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fxus65 kpsr 300101 

Area forecast discussion
National Weather Service Phoenix Arizona
601 PM MST Wed Mar 29 2017

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.


a fast moving deepening upper level trough will approach our
region from the northwest on Thursday and latest forecast guidance
shows a better threat of strong winds across southeast California
Thursday afternoon into early Thursday night. As a result, the
Wind Advisory has been adjusted to include Imperial County. The
strong westerly winds will develop early Thursday afternoon with
winds peaking late afternoon into early evening.

For tonight, clear to mostly clear skies and near normal
overnight lows are expected ahead of the approaching trough. The
rest of the forecast for tonight and Thursday still looks to be
in good shape.


Previous discussion...
a very pleasant day weather-wise has taken shape, as temperatures
are in the low-mid 80s f amidst mostly clear skies and generally
light winds. However, a pattern change is underway across the
western U.S. As a seasonably strong upper low deepens across the
western Great Basin overnight into tomorrow. The primary effect
from this system will be strengthening westerly winds beginning
early Thursday, spreading into central Arizona by Thursday
evening. In fact, naefs 850-mb wind speeds are forecast to reach
or exceed the 99th percentile tomorrow afternoon and evening
(30-40 kts) immediately ahead of an associated cold front sweeping
through the area. As a result, have expanded the Wind Advisory to
include most of eastern Riverside County beginning tomorrow
afternoon into the overnight hours, where confidence is highest
for the strongest advisory-level wind speeds to occur.

Otherwise, the other primary change will be much cooler
temperatures occurring Friday in the wake of the cold front.
Highs in the low 70s will be 5-10 degrees below normal as the
upper trough cuts off and decelerates near The Four Corners.
Precipitation chances will be quite limited given meager moisture
associated with this system, and the strongest forcing for ascent
remaining north and east of the Phoenix area. Only slight chances
for precipitation will be maintained across southern Gila County
for Saturday.

The upper low will gradually weaken and shift eastward this
weekend, and will allow for another short-lived warming trend to
take hold into early next week as transitory midlevel ridging
builds across the southwest. Another storm system will develop
across the western Continental U.S. Monday and Tuesday, and send a weak cold
front across the region. However, moisture will remain limited,
with the primary effects being increased wind speeds and a modest
cooling trend by Tuesday.


south-central Arizona including kphx, kiwa, and ksdl:

Westerly winds will gradually diminish this evening with a switch
over to downslope easterlies sometime late this evening to around
midnight. Skies to remain clear to mostly clear with only high
cirrus from time to time. Westerly winds will again become breezy
Thursday afternoon with gusts to around 20 kts.

Southeast California/southwest Arizona including kipl and kblh:

Generally light westerly winds tonight under mostly clear skies.
An approaching low pressure system will allow for increasing winds
on Thursday with westerly winds gusting up to 30 kts by late in
the afternoon. These strong westerly winds may lead to some patchy
blowing dust which could impact kipl or kblh. Not enough
confidence in blowing dust occurrence at this time to include in

Aviation discussion not updated for amended tafs.


Fire weather...
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 southeast 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.


Spotter information statement...
spotters should follow Standard reporting procedures this week.


Psr watches/warnings/advisories...
California...Wind Advisory from 2 PM Thursday to 4 am PDT Friday for caz030-

Wind Advisory from 2 PM to 11 PM PDT Thursday for caz033.



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