Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 191540
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
840 AM MST Sun Nov 19 2017

.SYNOPSIS...
The streak of drier weather and above normal temperatures will
persist through next weekend. A weak front has brought somewhat
cooler conditions to the area, though unseasonable warmth will
quickly return this week. In fact, record warmth will be likely by
the middle of the week and into the long holiday weekend.

&&

.DISCUSSION...
A fast moving, low amplitude shortwave was progressing into southern
New Mexico this morning helping reinforce dry advection and
subsident flow. After the coolest morning since the very beginning
of April, temperatures should respond quickly later this morning
breaking a shallow, steep inversion. Essentially a pure persistence
forecast today and only change in the sort term was to accelerate
this warming process during the late morning. All in all, another
near picture perfect day in the Southwest.

&&

.PREVIOUS DISCUSSION...
/449 AM MST Sun Nov 19 2017/
Models remain in excellent agreement through the weekend,
depicting gradual height/thickness rises associated with a
building ridge across the Intermountain West. The ECMWF ensembles
in particular are exhibiting remarkably low variability. This
will equate into a warming trend through late in the week with
NAEFS 500mb heights (in excess of 590dm) approaching records
Tuesday-Thursday, particularly in the Yuma vicinity. Some subtle
cooling is expected thereafter, though temperatures will remain
well above normal as the ridge slides eastward into the Plains.

Latest blended guidance continues to suggest that temperatures
will exceed daily records by Thanksgiving (Phoenix record for Nov
23rd is 87 in 1950; and for any Thanksgiving day is 87 on Nov 23
1950 and Nov 27 2014). However, given the exceptionally low
standard deviations evident in the ECMWF temperature guidance,
the official forecast was adjusted above the median of all
available guidance, which results in a high temperature of 89
degrees for Phoenix Thanksgiving Day.

It`s not totally out of the question that Phoenix could flirt
with 90 degrees Wednesday/Thursday, which would set a record for
the latest 90 at KPHX (record is 90 deg on Nov 15 1999). PoPs also
remain near 0 percent and it is very likely the long dry stretch
will continue into at least the end of November, which would
result in a meteorological fall (Sept-Oct-Nov) without any
measurable rainfall at Sky Harbor Airport (last occurred in 1938).

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:
Overall, very light easterly winds will affect the area this
morning, but stronger northeasterly winds may mix down for a
few hour period later this morning. Winds will struggle to go
westerly this afternoon, but should eventually turn out of the
west for a few hours into this evening. Winds tonight will again
be light and often variable. FEW to SCT high clouds into early
tonight will eventually increase and become BKN by Monday morning.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns through the TAF period. Skies will remain
mostly clear through this evening before increasing high clouds
move into the area from the west. Light west to northwest winds
will affect both KBLH and KIPL through Monday morning.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday:
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. Unusually dry air will also affect the area through the
middle of the week 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 late in the week. Light winds
will dominate for the duration of the forecast.

&&

.CLIMATE...
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

The Phoenix record high for any Thanksgiving is 87 on Nov 23 1950
and Nov 27 2014.

&&

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

&&

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

&&

$$

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DISCUSSION...MO/Hirsch
AVIATION...Kuhlman
FIRE WEATHER...Kuhlman
CLIMATE...MO


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