Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 260453

Area Forecast Discussion
National Weather Service Phoenix AZ
953 PM MST Fri May 25 2018

.UPDATE...Updated aviation discussion.


Near normal temperatures and dry weather will persist over the
region through the holiday weekend, though the afternoons will be
a bit breezy through Saturday. Temperatures will trend upward
Sunday through Tuesday, with most lower desert areas topping out
in the 100 to 105 range. The warm temperatures will remain through
the work week.


A closed low centered just west of San Francisco continues to
slowly rotate eastward this afternoon, readily seen on any
infrared satellite product focused on the Western US. For our
forecast area, we are firmly under a dry southwest flow.
Precipitable water values are generally around 1/4 to 1/2 inch,
which is fairly typical for the late spring across the Southwest.
Temperatures will peak at values also fairly typical for this time
of year.

The closed low will continue moving east the next two days as it
gradually fills. Most notable impacts to our area will be a modest
decrease in temperatures and a slight uptick in afternoon winds
(primarily Saturday). Mass fields are not expected to
substantially deviate from climatological norms, so not expecting
the cool down or winds to be very significant. That said, winds
across southeast California will likely be high enough to agitate
surface sand/dust and create areas of reduced visibility. Based on
past few wind systems, the recreation areas of western Imperial
County are likely source regions and areas to the east would be

Sunday through Tuesday will see a warming trend, as the low moves
out and thermal profiles rebound under an expanding anti-cyclone
centered over northern Mexico. We did lower temperatures just a
bit from previous forecasts as thermal fields from the GEFS are
struggling to breach the 90th percentile values. Still, widespread
highs in the lower 100s will be common from Memorial Day through
Friday. This will put most of the lower desert areas into the
moderate HeatRisk category.

We could see a bit more cooling and a return of breezy conditions
toward the end of the week and into next weekend as the GEFS is
suggesting another trough will move toward the West Coast. Given
the pattern of the past few weeks, would not be surprised to see
that trend continue.


South-Central Arizona including KPHX, KIWA, and KSDL:
West wind will persist late into Saturday morning at KPHX and
KIWA, although speeds have come down late this evening. Still
questionable if/how long east winds will materialize at KPHX, but
should see several hours of weaker and more variable winds after
11Z. Higher confidence in easterly winds developing across KIWA
after 09Z. Typical west-southwest winds will develop tomorrow
amidst periods of scattered high clouds, with no aviation weather
concerns anticipated.

Southeast California/Southwest Arizona including KIPL and KBLH:
Gusty winds are likely to continue at KIPL through around 07Z,
before weakening across southeast California. Gusty west winds are
possible once again Saturday, but speeds should be around 5-8 kt
weaker than Friday. Lighter winds anticipated at KBLH, generally
below 12 kt, although a few gusts to around 18 kt will be possible
Saturday afternoon.

Aviation Discussion not updated for amended TAFs.


Monday through Friday:
Very dry conditions will continue to prevail next week with no
sign of substantial moisture anytime in the near future.
Temperatures will become seasonably warm with highs some 5F or so
above average. Afternoon minimum humidity levels will mainly be in
a 5-15% range with poor to fair overnight recovery. Winds will
become somewhat stronger Wednesday and Thursday with the passage
of a weather disturbance to the north of the districts; and gusts
25 to 30 mph will be possible in the more wind prone areas.
Otherwise, winds will be very typical for late May the remainder
of the week.


Spotter activation will not be needed.




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