textproduct: NWS Flagstaff

SYNOPSIS

Hot temperatures continue through the early part of the week. Monsoon moisture returns to the area through the coming week, bringing better storm chances especially for areas along and south of the Mogollon Rim. With the added moisture, temperatures begin to trend downward Monday towards seasonal averages for most areas.

DISCUSSION

Very strong high pressure was centered just north of the four corners on Saturday, bringing the hottest temperatures of the year so far to many locations including Flagstaff (92), Winslow & Page (104), and Prescott (98). This ridge will expand northeastward to cover much of the country for most of the coming week. Though it will become centered over the northern plains and Midwest, it is forecast to be so strong (500mb height 600 dam) that even on the fringes of the high in Arizona, areas that don't receive much rainfall and cloud cover will continue to be hot for much of the week. This would mostly be areas north of the Mogollon Rim where precipitation and cloud coverage will be lower, at least through mid week. With the position of the ridge today and Monday, mid level flow will be east-southeasterly and favorable for moisture transport up into central Arizona and the Mogollon Rim. A storm complex that moved westward through southern AZ Saturday evening has helped push some added low level moisture northward, the dewpoints mostly in the 50s in Yavapai/Gila counties and mid-upper 40s along the rim. Model guidance continues to show storms firing along the higher terrain of the Mogollon Rim/White Mtns around mid day to 2 PM, then moving west- northwestward through Gila/Yavapai during the mid afternoon to early evening. As these storms move into the higher instability and hot/deep boundary layer, gusty outflow winds will be a threat with widespread 30-50 mph gusts and an isolated severe gust to 60 mph. The Storm Prediction Center continues with a marginal risk of severe weather in Yavapai/Gila counties this afternoon/evening mainly for strong wind gusts, though some localized 1/2 to 1 inch hail can't be ruled out. Monday's setup is quite similar, so we could see a repeat of this storm evolution with the same areas targeted. Tuesday, the flow aloft turns a bit more northeasterly as low level moisture expands to cover areas farther north. This may allow for more storms over the higher terrain of northeast Arizona, possibly giving areas along the Mogollon Rim a second round of storms moving in from the northeast in the evening.

From Wednesday into next weekend, most of the guidance keeps the ridge centered to our north/northeast which is a favorable pattern for monsoon moisture to remain over Arizona. The mean precipitable water from the grand ensemble is around 1.00" over the Mogollon Rim and near 1.50" over lower elevations of Yavapai County. These values are in the 80-95th percentile for this time of year, so daily rounds of showers and thunderstorms are expected to continue along with the typical hazards of the monsoon - dangerous lightning, localized flash flooding, and a few strong/severe thunderstorms.

AVIATION...Sunday 12/18Z through Monday 13/18Z

VFR with MVFR possible near heaviest storms. Scattered showers/storms expected between 18Z-04Z today, mainly south and west of a KGCN-KFLG-KJTC line. Winds SW- SE 5-15kts daytime, light and variable or terrain driven overnight. Gusty and erratic winds up to 30-40kts possible in vicinity of storms.

OUTLOOK...Monday 13/18Z through Wednesday 15/18Z...VFR with MVFR possible near heaviest storms. Scattered showers/storms each afternoon mainly between 18Z-04Z throughout most of the area. Winds SW-SE 5-15kts daytime, light and variable or terrain driven overnight. Gusty and erratic winds up to 30-40kts possible in vicinity of storms.

FIRE WEATHER...Today and Monday

Remaining hot. Increasing chances for showers and thunderstorms, with the highest chances along and south of the Mogollon Rim and White Mountains. Strong storms with widespread gusty outflow winds will be possible each afternoon and evening, mainly across Yavapai and Gila counties. Outside of storms, winds 5-15 mph south through west today shifting to south through southeast on Monday.

Tuesday through Thursday...Shower and thunderstorm activity increasing across the region, best chances from the Mogollon Rim and White Mountains southward where wetting rains are likely. Otherwise, near normal daytime temperatures with winds mainly southwest 5-15 mph outside of storms.

FGZ WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning until 8 PM MST /9 PM MDT/ this evening for AZZ005-006.