Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 240306

Area Forecast Discussion
National Weather Service Phoenix AZ
805 PM MST Wed Aug 23 2017

Increased moisture levels and storm chances will linger into
Thursday across central and eastern Arizona before decreasing
heading into the weekend. With very minimal storm chances after
Thursday, temperatures will remain above normal through the next


A series of shortwaves (some convectively enhanced) in southwest
flow aloft have invigorated scattered to numerous convective
clusters over southern and eastern Arizona, as well as western New
Mexico. With earlier DCape values approaching 2000 J/kg, several
long lasting outflow boundaries have been washing across the lower
elevations of southern Arizona bringing areas of blowing dust into
Pinal and Maricopa counties. Despite several colliding boundaries
over the metro, renewed convective development has been limited to
absent this evening.

00Z KPSR sounding data sampled fairly low 9 g/kg boundary layer
mixing ratios, though this moisture did extend all the way to the H7
level yielding only 25 J/kg cinH. It may take the combination of
outflow and terrain features to break this inhibition and a few
showers on the outskirts of town for the remainder of the evening
looks probable. Otherwise, made some various minor adjustments to
account for moisture behind outflows and winds, but also larger
revisions to overnight lows given the combination of persistent
winds, increased moisture, and cloud cover.


/137 PM MST Wed Aug 23 2017/
Already by Thursday, the trough lifting to the northeast will
begin to beat back the lower level moisture. Mixing ratios in the
1000-700 mb level will thin to around 9 g/kg by the afternoon,
which is reflected in decreasing instability parameters.
Precipitation chances will remain but will be on the downward

Heading into the weekend, a broad anti-cyclone gradually develops
across the western states, with the maximum height anomalies
situations over the PacNW. Locally, our temperatures will increase
as any chances for rain greatly diminish. HeatRisk values will
broadly climb into the moderate range, meaning the heat will be an
issue for at-risk folks. We`re unlikely to reach the high category
unless forecast temperatures increase by several degrees.

Early next week, appears a backdoor front will push through New
Mexico and into Arizona. This pattern can bring us some
precipitation (primarily through a northeast steering flow to help
propagate convection off the Rim) but not really the most ideal,
especially as we`d be recycling moisture from the Four Corners
area. It should be enough to bring our temperatures down just a
few degrees.


South-Central Arizona including KPHX, KIWA, and KSDL:
Outflow boundaries and wind shifts will continue to be the primary
concerns this evening and overnight, though a predominant southeast
wind should prevail as restrictions from dust improve. An isold TSRA
could be possible around Phoenix into the early morning though
coverage and probabilities are far too remote to include in the TAF
package. Otherwise, east winds should prevail much later into the
afternoon Thursday than is typical with little to no chance of
storms after Thursday morning.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns under mostly clear skies through Thursday
afternoon. Sfc winds will favor a S/SW component and could
approach 15-20kt at times.

Aviation discussion not updated for amended TAFs.


Saturday through Wednesday:
Monsoon activity over the forecast area through next Wednesday will
be somewhat sparse. Storm chances will stay confined to the higher
terrain areas east of Phoenix through Sunday before moisture starts
to work back towards the west, bringing a slight chance of
thunderstorms to the south-central deserts by Monday. Humidities
will stay somewhat low each day with minimum RH values mostly
between 12 and 20 percent each day. Apart from thunderstorms, winds
will tend to follow familiar warm season patterns. In addition,
temperatures will stay above normal each day, especially over the
weekend when hotter western deserts should reach to 110 degrees.


Spotters should follow standard reporting procedures.





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