Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 221005

Area Forecast Discussion
National Weather Service Phoenix AZ
305 AM MST Wed Nov 22 2017

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 unseasonably strong high pressure ridge has now moved over
much of Arizona and southern California with the 594dm 500mb
height center just off the coast of Baja. This positively tilted
ridge will remain nearly stationary through Friday, but begin to
get flattened by Thursday night into Friday. Area 00z raobs showed
record or near record 500mb heights and these heights should
persist for another couple days. Today will be the first really
widespread warm day as warm air continues to advect northward.
850mb temps reach near 20C today or around 99% of climo, and inch
up another degree on Thursday which would be in record territory
for the date. Highs today should increase to between 84-88 across
the deserts and stick around these readings through Saturday.
Thursday still looks like it should be the warmest day, likely
breaking daily records. Some high clouds moving into northern and
central Arizona later Thursday may impact temperatures somewhat,
so temperatures may have to be adjusted down a degree or two in
subsequent forecasts.

A fast moving shortwave trough moving well to the north Thursday
night into Friday will knock down the ridge slightly, but little
change in sensible weather is expected. Once the trough moves into
the Plains States early Saturday, the ridge will rebuild slightly
while also pulling in drier air aloft from the southwest. This
will lead to clearing skies late Friday, lasting through much of
the weekend. The near record temperatures should last through the
weekend with highs holding fairly steady in the middle 80s and
lows mostly in the 50s.

Some relief from the unseasonably warm temperatures is likely to
move in early next week as a stronger upper level trough moves
southward into the Great Basin on Monday. This should drop highs
into the upper 70s and lower 80s while bringing increased clouds.
Good model agreement shows the trough tracking southeastward
through the Four Corners area Monday night into Tuesday with a
weak cold front moving through the Desert Southwest Monday
afternoon and evening. This will bring breezy and cooler
conditions next Tuesday as highs drop into the middle to upper
70s, but these readings are still a good 5-10 degrees above
normals. Heights aloft seem to trend lower into late week, likely
bringing even cooler conditions. Many areas should see overnight
lows dip into the 40s again starting late next week. No
significant moisture is seen moving into the Desert Southwest
through next week, so the dry streak will continue.


South-Central Arizona including KPHX, KIWA, and KSDL:
A weak backdoor cold front moving into south-central Arizona will
result in a more substantial easterly component than typical. This
could result in a period of stronger/gusty easterly winds after
sunrise as mixing occurs, but gusts should remain at or below 20
kt. Confidence is low that winds will shift out of the west during
the afternoon, and if they do, it`ll likely be brief. For now,
kept this mention out of the TAF as sustained easterly winds are
expected to persist, but will weaken throughout the day. High
clouds should begin to recede by late morning.

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

Aviation Discussion not updated for amended TAFs.


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.


Record highs for selected dates this week:

Date      Phoenix       Yuma
----      -------       ----
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)


Spotters should follow standard reporting procedures.




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