textproduct: Salt Lake City

KEY MESSAGES

- Day 3 of critical fire weather conditions persist across central and southern UT tomorrow, lasting through at least Wednesday as forecast confidence continues regarding gusty conditions with low relative humidity each afternoon.

- Given preceding dry and gusty conditions, blowing dust is expected once again across much of UT and southwest WY tomorrow afternoon.

- On Tuesday, strong to severe thunderstorms may form ahead of an incoming cold front across northern UT. Strong to severe wind gusts and potentially severe hail appear to be the primary threats.

- A warming and drying trend takes hold Thursday into the weekend with high temperatures climbing above climatological averages.

DISCUSSION

Once again, the critical fire weather threat continues across central and southern UT tomorrow as winds see a notable increase ahead of a midlevel trough. Despite afternoon humidities remaining somewhat higher than the past few days in the low-teens, a stronger and more widespread wind threat is on track to develop across central and southern UT. While probabilities for wind gusts greater than 40mph have tapered off somewhat and become more localized, probabilities for gusts in excess of 30mph remain around 70%+ across the majority of central and southern UT tomorrow afternoon. Thankfully, dry thunderstorms do not appear to pose a threat tomorrow compared to the past couple days as height rises persist across central and southern UT as the initial midlevel trough lifts to our northeast.

On Tuesday, the critical fire weather threat appears to favor southeast UT where probabilities for gusts in excess of 40mph range from 40-60%. Across the remainder of southern UT and central UT, probabilities for gusts greater than 30mph remain widespread and rather high around 70%+. Wind probabilities surrounding western UT and especially the Washington county area remain uncertain at this time as the subtropical jet is displaced further east, favoring eastern UT and western CO, all while the midlevel trough lifts north with the stronger flow aloft. Additionally, CAM guidance hints at a potential mid-level warm later which would prevent winds from mixing down to the surface across the aforementioned areas. This has created a somewhat uncertain forecast for Tuesday with respect to winds.

On Tuesday afternoon, a rather interesting severe setup may develop along the ID/UT border favoring strong to severe thunderstorms and perhaps the development of a couple supercells. At the surface, a cold front will slowly swing into the area from the northwest with ample midlevel moisture in place as a midlevel trough swings toward the PNW. As the parent trough begins to deepen and take a negative tilt across the PNW, a shortwave appears to deepen along the base of the trough resulting in enhanced midlevel westerly flow to around 50kts along the frontal boundary and across the ID/UT border. With enhanced flow aloft and modest surface flow out of the south- southwest, bulk shear values ranging from 30-40kts appears evident across most 00z CAM guidance. Additionally, H5 temperatures will be rather cold for June ranging from -14C to -17C. Coupled with surface temperatures in the mid 60s to low 70s, these cold H5 temperatures will steepen lapse rates markedly to around 7.5-8C/km. While these lapse rates aren't necessarily steep compared to most hot and dry summer days across the Great Basin, this is notable given dewpoints ahead of the front across northern UT are forecast to range from the mid 40s to upper 50s yielding a significantly smaller dewpoint depression than our run of the mill dry thunderstorm days. With this anomalous overlap of parameters, the potential for strong to severe storms developing ahead of the cold front cannot be ruled out Tuesday afternoon. Given ample shear and instability in place, isolated supercells cannot be ruled out which would pose a severe wind and hail threat. Some uncertainties exist regarding the southeastern extent of the cold front, though high confidence exists regarding thunderstorm development across northern UT Tuesday afternoon.

Wednesday will bring another round of fire weather conditions to central and southern UT, though uncertainty remains regarding the northern and western extent of the critical fire weather conditions due to frontal boundary placement. Winds may struggle to mix to the surface across much of western UT on Wednesday, and as such, westernmost fire zones have been removed from the fire weather watch for Wednesday.

From Thursday on, height rises appear likely as nearly all global ensembles indicate large-scale ridging building off the West Coast. This will result in primarily westerly flow areawide, serving to raise temperatures to roughly 5-10F above seasonal normals as early as Thursday. Ensembles hint at a pivot to northwesterly flow aloft with embedded shortwaves potentially yielding a few instances of unsettled weather across the CWA this weekend, though high uncertainty regarding this outcome exists at this time.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions prevail across the area under increasing high level cloud cover through the forecast period. Breezy northerly winds will prevail across the West Desert through around 09-10Z before relaxing, with all other terminal expected to see light drainage flows overnight. Gusty southwest winds resume by the early afternoon hours on Monday for much of the region with peak gusts expected around 25-30kts.

FIRE WEATHER

Critical fire weather conditions continue across central and southern Utah through this evening given widespread southwesterly winds with gusts 30-40 mph and RH in the low teens. There is a more conditional fire weather threat once again this afternoon, mainly across portions of central to northeastern Utah as high-based thunderstorms develop this afternoon, with potential to produce dry lightning strikes and gusty and erratic outflow winds to 50 mph. Winds taper this evening areawide, but another weather system digging into the Great Basin Monday into Tuesday will bring another extended period of gusty southwesterly winds with gusts 30-40 and locally to 45 mph through this period. Strongest winds will be favored across the western half of Utah on Monday, then shift to eastern Utah on Tuesday. A mostly dry cold front sweeping through the region late Tuesday will bring downsloping winds to portions of eastern Utah on Wednesday, which will bring locally critical fire weather conditions as daytime humidity values remain in the single digits to low teens across the area.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Red Flag Warning from 10 AM Monday to 10 PM MDT Tuesday for UTZ484-489-492>498.

Fire Weather Watch from Wednesday morning through Wednesday evening for UTZ484-489-493-494-496-498.

WY...None.