Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 291259

Area Forecast Discussion
National Weather Service Phoenix AZ
559 AM MST Wed Mar 29 2017

.UPDATE...Updated Aviation and Fire Weather discussions.


High pressure building across the Desert Southwest will result in
a warming trend through Thursday. A strong low pressure system
will then produce windy conditions Thursday along with much cooler
temperatures Friday. Scattered precipitation is possible across
the higher terrain of eastern Arizona Saturday as the storm
lingers. Warmer conditions will then return Sunday as high
pressure again builds across the region.


Overall weather pattern will remain transitory with several
similar systems affecting the Desert Southwest through next week.
Latest streamline analysis shows a broad ridge building in across
the California coast in the wake of the departing upper low
across New Mexico. Thickness rises will translate into a warming
trend through Thursday, with above normal temperatures expected.

A Pacific low pressure system dropping into the Great Basin will
strengthen, ultimately closing off across Utah Thursday evening.
Windy conditions will develop ahead of this low during the
afternoon and evening with the latest NAEFS percentiles indicating
speeds widespread above the 90th percentile and even approaching
the 99th percentile in some spots. A significant cooldown is
expected Friday as the low drifts towards the Four Corners with
high temperatures struggling to reach the lower 70s in the lower

Not unlike the last upper low, the next one will also likely feature
a vort max slowing the progression of the low, which will generate
ascent across eastern Arizona Saturday. Latest models including
the CAMs suggest some potential for scattered shower activity
during the afternoon mainly across eastern Arizona, though Lifted
Indices generally remain unimpressive south of the Mogollon Rim.

Temperatures will rebound quickly Sunday as another positively-
oriented Pacific ridge builds eastward. Earlier runs of the GFS
and ECMWF were quite divergent for early next week, however the
most recent runs have come into much better agreement. Latest
forecast generally reflects a blend of the multi-model ensemble,
which suggests yet another weaker low pressure system will pass by
to our north Monday. Subtle cooling behind this trough Tuesday
will then again be supplanted by another ridge and subsequent
warming Wednesday.


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

We are currently on the backside of an exiting upper level low
pressure system which will give our diurnal winds a more
northerly component today. A few high clouds at 20-25 kft may
pass overhead late this afternoon but will not be of any concern.
Northwesterly winds look like they will pickup earlier than usual
today and will slowly back to westerly by the evening hours.

Southeast California/Southwest Arizona including KIPL and KBLH:

North to northwesterly flow will continue as an upper level low
exits the area. Gusts up to 20 kts may be observed at KBLH this
morning and early afternoon before diminishing. A few high clouds
today otherwise the north to northwesterly flow will switch
slightly to westerly this evening.

Aviation discussion not updated for amended TAFs.


Friday through Tuesday: The weather pattern will remain relatively
active across the Desert Southwest through early next week, though
in general precipitation is not expected. Only exception will be in
the higher terrain well north and east of Phoenix. On Friday, below
normal temperatures are expected as a low pressure system moves
through which may bring locally breezy winds. High temperatures
rebound on Saturday to near normal although breezy winds are
expected once again in SE California and far western Arizona as
the low pressure system exits our area. Thereafter, high pressure
will follow for Sunday and Monday, resulting in a warming trend
and a return to above normal temperatures with relatively light
winds. Another passing dry low pressure system may affect our area
on Monday which should bring another round of breezy winds.


Spotters should follow standard reporting procedures this week.


CA...Wind Advisory from 2 PM Thursday to 5 AM PDT Friday for CAZ030.



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