Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 210530 AAA
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1032 PM MST Fri Oct 20 2017

.UPDATE...Updated aviation discussion.

&&

.SYNOPSIS...
Gusty winds this afternoon will lead to areas of blowing dust
across parts of southeast California and southwest Arizona. Winds
will decrease into Saturday, except across the lower Colorado
River Valley. Near-normal temperatures will make a brief return
this weekend, before a strong area of high pressure builds over
the Western U.S. This will result in another warming trend with
dry conditions and well above normal temperatures throughout much
of next week.

&&

.DISCUSSION...
Primary concerns in the short term revolve around blowing dust and
strong winds, especially across southwest Arizona and southeast
California. Satellite imagery and observations indicate plumes of
blowing sand and dust have developed across Imperial and Yuma
Counties, with visibilities locally restricted down to one mile.
This is in response to strong westerly flow moving across southern
California into Arizona, supporting gusts of 40-50 mph across the
I-8 corridor primarily from Yuma County westward. Some increase in
west-southwesterly winds has been noted this afternoon across
south-central Arizona, but the best phasing of the strongest flow
aloft with peak heating will remain focused west of the Phoenix
area. The Blowing Dust Advisory, mainly for Imperial and Yuma
Counties, remains in effect until 01Z, while a Wind Advisory
remains in effect until 06Z.

By tomorrow, winds should generally weaken area-wide, except near
the lower Colorado River Valley, where north winds of 15-25 mph
will remain possible. The coolest daytime temperatures in awhile
will also occur in the wake of the fast-moving storm system. High
temperatures in the mid-80s are expected across most lower-desert
locations. Unfortunately, a rapid return to well above-normal
temperatures will occur by Monday, as the large-scale pattern
becomes highly amplified with a ridge building across the Pacific
coast. Temperatures in the mid-upper 90s are expected Monday
through Wednesday.

Longer-range models are now trending towards another pattern change
by next weekend, developing the coldest and most expansive upper
trough of the season across the northern Rockies/northern Plains
into the Four Corners region. This will likely result in a strong
cold front sweeping south-southeastward across the Great Basin,
potentially clipping western/central Arizona and bringing cooler
temperatures by next weekend. With the tight height/pressure
gradients, the degree of cooling and strength of winds over the
Southwest will be sensitive to any longitudinal displacement of the
large- scale features will on, so it is worth watching. Bottom line -
- the well above-normal temperatures don`t look like they`ll last
quite as long as previously advertised. Regardless, precipitation
chances will remain minimal throughout the next week.

&&

.AVIATION...

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

Diminishing winds aloft to allow winds to diminish and revert back
to familiar diurnal patterns through the taf period. Drier air
moving in from the west to allow skies to clear. Reduced slant
visibilities due to lofted dust wafting in from the California
deserts is possible through Saturday morning.

Southeast California/Southwest Arizona including KIPL and KBLH:

Diminishing winds aloft to allow westerly winds that are currently
affecting the region to continue to diminish through the rest of
tonight. Northerly winds at the surface and aloft begin to develop
toward morning Saturday. Expect some moderate gustiness over the
Lower Colorado River Valley after 16Z. Very dry air moving in from
the west to allow skies to pretty much clear completely over the
region.

&&

.FIRE WEATHER...
Monday through Friday: Expect high temperatures to be about 10F
above normal on Monday and Tuesday before a cooling trend takes
place during the latter half of next week. Minimum humidities will
remain below 15% (even at higher terrain locations) and overnight
recovery will be modest. Winds will be light during the first half
of next week except for some minor north and northeasterly
breeziness Tuesday and Wednesday. Some southwesterly breeziness is
possible at times during the latter half of next week.

&&

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

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

&&

$$

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DISCUSSION...Rogers
AVIATION...Percha
FIRE WEATHER...AJ


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