textproduct: NWS Flagstaff

SYNOPSIS

Expect temperatures 5-10 degrees above average today and Friday, with temperatures cooling back to near normal over the weekend. Thunderstorm coverage increases today with an active monsoon pattern expected through the weekend.

DISCUSSION

Thunderstorm activity remains pretty active over the southern part of our CWA this morning, but slowly this activity is dissipating and will likely end by sunrise. This may slow the onset of convection a couple hours, but overall its expected to be an active day. High pressure has shifted to the east and is centered over the Four Corners which is a good position to import more moisture into the area today and lasting through the weekend. For today short term models are showing the potential for two waves of thunderstorms. First wave develops along the Mogollon Rim and pushes to the west and southwest during the early to late afternoon out into Yavapai County. The second wave develops over the northeast mountains and mountains of western New Mexico in the mid to late afternoon and pushes to the west through eastern and northeastern Arizona during the evening and early nighttime hours making it as far as central Arizona before dissipating during the early morning hours. With plenty of moisture to work with and some wet soils in parts of the area from yesterday's activity, will definitely have to watch for the potential for some flash flooding. A few storms may become briefly severe with strong winds and quarter sized hail.

Friday's activity will be dependent on how badly Thursday's activity works over the atmosphere. It looks like storm motion may be towards the northwest which often means lower POPs for the middle and lower elevations as storms are not as likely to move off the Rim and that's reflected in the forecast at this time. POPs for the northern half of the state remain elevated as storms may move off the higher terrain into the northern deserts.

Saturday through Monday looks like an active monsoon pattern for the higher terrain with lower POPs for the lower deserts as steering flow remains unfavorable for storms to move off the higher terrain.

Models are split for next week. GFS wants to keep monsoon moisture in while the ECMWF wants to bring in drier air from the west. Right now from Tuesday onward the forecast is for low grade monsoon with only the high terrain seeing a slight chance of storms. Temperatures may also tick back up a few degrees with the drier air in place with highs rising about 5 degrees above average.

AVIATION...Thursday 20/12Z through Friday 21/12Z

Mainly VFR but MVFR likely near thunderstorms. Scattered to numerous thunderstorms begin developing between 18Z-20Z on the higher terrain at first but spreading area wide by late afternoon and not completely dissipating until around 06Z. Winds SW-NW 5-15kts daytime, light and variable or terrain driven overnight. Gusty and erratic winds near thunderstorms.

OUTLOOK...Friday 21/12Z through Sunday 23/12Z...Mainly VFR but MVFR likely near thunderstorms. Scattered to numerous thunderstorms area wide Friday between 18Z-06Z. Scattered to numerous thunderstorms 18Z-03Z Saturday but more confined to higher terrain areas. Daytime winds SW-NW 5-15kts Friday and SW-W 5-15kts Saturday. Light and variable or terrain driven overnight. Gusty and erratic winds near thunderstorms.

FIRE WEATHER...Today and Friday

Expect temperatures to be 5 to 10 degrees above average. Scattered to numerous showers and thunderstorms each day area wide. Nocturnal storms are also possible over the time period. The primary hazards are lightning, gusty and erratic winds, and heavy rain. Winds variable 5-15 mph on today, becoming SW-W 5-15 mph on Friday. Minimum RH's 15-35% each day.

Saturday through Monday...Expect temperatures 0-5 degrees above average through the weekend. Scattered to numerous showers and thunderstorms area wide each day, with nocturnal showers and thunderstorms also possible. Winds SW-W 5-15 mph each day, with gusty and erratic winds possible near storms.

FGZ WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning until 8 PM MST this evening for AZZ006.