textproduct: NWS Flagstaff

SYNOPSIS

Look for isolated showers and thunderstorms from the White Mountains and Mogollon Rim southward today and Thursday. Widespread shower and thunderstorm activity could develop by Friday and Friday night with a passing weather disturbance. Temperatures warming to above normal today through Thursday, then cooling off over the weekend.

DISCUSSION...For Today and Thursday

High pressure will gradually build back over Arizona with the high pressure center becoming established over the California/Arizona border by Thursday. Under this pattern monsoon moisture will continue to linger over and south of the Mogollon Rim and White Mountains but further north a drier northwest flow will develop. As a result, look for isolated afternoon and evening showers and thunderstorms along the Mogollon Rim and across the White Mountains region. In addition, a weak moisture surge south of the Mogollon Rim has upped the chances for a stray shower or storm today over the mountain areas of Yavapai and Gila Counties, which could linger into Thursday. Little to no activity is anticipated north of the Mogollon Rim. Look for warmer temperatures as the high builds with mountain highs climbing to the upper 70s to mid 80s and reaching 95 to 105 at lower elevations.

For Friday and the weekend..A trough is expected to dive across the Pacific Northwest pushing the California/Arizona high center eastward. It appears monsoon moisture will interact with the passing Pacific Northwest trough. The models are showing good chances for widespread coverage of showers and thunderstorms Friday and Friday night with diminishing chances from Saturday into Sunday as the trough moves eastward. Vertical wind shear will strengthen some associated with the passing trough. This usually means a few storms will become organized with isolated severe thunderstorms and localized flash flooding possible. Under the influence of the trough it will become breezy with general west to southwest winds at 10-20 mph gusting to 25-30 mph starting Friday and lasting through the weekend.

Looking at early next week...The Pacific Northwest trough moves to the east while an additional trough dives southward just off the west coast of the United States. This will set up a deep south to southwest flow over Arizona between the west coast trough and high pressure over the central Unites States. The question, will deep southerly flow develop with monsoon moisture pushing back across all of Arizona or will a drier and more stable southwesterly flow develop? Looking at the spectrum of model solutions both scenarios are possible. We'll know more a time draws nearer.

AVIATION...Wednesday 09/12Z through Thursday 10/12Z

Primarily VFR conditions. Isolated to scattered SHRA/TSRA mostly along/south of the I-40 corridor between 18Z-03Z, with the best coverage near the White Mountains. Brief drops to MVFR conditions with gusty/erratic winds possible in and around stronger storms. Winds becoming W to NW 5-15 kts between 18Z-02Z. Otherwise, light winds.

OUTLOOK...Thursday 10/12Z through Saturday 12/12Z...Primarily VFR conditions on Thursday, with isolated to scattered SHRA/TSRA along/south of the I-40 corridor. Chances for SHRA/TSRA spreading to most of northern Arizona on Friday afternoon, continuing overnight. Winds W 5-15 kts on Thursday then SW to W 10-20 kts on Friday. Gusty and erratic winds near storms.

FIRE WEATHER...Today and Thursday

Isolated showers and thunderstorms are expected each afternoon along the Mogollon Rim as well as in the areas of the White and Bradshaw Mountains. Winds west to northwest 5-15 mph today, will be followed by west winds 10-20 mph on Thursday. Minimum RH will range from 10-20% percent across northeast Arizona and 20-30% for the remainder of the area.

Friday through Sunday...Monsoon moisture will combine with a passing weak disturbance for scattered shower and thunderstorm activity Friday into early Saturday. There will be the potential for heavy rain and severe hail in spots. Moisture begins to decrease Saturday and Sunday with showers and storms confined to the higher terrain. Winds will be primarily out of the west to southwest at 20-30 mph each afternoon, remaining locally gusty downwind of terrain features at night.

FGZ WATCHES/WARNINGS/ADVISORIES

None.