FXUS65 KTWC 251032

Area Forecast Discussion
National Weather Service Tucson AZ
330 AM MST Sun Aug 25 2019

.SYNOPSIS...Expect limited thunderstorm activity through Tuesday as
high pressure builds overhead. The drier pattern will also bring
hotter temperatures, especially by Tuesday. A more favorable flow
with adequate moisture will provide scattered mainly afternoon and
evening thunderstorms Wednesday into next weekend.


.DISCUSSION...Upper ridge axis extended from central California
southeastward into northeast Sonora/northwest Chihuahua Mexico early
this morning. The 25/00Z upper air plots initialized a 500-300 mb
anticyclonic gyre over southern Pinal County northwest of Tucson.
Various 25/00Z high-resolution models suggest shower and
thunderstorm initiation early this afternoon will be quite limited
across this forecast area.

Given the aforementioned upper features and based on these
solutions, expect only isolated showers/tstms this afternoon and
perhaps into early this evening favoring locales south-to-southwest
of Tucson. Any showers/tstms should end shortly after sunset. Expect
dry conditions across much of the area Monday as the upper high
pressure is progged to remain overhead. If any showers/tstms develop
Monday afternoon, the favored locations at this time are the
Chiricahua Mountains followed by the White Mountains. Various 25/00Z
models then suggest isolated showers/tstms mainly near eastern/
southern mountains Tuesday afternoon and evening.

Thereafter, the 25/00Z GFS/GEFS and ECMWF/EPS were similar with
depicting consolidation of the upper high to occur by midday
Wednesday generally over southern California. The upper high is
progged to remain quasi-stationary Thursday into Friday before
moving northeastward toward the Las Vegas, Nevada vicinity by

Have noted that these solutions generally were not quite as robust
with the expected return of showers/tstms later this week versus the
same solutions from 24 hours ago. However, the progged flow regime
and various moisture fields still suggest that scattered mainly
afternoon and evening showers/tstms should return Wednesday and
continue into next weekend.

Regarding daytime temps, expect a warming trend to occur into
Tuesday in response to high pressure ridge aloft and a gradually
drier environment. The hottest temps during this forecast package
still appear most likely Tuesday, and temps Wednesday will likely
only be just a degree-or-two lower for much of the area. There is
the potential for an Excessive Heat product to eventually be issued
for portions of the area, especially Tuesday. Thereafter, daytime
temps are forecast to moderate closer to late August normals
Thursday into Saturday.


.AVIATION...Valid through 26/12Z.
Isolated -TSRA/-SHRA after 19Z today and into early this evening
south to southwest of KTUS. Forecast confidence too low at this time
to include VCTS at KOLS and thus will defer this notion to the next
shift. Any -TSRA/-SHRA expected to end by 05Z Monday. Otherwise,
cloud decks mainly 10k-15k ft MST. Surface wind mostly variable in
direction and under 12 kts. The exception is vicinity KSAD this
afternoon/evening with nwly surface wind 12-18 kts with gusts near
25 kts. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Isolated thunderstorms this afternoon mainly south
to southwest of Tucson. Expect dry conditions across much of the
area Monday into Tuesday, although isolated thunderstorms especially
Tuesday afternoon near eastern and southern mountains. A favorable
flow pattern with adequate moisture will provide scattered mainly
afternoon and evening thunderstorms Wednesday into next weekend.
Aside from thunderstorm wind gusts, 20-foot winds will be terrain
driven mainly under 15 mph.






Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson

NWS TWC Office Area Forecast Discussion