Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 291636

Area Forecast Discussion
National Weather Service Phoenix AZ
936 AM MST Sat Apr 29 2017

Below normal temperatures can be expected today as a storm system
slowly shifts eastward into the southern Rockies. Breezy
conditions will also be possible through this afternoon, but wind
speeds will generally be much weaker than yesterday. Still, high
fire danger will continue across the lower Colorado River Valley
through the late afternoon. A warming trend will begin Sunday into
next week, with the first 100 degree reading of the year forecast
for Thursday at Phoenix.


Latest satellite imagery shows a large and well-defined PV
anomaly drifting southward near the Four Corners. In its wake,
cooler air has infiltrated the Desert Southwest. Morning low
temperature at Sky Harbor Airport reached 58 degrees, which is
several degrees below normal. Meanwhile, observed dewpoints are
already into the teens this morning.

Model consensus indicates a reinforcing shot of drier air this
afternoon, particularly across southeastern California and
southern Arizona as the low pressure system migrates into
northeastern New Mexico. Aside from some stratocu wrapping around
the low across the higher terrain east of Phoenix, skies will
remain clear. Only some minor adjustments to the short-term
temperatures are needed this morning. Otherwise, the forecast
remains on track.


Temperatures are forecast to be well below-normal today, with
afternoon readings in the upper 70s to lower 80s likely to result
in an extremely pleasant day. Winds will remain gusty on occasion
as well. Despite the cooler temperatures, the very dry air mass
will continue to support high fire danger across the lower
Colorado River Valley today, and a Red Flag Warning is in effect.

Unfortunately, the cool temperatures will be short-lived, and the
heat will return with a vengeance into the middle part of next
week as a pronounced ridge of high pressure builds over the
Southwest. Confidence is increasing that the first 100 degree
reading of the year will be reached at Phoenix on Thursday, with a
repeat performance on Friday. More uncertainty into next weekend
as deterministic models are hinting at the development of
potentially an anomalously deep upper trough over the Pacific
coasts. A wide range of scenarios could occur, including
increasing moisture over the Southwest and significantly cooler
temperatures. However, with low confidence at this point, trended
more towards climatological norms during this period for all
forecast parameters.


South-Central Arizona including KPHX, KIWA and KSDL:
Elevated northerly breezes will continue today after yesterday`s
strong frontal passage. Morning northerly winds 10-15kts will
eventually drop towards more westerly headings in the early
afternoon, with gusts nearing 20kts possible. Skies will remain
mostly clear, save for some afternoon CU AOA 12kft which will
dissipate with sunset.

Southeast California/Southwest Arizona Including KIPL and KBLH:
Elevated northerly winds to continue for the terminals, with KBLH
seeing the stronger speeds than KIPL. Gusts near 30kts will be
possible starting mid morning and continuing through the day.
Skies to remain clear to mostly clear.

Aviation discussion not updated for amended TAFs.


Monday through Thursday:
A ridge of high pressure will slowly build over the west next
week with the lower deserts making another run at 100 degrees
during the latter half of next week. No strong wind events are
anticipated. Minimum humidities will remain low - below 15% most
areas with low deserts generally single digits. Overnight recovery
will be fair.


Spotter activation will not be needed through the middle of next


AZ...Red Flag Warning until 7 PM MST this evening for AZZ131.

CA...Red Flag Warning until 7 PM PDT this evening for CAZ231.



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