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000
FXUS65 KPSR 260941
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
245 AM MST Mon Jun 26 2017

.Update...Aviation and Fire Weather Discussions.

&&

.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...
A resurgence of the high pressure system over the Southwest U.S.
this past weekend led to a continuation of the very hot
temperatures across the region. Fortunately, this high pressure
will begin to get squashed today as a weak shortwave trough moves
through northern California. 500mb heights will lower slightly
from yesterday and highs this afternoon will drop a few degrees,
but the Excessive Heat Warning remains in effect into this
evening.

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. Increasing winds aloft will mix down to the
surface resulting in gusty west to southwest winds during the
afternoon and evening hours. Through 20z Mon, light south to
southeast winds under 7 knots. Clear skies.  From 20z Mon through
03z Tue, increasing west to southwest winds 10 to 15 knots with
gusts to 25. Clear skies.


Southeast California/Southwest Arizona including KIPL and KBLH:

A series of weak Pacific weather systems will move into the western
states north of AZ. Increasing winds aloft will mix down to the
surface resulting in breezy west to southwest winds during the
afternoon and evening hours. Through 21z Mon, light and variable
winds under 6 knots. Clear skies. From 21z Mon to 03z Tue,
increasing southwest winds 10 to 15 knots. Gusts to 25 knots
vicinity 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...Kuhlman
AVIATION...Vasquez
FIRE WEATHER...Vasquez