Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 152125

Area Forecast Discussion
National Weather Service Tucson AZ
225 PM MST Fri Sep 15 2017

.SYNOPSIS...Breezy to locally windy conditions again today, with
temperatures falling to near seasonal levels this weekend. A
potential moisture increase could bring expanding thunderstorm
coverage next week.


.DISCUSSION...Patchy drying continues today, but most spots are
managing to hold on to precipitable water values around 1 inch.
Just enough for isolated thunderstorms organized along weak
horizontal roll vortices oriented parallel to the direction of the
wind. Temperatures down another few degrees with the height and
thickness values continuing to retreat. Similar conditions into
the weekend with a little less wind as the new mean trough
position through much of the West dominates.

Tropical storm Norma was around 18.9N 110.1W this afternoon,
still showing very slow movement to the N/NW. Still not much
steering flow for the storm right now, but she will eventually
catch on to the far western flank of the ridge redeveloping from
central Mexico through Texas and southeastern states. Ultimately
no threat to hit us, but we`ll keep an eye on the associated
moisture fields and potential moisture surge activity generated by
the storm. As it was this morning, timing and track are still a
huge issue with some moisture very likely being pushed in this
general direction. Still focusing on areas southeast and east of
us early to mid next week for the bulk of the deepest remnant
moisture, with mainly eastern portions of our area affected.


.AVIATION...Valid thru 17/00Z.
SCT clouds at 10k-14k ft AGL with isolated -TSRA/-SHRA mainly E
of KTUS through 16/03Z. Gusty SLY/SWLY SFC wind at 13-20 kts with
higher gusts until 16/04Z, diminishing overnight with normal wind
trends generally under 12 kts Saturday. Aviation discussion not
updated for TAF amendments.


.FIRE WEATHER...There will be a slight chance of afternoon and
evening showers and thunderstorms mainly across the higher terrain
east of Tucson through Saturday. Increasing chances of showers and
thunderstorms will then occur areawide early next week as deeper
moisture moves northward. Gusty south to southwest winds again
today as a trough moves north of the area across the Great Basin.
Otherwise, 20-foot winds will generally be terrain driven at less
than 15 mph.






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