textproduct: Salt Lake City

KEY MESSAGES

- Temperatures will stay mild for Memorial Day, with scattered afternoon showers with a few thunderstorms developing over the higher terrain. Any storms that develop will be capable of producing gusty and erratic winds.

- Increasing winds will bring the potential of critical fire weather conditions to southwest Utah beginning Tuesday, with a medium chance of some gusts in excess of 40 mph over western Utah. Gusty winds will be more widespread across the state on Wednesday, with a higher potential for strong gusts. The potential for critical fire weather conditions will linger through at least Thursday over eastern Utah.

DISCUSSION

The ridge axis that has been over Utah and southwest Wyoming is shifting eastward into Colorado this evening. Shortwave energy moving over the top of the ridge into northern Utah brought some scattered convection this afternoon that has mostly diminished at this time. Temperatures were near seasonal normals over southern Utah, with maxes running up to 10F above climo for northern Utah.

A trough will be moving onshore along the Pacific Northwest coast on Memorial Day as southerly flow develops over Utah and southwest Wyoming. This flow will start to draw moisture and instability in the form of some weak shortwaves into the area during the day. Thus, another round of afternoon convection is expected, mainly over the higher terrain, with coverage most widespread over southern Utah. Lower levels are still on the dry side so the main threat will remain gusty and erratic thunderstorms winds.

There is high confidence that the Pacific Northwest trough will drop south into the Great Basin on Tuesday. The stouter pressure gradient will bring increasing winds to western Utah, likely to produce critical fire weather conditions were fuels are dry over southwest Utah. For there and the remainder of western Utah, most likely wind speeds have gone up a bit in this evening's guidance, with an approximately 50-50 chance of gusts in excess of 40 mph, mainly across areas closer to the Utah/Nevada border.

As the low continues edging eastward for the middle of the week, the areal extent of gusty winds is expected to increase for Wednesday. Thus, the potential for critical fire weather conditions will become more widespread, though increasing relative humidities may be a bit of a limiting factor. Will also need to continue to watch for the potential of wind gusts in excess of 40 mph, with latest guidance still showing about a 50-50 chance of more widespread gusts in excess of 40 mph.

Beyond the midweek period, model spread increases with regard to the evolution of the Pacific Northwest low, which is to be expected as guidance typically struggles with weakening closed lows, as this one is expected to be at that point. The most likely scenario is for the low to track northeast over the area as it opens up. Overall, moisture and instability look unimpressive at this point, but the position of the upper jet over eastern Utah may result in that area becoming a focus for convection late in the work week. Drier conditions are expected to move in for the upcoming weekend with high pressure moving in, with some guidance indicating that this may be somewhat short lived.

REST OF UTAH AND SOUTHWEST WYOMING

Winds will be largely diurnally-driven overnight, with scattered showers and thunderstorms redeveloping after 18z Monday. Any storms may be capable of producing gusty and erratic outflow winds. VFR conditions will prevail.

FIRE WEATHER

Moisture and instability will remain in place over Utah for Memorial Day, bringing scattered showers with a few thunderstorms during the afternoon, primarily over the higher terrain and with the best coverage over southern Utah. The chance of wetting rain is limited at best with gusty and erratic winds likely with any storms that develop. The potential for critical fire weather conditions will increase over southwest Utah on Tuesday as a Pacific Northwest trough drops into the Great Basin, bringing an increase in winds. The gusty winds will become more widespread across the area on Wednesday, though relative humidities will be increasing during this time. As the trough crosses the area Thursday into Friday, the potential for critical fire weather conditions will continue over eastern Utah.

SLC WATCHES/WARNINGS/ADVISORIES

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