Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 081555
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
855 AM MST Thu Dec 8 2016

&&

.SYNOPSIS...
Dry weather with seasonably comfortable temperatures will persist
over the region through the weekend. Only periods of passing high
clouds will interrupt an otherwise beautiful stretch of early winter
weather. No precipitation is expected anywhere in the area into the
middle of next week.

.DISCUSSION...

Very quiet morning across our cwa...under mostly clear skies and dry
northwesterly flow aloft. Temperatures this morning across the lower
deserts are now in the 40s and low 50s, which is very close to
normal for this time of year. A warming trend is expected to begin
today as weak ridging begins to build eastward from the west. latest
model guidance continues to show highs rising into the mid-60 to
near-70 range today across the lower deserts. Other than some very
minor adjustments to the hourly grids to better reflect current
trends, inherited forecasts look good.

&&

.DISCUSSION...

At 2 am this morning, skies were generally clear across the area as
subsidence behind an exiting short wave led to substantial thinning
of the mainly high level cloud decks. Dry northwest flow aloft was
present, as seen in the recent 00Z plot data and area RAOBs and the
surface dewpoints over the central deserts had lowered mostly into
the 30s early this morning. Progs agree that flat upper ridging will
be building into the desert southwest over the next couple of days
leading to a warming trend with desert highs forecast to rise into
the low 70s by Friday despite another batch of high clouds
spreading into the area.

Operational model guidance such as the GFS and ECMWF as well as GEFS
ensembles has been consistent with its outlook for our weather over
the next 7 days; we will be looking a dry conditions along with high
temperatures staying near or slightly above seasonal normals with
little significant temperature trends day to day. Model isotach
progs keep the upper jet north - if not well north - of Arizona into
the middle of next week, keeping the storm track way north of our
area and steering any potential precipitation producing waves well
to our north. Anticylonic shear aloft will dominate as will general
subsidence; mid-level Q-convergence progs suggest mostly Q-
divergence each day or minimal amounts of convergence. With the flow
staying rather zonal each day, this will allow for periods of mainly
high clouds to quickly race into and then out of the area, leading
to partly cloudy skies at times. Little change in the forecast was
made on this shift, only minor tweaks to some of the temperature and
sky grids, otherwise the forecasts look to be in good shape.

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:
There are no major weather impacts to aviation. Winds will remain
relatively light and favor typical diurnal patterns for the TAF
period. There will be periods of some high clouds towards Thursday
afternoon but will not concern any of the terminals.

Southeast California/Southwest Arizona including KIPL and KBLH:
There are no major weather impacts to aviation. Winds will be
primarily out of the northwest to north but with some occasional
variability. Skies will be mostly clear with just a few high clouds.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Saturday through Wednesday:
Slightly above normal temperatures and mostly dry conditions are
likely through the period with high clouds moving across the area at
times. Overall, the weather patterns shows little day to day change
with a zonal westerly flow aloft over the area. Winds each day will
mostly stay on the light side with typical afternoon breeziness
favoring the southwest or west. Humidities will be elevated through
the five day period with minimum RH values mostly between 20 and 30
percent each day. There are no significant fire weather concerns for
the next five days.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters activation will not be needed this week.

&&

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

$$

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DISCUSSION...Percha/CB
AVIATION...Deemer
FIRE WEATHER...CB/Deemer



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