584
FXUS65 KPSR 090926
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
226 AM MST Tue Jul 9 2024

.SYNOPSIS...
Extreme heat will continue to prevail across the region
throughout the work week as daily high temperatures across the
lower deserts mostly top out between 112-118 degrees. Limited
moisture moving back into the area over the next few days will
provide for some chances for isolated showers and thunderstorms
across the eastern Arizona high terrain. By the weekend, moisture
should improve enough to bring chances into the Arizona lower
deserts, while also lowering temperatures closer to or just below
110 degrees.

&&

.DISCUSSION...
The average temperatures for the first 8 days of July has been
the hottest on record for our three climate sites; Phoenix, Yuma,
and El Centro. Daily records have also been broken and will
continue to be threatened through Friday as the strong high
pressure system remains put across the region. The center of the
high is currently positioned over southeast California with
guidance showing the center drifting northward toward Las Vegas
through Wednesday and then northeastward into southern Utah by
Friday. H5 heights over the region will continue to range from
592-594dm across eastern Arizona to 595-597dm near the center of
the high.

Temperatures over the next few days will not vary a whole lot with
highs mostly between 112-117 degrees across the south-central
Arizona lower deserts to 114-120 degrees across the western
deserts, or right around daily records. These readings are around
10 degrees above normal for the period. Overnight temperatures
will also continue to run above normal, but due to the dry
atmosphere and clear skies, lows are forecast to be mostly
between 2-6 degrees above normal. Widespread major to locally
extreme HeatRisk will continue through the end of the work week
with the Excessive Heat Warning in place through Friday.
Therefore, if partaking in outdoor activities it is very crucial
to take all the necessary heat precautions to avoid any heat-
related illnesses.

Moisture levels over the majority of the region remain quite low,
but modest moisture remains in place across New Mexico and
portions of northern Mexico. As the high center drifts northward
over the next couple of days, the flow aloft will shift more out
of the northeast into southeast Arizona. Initially this should
only provide for slight chances (10-20%) across far eastern Gila
Co. for today with the steering flow pushing any convection to
the south. Guidance does show chances extending more northwestward
along the Mogollon Rim starting Wednesday, so this could lead to
some gusty outflows reaching the Phoenix area Wednesday evening if
the weak convection is widespread enough just to the north of the
Phoenix area. Similar conditions are expected for Thursday, but
with slightly higher PoPs due to moisture levels gradually
improving.

Friday should be our transition day with temperatures still
reaching excessive heat levels, but moisture improving to the
point it should provide for convection getting close to the
Phoenix area. By midday Friday, the high center is forecast to be
over southern Utah turning the mid level flow out of the east.
This should advect better moisture out of New Mexico into eastern
Arizona resulting in more widespread and stronger convection over
the Arizona high terrain. An easterly steering flow at this point
should push convection and storm outflows more easily into the
lower deserts Friday evening. So far it doesn`t look all that
promising for convection to survive into the lower deserts due to
the expected limited moisture, but it should be the impetus that
allows for better moisture spreading westward through the Arizona
lower deserts.

The position of the high should be even more favorable for moist
flow into Arizona over the weekend as it shifts into western
Colorado starting Saturday. This should boost PWATs to around
1.5" and lift low level mixing ratios to around 10 g/kg.
Atmospheric conditions Saturday still don`t look optimal to have
widespread convection over the lower deserts, but PoPs improve to
20-30%. By Sunday, conditions look even more favorable for storm
activity as a weak disturbance is shown to form over southern New
Mexico, while moisture levels continue to improve. Temperatures
are forecast to drop below excessive heat levels over the weekend
as we lose strong influence from the high pressure ridge and
monsoon activity increases.

&&

.AVIATION...Updated at 0530Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major aviation weather concerns will exist through the TAF
period under mostly clear skies. Winds will continue to follow
diurnal tendencies, with easterly winds establishing within the
next several hours. A period of light speeds (aob 5 kt) and
variability can be anticipated late tomorrow morning before the
typical W`rly switch in the early afternoon. Westerly winds will
occasionally gust to between 15-20 kt late tomorrow afternoon. Hi-
Res guidance continues to indicate a low (<10%) chance for an
outflow boundary to push into the Greater Phoenix Area as early as
00Z tomorrow, but confidence in any of the terminals being
impacted is still too low to reflect in the TAFs at this time.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns are expected through the next 24
hours under clear skies. Winds will favor SE at IPL through much
of the period, whereas winds will continue out of the S-SW at BLH
through most of the TAF period. Gusts into the low 20s will be
possible at times at BLH.

&&

.FIRE WEATHER...
Hot and overall dry conditions will continue as high pressure
dominates overhead. There will be a slight chance of showers and
thunderstorms across eastern Gila Co today and Wednesday, but CWR
is below 10%. Afternoon high temperatures will generally be in
the 111-120 degree range across the lower deserts and in the
95-110 degree range across the higher terrain. MinRH values will
range from 5-15% across the lower deserts and 10-20% in the higher
terrain, with overnight recoveries generally in the 30-50% range.
Winds will be fairly light and tend to follow their typical
diurnal patterns, with some occasional afternoon gusts up around
20 mph. The very hot and dry conditions will lead to an
increased fire danger threat through the end of the workweek.
Moisture is forecast to improve Friday into the weekend with good
chances of showers and thunderstorms through south-central Arizona
starting over the weekend.

&&

.CLIMATE...

Record Highs

           Phoenix      Yuma      El Centro
          ---------    -------   -----------
July 9    116 (1958)  119 (1958)  117 (1958)
July 10   115 (1958)  118 (1959)  116 (2021)
July 11   118 (1958)  118 (1958)  117 (1975)
July 12   116 (2020)  119 (1939)  118 (1964)

&&

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

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

&&

$$

DISCUSSION...Kuhlman
AVIATION...Whittock
FIRE WEATHER...Kuhlman
CLIMATE...Berislavich/Kuhlman