000
FXUS65 KPSR 180037
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
537 PM MST Mon Jun 17 2019

.UPDATE...Updated Aviation discussion 0037z.

&&

.SYNOPSIS...
With only occasional passing clouds, temperatures will sit around
average for the majority week. A weather disturbance skirting
north of the area late in the week should created periods of
breezy conditions, but also cool temperatures somewhat with some
lower desert communities struggling to even reach 100 degrees.

&&

.DISCUSSION...
WV imagery and objective analysis show a weak positively tilted
trough stationed through the Great Basin and extending into the
Southwest this afternoon. Several vorticity centers have been
rotating through the mean trough axis, however the environment
remains quite dry with 0.70 inch PWAT and 4 g/kg mixing ratios
measured on the first 12Z KPSR sounding of the season. Once again
today, isolated showers will spread through far northern Arizona,
but little other than some thin high clouds and briefly gusty winds
will impact southern Arizona.

The overall pattern will remain stagnant through much of the week as
stronger positive height anomalies anchor through the central
Pacific and weak midlevel troughing and dry southwest flow sit in
place over the SW Conus. With H5 heights steady in a 585-588dm
range, model spread through the middle of the week is very narrow
and temperatures should hover not far from the climatological
average. A late week upper level low moving into the Pacific
Northwest has trended a bit more robust with a slightly deeper and
more southern solution. Odds are quite good that H5 heights fall
closer towards 580dm by the weekend yielding another period of below
normal temperatures. In fact, there is a reasonably good chance high
temperatures on Saturday and Sunday fail to reach triple digits for
most low elevation communities. Aside from avoiding any excessive
heat, the greatest impact from this system may be an increase in
gusty winds Thursday and Friday. While speeds will not be
exceedingly high, they will be enough to exacerbate on-going fire
concerns.

With essentially zero chance of rain through at least early next
week, smoke output from the Woodbury Fire may be an issue for many
downstream communities. With the fairly persistent weather pattern,
recent smoke tendencies should repeat over the next several days
with only some oscillation between a more southerly drift (i.e.
through Wednesday) versus a westerly push (more likely towards the
end of the week). Mid/late afternoon enhancement of fire activity
will allow deep smoke plume development and downstream (NE)
advection through Tonto National Forest and the Salt River Canyon
Wilderness. Overnight inversions will allow more trapping of smoke
and recent tendencies have been for settling through the Tonto and
Verde basins either side of the Four Peaks Wilderness. Thus far,
there has been no observation or future evidence of smoke drifting
south or west towards more populated areas, and have focused smoke
forecasts towards the past several days of GOES-17 Blue and Red
Visible band imagery.

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.

&&

.AVIATION...Updated at 0037 UTC.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The mean flow will remain southwesterly through Tuesday with a
trough axis persisting across southeastern California. The
forecast will more or less be persistence, with typical diurnal
winds occasionally interrupted by periods of southerly crosswinds
at KPHX during the early afternoon. However, sustained winds
during this window will generally remain less than 10 kt.

Southeast California/Southwest Arizona including KIPL and KBLH:
Diurnal winds expected through Tuesday with the strongest gusts
reaching around 20 kt at both KIPL and KBLH.

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 SE 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.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

DISCUSSION...Iniguez/MO
AVIATION...Hirsch
FIRE WEATHER...MO

NWS PSR Office Area Forecast Discussion