textproduct: NWS Flagstaff

SYNOPSIS

Showers and thunderstorms are starting to develop over the higher terrain due to clear skies and daytime heating. A complex of thunderstorms is also moving through far northwest Arizona and into Utah, and outflow from this complex may trigger more showers and thunderstorms in northwest Arizona this afternoon. Thursday and through the weekend, shower and thunderstorm coverage will be isolated and mainly contained to the higher terrain as daytime high temperatures soar, likely reaching the warmest readings so far this year.

DISCUSSION

The weak MCV is continuing to move north-northeastward and showers and thunderstorms are pushing into Utah. Mostly clear skies are leading to showers and thunderstorms to develop along the higher terrain of the Rim, and we should start to see showers and thunderstorms over the White Mountains over the next couple of hours as well. Decent southerly flow is expected to push developing showers and thunderstorms northward, which may limit the threat for flash flooding from individual storms, but any back-building storms, caused by outflow from thunderstorms pushing southward will create localized areas of higher risk for flash flooding through the afternoon and early evening hours. Shower and thunderstorm activity should settle down tonight.

For Thursday and into the weekend, the high over New Mexico is expected to move westward and strengthen, This slowly introduces drier, mid-level air and subsidence, causing the Monsoon activity will slow down. We don't expect a total stop, but it will be slow through the weekend. The high may return to a more favorable location by next week, with easterly steering flow returning, but this outlook could change in a week and will be monitored. The relocation and strengthening of the high, with the slow down of the Monsoon, will cause temperatures to soar. This will cause many locations to reach the warmest temperatures so far this year. Extreme heat warnings remain in effect for the Grand Canyon, Yavapai and northern Gila Counties below 4000 ft, as well for Marble and Glen Canyon, including the city of Page, and Oak Creek and Sycamore Canyons, including the city of Sedona.

AVIATION...Thursday 30/00Z through Friday 31/00Z

Mainly VFR conditions, MVFR possible near heavier showers/storms. Scattered showers/storms mainly north of I-40 through 03Z. Winds SW 5-15kts daytime, light and variable or terrain driven overnight. Gusty erratic winds up to 40kts possible near storms.

OUTLOOK...Friday 31/00Z through Sunday 02/00Z...Mainly VFR conditions. Isolated showers/storms each afternoon with best chances near the White Mountains. Winds SW 5-15kts daytime, light and variable or terrain driven overnight. Gusty erratic winds up to 40kts possible near storms.

FIRE WEATHER...Thursday and Friday

A downturn in precipitation chances begins on Thursday with best chances being over the Rim and the White Mountains. Temperatures warm to 5-10 degrees above average. Winds SW 5-15 mph. Minimum RH values 15-30% Thursday, 10- 25% Friday.

Saturday through Monday...Hot with temperatures 10-15 degrees above average. Only precipitation chances are mainly confined to the White Mountains this weekend, with a slight uptick in monsoon activity over the higher terrain starting Monday. Winds will be generally light and variable at 5 to 15 mph. Minimum RH values 7-20% Saturday, 8-25% Sunday, 10-30% Monday.

FGZ WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning from 10 AM MST /11 AM MDT/ Friday to 8 PM MST /9 PM MDT/ Sunday for AZZ005-018-037-038.

Extreme Heat Warning from 10 AM Thursday to 8 PM MST Sunday for AZZ006.