Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 231004

Area Forecast Discussion
National Weather Service Tucson AZ
300 AM MST Sun Jul 23 2017

.SYNOPSIS...Scattered to numerous thunderstorms will continue
through Monday, mainly during the afternoon and evening hours.
Conditions for thunderstorms will become less favorable by mid week,
before another upswing in activity develops late in the week.


.DISCUSSION...Abundant moisture remains across the forecast area
this morning with surface dewpoints in the mid 60s to lower 70s and
PW values ranging from 1.5 in the northeast to 2 inches in the
southwest.  We also have plenty of instability waiting to be worked
on and that will be the case for the next 36 hours.  Plenty of cloud
cover and afternoon convection is expected to really limit heating
today and will maintain the 8-10 degree cooler than normal
temperature forecast for today.

Potentially interesting setup for tonight into Monday raising
concern for more flood producing rains. The inverted trough that has
been helping to bless us with all the convection is expected to get
caught up in the developing S-SW mid-level flow tonight through
Monday driving the somewhat more consolidated closed (by Monday
morning) feature north.  As it does it places much of our area in a
favorable location for vertical lift to act on all this moisture and
conditional instability and a few models have been suggesting areas
of very heavy rain developing tonight into Monday. Considered a
Flash Flood Watch for late today through tonight in cooperation with
my neighbors but we decided to hold off at this time. Stay current
on the latest forecast updates as that may change if confidence in
that scenario increases.

Once that system moves off to the north a slightly drier southwest
flow develops lowering dewpoints at least 10 degrees and dropping
the PW back down closer to 1.3 inches. That along with some warming
in the mid-levels will hamper convection quite a bit Tuesday and
Wednesday and possibly into Thursday.  Not to say there won`t be
storms, just not as widespread as they have been and primarily
confined to mountains east and south of Tucson. The other change as
a result of this drying will be temperatures quickly rebounding back
to more normal levels Tuesday through Thursday, meaning around 90
higher eastern/southern valleys like Douglas, to 95-100 around
Tucson and 100-105 across the western deserts.

Then at this time it looks like the upper high will reposition
itself back into its favorable (for us) position to our north with
another inverted trough setting up allowing for more moisture and a
more favorable convective environment to develop. That pairing
should allow for a noticeable increase in convection across the area
once again Friday into next weekend.  Cerniglia


.AVIATION....Valid thru 24/12Z.
More of the same, VFR conditions with cloud decks generally 5k-10k
ft AGL with BKN layers above, and surface wind variable in direction
mainly less than 12 kts. SCT TSRA redeveloping after 23/17Z and
likely continuing through the night. Winds vicinity TSRA could gust
40+ kts. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Scattered to numerous mainly afternoon and evening
thunderstorms will continue into Monday with locally heavy rain and
strong winds. Fewer storms are then expected Tuesday through at
least Thursday as somewhat drier air moves over the region.
Temperatures will remain below normal through Tuesday, with near
normal readings the rest of the week. 20-foot winds will remain
below 15 mph with the exception of strong outflow winds in the
vicinity of thunderstorms.





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