Helper, UT 84526 Weather

Key messages

- After a relative lull in precipitation on Saturday, an atmospheric river will interact with a strong cold front Sunday into Monday, resulting in widespread moderate to heavy precipitation across the region. This will increase the potential for flash flooding on Sunday across southern and eastern Utah.

- Accumulating mountain snow is expected Sunday night through early Monday as colder air spreads into the region. Local snowfall totals above 8000 feet may exceed 12" across areas favored in northwest flow.

- Cool, dry and stable conditions are expected Tuesday into Wednesday, before a more active pattern returns later next week.

Discussion

Utah and southwest Wyoming remain under a south to southwest flow this evening which has brought unseasonably high moisture to much of the area, particularly over southern Utah. Satellite derived PWs are in the 0.6 to 0.8 inch range over southern Utah and 0.3 to 0.5 inch elsewhere. This allowed for good coverage of showers today, particularly along a line extending from southwest Utah through the Wasatch Front where some embedded shortwave energy moved through.

The remaining shortwave energy with exit to the north tonight, taking some of the moisture with it. This will result in a relative lull in precipitation on Saturday with just some scattered showers around. High temperatures are expected to stay near seasonal normals across northern portions of the area, but in excess of 5F below climo over southern Utah where more cloud cover is expected.

Confidence remains high that ingredients will come together to bring widespread valley rain and mountain snow to Utah and southwest Wyoming Sunday into Monday. Southerly flow will bring up moisture from a landfalling atmospheric river as a strong and progressive Pacific storm system tracks across the state. With this high amount of moisture and instability, rain will be heavy at times, creating a rather heightened potential for flash flooding, particularly for southern Utah. Going Flood Watch covers this threat well.

As the strong cold front moves through, snow levels are expected to lower from 9,000 feet to as low as the 6,500 to 7,000 foot range, bringing accumulating snow to all of Utah's mountains. These totals could be significant, particularly for areas favored in northwest flow, and this has the potential to bring travel difficulties to higher elevation routes.

The trough is expected to exit the area Monday morning, with just a few mountain showers expected to linger into Monday afternoon. Temperatures will be quite unseasonably cool, with maxes averaging 10-15F below seasonal normals. Weak transient high pressure is then expected to keep conditions dry for Tuesday, but most guidance shows this being quickly pushed out of the way by yet another Pacific trough Wednesday into Thursday, with an active pattern then continuing through at least day seven. Ensemble spread remains high with regard to the timing, strength, and track of these individual systems so confidence is low with regard to potential impacts, but relatively high in the continued unsettled pattern.

Hydrology

Through Sunday night: additional rainfall, locally heavy across southern Utah, will once again bring elevated potential for localized flash flooding and widespread rises to area waterways in southern and portions of central Utah. The most significant period of precipitation is expected on Sunday.

Earlier precipitation brought areas of flooding to portions of southwest Utah. However, coverage has decreased this evening. A relative downtick in heavy rain potential exists for Saturday, but the primary precipitation producer will be moving into the area Sunday. The broad upper trough off the Pac Coast is expected to phase with a strong short wave embedded within a strengthening southern tier jet. Anticipated set-up will allow a land falling atmospheric river (AR) to penetrate inland into southern/central Utah producing widespread moderate to locally heavy rainfall across the Arizona strip, Grand Staircase, and southern/central mountain regions, including National Parks and Recreation Areas within these areas. Rainfall amounts of 1-2.5" are likely with this, and given antecedent conditions, will efficiently runoff the landscape promoting widespread rises for all waterways, including streams, creeks, normally dry washes, slot canyons, and rivers across the region.

.AVIATION, Issued 952 PM MDT Fri Oct 30 2026:

KSLC: VFR conditions are forecast to prevail through the TAF period, though mountain obscurations are forecast to continue through much of the period as well. Winds will largely remain southerly through the period as a system approaches the region. Occasional bouts of -SHRA are expected through 00-06z, followed by persistent -RA.

REST OF UTAH AND SOUTHWEST WYOMING: Showers are forecast to continue becoming more isolated through the overnight, then quickly returning in the morning hours across southern UT before overtaking the remainder of UT/SW WY in the afternoon. Conditions will largely remain VFR with mountain obscurations at all sites through the TAF period. Winds will generally remain south-southwesterly as a system approaches the area.

Watches, warnings and advisories

UT: Flood Watch from late Saturday night through Sunday evening for UTZ120-121-123>125-127>131.

WY: None.