textproduct: Salt Lake City

KEY MESSAGES

- Extreme fire weather conditions will result in a Particularly Dangerous Situation through late this evening across the central and southern mountains and southwest Utah.

- Widespread and significant critical fire weather conditions will continue through Saturday across nearly the entire state.

- A strong cold front will cross northern and central Utah Saturday afternoon through Saturday night. Much cooler temperatures will follow the front, with daytime highs Sunday running 20 to 25 degrees below normal over northern Utah and 10 to 15 degrees below normal over central and southwest Utah.

- Critical fire weather conditions will continue through Sunday across southeastern Utah ahead of the cold front.

DISCUSSION

Enhanced southwesterly flow resides across the forecast area this afternoon, resulting in widespread wind gusts in the 35-45 mph range across the western half of Utah. A mid level dry slot within this flow has overspread much of the forecast area, dropping RH values into the single digits, while afternoon temperatures have climbed into the 90s across most western valleys. This combination of hot, dry and very windy conditions is resulting in an extreme fire weather environment south of I-80. See Fire Weather section for additional details. Meanwhile, convection over northern Arizona will bring a slight chance for strong outflow winds across the Lake Powell area later this afternoon.

This enhanced southwesterly flow is resulting from an upper trough across the Pacific Northwest, which will impact the forecast area through the upcoming weekend. An initial shortwave lifting through the northern Great Basin will push a cold front through northern Utah this evening, bringing a wind shift and slightly cooler temperatures. South of this boundary, gusty southwest winds will likely keep the airmass mixed well into the evening and potentially overnight hours.

This frontal boundary will temporarily retreat Saturday morning, allowing gusty southwest winds to spread back into northern Utah. Meanwhile to the south, strong southwest flow will result in another windy day Saturday across central and southern Utah, and have issued another Wind Advisory for most central/southern valleys.

The aforementioned frontal boundary will surge south through northern Utah Saturday afternoon, and central Utah late Saturday evening into Saturday night, as the upstream trough begins to dig into the northern Great Basin. Instability across far northern Utah will support a convective threat in the vicinity of this boundary during the afternoon hours, with deep layer shear supportive of strong updrafts. As this trough settles into the region, a much cooler airmass will spread into northern and central Utah Sunday. Temperatures across northern Utah will run 20-25 degrees below normal and remain in the 60s across the northern valleys, while further south temperatures across central and southwest Utah will remain 10-15 degrees below normal. As the upper trough axis swings through the area Sunday morning, a chance for rain (and maybe even snow above 10k feet) will spread across the northern mountains and perhaps northern portions of the Wasatch Front as well.

Rising heights in the wake of this trough will result in a warming trend throughout next week, with hot and very dry conditions returning midweek.

AVIATION

KSLC...Gusty south to southwest winds persist into the evening ahead of a front. Expect frontal passage roughly 00-02Z Saturday, bringing a quick gusty northwest shift. Winds will gradually become less breezy in the following hours with thickening mid level clouds. Models suggest potential for a period of light southerly to variable winds between 05-10Z as clouds continue to thicken and lower some. Additionally, there is a 20-40% chance of showers between 11-15Z. Northwest winds and gusts pick back up for Saturday afternoon.

REST OF UTAH AND SOUTHWEST WYOMING...Gusty south to southwest winds continue as a strong cold front approaches. At northern terminals, this front will pass between around 23Z Fri to 03Z Sat. Mid level clouds thicken, and winds shift gusty to the northwest as the front passes, with gusts relaxing some in the following hours. Northwest to north winds generally expected to persist thereafter, but some variability possible, especially during any periods of precipitation. Shower chances will also increase Saturday morning prior to sunrise, with chances higher at terminals further north. Southern terminals stay in a prefrontal environment, and a southerly direction will remain favored.

FIRE WEATHER

A widespread and significant period of critical fire weather conditions is ongoing across Utah, and will persist overnight and through Saturday across most of central and southern Utah. Southwesterly wind gusts approaching 50 mph and RH values in the 5 to 10 percent range will continue through this evening, with the greatest threat across zones 493, 495 and 496 where a Particularly Dangerous Situation (PDS) Red Flag Warning is in effect. Any RH recovery overnight will remain below 30 percent as southerly winds remain gusty through much of the overnight hours. Gusts will again approach 50 mph Saturday across central and southern Utah ahead of an approaching cold front, and although RH values will trend higher the strength of the southwest winds will continue to result in significant critical fire weather conditions through Saturday evening.

Further north, the first of two cold fronts will reach far northern Utah this afternoon, bringing a marked and strong wind shift to northwestern portions of zone 478. This front will reach I-80 this evening bringing a wind shift, with strong gusty winds from the northwest likely along the Nevada border. More stable air will bring improved overnight RH recovery to areas north of I-80 tonight, while recovery remains poor to the south. This front will retreat northward Saturday morning allowing gusty southwest winds and very low RH to spread back into northern Utah.

A strong cold front will cross northern Utah Saturday afternoon, then progress into central Utah Saturday evening. Behind this front winds will switch to northwesterly as a much cooler and more stable airmass spreads into the region for Sunday. Ahead of this front, critical fire weather conditions and very low RH will redevelop Sunday across south central and southeastern Utah.

A warming trend will follow for much of next week. Initially gusty winds and low RH will bring local critical fire weather conditions to central and southern Utah. A return to hot, dry and potentially windy conditions will follow for the latter half of next week, with single digit RH and poor recovery becoming common across the entire area by Thursday.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Red Flag Warning until midnight MDT Saturday night for UTZ478- 479-482-484-488-492-495-497.

Wind Advisory from 6 PM this evening to midnight MDT tonight for UTZ101.

Wind Advisory until 8 PM MDT this evening for UTZ102.

Red Flag Warning until 9 PM MDT Sunday for UTZ489-494-498.

Wind Advisory until midnight MDT tonight for UTZ115-116-118-119- 122-123-126>128.

Wind Advisory from 10 AM Saturday to midnight MDT Saturday night for UTZ115-116-118-121>124-126-128>131.

Red Flag Warning until 3 AM MDT Sunday for UTZ493-496.

WY...None.