Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 172053

Area Forecast Discussion
National Weather Service Tucson AZ
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 SE AZ.

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 SE AZ 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-SCT clouds 9-13K ft agl until dark, mainly clear
skies will prevail through tonight. SCT-BKN clouds 7-10k ft are
forecast Fri afternoon when an isold TSRA 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.






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