677
FXUS65 KPSR 061710
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1010 AM MST Sat Jul 6 2024

.UPDATE...Updated 18Z Aviation Discussion.

&&

.SYNOPSIS...
Extreme heat will continue region-wide through most, if not all
of, next week with strong high pressure over the region.
Temperatures will be near daily records with lower desert highs
reaching 115 to 120 degrees. Some moisture return will bring
increased thunderstorm chances back to the Arizona high terrain
and southeast Arizona by the middle of next week.

&&

.DISCUSSION...
Deep mixing, record-level 850mb temperatures, around 32-33C, and
low specific heat capacity with the dry air likely helped
contribute to high temperatures overperforming by a few degrees
Friday afternoon. Several records were broken across the region
yesterday. There is every reason to believe something similar may
happen again in the following days, with very little change in the
environment as strong high pressure continues to dominate the
region. However, model soundings do indicate a slight cooling, by
1-2C, of the 850mb temps heading into this weekend. So, this
weekend`s highs are not forecast to be quite as hot as Friday, but
still within a couple degrees of daily records. The forecast
temperatures were blended with the NBM 75th percentile to nudge
highs up a degree or two, following the NBM deterministic`s
underforecast Friday.

An Excessive Heat Warning remains in effect through Tuesday
afternoon with no changes made during this morning`s forecast.
However, it is hard not to acknowledge the latest forecast which
has lower desert high temperatures remaining as high as 115-120F
each day through Friday next week. Through all of next week
global ensembles show little to no change in the height field over
the Desert Southwest, with H5 heights remaining in the 594-597dm
range, along with 850mb temps remaining near 30-33C each day.

The uncertainty in the temperature forecast, primarily in AZ,
remains tied to the gradual moisture return and subsequent
increase in storm activity anticipated beginning early next week.
A shortwave trough passing around the high pressure Monday is
expected to increase storm activity in NM and West TX, which
should in turn aid in low to mid level evening/overnight moisture
fluxes back into AZ. NBM PoPs steadily increase day to day
through next week, but most activity will likely remain isolated
to Southeast AZ and higher terrain spots like the White Mtns and
along the Rim. It will take some time for the South-Central lower
deserts, including the Phoenix area, to see better chances if at
all, with PWAT forecast to return to around 1.0" during the
second half of next week. While the South-Central lower deserts
may not see much thunderstorm activity, the potential for strong,
long-traveling, outflow boundaries will be there as the
environment will be ripe for strong downbursts. It is uncertain
this far out how much influence regional thunderstorm activity,
the moisture, and other mesoscale influences will have on
temperatures, but the synoptic pattern, with the center of the
high slowly trekking east across Southern NV and along the AZ/UT
border, will likely still support extreme heat through next week.

&&

.AVIATION...Updated at 1710Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation concerns are expected during the TAF period. Winds
will follow diurnal tendencies with occasional afternoon gusts in
the mid-teens, upwards of 20 kts. Mostly clear skies will prevail
through Sunday morning.

Southeast California/Southwest Arizona including KIPL and KBLH:
SE`rly winds will continued to be favored at IPL, with speeds
generally aob 10 kts. At BLH, S`rly winds will prevail, with brief
periods of gusts (20-25 kts) this evening and perhaps again by the
mid-morning hours Sunday. Clear skies can be expected through the
forecast period.


&&

.FIRE WEATHER...
Hot and dry conditions will prevail across the area through much
of next week as strong high pressure dominates. Excessively hot
temperatures with highs generally between 112-120 degrees are
expected across the lower deserts each day. Daily MinRH values
through next week will fall to or below 15% across the lower
deserts, while higher terrain areas in Arizona will mostly see
10-20%. Overnight recoveries will mostly fall in the 30-50% range.
Winds will be fairly light most days and follow diurnal trends,
occasionally gusting to 20 mph during the afternoon hours. The
breeziest day looks to be Sunday, primarily across eastern
districts, with afternoon wind gusts up to 20-30 mph. The
combination of the very hot and dry conditions will lead to an
increased fire danger threat.

&&

.CLIMATE...

Record Highs

           Phoenix      Yuma      El Centro
          ---------    -------   -----------
July 6    116 (1942)  117 (2018)  118 (1966)
July 7    118 (2017)  118 (2017)  121 (2017)
July 8    115 (1985)  118 (1958)  117 (1942)
July 9    116 (1958)  119 (1958)  117 (1958)
July 10   115 (1958)  118 (1959)  116 (2021)

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Tuesday for AZZ530>555-559.

CA...Excessive Heat Warning until 8 PM PDT Tuesday for CAZ560>570.

&&

$$

DISCUSSION...Benedict
AVIATION...RW
FIRE WEATHER...Benedict
CLIMATE...Kuhlman