Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 230311

Area Forecast Discussion
National Weather Service Phoenix AZ
811 PM MST Thu Jun 22 2017

.UPDATE...Updated Aviation Discussion...


Anticipate little change in temperatures Friday as high pressure
remains situated across northern Mexico. Temperatures increase
over the weekend. Storm chances return to the higher terrain as
well. Temperatures start to decline on Monday but still
excessively hot in some areas. Modest additional cooling is
anticipated Tuesday and Wednesday.



Friday through Sunday...
The high will sag southward on Friday and dew points will decline
as well. Anticipate little change in temperatures. Over the
weekend, ridging consolidates over the west and the high
strengthens. Accordingly, temperatures increase at least a few
degrees. Expecting to stay below records but we may be only a few
degrees below the peak values we saw on Tuesday. A complicating
factor will be the return of deeper moisture into Arizona as a
backdoor front pushes against the southern Continental Divide.
However, models are not indicating a major influx that would lead
to widespread storms. Rather, it would be more like what we`ve
seen the past couple days with high-based storms over the favored
higher terrain areas of Arizona sending outflow pretty far afield
to the lower elevations. Unfavorable steering flow will also tend
to prevent storms from getting to the central Arizona deserts
(including metro Phoenix). Anticipate Sunday afternoon/evening
being more active than Saturday.

Monday through Wednesday...
A combination of higher dew points and debris clouds will nudge
temperatures down a bit on Monday. However, a number of locations
will still reach high to very high Heat Risk levels. Thus,
extended the Excessive Heat Warning to Monday for portions of our
forecast area including metro Phoenix. A trough passing to the
north will weaken the ridge leading to a modest cooling trend
Tuesday and Wednesday. Anticipate a decrease in storm activity
over Arizona but not altogether since there will still be some
lingering moisture over the southeast third of the state.


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

A late switch to easterly winds will occur tonight, possibly as
late as 12Z at KPHX, followed by a quick turnaround back to
westerlies late in the morning. Afternoon winds will again
become breezy on Friday with gusts at times around 20 kts. Skies
will generally remain clear with intermittent high clouds.

Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation impacts through Friday as skies remain mostly clear.
Winds will continue to favor a southerly direction with some
afternoon breeziness likely at KBLH.

Aviation discussion not updated for amended TAFs.


Sunday through Thursday:
High pressure will generally remain positioned over the Southwest
through late next week, maintaining above normal temperatures. A
modest increase in moisture will occur next week, but still should
see minimum RH values in the 10-20% range each afternoon. Isolated
thunderstorms are possible each afternoon across the higher
terrain of south-central Arizona, including southern Gila County,
but rainfall amounts will be light. Lightning ignitions remain a
concern given the dry sub-cloud layers, along with gusty outflow
winds. For now, it appears any significant moisture intrusion will
hold off until after the period, maintaining dry fuel conditions



Record highs this week:

Date           Phoenix            Yuma
----           -------            ----
6/23         116 in 1974        116 in 1959
6/24         118 in 1929        120 in 1957
6/25         120 in 1990        119 in 1994
6/26         122 in 1990        122 in 1990


Spotters should follow standard reporting procedures.


AZ...Excessive Heat Warning until 8 PM MST Monday for AZZ530-533-534-

     Excessive Heat Warning until 9 PM MST /9 PM PDT/ Sunday for

     Heat Advisory until 9 PM MST Sunday for AZZ557-558-563.

CA...Excessive Heat Warning until 8 PM PDT Monday for CAZ560-561-563-

     Excessive Heat Warning until 9 PM PDT Sunday for CAZ562-564-565.



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