Area Forecast Discussion
Issued by NWS Tucson, AZ
FXUS65 KTWC 300426
Area Forecast Discussion
National Weather Service Tucson AZ
926 PM MST FRI JUL 29 2016
.SYNOPSIS...A good monsoon pattern will remain in place through at
least the middle of next week resulting in plenty of afternoon and
evening thunderstorms and occasional overnight storms. Storms this
evening will be capable of producing very strong winds with areas of
blowing dust, mainly north and west of Tucson. Saturday into early
next week extra moisture brings an increased threat of very heavy
rain and local flooding. With the abundant moisture and storms,
temperatures will be cooler this weekend into next week.
.DISCUSSION...After an active late afternoon and early evening,
storms have mostly shifted to the west.
As storms continue to march west, I adjusted the POP forecast for
the remainder of this evening and into the overnight hours to
account for the most recent satellite and radar trends. Also just
removed portions of our CWA from the Severe Thunderstorm Watch to
now just include zones 501 and 502, which is far western PIma county
(Ajo and Organ Pipe) and central Pima county, including the Tohono
I also made some adjustments to the short term hourly temperature
grids and also to some of the overnight lows to account for areas
that were rain cooled significantly, and as a result the inherited
overnight low temps no longer seemed reasonable.
For details beyond tonight, please refer to the previous discussion
.AVIATION...Valid through 01/06Z.
Expect scattered SHRA/TSRA into this evening moving generally E to
W. Mostly VFR conditions are anticipated thru pd except for MVFR
in/around SHRA/TSRA due to heavy rain. Winds generally 10 kts or
less except brief gusts to 50 mph psbl with stronger TSRA. Aviation
discussion not updated for TAF amendments.
.FIRE WEATHER...Storms will continue to move west and diminish
through the remainder of the night. Could see additional development
later tonight as outflows from the complex south of the border push
Saturday and Sunday, due to an increase in moisture across the
region we are expecting more widespread convection each afternoon
and likely overnight as well with the potential for locally very
heavy rains. The abundant moisture will linger into next week before
easing back after Wednesday. This moisture will also result in
cooler daytime temperatures and higher humidity levels Saturday
onward. Winds will generally be light except those associated with
thunderstorms where gusts in excess of 50 mph are possible,
especially this afternoon.
.PREV DISCUSSION...The focus shifts toward the weekend with an
interesting setup taking place. Moisture will continue to stream
northward with PW`s of 1.75 to possibly 2+ resulting in the
potential for very heavy rains with stronger or persistent
thunderstorms (note WPC Slgt risk for excessive rain). Normally
would have some concern of clouding over with limited convection but
models developing inverted mid-level trough over the area acting as
focusing mechanism which should override that issue. H20 loop also
shows several features moving across the top of the ridge that
should roll across the area at some point this weekend although
timing is tough at best. Each of these can be a good focusing
Upshot to all this is there is potential for thunderstorms producing
very heavy rains of 1-3 inches later Saturday and Sunday with
concerns for local flooding issues. This also would be a good set up
for nighttime storms both Saturday and Sunday nights. The main
problems are location and timing. At this time will continue to
highlight the threat but headlines not to be issued at this time.
Moving into early next week, still have an impressive amount of
moisture across the area Monday through Wednesday before it begins
to ease back down a bit, basically back toward more normal levels.
So there will be a heightened threat for convection producing local
heavy rains early next week. All this moisture will help to lower
afternoon temperatures Saturday onward with Sunday and Monday
possibly being the "coolest" days.
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