Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 262202
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
302 PM MST Mon Jun 26 2017

&&

.SYNOPSIS...
Hot temperatures will continue today, but some minor cooling will
take place over the next couple days allowing highs to finally
drop below 110 by Wednesday. A series of Pacific weather
disturbances are forecast to move into the western states north of
Arizona Tuesday through Saturday. This will bring drier westerly
winds while keeping the slightly cooler temperatures into the
weekend.

&&

.DISCUSSION...

After 10 days with an Excessive Heat Warning in effect, we have
finally reached the last day. Temperatures will continue to be on
the decline this week as the subtropical high weakens and remains
south of our area.

Over the past week, PW values in Phoenix have increased from .68
inches last Monday, to 1.15 inches this morning. Greatest moisture
remains east and southeast of us, and this is where storm
development has been this afternoon. The steering flow is out of
the west to northwest, so this should keep majority of the
activity away from our forecast area, with a very slight chance
of thunderstorms over the higher terrain of southern Gila County.
The main threats with any storm that does develop, however, will
be gusty outflow winds and brief downpours.

&&

.PREVIOUS DISCUSSION...
A more pronounced trough is set to develop over southern Canada
and the Northern Rockies into the middle part of this week which
will help to push the high pressure further south into Mexico. As
this happens, stronger westerly flow bringing considerable drying
will develop across the Desert Southwest. Temperatures will
gradually lower back to around seasonal normals starting Wednesday
while the drier air completely shifts any thunderstorm activity
well south and east of our area.

The dry westerly flow will continue at least through Saturday and
possibly into Sunday before models indicate a weak trough dipping
into the Desert Southwest early next week. Over the weekend, the
sub-tropical high actually splits shifting one portion over the
eastern Pacific and the other over the Gulf of Mexico. If this
scenario takes place, it will keep the high from reestablishing
over our region and likely keep any monsoon moisture well south
into Mexico into early next week. A dry forecast through around
the 4th of July seems likely for all but far southeastern Arizona.
Temperatures should hover near seasonal normals through early
next week providing a much needed break from the recent extreme
heat.

&&

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

A series of weak Pacific weather systems will move into the western
states north of AZ during the taf period. Increasing winds aloft
will mix down to the surface resulting in gusty west to southwest
winds well into the evening, and overnight hours. The typical shift
to easterly drainage winds is not expected to occur until around
daybreak on Tuesday. Easterly winds to then persist through late
morning on Tuesday, before shifting back to westerly by afternoon,
with gusts as high 28 kts possible by late afternoon on Tuesday.
Drier air aloft to keep skies mainly clear through the taf period.

Southeast California/Southwest Arizona including KIPL and KBLH:

A series of weak Pacific weather systems tracking across the Great
Basin to keep winds going from a westerly direction through the
entire taf period at KIPL and from a southwesterly direction at
KBLH. Winds speeds to diminish at both SE CA taf sites later tonight
and early Tuesday before increasing again on Tuesday afternoon.
Sustained wind speeds at KIPL to rise as high as 25 kts, with gusts
to 35 kts possible during the late afternoon/early evening hours on
Tuesday, with slightly lighter winds expected at KBLH.

Aviation discussion not updated for amended TAFs.


&&

.FIRE WEATHER...

Wednesday through Sunday:

Dry westerly flow aloft over the region will result in clear skies.
Near to slightly above-normal temperatures are expected. Minimum
relative humidity will range from 5 to 8 percent. Good overnight
recovery. Afternoon southwest winds Wednesday and Thursday in the 15
to 25 mph range, decreasing into the 10 to 15 mph range Friday
through Sunday.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST /8 PM PDT/ this evening
     for AZZ530>556-559>562.

     Heat Advisory until 8 PM MST this evening for AZZ557-558.

CA...Excessive Heat Warning until 8 PM PDT this evening for
     CAZ560>570.

&&

$$

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DISCUSSION...Hernandez
PREVIOUS DISCUSSION...Kuhlman
AVIATION...Percha
FIRE WEATHER...Vasquez



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