Area Forecast Discussion
Issued by NWS Flagstaff, AZ
Issued by NWS Flagstaff, AZ
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758 FXUS65 KFGZ 200517 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 1017 PM MST Thu Sep 19 2024 .SYNOPSIS...Seasonably cool temperatures remain through Saturday, before warmer temperatures return next week. A cold front will bring a chance for showers and possibly thunderstorms to the area late Friday into Saturday, with otherwise dry conditions expected. && .UPDATE...A few high clouds are drifting into the region ahead of our next low pressure system, currently centered over southern California. Seasonable temperatures and dry weather will continue overnight with no forecast updates needed. See the discussion below for more on the expected impacts of this approaching low. && .PREV DISCUSSION /431 PM MST/...Arizona remains under a mild southerly flow ahead of a Pacific low pressure system moving southward along the California coast. A mild and breezy day is underway with wind gusts peaking around 25-30 mph this afternoon. A band of upper level clouds is migrating northwest across the state. Similar conditions can be expected through the early part of Friday, but as the closed upper low begins to move eastward toward Arizona, we`ll see the chance for showers/thunderstorms to develop across western Arizona Friday afternoon. The low is forecast to gradually move northeastward across the state Friday night through Saturday. The main changes today are a slightly slower movement of the low, which prolongs precipitation chances through Saturday afternoon, and a continued upward trend in precipitation chances. Ensemble membership today is even more supportive of precipitation with fewer members showing zero precipitation. The best rain chances and accumulation potential remain generally along and north of a Prescott to Window Rock line. Precipitation amounts will most likely remain less than 0.25 inches. Given the strength of the low, we can`t rule out an isolated strong or severe storm, but the precipitation looks to mostly lag behind the better shear profiles. Some very light snow is possible over the highest mountain peaks above 10,000-11,000 ft. Saturday will be the coolest day yet this season in response to the trough passage and shower activity. Daytime temperatures will be about 7-10 degrees below normal. Sunday begins a warming trend that will last through next week as the dominant weather feature becomes a strong ridge building over the west. The one exception is a shortwave trough passage near the four corners that could bring some additional wind and chances for showers on Tuesday. Some model guidance this morning indicates a stronger trough passage with additional precipitation potential, so we`ll have to keep an eye on this trend. && .AVIATION...Friday 20/06Z through Saturday 21/06Z...VFR conditions prevail for most areas. Expect variable winds under 10 kts overnight. South- southwest winds increase again after 18Z Friday with speeds 10-20 kts and gusts 20-30 kts. There is a slight chance of a light shower west of a KPRC-KPGA line after 22Z with chances gradually increasing through the evening. OUTLOOK...Saturday 21/06Z through Monday 23/06Z...Cloud cover increases from west to east Friday night through mid day Saturday, with chances for -SHRA and an isolated -TSRA. Greatest chances will be along and west of a KPRC-KFLG-KPGA line. Showers could linger throughout Saturday near the AZ/UT border before ending by sunset. Localized/brief MVFR conditions in precipitation. VFR conditions with SKC return on Sunday. West- northwest winds 10-20 kts on Saturday, then variable winds mostly 10 kts or less for Sunday. && .FIRE WEATHER...Friday and Saturday...Clouds increase throughout the day on Friday as a low pressure system begins to move through from west to east. Seasonal temperatures will remain on Friday with scattered showers and isolated thunderstorms developing later in the day. Precipitation chances persist overnight and into Saturday as temperatures cool. Anticipate southerly winds, 15 to 30 mph, for Friday afternoon, followed by west-northwest winds, 10 to 25 mph, on Saturday. Sunday through Tuesday...A warming and drying trend develops on Sunday and continues on Monday. Afternoon humidity is forecast in the 10 to 20% range on Monday. Humidity increases on Tuesday with a 10 to 15% chance of precipitation. Light west to north winds, under 15 mph, are likely on Sunday and Monday, followed by northerly winds, 10 to 20 mph, on Tuesday. && .FGZ WATCHES/WARNINGS/ADVISORIES...None. && $$ PUBLIC...JJ/MCT AVIATION...JJ FIRE WEATHER...LaGuardia For Northern Arizona weather information visit weather.gov/flagstaff