Sunrise 6:13 AM   Sunset 8:08 PM Moonrise 1:55 AM   Moonset 11:50 AM

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FXUS65 KSLC 011029 AFDSLC

Area Forecast Discussion National Weather Service Salt Lake City UT 429 AM MDT Wed May 1 2024

SYNOPSIS
A cool but relatively stable airmass will reside across much of Utah and southwest Wyoming today, as a cold front moves away from the region. A relatively cool and unsettled pattern will persist through the remainder of the week, with the next weather system affecting northern Utah and southwest Wyoming Thursday night into Friday.

.SHORT TERM (Through 00Z Saturday/6PM Friday)...A shortwave trough evident in satellite imagery and objective analysis is digging through the northern Rockies and northern Great Basin early this morning. A stalled frontal boundary continues to bisect the area, and extends roughly along a Cedar City to Green River line. As the upper jet associated with the shortwave trough interacts with this boundary, scattered showers have developed along the cool side of the boundary and will likely continue into the morning hours.
Meanwhile a secondary surge of cold air associated with this trough is currently spreading into northern Utah. This colder air will continue to push south, effectively re-enforcing the stalled frontal boundary this morning before the boundary pushes southeast through the remainder of the area this afternoon. The focus for showers will shift into areas from roughly Capitol Reef eastward this afternoon, before exiting the forecast area this evening.

With this colder air overspreading the area, max temperatures across northern/central valleys will trend 4-6 degrees cooler today, running in the low to mid 50s along the Wasatch Front which is roughly 10F below climo. Meanwhile max temps across southern Utah behind the front will trend 4-8 degrees cooler than Tuesday.
With this cooler air mass in place, temperatures will fall near or below freezing across many locations overnight. Although much of the Wasatch Front will remain in the mid to upper 30s, outlying agriculture areas outside of Brigham City as well as more rural portions of Utah Valley will see temperatures approach freezing.
Some question remains regarding cloud cover overnight as the broad flow pattern remains cyclonic, and therefore have held onto the Freeze Watch for these locations. Other forecast zones such as the Cache Valley and central/southwest Utah (excluding St George)
have not yet reached the date for freeze warnings, thus no products are in effect for these areas.

A general cyclonic west to northwest flow will remain across the region through the remainder of the week. The airmass will modify a bit Thursday allowing temperatures to trend 5F warmer for most valleys. A more organized wave within this flow will bring a chance of showers to northern Utah Thursday night through Friday morning with minimal QPF expected. Cooler air associated with this wave will result in little change in temperatures from Thursday to Friday across the north, with a slight warming trend forecast across the south.

.LONG TERM (After 00Z Saturday/6PM Friday)...Clouds will diminish through Friday evening as shortwave ridging tracks across Utah and southwest Wyoming. Temperatures Saturday will start in the 30s and 40s for most valleys. The ridge axis will be east of the area Saturday morning, while an upstream trough will be digging into the PacNW. With the approaching trough and exiting shortwave ridge, flow aloft will increase through the day. Flow at 700 mb Saturday morning will be around 15 knots, but by Saturday evening, 50 knot or higher winds are likely there. Strong warm air advection with dry conditions will allow for a big range in temperatures. Morning lows will be roughly 5-10F cooler than normal. Most valley high temperatures will be into the 70s, roughly 5-10F warmer than normal.
Winds will be strongest throughout western Utah during the afternoon and will stay enhanced into Sunday.

The longwave trough will dig southeast into Sunday. There are timing differences, so uncertainty Sunday when a baroclinic zone will track into Utah. Ensemble guidance ranges from early in the day to late on a north to south oriented cold front. With the timing differences, there is uncertainty if gusty southwest winds would last much of the day or if precipitation would push in with lighter winds. Confidence is better as the day goes for the boundary to track across Utah.
Valley rain and snow above roughly 8000 feet are likely initially.
As colder conditions build in into Monday, snow is likely to roughly 6000 feet. Once the trough axis tracks over Utah, moist, unstable northwest flow will bring more snow to the northern mountains.

Rain and snow will taper off Monday into Tuesday, but ensembles are in good agreement on a shortwave trough quickly tracking in Tuesday with light valley rain and mountain snow.

AVIATION
KSLC...Northwest winds will last through the day with gusts around 20 knots much of the afternoon. Mostly clear conditions to scattered clouds are likely.

REST OF UTAH AND SOUTHWEST WYOMING
A relatively dry cold front will push into southern Utah, transitioning winds to northwest during the morning. West to northwest winds will last through the day throughout southwest Wyoming and Utah, with gusts around 20 knots. Largely dry conditions are likely with isolated mountain showers.

SLC WATCHES/WARNINGS/ADVISORIES
UT...Freeze Watch from late tonight through Thursday morning for UTZ103-106.

WY...None.

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