000
FXUS65 KPSR 102341 AAA
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
440 PM MST Fri Jul 10 2020

.UPDATE...Updated Aviation Discussion.


.SYNOPSIS...
Abnormally strong high pressure building over the area into early
next week will result in excessive heat with lower elevation high
temperatures rising into the 115 to 120 degree range. Stable
conditions will keep thunderstorm coverage limited and favoring
the high terrain east of Phoenix. Extreme temperatures should
subside early next week, but temperatures likely will remain above
normal.

&&

.DISCUSSION...
Dewpoints rose this morning in the wake of an outflow boundary
that developed from an MCS in northern Sonora overnight. This
moisture surge caused an increase in mid and upper level moisture
causing PWATs to rise to 1.40" in this mornings sounding.
According to the SPC sounding climatology page, a PWAT of 1.40" in
the 12Z Phoenix sounding falls right between 90 percent and the
max moving average. Despite good moisture, a steep and unfavorable
inversion can be observed around 500 mb. This is due to very warm
temperatures in the mid-levels from strengthening high pressure
aloft. These stable conditions will limit thunderstorm coverage,
however, the HREF is showing isolated activity is possible in the
eastern portions of southern Gila county this afternoon and early
evening. There is also indication that light showers/virga could
develop early tomorrow morning along an outflow generated from
another northern Sonora MCS. With another moisture surge expected
tonight, there will definitely be plenty of moisture tomorrow
afternoon for isolated to scattered thunderstorms. HREF is
indicating a little more coverage tomorrow, with most of the
activity in southern Gila county. However, the potential is there
for activity to get into the far eastern portions of Maricopa and
Pinal counties. Gusty erratic winds and lightning will be the two
biggest impacts. QPF should be minimal.

The big story will be the heat through early next week. Models
remain consistent indicating mid-tropospheric heights peaking
tomorrow across Arizona. However, 850 mb temps won`t plateau until
Sunday, which will likely be the hotter day. Nevertheless,
forecast high of 115 deg in Phoenix Saturday will result in
widespread high heat risk.

NBM and ECMWF ensembles are still exhibiting some variability
with regard to temperatures, which is likely a reflection of the
uncertainty in overall moisture since humidities will be
sufficient for isolated thunderstorms each afternoon.
Consequently, it is difficult to pinpoint exactly how high the
temperatures will get, particularly due to occasional debris
clouds disrupting the diurnal cycle.

The aforementioned anticyclone will begin drifting eastward early
next week. This will result in a more pronounced southwesterly
flow and somewhat of a cooling trend, though temperatures will
likely remain above normal for the foreseeable future. The EPS and
GEFS also don`t highlight any particular day as being more
favorable for convection. However, it is conceivable that isolated
activity could develop early in the week and this is reflected in
the NBM single-digit PoPs. ECMWF ensemble PWAT anomalies
generally drop below average beginning next Wednesday, which will
essentially negate any chance of organized shower and thunderstorm
activity.

&&

.AVIATION...Updated at 2340Z.

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

No major aviation concerns expected through the TAF period. Breezy
westerly at the current time to continue into the early evening
hours, with a few gusts into the teens at times. Lighter westerly
winds to continue well into the night before a brief switch to
easterly occurs during the early morning hours on Sat. Some of the
high-resolution models due indicate an outflow boundary could make
its way northward from decaying TS over SE AZ, but even the most
aggressive model output washes the boundary out before it gets into
the greater PHX area. Westerly winds will then return on Sat
afternoon. FEW-SCT decks aoa 15 kft and SCT-BKN clouds around 25 kft
will be possible throughout the TAF period.

Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation concerns anticipated through the next 24 hours.
Winds at KIPL to veer toward the west this evening, then become
southeasterly overnight and on Sat. At KBLH, winds will favor a
southerly component through the period. Winds may become light and
variable at times mainly during the overnight hours. Otherwise, FEW-
SCT mid and high clouds aoa 15 kft will be possible throughout the
next 24 hours.

&&

.FIRE WEATHER...
Monday through Friday:
Dry conditions and well-above normal temperatures can be expected
Monday with lower deserts seeing highs in the 115-120 degree
range. Some cooling can be expected during the Tues-Fri period.
Daytime minimum humidity values will be around 5-15% for most
places while overnight recoveries will rise into the 20-40% range.
Wind speeds will be light most days, outside of typical afternoon
breezes up to 20-25 mph, with directions following local terrain
influences. Moisture will fluctuate some, but the atmosphere will
likely remain too stable for thunderstorm coverage to be anything
but limited.

&&

.CLIMATE...

        Record Daily Maximum Temperatures

Date   Phoenix AZ  |   Yuma AZ   |  El Centro CA
----  -----------      -------      ------------
7/10  115 in 1958  | 118 in 1959 |  116 in 2012
7/11  118 in 1958  | 118 in 1958 |  117 in 1975
7/12  115 in 2009  | 119 in 1939 |  118 in 1964
7/13  114 in 2005  | 115 in 1983 |  118 in 1939

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Monday for AZZ537-540>544-
     546-548>551-560.

     Excessive Heat Warning from 10 AM Saturday to 8 PM MST Monday
     for AZZ530>536-538-539-545-547-552>559-561>563.

CA...Excessive Heat Warning from 10 AM Saturday to 8 PM PDT Monday
     for CAZ560>570.

&&

$$

DISCUSSION...Feldkircher/Hirsch
AVIATION...Percha/Smith
FIRE WEATHER...Feldkircher
CLIMATE...MO

NWS PSR Office Area Forecast Discussion