Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 211012 AAA
AFDPSR

Area Forecast Discussion...Updated
National Weather Service Phoenix AZ
310 AM MST Tue Nov 21 2017

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

&&

.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...
Overnight conditions similar to those last evening with thin high
clouds, and some patches of thicker cirrus, streaming across the
region from the northwest. Unseasonably strong ridging continues
to build into the region with the circulation center off the
central Baja Coast and ridge heights lifting the storm track and
upper jet well into the Pac NW and western Canadian Provinces.
21/00z regional RAOB flights sampled 500mb heights in the mid 580s
on the north/northwest periphery of the ridge center and 500mb
height progs paint low to mid 590s possible over northern Baja,
Colorado River Valley and southern California by Wednesday and
Thursday. Values in this range climb into record-territory on
numerous parameters including ML height and temperature fields and
resultant surface temperatures. Cirrus cloud coverage will thin
and dissipate as strong ridge subsidence and displacement of the
upper jet occurs, clearing skies by Wednesday. Forecast
temperatures remain unchanged, painting one of the warmer (if not
the warmest) Thanksgiving on record for many Southwest locales.
Temperature records for both Phoenix and Yuma are referenced in
the Climate section below.

Area of strong troughing moving through northeast Pacific will
transition on-shore by the late week/early weekend, flattening
ridge heights across the Intermountain West. Subtle cooling will
result for much of the region, however still remain above late
November normals with temps still holding in the 80s. Highly
amplified wave pattern remains over the North American continent
into the weekend with broad ridging remaining over the Four
Corners on up through central Canada. This will keep the current
dry streak count running and climbing north of 90 days since
measurable rain occurred at Phoenix Sky Harbor. Rank for this
streak stands at the 39th driest as of Mon Nov 20, tied with a
streak that ended in July 2010.

In the extended forecast, strong jet streak (180kt or stronger)
progged to develop off the Asian continent should break down the
larger blocked pattern feeding several smaller shortwave and
progressive features into the North Pacific. A more open pattern
should lend itself towards more forecast temperature variability
and some periods of elevated winds, however moisture parameters
still look lacking.

&&

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

High pressure aloft centered to our west will continue to give a dry
northwest flow aloft into the greater Phoenix area today into
Wednesday. There will be periods of embedded high clouds, mostly
aoa 25k feet. We can expect BKN cigs much of the time but cirrus
will often be on the thin side. Otherwise, gradients remain weak and
wind at the TAF sites will be light, favoring typical diurnal
tendencies. Much of the time, KSDL will be light/variable or calm.
There are no aviation concerns today, tomorrow or for most of this
week at least.

Southeast California/Southwest Arizona including KIPL and KBLH:

Dry northwest flow aloft will persist today into Wednesday and there
will be periods of high cloud embedded in the flow with bases mostly
aoa 25k feet. There will be BKN cigs at times with the high cirrus
often thin. Winds will be very light at the TAF sites next 24 hours,
often light variable or calm. No aviation impacts expected for at
least the next 24 hours.

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    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...Nolte
AVIATION...CB
FIRE WEATHER...CB
CLIMATE...MO/Iniguez



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