FXUS65 KVEF 250814 AFDVEF Area Forecast Discussion National Weather Service Las Vegas NV 114 AM PDT Fri Oct 25 2024 .SYNOPSIS...Warm and dry conditions will continue through Sunday under high pressure. A significant change in the weather pattern arrives Monday as low pressure from the Gulf of Alaska brings increased winds, cooler temperatures, and precipitation potential to parts of the forecast area. && .SHORT TERM...through Sunday night. Midnight satellite loop showed scattered cirrus moving east over Mohave, Lincoln, Clark, and eastern San Bernardino counties, with clear skies farther west. Surface obs showed light winds and temperatures a few degrees lower on average than 24 hours ago. Very little change in forecast thinking. High pressure will remain in place through Saturday, keeping dry weather and above normal temperatures in the forecast, with periods of passing high clouds. Sunday and Sunday night will be when things start to change. As noted yesterday, the leading shortwave trough will be coming into the West Coast ahead of the main low nearing Vancouver Island. This will increase surface pressure gradients, upper level winds, and thermal gradients, causing winds to pick up Sunday and especially Sunday night. Wind Advisories may be needed for the Barstow area as early as Sunday night. The increasing winds and deeper mixing will offset or even outweigh falling heights, so temperatures will not fall from Saturday to Sunday and may even rise a bit more. NBM 4.2 via the WSUP 1-D viewer still gives a 50 percent chance for Las Vegas to reach 90 degrees on Sunday. .LONG TERM...Monday through next Friday. Attention turns to a closed low as it approaches the western coast of Canada through the weekend. By the start of the next work week, the associated trough will have dug through the western CONUS, with the trough axis pushing through the Mojave Desert on Monday. We remain confident in the timing and placement of this system, as well as the temperature drop that will correspond with the cold frontal passage. Temperatures will drop 15 to 20 degrees between Sunday and Wednesday, shifting the region from above-average temperatures to below-average temperatures for the remainder of the forecast period. Along with a stark drop in temperatures, we can expect gusty pre- frontal southwesterly winds on Monday. As mentioned in the previous forecast discussion, the NBM continues to highlight a band of 75-95% chance of gusts exceeding 40 mph from western San Bernardino County through Las Vegas into northern Mohave County / the Arizona Strip on Monday. Post-frontal northwesterly winds will take over across the region through the day on Tuesday, but are not forecast to be as strong as the pre-frontal winds with this event. This is likely due to the fact that the trough will have a more eastward trajectory (rather than a south-southeastward trajectory) than last week's wind event, creating less favorable upper-level pressure gradient directions. Finally, precipitation chances will increase with this system. As mentioned previously, this remains the least confident part of the forecast, as the moisture increase does not temporally line up well with the needed dynamics. However, the mountains and other areas of higher terrain can expect increased precipitation chances due to assistance from orographic lift. Due to snow levels dropping between 5000 and 5500 feet Monday evening, higher elevations of Lincoln County can expect a dusting of snow. Wednesday onward, an active fall-like weather pattern continues, though details are unclear at this time. && .AVIATION...For Harry Reid...Wind speeds of 8 knots or less will continue again today and favor an easterly direction from late this morning through the afternoon and a westerly direction this evening into Saturday morning. VFR conditions will prevail through the TAF period with clear skies through the afternoon followed by FEW to SCT high clouds with bases AOA 15kft moving across the valley overnight and Saturday. For the rest of southern Nevada, northwest Arizona and southeast California...Winds will remain less than 10 knots and favor typical diurnal directions today into Saturday. VFR conditions are expected at all regional TAF sites, although a FEW to SCT high clouds with bases AOA 15kft will move across the area west to east beginning late this afternoon and continue into Saturday morning. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ SHORT TERM...Morgan LONG TERM...Soulat AVIATION...Planz For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter