502 FXUS65 KFGZ 140523 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 1023 PM MST Sun Apr 13 2025 .SYNOPSIS...A gradual cooling trend is expected this week with a chance of showers Monday night and Tuesday and again Thursday night into the weekend. && .UPDATE...Breezy conditions are keeping the boundary layer mixed in some locations this evening while other areas have decoupled. Will make minor adjustments for low temperatures tonight. High cloud cover will continue through the night as a fetch of high level moisture extends well over 1000 miles southwest of Arizona. && .PREV DISCUSSION /423 PM MST/...Today...An elongated trough remains over the West, keeping much of northern Arizona under mid and high level clouds through the day. Breezy southwest winds have also developed, especially across the eastern portions of the state. Monday and Tuesday...Moisture advection begins to increase with southerly flow ahead of a shortwave off the Baja California coast. With the increase in mid-level moisture, some virga will be possible on Monday, but any actual precipitation looks to hold off until the overnight hours. By Monday night, moisture looks to have increased enough so that once the shortwave (and corresponding forcing) arrives in Arizona, some showers look to develop. As of now, the best shot at any precipitation will mainly be over the higher terrain from about I-40 and northward late Monday night into early Tuesday afternoon. Model soundings still show a strong inverted-v appearance, indicating the very dry sub-cloud layer. Thus, any precipitation that does reach the surface is expected to be minimal, with the odds of a wetting rain highly unlikely. With the low overhead, lapse-rates do steepen enough going into the afternoon for a subtle increase in instability, around 100 J/Kg or so. Thus, some thunder can not be totally ruled out in any more vigorous showers (or virga) during the afternoon hours. Wednesday through Saturday...Drier air sets in behind the shortwave on Wednesday. However, breezier conditions look to return as a cut- off low spins off the coast of California and begins to eject off the Pacific. The pressure gradient looks to further increase as a secondary longwave trough begins to descend southward from the Pacific Northwest and eventually phase with the cut-off low. Even stronger southwesterly winds look to develop as a result on Thursday, potentially leading to another round of critical fire weather conditions as RH values will still be low across much of northern Arizona. As the now closed-low begins to move through Nevada, moisture begins to increase across Arizona. Rain (and high-elevation snow showers) look to develop as early as Friday across northwest Arizona, then increase in coverage through Friday. Precipitation looks to then peak on Saturday as the core of the low moves overhead. Most of the ensemble solutions seem to have narrowed in on the timing aspect of this system, however precipitation amounts are still uncertain, as the exact track will dictate how the amounts shake out. Regardless of any precipitation, colder and breezier conditions look to dominate the end of the week. && .AVIATION...Monday 14/06Z through Tuesday 15/06Z...VFR. Light and variable winds, becoming southerly 5-15 kts after 18Z. OUTLOOK...Tuesday 15/06Z through Thursday 17/06Z...Mainly VFR expected. ISO SHRA and VCTS mainly north of the I-40 corridor 12Z-22Z Tuesday. S-SW winds 10-15 kts with gusts 20-30 kts Tuesday and Wednesday afternoons with 10 kts or less during the overnight periods. && .FIRE WEATHER...Monday through Tuesday...South winds 5-10 mph on Monday, then south to southwest 10-20 mph Tuesday. Min RH values 8- 15% Monday and 10-20% Tuesday. There is a 10-30% chance of light showers on Tuesday with a few afternoon thunderstorms possible north of I-40. Wednesday through Friday...Cooler with increasing southwest winds. Dry conditions on Wednesday and Thursday with near-critical fire weather in eastern Arizona. Low pressure brings a chance of rain and snow showers Friday, with some thunder possible. Southwest winds 10- 20 mph Wednesday, increasing to 15-25 mph with gusts 30-40 mph Thursday and Friday. && .FGZ WATCHES/WARNINGS/ADVISORIES...None. && $$ PUBLIC...MAS/Humphreys AVIATION...Meola FIRE WEATHER...Meola For Northern Arizona weather information visit weather.gov/flagstaff