textproduct: NWS Flagstaff

SYNOPSIS

Scattered afternoon showers and thunderstorms will continue over portions of eastern and central Arizona into Wednesday. On Thursday and Friday, drier conditions are expected with storms confined to mainly the White Mountains. Moisture begins to ramp up again this weekend and into next week. Dangerous heat is expected at the lower elevations of the Grand Canyon through at least Saturday.

DISCUSSION

A ridge centered along the AZ-NM border continues to allow for favorable flow of moisture into our area, and storms are currently ongoing in eastern AZ. Storm intensity is slightly higher than yesterday, but still remains somewhat suppressed with warm air aloft. Gusty outflow winds up to 40 mph and cloud-to- ground lightning are the primary hazards from storms. Localized downpours will also lead to a low, but nonzero chance for flash flooding over sensitive areas (burn scars). Hi-res guidance indicates potential for storms as far west as Flagstaff and the Kaibab Plateau in the late afternoon. Storms will diminish after sunset today. Similar activity can be expected tomorrow, though the ridge begins to flatten and introduce a drier westerly flow aloft.

By Thursday and Friday, the flattened ridge centers to our west. This will push most of the convective activity to our south, though some storms will likely hang around the White Mountains each day. By the weekend, the ridge is forecast to strengthen and rapidly shift to our northeast. Confidence is increasing that we will enter a favorable monsoon pattern by early next week. Stay tuned for further updates on this period!

Heat will also be a concern through the week. The primary concern is the lowest elevations of the Grand Canyon, where temperatures are forecast to exceed 110 degrees each day this week. Similar temperatures will be felt An Extreme Heat Warning is in effect for the Grand Canyon below 4000 ft through Wednesday, becoming an Extreme Heat Watch thereafter through Saturday.

AVIATION...Wednesday 08/06Z through Thursday 09/06Z

Primarily VFR conditions. ISOLD -SHRA east of KPGA-KINW through around 08Z. Another round of ISOLD-SCT SHRA/TSRA after 18Z-20Z Wed, with the highest coverage south of a KPAN-KINW-KRQE line. Winds light and VRB overnight and then SW 10-20 kts again after 18Z Wed. Gusty/erratic wind gusts up to 35 kts possible with shower activity.

OUTLOOK...Thursday 09/06Z through Saturday 11/06Z...Primarily VFR conditions. ISOLD SHRA/TSRA possible SE of a KPAN-KRQE line on Thursday and Friday afternoons. Winds SW-W 10-20 kts each afternoon. Gusty and erratic winds expected near storms.

FIRE WEATHER...Wednesday and Thursday

Most areas will remain hot and dry, with daily southwesterly breezes from 10 to 20 mph, gusting from 25 to 30 mph. Chances for showers and thunderstorms continue over eastern Arizona. Isolated activity developing as far west as a Flagstaff to Payson line on Wednesday, then shifting to Heber eastward on Thursday. Stronger storms will be capable of producing wetting rains.

Friday through Sunday...Hot and mostly dry. Slight chances for afternoon showers and thunderstorms in the White Mountain region on Friday, before activity starts moving back west and north Saturday and Sunday. Expect southwesterly breezes from 10 to 20 mph, gusting from 25 to 30 mph on Friday becoming lighter at 5-15 mph and more variable on Saturday and Sunday.

FGZ WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning until 8 PM MST Saturday for AZZ006.