Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
110 FXUS65 KSLC 131041 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 441 AM MDT Thu Jun 13 2024 .SYNOPSIS...Anomalous heat persists today, with potential for triple digit readings along portions of the Wasatch Front for the first time this year. A mid to upper level low will move through late today through Friday, bringing a slight cooldown and some low end precipitation chances. A stronger storm system looks to affect the area early next week, bringing gusty winds and much cooler temperatures. && .SHORT TERM (THROUGH 12Z SATURDAY)...The axis of the upper ridge over the area has shifted east this morning, allowing for increased southwest flow into Utah. Upstream, a closed low remains in place off the SoCal and northern Baja coast, but will be advancing inland later today. Meanwhile, a few lingering showers remain in place across far northern Utah. These are not producing much in the way of precipitation or winds at this time, and should taper off shortly after sunrise as PWATs decrease across northern Utah. As the low approaches Utah, breezy conditions can be expected today, especially across southern Utah. Midlevel moisture will also start to spread into the area from the south. As such, expect increasing cloud cover across southern/eastern Utah today with some weak, high- based showers which may produce a few gusty microbursts. This moisture will lead to a slight drop in temperatures across the south today. However, across northern through west-central Utah, dry conditions, better mixing, and slightly higher H7 temperatures near the Idaho border should result in afternoon max temperatures as high as, or slightly higher than, yesterday. The latest NBM has a 61% chance of SLC reaching 100 degrees today. As the low continues to progress inland, it will fill before ejecting across the Four Corners area tomorrow. Midlevel moisture will continue to increase ahead of this storm system. However, the latest models are increasingly shunting the bulk of the moisture farther east. As such, the prospect of seeing any appreciable amounts of precipitation has decreased. Still, expect a few high- based showers to continue across southeast Utah overnight tonight, then increase in coverage tomorrow afternoon over the spine of Utah and into the eastern valleys. Gusty microburst winds remain the main threat. Cooler temperatures will also spread into the area by tomorrow, decreasing the threat of significant heat. That said, afternoon maxes tomorrow remain up to 5 degrees above normal across southeast Utah, and 6-12 degrees above normal elsewhere. .LONG TERM (After 12z/6AM Saturday)...Model guidance continues to trend cooler with the potent cold front arriving on Monday. Expect a stark transition to spring-like temperatures, contrasting the near- record heat we have seen this week. At the start of the long-term, a strong closed low will likely be positioned over WA and southern BC. As it inches closer over the weekend, expect a gradual cooling trend on Saturday and Sunday with highs returning to around normal by Sunday. With a strengthening pressure gradient as the trough begins to push southward, gusty southwesterly winds are expected to develop Sunday afternoon. The highest winds will occur mainly south of I-70, with current ensemble mean gusts reaching 30-40 mph. Winds are likely to peak Monday afternoon ahead of the cold front, with ensemble means exceeding 50 mph in portions of southern UT. As the upper-level trough swings across the northern Great Basin and into the Intermountain West, its cold front will push through our area on Monday. The air mass will likely be too dry for much precipitation, aside from a few isolated showers near the UT-ID border just behind the frontal passage. Uncertainties in the upper-level pattern still remain, with disagreement of the timing of the cold front and extent of cooler temperatures. Models have overall trended a bit later with the cold front, now looking more likely for late Monday into Tuesday. Eighteen percent of ensemble members suggest a much milder cooldown, with 700-mb temperatures dipping down to +6C. On the other end of the spectrum, another 21% of members favor a more aggressive cooldown with 700-mb temperatures reaching -5C. The remainder are somewhere in the middle, with a mean around -2C, which is still below the climatological 10th percentile for mid-June. At the surface, this translates to highs around 70F across the Wasatch Front and near 90F in far southern UT...though keep in mind that there is still a 10 degree spread in the NBM 25th-75th percentiles. && .AVIATION...KSLC...Southeasterly winds will continue at least through the morning, becoming light and variable at times. Heading into the afternoon, there is high uncertainty with whether or not the lake breeze (and thus NW winds around 10kts) makes it over the terminal Thursday afternoon. There is currently a 60% chance that this occurs, with the most likely timing being after 20z. Otherwise, there is a 40% chance that southerly winds with gusts to 25kts persist through the afternoon. .REST OF UTAH AND SOUTHWEST WYOMING...Gusty southwesterly winds will develop after 17z, especially across areas south of KDTA-KPUC. Scattered showers and isolated thunderstorms are possible after 20z southeast of roughly KBCE-KPUC, likely continuing well into the evening hours. Gusty and erratic winds are possible near these showers. && .FIRE WEATHER...High pressure over the area will start to shift east today, bringing increased southwest flow while maintaining hot temperatures over the area. Winds will be strongest this afternoon over southern Utah, which will bring locally critical fire weather conditions to south-central Utah where fuels have cured. Midlevel moisture will begin to spread into south-central and southeast Utah this afternoon, with weak, high-based showers possible. These will have the potential to bring a few erratic and gusty outflow winds. Moisture will increase more tonight into tomorrow, bringing an increased threat of measurable rain, although the wetting rain chances remain on the low side. Gusty outflow winds will continue to be the main threat. Otherwise, will see temperatures to cool a bit into the weekend. A relatively deep trough for this time of year is anticipated to carve into the area for the first half of next week. Ahead of this, gusty southwest winds Sunday into Monday could bring another round of critical fire weather conditions to areas where fuels have cured. Much cooler temperatures can then be expected as this storm tracks into the area, although it is not expected to be accompanied by much in the way of moisture. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Heat Advisory until 6 AM MDT Friday for UTZ101-102-104>106. Red Flag Warning from noon today to 9 PM MDT this evening for UTZ498. Excessive Heat Warning until 10 PM MDT this evening for UTZ131. WY...None. && $$ Cheng/Cunningham For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity