textproduct: NWS Flagstaff

SYNOPSIS

Dry weather and seasonable temperatures will continue through Thursday. A series of Pacific storm systems will tap into more tropical moisture beginning Friday, with widespread showers and isolated thunderstorms moving across the state. Shower chances will diminish a bit for Saturday, with a more significant storm system possible for late Saturday night and Sunday. Stay tuned.

DISCUSSION

After a break in precipitation the past few days, another period of unsettled on potentially very wet weather is in store starting early Friday. There is a brief lull in rain and thunderstorms through much of the day Saturday before the next wave of significant rainfall moves in later Saturday night through late Sunday. The first shower and thunderstorms chances begin during the early morning hours on Friday, as tropical moisture heads northward into our region and combines with an approaching upper level wave. A general 0.20"-0.80" rainfall is currently forecast from the Mogollon Rim/White Mtns southward, with some localized heavier amounts over 1" for portions of southern Yavapai County and favored upslope regions along the rim. Some localized flooding could develop, again areas mainly south of the Mogollon Rim would be favored.

Late Friday evening through Saturday afternoon looks to be a lull in precipitation as the first wave moves eastward and the next stronger system begins to approach from the west. By Saturday night through the day on Sunday, very deep moisture is forecast to move across our region from the Pacific. Two upper level features will also impact the region, one wave moving east off the Pacific at a fairly low latitude (starting at 30 degrees north), and the other is a deep upper low moving from the PacNW toward the Great Basin. The majority of guidance produces heavy rainfall across much of our forecast area, with the heaviest from the upslope regions of the Mogollon Rim southward, and somewhat lighter but still significant rain to the north including Navajo Nation. Current projections are for widespread 1-3" rainfall along/south of the Mogollon Rim, with locally higher amounts of 4" in the most favored upslope regions. With soils still wet from previous weeks of rain, this amount of additional rainfall would cause flooding issues. WPC has included all of our forecast area in a Slight Risk for excessive rainfall late Saturday through Sunday, and we will be closely monitoring this potential. Additionally, increased shear, large-scale ascent and colder air aloft raises the risk for severe weather, especially late Saturday night through Sunday.

AVIATION...Thursday 29/00Z through Friday 30/00Z

Mainly VFR conditions. Localized VIS reductions near KFLG and KSEZ due to prescribed burns. Daytime winds S-SW 5-10 kts with gusts 15-20 kts, becoming light and variable or terrain driven overnight.

OUTLOOK...Friday 30/00Z through Sunday 01/00Z...Mainly VFR conditions. After 12Z Friday, ISO-SCT -SHRA with ISO -TSRA with localized MVFR through the period. Daytime S-SW winds 5-10 kts with gusts 15-20 kts, then light and variable or terrain driven overnight.

FIRE WEATHER...Thursday and Friday

A cooling trend is expected to wrap up the week, with daytime highs landing 5-10 degrees below normal by Friday. Dry conditions will last through Thursday, with showers and thunderstorms ramping up early Friday morning. Greatest coverage looks to be along and south of the Mogollon Rim for much of Friday. Gusty/erratic winds possible in/near storms, with south- southwest 5-15 mph expected otherwise.

Saturday through Monday...Cool temperatures will persist, with the coldest temperatures forecast for Sunday. Showers and thunderstorms forecast each day, with Sunday having the greatest risk and greatest coverage for flooding/severe weather. Look for south-southwest winds 5-15 mph Saturday, increasing to 10-25 mph on Sunday, and shifting out of the northeast on Monday.

FGZ WATCHES/WARNINGS/ADVISORIES

None.