Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 210440
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
940 PM MST Mon Nov 20 2017

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
The streak of drier weather and above normal temperatures will
persist through the week with unseasonable warmth quickly
returning the next several days. In fact, record highs will be
likely by the middle of the week and into the long holiday
weekend.

&&

.DISCUSSION...
Today is much like the past several days with warm temperatures
and passing high clouds. Temp readings are just slightly off from
24 hours ago, due in part to this high clouds and a very weak
embedded short wave. We`ll see just how high Phoenix gets but as
of 2 PM the high was 78F. If it holds below 80F, today will be
just the third day to accomplish such a feat this month. Given the
forecast, we may end up with the most 80+ days on record during
the month of November in Phoenix.

Upper air data this AM depicted 500 mb heights in the 580-582 dm
range (already) under a semi persistent anti-cyclone. Further
upstream, the storm track remains amplified and well entrenched,
featuring a re-invigorating low in the Gulf of Alaska, a ridge
over the Aleutian Islands, and another large low covering eastern
Russia. The GoA low is forecast to strengthen again the next
several days, which will excite the ridge over the Southwest
CONUS. H5 heights will reach as high as 594 dm, which will be
exceptionally high for late November (record heights likely). In
fact, GEFS and ECens members are all forecasting record level H5
heights for this event. This will clear out the high clouds and
lead to record level temperatures across our forecast area.
Current forecast max temps are already at or above record level
values; some model data suggests temps could be slightly warmer.
This will quite likely be the warmest (hottest?) Thanksgiving on
record for Phoenix and Yuma.

The GoA low will open up and eject eastward into Canada
Friday/Saturday, which will depress the ridge over us and cause
temps to dip very slightly but still remain near record levels.
Unfortunately, the GoA recharges with additional short wave energy
feeding into it, and that will keep the Southwest ridge locked in
place. Rain chances remain zero all areas throughout the seven
days.

There is some indication of a modest pattern change in the D7-10
range. The East Asian jet may strengthen and extend further out
into the Pacific, which will feed several waves out into the North
Pacific and get the weather pattern looking a bit more
progressive. While that doesn`t really mean precipitation, it at
least opens the door for one or two weather systems to dip further
south than the current storm track. Ultimately that may just mean
an increase in wind and cooler temperatures.

&&

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

With abundant cirrus clouds continuing to spill over the strong
ridge building over the west coast no aviation impacts are expected
during the TAF period. Familiar diurnal winds will remain light to
occasionally calm through Wednesday evening with the nocturnal
drainage easterly wind occurring very late tonight around 10-11Z.
Otherwise skies will remain cloudy to mostly cloudy with high cloud
CIGS near 25Kft.

Southeast California/Southwest Arizona including KIPL and KBLH:

Expect cloudy to mostly cloudy skies with bkn high clouds around 25K
ft. Winds will remain light to light and variable and favor the west
at KIPL and the north at KBLH. Expect the winds at KBLH will pick up to
near 10kt by the late morning.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday: Unseasonably strong high pressure aloft
will bring warming conditions through the middle of the week with
temperatures reaching into the middle to upper 80s across the
deserts starting Wednesday. Rather dry air will also affect the area
through Wednesday before there is a slight boost in moisture by late
in the period. Minimum RH values will fall between 10-15% through
Wednesday and 15-20% for the rest of the week. Light winds will
dominate for the duration of the forecast.

&&

.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    87 in 2014    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...Iniguez
AVIATION...Sawtelle
FIRE WEATHER...Kuhlman/CB
CLIMATE...MO/Iniguez



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