Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 202222
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
325 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...

Tonight and Saturday...

Most of our forecast area, southeast CA to south central AZ, was
inbetween storm systems this afternoon. However since we are under
the storm track, cloudy skies and areas of light rain have develop
ahead of the next storm expected tonight and early Saturday.

Morning weather balloon soundings showed another area significant
low level moisture had moved ashore into southern CA, and will be
pushed along the frontal zone and upslope into central and eastern
AZ tonight. Strong dynamics with this next system will produce
considerable rain and mountain snow over our portions of south
central AZ, generally from Phoenix north through east.

850 mb southwest winds approaching nearly 60 mph tonight will
generate strong upslope conditions over the mountains north and east
of Phoenix, which should realize between 1.50-2.00 inches of rain.
Needless to say heavy snow is expected in the higher elevations.
Snow accumulation will generally be above 5500 feet. A Winter Storm
Warning for southern Gila County continues through Saturday
afternoon.

Rain and perhaps a thunderstorm falling into the belt of low level
winds will likely bring down wind momentum for gusty surface winds
tonight across portions of southwest and south central AZ. A wind
advisory continues tonight for these areas.

As the storm pulls away early Saturday, showers will slowly diminish
from west to east, but with lingering rain and snow in the mountains
northeast through east of Phoenix. It will become partly cloudy
Saturday night.


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:
Scattered light showers will continue off and on the rest of this
afternoon and into this evening ahead of an approaching cold front.
Ceilings will fluctuate quite a bit (4-6 kft MSL in and near showers
and 7-9 kft MSL in between showers). Winds will favor the southeast
quadrant. Winds in the lower levels above the surface will
strengthen in the early evening and create low level wind shear
conditions. As the frontal zone moves through, ceilings and
visibilities will deteriorate rapidly after 03Z down to IFR and even
LIFR before beginning to improve after 09Z. Isolated embedded
thunderstorms are possible during that time as well. Strong
southwesterly surface winds will develop with the arrival and
passage of the front with a prolonged period gusts to 30 kts and a
shorter window with gusts to 40 kts (roughly 04Z-08Z).

Southeast California/Southwest Arizona including KIPL and KBLH:

Isolated showers with local ceilings of 6-8 kft MSL can be expected
through 23Z (otherwise ceilings of 8-10 kft MSL) ahead of an
approaching cold front with south and southeasterly winds slowly
strengthening. Heavier and more widespread showers can be expected
roughly between 00Z-04Z as the frontal zone passes with ceilings at
3-5 kft MSL and visibilities dropping to 3-5 SM (locally 1-3 SM) in
rain and fog. Strong southwesterly winds gusting 30-35 kts can be
expected (brief, localized gusts to 40 kts). Shower activity
decreases from west to east after 04Z and winds slowly weaken.

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 from 8 PM this evening to 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...Vasquez
AVIATION...Nolte
FIRE WEATHER...Nolte/Hirsch


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