Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 300200

Area Forecast Discussion
National Weather Service Phoenix AZ
700 PM MST Sat Apr 29 2017

Somewhat cooler than normal temperatures will linger over the area
to close out the weekend, however gradual warming will start in
earnest Monday. Mostly clear skies will grace the region this week
and the first bout of 100 degree temperatures in Phoenix metro is
highly likely Thursday and Friday.


Pronounced cool northerly flow persists over the forecast area this
evening in the wake of deep troughing ejecting into the southern
plains. The enhanced baroclinicity and sfc pressure packing over
the region has allowed winds to be gusty once again today, though
speeds through the mixing depths are not nearly as strong as Friday.
Already seeing decoupling and weakening winds early this evening and
this trend will continue through the night. As a result, greater
fire weather concerns are largely alleviated and the region will
head into another cool late April night (clear skies and calming
winds) with overnight lows some 5F-10F below average (and likely the
coolest temperatures that will be seen in the next 5-6 months!).

Otherwise, shallow convection over far SE Gila County was mostly
dissipating with the loss of daytime heating and all remnant light
shower activity was advecting through the White Mountains and
western New Mexico. Should see temperatures drop fairly rapidly in
the next several hours in a very cool, dry airmass though the
forecast had mostly already accounted for this. So, get out and
enjoy early Sunday morning as its likely as refreshing as we`ll see
in some time here in the Southwest.


/158 PM MST Sat Apr 29 2017/
A low pressure system will slide eastward into the Plains overnight.
In its wake, sharp height rises will overspread Arizona and portend
a warming trend for Sunday.

Unfortunately, the cooler 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:
Timing wind shifts will be the only real aviation consideration
through Sunday afternoon under clear skies. Occasional gusts this
evening will rapidly weaken, but then follow the typical shift to
an easterly direction very late evening. The shift back to a
westerly component should occur in the traditional 18Z-20Z time
frame Sunday. Any wind gusts Sunday afternoon should remain near or
below 20kt.

Southeast California/Southwest Arizona Including KIPL and KBLH:
No major aviation concerns through Sunday afternoon under clear
skies. Gusty north winds this evening will gradually weaken and
trend towards a W/NW direction overnight and Sunday. Any stronger
wind gusts Sunday will be very temporary and mostly below 20kt.

Aviation discussion not updated for amended TAFs.


Tuesday through Friday:
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% for most areas with
the low deserts generally in the single digits. Overnight recoveries
will range from 25-35% and up to 40% in the elevated portions of
Gila county.


Spotter reports will not be needed through at least the middle of
next week.





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