Area Forecast Discussion
Issued by NWS Salt Lake City, UT
Issued by NWS Salt Lake City, UT
406 FXUS65 KSLC 181023 AFDSLC Area Forecast Discussion National Weather Service Salt Lake City UT 423 AM MDT Tue Jun 18 2024 .SYNOPSIS...A much cooler day will be experienced on Tuesday across the region behind a strong cold front. Temperatures will return to normal by Wednesday then back above normal through the weekend when another period of very hot temperatures build into the area. Before then, anomalous moisture will build into eastern Utah late Thursday through Friday, bringing showers and thunderstorms. && .SHORT TERM (Through 12Z/6AM Thursday)...Much cooler temperatures have built into Utah and SW Wyoming behind an unseasonably strong cold front that blasted through the area on Monday. Near freezing to below freezing temperatures are in place across portions of the Wasatch Back as well as the Bear River Valley and outlying portions of the Cache this morning. One pocket of gusty winds remains in place across SW Utah early this morning, thanks to the presence of a strong pressure and thermal gradient. NE gusts remain around 45 mph near the mouth of Black Ridge Canyon, with isolated stronger gusts. These winds will begin to back off shortly after sunrise. Meanwhile, tranquil conditions will be in place through midweek across the area. Under building mid-level heights, Wednesday`s temperatures will rebound to near seasonal normals for mid-June after an unseasonably cool day on Tuesday. .LONG TERM (After 12z/6AM Wednesday)...Ensemble guidance remains in great agreement on a trough remaining upstream of the forecast area through at least early Friday with a ridge building into the area Friday through the weekend. Past Sunday, models diverge a bit as there is some uncertainty on the depth of a trough progged to move through southern Canada. The depth of this trough will ultimately influence the temperature trends (mainly in the northern area) through next week. A trough upstream of the area during the latter portion of the week will continue to promote warm and dry southwesterly flow over the forecast area, allowing temperatures to warm back to above normal levels. To the east of the area over the southern Plains, an wave propagating to the west will interact with the upstream trough and bring an increase in lower level flow as well as initiating a moisture flux into the eastern Great Basin region. Increased flow in the lower levels will bring increasing surface winds during the afternoon on Thursday. The increase in flow will bring concerns of elevated fire weather conditions in eastern Utah before the near surface moisture arrives. At this time, no fire weather headlines have been issued as fuels are not currently over their critical thresholds in the zones of concern. Moisture continues to work into the area through the evening hours on Thursday, while the aforementioned trough begins shifting over the region. Isolated showers and thunderstorms over eastern Utah will be possible, and will carry the threat of dry lightning as the lower level moisture lags. Should expect to see an increase in shower activity through the overnight hours as upper level support for lift increases. Going into Friday, upper support and increasing moisture in the lower levels will act to destabilize the environment and bring an increasing threat of strong thunderstorms and flash flooding (model PWAT anomalies continue to push 200-250% of normal over eastern Utah). Will need to continue to assess the threat of flash flooding on Friday afternoon as models maintain abnormally moist conditions over eastern Utah. The one concern with this is whether or not the added dynamics from the trough will bring too much cloud cover to destabilize the environment to the potential that the models are suggesting. In general, if you`re planning a slot canyon trip, you might want to hold off until late in the weekend. A stout ridge builds back over the region late in the weekend, which will help to reinforce hot conditions areawide as well as provide a drier environment. Confidence is increasing that the Wasatch Front will be pushing temperatures to near 100 degrees and into the mid- to upper-100s for lower elevations in southern Utah by Sunday. Will need to continue to assess the need for heat related headlines by Sunday as overnight lows will provide minimal recovery from the heat. Thankfully for the northern portions of Utah and southwest Wyoming, the heat looks to be fairly short lived as an active storm track resumes to the north of the area, which should tamper down the strength of the high. There is still uncertainty on how much the high will be repressed by the northern stream, but in general we should expect a gradual cooling trend into the middle portion of the week across the northern half of the area. For the southern area, heat looks to be maintained unless we can develop a deeper trough into the CONUS (supported by ~30% of ensemble members). && .AVIATION...KSLC...VFR conditions will prevail over the KSLC terminal through the valid TAF period. Winds will become light and variable, with periods of prevailing southerlies, through the early to mid-morning hours. A return to northerly flow is expected after 17Z. .REST OF UTAH AND SOUTHWEST WYOMING...VFR conditions under high level cloud cover will prevail through the day. Winds will prevail out of a predominant northerly direction across the region, with strong winds in lower Washington County decreasing in speed through the morning hours. && .FIRE WEATHER...Dry and steadily warming temperatures are expected for the next couple of days after the passage of an unseasonably strong cold front on Monday. Temperatures on Tuesday will range from 5F to 15F below normal across central and southern Utah, to as much as 20F below normal across northern Utah. Temperatures will return to normal by Wednesday and back to 5F to 15F above normal by Thursday, with poor overnight recovery most areas. A few pockets of critical fire weather conditions will develop across wind-prone areas of southern Utah on Thursday due to the combination of gusty southwest winds and low humidity between 8 and 15 percent. A surge of moisture will then begin to work into eastern Utah from the southeast by late on Thursday, with a significant increase in moisture expected to move into areas generally along and east of I-15 for Friday. On the leading edge of this moisture surge from late Thursday into early Friday, isolated dry lightning will be possible. Widespread showers with isolated thunderstorms are then expected across eastern Utah on Friday, with widespread 50% and above chances for wetting rains. Dry conditions are then expected to quickly build back into the area for next weekend, with isolated thunderstorms possible for eastern areas on Saturday. Hot and dry conditions will be the rule for Sunday across the state, with many northern valley locations approaching or exceeding 100F. && .SLC WATCHES/WARNINGS/ADVISORIES... UT...Freeze Warning until 9 AM MDT this morning for UTZ107-108. High Wind Warning until 8 AM MDT this morning for UTZ123. WY...None. && $$ ADeSmet/Webber For more information from NOAA`s National Weather Service visit... http://weather.gov/saltlakecity