Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 251606

Area Forecast Discussion
National Weather Service Phoenix AZ
906 AM MST Sat Mar 25 2017

A weak Pacific disturbance will move across northern Arizona
today. This system will be dry for southeast California and
southern Arizona, with high clouds clearing and a breezy
afternoon. This will be followed by a quick moving high pressure
system Sunday, followed by another Pacific disturbance for the
region later Monday through early Wednesday, particularly over
eastern Arizona. Dry and warmer weather will return next Thursday,
but followed by yet another Pacific storm Friday and Friday


Mid morning satellite imagery shows a fast moving shortwave
trough tracking across the Desert Southwest with the trough axis
across western Arizona as of 0900 MST. Little moisture exists with
this system and the bulk of the moisture remains above 15K feet.
Any light radar returns have been well north of our CWA border and
expect this to be the case the rest of today as it tracks through
Arizona. Have updated the forecast to remove any mention of
slight chance PoPs for today due to current trends and hi-res
models keeping any showers north our area. The band of high level
clouds across central Arizona will quickly push through the rest
of Arizona by around noon, but we do expect at least some
scattered high based CU this afternoon mainly over the high
terrain. Should see a bit of warming at the surface today over
south-central Arizona compared to yesterday`s readings while
similar temperatures are expected for Sunday.



Sunday and Sunday night...

Another transitory upper level ridge will build over the region
Sunday and Sunday night for mostly clear skies. Light surface wind.

Monday through Tuesday Night...

Another in a series of Pacific weather systems is forecast to move
into the region late Monday afternoon and night.  This is a deeper
and colder system, however still a bit moisture starved. A threat of
showers are forecast, predominately from Phoenix north through
southeast later Monday night through Tuesday evening. Since the
airmass is not expected to overly moist, only light rain is expected
with showers.

The biggest impact however will be wind. Gusty afternoon west winds
to 35 mph should develop over a large part of southeast CA and
Colorado River Valley Monday, becoming strong northerly in the same
area Monday night and Tuesday following the cold front. Afternoon
temperatures Tuesday should cool into the upper 70s at mainly
southwest and south central AZ desert locations.

Wednesday and Wednesday Night...

It appears that earlier predictions of a transitory high pressure
system over AZ Wednesday has slowed somewhat. The high pressure
system is forecast for Thursday instead. In the interim, a slight
chance of afternoon instability clouds and showers will continue
over the distant mountains east of Phoenix, namely southern Gila
County zone 24, and in general eastern AZ.


A high pressure will build back into the region for mostly clear
skies and near normal temperatures. light wind.

Friday and Saturday...

All models are in general agreement in developing yet another
Pacific trof over AZ this period. Models however are still
conflicted in the eventual track of this system, which has potential
to be the strongest, coldest, and wettest system in the series.
However big disparities exist with the model guidance, with the
European suggesting a more progressive trof through AZ Friday and
into New Mexico Friday night. The GFS on the other hand forecasts a
deep cold cutoff low to become nearly stationary over central AZ
Friday and Saturday. Forecast confidence is very low this far out,
so precip probabilities will be shaded toward a slight chance in
south central AZ.


South-Central Arizona including KPHX, KIWA, and KSDL:
Area of low pressure will move through northern Arizona, sweeping
trough heights through south-central Arizona today. Clouds will
increase from the west through midday, with mid-level BKN to OVC
Cigs 15-18kft. Some clouds may develop lower as the trough axis
clears the area, with SCT-BKN coverage 8-10kft by late aftn. Any
precipitation activity will stay north of the terminals over the
Rim and northern Arizona. Typical southeasterly morning winds will
turn westerly at or just after midday, with afternoon gustiness
20-25kts at times.

Southeast California/Southwest Arizona including KIPL and KBLH:
Upper trough will pass by to the north, increasing surface winds
from the west with midday and afternoon gustiness 20-25kts
possible for KIPL, less so at KBLH. Strong ridgetop winds in the
evening and overnight may develop into rotor/mountain wave
activity downwind for KNJK/KIPL overnight. OVC high level cloud
shield will continue to track eastward this morning, SCTing out by
midday with mostly clear skies developing by this evening.

Aviation discussion not updated for amended TAFs.


Monday through Friday...
Active storm pattern will remain over the Intermountain West at
least through the end of the month and possibly into early April
as a series of Pacific storms pass through. Breezy weather will
remain a common feature of most afternoons/early evenings for the
districts with daytime humidity levels ranging 10-25 percent at
their driest. Most of the Pacific storms will travel through the
Great Basin before sweeping into Arizona, allowing for above
normal chances of precipitation for the Arizona districts but near
to below normal chances for precip along and west of the Colorado
River Valley. With an active storm track over the area,
temperatures will trend more towards seasonal averages. Periods of
stronger winds may lead to a locally elevated fire danger at
times that may turn into critical fire weather conditions for some
locales. A fair bit of uncertainty remains with the track of the
next few systems to move through the region in the far extended
period that may ramp up or back off concerns for
elevated/critical fire danger.


Spotter reports will not be needed through the weekend.




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