423
FXUS65 KPSR 231139
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
439 AM MST Sun Jun 23 2024

.UPDATE...
12Z Aviation Discussion.

&&

.SYNOPSIS...
Daily shower and thunderstorm chances will continue through early
this week, with most activity confined to the higher terrain areas
across southcentral Arizona. Cloudy conditions will persist
through at least today, which will keep temperatures a few degrees
cooler relative to the middle of this week, where highs will climb
several degrees above normal.

&&

.DISCUSSION...
Mid to high level moisture and clouds continue to stream in from
the southwest this morning, resulting in some scattered shower
activity according to the latest MRMS radar returns. Specifically
to southcentral Arizona, scattered showers are moving
northeastward across Gila County, with a more solid area of
showers moving into southern Maricopa County. Hi-res guidance
suggest these showers, especially in southern Maricopa and western
Pinal Counties to continue over the next several hours. After
these showers dissipate, attention turns towards afternoon/evening
convective activity once again. The highest chances again will be
focused over higher terrain areas, as cloud cover will continue
to be a limiting factor in potential/strength today as well as the
mean mid-level flow turns more southwesterly. Further west across
southwestern AZ and even into SE CA, less cloud coverage could
spark a few showers and storms as the elevated moisture levels
(and in turn more instability) will reach that region of the
forecast area today. General expectations for showers/storms are
around 30-40% (10-20%) for the higher terrain of southcentral AZ
(southcentral & southwestern AZ as well as southeastern CA). HREF
wind potential for 35+ mph for any outflows is much lower today,
generally 10-30% centered across southcentral and southwestern AZ
this afternoon and evening.

Ridging/surface high pressure will continue to migrate westward
going into tomorrow, continuing the downward trend for convective
activity, mainly due to strengthening subsidence aloft from the
building mid-level heights. This ridging feature will persist
through the middle of the week, resulting in a warming trend, as
mid-level heights hover in the 591-594 dam range. Widespread
Moderate HeatRisk will persist during this period, while localized
Major HeatRisk develop Tuesday through Thursday. While moisture
levels will remain elevated during this period (general consensus
is 1.75"-2.00" through Tuesday), thunderstorm chances will
diminish, especially for lower desert locations beginning
tomorrow. Thus, expect daily thunderstorm chances to reside mainly
in the higher terrain areas of southcentral Arizona going through
most of this week.

Looking towards the extended period, ensemble clustering shows
excellent agreement through at least Thursday, as a troughing
feature moves into the Pacific Northwest. As this trough traverses
across the Intermountain West going into this upcoming weekend,
mid-level heights will fall by a few decameters, resulting in a
slight cooling trend. More noticeable spread is seen in the
clusters by this upcoming weekend, where there is some uncertainty
in how quickly this trough exits the region and how quickly
heights build in from the east again. This will affect if and how
quickly temperatures may warm going through this upcoming weekend,
as current NBM temperature spreads are around 5-8 degrees for the
interquartile ranges for central Phoenix Saturday and Sunday.
Ensembles continue to show elevated moisture levels during the
extended period, thus while HeatRisk may remain mainly in the
Moderate category, higher humidity levels should still be
accounted for any outdoor plans during this period.

&&

.AVIATION...Updated at 1130Z.

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

Latest area radars indicate a batch of light SHRA progressing nwd
through south central AZ. These showers will likely weaken and
dissipate after sunrise, but are expected to pass near KPHX and
KIWA. No aviation impacts are anticipated. Winds will remain light
out of the ESE this morning. Due to abundant cloud cover, there
may be a slight delay in the onset of westerly flow this afternoon,
but high-res guidance does indicate a WNW shift in wind direction
by 20Z-21Z at the metro terminals. Convection this afternoon and
evening is expected to remain outside of the Phoenix Metro area,
but there could be outflow boundaries that emanate from distant
storms which could cause a brief wind shift. Timing of any
boundary is too uncertain to include mention in this forecast
package. Abundant mid-high lvl clouds will persist through the
forecast period.

Southeast California/Southwest Arizona including KIPL and KBLH:

VFR conditions will prevail at both terminals over the next 24 hrs.
Winds will remain southerly at KBLH through much of the day with
some afternoon breeziness anticipated. At KIPL, winds will be
southeasterly through this afternoon before switching out of the
WSW by sunset. A few isold storms may develop over/near the Kofa
mountains which in turn could create temporary gusty conditions
from the east/southeast at KBLH by late afternoon/early evening.
SCT mid-high clouds will continue through the forecast period.

&&

.FIRE WEATHER...
Monsoonal moisture will continue to result in daily chances for
shower and thunderstorm activity, with the best chances for
activity across the higher terrain areas. With the elevated
moisture in place, MinRH values through early this week will
range between 35-45% across the far eastern districts to between
15-25% across the western districts before slowly drying into the
middle to latter half of next week. Winds will follow their
typical daily tendencies, with gusty outflows from any
thunderstorm activity anticipated over the next several days.
Temperatures through the weekend will average near to slightly
above normal before increasing some heading into the middle of
next week. Chances for wetting rains will generally remain around
15-25% for the higher terrain areas and 5-10% for the lower
deserts of southcentral Arizona through tomorrow.

&&

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

$$

DISCUSSION...Young
AVIATION...Salerno
FIRE WEATHER...Young/Lojero