textproduct: NWS Flagstaff

SYNOPSIS

A series of disturbances are expected to bring winter weather conditions to much of northern Arizona through the end of the week. Gusty winds also likely, especially today and Wednesday. Mild weather looks to return for the weekend.

DISCUSSION

The first of 3 shortwave troughs is currently making its' impact across northern Arizona. As a result, we are starting to see light snow accumulation here at the NWS office in Bellemont. It's been raining for the last few hours due to snow levels flirting with 7000', but snow levels are steadily dropping and will continue to do so through the next several hours. By this afternoon, snow levels will generally range between 5500-6000' across our CWA. Rain and high elevation snow showers will continue through much of the morning/afternoon creating hazardous travel conditions for your Tuesday morning commute. A Winter Weather Advisory remains in effect for the Kaibab Plateau, Mogollon Rim, and White Mountains through 5 PM MST this evening. Even though we anticipate the bulk of the precipitation to fall with the main frontal passage, this synoptic pattern will favor upsloping conditions throughout the afternoon, allowing localized areas across south-facing slopes (primarily the Mogollon Rim and Kaibab Plateau) to see persistent showers this afternoon and continued winter weather travel conditions. Of course we can't forget to mention the projected snow totals for this first system. Areas above 6000' are forecast to receive a dusting to 1". Locations above 7000' have remain persistent in the 3 to 7" range (but again localized areas could see higher values from upslope forcing). And finally, the highest mountains peaks (generally 8000' and above) could enjoy a foot or more of fresh new snow. I guess there is also one more item to mention for this first disturbance (if you haven't noticed already), but it's very windy! Many locations across our CWA are gusting between 30 and 40 mph, with a few sites surpassing 50 mph. These elevated winds look to continue through at 5 PM MST for the Little Colorado River Valley and Black Mesa Zones. The Coconino Plateau, Grand Canyon Country, Oak Creek/Sycamore Canyons, and Yavapai County Mountains are also in the on-going Wind Advisory, but these zones will drop off by 8 AM MST this morning.

Shortwave number 2...The next disturbance looks to slide through northern Arizona beginning late Tuesday/early Wednesday. There is still a Winter Storm Watch in place for the Kaibab Plateau and Mogollon Rim in correlation to the heaviest snowfall amounts forecast. These areas could warrant a Winter Storm Warning eventually and other locations could see a Winter Weather Advisory go up. Snow levels will drop closer to 4500-5000' for this second system, so areas that only got to enjoy rainfall on Tuesday may get to enjoy a few snowflakes by the middle of the week. The decision on what products may be necessary will likely be decided on the upcoming shift. Either way, anticipate hazardous travel to persist. One product that was added to the forecast for Wednesday was a High Wind Watch for the Little Colorado River Valley, White Mountains, and the Northeast Plateaus and Mesas. Sustained south to southwest winds look to be 35 to 45 mph throughout Wednesday afternoon, with gusts near 60 mph possible. Gusty winds will be likely across other locations as well, but any future Winter Weather products will cover the need for a Wind related products.

Shortwave number 3...The final shortwave of this series looks to slide through Thursday into Friday. There is still uncertainty with how this system will play out, but within the last 12 hours snowfall amounts have increased compared to the previous forecast package. Hard to say where final amounts will land for this last system, but additional Winter Weather products will likely be necessary. Outside of more precipitation, breezy winds will stick around primarily Flagstaff eastward.

Over the weekend...Although chilly temperatures will still be present on Saturday, drier/calmer weather looks to return for the weekend. Daytime highs should even creep back towards normal on Sunday for this time of year thanks to a building area of high pressure.

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

Isolated to scattered -SHRA/-SHSN will bring localized MVFR/IFR conditions through Tuesday evening, primarily along the higher terrain. A more consistent band of SN/RA moves from west to east along a front after 12Z Wednesday, bringing drops to IFR/LIFR. South to southwest winds 20-30 kts gusting 35-45 kts through the period, though gusts up to 50-55 kts may be possible along the FROPA.

OUTLOOK...Wednesday 18/18Z through Friday 20/18Z...Mainly MVFR/IFR conditions with periods of VFR conditions. Worst impacts expected through 00Z/Thursday and again after 06Z/Friday, with IFR/LIFR conditions in +SN/+RA and BLSN. South to southwest winds 15-30 kts with gusts 35-50 kts on Wednesday, becoming southwest to west at 10-20 kts with gusts 35 kts on Thursday.

FIRE WEATHER...Today through Wednesday

Widespread rain and snow showers, heaviest through this morning. Additional widespread rain and snow Wednesday morning into the evening. Conditions will remain scattered and showery even outside of the above periods. Snow levels falling to 5000-5500 feet by midday Today, then 4000-4500 feet by Wednesday evening. Winds southwest at 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. Snow levels may drop as low as 3500- 4000 feet on Friday. Fair weather looks to return by Saturday. Winds 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 this afternoon for AZZ004- 015>017.

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

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

High Wind Watch from Wednesday morning through Wednesday evening for AZZ012>014-017-040.