Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 222147

Area Forecast Discussion
National Weather Service Phoenix AZ
250 PM MST Wed Feb 22 2017

A dry cold front will move through the region this evening and will
bring much cooler afternoon temperatures to the area Thursday and
Friday. Slightly warmer weather is expected Saturday, however a
couple of Pacific storms are forecast to move into the region Sunday
morning and again Monday. The Monday weather system will be the
wettest, spreading a good chance of rain mainly across parts of
southwest and south central Arizona. A dry but cool airmass will
follow by the middle of next week.



Tonight through Saturday...

A relatively dry cold front was approaching AZ from the west this
afternoon. Considerable high clouds were spreading across our
forecast area, southeast CA to south central AZ ahead of the front,
and should continue through the evening hours. The dry cold front
will probably move through the Colorado River Valley around 5 pm
mst, then through the greater Phoenix area just after midnight. In
the wake of the cold front, much cooler below normal temperatures
are expected Thursday and Friday. A slightly warmer afternoon will
develop Saturday.

Sunday and Monday...

A couple of Pacific storms are forecast to move into the region this
period, one Sunday morning and a much wetter one Monday.

The early Sunday weather system will be much colder, but most
dynamics and moisture will be confined to the northern Half of AZ,
mainly north of Phoenix. However enough moisture with frontal zone
should provide a slight chance of showers over the mountains
northwest through east of Phoenix, especially southern Gila County.

The weather system for Monday will actually be the merger of two
disturbances, one from the Pacific northwest, and one coming in from
north of Hawaii. Needless to say it will be a wetter storm, with
most precip expected to fall east of the Colorado River, and
especially in the vicinity of the mountains and deserts near
Phoenix. Strong westerly winds on Monday should enhance the rain
shadow effects in southeast CA, namely the Imperial Valley and areas
west of the Colorado River. Much colder temperatures are also
forecast for Monday.

Tuesday and Wednesday...

Dry cool west to northwest flow aloft will follow this period.
Mostly clear skies are forecast with below normal temperatures


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

High-Res model output continues to show isolated-scattered
showers/thunderstorms developing over the eastern portions of the
Greater Phoenix area through about mid-morning today as the upper
low that has brought the moisture to the region moves off to the
south and east. However, confidence on any shower activity actually
affecting a particular terminal is not high enough at this time to
include anything more than VCSH in the TAFs. Cigs could briefly dip
as low as 8k feet in any showers that do develop, but should remain,
for the most part, aoa 10k feet. Cigs/shower chances to lift/end
this afternoon and evening as the upper low moves off well to the
east. Winds to remain easterly until late afternoon, then briefly
shift to light westerly to northwesterly during the late
afternoon/early evening hours before reverting back to easterly
direction during the mid-late evening hours.

Southeast California/Southwest Arizona including KIPL and KBLH:

High pressure building into the region to bring mainly clear skies
to both KIPL and KBLH through most of the taf period, with perhaps a
bit of high cirrus moving into the region late tonight. Winds to
remain mainly out of a westerly to northwesterly direction at KIPL
and out of a northerly direction at KBLH through the taf period,
with speeds mainly aob 12 kts.

Aviation Discussion not updated for amended TAFs.


Friday through Tuesday...Dry conditions are expected for most
areas through early Sunday. Near-normal temperatures are expected
on Saturday and Sunday with humidity values bottoming out in the
15-25 percent range each day. Winds will be light amidst high
pressure over the region. Strengthening of westerly winds will
occur Sunday across southeast California ahead of a storm system.
Precipitation chances will also increase late Sunday into Monday
across the forecast area, especially over the higher terrain of
south-central Arizona, but precipitation totals are forecast to be
light. Winds will strengthen again on Monday especially across
southeast California and southwest Arizona, but this will also
coincide with an increase in humidity values, which should
mitigate fire weather concerns.


Spotters should follow standard reporting procedures.




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