Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 250442

Area Forecast Discussion
National Weather Service Phoenix AZ
942 PM MST Mon Apr 24 2017


A series of mainly dry weather disturbance from the Pacific will
move into the western states the remainder of this week. These
systems will keep afternoon temperatures near or slightly below
normal, along with breezy afternoons. One stronger disturbance on
Friday has the potential to produce a slight chance of afternoon
showers over the eastern Arizona mountains.


A series of upper level disturbances were noted on water vapor
imagery, stretching from the Oregon coast into the central
Rockies. A surrounding belt of broad cyclonic flow and tightening
geopotential height gradient aloft will become positioned across
the Southwest. The primary concern will be the breezy westerly
winds that will occur tomorrow as a dry cold front moves through
the region. The current forecast calls for sustained wind speeds
of 20-25 mph with gusts up to 40 mph. There are some hints in
model guidance that a brief period of stronger winds could occur
near or after sunset, as 0-1 km mean-layer flow increases to 30-35
kt per forecast soundings. Conditions will approach and perhaps
briefly exceed wind advisory criteria, especially between 25/23Z
and 26/03Z.

Otherwise, only minor updates were made to the short-term forecast
this evening, primarily to increase cloud cover across parts of
the forecast area and decrease temperatures slightly to be more in
line with observational trends.



Tonight through Tuesday night...

A series of fast moving Pacific weather systems will continue to
flow through the western states this week, including parts of AZ.
One dry system moved through northern AZ last night and brought a
little cooling this afternoon, with a second and stronger
disturbance expected Tuesday afternoon.

An associated cold front with the Tuesday disturbance is forecast to
move through central AZ including Phoenix during the afternoon
resulting in gusty conditions. Increasing afternoon west to
northwest winds 25 to 35 mph are expected on the south central AZ
deserts including Phoenix, with close to 40 mph in southern Gila
County zone 24. A Red Flag Warning is posted for the south central
AZ deserts Tuesday afternoon/evening.

Other than some high cloudiness at times, dry weather will continue
through Tuesday night.

Wednesday through Saturday...

Several more dry weather disturbances are forecast to move into the
region this period. This will keep temperatures at or slightly below
normal, along with breezy afternoons and evenings. One colder system
Friday will generate a slight chance of showers over the higher
terrain of southern Gila County zone 24, mainly on the San Carlos
Indian Reservation.


South-Central Arizona Including KPHX, KIWA, and KSDL: Winds will
remain generally out of the west overnight and into tomorrow.
Wind gusts will become more frequent and stronger by late morning,
with gusts to 30-35 kt possible after 21Z. A dry cold front will
arrive during late afternoon, and not out of the question to see
gusts exceeding 35 kt between 23-02Z. Will have to monitor for the
potential for an airport weather warning during this period.
Otherwise, thicker high clouds around 25-30 thousand feet should
persist into the morning hours, before becoming more scattered in
coverage during the afternoon.

Southeast California/Southwest Arizona Including KIPL and KBLH:
Westerly wind gusts up to near 20 kts remain possible overnight.
Winds should gradually veer towards a northwesterly direction as a
dry cold front moves through the area. Wind gusts will become less
frequent by afternoon as the cold front shifts east into Arizona.
Thicker upper-level cloud cover will also shift east of the area
by late tomorrow morning.

Aviation discussion not updated for amended TAFs.


Wednesday through Sunday:
Temperatures will continue to hold at or above seasonal averages,
with minimum RH values mostly below 15 percent as dry northwest
flow aloft persists over the area. After Wednesday, a gradual
cooling trend will settle into the region as mostly dry storm
systems sweep through the Great Basin and down through the
Southwest. Outside of a slight chance at some light showers over
high terrain of Gila County Friday into Saturday, widespread dry
weather will cover the districts. Dry afternoons with 5-15% will
be common with overnight humidities varying between mostly fair to
good. Active storm track through the West will keep afternoons
breezy for the district, with upslope west winds and occasional
gusts possible through week`s end.

There will be potential for widespread dangerous fire weather
conditions Friday into Saturday as windy conditions develop across
most of the area - especially south-central Arizona on Friday - and
minimum RH values drop into the single digits across much of the
lower desert. The cooling trend may help mitigate some of the fire
danger potential however but this is something to keep our eyes on
as we move towards the latter part of the week.


Spotter activation will not be needed through the middle of next


AZ...Red Flag Warning from 2 PM to 8 PM MST Tuesday for AZZ132.

CA...Wind Advisory until 7 AM PDT Tuesday for CAZ562-566.



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