Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 270504 AAA

Area Forecast Discussion
National Weather Service Phoenix AZ
1005 PM MST WED OCT 26 2016

.UPDATE...Updated aviation discussion.


Strong high pressure building over the region will lead to warming
temperatures through the end of this week with record highs possible
at some locations on Thursday. A slight cool down will occur for the
weekend and early next week, but temperatures will still remain well
above normal and the dry weather will continue for the majority of
the region.


A mild and dry evening, finishing off yet another very warm dry
across our cwa. Phoenix Sky Harbor recorded a high of 96, which was
only 2 degrees shy of the record of 98, set in 2001. Although clear
skies and a rather dry airmass will allow for decent radiational
cooling tonight, the very warm airmass will still keep our nighttime
lows well above normal, with the current forecast low of 71 at Sky
Harbor being a full 10 degrees above normal, and would, if is
verifies, also tie the record high min for the date. Outside of some
minor edits to the hourly temp/dewpoint grids to better reflect
current trends, inherited forecasts look to be in good shape, and no
updates are planned.


Latest streamline analysis shows an anticyclone in the eastern
Pacific with a ridge axis extending northward through Sonora and into
the Desert Southwest. Main forecast impact remains the anomalous heat
forecast for tomorrow.

Global models are indicating copious amounts of upper-level moisture
will be transported into Southwest in the return flow around the
eastward-advancing ridge. Latest simulated satellite imagery from the
NCAR ensemble suggests increasing high clouds will temper the heat
somewhat, particularly across southwestern Arizona and southeastern
California. Minor adjustments were made to the high temperatures in
these areas. Nevertheless, forecast high of 98 degrees in Phoenix
would tie the record for the date. Upper percentiles of the raw and
post-processed guidance also indicate that there is a low probability
of reaching 100 degrees, which would set a new mark for the latest
100 degree reading on record.


By Thursday night, an Pacific low pressure trough reaches the
California coast helping to displace the upper level ridge eastward
over New Mexico and Texas. The track of this Pacific low still keeps
the majority of the dynamics and moisture out of our area, but we
can`t rule out a few showers across southeast California on Friday
with best chances over JTNP. This trough will drop our heights aloft
(500mb heights of 582-585dm), leading to a 2-5 degree drop in highs
for Friday. Dry southwesterly flow with little change in temperatures
is shown into Saturday.

A deep northern Pacific trough dips southward down the West Coast
Saturday night into Sunday before moving into Oregon and northern
California later Sunday. As with the previous trough, this one should
mostly miss us to the northwest, but a slight chance of showers will
exist on Sunday mainly over JTNP. Little change in the jet stream
pattern is seen for early next week keeping any potential weather
systems to our north. The dry southwesterly flow should keep us under
mostly clear skies with temperatures near to a few degrees above
normal for next Monday-Wednesday.


.AVIATION...South-Central Arizona including KPHX, KIWA, and
KSDL. Southeast California/Southwest Arizona including KIPL and KBLH:

High pressure at the surface and aloft along with weak sfc pressure
gradients to keep skies mainly clear and winds very much on the
light side through the taf period (mainly 6 kts or less). Wind
directions to mainly follow typical diurnal trends, with extended
periods of light/variable winds likely to occur as well.

Aviation discussion not updated for amended TAFs.


Saturday through Wednesday...

Two Pacific weather systems will brush the Desert Southwest Friday
through Sunday. The tracks of these systems will keep the majority
of the moisture out of our area; however, a few showers across
southeast California cannot be ruled out on Saturday or Sunday,
mainly over JTNP. These weather systems will also bring cooler
temperatures in the lower deserts, with high temperatures gradually
falling from the the low to mid 90s on Saturday down into the upper
80s by Tuesday.

Minimum humidities will remain near the 20 to 30 percent range each
day with good overnight recoveries. Winds will remain light and
follow normal diurnal headings through the entire period, except for
some periods of afternoon breeziness up to 20 mph in southeast
California Sunday through Tuesday.


Spotter activation will not be needed this week.




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