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Area forecast discussion 
National Weather Service Tucson Arizona
330 am MST Monday Sep 1 2014

Synopsis...hot and dry conditions will occur today followed by a
few thunderstorms near the international border Tuesday afternoon.
Thereafter...the chance of thunderstorms will increase Wednesday
into this weekend as moisture increases across the area.

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Discussion...upper level ridge axis extended from west of the northern
Baja California California coast southeastward into southern Texas early this morning.
Abundant sunshine will occur again today with a few to scattered
cumuloform clouds this afternoon mainly across eastern sections. Clear
skies or mostly clear skies will prevail tonight into Tuesday
morning.

01/00z GFS/ECMWF/Canadian were similar with depicting high pressure
aloft to be centered over southern New Mexico Tuesday afternoon. Some
increase in moisture will happen across northern Sonora Mexico...and a
few showers/thunderstorms may occur as far north as the international border
adjacent Cochise County Tuesday afternoon. Given that the GFS/ECMWF/
Canadian solutions were further south with quantitative precipitation forecast/S versus previous
solutions...have opted for precipitation-free conditions across all of this
forecast area Tuesday afternoon and Tuesday night.

Lower and middle-level moisture is prognosticated to increase Wednesday with deeper
moisture to increase into the upcoming weekend. There were some
differences between the 01/00z GFS/European model (ecmwf) solutions regarding the
extent of moisture to occur later this week and this weekend. In
essence...the European model (ecmwf) depicted more-robust moisture fields versus the
GFS thur-Fri. Thereafter...the GFS depicted more-robust moisture
fields versus the European model (ecmwf)...especially regarding qpf/S...by sun.

The reason for this latter difference appears to be due to the GFS
depicting the next eastern Pacific tropical system to be considerably
closer to the southern Baja California California coast late this weekend versus the
European model (ecmwf) position of this tropical system. Based on these solutions and
especially the GFS...have increased probability of precipitation for this weekend. The
upshot during the Wednesday-sun period...expect increasing chances of
showers/thunderstorms as moisture increases across Southeast Arizona.

High temperatures today-Thursday will generally average about 3-6 degrees f above
normal area-wide followed by a pronounced cooling trend this weekend.

&&

Aviation...valid through 02/12z.
Expect clear skies most sections this morning followed by a few to
scattered clouds at 8-12k feet above ground level mainly east of ktus this afternoon
and early this evening. Clear skies should then prevail across much
of the area late tonight into Tuesday morning. Surface wind will be
mainly less than 10 kts into Tuesday morning...except for occasional
gusts to around 20 kts this afternoon. Aviation discussion not
updated for taf amendments.

&&

Fire weather...dry conditions with above normal temperatures will
occur today. There is a slight chance of thunderstorms near the
international border adjacent Cochise County Tuesday afternoon.
Thereafter...increasing chances of thunderstorms will prevail
Wednesday into next weekend as moisture increases across the area.
20-foot winds will be southwest to west at 10 to 15 miles per hour during the
afternoon hours through Tuesday. Gusty outflows associated with
thunderstorms may then occur during the latter part of the week.

&&

Twc watches/warnings/advisories...none.

&&

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Francis

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