Brighton

000
FXUS65 KSLC 301759
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
1159 AM MDT Fri Oct 30 2026

.KEY MESSAGES...

- Tropical moisture will fuel showers and thunderstorms through
  this evening across much of Utah. Locally heavy rainfall may
  lead to flash flooding, particularly across southwest Utah.  

- 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...

A longwave trough resides along the Pacific Coast late this 
morning, anchored around an upper low spinning off the WA/OR 
coastline near 130W. A shortwave trough is noted ejecting through 
the lower Colorado River Valley, and is pulling an anomalously 
moist airmass into the Desert Southwest/southern Great Basin. 
Meanwhile an Atmospheric River (AR) is noted along the base of the
longwave trough near 20N. This initial shortwave passage today, 
followed by the main upper trough late Saturday night through 
Sunday, will bring 2 rounds of heavy precipitation across southern
and eastern Utah. The first round this afternoon/evening will be 
more convective in nature, while the second round late Saturday 
night into Sunday associated with the inland-penetrating AR will 
be predominantly stratiform. See the Hydrology section below for 
more details on the heavy rain and flood potential through Sunday.


As the initial shortwave ejects northward, ongoing convection 
across southwest Utah into northern AZ will lift into central and
eventually northern Utah later this afternoon through this 
evening. In the wake of this feature, lingering moisture will
maintain a chance of showers and isolated thunderstorms Saturday,
however with the forecast area remaining between today's ejecting
shortwave and the approaching longwave trough axis, large scale 
forcing will remain limited which will keep convective coverage
isolated to perhaps scattered in nature.

As the upper low off the Pacific NW coastline begins its eastward
progression late Saturday, the aforementioned AR will spread
inland around the southern end of the Sierra, and into the
southern Great Basin/Desert Southwest Saturday night, reaching
southern Utah by early Sunday. The approaching upper low will
translate through the Great Basin Sunday through Sunday night,
with the combination of the two bringing widespread and
potentially heavy precipitation across the forecast area Sunday 
through Sunday night. Colder air in the wake of the surface-700mb
trough axis will spread into the area late Sunday through Sunday
night, with snow levels falling from 9000+ ft Sunday afternoon to
below 7000 ft by early Monday. This will result in accumulating
high elevation snowfall across the forecast area Sunday night
through Monday morning. Assuming the post-frontal environment
evolves as currently forecast, a favorable orographic setup 
Sunday night into Monday morning looks likely across the upper 
Cottonwoods and other northern/central mountains favored in NW 
flow, where snow totals in excess of 12" are currently forecast. 

In the wake of this system, mid level ridging will bring a cool
and stable airmass into the area through mid-week, followed by
another series of troughs beginning Thursday. Considerable
uncertainty exists regarding how this pattern evolves beyond
Wednesday, thus confidence is low regarding the probability,
timing and coverage of precipitation later next week.

&&

.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, but convection will
bring a localized flash flooding potential to southwestern Utah 
this afternoon and evening. 

A tongue of elevated PWAT advecting north out of western AZ has 
pushed values to near .80" across southwestern Utah this morning. 
Aiding this is the approach of a progressive short wave trough 
ejecting from the broad upper level trough off the Pac Coast, 
which will begin crossing the region from west to east around mid 
afternoon. Ahead of this, noting scattered convective development 
across far southwestern Utah where modest MUCAPE of 400-600 J/KG 
exists, with stronger cells packing 1-2+"/hr instantaneous 
rainfall rates. For much of Washington County, and western Kane 
County, localized flash flooding will remain a potential through 
at least late afternoon where this convection will be most 
focused.
 

A relative downtick in heavy rain potential exists for Saturday, 
but the primary precipitation producer will be moving into the 
area Sunday. The aforementioned 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...

KSLC...VFR conditions are forecast to prevail through much of the
TAF period, though brief MVFR visbys are possible this afternoon 
as showers move into the airspace after 1830-1900z. Chances for 
thunderstorms remain around 15% through 01z. Additionally, 
ceilings will gradually lower through the afternoon, with CIGs 
approaching 6000ft AGL as early as 20z. South winds are expected 
throughout the day, with occasionally erratic winds near showers. 
While the bulk of the shower activity will wind down by 03-04z, 
isolated showers will remain possible overnight.

REST OF UTAH AND SOUTHWEST WYOMING...Widespread showers and 
isolated thunderstorms will continue to overspread the state from 
southwest to northeast through the afternoon, with activity 
winding down after 04z or so. Still, isolated showers will likely 
last into the early morning hours. VFR conditions will largely 
prevail, though MVFR VIS/CIGs are likely with heavier rainfall, 
primarily before 03z. Winds may be briefly gusty and erratic near 
thunderstorms this afternoon, but will otherwise generally follow 
a diurnal pattern.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Flood Watch from late Saturday night through Sunday evening for 
     UTZ120-121-123>125-127>131.

WY...None.
&&

$$

PUBLIC...Seaman
AVIATION...Cunningham
HYDROLOGY...Merrill

For more information from NOAA's National Weather Service visit...
http://weather.gov/saltlakecity