373 FXUS65 KFGZ 071155 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 455 AM MST Thu Oct 7 2021 .SYNOPSIS...Expect dry weather Thursday, along with breezy afternoon winds. A chance for showers returns Friday for northwestern Arizona. Some rain chances linger over far northern Arizona for much of the weekend with most areas expected to remain dry. A significant change to the weather is expected next week as a very cold system moves through Tuesday bringing a Hard freeze to the region down to 5000 ft. && .DISCUSSION...Temperatures are mild across the region as a blanket of mid to high clouds stream in from the southwest. The models are on track with satellite imagery placing the descending trough off the northern California coast. The trough is forecast to continue tracking south off the coast before turning inland across south- central California into the Great basin and setting up a longwave trough system across the Western US. Guidance tends to agree with this track, keeping most of the precipitating to the northwest of the San Francisco Peaks over the Coconino Plateau and areas north. The European model tracks the trough slightly farther south which would significantly change the forecast drawing the precip band south into Yavapai County and the western Mogollon Rim. A deep plume of moisture pushes into the region Friday morning ahead of the trough, increasing PWats to 0.75 to 0.95 inches through the day. A cooling of just a couple degrees at 500 mb heights would be enough instability to support showers and a few thunderstorms across Yavapai County and as far east as the Strawberry-Pine and Payson areas Friday afternoon and evening. The current forecast has two to three tenths inch precip over the Kaibab Plateau, but the latter scenario could push these amounts south into the Yavapai County and Flagstaff areas. Though there is little confidence in this scenario, it will be something to watch over the next 12 hours as the guidance picks up more on the mesoscale and CAM models. Two more shortwave troughs move across northern Arizona through the longwave pattern Saturday and Sunday, keeping unsettled weather in the forecast through the weekend along and within about 70 miles of the Utah border. The third shortwave has a dry cold front associated that will move through the region Saturday night into Sunday, dropping temperatures five to ten degrees and shifting the winds northerly. Looking at the next system, a deep cold low pressure system that drops south through the Great Basin Monday night into Tuesday will bring a big change to the weather. Each successive model run for the last couple days has cooled this system. The latest run of the GFS and European models puts snow in the forecast for the Flagstaff area with accumulations up to a half inch along and west of the Arizona Divide and one to two inches possible on the San Francisco Peaks and the Kaibab Plateau. Modeled soundings for the region support the snow forecast with near saturation in the dendritic growth zone. They're even hinting that the Prescott area could see a flurry Tuesday morning. There is currently low confidence in the snow forecast, but high confidence that this system will bring much colder weather to the region with temperatures falling 15 to 20 degrees. Expect morning lows in the teens to low 20's across the High Country and a hard freeze (< 28F) down to 5000 ft Wednesday morning. This system has strong jet support and a tight pressure gradient. The european ensemble forecasts strong gusty winds Tuesday as this system moves through. Expect winds gusting 30-40 mph across much of the region and gusts of 45-65 mph possible from Flagstaff southeast along the Mogollon Rim to the White Mountains. We will have a better handle on these winds by Sunday; stay tuned. Beyond Wednesday, the models diverge with the GFS building in a ridge and warming the region, while the European and Canadian models maintain the longwave trough over the western US into the following weekend with cooler, unsettled weather over northern Arizona. Stay tuned as we go through the weekend to see how this works out. && .AVIATION...For the 12Z package...Expect VFR conditions under varying amounts of mid and high level cloudiness over the next 24 hours. Winds will remain light, generally at 10 kts or less. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Expect dry conditions and light winds with little change in temperatures today. Winds will be on the increase Friday as a weather system approaches with afternoon gusts of 25 to 35 mph. Rain showers will be possible by Friday afternoon, mainly from a Prescott to Flagstaff line north and west. Saturday through Monday...The active fall pattern will continue with cooler temperatures and chances for precipitation. Breezy winds on Saturday and Sunday will increase on Monday with the approach of another weather system. && .FGZ WATCHES/WARNINGS/ADVISORIES...NONE. && $$ PUBLIC...DB AVIATION...McCollum FIRE WEATHER...McCollum For Northern Arizona weather information visit weather.gov/flagstaff