textproduct: NWS Flagstaff

SYNOPSIS

Dry and mild conditions remain today and much of Friday, before showers set in late Friday into Saturday. A brief return to dry conditions is expected early next week, before unsettled conditions set in by the middle of the week once again. Snow levels look to remain above 8000 feet for the first round of showers, but could drop to around 7000 feet next week.

DISCUSSION...Today

High pressure remains in control on last day across Arizona. Mild temperatures and dry conditions will prevail through the day as a result, along with light winds.

Friday and Saturday...The ridge begins to move eastward as a weakening low ejects off the Pacific into southern California. Breezier and cooler conditions look to set in as a result on Friday. Much of the area looks to remain dry on Friday, however as moisture advection increases, chances for showers and possibly a thunderstorm increase late in the day. The most likely areas look to mainly be along and south of the Mogollon Rim, and any activity that does develop looks to be on the lighter side.

A slightly stronger trough looks to slide southward through the Great Basin on Saturday, adding a little bit more large-scale ascent to aid in precipitation development. This combined with an already primed environment from the previous low should help prompt more scattered to numerous showers and some isolated thunderstorms for the day Saturday. However, given the lack of robust forcing, precipitation amounts still look to be on the light-side, and have continued to trend downward in the last few model runs. Overall, QPF amounts sit around 0.25 inches possibly up to about a half-inch over the higher terrain, with around a few hundredths to a tenth in the lower elevations.

700 mb temperatures start around around 0C, keeping snow levels largely above 9000 feet initially. As colder air moves in aloft, they fall to around -2C which should allow for snow levels to fall to around 8000 feet on Saturday. Some snow mix in down to around 7000 feet at times, however accumulating snow is not anticipated below 8000 feet. Above 8000 feet, 1-3 inches will be possible with the greatest likelihood over the Kaibab Plateau and the San Francisco Peaks where 3-6 inches seem probable.

However, mixing will likely be limited given the increased moisture likely limited the strongest gusts to the downslope areas. Gusts upwards of 30-40 mph will be possible, especially downwind of the Mogollon Rim, with potentially some locally higher gusts possible.

Sunday through Wednesday...High pressure builds back into Arizona on Sunday, brining a brief return of warmer temperatures and dry conditions to at the start of next week.

A stronger trough descends into Arizona on Tuesday. Winds increase again, along with cooler temperatures once again. Overall, QPF amounts look a bit higher with this second storm, however model solutions still remain highly variable so confidence in exact amounts remains low. Temperatures do look a little cooler as well, however the problem will be whether or not the cold air can make it in before the drier air sets in. Regardless, unsettled conditions look to set in late Monday into Tuesday, potentially lingering into the end of the week as well.

AVIATION...Thursday 12/18Z through Friday 13/18Z

VFR conditions expected. Mostly light and variable winds expected through the period. Localized MVFR ceilings possible along the higher terrain after 12Z.

OUTLOOK...Friday 13/18Z through Sunday 15/18Z...Mostly VFR conditions expected, but brief MVFR conditions in -SHRA on Friday afternoon through Saturday afternoon, with a chance for -SHSN mixing in above 7000-8000 feet. Winds are south 10-20 kts on Friday, becoming S-SW 15-25 kts with gusts to 35 kts by 12Z Saturday. Light and variable winds return by 06Z Sunday.

FIRE WEATHER...Friday and Saturday

Slight chances for showers beginning late Friday afternoon through evening. Chances increase and spread to most of northern Arizona on Saturday morning, before mostly dry conditions return by the evening. Rainfall accumulations will generally stay light, under 0.3 inches for most. Light snowfall accumulations will be possible above 8000 feet. Winds are south through southwest 10-20 mph on Friday, increasing to 15-25 mph with gusts to 35 mph on Saturday.

Sunday through Tuesday...A brief period of dry conditions return for Sunday and Monday. Chances for showers increase late Monday evening into Tuesday as another weather system approaches. Winds will be light and variable on Sunday, becoming south at 5-15 mph on Monday, then southwest 15-25 mph with gusts to 40 mph on Tuesday.

FGZ WATCHES/WARNINGS/ADVISORIES

None.