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Area forecast discussion 
National Weather Service Phoenix Arizona
855 am MST Fri Dec 2 2016

Synopsis...

A strong and cold low pressure will move quickly south through the
region today and tonight, with its center tracking south along the
Colorado River valley. Although dry weather is forecast, strong and
gusty north winds will develop across a large part of southeast
California and the Colorado River valley today through Saturday. Dry
and warmer weather will return Sunday and Monday. Another large
Pacific low pressure system is forecast to move into the western
states next Tuesday and Wednesday, however this system will track
farther north across Utah and northern Arizona. Therefore dry,
breezy, and slightly below normal temperatures are forecast the
middle of next week.

&&

Discussion...

A transition to a somewhat more active weather pattern is underway
this morning across the region. The upper low that will be bringing
a slight chance for showers today/tonight across southern Gila
County and some very strong winds to southeast California/lower Colorado River
valley can be seen on latest WV satellite imagery moving southward
across Imperial County, and will be crossing the international
border shortly. Northerly to northwesterly winds are already picking
up across the region, with sustained winds up to 20 mph being
observed at this time. 88-d radar is also now showing echoes across
central and northern AZ, but most of these are yet to reach the
cloud, due to the still-high cloud bases and very dry subcloud layer
(dewpoints in the 20s and low 30s). For the short term, outside of
some minor edits to the hourly grids, inherited forecasts seem to be
capturing current trends well, and no updated are planned at this
time.

&&

Previous discussion...

Today through Saturday...

A cold upper level low pressure system centered over central Nevada
last evening will continue to move south toward Mexico and intensify
the remainder of this morning and afternoon. Since the airmass
remains very dry, rapid intensification of this system will
squeeze/wring out the atmosphere for every bit of moisture,
resulting in considerable mid level cloudiness and virga type
threatening skies in southwest and south central Arizona through early
afternoon. In fact mid level clouds had developed so fast around
midnight that both Phoenix and Yuma radars were switched into precip
Mode (vcp212). A slight chance of showers will continue over the
higher elevations of southern Gila County today through Saturday
morning.

Otherwise the main effect from this deepening system is wind, strong
wind today through Saturday over a large part of southeast California and
Colorado River valley. A Wind Advisory remains in effect for the
above mentioned areas beginning at 8 am PST today through 8 PM PST
Saturday. Northerly gusts between 35-45 mph are expected with
possible peaks near 50. Needless to say areas of blowing dust and
sand are expected. Clearing skies area-wide are expected Saturday
afternoon as the upper low pressure center deepens farther south
into northwest Mexico and away from our forecast area.

Sunday and Monday...

Dry northwest flow aloft will develop over the region this period.
Nearly cloudless skies are expected with afternoon temperatures
approaching seasonal normals.

Tuesday and Wednesday...

Another deep cold Pacific trof is forecast to move into the western
states Tue and part of Wed. This system will track north of our
forecast area, southeast California to south central AZ, basically across
the 4 corners region. Dry and breezy conditions can be expected with
afternoon temperatures near or slightly below normal.

Thursday and Friday...

Dry northwest flow aloft will develop over the region this period.
Nearly cloudless skies are expected with afternoon temperatures
near seasonal normals.

&&

Aviation...
south-central Arizona including kphx, kiwa, and ksdl:

A fairly light diurnal wind Patten will persist for the first part
of the taf period. Although the winds will remain to be light, the
afternoon westerly winds will have a more north to northwest
direction. A high level cloud deck will continue infiltrate from the
west dropping the ceiling down to the 10-12kft range by Friday
afternoon before lifting and clearing into the evening.

Southeast California/southwest Arizona including kipl and kblh:

Windy conditions will impact the terminals starting around 16z and
lasting through the taf period. The north to northwest winds will be
sustained 20-30kts with gusts up to 35kts. Also, a thick cloud deck
down 9kft will persist through the morning before more broken cloud
conditions take hold heading into the afternoon.



Aviation discussion not updated for amended tafs.

&&

Fire weather...
Sunday through thursday:

There is a slightly elevated fire danger potential on Sunday for
southeast California and parts of western Arizona. The main concerns
will be windy conditions and relative humidities below 15 percent.
However, the duration of these conditions is short lived and the
overnight recovery for relative humidity is fair. In addition,
breezy conditions on the order of 10 to 20 mph are likely for much of
south-central Arizona and southeast California beginning Tuesday and
lasting through Wednesday. Minimum relative humidity will stay in the 12 to 30
percent range with decent overnight recoveries.

&&

Spotter information statement...
spotters are encouraged to report according to Standard criteria.
Spotter reports of wind and dust may be needed Friday across
southeast California and southwest/west Arizona.

&&

Psr watches/warnings/advisories...
Arizona...Wind Advisory from 9 am this morning to 9 PM MST Saturday for
azz020-025.

California...Wind Advisory from 8 am this morning to 8 PM PST Saturday for
caz030>033.

&&

$$

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Discussion...percha/vasquez
aviation...Deemer
fire weather...Deemer

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