textproduct: Salt Lake City

KEY MESSAGES

- Scattered showers with a few thunderstorms will impact northeastern portions of the forecast area early Thursday through Thursday afternoon.

- Locally elevated fire weather conditions will occur across far southern Utah Thursday afternoon and evening. After a break, critical fire weather conditions are likely (>60% chance) to return across much of Utah on Tuesday into Wednesday.

- Elevated winds are likely (>50% chance of 45+mph) across western Utah on Tuesday

DISCUSSION

An area of mainly virga and sprinkles has moved through the Wasatch Front this morning associated with an upper level trough moving from eastern Idaho into southwest Wyoming while grazing northern Utah. Increasing lapse rates under the trough combined with daytime heating is resulting in an area of 200-300 J/kg of mixed layer CAPE across northern Utah into Southwest Wyoming. Thus the best axis for isolated to widely scattered thunderstorms this afternoon will be from around Logan eastward to Evanston and southward into the Uinta mountains. Some isolated wind gusts up to 45 mph can't be ruled out from any thunderstorms in this area. Moisture and instability decrease south of this axis toward SLC eastward to Duchesne, and thus expect generally dry conditions to persist this afternoon along and south of that line.

On Friday the frontal boundary will stall across central Utah with broad weak cyclonic flow aloft still in place. This will support a few isolated to widely scattered showers developing over the central mountains Friday afternoon. Otherwise, expect dry conditions across northern and southern Utah.

A warming trend will continue this weekend with dry conditions as height build aloft from a high pressure system centered over Arizona and New Mexico. Temperatures will run about 10 degrees above average by Sunday into Monday in response to this warming and subsidence.

For Monday through Wednesday next week the pattern will become more active again. With the ridge axis to our east and a deep trough moving into the Pacific northwest, models are in good agreement that a shortwave trough near Southern California will track northeastward across eastern Utah Monday night and into southern Wyoming during the day Tuesday. Mid and high level moisture will be pulled northward across central and eastern Utah ahead of that shortwave and will start increasing the chance of elevated showers and thunderstorms over the high terrain Monday afternoon. Currently the shortwave timing trough eastern Utah looks to be Tuesday morning, and thus ill-timed for peak heating. Thus convective wind threat would be more minimal, however given this is 5 days out, if that timing were to change, there would be an elevated thunderstorm threat with strong gusty winds. That will be something to keep a close eye on. Otherwise, drier air across western Utah on Tuesday will likely combined with stronger wind gusts (>50% chance of gusts 45+mph) to create critical fire weather conditions. As the upstream trough moves in closer to the area on Wednesday that threat will shift east into eastern Utah. There remains decent spread on the track of that cutoff low and exactly how fast it will track eastward across the area next week, which will influence conditions from Tuesday/Wednesday onward next week.

REST OF UTAH AND SOUTHWEST WYOMING

A frontal boundary is currently shifting across the state resulting in gusty NW winds beginning to fill in across all northern UT sites through the afternoon. KEVW may see isolated thunderstorms over the next 1-2hrs. Otherwise, VFR conditions will persist across all sites through the TAF period.

FIRE WEATHER

A storm system will bring an area of scattered showers and thunderstorms across northeastern Utah today, mainly from around Logan southeastward into the Uinta Mountains. The cold front associated with this storm system will push through central Utah this afternoon and evening where it will stall into tomorrow. Behind this cold front across eastern Utah, dry conditions with RH values ranging from the upper teens near Price, will drop into the 10-15% range for areas from Green River to Hanksville to the Grand Staircase. Winds will also briefly pick up this afternoon with around a 40-60% chance of exceeding 25 mph in this area, making for near-critical to locally critical fire weather conditions where fuels are receptive, mainly in Zone 489.

A few isolated to widely scattered showers and thunderstorms will develop along the stalled frontal boundary across central Utah tomorrow, mainly over the high terrain. Locally gusty and erratic outflow winds cannot be ruled out with those storm. Otherwise, the rest of the area will be on warming and drying trend through the weekend with temperatures trending to about 10 degrees above average by Sunday into Monday.

There is increasing confidence in increasing southwesterly winds by Tuesday across western Utah along with low humidity. There is now about a 60% chance of critical fire weather conditions developing over western Utah by Tuesday afternoon from a combination of low humidity and wind. There is even about a 50% chance that winds will exceed 45 mph across western Utah during this period of low humidity. By Wednesday there is increasing spread in how quickly the low pressure system will track eastward, but the overall trend will be the spread the windy and dry conditions in eastern Utah by Wednesday.

SLC WATCHES/WARNINGS/ADVISORIES

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