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Area forecast discussion
National Weather Service Phoenix Arizona
155 am MST Tue Nov 21 2017

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


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 northwest and western Canadian provinces.
21/00z regional radiosonde observation 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.


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
ceilings 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 relative humidity 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.


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...


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