fxus65 ktwc 172053 

Area forecast discussion 
National Weather Service Tucson Arizona 
153 PM MST Thu Aug 17 2017 

Synopsis...dry weather will continue into Friday. A moisture 
increase from the south will gradually bring isolated to scattered 
thunderstorms back to Southeast Arizona this weekend and 
especially early next week. High temperatures within a few degrees 
of normal will prevail through the weekend. 


Discussion...focus of the forecast is the return of moisture and 
thunderstorms to Southeast Arizona. 

Current surface obs show dew points in the 30s and 40s with a few 
cumulus clouds over mountains. Better moisture is south of the 
border with thunderstorms occurring from central Sonora/Chihuahua 
southward. Upper trough/low over California will not move a lot 
through this weekend, but the upper ridging/high pressure 
stretching from nrn Mexico to the Gulf of Mexico will become 
reoriented farther north into Texas. This will allow increased 
southerly flow between the low to our west and high to our east 
and a resultant moisture transport northward into Southeast Arizona. 

Initially, it looks like the axis of deepest moisture will be over 
New Mexico or perhaps far eastern AZ, but storms should form on 
the western edge of this axis this weekend, triggered by a series 
of disturbances in the the southerly flow. Southern and eastern 
areas will have the best chances for rain. As moisture continues 
to stream in, the axis of best moisture should shift westward 
early next week with 1.5+ inch precipitable water values indicated 
over Southeast Arizona Monday night through Wednesday. Thus, rumors of the 
demise of our monsoon have been greatly exaggerated. 

A relatively large difference between daytime highs and nighttime 
lows will only continue another day or two for most areas before 
the diurnal range Narrows as is typically the case during an active 
monsoon time frame. 


Aviation...valid thru 19/00z. 
Other than a few-scattered clouds 9-13k ft agl until dark, mainly clear 
skies will prevail through tonight. Scattered-broken clouds 7-10k ft are 
forecast Fri afternoon when an isold thunderstorms and rain could occur near the New 
Mexico line. Expect normal diurnal wind trends less than 12 kts. 
Aviation discussion not updated for taf amendments. 


Fire weather...dry weather will continue into Friday. Isolated 
to scattered showers and thunderstorms will return this weekend 
into early next week. 20-foot winds will generally be terrain 
driven at less than 15 mph apart from any thunderstorm outflows. 


Twc watches/warnings/advisories...none. 


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