Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 212258

Area Forecast Discussion
National Weather Service Tucson AZ
358 PM MST Thu Sep 21 2017

.SYNOPSIS...A low pressure system will bring strong and gusty
winds each afternoon through the weekend. A few showers or
thunderstorms may proceed the system, but activity should remain
very isolated. Cooler temperatures will arrive Friday, with readings
holding below average through at least the middle of next week.


.DISCUSSION...Winds have picked up about as expected this
afternoon as a trough digs into the region from the northwest.
Most of our area will be a little stronger tomorrow, but still
under wind advisory levels (sustained 30 mph winds are needed). On
Saturday the focus will be ahead of the front with mainly eastern
areas emphasized. Wind prone locations in Cochise county may reach
advisory levels Saturday afternoon, but it shouldn`t be very

Temperatures today have been similar to yesterday,ahead of height
falls bringing few degrees of cooling tomorrow. Some cool air
advection associated with the trough will drop temperatures
several degrees below average for late September over the weekend.
That means widespread 80s for daytime highs. Overnight lows
Sunday morning and Monday morning generally in the 50s from Tucson
into the lower deserts, and 40s in cooler eastern valleys. One or
two coldest valley spots could see upper 30s Monday morning with
freezes possible in a few higher mountain locations.

Medium range operational models and ensembles are pretty
consistent in leaving modest low pressure behind over the desert
southwest as higher latitude support lifts into the northern
plains early next week. That would tend to retard any warming
trend next week while also tapping into a little moisture from the
southeast and east around the middle of the week. Any shower
activity that we might manage would be closer to the New Mexico

Even with the residual troughiness delaying things, we should see
high pressure build in from the west by later next week. An
amplified flow at day 10 hints at a chance of relatively hotter
temperatures to start October.


.AVIATION...Valid thru 22/23Z.
Generally SKC west of KTUS thru the period. FEW-SCT clouds at 8k-12k
ft AGL from KTUS eastward thru 22/04z and then again aft 22/16Z,
with SKC conditions between 22/04Z and 22/16Z. SFC wind mainly SWLY
at 15-20 kts with gusts to 30 kts thru 22/03Z. SFC wind diminishing
to less than 10 kts after 22/03z. SFC wind then increasing again aft
22/15Z, with SWLY SFC wind at 17-22 kts and gusts to around 30 kts
Friday afternoon. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...A deepening upper trough over the western United
States will result in gusty southwest winds, especially during the
afternoon and early evening hours through Saturday. The strongest
winds are expected through the early evening hours tonight and then
Friday, with a cooling trend Friday through Sunday. There will be a
slight chance of thunderstorms over the mountains in the eastern
portion of the state before drying out this weekend.






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