849
FXUS65 KPSR 011039
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
339 AM MST Mon Jul 1 2024

.SYNOPSIS...
Current shower and isolated thunderstorm activity across south-
central and southwestern AZ will persist through the morning with
the activity winding down by the early to mid-morning timeframe.
Another round of isolated to scattered showers and storms is
expected this afternoon and early evening across south-central AZ.
Daily rainfall chances continue through Wednesday, with most of
the activity confined to the higher terrain locations. Dry
conditions return on the 4th of July and continue into the weekend
as high pressure starts to move into the region. Above normal
temperatures will continue through the weekend, with excessive
heat conditions for portions of the Lower Colorado River Valley
and southeastern California.

&&

.DISCUSSION...
There is ongoing activity stretching from northeast Arizona to
southwest Arizona, with some activity within the Phoenix Metro. On
upper-level water vapor we can see a weak easterly wave moving
through southern Arizona along with a broad trough moving into
northwest Arizona. These features along with southerly flow
advecting some moisture into into the region are likely causing the
ongoing shower activity. A few isolated lightning strikes are also
possible. This activity is expected to come to an end around
sunrise, or mid-morning at the latest.

Hi-res guidance differs on how this afternoon will play out and will
likely depend on how quickly activity ends this morning and how
quickly clouds can clear out causing more sunlight to heat the
surface and increase instability. Current PWATs are in the 1.7-1.9"
range and are forecasted to stay within that range throughout the
day. Most of the hi-res guidance does keep any activity this
afternoon and early evening confined to the higher terrain
locations. However, the HRRR does show some isolated showers and
storms across portions of the lower deserts, mainly in western
Maricopa County and locations to the east. GFS soundings also depict
an uncapped environment this afternoon. So if we can get some of the
clouds to clear out across the lower deserts this afternoon the
environment would be poised to produce some shower and thunderstorm
activity.

The 00Z HREF indicates the greatest instability will set up over
southern Arizona and extend up into western Maricopa County, with
MUCAPE values of around 1000 J/kg and around 750 J/kg in the Phoenix
Metro. The HREF also shows no CIN in place across south-central
Arizona this afternoon and early evening. Activity is expected to
initiate over the higher terrain locations to the east of Phoenix as
well as to the southwest of Phoenix. The steering flow today will
be southwesterly, so the activity to the southwest of Phoenix
will be important to watch for it to either potential move into
Phoenix or produce an outflow that moves through the Phoenix Metro
that can kick off some storms. The environment today will also be
supportive of outflow boundaries with soundings showing DCAPE
values in the 800- 1000 J/kg range. While todays activity is a lot
more conditional than yesterday`s activity, any storms that form
will be capable of producing gusty winds, and brief localized
heavy downpours. The HREF shows a 30-50% of winds exceeding 30 kts
across Maricopa County and 50-70% of exceeding 30 kts across
Pinal County. These wind speeds could cause areas of localized
blowing dust, especially across the usual dust prone areas. Some
minor flooding cannot be ruled out, especially if storms move over
areas that have already seen a lot of rain.

Ensemble guidance still depicts a change in the synoptic pattern by
Thursday, with a strong high pressure system stretching from the
eastern Pacific to the Great Basin. The position of this high
pressure system will give our region dry northwesterly flow which
will usher out a lot of our moisture, especially at the mid- and
upper-levels. While, some moisture will remain within the
boundary layer, the much drier mid- and upper-levels will suppress
any convection. NBM PoPs have lowered for Thursday and Friday and
are now around 5-10% across the higher terrain and <5% across the
lower deserts. Ensemble guidance does start to show some moisture
starting to move back in to the region by late this weekend.

Temperatures for much of this week will remain above normal and will
not fluctuate a whole lot. Lower desert high temperatures will be in
the 105-113 degree range across south-central Arizona and in the
110- 115 range across southeastern California and far southwestern
Arizona. Overnight lows will be in the low-to-mid 80s across the
rural deserts and in the upper 80s to low 90s in the urban areas.
The hotter temperatures in southeastern California and far
southwestern Arizona will result in widespread Moderate HeatRisk,
with isolated Major HeatRisk. Due to this, an Excessive Heat
Warning is in effect for portions of southeastern California and
the Lower Colorado River Valley through Friday. Speaking of
Friday, it looks to be the hottest day of the week this week with
afternoon high temperatures 2-5 degrees warmer than the rest of
the week.

&&

.AVIATION...Updated at 0536Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:

A preponderance of spotty showers with embedded thunder is
expected through the rest of tonight, primarily just north and
west of the metro. However, a 15% chance in the metro will
continue. There is uncertainty in wind directions through the
night as the showers to the north and west may lead to a wind
shift to the W or N, but if this happens, when, and for how long
is uncertain. Otherwise, expect SE to E winds to prevail through
Monday morning. Any lingering SHRA/TS should diminish/move out
toward sunrise Monday. SE-E winds will shift SW around midday
Monday with afternoon gusts into the teens. There will be another
slight chance (10%) for SHRA/TS Monday afternoon, but confidence
and model probability is too low at this time for inclusion in
the TAF. Lowest cloud bases will remain around 10K ft, aside from
in SHRA/TA, with SCT to BKN coverage at times.

Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation aviation weather concerns expected through the
TAF period. Winds will generally be out of the southeast at KIPL
and out of the south at KBLH. Winds are expected to gust upwards
of 20-25 kts late Monday morning and afternoon at KBLH, with
weaker guest out of the west for a brief period Monday evening at
KIPL. Skies will remain mostly clear.

&&

.FIRE WEATHER...
Moisture levels remain high today with additional chances for
isolated to scattered showers and storms and gusty outflow winds
late this afternoon and evening across south-central Arizona. Min
RHs will be in the 25-25% range over south-central Arizona and in
the teens across southeastern California and far southwestern
Arizona.Overnight recovery will be good and in the 40-60% range in
the eastern districts and in the 30-40% range in the western
districts. Outside of thunderstorms, winds will tend to follow
their typical diurnal patterns. Daily monsoon storm chances
continue through Wednesday, although most of the activity will be
confined to the higher terrain locations. Min RHs will be in the
15-25% range Tuesday and Wednesday with overnight recoveries in
the 30-50% range. Dry conditions and ending rain chances start on
Thursday and continue into the weekend. Temperatures will remain
above normal through the week, with Friday being the hottest day
this week.

&&

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

CA...Excessive Heat Warning until 8 PM PDT Friday for CAZ562-566-567-
     569-570.

&&

$$

DISCUSSION...Berislavich
AVIATION...Benedict
FIRE WEATHER...Berislavich