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Area forecast discussion 
National Weather Service Tucson Arizona
855 am MST Tuesday Jul 7 2015

Synopsis...a gradual drying trend will prevail during the next
several days. However...there will still be enough moisture to
support isolated to scattered afternoon and evening thunderstorms
mainly east of Tucson. Some increase in shower and thunderstorms
will then occur this weekend and early next week. High temperatures
will generally average a few degrees below normal into this weekend.

&&

Discussion...visible satellite imagery shows mostly sunny to partly
cloudy conditions across most of the County Warning Area this morning. While surface
observations reveal relatively little change in the low-level
moisture field from 24 hours ago with dewpoints generally in the
lower 60s f...the 12z ktwc sounding tells a different story aloft
with continued drying above about 550 mb. As a result...the
precipitable water value was 1.47 inches...a decrease of 0.15 inch
versus 24 hours ago.

The most recent 15z Storm Prediction Center mesoanalysis nicely shows the continued
gradual drying...most notable out west...with a northwest-southeast
oriented 850 mb moisture gradient now through western Maricopa and
central Pima counties. Based on this gradient location and the
precipitation coverage observed yesterday...feel showers and storms
should occur a bit farther east than yesterday...with the
demarcation area around central Pima County. This matches up nicely
with the morning runs of various hi-res models such as the 14z
hrrr...and 06z suite of the University of Arizona wrfs. As such...have
adjusted the inherited pop grids to reflect isolated shower and
storm coverage to reflect this latest thinking. No other changes to
the going forecast at this time.

&&

Aviation...valid through 08/18z.
Isolated to scattered -tsra/-shra will prevail mainly east of kgxf-
kols line this afternoon and evening. Local MVFR conditions and
brief wind gusts of 25-35 kts may accompany the stronger thunderstorms and rain. Few-
scattered clouds this morning becoming scattered-broken with bases 5-9k feet above ground level
after 08/18z. Surface wind will generally be less than 10 kts apart
from thunderstorm influences. Aviation discussion not updated for
taf amendments.

&&

Fire weather...isolated to scattered showers and thunderstorms are
expected from Tucson eastward...although there is enough lingering
moisture to bring a risk for isolated showers and storms to parts of
central Pima County today. Wednesday through Friday...expect a low
grade monsoon pattern with isolated to scattered showers and
thunderstorms generally from Tucson eastward and mainly dry
conditions west of Tucson. Some increase in thunderstorm activity
should occur this weekend and early next week. Generally light
terrain driven winds will occur outside of thunderstorm influences.

&&

Previous discussion...the intrusion of drier air will lead to an
overall decrease in thunderstorm activity this week. Still expecting
a enough moisture to support isolated thunderstorms...mainly in the
mountains. The latest GFS and European model (ecmwf) track the low pressure system
into the Great Basin late Thursday. Thereafter...a more southerly
flow develops over the region with deeper moisture working back into
Arizona for an upswing in thunderstorm activity this weekend into
early next week. High temperatures will trend close to normals today
and Wednesday...followed by a slight cooling Thursday and Friday
before returning to above normal readings this weekend.

Twc watches/warnings/advisories...none.

&&

$$

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Carlaw

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