textproduct: Salt Lake City

KEY MESSAGES

- Critical fire weather conditions will persist across much of central and southern Utah through Wednesday. - Strong to severe thunderstorms may form across northern UT Tuesday afternoon. Gusty outflow winds and potentially severe hail appear to be the primary threats.

- A warming and drying trend establishes by Friday and persists into the weekend with high temperatures climbing above climatological averages.

DISCUSSION

Over the next 6 to 12 hours, the base of a broad trough over the PacNW region will pivot into northern Utah, helping to push a cold front into the northern half of the forecast area. Satellite imagery reveals a veil of cloud cover already draped across the western half of the area as moisture in the mid and upper levels increases, with radar returns showing weak echoes across southern Idaho and northwest Nevada (tied to the increasing lower level moisture focused along the leading edge of the cold front). This area of showers will continue to push into northwestern Utah through the overnight hours, with covering increasing substantially by around 3-4AM as the cold frontal boundary progresses farther into the region. This boundary is expected to progress into central Utah before losing strength, however, virtually no precipitation is expected south of the Wasatch Front. The cold front and associated precipitation will continue across northern Utah and southwest Wyoming through the morning and early afternoon hours, bringing cooler temperatures and upwards of around 0.1 inches of rainfall from the Ogden area northward through around 12PM.

As the boundary continues eastward, skies will gradually clear and allow for daytime heating to build instability in the post-frontal environment. This instability paired with the increased lower- level moisture will bring a threat of strong to severe thunderstorms after about 1-2PM in far northern Utah from the the Raft River Mountains eastward through the Cache Valley, and north of Brigham City.

The base of this broad trough will remain draped across the region through Thursday, leaving a cooler airmass in place for the northern half of the area, helping to favor below normal temperatures for this time of year. Before the trough moves out of the area, however, another trailing shortwave trough is expected to push through the northern half of the area. As a result, yet another cold front will push through much of the forecast area, but this time dry conditions are expected to prevail.

Friday forward, a dry and hot return flow will spread over Utah, allowing for daytime high temperatures to climb back above normal areawide alongside very dry conditions. As part of this broad southerly return flow, moisture is expected to increase across the Desert Southwest late in the week and over the weekend. There is still a great deal of uncertainty in how far north this moisture will push, and whether or not southern Utah gets into the mix. Current model guidances is showing less than a 25% chance of moisture increasing enough in the lower levels to produce meaningful precipitation for areas south of the I-70 corridor.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions will persist across all terminals this evening with elevated winds persisting on occasion across our southern UT terminals. Some scattered thunderstorm development is expected across northern UT tomorrow afternoon after 18z with the highest confidence of impacts occurring near KLGU and perhaps KEVW and KOGD.

FIRE WEATHER

A trough will continue to shift eastward, with an associated cold frontal boundary dipping southward into Utah. This will bring shower and thunderstorm chances to northern Utah through Tuesday, particularly north of I-80 and nearer the Idaho border. Winds will also shift more west to northwesterly following the frontal passage, and bring modestly calmer winds which will help to abate critical fire weather conditions behind it accordingly. That said, the initial passage of the front will likely result in a brief period of breezy conditions as it passes.

The front is unlikely to make it much further then central Utah through Tuesday, allowing gusty southwest winds to once again develop across southern and eastern Utah, and central Utah ahead of where the fronts progress is halted. With these gusts likely in the 30-40 mph range and humidity once again in the low teens to single digits, widespread areas of critical fire weather conditions are expected. The front will make some additional southward progress into Wednesday allowing some portions of western Utah to see some relief in regards to stronger wind gusts, but westerly winds with gusts 25-40 mph will persist across southern to eastern Utah, yielding another day with areas of critical fire weather conditions.

Thursday on into the weekend will see deeper flow shift more west to northwesterly as the trough continues to shift east. Winds will relax in turn, but with widespread daytime humidity values in the teens to single digits and limited overnight recovery, elevated to locally critical areas of fire weather conditions are anticipated where winds do pick up sufficiently.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Red Flag Warning until 10 PM MDT this evening for UTZ492-495-497.

Red Flag Warning until 10 PM MDT Wednesday for UTZ484-489-493- 494-496-498.

WY...None.