textproduct: NWS Flagstaff

SYNOPSIS

A series of storm systems will bring rain and snow along with gusty winds to northern Arizona through much of the coming week. Winter driving conditions are likely above 6000 feet later tonight through Tuesday, then down to 5000 feet or lower by Wednesday.

DISCUSSION

A large area of low pressure will be located over the western United States through Friday. A series of shortwave troughs will cross our region on the south end of this low, delivering colder temperatures, windy conditions and periods of mountain snow and lower elevation rain. Driving will become difficult and hazardous at times through the coming week due strong crosswinds and snow accumulation on roads. Make sure and check for forecast updates and plan your travels accordingly.

The first wave will cross our region later this evening through Tuesday. Precipitation is forecast to develop by early evening in western Coconino/Yavapai counties, spreading to the I-17/US89 corridor by mid to late evening (8-10 PM), then into eastern Arizona in the pre-dawn hours. Snow levels will be fairly high initially (7000-7500') but will fall quickly to 5000-5500' as the front passes. Southwest winds will also remain elevated overnight into Tuesday, strongest just ahead and along the cold front. The Winter Weather Advisory continues from this evening through Tuesday afternoon for the Kaibab Plateau and Mogollon Rim, including the Flagstaff region and adjacent stretches of I-40/17. A general 3-7" snowfall is forecast through early Tuesday evening above 6000' in the advisory area. Due to strong upslope forcing, some locally higher amounts of 8-12" may occur on south-facing slopes. The steadiest precipitation and heaviest accumulation is expected through Tuesday morning, with a more showery nature into the afternoon. From Tuesday evening through the overnight period, a chance of snow showers will persist over the upslope zones of the Mogollon Rim/Kaibab Plateau and continue to create periodic snowy travel, with most other areas seeing showers taper off. The second shortwave is forecast to move through our region from early Wednesday morning through early evening. This shortwave is expected to be colder, with lower snow levels down to 4000-5000'. The latest NBM guidance has a 50-70% chance of 24-hr snowfall exceeding 8" along the higher portions of the Kaibab Plateau and Mogollon Rim on Wednesday. Winds aloft on Wednesday also increase to 50-65kts at 700 mb, with surface winds gusting in the 35-45 mph range for most areas and even higher (55+ mph) in the Little Colorado River Valley and spots like Eagar, Springerville, and possibly Show Low. The combination of snow/blowing snow with the gusty winds prompted us to issue a Winter Storm Watch from early Wednesday morning through mid evening for the Kaibab Plateau to the Mogollon Rim where the heaviest snow is forecast. Other areas may need Winter Weather Advisories eventually (Grand Canyon, higher elevations of Yavapai County, Chuska Mtns). A third shortwave is still forecast to arrive later Thursday into Friday, but this continues to be a lower confidence forecast as there is more model spread in this time period. For now, we have a 40-60% chance of precipitation with low snow levels down to 4000'. This last system has the potential to be pretty impactful with another round of moderate to heavy snow, but we just don't have details just yet - stay tuned on this one. Overall, quite the pattern shift to active winter weather after a rather quiet season so far.

AVIATION...Tuesday 17/06Z through Wednesday 18/06Z

MVFR/IFR conditions in SHRA/SHSN spreading from west to east. Worst impacts expected between 06Z-12Z, with IFR-LIFR in +SN/+RA and BLSN for high elevation sites. Slight improvement after 12Z-15Z. S-SW winds 20-30 kts gusting 35-45 kts through the period.

OUTLOOK...Wednesday 18/06Z through Friday 20/06Z...Mainly MVFR/IFR with periods of VFR through outlook period. Worst impacts expected between 12Z/Wed-00Z/Thu, with IFR-LIFR in +SN/+RA and BLSN. S-SW winds 15-30 kts with gusts 35-40 kts on Wednesday, becoming SW-W 10-20 kts with gusts 20-30 kts on Thursday.

FIRE WEATHER...Tonight through Wednesday

Rain and snow showers begin spreading from west to east tonight. Heaviest and most widespread rain/snow accumulations are anticipated through Tuesday morning, then again Wednesday morning through evening. Conditions will remain scattered and showery even outside of these periods. Snow levels start around 7000-7500 feet by the onset of precipitation, falling to 5000-5500 feet by midday Tuesday, then 4000-4500 feet by Wednesday evening. Winds are southwest 15-30 mph with gusts 35-45 mph through the period, remaining elevated overnight.

Thursday through Saturday...Chances for rain and snow showers continue Thursday and Friday, however confidence is lower on additional accumulations during this period. Snow levels may drop as low as 3500-4000 feet on Friday. Fair weather looks to return by Saturday. Winds are southwest through west 10-15 mph gusting to 25 mph Thursday and Friday, then variable at 5-15 mph on Saturday..

FGZ WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until 5 PM MST Tuesday for AZZ004- 015>017.

Winter Storm Watch from late Tuesday night through Wednesday evening for AZZ004-015-016.

Wind Advisory until 8 AM MST Tuesday for AZZ006>008-038.

Wind Advisory until 5 PM MST Tuesday for AZZ012>014-039.