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Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
321 FXUS65 KSLC 132209 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 409 PM MDT Thu Jun 13 2024 .SYNOPSIS...Anomalous heat persists today, with 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/6AM Saturday)... The main talking point in the short term is the heat across Utah that peaks today. Readings at the Salt Lake Airport have just touched the century mark this afternoon, making it the first of the year, and roughly about 3 weeks ahead of the average first 100. Heat advisories remain in place across the Wasatch Front and over into Wendover. An excessive heat warning remains in place for the Glen Canyon NRA / Lake Powell area where high temperatures continue into low to mid 100s again today, resulting accumulated heat stress over the last couple days. The ridge responsible for the heat wave will continue to weaken and shift eastward away from the forecast area tonight into Friday while a filling low pressure system over southern California this afternoon continues to weaken as it tracks toward the Four Corners through Friday afternoon. Ahead of this low, mid-level moisture is already increasing into southern Utah, and this trend will continue from south to north across mainly the eastern half of the state tonight, while overall cloud cover will expand across much of Utah overnight. Simultaneously, winds will continue to increase from south to north as the pressure gradient tightens ahead of the low pressure system. This will result in an anomalously warm night night tonight as the combination of elevated winds maintain a mixed boundary layer and clouds limit radiational cooling. Thus warm overnight lows will continue to contribute some of the heat stress, particularly across northern Utah, limiting cooling relief tonight for those without air conditioning . By Friday, temperatures will be moderated by the low pressure system moving in and mid/high level cloud cover overspreading a good portion of the state, especially across eastern Utah. Isolated showers are possible on Friday, mainly across eastern Utah, but little to no appreciable rain is expected. .LONG TERM (After 12z/6AM Saturday), Issued 441 AM MDT... 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...Weak low pressure lifting through the region this evening will continue to drive strong southerly winds aloft... with that, expecting continued impulses of southerly winds and an early decay (~02Z) of the northerlies driven by today`s lake breeze. High and thin clouds move in overnight, with another morning of enhanced southerly flow for Friday. This has the potential to again delay the shift to northerly flow Friday afternoon with a chaotic transition period. .REST OF UTAH AND SOUTHWEST WYOMING...Southern Utah will continue to see gusty winds in the vicinity of high-based showers or virga. Southerly winds will die down some overnight, with cloud cover spreading over the region, generally above 15kft, clearing again through the morning hours Friday. Winds will be subdued some midday as the center of low pressure moves in overhead, but any shower activity in the afternoon could again produce localized gusty winds - particularly along the UT/NV border. && .FIRE WEATHER... High pressure continues to decay east of Utah as a weakening low pressure system fills moving from southern California this afternoon toward the Four Corners Friday afternoon. Hot, dry conditions continue across the state today with increasing winds across southern Utah as the low pressure system approaches. This is resulting in critical fire weather conditions across southern Utah this afternoon where Telegraph Flat is already at 6% RH with wind gusts to 37 mph. Moisture will quickly increase from south to north, mainly across eastern Utah into Friday as the low pressure system continues to approach. This will increase RH values slightly into Friday afternoon, increase cloud cover overnight, with some partial clearing later Friday afternoon, and result in some isolated rain showers, with very low (<10%) chance of wetting rain, mainly over eastern Utah. This weekend into early next week an anomalously deep trough for this time of year will develop over the Pacific Northwest. There is high confidence that this will develop critical fire weather conditions given the very dry and breezy southwesterly flow ahead of this trough, mainly across southern Utah. With zones 497 and 498 fuels recently turned critical, we`ve issued a Fire Weather Watch. Winds by Sunday, but especially Monday there is about a 50% chance of seeing gusts exceeding 45 mph, along with high confidence in widespread sub 10% RH values across these zones (as low as 5%). Meanwhile northern Utah will see some cooling/moistening early next week as strong cold front will eventually push through, likely by Monday afternoon or evening. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Heat Advisory until 6 AM MDT Friday for UTZ101-102-104>106. Red Flag Warning until 9 PM MDT this evening for UTZ498. Fire Weather Watch from Saturday morning through Monday evening for UTZ498. Excessive Heat Warning until 10 PM MDT this evening for UTZ131. Fire Weather Watch from Sunday morning through Monday evening for UTZ497. WY...None. && $$ SHORT TERM...Church LONG TERM...Cunningham AVIATION...Wessler FIRE WEATHER...Church For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity