textproduct: NWS Flagstaff

SYNOPSIS

Winter weather will continue across much of northern Arizona today, with dry but cold conditions following for Friday and the weekend. Dry weather and a warming trend are expected next week.

DISCUSSION

The first of two weather system to impact our region has moved eastward into New Mexico this morning. As the next stronger system (currently over central California) dives southeastward, moist westerly flow has increased over northern Arizona leading to a continuation of mainly upslope rain/snow showers with snow levels around 6000 feet. As the next system and strong cold front move from northwest to southeast through the day, we will see an increase in large scale lift and some heavier precipitation developing and snow levels dropping. The timing for the heavier snow and low elevation rain is late morning to early evening along/west of US89/I-17 and from afternoon through late tonight or early Friday morning farther east. Snow levels will drop with the cold front, from around 6000 ft at sunrise to 4500-5500 ft by 5 PM, then 4000 ft by late evening. There hasn't been much change in the forecast over the past 24 hours, and the current Winter Weather Advisories will remain in place. Later shifts will need to watch trends and possibly extend the far eastern AZ zones (White Mtns, Chuska Mtns, Black Mesa) a bit farther into the early morning hours Friday. There are also several models that develop a heavier band of snow on the north side of the low as it passes through northeast AZ late tonight, mainly affecting Black Mesa, Chinle Valley, and the northern Chuskas and we bumped snow amounts up in that area. There is now 1-3 inches forecast in the Chinle Valley including along Hwy 191 from Chinle up to Hwy 160. It will become windy today as well, with west to southwest winds 15-25 mph and gusts 30-40 mph. This could make travel even more hazardous in areas getting heavy snow, with visibility further reduced due to blowing snow. Late tonight through Friday - winds will shift to north/northeast at 10-20 mph gusting 25-35 mph, strongest over and just south of terrain features. These winds combined with temperatures 10-15 below normal, will result in wind chill values near zero in the high country Friday morning and not getting out of the teens in the afternoon. Otherwise, Friday will be much drier with clearing skies.

Saturday through next week - high pressure is forecast to be centered over California, with fair weather over Arizona. With the position of the high, northeasterly winds will persist each day and will keep the warming trend slow at first especially for the weekend. Temperatures return to near normal by Monday and then up to 10 degrees above normal by Wednesday and Thursday.

AVIATION...Thursday 08/12Z through Friday 09/12Z

WDSPRD MVFR/IFR conditions are expected in SHRA/SHSN through much of the period, but mainly from 18Z to 03Z. Brief periods of LIFR possible in the higher terrain in +SHSN and BLSN this afternoon. Winds W/SW 10-20 kts with gusts 25-35 kts, becoming W/NW 5-15 kts after 03Z/06Z.

OUTLOOK...Friday 09/12Z through Sunday 11/12Z...Lingering MVFR in ISO SHSN in vicinity of KSJN/KJTC through 17Z Sunday, otherwise VFR. Winds N/NE 10-20 kts with gusts 20-30 kts on Friday, subsiding to 5- 15 kts Friday night and Saturday. Locally gusty NE winds remain downwind of the terrain during the overnight hours.

FIRE WEATHER...Today and Friday

Rain and snow down to 5000 feet are expected today as a cold front moves through northern Arizona. Drier and colder conditions set in on Friday. Gusty southwest winds 15-25 mph with gusts 30-40 mph, becoming west/northwest in the afternoon. Winds north/northeast 10-20 mph with gusts up to 30 mph on Friday. Saturday through Monday...Dry conditions and gradually warming temperatures, along with north/northeast winds 5-15 mph each day.

FGZ WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory from 8 AM this morning to 8 PM MST this evening for AZZ004-006-007-015-016.

Winter Weather Advisory until 11 PM MST this evening for AZZ011- 017-039.