Sunrise 6:36 AM   Sunset 8:22 PM Moonrise 12:28 AM   Moonset 9:40 AM

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FXUS65 KSLC 290952 AFDSLC

Area Forecast Discussion National Weather Service Salt Lake City UT 352 AM MDT Mon Apr 29 2024

SYNOPSIS
Mild southwesterly flow will prevail across the region through much of the day today. A cold front will cross northern Utah late this afternoon, then stall across central Utah this evening. A secondary cold front will cross the area Tuesday night bringing much cooler temperatures for Wednesday.

.SHORT TERM (Through 12Z/6AM Wednesday)...Predominantly zonal flow is in place across the Great Basin this morning, downstream from an upper trough making landfall along the Pacific Northwest coastline. As this trough spreads inland across the Interior Pacific Northwest today, a mild southwesterly flow will become established across the forecast area. This will allow for a warming trend of 5-8F this afternoon across the western valleys including the Wasatch Front, where max temps will reach the upper 60s. Meanwhile temperatures will reach the low 80s across lower elevations of southern Utah including St George, Zion Canyon and Bullfrog.

As the upstream trough continues east, the associated cold front will reach northwest Utah late this afternoon, then push through northern Utah this evening before stalling across central and southwest Utah overnight. Increasing ascent ahead of this boundary will allow for scattered showers and isolated thunderstorms by mid afternoon across northern Utah, before a broken band of precipitation spreads across the north this evening along the low level baroclinic zone. Valley QPF will remain minimal...less than 0.05, while 0-10.0.25" of QPF is expected across the northern mountains.

Behind this boundary, cooler air will knock max temperatures down 7-10F Tuesday across northern utah, while to the south of the boundary temperatures across southern Utah will stay close to persistence.

The next upstream trough will push a cold front through northern and central Utah Tuesday night, bringing a re-enforcing shot of cold air. Moisture will be limited with this wave, with the better upper forcing and any associated chance for measurable precipitation holding off until Wednesday.

.LONG TERM (After 12Z/6AM Wednesday)...A trailing shortwave trough associated with a longwave trough positioned near the Montana and North Dakota border will swing into southwest Wyoming and northern Utah Wednesday. This will be from the same longwave trough as Monday's cold front, and it will have similar characteristics. It will be a rather dry boundary. Precipitation totals for the mountains will generally be less than 0.10", while valley precipitation will be less. Cold air advection will be a bit stronger, as 700 mb temperatures drop to -10C in the north. That will result in high temperatures in the 50s for most valleys and 30s or 40s for the mountains, roughly 10-20F cooler than normal.
Ensemble guidance is in good agreement that the boundary will get into southern Utah, but no precipitation is forecasted. Along with the cooler temperatures will be gusty post-frontal winds. Winds will be enhanced by a strong pressure gradient and 700 mb winds near 30 knots. The strongest speeds and gusts will be in downslope areas off higher terrain in west to northwest flow, including Castle County and the Uinta Basin through Wednesday afternoon.

The shortwave trough will have pushed into Colorado Thursday.
Scattered mountain snow showers for northern Utah will continue. The biggest difference will be much lighter winds throughout southwest Wyoming and Utah. Northern portions will have slightly warmer temperatures, while southern Utah will be slightly cooler, as the front won't reach there until Wednesday afternoon or evening.

Ensembles diverge, with more uncertainty later in the week. One scenario would be a grazing shortwave trough, slightly cooler temperatures, and light precipitation, mainly for the northern mountains. Another would be shortwave ridging building to the west with dry and warmer conditions. The grazing shortwave is slightly more likely, with about 60% of ensemble members with that.

AVIATION
KSLC...Light southeast winds will transition to the south then southwest through the morning. West to northwest winds are likely much of the afternoon, with gusts exceeding 20 knots.
Isolated showers are not expected to bring any precipitation, but could bring enhanced, erratic outflow winds through the afternoon. A cold front will increase winds, with flow prevailing from the northwest around 03Z.

REST OF UTAH AND SOUTHWEST WYOMING
South to southwest winds will increase through the morning. Winds will range from southwest to northwest much of the afternoon, with gusts exceeding 30 knots at some locations. Isolated to scattered showers for southwest Wyoming and northern Utah could bring enhanced, erratic outflow winds from 20Z through the evening.

SLC WATCHES/WARNINGS/ADVISORIES
UT...None.
WY...None.

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