Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 222204
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
300 PM MST Thu Jun 22 2017

.SYNOPSIS...Very hot temperatures will continue into this weekend.
Dry conditions will also prevail for much of the area into Saturday.
A more favorable pattern will then provide scattered afternoon and
evening thunderstorms Sunday into the middle of next week.

&&

.DISCUSSION...Strong upper high was centered just northeast of
Tucson this afternoon. A few showers developed early this afternoon
across the White Mountains but most have since dissipated. Showers
and thunderstorms have also developed near the International border
adjacent southwest Cochise/southeast Santa Cruz Counties. Given the
position of the upper high, the flow aloft will translate into a
southwestward movement of these showers/tstms and away from this
forecast area. Thus, the official forecast depicts precip-free
conditions this evening and continuing into Saturday morning.

The 22/12Z GFS/ECMWF/CMC were in general agreement with depicting an
increase in the coverage of showers/tstms starting Saturday
afternoon. A chance of showers/tstms exists Saturday afternoon/
evening across the White Mountains, and a slight chance of
showers/tstms also exists mainly near mountains east-to-south of
Tucson.

A more extensive westward influx of deeper moisture is then progged
to occur Sunday into Monday as the upper high remains quasi-
stationary over the area. The ECMWF continued to be more robust
versus the GFS and CMC regarding the westward extent of the deeper
moisture. At any rate, chance-category PoPs exist for most locales
east-to-south of Tucson Sunday afternoon/evening, and a slight
chance of showers/tstms is also depicted as far west as the Tohono
O`odham Nation. Western Pima County is then included in a slight
chance of showers/tstms Monday afternoon/evening with similar PoPs
elsewhere as depicted Sunday.

Thereafter, these solutions were similar with depicting a very
gradual daily reduction in shower/tstm coverage Tuesday into next
Thursday. Although a gradual reduction in coverage should occur,
believe there will be enough moisture to justify a slight chance of
showers/tstms next Thursday generally from Tucson south-to-southeast
across Santa Cruz/Cochise Counties.

The Excessive Heat Warning continues until 7 pm MST Sunday for all
elevations below 5000 feet and the Baboquivari Mountains including
Kitt Peak. The Heat Advisory also continues until 7 pm MST Sunday
for all other mountain zones.

&&

.AVIATION...Valid thru 24/00Z.
Expect clear skies to scattered clouds at 10k-15k ft AGL into Friday
afternoon. Surface wind nwly 10-25 kts with gusts to 35 kts early
this evening and Friday afternoon. The strongest wind speeds will be
east of KTUS and particularly near KSAD. Surface wind variable in
direction less than 12 kts at other times. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...Dry conditions will prevail across much of the
area through Saturday. The exception is across the higher terrain
along the New Mexico border and the White Mountains where there is a
slight chance of thunderstorms. A more favorable pattern for
thunderstorms will then prevail Sunday through next Thursday. Expect
scattered afternoon and evening thunderstorms, especially east to
south of Tucson. However, the coverage of thunderstorms Monday into
Tuesday may expand further west to also include Fire Zone 150 west
of Tucson.

Otherwise, 20-foot winds will generally be terrain driven and less
than 15 mph. The exceptions are early this evening and Friday when
some gusty northwest winds will occur east of Tucson, especially in
the Upper Gila River Valley. The combination of the gusty winds and
minimum relative humidity values of 5 to 10 percent may create
critical fire weather conditions in the upper Gila River Valley, but
these conditions are not expected be widespread nor long-lived.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
 Heat Advisory until 7 PM MST Sunday for AZZ510>514.

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

&&

$$

DISCUSSION...Francis
AVIATION/FIRE WEATHER...Zell

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