Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 230404
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
904 PM MST Sat Jul 22 2017

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

&&

.DISCUSSION...Plenty of moisture and easily accessible
conditional instability combined with strong organized outflows to
generate a great day for rain across most of the area. Outflow
continues to push through southern areas, including Santa Cruz
county this evening. Expect mainly moderate showers with isolated
embedded thunder to continue for another hour or two down there.
For the early morning hours, we will see some shower activity in a
diminishing debris field, and watch for any outflows from late
night activity in New Mexico.

We may not see that until after sunrise however, with the HRRR
developing convection in the mid morning across NM border areas.
Slow development elsewhere, but the flow may be strong enough to
reset the atmosphere for areas hit hard today by late afternoon
and early evening tomorrow. We`ll have to see how much heating we
are able to manage.

Busy period may take a break around Tuesday and Wednesday as we
introduce a southwesterly component to our flow, a decrease in
moisture, and mid level warming with the high center shifting
around a bit. That won`t last long though.

&&

.AVIATION....AVIATION...Valid thru 24/06Z.
SCT SHRA/TSRA diminishing overnight. Otherwise 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. 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. Isolated to scattered showers and thunderstorms are
then expected Tuesday into next weekend. 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.

&&

.PREV DISCUSSION...Activity got off to a quick start this morning
with first storm of the day popping up over the Chiricahua
mountains after 830 am which produced around 0.80" in less than an
hour. Mountain storms struggling to maintain themselves once they
move into lower elevations. With well above normal PW values in
place, between 1.60" and 1.85, heavy rain main threat this
afternoon into the evening hours, especially in the mountains.
Thus went ahead and hoisted a flash flood watch for areas east and
south of Tucson. The MCV mentioned in the morning discussion that
was near Glenwood NM in Catron county was over western Grant
county in NM and drifting south. For tonight scattered showers and
thunderstorms, more numerous east and south of Tucson. Tucson
will have to rely on outflow interactions for storms in the city.

Flow aloft becomes more E-SE later tonight as models move inverted
trof, which extended from NW NM to southern Sonora MX this morning.
Sunday has the potential to be rather gunked over for the bulk of
the day with showers around and embedded isolated thunderstorms.

High temperature forecast a challenge with MOS numbers rather cool
for July with lots of clouds around. At this time, the official
forecast high in Tucson for Sunday of 89 degrees would be the first
sub-90 high in July since 2010.

Monsoon train remains on the track next week, although there could a
slowdown day or two, while high temperatures warm back to late July
normal values.

&&

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

&&

$$

Meyer

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