250 FXUS65 KVEF 020441 AFDVEF Area Forecast Discussion National Weather Service Las Vegas NV 841 PM PST Mon Feb 1 2021 .SYNOPSIS...Subtropical moisture resulted in mostly cloudy skies across the forecast area. Light showers and virga possible south and east of Interstate 15 this afternoon. Another system will drop down the Western CONUS this week, but is increasingly looking like a wind maker as opposed to a rain maker. Enhanced westerly winds expected Wednesday and northerly winds expected Thursday with temperatures rebounding back to seasonal averages for the weekend. && .UPDATE... Light radar returns continue to stream across areas primarily south of I-40 in Mohave and San Bernardino County this evening. Most areas did not see any rain on the the ground today but the southern half of Mohave County was able to eek out a few hundredths fo an inch over the last six hours. A wide swath of dense cloud cover also accompanied this subtropical moisture surge and should slowly shift eastward along with any straggling showers over the next few hours. Lows tonight will be a few degrees cooler than yesterday even though today's highs were warmer with the exit of the cloud cover. Made minor tweaks to the Pop/QPF for the overnight period to account for current trends. && .DISCUSSION...Today through the Weekend. Subtropical moisture resulted in mostly cloudy skies across the region today. Due to the cloud cover overnight preventing much of a cooldown, this afternoon's high temperatures have hovered right around seasonal normals. The strongest band of clouds remains south and east of I-15, where light precipitation chances remain this afternoon. Rainfall totals today will range from a trace to a hundredth of an inch, with much more in the way of measurable rainfall not expected. In many instances, rain will evaporate before it reaches the ground, called virga showers. In some instances, erratic wind gusts may result from rain-cooled air dropping all at once, but this occurrence would be very isolated, if it happens at all this afternoon. Tuesday will be the most mild day of the forecast period, with above- average temperatures, light winds and mostly sunny skies expected across the region. However, high-resolution models are beginning to pick up on the potential for downslope winds off the Spring Mountain Range Tuesday night, which I blended in with NBM in this afternoon's forecast package. Going into Wednesday, winds become the primary story as we brace for a cold frontal passage. Currently, an area of low pressure is spinning off the coast of the Pacific Northwest. The associated trough will dip down the coast with a westward trajectory into the Pacific through the day on Tuesday before eventually splitting. The trough will become a closed low, leaving the remaining split energy to push eastward across the Continental US. While the closed low spins off the Baja Coast, the remaining trough will bring with it a cold front that will push through our forecast area on Wednesday. Meanwhile, a fairly robust upper-level jet streak (+120kts at 250mb) will set up late Tuesday into Wednesday, which will help amplify pre- frontal winds across the Mojave Desert. Originally a potential rain- maker, precipitation chances will remain north of our CWA as both precipitation chances and amounts continue to dwindle with each model run. Less than a tenth of an inch of rain possible in northern Mohave and northern Inyo counties, if any, through the event. Wednesday afternoon, west-southwesterly winds will gust, approaching Wind Advisory criteria. As such, we will continue to follow forecast trends and issue if necessary. Though gusts will subside after sunset, winds will remain elevated areawide overnight into Thursday before the trough and upper-level jet streak and push out of our area. Thursday, winds will remain elevated, as northerly flow sets up aloft. Northerly winds will enhance along the southern Great Basin as well as down the Colorado River Valley. Isolated areas may reach Wind Advisory criteria, though the more likely scenario may end up being a Lake Wind Advisory, as wave heights could range from 2 to 3 feet on Lake Mohave, creating dangerous conditions for those operating small craft. Due to the cold frontal passage, high temperatures on Thursday will range 6-10 degrees cooler than Wednesday's highs. On Friday, a shortwave trough will push through the area, resulting in tightening gradients once again along the Colorado River Valley, where breezy northerly winds will set up in the afternoon. Otherwise, temperatures will begin to rebound back to seasonal averages over the weekend. There is low confidence with the long term forecast. The cut-off low that split from the trough that passed through the Desert Southwest midweek is expected to remain spinning off the Baja Coast through the remainder of the week and weekend. Models are suggesting that it will return to land late Sunday into Monday. Deterministic runs indicate that this low pressure will remain south of our area, bringing rain chances to northern Mexico and southern Arizona. However, several ECMWF Ensemble members highlight a chance for precipitation in our CWA for the start of next week. Stay tuned! && .AVIATION...For McCarran...Ceilings at or above 9000 feet will persist at the terminal through much of Tuesday. There will be a chance for ceilings to drift down below 8000 feet between about midnight and 7 AM Tuesday morning, but confidence in this is not high enough to include in the TAF. No operationally significant winds or weather expected. For the rest of southern Nevada, northwest Arizona and southeast California...Clouds will slowly decrease across the region from northwest to southeast tonight and Tuesday. The best chances for ceilings low enough to obscure higher terrain will be southeast of Interstate 15 through sunrise Tuesday morning, with a few sprinkles or light showers possible as well. No operationally significant winds expected through Tuesday night. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ DISCUSSION...Varian AVIATION...Morgan For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter