819
FXUS65 KPSR 161007
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
307 AM MST Sun Jun 16 2024

.SYNOPSIS...
Hot afternoon temperatures will persist for the foreseeable
future, however there is expected to be cooler temperatures by a
few degrees settling into the region starting tomorrow. Afternoon
breezes will become more elevated over the next couple of days,
increasing the fire weather concern. Hotter temperatures expected
to return late week, with increasing thunderstorm chances as well
going into this weekend.

&&

.DISCUSSION...
Early morning satellite depicts dry zonal flow over the region.
This pattern will keep temperatures will above normal today, as
an Excessive Heat Warning continues for portions of the forecast
area, including the Phoenix metro and higher terrain communities
such as Globe/Miami and San Carlos.

The next system that will cool temperatures across the region
currently resides offshore of the Pacific Northwest, as the
shortwave is digging southeastward. As this shortwave strengthens
and digs over the next 24 hours, mid-level heights across the
Desert Southwest will fall, resulting in negative height anomalies
by tomorrow. These negative heights anomalies will persist through
the middle of the week, resulting in temperatures cooling by
several degrees, as highs will hover only a couple degrees above
normal through the middle of the week. With this developing
trough, breezes across the region will increase, leading to
elevated to near critical fire weather conditions, especially on
Monday. More widespread breeziness (and locally windy) will begin
out west today, with the lower deserts of southeast CA gusting
25-30 mph this afternoon and into the evening hours. On Monday,
this breeziness will spread across southcentral AZ, resulting in
breezes 20-25 mph (30-35 mph) for the lower deserts (higher
terrain) during the afternoon and early evening hours.

Once the troughing feature lifts out of the region, ridging will
begin to build in from the east going into this weekend. Thus,
expect temperatures to rebound back above 110 degrees for highs
across the lower deserts starting as early as Thursday. Current
NBM probabilities show a 30-60% (5-15%) chance of 110 (115)
degrees or greater across the lower deserts of southcentral AZ on
Thursday and peaking on Friday around 60-90% (30-60%). Due to the
higher heights building in from the east, temperatures will run
several degrees warmer across southcentral AZ than southeastern
CA. Ensemble clusters are seemingly good agreement through this
period, thus another excessive heat period looks like the scenario
to prepare for later this week.

Another development with this pattern change late this week is
enhanced moisture levels advecting into the region (most notably
into southcentral AZ), with the surface high pressure setting up
in the vicinity of the NM/TX border beginning Thursday. Current
ensemble guidance depicts PWATs north of 150% of normal building
into the region beginning Thursday and persisting into the
weekend. There are definite timing and magnitude differences
between the ensembles in regards to this moisture advection, but
thunderstorm chances will begin to increase starting Thursday and
continuing through at least Saturday. The latest NBM
PoP`s/thunderstorm chances continue to range between 10-30% for
the higher terrain of southcentral AZ, with the lower deserts
remaining low (10% or less). Monitoring the high pressure
development and evolution/movement will be key in determining how
good (or bad) thunderstorm chances will truly become late week
and into the weekend for southcentral AZ.

&&

.AVIATION...Updated at 0554Z.

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

No major aviation weather concerns are expected through the TAF
period. West winds will make the usual diurnal switch to the east
overnight before veering toward a southerly component mid to late
morning Sunday. Breezy westerly winds take hold by early Sunday
afternoon, gusting upwards of 20-25 kts across the Valley.
Otherwise, SKC conditions will persist.

Southeast California/Southwest Arizona including KIPL and KBLH:

Winds at KIPL will vary between the SSE and W/SW through the
period, while winds favor the south at KBLH. W/SW winds at KIPL
and S winds at KBLH will increase tomorrow afternoon/evening,
with gusts upwards of 25-30 kts at KIPL and around 25 kts at
KBLH. Otherwise, SKC conditions will persist.

&&

.FIRE WEATHER...
Hot and dry conditions continue through most of this week, but
elevated to near critical fire weather conditions will be in play
today and tomorrow due to increasing breezy to locally windy
conditions across the region. Generally, winds are expected to
gust 20-30 mph on Sunday (western districts) and Monday (eastern
districts). The higher terrain areas in southcentral AZ are likely
to see the strongest winds on Monday with gusts as highs as 30-35
mph possible, resulting in localized critical fire weather
conditions. Minimum afternoon humidity levels will continue to
remain 10% or less through Monday following poor overnight
recovery of only 15-30%. Humidity levels will improve modestly to
10-15% range Tuesday and Wednesday before falling back to 5-10%
later this week. Strong high pressure should build back over the
districts during the latter half of this week resulting in warming
temperatures, but also weakening winds. Increasing moisture
levels late this week are currently projected to increase
thunderstorm activity over mountain areas (10-20%), but
uncertainty remains in how high the moisture levels will become,
thus hindering the outlook on wetting rain chances at this time.


&&

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

CA...None.
&&

$$

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