305
FXUS65 KPSR 151146
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
446 AM MST Sat Jun 15 2024

.SYNOPSIS...
Dry conditions with above normal temperatures will continue this
weekend with local Excessive Heat Warnings remaining in effect.
The hottest day will be today with highs at least 5 degrees above
normal and breaching 110 degrees for many lower desert
communities. Readings will retreat several degrees back closer to
normal levels early next week as a series of weather disturbances
stream north of the area. A return to warmer than normal
conditions is likely during the latter half of next week.

&&

.DISCUSSION...
Upper level ridging has once again spread over much of the region
with H5 heights of around 591dm across southern California and
southern Arizona, or around the 90th percentile of climatology.
The ridge will boost temperatures today several degrees over
yesterday`s highs, reaching to between 110-113 degrees across much
of the lower deserts. By tonight, a large Pacific trough digging
southeastward through the Pacific Northwest will begin to
suppress heights over our region. This will help to bring some
slight cooling to the area starting Sunday as highs fall back to
107-111 degrees across the lower deserts. The approaching trough
will also cause winds to pick up across the area this weekend with
widespread breezy afternoon/evening conditions kicking in on
Sunday and lasting through Monday.

Further cooling will occur early next week as the Pacific trough
digs farther south toward our region, but with the core of the
trough only reaching as far south as northern Utah. Forecast highs
Monday are shown falling back closer to 105 degrees, or within
the normal range, while overnight lows drop well into the 70s.
These normal temperatures should persist through Wednesday as
broad troughing is likely to continue to influence the region.

Unfortunately, the unseasonably strong ridge that will impact the
Eastern U.S. early next week is expected to shift southwestward
midweek before sliding into our region by next Thursday. Ensemble
mean H5 heights are forecast to rise back to between 590-594dm
later next week as the sub-tropical ridge shifts back into our
region. There are still some model differences in the strength of
the ridge, but the NBM shows fairly low spread in boosting lower
desert highs to above 110 degrees over most of the lower deserts
as early as next Thursday. The NBM shows the hottest temperatures
falling on Friday with readings closer to 115 degrees right
before increasing moisture likely begins to curtail temperatures
into the following weekend. Guidance has been consistent in
showing a gradual uptick in low and mid level moisture later next
week with low end eastern Arizona higher terrain shower and
thunderstorm chances beginning as early as Thursday. As of now,
this moisture increase doesn`t look good enough to bring lower
desert rain chances, but it very well could result in gusty
outflow winds into the south-central Arizona deserts at some
point.

&&

.AVIATION...Updated at 0500Z.

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

No aviation impacts expected for the forecast period. Winds will
follow more normal diurnal trends today, but KPHX is still
expected to see light and variable winds with SE to SW-W
transition beginning this morning and lasting through most of the
afternoon. There may be periods of some gustiness with the
westerly winds 15-20 kts going into the late evening and into the
overnight periods. Winds will relax during the overnight periods
before turning back to the E-SE going into tomorrow morning. Skies
will remain mostly clear through the period, with the exception of
cumuliform clouds developing during the afternoon hours in the
higher terrain well to the east.

Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation impacts expected for the forecast period. Winds will
weaken toward morning becoming southeasterly at KIPL and light and
variable at KBLH. During the afternoon, expect for some enhanced
southerly breeziness at KBLH (gusts to 25kts) Saturday evening,
directions at KIPL will shift to southwest/westerly with some
gusts up to 20kts (more subtle change at KBLH to SSWly).
Otherwise, clear skies.

&&

.FIRE WEATHER...
Hot, very dry, and breezy conditions are expected through Monday
with increased winds Sunday and Monday resulting in elevated to
near critical fire weather conditions. Wind speeds will gradually
increase over the weekend with afternoon gusts at times reaching
20-25 mph today and 25-30 mph on Sunday and Monday. Higher terrain
areas in Arizona are likely to see the strongest winds on Monday
with gusts as highs as 30-35 mph possible. Minimum afternoon
humidity levels will continue to fall into the 5-10% range through
Monday following poor overnight recovery of only 15-30%. Afternoon
humidity levels will improve modestly to 10-15% range Tuesday and
Wednesday before falling back to 5-10% later next week. Strong
high pressure should build back over the districts during the
latter half of next week resulting in warming temperatures, but
also weakening winds. There are a few models suggesting somewhat
better moisture sneaking into eastern Arizona beyond next weekend
yielding a few thunderstorms over mountain areas, yet confidence
is very low given any early season activity typically results in
little actual wetting rainfall.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Sunday for AZZ534-537>555-
     559-560-562.

CA...Excessive Heat Warning until 8 PM PDT this evening for CAZ562-
     563-566-567-570.

&&

$$

DISCUSSION...Kuhlman
AVIATION...Young/AJ
FIRE WEATHER...18/Kuhlman