Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 261533

Area Forecast Discussion
National Weather Service Phoenix AZ
835 AM MST Sun Mar 26 2017


A fast moving high pressure system will build into the region today
ahead of another Pacific cold front expected Monday afternoon.
Although light winds are expected area-wide today, gusty winds ahead
and after Mondays cold front are expected. The threat of showers
Monday night and Tuesday will be confined to central and eastern
Arizona. High pressure will redevelop Wednesday and most of
Thursday, ahead of another stronger and colder weather system
expected Friday and Saturday.



A break between weather systems this morning across the region. The
combination of clear skies and relative light winds once again allow
overnight los to fall into the mid-40 to mid-50 range across the
lower deserts of south-central AZ, with slightly higher readings
across the lower elevations of SW AZ and SE CA. Shortwave ridging
aloft moving across the region will keep skies mainly clear through
the day today and allow lower desert highs to warm up into the low-
mid 80s this afternoon. For the short-term, outside of some very
minor edits to the hourly grids, inherited forecasts still look
quite good.



Today and Tonight...

A transitory upper level ridge will build over the region today and
tonight resulting in mostly clear skies, light surface wind, and
afternoon temperatures near of slightly above normal.

Monday through Tuesday Night...

Another in a series of Pacific weather systems is forecast to move
into the region Monday afternoon and night. This is a deeper and
colder system, and still a bit moisture starved. The cold front is
expected to move through the Colorado River Valley around 1 pm
Monday, then through Phoenix around 5 pm. Gusty pre and post frontal
surface winds are expected area-wide Monday afternoon and evening,
followed by strong north to northwest winds Tuesday.  The strongest
wind gusts however are forecast for southeast CA and Colorado River
Valley Monday.

Since this system is rather moisture starved, any shower activity
will be associated with the coldest mid level temperatures, near
the system center, and relegated to areas from Phoenix north
through east, especially Tuesday afternoon. Any precip should be
on the light side, with perhaps an isolated mountain thunderstorm
as well.

The Tuesday weather system will exit east into New Mexico Tuesday

Wednesday, Wednesday Night, and most of Thursday...

It now appears these incoming weather systems will be a little more
progressive than earlier thought, therefore another transitory upper
level ridge will move through the region Wednesday through most of
Thursday. And except for a few high clouds, mostly clear skies,
light wind, and slightly above normal afternoon temperatures are
forecast.  The only caveat Thursday will gusty afternoon evening
west winds over southeast CA and Colorado River with another
approaching cold front for Friday.

Friday and Saturday...

All models are in general agreement in developing yet another
Pacific trof over AZ this period. Models however are still
conflicted in the eventual track of this system, which has potential
to be the strongest, coldest, and wettest system in the series.
However big disparities still exist between the models, which are
flip flopping with the storm track through AZ. Forecast confidence
is very low this far out, so precip probabilities will be shaded
toward slight chances across south central AZ, with better potential
in the mountains of southern Gila County zone 24.


The upper level trof over AZ Saturday could possibly move east into
New Mexico Sunday, however confidence is low at this point. We will
keep it dry across the forecast area this period.


South-Central Arizona including KPHX, KIWA, and KSDL:
Southeast California/Southwest Arizona including KIPL and KBLH:

Intrusion of thin high clouds and generally light surface winds
following diurnal headings/trends will develop for the terminals
over the 12z TAF period. The forecast area will fall in between
Pacific weather systems today, with increasing mid level cloud
layers between 18-25kft the most noticeable impact today.

The next Pacific system timed into the Southwest will arrive
Monday into Tuesday and bring much windier conditions. There is
potential for some vsby impacts in blowing dust/sand across
southeast CA and degraded long range visibilities across the
region from lofted dust/sand late Monday and into Tuesday.

Aviation discussion not updated for amended TAFs.


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.


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




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