Sunrise 6:35 AM   Sunset 8:23 PM Moonrise 1:18 AM   Moonset 10:49 AM

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FXUS65 KSLC 302150 AFDSLC

Area Forecast Discussion National Weather Service Salt Lake City UT 350 PM MDT Tue Apr 30 2024

SYNOPSIS
A cold front will cross the region tonight, bringing additional cooling for Wednesday. Gradual warming is then expected late week into the weekend.

.SHORT TERM (Through 12Z/6AM Thursday)...
Little impactful weather expected through the short term, with temperatures running about 3-6 degrees below normal today, trending cooler to about 5-10 degrees below normal on Wednesday.
The main highlight is the potential (60-75% chance) for sub- freezing temperatures in Eastern Box Elder and Utah Valleys Wednesday night into early Thursday morning, as the growing season begins in those zones Wednesday, May 1st.

A stalled frontal boundary remains in place across central Utah, weakening in place while also starting lift back northward ahead of the next approaching shortwave. That shortwave trough can be seen on WV image moving on the Oregon coast this afternoon, and will continue to track east-southeastward grazing across northern Utah Wednesday.

Ahead of this trough, the surface cold front will be force back southward across the state on Wednesday, making it through central Utah by midday and southern Utah by Wednesday evening. Moisture and forcing with this system are both limited, and thus expect just some isolated to widely scattered showers to develop along the boundary, mainly over central Utah where the interaction with the pre-existing boundary provides just a bit more forcing. The main sensible weather impact for most will be a cooler northwesterly wind which will push temperatures roughly another 5 degrees cooler from today into Wednesday.

Also, this front has a bit more southward push than the last couple, and will actually make through southern Utah, thus finally knocking the temperatures down a few degrees even in St. George going into Thursday. In addition, late Wednesday night, the northerly gradient behind the cold front will be enough to support some breezy conditions through the typical Washington County gap areas, although largely expect winds to remain below advisory levels (gusts mainly less than 45 mph).

As far as the Freeze Watch goes, potential for sub-freezing temperatures in Eastern Box Elder and Utah Counties is around 60-75% percent. One potential limiting factor for optimal cooling below freezing remains how quickly clouds clear out behind the Wednesday frontal passage, and whether any upstream cloud cover ahead of the next wave starts to move in. There appears to be a window for clearer skies to accelerate radiational cooling early Thursday morning. Given the current probabilities and potential cloud cover starting with a Freeze Watch, and will monitor for needing to upgrade to a Warning with future forecast updates.

.LONG TERM (After 12Z/6AM Thursday)...
The local area will remain beneath a broad cyclonic flow through the end of the week, with progressive short wave energy largely staying north of the region through that time. Caveats to this are Wednesday/Friday when model consensus points towards two short waves amplifying just enough to clip the northern quarter of the region. Scattered showers at most, areal coverage greatest over the northern mountains, and a check back on temps the primary changes to sensible weather with each.

A transitory ridge will build across the area Saturday in advance of a deeper trough progged to translate onto the pac coast by midday.
Backing flow with increasingly gusty winds and a marked increase in temps (from 5 below Fri to 10 above climo Sat) will bring the weekend on a positive note, though increasingly cooler/unsettled conditions will end it. Still a lot of uncertainty regarding amplitude/timing/strength of this trough with passage into the early week period, but guidance is leaning towards another round of bullish precip and high mountain snow. More details to come in time...



AVIATION

KSLC...Light and variable winds in place are expected to prevail from a light northwest through 03z prior to returning to the south per norm. A dry boundary will cross the terminal tonight between 07-09z switching winds back to the north. Increasingly gusty northerly winds expected after sun up Wednesday morning. VFR conditions will prevail.

REST OF UTAH AND SOUTHWEST WYOMING
Breezy southwesterly winds within VFR conditions expected across southern/eastern Utah and southwest Wyoming through this evening...otherwise light winds will prevail. A dry boundary will move north-south across the area between 06z-18z driving increasingly gusty north winds within VFR conditions Wednesday.



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

WY...None.

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