Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 212119

Area Forecast Discussion
National Weather Service Phoenix AZ
219 PM MST Sat Apr 21 2018

Building high pressure this weekend will result in a significant
warming trend with high temperatures reaching into the middle 90s
by Monday. The very warm and dry conditions will last through next
week with highs nearing 100 degrees over the warmest desert


The weekend warmup is well underway with 24 hr trends for early
this afternoon of +7 to +12 degrees across the forecast area.
Expect several more degrees of warming Sunday thanks to the ridge
over the western states. Cirrus clouds are starting to move in
from the southwest. This is due to a very weak upper low/short
wave within the southern branch of a split in the Westerlies.
Anticipate more coverage of cirrus on Sunday as the wave tracks
across the region. It will weaken as it does so. Anticipate that
the cirrus will not be thick enough to offset the warmth aloft
that will mix down. Another short wave moves in Tuesday ahead of a
deep upper low off the West Coast. It will fizzle out due to
ridging in place. So, anticipate some additional warming Monday
with little change in temperatures Tuesday.

For the latter half of next week, there are some model differences
on how the coastal low will evolve. But there is general agreement
that it will stay off the West Coast through much of the week with
any cooling holding off until next weekend. Overall little change
in temperatures is seen through the workweek with highs generally
falling in the middle to upper 90s each day. Some locations will
likely reach and possibly top 100 degrees on Wednesday and
Thursday when the highest heights aloft are forecast. The weak
flow will also keep winds on the lower side providing a bit of a
break from the recent high fire danger episodes.


South-Central Arizona including KPHX, KIWA, and KSDL and Southeast
California/Southwest Arizona including KIPL and KBLH:

No aviation concerns are anticipated through Sunday afternoon.
Winds will remain light following typical diurnal directions,
becoming variable at times. Some increase in mid to upper level
clouds possible this afternoon and overnight, with SCT coverage
above 15 thousand feet.

Aviation Discussion not updated for amended TAFs.


Tuesday through Saturday...
Temperatures will be around 10 degrees above-normal for much of
this period as high pressure builds across the Southwest. A dry
air mass will result in RH values in the single digits each
afternoon and fair to poor overnight recovery. Weak pressure
gradients will continue to favor light and diurnally driven winds
each day, with only occasional afternoon gusts expected. Some
increase in breeziness is possible Friday/Saturday, but widespread
strong winds are not anticipated.


Spotters are encouraged to follow standard reporting procedures.




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