Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 082048
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
148 PM MST Sat Aug 8 2020

.SYNOPSIS...
Above normal temperatures and dry conditions are expected through
next week. Daily highs across the lower deserts will mainly top
out between 109 and 112 degrees with overnight lows near seasonal
normals. This stagnant and unusually dry weather pattern is
expected to last through at least next week.

&&

.DISCUSSION...
Current visible satellite shows few thunderstorms within a field of
cumulus north of the Rim. The Cu field extends south into portions
of Gila County where a few afternoon thunderstorms are possible today.
The most aggressive outcome from the High Resolution Ensemble Forecast
System shows a fair amount of activity across the higher terrain north
and east of Phoenix with a few storms even attempting to develop within
Maricopa County. However, most areas, including Greater Phoenix, are
not likely to see any rain. The high temperature so far at Sky Harbor
has been 108 degrees which means there is a very good chance today
we could see our 33rd day with a high temp of at least 110 degrees.
The record for most such days in a year is 33 and was set in 2011.

Overall, dry and hot conditions will be the rule this week as the
subtropical ridge migrates westward from western Texas to northern
Sonora. This location is not favorable for thunderstorms in the lower
desert with most of the moisture remaining well to the south. Instead,
increasing atmospheric heights as the ridge moves closer to Arizona
will translate into even hotter temperatures. Forecast highs across
much of the lower desert are around 110-113 degrees most days this
week, which is about 5-8 degrees above seasonal normals. This will
produce a high heat risk nearly everyday, and an Excessive Heat
Warning remains in effect Sunday/Monday for the Phoenix area and the
lower elevations of Gila County to highlight the days with the highest
anticipated heat risk. This warning could very well be extended
through much of next week if temperatures remain constant or increase.

By late next week, ensemble guidance places the H5 center of the
ridge over eastern Arizona closer to the Four Corners area.
This progression would be a step in the right direction for more
convection over the lower desert, but not as promising as if the high
could reach a little closer to the Four Corners. Still, this setup
could facilitate better moisture advection into Arizona. Forecast
trends for rain late in the forecast remain relatively optimistic
compared to recent days with PoPs nearing 5-10% next Friday and
Saturday. While these numbers are not usually worth much attention,
the trends are at least pointing to a better direction.

&&

.AVIATION...Updated at 1742Z.

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

No aviation impacts expected through the TAF period. Winds will
continue to exhibit typical diurnal tendencies over the next 24
hours with sustained speeds mostly below 10kt becoming light and
variable at times. Light and variable winds this morning will take
on a west to southwest component around 19Z-20Z. Skies will remain
clear to mostly clear through the period with only a few mid-level
clouds around 10 kft or above.

Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation impacts expected through the next 24 hours. Winds
will be fairly light through the period favoring a westerly wind
at KIPL and a southerly wind at KBLH. Some afternoon gustiness
will be possible at KBLH with gusts up to 20 kts. Winds may
become light and variable at times at both TAF sites, especially
during the morning and overnight hours. Skies will remain clear
through the period.

&&

.FIRE WEATHER...
Tuesday through Saturday:
Most days will be hot and dry. Minimum humidity values will drop
below 15% for almost everywhere while overnight recoveries will
struggle reach the 20-30% range. Winds will generally follow
typical diurnal/terrain influences at light and some typical
afternoon breezes. Thunderstorm activity will be very limited,
and non existent through the first half of the week. Increasing
moisture by Friday/Saturday looks better which may be enough for
isolated thunderstorms to form over the higher terrain north and
east of Phoenix.

&&

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

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning from 9 AM Sunday to 8 PM MST Monday for
     AZZ537-540-542>544-546-548-550-551-556-560-562.

CA...None.
&&

$$

DISCUSSION...AD
AVIATION...Smith/Kuhlman
FIRE WEATHER...AD



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