textproduct: Salt Lake City

KEY MESSAGES

- Hot and dry conditions will persist today, with northern Utah seeing the hottest temperatures of the season thus far. This will bring an increased risk of heat related illnesses along portions of the Wasatch Front.

- Gusty southwest winds in excess of 30 mph combined with very dry relative humidity values will bring critical fire weather conditions to western Utah this afternoon and evening. The focus for critical fire weather conditions will shift to areas of central and southern Utah east of I-15 on Saturday.

- Scattered dry thunderstorms are possible (30% chance) across northern Utah Saturday afternoon and evening. Strong outflow winds in excess of 50 mph can be expected with these storms, along with dry lightning.

- High pressure will rebuild for early next week, keeping conditions very dry with a steady warming trend in temperatures. The potential for heat related illness could increase for some valleys by the middle of next week.

DISCUSSION

A negatively tilted shortwave ridge axis extends across the forecast area early this afternoon. A tongue of 14C 700mb temperatures per RAP analysis extends along and north of this axis. This will push max temperatures into the mid-upper 90s along the Wasatch Front this afternoon, where a Heat Advisory is in effect for Davis and Salt Lake Counties. To the south of this ridge axis, southwesterly winds aloft are overspreading southwest Utah currently, and will gradually strengthen through the afternoon and evening ahead of a shortwave trough lifting into the southern Great Basin. These winds along with very low RH will result in critical fire weather conditions across west central and southwest Utah this afternoon and evening where a Red Flag Warning is currently in effect. Lastly, an arc of mid level moisture lifting ahead of this trough is currently lifting through the northern Great Basin, and extends back into central Utah. This will provide enough fuel for isolated high based convection from the central mountains northeastward through the Wasatch Plateau and western Uintas this afternoon.

As this shortwave trough lifts northward through this evening, better convective coverage will largely remain to the west across Nevada. However, later this evening some of this activity is forecast to spread into northwest Utah per hi-res guidance. Limited instability and forcing should keep the threat for lightning isolated across northwest Utah, however could see locally strong outflow winds near areas of virga.

Heading into Saturday, a loosely organized upper trough currently off the California coast will spread inland across the Great Basin bringing a notable cooling trend of 5-8F across northern Utah, and 2-4F across the south. An increase in mid level moisture will allow for high based convection across northern Utah Saturday afternoon and evening, where hi-res guidance is consistently developing scattered convection accompanied by strong outflow winds. Meanwhile, gusty west winds will overspread much of central and southern Utah east of I-15, where a Red Flag Warning will be in effect Saturday afternoon and evening.

Temperatures will remain near seasonal norms on Sunday, before mid level ridging begins to expand across the region during the first half of the upcoming week. This will bring a warming trend hot and dry conditions by midweek. This will elevate the HeatRisk and likely result in an increase in heat related issues during the latter portion of next week.

FIRE WEATHER

A hot and very dry airmass remains in place across the state this afternoon, with the hottest temperatures of the year thus far across northern Utah. Gusty southwest winds are beginning to spread into southwest Utah, and will expand northward and strengthen through the afternoon and evening hours. These winds will likely remain elevated into the overnight hours, thus the Red Flag Warning for this area continues beyond sunset. Meanwhile high based moisture will allow for a couple of isolated dry thunderstorms across zones 493, 488 and perhaps 480 this afternoon. Additional high based showers and isolated dry thunderstorms will spread into northern Utah this evening, which may bring rogue wind gusts to around 40 mph but little to no rainfall.

A low pressure system will move into the Great Basin Saturday bringing a cooling trend. The airmass will remain very dry across central and southern Utah, with the axis of gusty winds shifting across areas east of I-15. The Fire Weather Watch was upgraded to a Red Flag Warning for these areas Saturday afternoon and evening. Although winds will be a bit weaker across southwest and west central Utah Saturday, fire weather conditions will remain elevated, and local pockets of critical fire weather conditions are possible.

As this low pressure system moves into the region, high based showers and dry thunderstorms are expected to develop across northern Utah Saturday afternoon and evening. Strong outflow winds in excess of 40 mph will be possible, with a few gusts approaching 60 mph. The areal coverage of dry lightning remains a bit uncertain, thus have opted to go with a Fire Weather Watch for zone 478 for now.

As this low pressure system moves through the region, temperatures will cool back down to near normal Sunday. High pressure will strengthen across the region through much of next week bringing a warming trend, with a return to hot and very dry conditions by midweek.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Fire Weather Watch from Saturday afternoon through Saturday evening for UTZ478.

Heat Advisory until 6 AM MDT Saturday for UTZ104-105.

Red Flag Warning from 3 PM this afternoon to 3 AM MDT Saturday for UTZ492-495.

Red Flag Warning from noon to 10 PM MDT Saturday for UTZ482-484- 488-489-493-494-496-498.

Red Flag Warning from 3 PM this afternoon to midnight MDT tonight for UTZ497.

WY...None.