Sunrise 6:44 AM   Sunset 8:19 PM Moonrise 9:28 PM   Moonset 6:25 AM

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FXUS65 KSLC 251029 AFDSLC

Area Forecast Discussion National Weather Service Salt Lake City UT 428 AM MDT Thu Apr 25 2024

SYNOPSIS
An active pattern beginning today will continue into the weekend, resulting in valley rain and mountain snow along with a cooling trend.

.SHORT TERM (THROUGH 00Z SUNDAY)...The large-scale pattern this morning consists of a storm system that is transitioning from an upper low to an open wave trough as it continues to make its way across the desert Southwest. A mean southwesterly flow aloft remains in place across Utah, with an area of showers across northwest Utah and along the Idaho border associated with a diffluent region ahead of the approaching storm. As the trough axis crosses Utah this afternoon, the flow will gradually turn northwesterly behind it with precipitation spreading in from the northwest. Meanwhile, increasing instability will aid additional showers and thunderstorms across the area this afternoon, most notably near the mountains and northern Utah. The HRRR mean SBCAPE values top out at over 500J/kg along an area extending from the Dugway Proving Grounds through northeast Utah. Gusty microburst winds will be the main concern, although surface dewpoints should be trending gradually higher.

Temperatures will trend a bit cooler today, but H7 cold advection after the flow turns northwesterly will lead to more substantial cooling tonight into tomorrow. Afternoon max temperatures today will run closer to climatological normals. In addition, snow levels will remain on the higher side today, above 8500-9000ft. Snow levels will fall closer to 7500-8000ft tomorrow, while afternoon max temperatures fall below normal, to the 50s across the northern and western valleys and 60s across the far south and southeast.

Meanwhile, shower and thunderstorm activity will continue tonight, tomorrow, and into Saturday as the next storm system carves into the area, developing into a closed low over Utah by tomorrow night.
PWATs remain somewhat anomalous compared to climatology both Friday and Saturday. The ECMWF-based Extreme Forecast Index continues to indicate a signal for high QPF for Friday, and has trended a bit in favor of high QPF for Saturday as well. Bottom line, significant precipitation amounts will be possible, but may not be that evenly distributed due to the somewhat showery nature of precipitation. With the lower snow levels for Friday and Saturday, the greatest snow accumulations are expected during this timeframe.
However, impacts could remain somewhat limited as significant accumulation will likely remain confined to areas above 8000ft.

.LONG TERM (After 00Z Sunday/6PM Saturday)...By Saturday evening the center of the storm system that is anticipated to bring widespread precipitation will be downstream of the area, allowing wet conditions to wane through the remainder of the day. With the dynamical forcing east of the area, we'll see more of a transition to orographically driven precipitation (as we typically do with winter systems). Northern Utah and southwest Wyoming will be the primary areas that will see additional precipitation as the storm moves out of the region, with precipitation favoring the high terrain and adjacent valley areas to the east of terrain features.
Models indicate a high amount of lower level moisture remaining in place through the overnight hours, so anticipating precipitation to last through the overnight.

Sunday will feature another round of showers as lower level moisture lingers behind the departing trough, however, additional accumulations of high elevation snow/ valley rain will be quite light. With the coldest air departing the region, should begin to see the start of a warming trend as we head into early next week as high pressure attempts to build in from the south. With an active storm track remaining in place across the PacNW region, the thinking is that a full blown clear sky high pressure system will not take control of the forecast area until the active storm track lets up.
Instead, we'll likely continue to see daily buildups of clouds across the northern half of Utah where instability and moisture combine while the southern half of Utah remains mostly cloud free.
At least for Monday, models show enough moisture in place to support isolated to scattered light showers over the mountainous terrain of northern Utah. Tuesday forward will likely just be cumulus buildups during the afternoon, however, cannot rule out an isolated light shower in the terrain.

Temperature-wise, models appear to be in solid agreement of a rebound from below normal temperatures back to above normal by Tuesday across Utah and southwest Wyoming. For the Wasatch Front, could see temperatures push the 80 degree mark, or beyond. In lower Washington County, daytime highs could be pushing 90 degrees, though current NBM probabilities don't appear to be supportive of this happening. Bottom line, temperatures will return to about 10-15 degrees above normal by Wednesday and Thursday. Southwesterly flow increases ahead of another potential trough late next week, creating dry and windy conditions across much of the area. Though fuels are not of concern at this point, late week may serve as a reminder that fire season is right around the corner.

AVIATION
KSLC...VFR conditions will prevail through the TAF period, with increasing shower activity expected during the afternoon hours and onward. As showers develop this afternoon, CIGs are likely to lower to around 6-7kft AGL, beginning to obscure portions of the local topography during the late afternoon/ early evening. Periods of variable flow are expected through the morning hours but will transition to a north wind around 18Z.

Rest of Utah and Southwest Wyoming...VFR conditions are expected to prevail through a vast majority of the area through the valid TAF period, however, increasing shower activity this afternoon may lead to isolated MVFR conditions for the higher elevation terminals and/ or areas experiencing heavier showers. CIGs will lower through the day, starting around 8kft AGL, dropping to around 5kft AGL by the early evening hours. Local obscuration of local topography will be the main concern. West to northwest winds are expected during the afternoon hours across the western half of the area, with southwest winds across the eastern half. Not expecting any significant gusts, however, isolated strong gusts in excess of 35kts may be possible around showers during the afternoon.



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

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