Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 230416
AFDPSR

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

.SYNOPSIS...
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.

&&

.DISCUSSION...
Surface front is tracking across the CWA this evening -- evident
in the combo of strong gusty winds and pressure rises at the
surface in addition to the leading ML cirrus band on IR imagery
loops. Winds along and in the wake of the front were quite strong
this afternoon across SE CA and along the International Border,
where El Centro NAS and the Mexicali Airport gusted near 40 mph
for a few hour window with current sustained wind speeds still
elevated 15-20kts. Blowing dust is currently reported at MMML with
vsbys down around 1SM. As such, added mention of patchy blowing
dust through 06z/10pm PST along the I-8 corridor. Included patchy
blowing dust eastward into portions of Yuma county as well
although given the weekend`s rainfall, the threat for any
additional dust pick-up looks low. Westerly surface winds will
increase for the western and south-central AZ deserts overnight
with FROPA with some periodic gusts cresting 20-25mph. Much cooler
airmass advection still in store for tomorrow, dropping high
temperature forecasts 10 to 12 degrees with clearing skies and
continued dry conditions.

&&

.PREVIOUS DISCUSSION /Issued at 250 PM MST/...

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
expected.

&&

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

Dry surface front will move through the Phoenix area overnight,
promoting west directions to hold overnight. Current timing of the
surface front brings it through the terminals 06-08z window with
some gusts of 20-25kts possible. Mid and high level cirrus will
thin towards Thursday morning, with some limited FEW-SCT decks
20kft or higher lingering. Again, west winds will likely hold
overnight but main wane in speeds and become light/variable
towards sunrise but west winds will remain prominent just off the
surface.

Southeast California/Southwest Arizona including KIPL and KBLH:

In the wake of a potent cold front, strong westerly winds and
mountain waves (for KIPL/KNJK especially) will be possible
overnight. Sustained winds 15-25kts with periodic gusts near 30kts
will gradually weaken overnight but west to northwest winds will
persist into Thursday AM. Speeds will hold 8-12kts with mostly
clear skies.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
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.

&&

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

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

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DISCUSSION...Nolte
PREVIOUS DISCUSSION...Vasquez
AVIATION...Nolte
FIRE WEATHER...Rogers



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