textproduct: NWS Flagstaff

SYNOPSIS

Hot temperatures will remain this weekend. Only isolated storms are expected today along the Mogollon Rim and White Mountains. On Sunday, monsoon moisture begins to return to the area bringing better storm chances and more extensive coverage of storms across the state through next week.

DISCUSSION

Strong high pressure that was centered over central/southern Arizona on Friday will shift to near the four corners later today and then be parked over the northern Rockies/Plains Sunday through mid week. For today, this will result in the hottest temperatures of the summer so far for much of northern Arizona. An Extreme Heat Warning remains in effect through Sunday evening for the lower elevations of the Grand Canyon and also the Marble/Glen Canyon/Page areas. Moisture is lacking north of the Mogollon Rim where dewpoints will be in the 20s today. Along and south of the rim, some limited moisture remains which will allow for some isolated high-based afternoon and evening showers or thunderstorms with gusty outflow winds. By Sunday, big changes are expected as the high continues its northward shift, allowing for a more southeasterly flow aloft and a surge of moisture northward into our region. Much of the model guidance indicates scattered thunderstorms developing along the Mogollon Rim/White Mtns by early afternoon, pushing toward the west/northwest through Gila and Yavapai counties during the mid to late afternoon. These storms will move into a deeply mixed boundary layer and bring a threat of gusty outflow winds of 30-50 mph, with some isolated severe gusts up to 60 mph. Instability south of the rim will also bring an isolated threat of 1/2 to 1 inch diameter hail. Storm motion of 15-20 mph will limit the coverage of heavier rainfall, though a marginal flash flood threat exists from the Mogollon Rim/White Mtns south into Yavapai/Gila. A similar setup looks to remain in place Monday, with better storm chances spreading a bit farther north by Tuesday.

From Wednesday through Friday, the upper air pattern becomes less certain but most of the guidance keeps the ridge centered to our northeast which is a favorable pattern for monsoon moisture to remain over Arizona. The mean precipitable water from the grand ensemble is around 1.00" over the Mogollon Rim and near 1.50" over lower elevations of Yavapai County. These values are in the 80-95th percentile for this time of year, so daily rounds of showers and thunderstorms are expected to continue along with the typical hazards of the monsoon - dangerous lightning, localized flash flooding, and a few strong/severe thunderstorms. Daytime temperatures should decrease to near normal next week for most areas due to the moisture return. Areas along the UT/AZ line will remain around 5 degrees above normal through mid week as the moisture is slower to reach that area.

AVIATION...Saturday 11/12Z through Sunday 12/12Z

VFR conditions. ISO -SHRA/TSRA 18Z to 04Z, mainly along and south of a KFLG-KSJN line. Gusty outflow winds possible in and around TS. Winds VRB 5-15 kts.

OUTLOOK...Sunday 12/12Z through Tuesday 14/12Z...Mainly VFR. SCT SHRA/TSRA expected each day, primarily near and south of a KGCN-KINW- KSJN line. Brief MVFR conditions and gusty outflow winds possible in and around TS. Winds SW-SE 5-15 kts each day, becoming VRB overnight.

FIRE WEATHER...Today and Sunday

Remaining hot. Slight chance of showers and thunderstorms primarily over the Mogollon Rim and White Mountains area today, increasing and spreading further west and north on Sunday. Strong storms with gusty winds will be possible Sunday afternoon and evening, mainly in Yavapai and Gila counties. Outside of storms, winds will be mainly south through west around 5-15 mph.

Monday through Wednesday...Shower and thunderstorm activity increasing across the region, best chances from the Mogollon Rim and White Mountains southward where wetting rains are likely. Otherwise, turning a bit cooler with winds mainly southwest 5-15 mph.

FGZ WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning from 11 AM MST /noon MDT/ this morning to 8 PM MST /9 PM MDT/ Sunday for AZZ005.

Extreme Heat Warning until 8 PM MST Sunday for AZZ006.