Sil Nakaya, Arizona Weather Forecast Discussion

280
FXUS65 KTWC 160909
AFDTWC
Area Forecast Discussion
National Weather Service Tucson AZ
209 AM MST Tue Sep 16 2025
.SYNOPSIS...Moisture has moved into the region which will lead to
scattered showers and thunderstorms today through the end of the
work week. Temperatures will be slightly above normal today, then
around normal to just below normal into the weekend.
&&
.DISCUSSION...Skies are mostly cloudy across southeast Arizona
with a few weak showers south of Tucson. Aloft high pressure is
centered over northern Mexico and a weak shortwave sits off the
coast of northern Baja. There is also tropical storm Mario about
300 miles west of Cabo. Mario will feed significant moisture into
southern California and Arizona later this week. Some of this
moisture is already beginning to move in. By this afternoon PWATs
will be 100-150 percent of normal with the best moisture south of
Tucson. This will result in an uptick in thunderstorm activity
compared to yesterday. Hi-res guidance shows scattered convection
beginning this afternoon over most of southeast Arizona.
Initially storms will form from Tucson south and eastward then
expand west into the Tohono O`odham Nation. Late in the afternoon
and early evening outflows from storms could lead to some blowing
dust in Pinal County and parts of Pima County. Storms will be
capable of strong wind gusts and heavy rainfall, which could lead
to localized flash flooding.
Wednesday into Thursday Mario will weaken but travel northward
which will further increase moisture values in southeast Arizona,
especially from Tucson westward. Wednesday expect another round of
scattered showers and thunderstorms with the most activity
expected in central Pima County and the sky islands. PWAT values
will be 1.5"-1.8" from Tucson to far western Pima County. Storms
will be capable of heavy rainfall and strong winds.
Persistent southerly to southwesterly flow will continue to
advect tropical moisture from the remnants of Mario through
Friday. Mario`s upper level circulation will move into southern
California during this time. Southeast Arizona will be on the the
eastern periphery of its synoptic scale forcing, but there should
be enough to help facilitate daily scattered thunderstorms capable
of heavy rainfall both days. It`s possible one of these days
could be less active because of the previous day`s convection or
because of thick mid-level clouds that hinder insolation. The
added moisture will bring temperatures down to around normal or
just below normal Wednesday into the weekend.
This weekend storm chances decrease as the better moisture moves
to the north and upper level forcing weakens. However another
tropical wave, currently south of Mario, is given an 80 percent
chance to form into a tropical cyclone over the next 7 days. The
track of this next system will have an impact on this weekend`s
and early next week`s forecast. However lots of uncertainty this
far out with how it will track.
&&
.AVIATION...Valid through 17/12Z.
SCT-OVC clouds 6k-10k ft AGL through the period with a BKN layer
AOA 20k ft AGL moving in from the south after 16/15Z. Scattered
TSRA will be possible from KTUS south and eastward after 16/20Z
through 17/04Z. With storms and showers expect locally heavy
rainfall and erratic winds up to 45 kts. Other than thunderstorm
driven winds, SFC winds will be from the east southeast 5-10 kts.
Aviation discussion not updated for TAF amendments.
&&
.FIRE WEATHER...Moisture will be on the increase this week leading
to min RH 20-40 percent through the weekend. Thanks to the
moisture expect daily thunderstorm chances through Friday. Today
storms start from Tucson south and eastward then spread to
central Pima County early this evening. Thereafter chances will
be area wide generally 30-60 percent. This weekend storms chances
decrease, but still linger around 15-20 percent. 20-foot winds
will be 8-12 mph with some afternoon/early evening gusts to around
20 mph over the next week. Wind direction will be easterly today
then return to normal diurnal patterns through the weekend.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Hardin
Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson

NWS TWC Office Area Forecast Discussion