Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 231111

Area Forecast Discussion
National Weather Service Phoenix AZ
411 AM MST Wed Jan 23 2019

.UPDATE...aviation and fire weather discussions.


High pressure centered to the west of the region will keep dry
conditions over the region for the foreseeable future. A warming
trend over the next several days will eventually result in high
temperatures in the lower seventies across the lower deserts. A
few weak, but dry upper level disturbances will bring periods of
gusty winds and high level clouds through early next week, but
they will ultimately have little impact on our weather.


The last week of January looks to be rather uneventful across the
Southwestern U.S. with dry conditions persisting through at least
the middle of next week. This will be mostly be due to a stagnant
upper level flow pattern with a mostly stationary eastern Pacific
ridge situated to our west and a polar vortex that sets up over
the eastern 2/3s of North America. For the Desert Southwest, this
will bring persistent north to northwesterly dry upper level flow
and mild temperatures likely lasting through the end of the month.

The cool airmass currently in place will result in one more below
normal temperature day before significant warming occurs into
Thursday. From Thursday through at least next Monday, highs should
top out in the lower 70s over the deserts, or a few degrees above
normal. Overnight lows will be closer to normals, or possibly a
couple degrees below normal as the dry air and generally clear
skies lead to very efficient nocturnal cooling conditions. Models
have been consistent showing multiple dry shortwave troughs
moving out of British Columbia and the Pacific Northwest
southeastward through the Interior West and eventually through or
near the Desert Southwest. The first trough Wednesday night into
Thursday will be the least significant and should only bring
locally breezy conditions. The second trough, moving through on
Saturday, is shown to be a bit stronger and farther southwest.
This one will likely bring stronger winds with more widespread
gusty conditions, especially across southern California. Forecast
PWATs of less than a quarter inch for both disturbances fall below
10% of climatology for the period.

A third trough is shown to move through the Southwestern U.S.
at some point early next week. This one is shown to carry a bit
more upper level moisture and will likely be a bit colder than the
previous two shortwaves. We should see an increase in clouds, but
again this system will pose no rain threat. Similar to the
Saturday system, this one too should bring gusty winds to portions
of the region. Temperatures also look to take a slight dip
starting next Tuesday, but readings should still remain within a
couple degrees of normals.


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

Light northeasterly winds are bouncing off of south mountain and
resulting in temporary wind directions out of the southwest. A
more dominant easterly wind component will develop by mid morning
before the direction switches to the west in the early afternoon.
Wind speeds will remain on the light side mainly aob 8 kts through
the TAF period. Skies will remain clear with scattered high
clouds moving in from the west after 12Z tomorrow morning.

Southeast California/Southwest Arizona including KIPL and KBLH:

Wind speeds will continue to weaken overnight with speeds mainly
aob 10 kts through the 12Z TAF period. Wind directions will favor
the northwest at both KIPL and KBLH. Skies will remain mostly
clear with scattered to broken cloud decks moving in from the west
late this evening.

Aviation Discussion not updated for amended TAFs.


Friday through Tuesday:
Dry conditions under high pressure aloft will dominate through
Monday bringing above average temperatures to the desert
soutwhest. A wave moves through Monday night and Tuesday, bringing
cooler and drier air to the region. Through Monday, humidity
readings will remain fairly stable dipping into the 15 to 25
percent range each day. On Tuesday, humidity levels will remain
below 15 percent across the lower deserts. This, combined with
strong northerly winds on Tuesday will cause conditions to flirt
with Red Flag criteria, especially along and west of the lower
Colorado River Valley. &&

Spotters should follow standard reporting procedures.




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