textproduct: NWS Flagstaff

SYNOPSIS

Storm activity will be confined to eastern Arizona today before gradually spreading back westward through the week. Widespread shower and thunderstorm activity could develop by Friday and Saturday with a passing weather disturbance. Temperatures warming to above normal today through Thursday, then cooling off over the weekend.

DISCUSSION

High pressure aloft was centered over Oklahoma early morning Tuesday with a strong trough centered over the Pacific Northwest.

From Today into Thursday...High pressure will gradually build back over Arizona in response to the Pacific Northwest trough moving into the central United States. Monsoon moisture will continue to linger and even gradually increase through this period. As a result, the afternoon/evening shower and thunderstorm threat will continue across the high terrain of eastern Arizona but also gradually spread westward along the Mogollon Rim. Any heavy rain potential is expected to remain confined to the White Mountains region. Look for warmer temperatures as the high builds with mountain temperatures climbing to the upper 70s to mid 80s reaching 95 to 105 at lower elevations.

For Friday and beyond...An additional trough is expected to drive across the Pacific Northwest pushing the high center to the east of Arizona. It appears monsoon moisture will remain in play and interact with the passing Pacific Northwest trough. The models are showing good chances for widespread coverage of showers and thunderstorms Friday through Saturday with some level of activity continuing through the overnight hours. The passing trough will result in increased vertical wind shear with a few storms possibly becoming organized, thus raising the threat of severe thunderstorms and localized flash flooding. The trough heads eastward on Sunday with a drier and more stable air mass moving across most of northern Arizona. Under the influence of the trough it will be come breezy with general west to southwest winds at 10-20 mph gusting to 25 mph starting Friday and lasting through the weekend.

AVIATION...Tuesday 08/12Z through Wednesday 09/12Z

Primarily VFR conditions. Brief MVFR conditions possible in isolated to scattered SHRA/TSRA between 19Z-03Z, mainly south of the I-40 corridor. Winds W to NW 5-15 kts between 18Z-03Z. Otherwise, winds light and variable.

OUTLOOK...Wednesday 09/12Z through Friday 11/12Z...Mainly VFR conditions, brief MVFR conditions possible with thunderstorms. Scattered SHRA/TSRA over the Mogollon Rim and White Mountains on Wednesday, isolated elsewhere. Storm coverage increases and spreads westward on Thursday and Friday. Winds variable 5-10 kts on Wednesday, turning W to NW 5-15 kts on Thursday, then increasing and becoming SW to W at 10-20 kts gusting to 20 kts Friday.

FIRE WEATHER...Today and Wednesday

Expect low grade monsoon activity with afternoon shower and thunderstorm chances confined to the Mogollon Rim and the mountains of eastern Arizona. Winds south to southwest 5-15 mph with gusts to around 20 mph each afternoon, then light and variable or terrain driven overnight. Turning warmer with minimum RH ranging from 15% across the lower elevations of northeast Arizona to 30-40% in the mountains.

Thursday through Saturday...Low to medium grade monsoon activity developing. On thursday, shower and thunderstorm chances remain confined to the Rim and White Mountains. By Friday and Saturday, with a passing weather, disturbance wider coverage of showers and storms is anticipated. Daytime winds south to southwest 5-15 mph on Thursday then strengthening to 10-20 mph gusting to 25-30 mph on Friday and Saturday. Winds remaining locally gusty at night.

FGZ WATCHES/WARNINGS/ADVISORIES

None.