Area Forecast Discussion

KEY MESSAGES

- Rather unseasonably warm temperatures will continue through Saturday, continuing the threat for heat-related illness for those who are sensitive to heat, without adequate cooling or hydration, or have chronic health conditions.

- More widespread critical fire weather conditions develop across central and southern Utah Saturday through at least the middle of the upcoming week due to persistent gusty winds. - A few high based showers over far northern Utah tomorrow will be capable of producing strong outflow wind gusts and isolated lightning strikes with little to no rain hitting the ground. Winds may also produce areas of blowing dust during the afternoon.

DISCUSSION

Dry and warm high pressure remains in place over Utah and southwest Wyoming this evening, resulting in generally benign conditions with high temperatures averaging 10F above seasonal normals. A large low pressure system remains well off the Pacific Northwest coast but will move onshore tomorrow. As it does so, the southwesterly pressure gradient over the area will increase, resulting in breezy winds, particularly over central and southern Utah. With relative humidities staying low with poor overnight recovery, this will produce fairly widespread critical fire weather conditions. Temperatures will continue to warm for most of the area, with maxes topping out up to 15F above seasonal normals Saturday afternoon.

The approach of the upper jet from the trough will result in a modest increase in instability beginning tomorrow afternoon for far northern Utah. Despite the rather dry conditions, particularly at lower levels, cannot rule out some showers in the afternoon, with little if any rain reaching the ground. The main threats with any storms that develop will be gusty and erratic outflow winds and some isolated lightning strikes.

There is high confidence that the trough will graze northern portions of the forecast area Saturday night into Sunday. The main impact of this will be to bring a mostly dry cold front through, dropping high temperatures to near seasonal normals for northern portions of the area and up to 5F above seasonal normals for southern Utah. Will need to continue to watch for the potential of gusty outflow winds and isolated dry lightning with any storms that develop along the front, particularly with the combination of instability from the front and daytime heating Sunday afternoon. Winds will overall be less strong Sunday compared to Saturday, but still will be sufficient enough for some critical fire weather conditions.

As the first storm system exits, it is likely that a second storm system will approach the Pacific Northwest coast for Monday. This will be much slower to move than the first one, though latest guidance is favoring somewhat more progressive solutions for this system, eventually having it graze northern Utah during the day Wednesday. Ahead of the system, dry and breezy conditions will persist, keeping the fire danger high. As of now, it looks like this second system will have a bit more cold air and better dynamics than the first system, bringing a greater potential for showers and a decent chance of temperatures dropping below seasonal normals.

AVIATION...KSLC

VFR conditions persist through the valid TAF period with increasing mid and high clouds. Southeasterly winds are expected to increase out of the south after 09z. If winds mix down to the surface (80% chance), gusts may exceed 30 kts at times through the morning. There is a 20% chance that winds do not mix down to the surface overnight through early morning, instead creating potential for LLWS. Otherwise, gusty southerly winds will continue for the afternoon and early evening hours Saturday. Winds are expected to turn northwest between 01-04z Saturday evening, with a 30% chance of brief gusts over 30 kt due to high-based showers to the northwest of the terminal.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions prevail for all regional terminals, with generally increasing mid to high level clouds. Generally light diurnal winds are expected through this evening, gradually increasing out of the south to southwest early in the morning, with widespread gusts 20-30 kts through Saturday evening. During the late afternoon through evening, high-based showers across northern Utah will bring a 30% chance of brief wind gusts over 30kt to some northern Utah terminals.

FIRE WEATHER

Very dry conditions will continue over much of Utah through early next week. Southwest winds will become breezy over much of the area tomorrow ahead of an approaching storm system, and this will result in widespread critical fire weather conditions where fuels are dry over central and southern Utah. There is also the potential for isolated dry lightning as well as some gusty and erratic outflow winds over far northern Utah Saturday afternoon. The storm system will cross the area Saturday night into Sunday, with winds decreasing somewhat during the day Sunday. Still, most locations should see areas of critical fire weather conditions. The potential also remains for isolated lightning strikes and gusty outflow winds, primarily along the front during the day Sunday. Southerly winds will pick up again Monday, remaining gusty through at least Tuesday ahead of another storm system. Thus, anticipating the widespread critical fire weather conditions to continue through at least the middle of the upcoming week.

SLC WATCHES / WARNINGS / ADVISORIES

UT...Red Flag Warning from 6 AM Saturday to 10 PM MDT Sunday for UTZ484-489-492>498.

Fire Weather Watch from Sunday evening through Wednesday evening for UTZ484-489-492>498.

WY...None.