Area Forecast Discussion
Issued by NWS Tucson, AZ

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061
FXUS65 KTWC 202125
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
225 PM MST Fri Jan 20 2017

.SYNOPSIS...An approaching storm system will spread widespread valley
rain and significant mountains snows across southern Arizona tonight
into Saturday. The precipitation will taper off Saturday evening with
mostly dry conditions lasting into Monday. Another storm system will
impact the region later Monday through Wednesday with cool
temperatures and a chance of showers.

&&

.DISCUSSION...Scattered light rain and mountain snow showers have
occurring through the day thus far with generally light amounts as
expected. More significant bands of precipitation are just off to
the west headed this way. As this happens the winds are beginning to
pick up with gusts into the 30s and 40s already. Even had a twitter
report of some dust being lofted off the Wilcox Playa.

This is only the beginning on a number of fronts. For the wind, wind
advisory criteria will easily be met across much of the lower
elevations and in expectation of stronger winds as typical in the
Sierra Vista area thanks to the Huachuca mountains a high wind
warning has been issued for tonight. For most areas gusts into 50s
are possible with gusts to 70 mph possible in the warning areas. This
includes the mountains where very strong winds are likely, primarily
areas with a south to west exposure and across the ridges. The winter
storm warning these areas also covers the wind. These winds will pose
problems with blowing and drifting snow in the mountains.

Now about the precipitation, the bulk of which will be tonight
through Saturday morning we and are still expecting 0.50 to 1.25
inches in general valleys and locally higher amounts near the
mountains. Convective allowing models continue to highlight a decent
convective band rolling through later tonight with the potential for
some thunder to wake you up around and after midnight.

For the mountains there is the potential for considerably more
precipitation thanks to strong upslope flow enhancement with 2-3
inches of liquid equivalent a good bet higher elevation`s. With the
idea that this will be in the form of snow above 7000 ft storm
totals of 12-36 inches are expected above that elevation. Lower but
still significant amounts are expected between 5-7000 ft. See the
warning statement for further details.

Saturday morning the colder air moving into the region will settle
the snow level down to the 4-4500 ft level with snow showers, so
brief light accumulations in the high valleys east of Tucson and up
near Oracle are possible Saturday morning.

As the storm moves off to the east later Saturday precipitation will
end from west to east during the afternoon and evening hours. By
Sunday morning the precipitation should be over area wide with
clearing skies and cold temperatures. Readings below freezing will
be common east and south of Tucson.

Dry weather will linger into sometime Monday before the threat of
showers returns as a couple of upper level systems move across the
state Monday night through Wednesday. After a relatively mild Monday,
Tuesday through Thursday will be a rather cool period however these
systems will not be as moist as the current one so expect much less
precipitation. Then beyond that, well, warmer and dry from the looks
of things through the following weekend.

&&

.AVIATION...Valid through 22/00Z.
Numerous SHRA/mountain SHSN will develop this afternoon and continue
through the night with ISOLD TSRA possible tonight mainly between
21/06z and 21/12z. Expect widespread MVFR conditions and occasional
IFR conditions with mountains mostly obscured through Saturday
morning then conditions improving from the west. Southwestly surface
wind increasing to 15-35 kts with gusts of 30-50 kts then becoming
westerly late tonight. Surface wind diminishing somewhat after 12Z
Saturday but still gusty. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...A strong storm system will move across the area
through Saturday morning with widespread valley rains, significant
mountain snows and strong winds. Winds and precipitation will taper
off west to east Saturday with mostly dry conditions Saturday night
into early Monday. Another series of storms will impact the area
Monday night through Wednesday with cool temps and occasional breezes but
they will not expected to be significant precip producers. Dry and
warmer conditions late next week into the following weekend.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until noon MST Saturday for AZZ510-511-514.

Wind Advisory from 8 PM this evening to 8 AM MST Saturday for
AZZ501>508.

Winter Storm Warning from 5 PM this afternoon to noon MST
Saturday for AZZ512-513-515.

&&

$$

PUBLIC...Cerniglia
AVIATION....Cerniglia
FIRE WEATHER...Cerniglia

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