128 FXUS65 KVEF 170534 AFDVEF Area Forecast Discussion National Weather Service Las Vegas NV 934 PM PST Mon Dec 16 2019 .SYNOPSIS...High pressure will bring quiet weather through Tuesday except for gusty north winds down the Colorado River Valley. A weak disturbance will pass by Wednesday with increased cloud cover, then high pressure will return Thursday through Saturday. A series of Pacific storm systems could bring wet periods from early next week through Christmas. && .UPDATE...It's a clear and crisp evening across the region tonight with 9 am temperatures in the Las Vegas Valley 6-11 degrees colder than this time last evening. Across the rest of the forecast area, temperature trends compared to yesterday range from 2 degrees cooler at the Daggett Airport to 14 degrees colder at the Tonopah Airport in central Nye County. If current trends hold for Las Vegas, we could see morning lows along the city edges in the mid to upper 20s with valley wide temperatures at or below freezing. Up in the Spring Mountains, the fire station had a low of 8 degrees this morning and could end up closer to 0 degrees Tuesday morning. Updated the Tuesday morning minimum temperature grid to reflect what could be a very cold start to the day. && .PREV DISCUSSION... /issued at 233 PM PST Mon Dec 16 2019/ .DISCUSSION... A dry cold air mass and decreasing winds tonight will result in subfreezing temps across most desert areas away from the Colorado River Valley. Low temps will dip into the upper 20s to lower 30s across the Las Vegas Valley. Stiff north winds will persist down the Colorado River Valley Tuesday between Cottonwood Cove and Lake Havasu. The latest high res models indicate speeds will be quite similar to those observed today which have been sustained 20-25 mph with gusts 30-35 mph. Even though a ridge of high pressure will move overhead Tuesday, cold air will remain trapped in the valleys and temperatures will not vary much Tuesday afternoon and again Tuesday night. Wednesday will bring a quick change in the weather pattern as a Pacific trough quickly moves inland as an open wave. Considerable mid and high level clouds will precede the disturbance, but it will not have much of an impact except for some brief light snow over the southern Sierra early . The shortwave lifts away to the east Wednesday night followed by a broad ridge of high pressure over the weekend which holds through Saturday. Increasing southwest winds will develop late in the weekend which will bring temperatures up ahead of what looks to be a significant weather pattern change with a broad and deep long wave trough over the eastern Pacific which will set the stage for a potentially active week from Monday leading into the busy Christmas travel period. 20-30 percent chances of precipitation enter the picture Monday for the entire region as 2-3 large Pacific Systems appear to be lining up to impact the western states next week. Confidence in any details is still quite low for now, but ensemble means agree on an unsettle period shaping up with the potential for widespread precipitation. && .AVIATION...For McCarran...Northeast winds will drop below 10 knots shortly after sunset followed by a light northwest component late in the evening and overnight. Another round of northeast winds with speeds around of 10 knots appears likely Tuesday from mid morning through the afternoon hours. For the rest of southern Nevada, northwest Arizona and southeast California..VFR conditions and prevailing north to northeast winds generally less than 20 knots will continue across the most of the region tonight and Tuesday. The exception will be the lower Colorado River Valley where north winds gusting 25-30 knots can be expected from Laughlin-Bullhead City to Lake Havasu during daylight hours. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ UPDATE...Salmen DISCUSSION/AVIATION...Adair && For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter