Area Forecast Discussion
Issued by NWS Tucson, AZ
FXUS65 KTWC 190354
Area Forecast Discussion
National Weather Service Tucson AZ
854 PM MST Wed Jan 18 2017
.SYNOPSIS...A series of storms will spread valley rain, mountain
snow and gusty winds over Arizona Thursday night into Saturday.
Snow levels will lower through that time potentially reaching the
valley floors east of Tucson by Saturday. After a break in the
weather on Sunday another storm system is likely on Monday and
.DISCUSSION...A very brief shortwave ridge is phasing overhead
right about now with a much stronger trough developing upstream.
We`re still on track for the initial energy ahead of the main
system to push across the area late today and tonight, delivering
only a glancing blow to Southeast Arizona. This will set the table
for a much stronger, wetter and colder system Friday night into
Saturday morning. A look at 00z analysis and model data
reinforces confidence in our current forecast package. Please see
the previous discussion below for details.
.AVIATION...Valid through 20/06Z.
VFR with increasing cirrus from the west tonight, and then SCT-
BKN 100-140 AGL after 19/12Z. Surface winds will exhibit typical
diurnal trends and generally be less than 10 kts through Thursday
morning, then increasing from the southwest after 19/20z. Aviation
discussion not updated for TAF amendments.
.FIRE WEATHER...A series of storms will spread a good amount of
precipitation across the area late Thursday into Saturday. Gusty
west to southwest winds are expected at times through this period
especially Friday night and across the mountains. Dry weather
returns Sunday before another storm affects the area Monday into
.PREV DISCUSSION...Clouds on the increase tonight with a few
light showers/sprinkles possible Thursday afternoon mainly west
and north of Tucson. Showers will be spreading west to east
Thursday night into Friday morning with the best chances for
rainfall and accumulation mountain snows being from Tucson north
and northeast. The winter storm watch was upgraded to warning,
first starting with the mountains near Tucson northeast to the
White mountains for Thursday night into Friday morning. Snow
levels lowering down into the 4500 to 5500 foot level with
accumulating snows above 5500 feet.
There will be a break in rainfall and mountain snow intensity
between storms as snow levels rise a bit before the second stronger,
colder and wetter system starts to impact the area later Friday and
continuing into Saturday. Snow levels down into the 4000 to 5000
foot level with significant snow accumulations above 5500 feet where
a Winter storm warning continues for the higher terrain above 5500
feet. Strong gusty winds will bring periods of blizzard like
conditions to the mountains Friday night into Saturday. Wind speeds
at the lower elevation could reach wind advisory criteria on Friday.
Two day storm totals for valley rainfall range from 0.50" to 1.75"
with locally higher amounts over 2" possible, especially north of
Tucson. Snowfall amounts were also increased with totals above 5500
feet in the 12 to 36 inch range with locally higher amounts
possible. Minor snow accumulations are possible down to 4000 feet by
Conditions improve west to east Saturday night into Sunday with
colder overnight lows likely Sunday morning with eastern valleys
seeing temperatures in the 20s.
The storm parade continues early next week as long wave trof axis
remains over the western CONUS.
High temperatures for the next 7 days will remain below normal
with coolest highs occuring Friday and Saturday.
Winter Storm Warning from 8 PM Thursday to noon MST Saturday for
Winter Storm Warning from 5 PM Friday to noon MST Saturday for
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