Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 290352
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
850 PM MST Wed Jun 28 2017

.SYNOPSIS...
A dry airmass will remain over the region through the rest of the
week with temperatures moderating closer to average. Though high
temperatures will finally drop below 110 degrees, readings will
still end up in a slightly above normal range through early next
week. Skies will remain mostly clear as the monsoon wind pattern
has yet to be established and storm activity will stay well south
across Mexico.

&&

.DISCUSSION...
Upper high continued to be centered over far southern AZ with
relatively strong upper troffing across the northern tier of states.
This is keeping a dry westerly flow aloft going over most of
Arizona, and the latest IR imagery showed clear skies area-wide. 00Z
raobs showed the strong westerly flow aloft, especially at Flagstaff
where PWAT dropped to 0.26 inches. Expect continued clear skies
overnight along with relatively light winds and relatively mild
overnight low temps. No updates needed to the forecast at this time.

.PREVIOUS DISCUSSION...
The center of the subtropical ridge remains south of the region
with large scale troughing pushing across the Pacific Northwest
and the Great Basin. This is resulting in enhanced dry west to
southwesterly flow aloft and a significant decrease in 500 mb
heights. The dry air advection was very evident on this mornings
12Z Phoenix sounding, where PWAT values were .65 inches less than
Monday`s sounding. High temperatures will finally stay below 110
degrees over many desert locations today and these "cooler"
temperatures will continue through the rest of the week. In
addition, dry air and clear skies will lead to decent radiational
cooling overnight. This will allow temperatures to drop into the
70s over many desert locations with the exception of central parts
of Phoenix which will be a few degrees warmer due to the "urban
heat island."

Later this week, 500mb heights do begin to increase a bit as the
troughing to our north shifts over the central and eastern U.S.
After highs just below 110 through Friday, we should see a couple
degrees of warming on Saturday with the higher heights resulting
in highs around 110. Although 500mb heights stabilize this weekend
near 592dm and stay there into early next week, a slight boost in
low level moisture (afternoon surface dewpoints 35-40 degrees)
should keep highs just below 110 Sunday through Tuesday. This
moisture uptick will however still be insufficient for any monsoon
activity to be seen across the area as both the GFS and European
are in good agreement keeping low level flow either out of the
west or north through next Wednesday. There are indications we may
manage to see a switch to southeasterly low level flow late next
week which could be enough to bring at least a low grade monsoonal
moisture flow out of northern Mexico.

&&

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

Very little changes expected in the weather pattern as dry westerly
flow aloft will keep skies clear over the next 24 hours. Winds will
continue to follow their typical diurnal trends in the greater
Phoenix area, with locally breezy afternoon/early evening west winds
turning to the east/southeast after midnight and then back towards
the southwest/west in the afternoon. No aviation concerns for at
least the next 24 hours.

Southeast California/Southwest Arizona including KIPL and KBLH:

Dry westerly flow aloft will result in continued clear skies next 24
hours. Winds will favor the south at KBLH with a few gusts over 15kt
possible Thursday afternoon. Winds favoring the west during the late
afternoon and evening at KIPL; a few gusts over 20kt are possible.
Winds may turn towards the southeast however by mid morning and
persist into the mid/late afternoon. Overall, no real aviation
concerns for at least the next 24 hours.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
Saturday through Wednesday:

A very hot and dry weather pattern will persist throughout the
period. MaxT`s will remain very hot and generally range from near
seasonable to above normal values through Wed. In addition, min RH
values will remain mostly in the single digits, or below 15 percent
at the most, throughout the lower deserts. Poor to fair overnight
recoveries should improve to fair beginning Tue. Seasonably breezy
west and southwesterly winds can be expected each afternoon with
gusts of 15-17mph.

&&

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

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

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DISCUSSION...CB
PREVIOUS DISCUSSION...Hernandez/Kuhlman
AVIATION...CB
FIRE WEATHER...Sawtelle



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