Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 221653

Area Forecast Discussion
National Weather Service Tucson AZ
952 AM MST MON AUG 22 2016

.SYNOPSIS...Expect isolated afternoon and evening showers and
thunderstorms today. A drying trend will then limit thunderstorms to
mainly east of Tucson by Thursday. Isolated to scattered afternoon
and evening thunderstorms should return by next weekend. High
temperatures will generally be within a few degrees of normal into
next weekend.


.DISCUSSION...Water vapor imagery and 22/12Z upper-air plots show a
large area of low pressure over western Canada with disturbances
rotating around the base of the upper low across western Colorado
westward into central California. High pressure resides over the
eastern Pacific waters several hundred miles west of the Baja Spur.
This set up is resulting in generally zonal flow across the Desert
Southwest. A swath of dry mid to upper level air can be seen in WV
imagery across the eastern Pacific, extreme southern California and
into the southern half of Arizona and southwestern New Mexico.

The 22/12Z KTWC sounding revealed a PW of 1.10 inches, which is down
0.13 inches from 21/12Z and down 0.40 from 22/00Z. In addition, CIRA
LPW Total Imagery shows values ranging from 0.6-1.0 around the
Tucson area, with similar values to the south and east, while values
ranging from 1.1-1.5 reside over southwestern Arizona and the
northern Gulf of California.

The 22/06Z run of the Univ of AZ WRF/NAM & GFS did a fairly decent
job in depicting the convection across south central New Mexico from
late last night into early this morning, but seemed to hang on to
the storms a bit too long. At any rate, for this afternoon both
models show very little activity across my forecast area, mostly
over the White mountains and just isolated in nature. The inherited
POP forecast reflects this to some degree, although POP values may
be a tad too high given the aforementioned model solutions. Will
continue to monitor satellite and radar trends and will make
adjustments as needed.

As of 16Z (9 AM MST), temperatures across the region ranged from the
mid 70s to the lower 80s, with the Tucson Intl Airport reporting a
temp of 78 degs, after a morning low of 67 degs. These readings seem
to be on track with the expected afternoon high temps, but will
continue to monitor.


Scattered cloud decks around 10k-14k ft msl. Looking at isold
-TSRA/-SHRA this aftn and early evening. Surface wind generally less
than 12 kts. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Expect isolated thunderstorms this afternoon and
evening. A drying trend from west-to-east will occur Tuesday through
Thursday, with only isolated thunderstorms mainly near mountains
east of Tucson by Thursday. Then a bit of an increase in storm
coverage is expected again Friday and Saturday due to an increase in
monsoon moisture. 20-foot winds into next weekend will generally be
terrain driven at less than 15 mph except near thunderstorms.


.PREV DISCUSSION...Outside of the White Mountains, thunderstorm
activity Tuesday and Wednesday will be rather limited as the upper
level trof pushes across the area late Tuesday into Wednesday.
Moisture starts to return to the area Friday into the weekend for a
slight uptick in thunderstorms. High temperatures generally around
normal this week.





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