...South winds will prevail through the overnight period at KSLC, with winds becoming increasingly gusty after 06-07Z. After around 08Z, peak gusts may be upwards of 25-30kts from the south. These winds are expected to remain in place into the early/ mid- afternoon, taking on a slight southwest component before switching to a northwest flow following a cold front. VFR conditions will be maintained through the period.

REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions are expected to prevail across the airspace throughout the valid TAF period. Winds will remain gusty out of the south to southwest across much of the western half of Utah and southwest Wyoming through the overnight hours, with the strongest gusts expected on the lee sides of terrain features. Gusts may reach upwards of 30kts across the central Wasatch Front and southwest Wyoming overnight. Breezy southerly winds remain in place through the early afternoon tomorrow before a cold front sweeps across the northern area and brings a shift to northwest winds.

FIRE WEATHER

Drier conditions will persist over much of the area over the next few days, though monsoon moisture will continue to linger over southeast Utah, bringing isolated showers and thunderstorms each afternoon, with gusty outflow winds and brief heavy rain the primary threats. Southerly winds will continue to strengthen tomorrow ahead of an approaching cold front, with a decent chance of gusts to 40 mph for western Utah. The mostly dry front will pass through the northwestern half of the state late Sunday into Monday, bringing much cooler temperatures and further drying. The moisture will continue to persist over southeast Utah ahead of the front, however. Northern Utah temperatures are expected to rebound Tuesday, with maxes then expected to average around 5F below seasonal normals for much of the upcoming week.

SLC WATCHES/WARNINGS/ADVISORIES

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