Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 210445
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
945 PM MST Fri Jan 20 2017

.SYNOPSIS...
A series of Pacific storms will move into the region over the next
few days. The strongest and wettest storm will affect the region
tonight through early Saturday. Snow accumulation will be above 5500
feet. A Winter Storm Warning is posted for the mountains east of
Phoenix through Saturday afternoon. A break in the weather is
expected Saturday night and early Sunday, however another Pacific
storm is expected into the region later Sunday through next Tuesday.
Dry but cool weather will settle over the region for the middle of
next week.

&&

.DISCUSSION...

An expansive area of rainfall has developed across much of western
and central Arizona, in association with a strong Pacific storm
system moving across the Southwest. Observed precipitable water
values both at Tucson and San Diego were above the 90th percentile
for this time of year. Moderate to locally heavy rainfall rates are
expected to peak through early morning across the greater Phoenix
area, while persisting a bit longer over higher terrain areas north
and east of Phoenix. A winter storm warning also remains in effect
for elevations above 5500 feet for southern Gila County. The radar
estimated freezing level is currently near 6000 feet, and should
continue to fall overnight with heavy snow likely at higher elevation
areas.

The potential for strong wind gusts also remains a concern into early
tomorrow morning. Surface winds have veered towards the southwest
ahead of a cold front moving through western Arizona, and should
continue strengthening given 30-40 kt of flow observed in the KIWA
VAD wind profiler above 1 km. Wind gusts of 30 to occasionally near
40 mph, especially south and east of Phoenix, will be possible this
evening, before gradual weakening occurs as a 700-mb speed max
quickly shifts into New Mexico.

Precipitation chances will decrease from west to east overnight,
becoming focused across the higher terrain during the afternoon
through tomorrow afternoon. Otherwise, mostly drier conditions with
breezy west winds appear probable to develop across the lower
deserts.

&&

.PREVIOUS DISCUSSION...

Sunday and Monday Night...

Another Pacific weather system will be approaching the southern CA
coast on Sunday. Considerable clouds will spread into the region
Sunday afternoon through Monday. A slight chance of showers will
develop Sunday, increasing to a chance of showers Sunday night and
Monday.  Showers will dissipated from west to east Monday night.

Tuesday through Friday...

A few lingering showers are possible over the mountains east of
Phoenix Tuesday, otherwise dry and rather cool weather is expected
most of next week. Afternoon temperatures should fall to 6 to 8
degrees below normal.

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA,and KSDL:
Periods of moderate to heavy rainfall continue to affect area
terminals this evening, with reductions in visibility down to 1-2
miles and ceilings down to 1000 feet possible at times. Surface winds
have shifted towards a general southerly direction, and will continue
to veer towards the southwest as a cold front moves into central
Arizona, while a few gusts to 30-40 mph are possible through at least
07Z. Improvements in visibilities should occur in the wake of the
cold front as rainfall chances decrease. Ceilings should also
eventually rise as slightly drier air works into the area, currently
expected to improve to above 5k feet by 13Z.

Southeast California/Southwest Arizona including KIPL and KBLH:

Rainfall chances have decreased as a cold front has moved into
western Arizona. Lingering cloud cover with bases of 6-8k ft should
persist through 08Z at KBLH, before becoming more scattered in
nature. Surface winds have been slow to respond to stronger flow
aloft, with only occasional gusts to around 30 kt anticipated. Winds
should remain out of the west through morning with improvements in
ceiling heights and reduced cloud cover anticipated.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Sunday through Thursday: Another Pacific low pressure system will
move into the districts Sunday afternoon, producing additional
rainfall into Monday along with breezy to windy conditions. High
pressure will gradually rebuild across the area Tuesday and
Wednesday, resulting in a drying trend though temperatures will
remain below normal. Fire danger will remain low through the period
due to the persistent and anomalously moist conditions.

&&

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

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Wind Advisory until 8 AM MST Saturday for AZZ022-023-026>028.

     Winter Storm Warning until 11 AM MST Saturday for AZZ024.

CA...None.
&&

$$

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DISCUSSION...Rogers
PREVIOUS DISCUSSION...Vasquez
AVIATION...Rogers
FIRE WEATHER...Nolte/Hirsch



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