Heat in Arizona, August 8, 2020

Area Forecast Discussion...corrected
National Weather Service Tucson AZ
920 AM MST Sat Aug 8 2020

...corrected issuance line...

.SYNOPSIS...High pressure over the region will continue to
maintain above average heat. Below average daily thunderstorm
chances will also continue, primarily well south and east of
Tucson as a drier southwesterly flow limits thunderstorm coverage
into at least the first half of next week.

&&

.DISCUSSION...Clear skies prevailed across most of southeast Arizona
this morning, with just some scattered mid level clouds across far
western Pima county in the vicinity of Why and Ajo. Dewpoints ranged
from the mid 40s to the mid 50's across southern Arizona. The KTWC
200808/12Z sounding showed 1.09" PW and not much in the way of CAPE,
with southwest flow at the mid and upper levels. In fact, expect
drier air to our west to mix into western and northern portion of
the forecast area as the day wears on with the prevailing southwest
flow. In other words, not much in the way of shower and thunderstorm
development is expected today across most of southeast Arizona, with
isolated showers/thunderstorms confined primarily southeast of a
line from Nogales to Safford to Hannagan Meadow in axis of slightly
deeper moisture.

Otherwise, daytime highs today will top out well above normal with
mid to upper 90s across Santa Cruz/Cochise counties, 101-105 in the
lower elevations of Graham, eastern Pima and Pinal counties and 105-
109 across central/western Pima county. These high temperatures are
6-9 degrees above normal.

&&

.AVIATION...Valid through 09/18Z.
Mostly clear. Isolated -TSRA/-SHRA mainly east of a KOLS to KSAD
line after 08/21Z. Normal surface wind trends less than 12 kts.
Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Drier than normal with well above average heat
through next week. In general, afternoon valley RHs will be in the
10-20 percent range with mountains in the 20-30 percent range. A
few afternoon thunderstorms possible near the mountains east and
south of Tucson. Normal diurnal wind trends outside of any
possible thunderstorm gusts.

&&

.PREV DISCUSSION...An unfavorable pattern with weak troughiness near
the west coast and a ridge of high pressure nosing in from the
east will continue to limit our moisture. Well below average dew
points in the 40s and precipitable water values hovering around 1
inch just won't cut it. We'll see another round of isolated
thunderstorms mainly near the eastern mountains today, with
temperatures several degrees above average. Even northern and
northwest Sonora has seen some drying over the past 24 hours.

Ensembles are still showing a strengthening of the ridge's
western flank over our area the next few days, which will continue
to tend to block any deep import of moisture while pushing
temperatures as high as 6 or 7 degrees above average to start the
new week. That trend could add another few degrees by the end of
next week, and push us into widespread Excessive Heat levels. We
probably won't see a more favorable pattern for thunderstorms
until the second half of August.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...None.

&&

DISCUSSION...Zell
PREV DISCUSSION...Meyer

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