textproduct: NWS Flagstaff

SYNOPSIS

Isolated to scattered showers and thunderstorms will continue into the evening hours with flash flooding possible through mid-evening across portions of northwestern Arizona. Gradually warmer temperatures and more isolated coverage of storms is expected through the weekend into next week.

DISCUSSION

A trough was centered just off the California coast with high pressure centered over the southern United States Friday afternoon. The southerly flow between these two pressure systems continued to pull monsoon moisture northward. Northwest Arizona was seeing the most activity resulting from being closer to cooler mid-level temperatures and weak upward motion. The main observation through the early afternoon was generally fast moving storm cells locally training in spots across northwest Arizona. In addition, vertical shear associated with the trough resulted in a few organized and severe thunderstorms in the area of Chino Valley. A Flash Flood Watch remains in effect for portions of northwest Arizona until 8 PM MST.

For tonight...The current pattern remains in place. Storms will be most numerous across northwest portions of Arizona and generally isolated elsewhere. Isolated activity will then continue here and there through the night. The threat for flash flooding will remain through mid-evening across northwest portions of Arizona. Heavy downpours and briefly severe behavior could be observed with any storm this evening, most likely across the northwest, enhanced by cooler temperatures and wind shear aloft.

From Saturday into Tuesday...The high pressure center gradually builds from over the southern United States to over Arizona. Monsoon moisture will remain at the lower limits for activity for most of the area as well as warmer temperatures aloft adding a stabilizing aspect to the atmosphere. The best chance for showers and storms area wide will be on Saturday as cooler air aloft, vertical shear and even weak upward motion associated with the California trough remains in place. Beyond Saturday as the high builds, warming temperatures aloft take over for much of northern Arizona for generally an isolated threat. The exception, moisture values will remain just high enough over the high terrain of far eastern Arizona for scattered afternoon showers and thunderstorms, primarily the White Mountains region.

Looking further out...It appears active monsoon weather will return as the high pressure center finds it's way to the Four Corners region, opening the door to increasing monsoon moisture.

AVIATION...Saturday 15/00Z through Sunday 16/00Z

VFR with MVFR possible near heavier showers/storms. Showers and storms should be ending between 03-06Z. Tomorrow's shower/storm coverage will be more limited to the higher terrain (i.e. Rim, White Mountains, Kaibab Plateau and Bradshaws) with storms beginning around 18-22Z. Winds light and variable or terrain driven overnight, variable 5-15kts daytime Saturday. Gusty and erratic winds near storms.

OUTLOOK...Sunday 16/00Z through Tuesday 18/00Z...VFR conditions, MVFR possible near heavier storms. Chance of isolated showers/storms over higher terrain between 18Z-03Z each afternoon. Winds SW-W 5-15kts daytime, light and variable or terrain driven overnight. Gusty and erratic winds near storms.

FIRE WEATHER...Today through Sunday

Numerous showers and thunderstorms across northwest Arizona today, generally scattered for the remainder of the area. Coverage on Saturday and Sunday becoming isolated to scattered from the Mogollon Rim and northward. Outside of storms, winds generally southwest/west 5-10 mph.

Monday through Wednesday...Gradually turning warmer. Isolated to scattered showers and thunderstorms each day, best coverage over the White Mountains. Winds are gusty and erratic near storms, otherwise generally south through west 5-10 mph each day.

FGZ WATCHES/WARNINGS/ADVISORIES

Flood Watch until 8 PM MST /9 PM MDT/ this evening for AZZ004>006.