703
FXUS65 KPSR 032059
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
159 PM MST Mon Jun 3 2024

..SYNOPSIS...
Quiet conditions will prevail through the work week with
temperatures hovering near to slightly above normal through Tuesday.
An Excessive Heat Waring is in effect Wednesday through Friday as
the hottest temperatures of the year are expected over the Desert
Southwest. A weak disturbance will move through the region during
the weekend, providing some relief from the excessive heat.

&&

.DISCUSSION...
Current analysis reveals quasi-zonal flow currently stretched out
across the Desert Southwest, while a relatively potent upper-low
advances toward the Pacific Northwest. This rather benign pattern
over our forecast area will continue to promote dry and tranquil
conditions, with temperatures hovering near to slightly above
climatological normals. Forecasted highs across the lower deserts
this afternoon will generally range between 100-105 degrees, with
similar temperatures anticipated again on Tuesday, yielding Minor
to locally Moderate HeatRisk for the next few days.

As mentioned in previous discussions, an anomalously strong ridge is
expected to build over much of the western CONUS during the
middle of this week, pushing temperatures to easily their hottest
levels since last September. Mid-level heights by Wednesday will
rise to between 591-594 dam across the Desert Southwest, allowing
for day-to-day temperatures to rise 5 degrees or so, with
forecasted daytime highs ranging between 105-110 degrees across
lower elevation communities. These enhanced heights aloft will
then persist through the remainder of the week, promoting further
warming and the development of widespread Major HeatRisk through
the end of the week has highs exceed 110 degrees for many areas.
In response to the increasing heat levels, Excessive Heat Warnings
have been posted for much of our forecast area for Wednesday-
Friday. Record highs may also be challenged during this period,
with the current Thursday forecasted high for Phoenix (113F) set
to break the daily record high (111F set in 2016).

Global model guidance depicts a weak shortwave trough approaching
the Desert Southwest this weekend which may offer at least some
relief from the aforementioned unseasonably hot temperatures as
it helps to erode positive height anomalies across the region.
Given the forecasted evolution and orientation of this system,
increased moisture flux is anticipated over the region, with PWAT
values rising to 175-200% of normal for this time of year across
much of Arizona. However, forecast soundings show much of this
moisture suspended aloft with a dry sub-cloud layer. This setup
would inhibit rainfall chances for much of our area, with the NBM
squeezing out max PoPs of only 10-15% for far southern and eastern
Gila County. However, if sufficient moisture becomes available
like the models expect, it would not be surprising to see a few
showers and perhaps a thunderstorm over high terrain areas. As of
now, the most lower elevation areas would see in terms of rainfall
would be virga and maybe a shower or two, but PoPs over these
areas remain <10%. At a minimum, the increased moisture should
blanket the region in considerable cloud cover, which will also
help keep temperatures cooler compared to the days prior.

Heading into the start of next week, model clusters become more
separated with their forecasts, with some projecting the ridging
pattern returning, while other develop another trough/cut-off low
just west of the Baja Peninsula. The former would suggest the
return of well-above normal temperatures, with the latter solution
favoring the continuation of more seasonal temperatures. Plenty
of spread remains, so how the pattern evolves will be something to
keep an eye on over the next several days.

&&

.AVIATION...Updated at 1758Z.

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

Across the Phoenix metro, wind behavior and timing of typical
wind shifts will follow a near persistence forecast including
occasional westerly gusts 15-20kt during late afternoon/early
evening. There will be a period of southerly winds, with some
SW-SE variability, during the midday timeframe before the westerly
winds predominate. In SE California, winds will settle more out
of a SE direction through most of the TAF period at KIPL, with a
brief period of SW this evening. Southerly winds will prevail at
KBLH. SCT, to at times BKN, high cirrus will pass over the region
through the next 24 hours.

&&

.FIRE WEATHER...
Little to no change in the weather pattern will keep seasonably dry
and hot conditions in place through Tuesday. Expect lower desert
highs between 100 and 105 degrees, or 3-5 degrees above average each
day. MinRH values will continue to run between 5-10% across the
majority of the area each day, while overnight recoveries will
continue to range from poor to fair at around 25-40% over the
eastern districts to 35-50% over the western districts. Winds will
remain fairly light following diurnal tendencies with periodic
afternoon gusts of 15-20 mph. The latter half of the week will see
even hotter temperatures with potential for highs around 110 degrees
Wednesday through Friday over portions of the lower deserts. There
will also eventually be a slight improvement in humidities by next
weekend along with a low end chance (10-15%) of some isolated
thunderstorms over the Arizona higher terrain.

&&

.CLIMATE...

Record high temperatures:

Date        Phoenix         Yuma         El Centro
----        -------         ----         ---------
June 5    113 in 2016    115 in 1957    114 in 2016
June 6    111 in 2016    114 in 1928    113 in 2002
June 7    115 in 1985    116 in 1985    113 in 1985

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning from 10 AM Wednesday to 8 PM MST Friday
     for AZZ530>556-559>562.

CA...Excessive Heat Warning from 10 AM Wednesday to 8 PM PDT Friday
     for CAZ561-563-566-567-569-570.

&&

$$

DISCUSSION...RW
AVIATION...Benedict/Kuhlman
FIRE WEATHER...Young/Kuhlman
CLIMATE...18