592
FXUS65 KPSR 190505
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1005 PM MST Wed Jun 18 2025

.UPDATE...Updated Aviation Discussion

&&

.KEY MESSAGES...

- Extreme Heat Warnings remain in effect across south-central
  Arizona through Friday as lower desert high temperatures range
  from 108 to 116 degrees.

- Very dry and increasing breezy conditions will lead to elevated
  to locally critical fire weather conditions across higher
  terrain areas of south-central Arizona on Friday and Saturday.

- A cooling trend over the weekend will result in slightly below
  normal temperatures starting Sunday and lasting through early
  next week.

&&

.DISCUSSION...
Very dry air, evident in WV imagery early this afternoon,
encompasses the region as the sub-tropical high continues to build
into the region from the southwest. This dry, northwesterly flow
is resulting in PWAT`s 50% percent of normal, with this general
level of dryness continuing into this weekend. Due to the
subtropical high building across the Desert Southwest through
tomorrow, Extreme Heat Warnings continue for the lower deserts of
south-central Arizona through Friday. Temperatures through the end
of the week will continue to hover 8-12 degrees above normal,
with a 10-20% chance of breaking the daily high record in central
Phoenix tomorrow (118 degrees set in 2016 & 2017).

The overall weather pattern will begin to transition from strong
sub-tropical ridging late this week to negative height anomalies
moving in from the northwest in association with a strong,
anomalous Pacific trough amplifying across western CONUS over the
weekend. This transition period will result in continued very dry
conditions, but also some increasing winds that will lead to
elevated to locally critical fire weather concerns late this week
and into the early weekend. Afternoon winds could gust upwards of
30 mph (30-50% Friday, 50-70% Saturday), peaking on Saturday.
However, due to cooling temperatures of ~5 degrees by Saturday,
the fire weather threat will remain primarily below critical.

This Pacific trough will bring much welcomed cooler temperatures
to the region over the weekend, as high fall to the lower 100s,
which is near to slightly below normal for this time of year.
Strong high pressure building in the eastern half of the country
will act to hold troughing in place through the middle of next
week, keeping neutral or negative mid-level height anomalies
across the Desert Southwest through the middle of next week. The
main discrepancies amongst the ensembles is how quickly this
trough will dissipate and eject east of the region, but the
temperature uncertainty still remains quite small as NBM IQR`s are
still ~5 degrees through the middle of next week.

&&

.PREVIOUS DISCUSSION...

The trough situated just to our northwest is likely to keep
southwesterly winds and dry air working into at least western
portions of Arizona, but at the same time deep moisture over
northern Mexico may be able somewhat seep into eastern Arizona. At
the moment, the most likely scenario calls for some marginal
monsoon moisture to make its way into southeast Arizona providing
for isolated to scattered convection as early as Monday, but more
likely into Tuesday. There may also be some low end chances for
showers and storms as far north as the White Mtns and into Gila
County by Tuesday. It will definitely be something to watch over
the coming days.

&&

.AVIATION...Updated at 0505Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No major aviation concerns are expected during the TAF period
under clear skies. Winds will follow familiar diurnal trends with
periods of variability overnight. After a period of S`rly
crosswinds at KPHX and KDVT late Thursday morning/early afternoon,
the typical W`rly shift will occur with gusts developing to around
20 kts.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation concerns are expected over the next 24 hours
under clear skies. Typical diurnal trends will prevail through
Thursday morning before breezy conditions develop during the
afternoon hours, gusts to around 25 kts.

&&

.FIRE WEATHER...
Hot and dry conditions will continue today with overall light
diurnal winds. Temperatures will remain above normal with highs
near or above 110 degrees across the lower deserts through Friday.
Continued dry conditions, but increasing winds starting tomorrow
and into this weekend, will preclude elevated to locally critical
fire weather conditions across the eastern district higher
terrain, primarily Friday and Saturday. On Friday, very dry
conditions will persist (min RH`s 5-10%), with afternoon winds
gusting 20-25 mph. On Saturday, wind gusts will increase to 25-35
mph but min RH`s will rise to around 10-15% as temperatures cool.
Elevated fire weather concerns will subside going into early next
week as winds weaken and temperatures continue to cool to around
or just below normal while also increasing MinRHs into the teens.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Friday for AZZ534-537>544-
     546>556-559>562.

CA...None.
&&

$$

DISCUSSION...Young
PREVIOUS DISCUSSION...Kulhman
AVIATION...RW
FIRE WEATHER...Young