Area Forecast Discussion
Issued by NWS Tucson, AZ
FXUS65 KTWC 232246
Area Forecast Discussion
National Weather Service Tucson AZ
345 PM MST SAT JUL 23 2016
.SYNOPSIS...Isolated to scattered thunderstorms will occur mainly
east to south of Tucson this evening. An increase in deeper moisture
will then result in an upswing in thunderstorm activity during the
upcoming week. Daytime temperatures will generally trend a few
degrees above normal during the upcoming week.
.DISCUSSION...Isolated showers and thunderstorms were occurring
across the White Mountains north of Clifton, and further south
across the Chiricahua Mountains in eastern Cochise County at this
time. Otherwise, clear skies prevailed across western Pima County
with mostly clear skies elsewhere. For this forecast issuance, have
given strong preference toward the 23/12Z Univ. of AZ WRF-NAM and
WRF-GFS for the evolution of showers/tstms thru Sunday afternoon,
versus several HRRR solutions which seem to be considerable too
aggressive with shower/tstm potential this evening.
Expect isolated to scattered showers/tstms this evening east-to-
south of Tucson, with the greatest coverage/highest PoPs to occur
across the White Mountains. With the lack of an apparent forcing
mechanism aloft, the bulk of any showers/tstms should end by around
midnight. For now, will continue with a slight chance of showers/
tstms late tonight/early Sunday morning near the mountains east of
Tucson. A similar coverage pattern of showers/tstms should occur
The 23/12Z NAM/GFS were somewhat similar with depicting an upswing
in showers/tstms Sunday night into Monday. Although moisture/
stability values will remain similar to this afternoon/evening,
these solutions appear to be latching onto a weak inverted trough
presently over south Texas. As this system approaches from the
southeast Sunday evening, upper forcing in combination with adequate
moisture may be sufficient to provide at least isolated coverage of
showers/tstms Sunday night/Monday morning, then scattered to perhaps
numerous showers/tstms Monday afternoon/evening.
Thereafter, the GFS/ECMWF/CMC were similar with depicting a quasi-
stationary upper high centered over southern Utah/northern Arizona
Tuesday thru next Saturday. Based on these solutions, there appears
to not be a discernible "up-day" or "down-day" during that period.
Thus, the scenario of scattered afternoon/evening showers/tstms, and
a slight chance of late night/early morning showers/tstms will
High temps Sunday are forecast to moderate about 2-6 degs or so
versus this afternoon, then daytime temps will trend close to
seasonal normal or a few degs above normal Monday into next Saturday.
.AVIATION...VALID THRU 25/00Z.
Few-sct clouds at 8-12k ft agl with isolated to scattered SHRA/TSRA
mainly east and south of KTUS and near terrain this afternoon and
evening. Brief wind gusts to 40 kts and MVFR conditions are possible
with the stronger TSRA. Outside of thunderstorm wind gusts, sfc wind
will be nwly at 8-12 kts with higher gusts through the Gila Valley
near KSAD into this evening, with light and terrain driven winds
overnight. Better chances for SHRA/TSRA at all terminals will occur
on Sunday. Aviation discussion not updated for TAF amendments.
.FIRE WEATHER...Isolated to scattered thunderstorms will occur mainly
east and south of Tucson into this evening. Greater coverage of
thunderstorms will then occur Sunday into next weekend. Outside of
gusty thunderstorm outflow winds, 20-foot winds will generally be
terrain driven and less than 15 mph. The exception will be the Gila
River Valley, where northwesterly winds around 20 mph with higher
gusts are possible.
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