Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 250405
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
905 PM MST WED AUG 24 2016

.SYNOPSIS...Increasing moisture will help create better
thunderstorm coverage by Friday and Saturday.

&&

.DISCUSSION...Water vapor imagery continuing to look very similar to
yesterday at this time, with a trough axis that now extends across
western New Mexico, with high pressure centers on either side of
this trough. One is over the eastern Pacific waters west of the
central Baja peninsula, while the other is over the Dixie states.
Plenty of mid to upper level dry air can be seen over much of the
eastern Pacific waters and extends across all of Baja, as well as
portions of northern Mexico and parts of the Desert Southwest.

The 25/00Z KTWC sounding revealed a PW of only 0.88 inches, which
was down 0.18 inches from the 12Z flight and 0.08 inches lower than
24 hours ago.

IR satellite imagery shows scattered mostly mid and high level
debris clouds covering the eastern half of the state and extending
into New Mexico and Colorado, all associated with the aforementioned
trough axis.

Radar mosaic from around the region indicates that showers and
storms are mostly on the decline. However, earlier this afternoon
and evening a cluster of storms developed over the Mogollon Rim and
dropped south into the Phoenix metro. This batch of storms produced
a strong outflow that progressed south and southwest from the
Phoenix metro toward the Gila Bend area. As a result of these
outflow winds both the Phoenix and Tucson offices issued a Blowing
Dust Advisory. The advisory for my forecast area covered western
parts of Pinal county and central parts of Pima county, which
included northern parts of the Tohono O`Odham nation but was allowed
to expire at 9 PM MST since the winds have gradually diminished.

Even though the showers and storms are mostly diminishing, will make
some adjustments to the POP grids to reflect current satellite and
radar trends through the rest of the overnight hours.

Temperature trends seem to be on track, so no big changes expected
but will make some minor adjustments here and there to account for
the latest trends.

See the previous discussion below for details beyond tonight.

&&

.AVIATION...VALID THRU 26/06Z.
VFR conditions through the forecast period. Isolated -TSRA/-SHRA
through 25/05Z possible, followed by a clearing trend overnight.
Surface wind generally less than 12 kts outside of thunderstorm
outflows during the afternoon. Aviation discussion not updated for
TAF amendments.

&&

.FIRE WEATHER...Isolated thunderstorms during the afternoon and
early evening again Thursday. Increasing storm coverage is then
expected Friday through Sunday as monsoonal moisture increases from
the south. 20-foot winds into the upcoming weekend will be terrain
driven and less than 15 mph in most locations. Expect the potential
for strong and gusty winds near thunderstorms and stronger afternoon
and early evening winds today in the upper Gila River valley, with
northwest winds of 20-25 mph.

&&

.PREV DISCUSSION...With the weak troughiness east of our area
Thursday, the flow will weaken and begin to gain a more southerly
component. Below average thunderstorm coverage once again, but
increasing especially along border areas.

Friday, Saturday and Sunday are looking busier as we once again try
to make Southeast Arizona the home of the state`s deepest moisture.
A more typical late August scenario with increasing thunderstorm
coverage for most of the area. We`ll also likely see some overnight
activity.

For next week, we`ll see some ridging and a weaker flow, however we
should have enough moisture around for a chance of thunderstorms,
with an emphasis on eastern areas.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

DISCUSSION...Mollere
PREVIOUS DISCUSSION...Meyer

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