Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 271045
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
345 AM MST Mon Mar 27 2017

.SYNOPSIS...
Another Pacific cold front is expected to affect the region from
Monday afternoon into Tuesday. This system will bring shower chances
to the higher terrain of South-Central AZ, along with gusty winds
across the entire region. The strongest winds, along with areas
of blowing dust are forecast to develop over portions of southwest
AZ and Southeast CA. High pressure will then redevelop across the
region Wednesday and most of Thursday, ahead of another weather
system than is expected to move into the Desert Southwest on
Friday and Saturday.

&&

.DISCUSSION...

Mostly clear skies across our CWA this morning as our area sits
under a weak short wave ridge with a fast approaching trough to
our west. This is clearly seen in GOES water vapor imagery. IR
satellite indicates some high and mid level clouds beginning to
develop on the leading edge of the trough over portions of
Southern California. These clouds will continue to advance
eastward throughout the day today as the trough pushes inland.

Since moisture is rather limited with this system, we are
expecting very little, if any precipitation across our area on
Monday. A very slight chance is possible for elevated portions of
Gila county late this afternoon where the system`s dynamics
combined with the westerly orographic flow could squeeze out a few
drops. However, the main impact with this system will be winds.
Surface westerly winds will gradually increase across our area on
Monday with the strongest winds focused in SE California.
Additionally, as the winds strengthen across SE California during
Monday afternoon, isolated pockets of blowing dust and sand are
possible.

Early Tuesday, the system gradually moves eastward and digs
deeper across our area. This will position us under the dryer
backside of the trough which will gradually turn winds from
westerly to more northerly. During this period, winds are expected
to gust up to 50 mph across Joshua Tree National Park, especially
across the wind prone locations, and up to 40 mph across the
lower portions of the Colorado River Valley. This will very
likely kick up dust and sand and cause reduced visibilities on the
roadway, not to mention the strong cross wind creating difficult
driving conditions across I-10.

The system slowly moves eastward Tuesday night and winds
diminish. Models are in fairly good agreement of a transient
ridge building over the area Wednesday into Thursday which is
forecast to push our temperatures back into the upper 80s across
the Phoenix area. However, models show yet another trough diving
down from the Pacific Northwest and into our are on Friday. This
will cause a rather sharp cooling trend into Friday with highs at
least 10 degrees cooler than Thursday. While the details are still
uncertain, the system does look cooler than the one expected
Monday/Tuesday and precipitation amounts do look rather slim again.
As with all these passing upper level troughs, this one looks to
kick up surface winds again.

&&

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

Weak short wave ridge to move east across the area tonight into
Monday allowing increasing mid/high clouds to spread into the
greater Phoenix area. Expect SCt-BKN decks aoa 20k feet after
midnight with some mid cloud decks down to around 10-12k feet by
Monday morning. Winds next 24 hours should be mostly below 12kt
following typical diurnal trends with potential for some
afternoon/evening gusts Monday to 18kt or so ahead of an approaching
upper low.

Southeast California/Southwest Arizona including KIPL and KBLH:

As an upper low approaches tonight into Monday, an increase in
mainly high cloud is expected with SCT to BKN decks aoa 20k feet
along with some mid decks down to 10-12k feet. After 18z or so
Monday skies should become genly clear. Wind will become an issue
later Monday especially at KIPL as gradients tighten; mostly west
winds less than 12 kt at KIPL thru Monday morning then increasing
quite a bit during the afternoon with peak gusts over 25kt possible
by 20z. A bit less wind at KBLH but similar trends/tendencies. Gusts
in the afternoon/evening could generate some blowing dust/sand but
vsbys should stay above 6 SM for the most part; confidence rather low
that restricted vsbys will be seen at the TAF sites.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday...
Active storm pattern will remain over the Intermountain West at
least through the end of the month and possibly into early April
as a series of Pacific storms pass through. Breezy weather will
remain a common feature of most afternoons/early evenings for the
districts with daytime humidity levels ranging 10-25 percent at
their driest. With an active storm track over the area,
temperatures will trend more towards seasonal averages. Periods of
stronger winds in combination with drier air working into portions
of the area may lead to a locally elevated fire danger/critical
fire weather conditions for some locales Tuesday and again on
Friday as another storm transitions in. A fair bit of uncertainty
remains with the track of the next few systems to move through
the region in the far extended period that may ramp up or back off
concerns for elevated/critical fire danger.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters are encouraged to follow reporting procedures with
criteria reports this week.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Wind Advisory from 3 AM to 4 PM MST Tuesday for AZZ020-021-026.

CA...Wind Advisory from 7 PM this evening to 4 PM PDT Tuesday for
     CAZ030>033.

&&

$$

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DISCUSSION...Wilson
AVIATION...CB
FIRE WEATHER...Nolte


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