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fxus65 kpsr 181718 
afdpsr

Area forecast discussion
National Weather Service Phoenix Arizona
1018 am MST Tue Jun 18 2019

Update...updated 18z aviation discussion.

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Synopsis...
the weather pattern over the next week will remain uneventful with
near normal temperatures lasting through Thursday before gradually
cooling to below normal levels. A weather disturbance skirting
north of the area late in the week will bring periods of breezy
conditions, but also cooling temperatures with some Lower Desert
communities struggling to even reach 100 degrees this weekend.

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Discussion...
nearing the Summer solstice, the region will remain under a broad
troughing pattern keeping temperatures at or below normal through
at least early next week. The current upper level pattern shows a
open trough centered just off the Southern California coast, but
this will wash out into Wednesday as a shortwave trough passes
through the central rockies. The most dominant synoptic feature
remains to be the strong upper level high across the eastern
Pacific and this will continue to steer weather systems
southeastward through the Pacific northwest into the Great Basin
and central rockies. Temperatures will remain near to slightly
below normal through the middle of the week while typical dry
conditions (pwats ~0.50") persist.

For Thursday into Friday, a strong upper level trough is forecast
to track southward through the Pacific northwest into the Great
Basin, increasing the mid level flow across the Desert Southwest.
This will lead to breezy to locally windy conditions both Thursday
and Friday, aggravating the already problematic fire weather
conditions across the area. One positive thing will be the
slightly cooler air mass resulting in highs dropping closer to 100
degrees beginning Friday. As the trough axis swings through the
region on Saturday, it may even prevent saturday's highs from
reaching 100 degrees across a good portion of the lower deserts.
This pattern looks to continue through early next week with
temperatures likely creeping up a couple degrees, but the slightly
below normal temperatures and dry conditions should continue into
the middle of next week.

Peaking beyond the forecast period, the gefs and eps persist the
western US troughing almost through the end of the month while
positive height anomalies sit somewhere near the Southern Plains,
which would seem like a Summer continuation of our winter weather
pattern. While not climatological abnormal, the subtropical jet
appears to be a bit more active than one would anticipate heading
into July. This pattern means the subtropical ridge to our south
will continue to struggle building northward. Convection has yet
to develop across northern Mexico, so we will be watching and
waiting for the typical northward March to develop at some point.
Phoenix (kphx) itself typically does not typical measure its first
Summer rainfall until July 14 (based on 1981-2010 data). Of course,
areas to the east and south experience it earlier. The latest first
Summer rainfall for kphx occurred in 1995, when the first measurable
rain wasn't notched until August 14th.

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Aviation...updated at 1715 UTC.

South-central Arizona including kphx, kiwa, ksdl, and kdvt:

There are no aviation weather concerns through at least tonight.
The winds will most likely remain light through the rest of this
morning and early afternoon as the wind direction shifts from
easterly to westerly with some periods of a southerly crosswind
for kphx. The westerly winds later this afternoon, from 03z-05z,
will be accompanied by gusts up to 17 kts. Smoke plumes from
nearby wildfires may create slantwise visibility issues for
eastward take-offs/approaches this afternoon and evening. Otherwise,
expect an easterly wind shift during the early Wednesday morning.



Southeast California/southwest Arizona including kipl and kblh:

There are no aviation weather concerns through at least tonight.
The winds will remain fairly typical with speeds at or below 15
kts, and favoring typical diurnal trends.

Aviation discussion not updated for amended tafs.

&&

Fire weather...
Thursday through monday:
temperatures will hover very near the middle of June averages
heading through the middle of the week, however a weather system
moving north of the districts will allow notable cooling over the
weekend with reading pushing back below normal. Regardless,
afternoon humidity values will still fall near 10% with mostly poor
overnight recovery (only locally fair recovery at high elevations
and parts of southeast california). In response to the weather disturbance
late in the week, afternoon winds will increase Thursday and
Friday with gusts 25-30 mph common. While remaining below critical
thresholds, these winds combined with low humidity values and very
dry fuels will result in an elevated fire danger both days.

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Spotter information statement...
spotter activation is not expected.

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Psr watches/warnings/advisories...
Arizona...none.
California...none.
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