Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 211940
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1240 PM MST Tue Nov 21 2017

.SYNOPSIS...
Dry weather and unseasonably warm temperatures will persist
through the weekend with record highs likely by the middle of the
week. High pressure may weaken early next week bringing cooler,
although still above average temperatures.

&&

.DISCUSSION...

Latest satellite imagery shows high clouds over the desert
southwest this morning that are pinwheeling around an unusually
strong high pressure system positioned west of Baja California.
Over the course of the next 12 hours, this expanding ridge of high
pressure will push these high clouds north and east out of our
area as the deserts bake under mostly sunny skies. Latest 12Z
sounding from Tucson, Yuma, and San Diego indicates heights of
587, 589, and 591 dm, respectively. These height values indicate
the unusually warm airmass that is present and exceed the daily
records for all locations expect Tucson. However, with the ridge
expanding eastward, record heights will likely be reached at
Tucson tomorrow morning, if not this afternoon.

Increasing heights will undoubtedly bring warmer surface
temperatures across the desert southwest today, a reflection of
the warm air advection that is happening aloft as the ridge
marches eastward. Latest model guidance suggest temperatures will
soar into the upper 80s by Thanksgiving, and for a few unlucky
locations (or lucky depending on your perspective), eclipse the 90
degree mark. The warmest desert temperatures, by a degree or two,
will be found in California due to their closer proximity to the
high pressure center. In any event, temperatures will be
unseasonably warm with many locations forecast to reach and
possibly exceed many heat related records (see climate section
below).

Very warm temperatures will persist through the weekend as the
ridge will be slow to progress eastward. It isn`t until early next
week do models show a Pacific trough passing to our north
suppressing heights and bringing some relief (low 80s and
possibly upper 70s). However, even readings of those magnitudes
are still above average. As it stands right now, above normal
temperatures with absolutely no precipitation is forecast for
the foreseeable future.


&&

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

No aviation concerns for the next 24 hours as winds follow typical
diurnal tendencies. Winds will remain weak through early tomorrow
morning as skies gradually clear. A weak backdoor front will
bring enhanced easterly flow later Wednesday morning (17-20Z) as
the atmosphere mixes down higher momentum air to the surface, but
easterly gusts should stay at or below 15 kts. Winds may stay
easterly all day on Wednesday but will be rather weak by the late
afternoon hours.

Southeast California/Southwest Arizona including KIPL and KBLH:

Clearing skies with very light winds, following typical diurnal
tendencies will prevail for the next 24 hours. No other aviation
concerns.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Thursday through Monday: Strong high pressure aloft will persist
across the lower deserts for the rest of the week and likely into
early next week as well. This will keep high temperatures well above
seasonal normals with the warmer deserts into the mid to upper 80s
most every day this week. Sunny to mostly sunny days are on tap
through Saturday, with some increase in mid and high clouds expected
Sunday into Monday. Expect relatively dry conditions as well with
minimum RH values each day running from the teens to around 20
percent. Winds each day will be on the light side, favoring typical
diurnal tendencies especially across the south-central deserts.

&&

.CLIMATE...
Record highs for selected dates this week:

Date      Phoenix       Yuma
----      -------       ----
Nov 21    88 in 1924    90 in 1950
Nov 22    89 in 1950    91 in 1950
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)


&&

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

&&

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

$$

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DISCUSSION...Wilson
AVIATION...Wilson
FIRE WEATHER...CB
CLIMATE...MO/Iniguez



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