textproduct: NWS Flagstaff

SYNOPSIS

High pressure will continue to dominate the Southwest through the forecast period. This pattern will allow for above normal temperatures and daily chances for showers and storms. Greatest coverage will be across the higher terrain each afternoon and evening.

DISCUSSION

Not much change over the coming week. A strong high pressure system aloft will remain centered over New Mexico and Colorado through Wednesday then slowly shift westward becoming centered over Arizona and Utah by next Saturday. As a result, it will remain hot with low to medium level monsoon activity each day.

For the rest of today and tonight...Monsoon moisture remains in place but on the somewhat low side, consistent with the past few days. Instability is decent across the area but much like the moisture, on the low side. In addition, weak steering flow aloft suggests only a slight chance for storm organization with a preponderance of up and down storms with little movement. As a result, we are expecting heavy downpours with 1.0-2.0 inches of rainfall in isolated spots. Most of us will see much less or even nothing at all. Look for scattered afternoon thunderstorms in the mountain areas such the Mogollon Rim, White Mountains, Chuska Mountains, Black Mesa and the Kaibab plateau. Activity will then spread into the lower elevations, mainly isolated, but lingering into the evening. After midnight any showers/storms will be few an far between. Otherwise, hot with light winds. An Extreme Heat Warning remains in effect until 9:00 PM lower elevations of Yavapai County and through 8:00 PM Sunday for the elevations below 4000 feet from the Grand Canyon to northeastward to Page.

On Sunday...A virtual repeat of Saturday. Hot with light winds and thunderstorms first developing over the mountains late morning then moving into the low elevations from the afternoon into the evening. Shower and thunderstorm threat coming to an end by midnight. Extreme Heat Warning will continue below 4000 feet Grand Canyon to Page.

From Monday onward...Monsoon moisture isn't going anywhere. Look for isolated to scattered showers and thunderstorms each day. The mountains will tend to see the first activity by late in the morning where storms will be scattered. Later in the afternoon thunderstorms will move into the valleys and generally be more isolated. The northeast flow suggests weak and isolated storms north of the Mogollon Rim but south of the rim, as storms roll into deeper moisture, a better chance of local flash flooding and severe storms. Additional Extreme Heat Warnings are likely under strong high pressure.

AVIATION...Sunday 26/06Z through Monday 27/06Z

Mainly VFR conditions. ISO -SHRA overnight, then SCT SHRA/TSRA return after 18Z. Brief MVFR/IFR conditions and gusty, erratic winds in stronger storms. Outside of storms, expect variable winds around 10 kts or less, becoming light and variable overnight.

OUTLOOK...Monday 27/06Z through Wednesday 29/06Z...Mainly VFR conditions. SCT-NMRS SHRA/TSRA between 18Z-03Z each day, with greatest coverage across the higher terrain. Brief MVFR/IFR conditions and gusty, erratic winds in stronger storms. Outside of storms, expect westerly winds 5-15 kts, becoming light and variable overnight.

FIRE WEATHER...Rest of Today through Monday

Isolated to scattered showers/storms each day, primarily across the higher terrain. Localized heavy rain causing flash flooding will remain one of the main concerns. Outside of precipitation, very hot temperatures forecast for lower elevations. Storm driven winds could be gusty/erratic, but variable winds generally 10 mph or less expected otherwise.

Tuesday through Thursday...Above normal afternoon highs will continue through the week, along with daily chances for showers/storms. Main coverage will be across the higher terrain. Gusty/erratic winds possible from storm driven outflows, with light westerly winds forecast otherwise.

FGZ WATCHES/WARNINGS/ADVISORIES

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