textproduct: Salt Lake City

KEY MESSAGES

- Gusty winds and low relative humidity will create areas of critical fire weather conditions across southern Utah Friday.

- A significant widespread heatwave will develop this weekend into early next week, with temperatures challenging daily, monthly, and even all-time high temperature records.

- Monsoonal moisture is expected to spread into the region by the middle of the upcoming week, bringing an elevated threat for flash flooding across southern Utah through the end of next week.

DISCUSSION

High pressure is centered off the southern California coast this evening. Southern Utah is under a dry westerly flow aloft, with a weak stalled boundary over central Utah. Northern Utah continues to see a bit of high based moisture which led to the development of a few showers and thunderstorms this afternoon into the early evening, some producing gusty winds in excess of 40 mph.

The ridge is expected to continue eastward overnight and during the day Friday, becoming centered over southern California by Friday afternoon. This will allow the very dry airmass over southern Utah to spread across the remainder of the forecast area as temperatures continue to warm. Maxes are expected to average 5-8F above seasonal normals across the area. Conditions should remain breezy enough over southern Utah to bring areas of critical fire weather conditions during the afternoon.

For Saturday, the ridge will continue to strengthen, with its center moving directly over Utah. Winds will decrease, but temperatures will continue to rise, running in excess of 10F above seasonal normals for northern portions of the area. These quite abnormally hot temperatures are expected to bring HeatRisk values into the red (major) range for many valleys and mountain valleys across the area by Saturday afternoon, and an Extreme Heat Warning will go into effect Saturday afternoon. For Sunday, the center of the ridge will move east of the area, but temperatures, already abnormally warm, are on track to become even hotter. Just about all valleys are forecast to see maxes of 100F or higher, with some mountain valleys around those values as well. Departures from normal will remain highest over northern Utah, where not only will daily records be in play, but monthly and all time records as well. For example, the current forecast for Logan shows a high of 107F, which would shatter the all time record there. Guidance currently shows Salt Lake City with a 30 percent chance of meeting or exceeding the all time high temperature record of 107F on Sunday afternoon. Needless to say, the Extreme Heat Warning will remain in effect.

Models continue to be consistent and in good agreement in showing monsoonal moisture being drawn northward as early as late Sunday/early Monday as the ridge continues east and puts Utah and southwest Wyoming under southerly flow aloft. This moisture will most likely increase through the middle of the upcoming week, and stick around for much of the remainder of next week. Thus, anticipating temperatures will become a bit less hot (but still noticeably above normal), with increasing chances of showers and thunderstorms and the potential for flash flooding, particularly for southern Utah.

AVIATION...KSLC

VFR conditions are expected to prevail through the valid TAF period under partly cloudy skies. Southerly winds will be maintained through the overnight hours with high level cloud cover slowly dissipating by early morning. A return to northwesterly winds is expected during the early afternoon on Friday.

REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions are expected areawide through the valid TAF period, with ongoing rain showers in eastern Utah expected to diminish before midnight. Isolated showers and thunderstorms can be anticipated over the high terrain of northern Utah east of the I-15 corridor on Friday afternoon. Expect light diurnally driven overnight flows to transition to a southwest wind by mid-morning to early-afternoon on Friday, with peak winds around 10-15 kts.

FIRE WEATHER

West to southwest flow across the area will bring an increasingly dry airmass into the area tomorrow through the weekend. Winds are expected to remain breezy enough during the day Friday to produce areas of critical fire weather conditions. However, the presence of a very strong ridge over the weekend will result in generally light winds, though high temperatures will be quite unseasonably hot, breaking daily records, and likely monthly and all time high temperature records as well. The ridge will find its way east of the area by Monday, and the resultant southerly flow will draw monsoonal moisture northward through at least the middle of the upcoming week, with the moisture most likely stay in place through the end of next week. This will bring slightly less hot temperatures, but will also bring an increased potential of wetting rainfall.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Extreme Heat Warning from noon Saturday to 6 AM MDT Tuesday for UTZ101>108-114-116-118>121.

Extreme Heat Warning from noon Saturday to 6 AM MDT Monday for UTZ115-122-128>131.

Red Flag Warning from noon Friday to midnight MDT Friday night for UTZ495-496-498.

WY...Heat Advisory from noon Sunday to 9 PM MDT Monday for WYZ021.