Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 271552
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
850 AM MST Tue Jun 27 2017

.SYNOPSIS...
Drier westerly winds take over across the region through the
weekend with a moderation in temperatures occurring over the next
couple of days. Though high temperatures will finally drop below
110 degrees by Wednesday, highs will still end up near to
slightly above normal through early next week. Skies will remain
mostly clear as any monsoon storm activity stays well south across
northern Mexico.

&&

.DISCUSSION...
A trough axis objectively analyzed through S NV/NW AZ has allowed H5
heights to be depressed by 3-4dm throughout the entire SW Conus per
12Z sounding data. However, the same data shows thermal profiles
through the H8-H7 layer have changed very little in the past 24
hours with weak CAA lagging the trough into central CA/NV.
Therefore, afternoon temperatures will fall near to only a degree or
so cooler than Monday, however deeper westerly flow will allow
mixing of drier air into the boundary layer through the day. Several
adjustments capturing a better temporal forecast trend were made in
this morning update.

&&

.PREVIOUS DISCUSSION...
/300 AM MST Tue Jun 27 2017/
The quiet beginning to the monsoon season looks to remain quiet at
least into early July. As the high pressure system continues to
sag southward, increased westerly dry flow will allow for
substantially drier air to become entrenched over much of the
Desert Southwest through the rest of the week. Surface dew points
have already fallen quite a bit since yesterday and will likely
dip into the teens this afternoon. Temperatures will continue
their slow decline over the next few days with highs bottoming out
between 104-108 on Thursday. The drier air will also allow for
more comfortable overnight lows as readings dip into the 70s
across most of the lower deserts.

Temperatures will creep up a couple degrees Friday into Saturday
as a weak trough moves across California and the Great Basin
resulting in a brief bump in heights aloft over our region. Though
we are not expecting a return of excessive heat, many desert
locations will be flirting with 110 on Saturday. Highs Sunday
should fall back a degree or two and likely stay around or a
couple degrees above normal through early next week.

The forecast becomes a bit more difficult starting early next
week as models are now pointing toward rebuilding the sub-tropical
high somewhere to our east, likely over New Mexico. Between the
weak trough to the west/northwest and the high to the east, our
flow should turn more southerly as early as Sunday, but more
likely either on Monday or Tuesday. This may allow for some
moisture to creep into southeast Arizona at some point, but
models are mainly holding off on showing any appreciable moisture.
So far it does not look promising for any monsoon activity
nearing the lower deserts at least through the middle of next
week.

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL, and
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 gusty west to southwest winds during the
afternoon and evening hours. Through 20z Tue, light and variable
winds under 7 knots. Clear skies. From 20z Tue through 03z Wed,
increasing west to southwest winds 10 to 15 kt with gusts to 25 kt.

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 10 to 20 mph each day.


&&

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

&&

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

$$

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DISCUSSION...MO/Kuhlman
AVIATION...Vasquez
FIRE WEATHER...Vasquez



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