Area Forecast Discussion
Issued by NWS Tucson, AZ

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550
FXUS65 KTWC 192120
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
219 PM MST MON SEP 19 2016

.SYNOPSIS...Increasing moisture from the south should provide a
return of some showers and thunderstorms this week, especially
Tuesday into Wednesday. A low pressure system moving through the
Great Basin and into Arizona will bring another chance of rain and
cooler temperatures this weekend into early next week.

&&

.DISCUSSION...Moisture associated with tropical system Paine located
well west of the tip of Baja early this afternoon will continue to
stream northward into Arizona tonight and Tuesday. Clouds have
already been on the increase with regional radars detecting rainfall
just south of the International border. Recent model solutions
suggested that showers will start to develop and spread into
southern sections of the CWA this evening and tonight with the
initial moisture advection. Deeper moisture will move into the
region Tuesday, with more widespread showers and isolated
thunderstorms developing. Lingering moisture will interact with the
tail end of the system moving into the Great Basin around Thursday.
This will keep a chance of rain in the forecast through at least
Friday, mainly east of Tucson. Both the ECMWF and GFS models drop
this system farther south into Arizona over the weekend with rain
chances possible into early next week along with cooler
temperatures.

&&

.AVIATION...Valid through 21/00Z.
BKN-OVC clouds mainly above 15k ft AGL from KTUS/KOLS westward this
afternoon with SCT-BKN clouds north and east of KTUS becoming BKN-
OVC by early this evening. Some lower ceilings around 8-12k ft AGL
are expected to move in from south to north later this afternoon and
this evening. Isol`d to sct -TSRA/-SHRA will then push N/NE across
the international border this evening through Tuesday. Terrain
driven sfc wind becoming WLY-NWLY at around 10-15 kts this afternoon
becoming light and terrain driven mainly 10 kts or less through
Tuesday. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Increasing moisture is moving into the region
which will help bring isolated to scattered showers and a few
thunderstorms starting this evening, then continuing area-wide
Tuesday and Wednesday. A slight chance of showers and thunderstorms
will persist from Tucson eastward Thursday and then mainly east of
Tucson on Friday. Mostly dry for the upcoming weekend, but a slight
chance of showers and thunderstorms mainly for the mountains as
another weather system moves in from the north. 20-ft winds will be
mainly terrain driven at 15 mph or less through Wednesday, with
westerly to southwesterly breeziness developing Thursday and Friday
afternoons.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

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