Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 240449

Area Forecast Discussion
National Weather Service Phoenix AZ
949 PM MST Mon Apr 23 2018

.UPDATE...Updated Aviation discussion.


Very warm and dry conditions will last into the coming weekend
with periods of high clouds. Lower desert high temperatures will
reach into the middle to upper 90s each day, or roughly 10 degrees
above normal. Some modest cooling is possible this weekend, but
above normal temperatures should still persist.


Some cirrus has begun to overspread the forecast area from the
southwest. This is due to a weak southern branch low centered west
of Baja Mexico. To the northwest of that, in the main branch of
the Westerlies, is a stronger system. This latter system will push
the southern branch low northeastward. The only impact for our
area with the weaker feature will be increasing high clouds
tonight and Tuesday. However, the cloud cover won`t thick enough
to keep up from climbing well into the 90s tomorrow. Otherwise, a
ridge will be centered over the interior West through at least
Thursday before starting to shift eastward Friday. That will mean
highs in the mid-upper 90s on the lower deserts through the rest
of the workweek. Warmest day looks to be Thursday with many
locations getting very close to, or touching, 100 degrees. One
potential fly in the ointment will be moisture working its way
into eastern Arizona from a backdoor front during the latter part
of the week. With southwesterly steering flow, it will be quite
difficult to get storms on the lower elevations. For now, slight
chances over our higher terrain areas east of Phoenix will be the
most we can expect.

Over the weekend and early next week it looks like we finally get
some cooling as the aforementioned main branch system moves into
the Western states. There continues to be some considerable
differences amongst the medium range models but overall there is
better agreement on cooling since the ECMWF has trended a lot
further south. That will also mean more wind. Just how much
cooling we get and which day will see the biggest drop remains


South-Central Arizona including KPHX, KIWA, and KSDL:
No aviation weather impacts expected. Light diurnal winds will
prevail at TAF sites through at least Tuesday evening.

Southeast California/Southwest Arizona including KIPL and KBLH:
Winds will retain a southerly component through the period at
KIPL/KBLH, though speeds will generally remain below 10 kt at KIPL
and 15 kt at KBLH.

Aviation Discussion not updated for amended TAFs.


Thursday through Monday... Well above normal temperatures
continue through Friday. Moisture from the southern Plains will
seep into eastern Arizona for a slight chance of thunderstorms
over portions of eastern Arizona Friday and Saturday. Over the
weekend, look for cooling and a significant increase in winds.
These trends will be driven by a large low pressure system moving
through the Western states. Uncertainty remains with the track and
timing of this system. There is some potential for conditions to
flirt with critical thresholds in some areas over the weekend.


Spotters are encouraged to follow standard reporting procedures.




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