Key messages
- Another night of freezing temperatures will impact the Sanpete and Sevier Valleys as well as eastern Juab and Millard Counties tonight.
- A few thunderstorms will be possible Sunday afternoon and evening and again Monday afternoon and evening.
- More widespread precipitation will occur Tuesday through at least the early part of the weekend, with another 0.50-1.50 inches for most locations, locally up to 2 inches (or even more) for areas that do well in southerly flow.
Discussion
A warming trend will continue as high pressure remains overhead through the first part of the weekend. A cut off upper level low currently over southern California will continue to retrograde westward. Meanwhile, the continued very active eastern Pacific will have at least two ongoing tropical cyclones (Simon and Trudy). As the upper level low continues to shift westward, tropical moisture from weakening Tropical Storm Simon will be drawn northward into Baja California and eventually the Desert Southwest Sunday.
This upper level low will eject across the Desert Southwest ahead of the next Pacific trough Sunday. PW anomalies from this moisture advection ahead of the low will reach near 90-95th percentile across southern Utah. While it is mid-October, if sufficient destabilization occurs, a few thunderstorms capable of heavy rain will develop Sunday afternoon and evening across southern Utah. This threat will continue Monday afternoon and evening.
The previously mentioned upper level trough will be off the central California Coast by Tuesday morning. Broad upper level divergence ahead of this upper level trough combined with PVA will support the develop of widespread precipitation across central and southern Utah by Tuesday afternoon. As this trough slowly crosses the West, additional periods of valley rain and high elevation snow will continue through at least the early weekend period. Rainfall totals (25th to 75th percentile) are averaging around 0.50 to 1.50 inches across most locations, with some areas that do well in southerly flow (northern Wasatch Front, Provo Canyon, southern mountains) likely seeing more than 2 inches. As far as snow, while it's over several days, looking like another 6 to 12 inches, mainly above 9000-9500 feet.
Going Freeze Warnings are on track and no changes will be made. No additional headlines are needed at this juncture.
Aviation
KSLC...VFR conditions prevail at the terminal under mostly clear skies. Light southeasterly winds continue overnight, transitioning to the northwest after roughly 19z.
REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions will prevail through the TAF period for all regional terminals. Winds remain generally light and diurnally driven for northern Utah terminals into Friday. Across southern Utah and southwest Wyoming, while lighter winds are expected overnight, gusty northerly to easterly winds redevelop Friday afternoon.
Fire Weather
High pressure will strengthen over the region through the first half of the weekend, allowing for temperatures to gradually rise while maintaining light winds areawide. A drying of the environment is also anticipated under this area of high pressure, most notably across the central Utah mountains today and then into the southern and northern mountains as well as the west-central and southwest valleys by Saturday. An impulse of moisture pushing northward on Sunday will bring isolated showers and thunderstorms to portion of southern Utah while the remainder of the area remains dry. An unsettled pattern will develop once again as we head through next week as another storm system sets its crosshairs on the eastern Great Basin region. Anticipate shower and thunderstorm activity to expand throughout the rest of Utah by as early as Tuesday and as late as Thursday as this storm system works its way through Utah.
Slc Watches/Warnings/Advisories
UT...Freeze Warning until 9 AM MDT this morning for UTZ116-118-119.
WY...None.
PUBLIC... AVIATION... FIRE WEATHER...Webber HYDROLOGY...
For more information from NOAA's National Weather Service visit... http://weather.gov/saltlakecity