textproduct: NWS Flagstaff

SYNOPSIS

Warm temperatures continue with isolated to scattered showers and thunderstorms today. Cooler temperatures and more widespread showers and thunderstorms are expected through this week.

DISCUSSION

High pressure will remain the main feature of the forecast as it weakens and pushes to the north over the weekend. By early next week, the high will slide over the Four Corners region.

For today, expect similar conditions to the past several days with isolated to scattered showers and thunderstorms. Storms initiate across the higher terrain by early afternoon, moving off towards the south and west through this evening. Isolated activity remains possible across northeastern Arizona. Similar to Saturday, there is enough instability and shear to support a few strong to severe storms. However, heavy rain with the potential for flash flooding will remain the main hazard of concern. One kink the plan for today is just how much debris cover hangs around through the morning. It may delay storm initiation and limit coverage through this afternoon.

The heat is slow to abate across northern Arizona with temperatures in Phantom Ranch continuing to reach 115 on Saturday. With moisture expected to increase over the next few days, we will see more storms and cloud cover, which should finally break the heat wave. For now, we have issued an Extreme Heat Warning for the Grand Canyon and Glen/Marble Canyons through 8 PM this evening. There is some uncertainty to just how hot Monday will be and right now it looks marginal. However, the warning may need to be extended into Monday if trends continue to remain high.

Heading into the rest of this week, we will see the high shift over the Four Corners region and good moisture advection into the state. Daily chances for scattered to widespread showers and thunderstorms are expected with slightly cooler temperatures each day. Heavy rain leading to flash flooding will become the main hazard of concern as we go through the week.

AVIATION...Sunday 09/12Z through Monday 10/12Z

Expect mainly VFR conditions outside of thunderstorms. ISO-SCT SHRA/TSRA between 19Z-03Z, mainly along and west of a KGCN-KFLG-KSJN line. Some storms will produce brief MVFR/IFR and wind gusts to 40 kts. Outside of storms, expect SW-NW winds 5-15 kts.

OUTLOOK...Monday 10/12Z through Wednesday 12/12Z...Expect mainly VFR conditions outside of thunderstorms. SCT-NMRS SHRA/TSRA between 18Z-03Z each day. Some storms will produce brief MVFR/IFR and wind gusts to 40 kts. Outside of storms, expect SW-NW winds 5-15 kts.

FIRE WEATHER...Today through Monday

Above normal temperatures continue with slightly cooler temperatures on Monday. Expect isolated to scattered showers and thunderstorms today, with increasing coverage on Monday. Greatest coverage across higher terrain and areas to the south and west each afternoon/evening. Stronger storms may contain heavy rain, small hail, frequent lightning, and gusty/erratic winds. Outside of storms, expect variable winds around 5-15 mph. Minimum RH values 10-20% across NE Arizona, 20-40% elsewhere.

Tuesday through Thursday...Near to slightly below normal temperatures with scattered to widespread showers and thunderstorms each day. Outside of storms, expect variable winds around 5-15 mph. Minimum RH values 20-40% across NE Arizona, 30-60% elsewhere.

FGZ WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning from 9 AM MST /10 AM MDT/ this morning to 8 PM MST /9 PM MDT/ this evening for AZZ005-006.