textproduct: Salt Lake City

KEY MESSAGES

- Scattered high based convection will develop Monday afternoon and evening across portions of central and northern Utah, and southwest Wyoming. Gusty outflow winds to around 50 mph will be possible. Limited moisture will then linger across the north Tuesday.

- Elevated to locally critical fire weather conditions can be expected across southwest Utah Tuesday, then across central and southern Utah Wednesday, due to gusty southwest winds and low relative humidity. - A heat wave late this week through the upcoming weekend will bring areas of major HeatRisk across the region. Afternoon temperatures below 6000 feet will reach or exceed 100 degrees across the area Saturday and Sunday. Temperatures along the Wasatch Front will approach 105 during this time, and 110 around St George and Zion Canyon.

DISCUSSION

Southwesterly flow aloft resides across the forecast area early this afternoon, along the western periphery of an upper ridge centered over the central and southern Rockies. A shortwave trough lifting through the Pacific Northwest and northern Great Basin helped advect mid level moisture across the forecast area overnight.

Currently seeing high based convection develop over the central and southern mountains, and this activity will progress north and northeast over the next few hours. Meager instability across the lower elevations may cause this convection to struggle as it tries to move off the terrain this afternoon. Meanwhile, addition convection currently initiating across eastern Nevada will spread across northwest Utah late this afternoon through this evening, potentially impacting the Wasatch Front. Again some question remains regarding how well this convection will maintain itself as it spreads of the terrain of eastern Nevada and into the desert, but any convection which does persist will be capable of strong microburst winds given the deep and dry sub-cloud environment.

Much of this moisture looks to remain across the area Tuesday, and potentially into Wednesday, maintaining a chance for afternoon and evening convection over portions of northern and central Utah. With this moisture in place daytime temperatures will remain near to slightly above climo.

Attention then turns to an expanding mid level ridge which will bring hot and very dry conditions beginning Friday, and continuing through the upcoming weekend. By Saturday, max temperatures across most elevations below 6000 feet will reach or exceed the 100F mark, then trend a little hotter Sunday. For KSLC, the 25th-75th percentile max temps from the NBM run 101-105 Saturday, 102-106 Sunday, and 100-105 Monday, with a 10% chance of tying the all time record of 107F both Sunday and Monday. The 75th percentile at KSGU runs at or above 110 Saturday through Monday. This will result in areas of Major and locally extreme HeatRisk through the weekend, particularly across northern and central Utah.

Model guidance continues to suggest this ridge axis shifts far enough east by the middle of next week to allow appreciable monsoon moisture to spread into the region, mostly likely during the July 14th-15 timeframe.

AVIATION

KSLC...There is low confidence in wind direction this afternoon at KSLC, with the typical diurnal wind shift expected as early as 19z or as late as 22z outside of any outflow. Speaking of outflow, while the main threat for thunderstorms/outflow winds up to 30-40kts is expected between 00-04z, cannot rule out a couple isolated storms moving off the Oquirrh Mountains earlier this afternoon. Winds will be largely light and variable during the overnight hours.

REST OF UTAH AND SOUTHWEST WYOMING...Scattered showers and thunderstorms will develop this afternoon across northern/central Utah and southwest Wyoming, where any storms will be capable of producing gusty and erratic outflow winds up to 30-50kts...where the higher end will be largely limited to northern areas. Winds will be largely light and terrain-driven overnight.

FIRE WEATHER

High based moisture which spread across the region over the last 24 hours will continue to bring a chance for high based showers and dry thunderstorms through this evening, and again Tuesday afternoon and evening, mainly north of I-70/US-50. In addition to lightning, strong outflow winds to 50 mph will be possible with these storms. With this moisture in place, RH has trended higher today, which will result in improved overnight recovery and elevated RH again Tuesday across northern and central Utah. Further south, drier air will allow afternoon RH values to fall near or below 15% across southwest Utah, which will result in elevated to near critical fire weather conditions in zone 495 and 497.

A drier westerly flow Wednesday into Thursday will drop daytime RH values below 15% across most elevations below 8000 feet across central and southern Utah. This combined with the westerly flow will result in elevated to locally critical fire weather conditions. At this time these locally critical conditions don't look to be widespread enough to warrant a Fire Weather Watch. A strong area of high pressure will bring hot temperatures and very low RH to the region late this week through the upcoming weekend. This high is expected to move far enough east next week to allow monsoon moisture to spread into the region around the July 14th-15th timeframe.

SLC WATCHES/WARNINGS/ADVISORIES

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