textproduct: Salt Lake City

KEY MESSAGES

- Areas of critical fire weather conditions will return to portions of southern Utah Saturday and Sunday afternoons.

- A quite unseasonably cold storm system will result in temperatures 10-20F below normal for Sunday and Monday along with accumulating mountain and mountain valley snow, potentially significant for some northern Utah mountains.

- Freeze conditions will impact many Utah valleys outside of the Wasatch Front Monday and Tuesday mornings. Some areas that might see a hard freeze include the Cache Valley, Wasatch Back, west central Utah, southwest Utah, and the Sanpete Valley.

DISCUSSION

Utah and southwest Wyoming remain under a dry and mild zonal flow aloft ahead of a storm system starting to move onshore along the Pacific Northwest coast. Tranquil conditions will persist today with maxes 5-10F above normal, with the greatest departure from normal over southern Utah.

The main cold trough will be parked over the Pacific Northwest tomorrow, with a small wave splitting from it into the Great Basin. This is expected to move a weak initial cold front across northern Utah during the day Saturday, providing enough instability for scattered afternoon showers across the higher terrain. It will also bring highs back around seasonal normals for northern portions of the forecast area. Gusty southerly winds ahead of the boundary will combine with the dry conditions to produce areas of critical fire weather conditions. See the fire weather section of the AFD for more details.

There is high confidence that the main Pacific Northwest trough will dive southeast, tracking across the forecast area Sunday into Monday. the most noticeable impact from the system will be on temperatures, with maxes running up to 20F below seasonal normals both Sunday and Monday, bringing temperatures more typical of early March than mid May. These cold temperatures will bring freezing temperatures and the potential for hard freeze conditions to most northern Utah valleys and mountain valleys outside of the Wasatch Front across northern and central Utah. Seeing a slight upward trend in mins in the guidance, so will hold off on any Freeze Watches this far out.

Accumulating snow for all of Utah's mountains as well as most mountain valleys is also looking increasingly likely, and amounts have trended upward just a bit with the morning forecast package. Amounts between two and six inches look most likely for most mountain valleys and mountains, but guidance is indicating amounts up to a foot for parts of the Western Uintas. If forecast totals continue to trend upward, the snow could be significant for that area.

Ahead of the trough, winds become breezy on Saturday and will be even stronger across portions of southern Utah on Sunday. Overall, there seems to be a decent chance of isolated wind gusts in excess of 40 mph for southern Utah Sunday afternoon, with a less than 50 percent chance of these gusts being long lasting.

Confidence is high in temperatures steadily rebounding for Tuesday and beyond under the influence of a ridge off the Pacific coast. Conditions should be generally dry, but a subset of guidance indicates another weak trough on the tail end of the cold Pacific Northwest system moving across northern Utah Tuesday afternoon. If this materializes, the result would be some additional showers over the higher terrain of northern Utah, with noticeably higher snow levels given the rapid warming.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions will persist through the TAF period. Winds will remain light and terrain driven through mid-morning today before northwesterly flow prevails in most areas as upper level flow picks up. As the next system pushes in Saturday morning, expect widespread stronger northwesterly through northerly winds especially for the northern half of Utah and southwest Wyoming. Light showers falling into a much drier lower atmosphere will limit the chances of seeing showers at most sites, but could drive gusty and erratic winds in their vicinity.

FIRE WEATHER

Dry and mild conditions will continue into Saturday, with high temperatures near to 5F above seasonal normals across northern Utah and up to 10F above normal over southern Utah. With the approach of a cold Pacific Northwest storm system, winds will become breezy by Saturday afternoon. This will combine with the dry conditions over southern Utah to produce areas of critical fire weather conditions. Thus, a Red Flag Warning has been issued for most of the valleys of southern Utah for Saturday. The storm system will cross Utah Sunday into Monday, bringing temperatures up to 20F below seasonal normals both Sunday into Monday. Relative humidities will come up significantly over the area, but are still expected to be critically dry over far southern Utah. With winds a bit gustier than Sunday, have continued the Red Flag Warning into Sunday across far southern Utah. Snow levels are expected to drop as low as 5000 feet Sunday into Monday, with most mountains and mountain valleys seeing between two and six inches of snow. The exception will be portions of the western Uinta mountains, where up to 12 inches of new snow is possible. Behind the trough, the area will see a steady warming trend beginning Tuesday along with a drying trend.

SLC WATCHES/WARNINGS/ADVISORIES

UT...Red Flag Warning from 11 AM to 9 PM MDT Saturday for UTZ489-494- 495.

Red Flag Warning from 11 AM Saturday to 9 PM MDT Sunday for UTZ497-498.

WY...None.