Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 161537

Area Forecast Discussion
National Weather Service Tucson AZ
837 AM MST Sat Sep 16 2017

.SYNOPSIS...Isolated to scattered afternoon and evening
thunderstorms mainly east to south of Tucson into the middle of next
week. Daytime temperatures will remain near seasonal normals through
Monday followed by cooler temperatures by midweek.


.DISCUSSION...Mostly sunny skies across southeast Arizona this
morning. Still quite a bit of boundary layer moisture hanging around
with the 12Z KTWC sounding coming in with a PWAT of 1.01 inches.
Quite dry above 700 mb and some of this drier air will mix down
today with PWAT values expected to drop to 0.75" to 1 inch with the
highest values southeast of Tucson. Even with the drier air, given
the southwesterly flow aloft, cool mid level temperatures and modest
lift ahead of a weak shortwave, a very isolated shower or
thunderstorm mainly east of Tucson can`t be ruled out this

We`re still keeping an eye on Hurricane Norma situated to the south
of the Baja peninsula. However, all indications per NHC and various
model guidance is that Norma will weaken later this upcoming week
off the western coast of the southern Baja peninsula. It will be
close enough to influence our moisture as south to southwesterly
flow continues across the area but certainly no direct impacts this
far north. With that said, there will be a slight chance of showers
and thunderstorms for much of the upcoming week mainly to the south
and east of Tucson. In addition, with the broad troughiness in the
western CONUS, expect some afternoon breezes as well. Temperatures
will be near normal through about midweek, then cool off to slightly
below normal values at the end of the work week.


.AVIATION...Valid thru 17/18Z.
Clear skies west of KTUS with FEW-SCT clouds at 5k-8k ft AGL east
and south of KTUS. Isolated -TSRA/-SHRA this afternoon and evening
mainly east and south of KTUS. SFC wind variable in direction and
less than 10 kts thru 16/17Z. SFC wind between 16/17Z and 17/03Z
sly/swly at 8-14 kts with some gusts to near 20 kts. Diminishing SFC
wind aft 17/03Z. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Expect isolated afternoon and evening showers and
thunderstorms mainly east to south of Tucson into the middle of next
week. Dry conditions with cooler daytime temperatures will then
occur late next week. A deepening upper trough over the western
states may bring gusty winds late next week as well.






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