Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 222231
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
331 PM MST Sun Jan 22 2017

.UPDATE...
Updated Aviation section.

&&

.SYNOPSIS...
Another Pacific storm will approach the area tonight. Increasing
clouds are expected, with a chance of showers over portions of
southeast California, spreading east across the remainder of
southern Arizona later tonight and Monday. Snow levels Monday
afternoon and night will fall to between 5 and 6 thousand feet.
After the cold front Monday, a drier and much colder airmass will
settle over the region Tuesday through Thursday, resulting in some
of the coldest low temperatures of the year. Clear skies with a
warming trend will return next Friday through Sunday.

&&

.DISCUSSION...

Tonight through Monday night...

Another Pacific storm is forecast to move into the region later
tonight through Monday night. Although rain shadow effects downwind
from the coastal mountains may limit precip over our southeast CA
zones, much higher amounts are expected in south central AZ
generally from Phoenix north through east. Of particular note, the
last several GFS model runs are forecasting higher amounts of low
level frontal band moisture upslope into south central AZ. Rainfall
amounts in the area from Phoenix north through east, especially in
the foothills and mountains, will range from 0.50 to 0.80 inches,
enough to renew flooding of deserts washes draining from the higher
elevations. Yesterday there were several water rescues, and washes
are still running this afternoon over a large part of northern
Maricopa and southern Gila Counties.  Since soil moisture is
saturated, we have decided to issue a Flash Flood Watch for the
above counties from Monday afternoon through Monday night.

Additionally, snow levels will remain rather high initially, but
dramatically fall with the cold front Monday afternoon and night.
Since most precip will fall early as rain, snowfall in the 2 to 5
inch range is possible in southern Gila County above 6000 feet. A
Winter Weather Advisory is posted for southern Gila County on Monday.
Showers generally decrease considerably by late Monday night and
early Tuesday morning.

Tuesday through Thursday...

After the cold front, some of the coldest temperatures of the season
are forecast to settle over the region Tuesday through Thursday. Low
temperatures Tuesday and Wednesday nights will likely fall into the
low to mid 30s on the deserts, but not cold enough yet for a Freeze
Warning.  Clearing skies are also expected.

Friday through Sunday...

Mostly clear skies with a slow warming trend is forecast this
period. Afternoon temperatures will finally approach season norms by
next Sunday.

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA,and KSDL:
Southeast surface winds will continue through about 12-15Z Monday
before things start to change as a cold front moves across the area
later in the morning. Surface winds will strengthen and become
southwesterly with the frontal passage. Ceilings with bases AOA 8-10
kft MSL will continue through about 09Z before trending lower and
possibly touching MVFR for a short period with the frontal passage.
Higher mountains obscured.

Southeast California/Southwest Arizona including KIPL and KBLH:
Light surface winds will strengthen this evening becoming mostly
southerly through 06Z-10Z Monday before things start to change as a
cold front moves across the area late tonight. Surface winds will
strengthen further with gusts of 20-30 kts and become southwesterly
with the frontal passage. Ceilings with bases AOA 7-9 kft MSL will
continue through about 03-06Z before trending lower and possibly
touching MVFR for a short period with the frontal passage. Higher
mountain tops obscured.


Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday: Weakened but broad and dry troughing will
settle over the west Tuesday and Wednesday keeping flow aloft
westerly. Additional weak shortwaves may move on-shore over southern
CA but fall apart before reaching the districts in southeast CA.
Quasi-zonal flow will develop into the region as high pressure
attempts to build into the west and various shortwave systems ride
over the ridge flow. Temperatures will stay at or below seasonal
normals as minimum humidities gradually dry into the 20 to 40 percent
range through the week. One stronger storm system passing through the
Four Corners during the late week/early weekend will produce enhanced
easterly surface flow over the Mogollon Rim and northerly flow down
the Colorado River Valley, introducing breeziness and periodic
gustiness from the north and northeast for the districts.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Winter Weather Advisory from 1 PM Monday to 5 AM MST Tuesday for
     AZZ024.

     Flash Flood Watch from Monday morning through Monday evening for
     AZZ021>024.

CA...None.
&&

$$

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DISCUSSION...Vasquez
AVIATION...AJ
FIRE WEATHER...Nolte



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