textproduct: NWS Flagstaff

SYNOPSIS

A passing weather system will bring increasing showers through the day today, with more widespread precipitation tonight through Saturday. Expect accumulating snow mostly in the mountains, with light snow amounts possible down to around the 5000 foot elevation level by Saturday evening behind a cold front. Expect much colder temperatures this weekend lasting into early next week. Drier weather returns Sunday through much of next week.

DISCUSSION

A briefly more active weather pattern is developing this morning as Arizona will be impacted by a pair of approaching weather systems. Early this morning, a cut-off low pressure system was spinning off the southern California coastline, while a cold northern stream trough was progressing into the Great Basin. Already this morning, the deserts of southern AZ have seen some rainfall thanks to the moisture advection ahead of the closed low. We expect showers to increase and spread into northern AZ through the day today. The more persistent activity will be generally from Flagstaff south and east into the White Mountains. The mild airmass today will keep snow levels mainly near and above 7000 feet today.

The aforementioned cut-off low is forecast to track well south of AZ, while the northern stream trough becomes the dominant feature bringing precipitation and colder temperatures through the weekend. The advancing trough from the north will lead to increasing coverage and intensity of showers Friday night into Saturday. The advancing cold air will lower snow levels to 5500 - 6500 feet through Saturday afternoon. The coldest air arrives along a cold front passage that will move south through the area Saturday afternoon and evening dropping snow levels briefly to around 5000 feet. Precipitation forecasts have trended slightly upward, especially across eastern Arizona which has prompted the issuance of a Winter Weather Advisory for the Chuska Mountains. Additionally, hi-res models are suggesting potential for a more intense band of snowfall to set up along the cold front Saturday afternoon so this will be something to keep an eye on. Precipitation chances quickly diminish behind the cold front passage Saturday night. Although snowfall amounts are not particularly high with this system, it has the potential to bring widespread light snowfall to valley floors across northeastern Arizona.

In addition to the winter weather impacts, much colder weather is in store through the weekend with the coldest nights yet this season expected Saturday and Sunday nights. Overnight temperatures will drop into the teens to even single digits for much of the high country. Bundle up and be prepared for cold mornings, especially at the start of next week.

A much quieter pattern develops next week with high pressure returning to the region. Expect dry weather with gradually warming temperatures through the week.

AVIATION...Friday 23/12Z through Saturday 24/12Z

Mostly VFR conditions forecast through 18Z, but a few light sprinkles/virga may be noted south of I-40 until then. Afterwards, expect SHRA/SHSN to develop causing MVFR conditions generally south and east of a KPRC- KRQE line before expanding more west and north throughout the TAF period. Look for S-SW winds 10-20 kts with gusts up to 25 kts possible.

OUTLOOK...Saturday 24/12Z through Monday 26/12Z...MVFR/local IFR conditions expected through at least 00Z Sunday due to SHRA/SHSN, with improving conditions west to east forecast afterwards. By 12Z Sunday, majority of the precipitation should be gone from our CWA. Look for west through north winds 5-15 kts Saturday, becoming generally less than 10 kts out of the north on Sunday.

FIRE WEATHER...Friday and Saturday

Normal to above normal temperatures will stick around today, before a quick cooling trend begins on Saturday. A storm system not only will bring chilly daytime highs, but increased chances for rain/high elevation snow beginning this afternoon across the White Mountains and spreading north and west through Saturday. Look for southwest winds 10-20 mph today, becoming west through north 5-15 mph on Saturday.

Sunday through Tuesday...A few lingering showers possible early Sunday across far E. AZ, but otherwise dry conditions will prevail. Daytime highs also look to warm each afternoon, but morning lows forecast below freezing for the majority of northern/central AZ. Expect north-northwest winds 5-15 mph on Sunday, becoming more variable for Monday and Tuesday.

FGZ WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory from 5 PM this afternoon to 11 PM MST Saturday for AZZ011.

Winter Weather Advisory from 5 PM this afternoon to 5 AM MST Sunday for AZZ017.