Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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853
FXUS65 KFGZ 200337
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
837 PM MST Thu Jan 19 2017

.SYNOPSIS...A series of winter storms will affect the region from
tonight, through Monday or Tuesday. These will be cold systems,
with heavy accumulations of snow across the high country.
Hazardous driving conditions should be anticipated for the next
several days.

&&

.DISCUSSION...Areas of rain and snow showers were being observed
across northern Arizona during the evening. Showers were most
numerous across the area of the Mogollon Rim. Even a stray
thunderstorm or two over far western Arizona. For the remainder of
the night, shower activity will continue but taper off toward
sunrise. The break will be short with a stronger system then
spreading additional rain and snow across the area starting
midday Friday. The forecast package looks good with no updates
anticipated at this time.

&&

.PREV DISCUSSION /302 PM MST/...

SHORT TERM...through Saturday afternoon.

The first short wave trough is making its way into Arizona this
afternoon from southern California. We are in a region of broad
lift ahead of the trough, and in fact a relatively large area of
light to moderate precipitation developed across southwestern
portions of Yavapai County and has begun to move across the
Prescott area. Webcams in downtown Prescott indicate snow falling,
but with wet roads and with no accumulation as of yet. Will
continue with a rain/snow mix through this afternoon in the
5000-5500 foot range, likely becoming all snow this evening as
snow levels drop to around 5000 feet by late tonight. We raised
snow amounts by a couple inches or so in the 5000-5500 foot range
with the event from now through tonight. Otherwise, precip and
snow amounts are relatively consistent with previous forecasts.
Hi-res models, including the experimental HRRR, show the heaviest
precipitation moving across northern Arizona from now through late
tonight, with some lingering showers through the early morning
hours especially in far northeast Arizona and the White Mountains
region.

Though snow showers will likely not completely stop especially
over high elevation locations, expect a brief break in moderate to
heavy precipitation on Friday morning in the wake of the first
short wave trough. The next trough is on the way quickly, with
lift influenced by this second trough initiating over northern
Arizona by early afternoon on Friday. The event from late Friday
afternoon through early Saturday morning will feature a moist mid-
level jet along the base of the trough. The strength of the Friday
evening system, combined with the amount of available moisture,
will enhance snowfall amounts in the higher elevations as well as
rainfall amounts in the low elevation upslope regions of Gila and
southern Yavapai County. The heavy snow and associated hazardous
winter conditions have been well advertised for many days; we also
need to be concerned about potential flooding in the lower
elevations of Gila/southern Yavapai county during and after the
rain on Friday night as the water runs off.

Precipitation will likely continue on the east Rim and over the
White Mountains during the day on Saturday, ending fairly rapidly
from west to east Saturday afternoon as the trough moves out of
northern Arizona.

LONG TERM...Saturday evening through Thursday morning.

Progs are in good agreement through this Wednesday. A fast moving
shortwave ridge will bring clearing conditions from west to east
across the northland Saturday night. This break to last less than
12 hours though as the 3rd winter system sets up off the west
coast on Sunday. This system to spread clouds across our area with
precipitation developing across western AZ. Snow levels should be
rising to between 5500 feet on the Kaibab Plateau to 7000 feet in
the White mountains Sunday afternoon and evening ahead of a strong
cold front. This front moves west to east across the area Sunday
night-Monday morning with gusty southwest winds. Snow levels to
fall to 4500-5500 foot range with precipitation likely. Still to
early for snow amounts. Models are insistent that h5 temps will be
around -30C overhead from Monday evening through at least
Wednesday. This will keep some instability showers going through
Tuesday. Temperature guidance showing max temps around 30 in the
high country with mid 40s in the lower valleys of Yavapai county.
Overnight lows in the single digits and teens for most of us by
Tuesday. These temp forecast may go lower as we move into next
week.

Slight chances of showers to continue Wednesday across Navajo and
Apache counties, otherwise it is just dry and cold.

&&

.AVIATION...For the 06Z package...The first in a series of storm
systems will exit Arizona overnight with a second stronger system
moving in Friday afternoon and night. Expect widespread MVFR
conditions and areas of IFR/LIFR conditions in rain and snow showers
through the next 24 hours. Aviation discussion not updated for TAF
amendments.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...Winter Storm Warning until noon MST Saturday FOR AZZ004-006>008-
015>018-038.


&&

$$

PUBLIC...McCollum/AT
AVIATION...McCollum


For Northern Arizona weather information visit
weather.gov/flagstaff



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