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Area forecast discussion
National Weather Service Phoenix Arizona
933 PM MST Tue may 22 2018

Update...
updated aviation section.

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Synopsis...
quiet weather is expected across the area through next week with
near normal temperatures and dry conditions forecast. Some
breeziness is possible late this weekend into early next week as a
disturbance passes through northern Arizona, otherwise tranquil
weather will prevail.

&&

Discussion...
early afternoon water vapor imagery reveals a slow moving upper
low over southern Nevada, with a dry slot noted across much of
Arizona. While most of the western Continental U.S. Is seeing some degree of
cloud cover associated with this low, southern Arizona and
southeast California are virtually cloud-free as of 20z. This has
allowed temperatures to rise well into the upper 80's across the
lower deserts. Topping out in the low 90's later today seems more
than reasonable based on trends and incoming model data.

Overall a fairly quiet weather week is in store for the region.
The aforementioned low will drift northward on Wednesday, ushering
in weak ridging, drier air, and less wind. This ridge will remain
in place through the end of the week into the first half of the
weekend, resulting in a steady increase in temps. Friday looks to
be the warmest day of the week with highs creeping up right to
around 100 degrees. Just as temps start to warm up, yet another
upper low is forecast to move onshore and through Nevada Saturday
into Sunday. Much like today's low, this one will also remain well
north of the area. If nothing else it will bring some increased
winds and a slight drop in temperatures (highs retreating back
into the mid 90s) for the Holiday weekend. As the low departs
early next week, look for temps to once again trend upward with
most blended guidance suggesting a return of the 100 degree temps
by Tuesday of next week.

&&

Aviation...
south-central Arizona including kphx, kiwa, and ksdl...
southeast California/southwest Arizona including kipl and kblh:

An upper level low pressure system centered over the Great Basin has
begun to retreat north-northeastward this evening. Aloft (aoa
fl100), this will mean weakening southwesterly flow tonight and
through the day Wednesday. Surface winds will favor southwest and
west directions until 08z-09z before transitioning to familiar
drainage/downvalley patterns. During the day Wednesday, anticipate
similar directional patterns as were observed on Tuesday with
prolonged southeast and south directions lasting well past noon
before trending southwest during the latter part of the afternoon.
Otherwise, clear skies.



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Fire weather...
Friday through tuesday:
dry conditions will prevail across the districts through the
Holiday weekend with temperatures a couple degrees above normal
Thursday and Friday cooling back near normals over the weekend.
Afternoon minimum humidity levels will mostly fall in a 5-10%
range with generally poor overnight recoveries. Wind speeds will
begin to increase Friday across southeast California, then across the
remainder of the districts on Saturday. Wind gusts approaching a
25-30mph range will be possible leading to an elevated fire
danger, particularly on Saturday.

&&

Spotter information statement...
spotter activation will not be needed.

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Psr watches/warnings/advisories...
Arizona...none.
California...none.
&&

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