Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 200334

Area Forecast Discussion
National Weather Service Phoenix AZ
835 PM MST Thu Jan 19 2017

A series of Pacific storm systems will move into the region. After a
weak disturbance tonight, a stronger and wetter system will affect
the region Friday 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
Saturday night and early Sunday, however another Pacific storm is
expected in the region later Sunday through Monday night. Dry but
cool weather will settle over the region for the middle of next week.



The 1st in series of Pacific storm systems that will be affecting
our region over the next several days is now moving across South-
Central AZ at this hour. Current 88D radar imagery is showing very
light shower activity moving eastward across Maricopa County, and
into southern Gila county. So far, rainfall amounts with this system
have been quite, light, mainly 0.10 inch or less, with many spots
only seeing trace amonuts of rainfall. Latest HRRR high-res model
guidance continues to show light shower activity developing through
the rest of tonight over south-central AZ, but with many areas
likely not seeing measurable rainfall between now and Friday
morning. Further to the east, the rainfall should turn to snow above
5500 feet, with a few inches still possible over the highest peaks
of our cwa between now and early Friday. For the short term, have
adjusted POPS downward through the rest of this evening and up a bit
overnight over the lower deserts to reflect updated high-res model
forecasts, and also made some adjustments to hourly
temp/dewpoint/wind grids to better reflect current trends.



Tonight through Saturday...

A series of Pacific weather systems has begun to move into the
region. The first one, a minor one, moved through southwest and
south central AZ this morning, followed by another system late this
afternoon and evening. Most showers through tonight will be on the
light side, except in the upslope areas of southern Gila county
where rain and snow should be a little heavier.

With the passing systems tonight through Saturday, snow levels will
rise and fall with each system. For example, in the area where we
have a Winter Storm Warning in southern Gila County, snow levels
fall to near 5500 feet late tonight, lift to 6000 feet Friday
evening, then fall to 5000 feet by Saturday morning. In general the
Winter Storm Warning in southern Gila County is posted above 5500 ft
where storm total accumulations by Saturday afternoon could reach
nearly a foot in the highest elevations.

With the cold frontal passage Friday night, low level winds at 5000
feet begin to approach 45-60 mph in a belt from just east of Yuma to
Phoenix. Rainfall and isolated thunderstorms could tap this momentum
to develop gusty surface winds in the 30 to 45 mph range, higher
near thunderstorms.  A Wind Advisory is posted for southwest and
south central AZ Friday night.


A break in the weather will develop Sunday afternoon, but with
cloudy skies and a slight chance of showers over the mountains of
southeast CA ahead of the next weather system for Sunday night and

Sunday night and Monday...

Another Pacific weather system will move into the region this
period. The character of precipitation will be light.  Additional
snowfall is expected in southern Gila County above 5800 feet Monday
afternoon and evening with perhaps an inch or two.

Tuesday through Thursday...

Partly cloudy, drier and colder weather is expected this period
under northerly flow aloft from Nevada and Utah.


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

Expecting sct-bkn ceilings to in the 3-5k foot range to continue
this evening. Showers are approaching from the west and should begin
to affect terminals as early as 22Z, persisting through 06-07Z. Rain
should become more spotty after this period across south-central AZ,
with some improvements in ceilings possible to around 8k feet.
Easterly winds around 5 kt should be maintained through late evening
as well, before a shift towards the southwest is anticipated after

More widespread rainfall is anticipated late Friday evening and
Saturday morning and will be associated with another period of
increased cloud cover. Winds will also strengthen during this time
as a cold front approaches, shifting from southerly to westerly by
early Saturday morning.

Southeast California/Southwest Arizona including KIPL and KBLH:

Areas of sct-bkn ceilings as low as 7k feet, along with scattered
showers, have developed across southeast California into the lower
Colorado River Valley. Otherwise, expect sct clouds with bases near
10-12k ft this afternoon and overnight. Gusty west winds are still
anticipated to develop across the Imperial Valley this afternoon,
before weakening around 03Z. Periods of more widespread showers are
possible across the area Friday afternoon, and will be associated
with an increase in westerly winds.

Aviation discussion not updated for amended TAFs.


Saturday through Wednesday: After a brief respite from the rain
Saturday evening through Sunday morning, precipitation associated
with another low pressure system will develop Sunday afternoon and
evening across the Desert Southwest. Additional rainfall is likely
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 reports of rain and snow will likely be needed later this


AZ...Winter Storm Warning from midnight tonight to 11 AM MST Saturday
     for AZZ024.



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