Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/06/23

Area Forecast Discussion

National Weather Service Phoenix AZ

 532 PM MST Wed Jul 5 2023

.UPDATE...
Updated Aviation discussion.

&&


.SYNOPSIS...
High pressure will continue to predominate the overall weather
pattern across the Desert Southwest into next week. High
temperatures of around 110 degrees are expected across the lower
deserts through the weekend. An Excessive Heat Warning is in
effect for the south-central Arizona lower deserts through Friday.
Dry and breezy conditions each afternoon will result in elevated
fire weather concerns. For the first half of next week, even
hotter conditions are likely with enough monsoon moisture moving
into southeastern Arizona for some chances for isolated high
terrain thunderstorms.

&&

.DISCUSSION...
Latest water vapor imagery and streamline analysis reveal a well-
defined anticyclone across southern California with the ridge axis
extending eastward into southeastern Arizona. This is resulting
in a continuation of the above normal temperatures, clear skies
and below normal dewpoints across the Desert Southwest. Latest
ACARS soundings indicate a pronounced subsidence inversion around
500 mb with PWATs around 0.7 inches near Phoenix.

Over the next few days, the aforementioned anticyclone will
become repositioned across New Mexico, resulting in a dry
southwesterly flow and continued well above normal temperatures.
Further west, latest models indicate a subtropical area of low
pressure will move northeastward towards the Baja Peninsula and
into southern California, suppressing the positive height
anomalies to the south and east. This will result in somewhat
cooler conditions across southeastern California and an increase
in uncertainty further east across the lower deserts of Arizona.
Current Excessive Heat Warning for south-central Arizona goes
through Friday and for now this will not be extended into the
weekend. However, latest trends in the grand ensemble suggest
another significant warming trend next week.

Latest ECMWF ensemble shows a concerning trend with an
anomalously strong subtropical ridge strengthening and meandering
to the north and west. Given the inherent uncertainty further out
in time, positive height anomalies of +2 standard deviations from
an ensemble system suggest the potential for near record
temperatures next week, with high temperatures likely reaching
113-119 degrees each day in Phoenix. A slight increase in
humidity will also translate into well above normal low
temperatures, which will inhibit overnight recovery and exacerbate
the Heat Risk.

One thing to consider is the longevity of the heat wave and the
cumulative effects on the body. There have been 5 consecutive
days so far of 110+ degrees in Phoenix and the record of 18
straight days set in June 1974 could be challenged. Although it is
unlikely the all-time daily record of 122 degrees will be reached
in Phoenix, latest NBM does indicate roughly a 10 percent chance
of reaching this value at Phoenix Sky Harbor Airport sometime next
week. Meanwhile, latest trends in the ensembles do suggest a
gradual increase in moisture emanating from Mexico next week as
well. However, low-level mixing ratios and subsequent instability
will likely remain inadequate for even isolated convection, except
across the higher terrain of eastern and southeastern Arizona.

&&

.AVIATION...Updated at 0032Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT and
Southeast California/Southwest Arizona including KIPL and KBLH:

Clear skies can be expected through at least Thursday. Winds will
continue to follow familiar warm season diurnal patterns through
Thursday afternoon. For the Greater Phoenix area, this will mean
westerly winds continuing through the evening with a slow
overnight transition to light downvalley/drainage winds (favoring
east component) followed by a resumption of afternoon westerly
winds with gusts generally 15-20kts. For KIPL, this will mean
daytime winds favoring southeast directions and evening/overnight
winds favoring westerly directions.

&&

.FIRE WEATHER...
Hot, dry, and breezy conditions will persist for the next several
days. High temperatures will continue to run several degrees
above normal across the central and eastern Arizona with minimum
relative humidity falling below 15 percent each afternoon.
Winds will oftentimes be breezy during the afternoon and early
evening hours with gusts reaching 20-25 mph across much of the
area. These dry and breezy conditions combined with the extreme
heat will result in elevated fire weather conditions for much of
area this week and into this weekend. Overnight moisture recovery
will range from poor to fair each night. For next week, even
hotter conditions are expected with a gradual increase in moisture
likely leading to isolated thunderstorm chances over the eastern
Arizona high terrain.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Friday for AZZ534-537>544-
     546-548>551-553>555-559.

CA...None.
&&

$$

DISCUSSION...Hirsch
AVIATION...Lojero
FIRE WEATHER...Kuhlman