Area forecast discussion 
National Weather Service Tucson Arizona 
315 am MST Tuesday Sep 1 2015 

Synopsis...after some lingering showers and thunderstorms 
in the early morning hours...storm coverage will be less 
across portions of the area hit the hardest last night. 
An impulse from the south will enhance storm coverage again 
Wednesday into Thursday. Increasing moisture from the south will 
then keep a good chance of showers and thunderstorms into the 


Discussion...okay then. If you take a look at water vapor imagery 
we saw a big complex through Sonora late yesterday afternoon...with 
influence from the northern periphery impacting our area in the 
late afternoon and early evening. As this occurred...a small but 
very strong complex that developed even further north near 
Phoenix and Gila County can be seen sending a Gravity 
wave to the southwest and south between 04z-07z. This intersected 
with a remnant shear axis created by the earlier complex and fired 
the persistent and widespread thunderstorm area through eastern Pima 
County late last night and early this morning. 

After that show (which is finally diminishing) it will be very 
difficult to manage a strong enough trigger for widespread storms in 
Santa Cruz Valley...including Tucson metropolitan this afternoon. Favored 
locations will be on the eastern periphery of last night's 
action...primarily Cochise and Santa Cruz County. 

For Wednesday through the weekend...the modest southwesterly flow 
between the trough to our northwest and ridge to our east will be 
be able to tap into a long fetch of moisture. With tropical 
activity heating up again off the West Coast of Mexico (hello 
tropical depression 14-E...soon to become kevin)...we'll head into 
September watching for tropical influences pushing up from the 
south. An impulse embedded in the flow will help organize storms 
Wednesday into Thursday. After that we'll see what else Cooks up for 
US from that general direction this weekend. 


Aviation...valid through 02/12z. 
Scattered -tsra/-shra mainly NE of ktus this morning. 
Otherwise...vicinity expect scattered -tsra/-shra mainly east 
and southeast ktus this afternoon and evening. Brief MVFR conditions 
and gusty winds to 45 kts may occur with with the stronger 
thunderstorms. decks will generally range from 8- 
12k feet above ground level and surface wind will ge mostly less than 10 kts. 
Aviation discussion not updated for taf amendments. 


Fire weather...we will maintain enough moisture for a good chance 
of mainly afternoon and evening showers and thunderstorms into 
this weekend. For the most part storms will be decent rainers 
with wind gusts in the 25-45 miles per hour range...while a couple each day 
will be stronger. Through much of the coming week winds will be 
light with a west to southwest 10-15 miles per hour breeze each afternoon 
outside of thunderstorm outflows. 


Twc watches/warnings/advisories...none. 




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