Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

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.




Visit US on at weather.Gov/Tucson

National Weather Service Glossary of Abbreviations