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.

DISCUSSION

A series of shortwave troughs will deliver colder temperatures, windy conditions and good chances for mountain snow and lower elevation rain through Friday. 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.

For today and Tuesday...The first in a series of shortwave troughs will move from west to east across Arizona. In advance of the trough strengthening surface pressure gradients will result in widespread south to southwest winds at 15-25 mph. Gusts of 40-50 mph are anticipated along and north of a Bagdad-Prescott- Show Low line. These strong winds are likely to continue tonight through Tuesday, gradually diminishing over western portions early Tuesday but hanging on further east through the end of the day Tuesday. As a result, a Wind Advisory is in effect for portions of Arizona through Tuesday. As moisture increases and upper dynamics move in tonight it is expected that widespread showers will develop. Showers will be most intense over the Mogollon Rim and Mountains to the south due to the proximity of deeper moisture and strong upslope winds. Snow levels start out in the 7,000-8,000 foot range this evening but then fall to 5,500-6,500 feet by midday Tuesday. Elevations above 6000 feet are expected to see general snowfall accumulation of 3-6 inches with higher amounts over the San Francisco Peaks and highest elevations of the Kaibab Plateau. Likewise, lower elevations will see 0.20-0.45 inches of rainfall. The main limiting factor on amounts will be the fast movement of this trough across the area.

From Wednesday into Thursday...The next shortwave trough will move in during the day Wednesday. Winds will remain strong on Wednesday, generally from the southwest at 15-25 mph area wide but with gusts of 40-50 mph from the Mogollon Rim northward. Winds becoming quite a bit lighter on Thursday as the trough heads eastward. This will be colder system as it will approach from a more northerly direction. As a result, the snow level looks to start out in the 5,000-6,000 foot range but then drop to 3,500-4,500 feet (or even lower) before the trough exits the area on Thursday. It looks like the highest snow accumulations with this second trough (a bit further north trajectory) will be from around Happy Jack northwestward over the higher terrain. The forecast is for general snow accumulations of 4-8 inches at elevations above 6,000 feet across this area with potentially more than a foot over the very highest mountain locations. The lowest elevations are forecast to see 0.10-0.25 inches of rainfall.

Looking at Friday into the weekend...Forecast models are have lock on to another fast moving shortwave trough for Arizona on Friday. However, forecast models and associated ensembles are in conflict with the chances for precipitation with this third wave. The GFS brings good chances with an additional 3-6 inches of snow to our mountain areas. The latest run of the European Model is only showing 1-2 inches resulting from a faster moving less amplified trough. Confidence in the weather associated with this third trough remains low, so stay tuned because things could go either way. High pressure and fair weather still looks on track for the weekend.

AVIATION...Monday 16/12Z through Tuesday 17/12Z

VFR conditions to start the period. Rain showers begin to move in causing MVFR in spots after 00Z. Ceilings fall quickly to MVFR at lower elevations due to rain showers, but higher elevations will see IFR or LIFR conditions due to snow or heavy snow showers. Winds increase S-SW 10-20kts, gusts 30kts after 15Z, then increase to S-SW 20-30kts gusts 35-45kts after 18Z. Winds will not decrease overnight and remain at S-SW 20-30kts, gusts 35-45kts.

OUTLOOK...Tuesday 17/12Z through Thursday 19/12Z...Multiple storm systems will move in during the time period, with snow levels lowering with each passing system. Lower elevations will see VFR-MVFR conditions with rain showers, while terminals above 5000ft likely seeing anywhere from MVFR to LIFR conditions due to rain/snow, snow, heavy snow, or periods of blowing snow. Winds S-SW 15-30kts, gusts 35-40kts throughout the time period, including overnight hours.

FIRE WEATHER...Today and Tuesday

Windy and dry most of today, but rain/snow showers begin spreading from west to east overnight. Snow levels start around 7000-8000 feet by the onset of precipitation, then fall to 5000-6000 feet by midday Tuesday. Heaviest rain/snow accumulations are anticipated late Monday night through Tuesday morning. Winds are SW 15-30 mph with gusts 35-50 mph through the period, remaining elevated overnight. Minimum RH values Monday range from 15-30% in the eastern half of the state to 25-40% western half. Minimum RH values Tuesday range from 25-40% northeast Arizona deserts, to 50-80% in the mountains.

Wednesday through Friday...Periods of widespread rain and snow showers continue as a series of weather disturbances pass through. Accumulating snow or wetting rains are likely through the period, with snow levels continuing to drop. Winds SW 15-25 mph gusts 35-45 mph Wednesday, SW-W 10-15 mph gusting to 25 mph Thursday and Friday.

FGZ WATCHES/WARNINGS/ADVISORIES

Wind Advisory from 11 AM this morning to 8 PM MST this evening for AZZ004-015>017.

Winter Weather Advisory from 8 PM this evening to 5 PM MST Tuesday for AZZ004-015>017.

Wind Advisory from 11 AM this morning to 8 AM MST Tuesday for AZZ006>008-038.

Wind Advisory from 11 AM this morning to 5 PM MST Tuesday for AZZ012>014-039.