textproduct: Salt Lake City

KEY MESSAGES

- Calm, stable, and dry sums up much of the forecast for most of the work week with occasional redevelopment of valley inversions possible.

- Chances for precipitation continue to trend toward the Fri-Sat timeframe, and have trended further south and lighter for this forecast cycle.

DISCUSSION

The 12z sounding this morning was indicative of a warm layer slightly above the surface around roughly 300m/1000ft AGL. This has resulted in some valley inversions redeveloping across northern UT, which has been evident near the airport with occasional visibility restrictions in the METARs earlier on. Throughout the day, despite some warming aloft and flow weakening somewhat, it remains cool enough to encourage some mixing throughout the afternoon hours which should deepen the boundary layer somewhat. While the air quality and visibility may not become nearly as good as the past couple days, some improvement is expected this afternoon.

Gap winds across southwest UT, particularly along the I-15 corridor have been observed this morning generally peaking around 30-40mph due to northerly flow and a tightening pressure gradient at the surface. Gusts have begun to taper off somewhat, though sporadic gusts up to 30-40mph will remain possible until the evening hours.

Generally calm conditions persist through at least Wednesday ahead of an incoming split flow pattern. On Thursday, a weak shortwave will progress inland over the PNW with a cutoff low developing off the southern CA coastline, which will also gradually push inland on Thursday-Friday. Over time, these two features will phase together keeping much of the forcing to our south. As mentioned in yesterdays forecast discussion, there was a chance that this system continues to trend south with precipitation favoring southern UT at this time, and that appears to be the case here. While 50% of all ensemble guidance indicates lower geopotential heights to our north, nearly all ensembles support a southern track for this system which will result in northern UT and southwest WY seeing around a trace of precipitation Friday and Saturday at best. In fact, while central/southern UT may be "favored" in this regime, drier air and weaker dynamics aloft will greatly limit the overall extent of this event. Currently, forecast snowfall accumulations across the central and southern UT mountains are well below advisory criteria. To be quite frank, this event isn't trending in a great direction for those who desire precipitation anytime soon. While there is still a chance that northern UT and southwest could see a potential northern trend, as mentioned above regarding geopotential heights to our north potentially weakening, moisture quality and dynamics do not appear to be overly substantial and may only bump precipitation values up slightly.

The silver lining with this forecast, however, is that stronger winds aloft from a more chaotic upper air pattern should provide enough ventilation to prevent valley inversions from getting out of hand through the long term forecast. Around D6-D7 of this forecast, guidance does seem quite keen on ridging establishing itself to our southwest once again. There is potential that this sets us up favorably for more northern stream systems diving down toward the area, though it is too soon to iron out any of those details.

REST OF UTAH AND SOUTHWEST WYOMING

Most areas will continue to see light and terrain-driven winds, with the exception being far southwestern UT where northerly to northeasterly winds around 10- 15kts are prevailing (particularly KCDC this afternoon and KSGU this evening). Valley haze, mainly along the Wasatch Front, will produce slantwise VIS reductions down to MVFR at worst. Expect clear skies otherwise.

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SLC WATCHES/WARNINGS/ADVISORIES

UT...None. WY...None.