Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 240433

Area Forecast Discussion
National Weather Service Tucson AZ
932 PM MST Fri Jun 23 2017

.SYNOPSIS...Very hot temperatures will continue this weekend.
Isolated to scattered thunderstorms will occur east of Tucson
Saturday afternoon, then scattered thunderstorms from Tucson
eastward Sunday into Tuesday. Expect less thunderstorm coverage with
temperatures lowering closer to seasonal normals late next week.


.DISCUSSION...Not much in the way of shower or thunderstorm activity
near the International Border today compared to yesterday. However,
models continued to show an increase in moisture tonight and more so
by Sunday for an upswing in thunderstorm activity this weekend.
Otherwise, very hot temperatures will continue through the weekend.
Current forecast looked in good shape, so no updates necessary this


.AVIATION...Valid thru 25/06Z.
Isolated -TSRA east of KTUS Saturday afternoon. Brief wind gusts to
40 kts may occur. Otherwise, VFR conditions into Saturday evening.
Surface wind less than 10 kts, then Saturday afternoon swly to nwly
5-15 kts with gusts to 20 kts. Aviation discussion not updated for
TAF amendments.


.FIRE WEATHER...Scattered thunderstorms generally from Tucson
eastward and southward Sunday into Tuesday. Expect decreasing
coverage of thunderstorms Wednesday, with isolated to scattered
thunderstorms mainly east to south of Tucson. Dry conditions are
forecast to prevail across much of the area next Thursday and Friday.

Otherwise, gusty east to southeast winds will likely occur Saturday
night into Sunday morning. The favored locales will be the Upper
Gila River Valley including Safford, and near the Tucson metro area.
20-foot winds will then exhibit diurnal trends with speeds mainly
less than 15 mph, although some stronger afternoon gusts to occur
due to daytime heating.


.PREV DISCUSSION...Strong high pressure aloft will remain centered
over southern Arizona this weekend. Various NWP models depict a
gradual westward import of somewhat deeper moisture into the area
starting Saturday and continuing into early next week. Expect
isolated to scattered thunderstorms Saturday afternoon and evening
east of Tucson. Scattered showers and thunderstorms should then
occur mainly from Tucson eastward and southward Sunday and Monday,
especially during the afternoon and evening hours.

Thereafter, the 23/12Z GFS/ECMWF deterministic solutions depict a
gradual decrease in thunderstorm coverage to occur starting Tuesday
and continuing into next Friday. Curious to note that the GFS is now
generally more-robust with model-generated liquid precip amounts
versus the ECMWF, which had been more-robust with liquid precip
amounts versus the GFS for several model cycles. This appears to be
due to a somewhat less amplified upper trough depicted by the GFS
over the western CONUS later next week, versus the now deeper upper
trough scenario depicted via the ECMWF.

At any rate, expect isolated to scattered showers/tstms mainly east
to south of Tucson Tuesday, then isolated to scattered showers/tstms
mainly south-to-southeast of Tucson Wednesday. A slight chance of
showers/tstms Thursday is then confined mainly to higher terrain
southeast of Tucson, with dry conditions area-wide next Friday.

Some adjustments to temperatures led to earlier expirations of
Excessive Heat Warnings and Heat Advisories for locales east of
Tucson versus previous product issuances. Please refer to the
Watches/Warnings/Advisories section of this Area Forecast Discussion
for detail. Otherwise, very hot daytime temperatures to continue
this weekend, then daytime temperatures will lower closer to
seasonal normals Wednesday into next Friday.



Excessive Heat Warning until 7 PM MST Saturday for AZZ508.

Heat Advisory until 7 PM MST Saturday for AZZ511-513.

Excessive Heat Warning until 7 PM MST Sunday for AZZ501>507-509-515.

Heat Advisory until 7 PM MST Sunday for AZZ514.



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