textproduct: NWS Flagstaff

SYNOPSIS

Chances for afternoon showers and thunderstorms will continue over the White Mountain region today and Friday, hot and mostly dry elsewhere. Monsoonal moisture begins to ramp up over this weekend and into next week, with storm activity pushing back west and north and becoming more frequent. Dangerous heat is expected at the lower elevations of the Grand Canyon through Sunday, and for Glen Canyon on Saturday and Sunday.

DISCUSSION

Drier air continues to work it's way into the region as a large flattened ridge is centered to our west. Dewpoints and PW across the region has fallen compared to previous days, especially towards far northern AZ. Scattered thunderstorms are still expected over the White Mountains and Eastern Mogollon Rim today, with some weaker and isolated activity further north. Stronger storms in the White Mountains today could still see small hail, gusty outflow, and flash flood risk over sensitive burn scars. The drying trend continues through tomorrow, with PW bottoming out across the region in the short term. Enough moisture will linger around east and southeast AZ to bring continued convective activity to the White Mountains.

The ridge rapidly strengthens and rebounds eastward this weekend, and sets up in a favorable flow pattern for the North American Monsoon. Moisture begins to creep up slightly on Saturday, but really ramps up by Sunday-Monday. PW values are forecast to climb to 0.9-1.0 inches or greater, around the 80th percentile for Flagstaff climatology. Daily shower and thunderstorms chances look to continue through at least the middle of next week as the flow continues to allow for subtropical moisture to stream into AZ.

Heat will also be a concern through the week with strong ridging in the vicinity. An Extreme Heat Warning remains in effect for the Grand Canyon below 4000 ft through Sunday, with temperatures in excess of 110 degrees expected each day at Phantom Ranch. An Extreme Heat Warning has also been issued for Marble and Glen Canyons on Saturday and Sunday with temperatures close to 10 degrees above normal and HeatRisk in High-Extreme thresholds.

AVIATION...Friday 10/00Z through Saturday 11/00Z

VFR conditions. ISOLD -SHRA/-TSRA before 03Z and after 19Z INVOF KJTC. Winds SW/W 5- 10 kts, increasing to 10-15 kts with gusts 20-25 kts after 18Z. Gusty, erratic winds possible in and around TSRA.

OUTLOOK...Saturday 11/00Z through Monday 13/00Z...Mainly VFR. ISO- SCT SHRA/TSRA INVOF KSOW/KJTC on Saturday, expanding to south of a KGCN-KFLG-KSJN line on Sunday. Brief MVFR conditions and gusty, erratic winds possible in and around TSRA. Winds VRB 5-10 kts on Saturday, becoming S/SW on Sunday.

FIRE WEATHER...Friday and Saturday

Most areas will remain hot and dry. Southwesterly breezes from 10 to 20 mph, gusting from 25 to 30 mph on Friday will become light and variable at 5-15 mph on Saturday. Chances for showers and thunderstorms will continue over the White Mountain region Friday afternoon, with chances nudging further west over the Mogollon Rim on Saturday.

Sunday through Tuesday...Turning a few degrees cooler. Shower and thunderstorm activity pushing west and north across the area with an increase in coverage. Wetting rains are likely. Winds mainly southerly at 5 to 15 mph.

FGZ WATCHES/WARNINGS/ADVISORIES

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

Extreme Heat Warning until 8 PM MST Sunday for AZZ006.