Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 182132
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
232 PM MST Wed Jan 18 2017

.UPDATE...Updated aviation discussion.

&&

.SYNOPSIS...
A series of Pacific storm systems are forecast to move into the
region Thursday night through Saturday. The first system will move
into the area Thursday night and early Friday, with a stronger
system Friday night through early Saturday. Snow accumulation will
be above 5500 feet, with a Winter Storm Warning posted for the
mountains east of Phoenix. A break in the weather is expected
Sunday, however another Pacific storm is expected in the region
Monday and Monday night.  Dry but cool weather will develop next
Tuesday and Wednesday.

&&

Tonight through Saturday...

The transitory high pressure system over the area this afternoon
will rapidly weaken as a new series of Pacific storms begin to race
into the region late tonight through Saturday.  The initial weather
system is forecast to move into southeast CA and far western late
tonight, the slowly move across the remainder of southwest and south
central AZ, including Phoenix, thursday afternoon and night.

The highest probabilities of precip over our forecast area,
southeast CA to south central AZ, Thursday night will develop over
areas from Phoenix eastward.  Of particular concern Thursday night
are lowering snow levels, after midnight falling to 5000 feet with
accumulating snow above 5500 feet. The Winter Storm Watch issued
earlier has been upgraded to a Winter Storm Warning above 5500 feet
in southern Gila County zone 24. Most population centers in southern
Gila County are below that level, so concerns are over the higher
elevations of the San Carlos Indian Reservation bordering the White
Mountains, and Signal Peak (7000 ft) just south of the city of
Globe. About 4 to 5 inches of wet snow are possible above 5500 feet
in southern Gila County through Friday morning.

Friday afternoon will be inbetween systems, however cloudy skies and
a few showers will continue throughout the day before the next or
2nd even stronger disturbance moves bodily into the area Friday
evening through Saturday morning.  This will be the heaviest precip
producer with another 5 to 8 inches of snow above 5500 feet in
southern Gila County. Therefore storm total snowfall in southern
Gila County between late Thursday night through Saturday morning
could approach a foot or 12 inches in spots.

Lighter instability rain and snow showers will continue throughout
the day Saturday generally from Phoenix eastward.

Sunday and Sunday Night...

A weak high pressure system will develop over the region this period
for dry weather but with continued below normal temperatures.

Monday and Monday night...

Another Pacific weather system is forecast to move into the area
from west to east on Monday and Monday evening. This system is not
as strong over our forecast area as it will be in northern AZ,
however a chance of showers is foreast.

Tuesday and Wednesday...

Dry northern flow aloft will develop this period with much below
normal temperatures.

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:

Expect light winds to favor familiar diurnal sequences throughout
the period. Skies will be clear to mostly clear with increasing
cloudiness beginning this evening and later tonight with BKN-OVC high
cloud CIGS moving in from the west near 25Kft. Expect BKN CIGS to
lower to near 8Kft from 12-15Z with a chance of light rain or
sprinkles during that time. The confidence of light rain on Thursday
morning at the terminals was not high enough to include it in the
TAFS at this time.

Southeast California/Southwest Arizona including KIPL and KBLH:

Light and variable to light southerly component winds will begin to
favor the west and southwest later this evening and tonight from
about 03-06Z. Expect clear to mostly clear skies with increasing
cloudiness beginning this evening from about 03-06Z with CIGS
lowering to near 6-8Kft. from about 07-12Z along with a chance of
mainly light rain showers in the vicinity of the terminals.
Southwesterly winds at KBLH will become a bit breezy tonight with
some gusts near 16 Kt. beginning about 07Z.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Friday through Tuesday: A series of low pressure systems will bring
periods of precipitation along with persistent below normal
temperatures through early next week. The strongest storm system will
move through the area Friday night, bringing wetting rains and
mountain snow. Widespread breezy to windy conditions will also
accompany the system Friday and Saturday. However, fire danger will
remain low due to the relatively moist conditions. After a brief
respite Sunday, conditions will again deteriorate Monday with
increasing winds and precipitation likely. Unsettled conditions will
persist Tuesday particularly across the higher terrain north and east
of Phoenix.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter reports of rain and snow will likely be needed later this
week.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Winter Storm Warning from midnight Thursday night to 11 AM MST
     Saturday for AZZ024.

CA...None.
&&

$$

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DISCUSSION...Vasquez
AVIATION...Sawtelle
FIRE WEATHER...Hirsch


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