Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 231237 AAA

Area Forecast Discussion...Updated
National Weather Service Phoenix AZ
535 AM MST Thu Nov 23 2017

.UPDATE...Updated aviation and fire weather discussions.


Dry weather and unseasonably warm temperatures will persist
through the weekend with near record highs each day. High
pressure will weaken early next week bringing cooler, although
still above average temperatures.


The impressively strong upper level ridge with 500mb heights up to
595Dm just to the southwest of Yuma will continue to bring record or
near record temperatures through this weekend. Highs today will
likely reach 90 degrees in the warmest desert locations while a
forecast high of 89 degrees in Phoenix would break the record of 87
degrees. Some high clouds should move in across much of the region
tonight lasting through Friday, likely keeping Friday`s highs a
degree or two cooler than today. The upper level ridge will remain
nearly stationary through the weekend with 500mb heights ranging
between 588-593Dm across southern California and southern Arizona.
Very little change in temperatures is seen for the weekend with
desert highs again reaching into the middle to upper 80s. Drier air
moving in from the southwest Friday night and Saturday will push any
high clouds off to the north and east.

Record heights and temperatures will finally end early next week
as a deep upper level trough off the Pacific Northwest coast digs
southeastward into the Great Basin on Monday. This will quickly
lower heights aloft across the Desert Southwest and bring a cold
front through the area starting Monday afternoon. Highs Monday
will cool into the 70s across southern California, but still
likely reach into the lower 80s for much of the southern Arizona
deserts. The cold front will also bring breezy to windy conditions
starting Monday evening lasting through Tuesday, especially
across the Lower Colorado River Valley where gusts to 35 mph will
be possible. For now models are in good agreement keeping the
shortwave trough and any significant moisture to our north,
passing through the Four Corners area Monday night. However, it`s
very possible at least some mid level CU and maybe a few virga
showers will pass over south-central Arizona along and just ahead
of the cold front later Monday.

Heights aloft should temporarily rebuild a bit for next Tuesday,
but shouldn`t allow for any additional warming as at least one
shortwave trough is shown moving into California and possibly the
Desert Southwest sometime during the latter part of next week.
Temperatures should remain above normal for a good portion if not
all of next week with desert highs generally in the middle 70s,
but will depend on the potential low pressure system. If models
stick with this solution in subsequent model runs, temperatures
will trend lower and precip chances may finally return.


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

Strong high pressure aloft will keep skies generally sunny today,
with a few mainly thin high clouds spreading in from the west later
in the day. Gradients will be a bit weaker and as such we should see
less wind today in the Phoenix area; the TAF sites should favor
their normal diurnal tendencies with speeds mostly below 8kt. No
aviation impacts expected for at least the next 24 hours.

Southeast California/Southwest Arizona including KIPL and KBLH:

Strong high pressure aloft will lead to generally sunny skies today,
with a few mainly thin high clouds spreading in from the west during
the latter part of the day. Bases should stay mostly aoa 25k feet.
Winds to remain light at the TAF sites, favoring the north at KBLH.
Most speeds should stay below 8kt with many light/variable
observations expected during the 24 hour period. No aviation impacts
expected for at least the next 24 hours.

Aviation Discussion not updated for amended TAFs.


Saturday through Wednesday: Strong high pressure aloft will lead to
continued very warm conditions over the weekend, with desert highs
in the mid and upper 80s Saturday and Sunday. Humidity levels stay
relatively dry, with minimum RH values mostly in the teens or low
20s. Winds will be light as well through Sunday. A low pressure
system passing by to our north during the first part of next week
will result in an increase in wind along with a sharp cooling and
drying trend. High temperatures will fall into the upper 70s to low
80s Monday, then into the 70s on Tuesday. Humidity levels will fall;
by Tuesday minimum RH values over the deserts will lower well below
15 percent with many of the deserts near or even slightly below 10
percent. Little change in RH is expected on Wednesday. Breezy
northwest winds will develop over the western Arizona and far SE
California deserts Monday afternoon with increasing wind again on
Tuesday favoring the north most locations. Wind gusts on Tuesday,
especially ridgetops, could exceed 40 mph in some favored locations.
Much less wind is expected on Wednesday with just some local
breeziness from the east to northeast expected nearly area-wide.


Record highs for selected dates this week:

Date      Phoenix       Yuma
----      -------       ----
Nov 23    87 in 1950    87 in 1950
Nov 24    88 in 1950    89 in 1950
Nov 25    88 in 1950    90 in 1950
Nov 26    88 in 1950    87 in 1950

The Phoenix record high for any Thanksgiving is 87 on Nov 23 1950
and Nov 27 2014. The Yuma record high for any Thanksgiving is 87
on Nov 23 1950.

Most days of 80+ during November in Phoenix: 24 in 1949.
Most days of 80+ during November in Yuma: 24 in 1954, 1950, and 1949.

Latest 90+ day in Phoenix: Nov 15 (1999)
Latest 90+ day in Yuma: Nov 25 (1950)


Spotters should follow standard reporting procedures.




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