Area Forecast Discussion
Issued by NWS Tucson, AZ
FXUS65 KTWC 240416
Area Forecast Discussion
National Weather Service Tucson AZ
916 PM MST SAT JUL 23 2016
.SYNOPSIS...Isolated showers and thunderstorms will occur mainly
east and southeast of Tucson toward the New Mexico border 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...IR satellite imagery shows most of the cloudiness and
associated convection over northeast Arizona and northwest New
Mexico, but still a few lingering cells mainly over parts of Graham
and Cochise counties, but these are dying as well. A more expanded
look at IR imagery shows a thunderstorm complex over southern Sonora
Mexico. With this system so far to the south, not expecting any
significant push or surge of moisture from outflows, but can`t rule
out some isolated activity regenerating overnight in response to
this system well to our south. That said, will keep just a slight
chance of showers/thunderstorms in the forecast overnight, mainly
along the border with Mexico as well as over the White mountains for
the potential of activity that may fire up in west central New
Mexico affecting that area as well.
As of 04Z (9 PM MST), temperatures across the region ranged from the
mid 80s to the upper 90s, with the Tucson Intl Airport reporting a
temp of 97 degs after an afternoon high of 106 degs, which was 7
degs above normal for this date. These current readings seem to be
on track with the inherited/expected overnight low temps, but will
continue to monitor.
See the previous discussion below for details beyond tonight.
.AVIATION...VALID THRU 25/06Z.
Few-sct clouds at 8-12K FT AGL with isolated -SHRA/TSRA mainly east
and southeast of KTUS and near terrain the remainder of this
evening, with a decrease in activity after midnight. Expect west to
northwest winds ranging from 12-18 kts with gusts to around 20-25
kts Sunday afternoon. Stronger and gusty winds expected near any
thunderstorms that develop. Slightly better chances for SHRA/TSRA at
all terminals on Sunday, but still just isolated to scattered in
nature. Sct to locally bkn ceilings of around 8-12K FT, with lower
ceilings near thunderstorms Sunday afternoon. Aviation discussion
not updated for TAF amendments.
.FIRE WEATHER...Isolated to scattered thunderstorms will occur mainly
east and southeast of Tucson this evening, with little activity
after midnight. 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.
.PREV DISCUSSION...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 considerably 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.
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