Area Forecast Discussion
Issued by NWS Flagstaff, AZ
Issued by NWS Flagstaff, AZ
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682 FXUS65 KFGZ 151611 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 911 AM MST Sun Sep 15 2024 .SYNOPSIS...A few showers will be possible in eastern Arizona this morning with mainly dry weather elsewhere. Cooler weather with chances for showers and thunderstorms will move in later today and continue through Monday, with the best chance of rain over the eastern half of the state. Look for breezy weather today with windy conditions on Monday. Dry but cool and breezy weather then returns on Tuesday and for much of next week. && .UPDATE...Scattered showers and thunderstorms developed early this morning between 400 and 730 AM over portions of Apache County, including Eagar-Springerville, St Johns, and Window Rock as increased moisture interacted with a passing shortwave. This activity has moved into New Mexico, with dry weather as of 9 AM area wide. For the rest of today, isolated to scattered showers and thunderstorms are expected to redevelop mainly east of a Payson-Kayenta line with daytime heating. Later tonight, as the main low pressure system approaches, low level winds are forecast to back and pull some additional moisture north and west. Instability should increase, and scattered showers and thunderstorms are forecast by most CAMs to develop and move up into Gila, southeast Coconino, and Navajo/Apache counties through the overnight hours. With 0-6km wind shear in the 35-40 kt range, a few strong to possibly severe storms could develop, along with some training cells producing localized heavy rainfall. PoPs were increased in these areas for the overnight hours in an update this morning. The other thing we are watching for Monday as the low approaches is strong gusty southwest winds (unrelated to storms). With gusts in the 35-45 mph range forecast by the latest guidance, we may be issuing a Wind Advisory from around Winslow/Flagstaff northwestward for Monday afternoon. && .PREV DISCUSSION /623 AM MST/...A trough continues to approach Arizona from over the Pacific Ocean with some moisture streaming northward in advance of the trough. The moisture from the south is still coming but not quite as much as we were previously forecasting. We`ll need to dial back our expectations with most decent rainfall amounts confined to the area along and south of a line extending from Payson to Window Rock. The highest precipitation amounts of 0.50 to 1.00 inches look to be located along the eastern Mogollon Rim and White Mountains region southward. Today...Mainly isolated and brief showers across most of northern Arizona. The highest moisture values and best chances for showers will be from Payson to Window Rock southward, especially with daytime heating. But even then only a 30 to 40 percent chance of showers and thunderstorms for a given location. Otherwise, look for cooler temperatures under the influence of the approaching trough. In addition, pressure gradients will be strengthening with afternoon southwest winds at 10 to 20 mph gusting to 30 mph across much of the area. Tonight and Monday...Increasing moisture from the south and residual boundary layer instability from the previous days heating will interact with passing large-scale upward motion associated with the approaching trough. As a result, we will see the best chance for showers and thunderstorms later tonight into Monday, especially over eastern portions of Arizona. There will remain the limited threat of a stray severe thunderstorm and localized flooding. As the trough axis draws nearer anticipate additional cooling. Pressure gradients strengthen further on Monday with southwest winds at 15 to 25 mph gusting to 30 to 40 mph developing, with the stronger gusts located from the Mogollon Rim northward. For Tuesday and much of next week...Some moisture will linger over the White Mountains region for a slight chance of showers and thunderstorms on Tuesday. Otherwise, mainly dry and seasonably cool temperatures are forecast. The potential for below freezing temperatures at elevations above 6500 feet will enter the picture starting Wednesday with the drier air mass. It will remain breezy to windy as an additional mainly dry trough heads our way toward the end of next week. There could be a few showers across northwest Arizona and along the Utah border later next week but at this time don`t appear to amount to more than a few hundredths of an inch. && .AVIATION...Sunday 15/12Z through Monday 16/12Z...Mainly VFR conditions persist through the period with FEW-SCT cloud cover near 11,000 feet MSL. Cloud cover increases east of a KPAN-KOV7 with isolated to scattered -SHRA/-TSRA. Variable winds of 5 kts will become southwest winds, 15-25 kts, from 17Z-02Z. OUTLOOK...Monday 16/12Z through Wednesday 18/12Z...ISLD-SCT -SHRA/TSRA through Monday with greatest chances across eastern Arizona. Winds increase again Monday with gusts 25-35tks. Widespread VFR conditions are expected Monday night and Tuesday with mostly clear skies. Southwest winds will remain elevated on Tuesday, 20-30kts. && .FIRE WEATHER...Today through Monday...Moisture increases from the south resulting in isolated to scattered showers and thunderstorms into Monday. Greatest coverage will be across east-central Arizona. Cooler temperatures are expected, becoming 5 to 10 degrees below average on Monday. Breezy southwest winds, 15 to 25 mph, today will increase to 30 to 40 mph on Monday. Tuesday through Thursday...Cooler, breezy, and mainly dry. Another low pressure system could bring a few showers to northwest Arizona Thursday. Southwest winds 15 to 25 mph each day. && .FGZ WATCHES/WARNINGS/ADVISORIES...None. && $$ PUBLIC...JJ/McCollum AVIATION...MAS FIRE WEATHER...JJ For Northern Arizona weather information visit weather.gov/flagstaff