Benson, Arizona Weather Forecast Discussion

678
FXUS65 KTWC 202101
AFDTWC
Area Forecast Discussion
National Weather Service Tucson AZ
201 PM MST Sat Sep 20 2025
.SYNOPSIS...Ample moisture across the region will result in
isolated to scattered showers and thunderstorms each day through
early next week. Temperatures near normal this weekend with warm
and dry air returning late next week.
&&
.DISCUSSION...Clouds and small build ups are forming along the
terrain with a few showers and thunderstorms. The 18Z sounding
launched in Tucson observed 1.38 inches of PWAT and 1500 J/kg
DCAPE with forecast SFC CAPE of 1100 J/kg. There is also a fair
bit of wind shear observed by the sounding, nearly 20kts of
effective shear. With that said, there isn`t a large scale lifting
mechanism to influence more widespread showers and thunderstorms
but there is still a slight chance isolated developments this
afternoon. The main concern with showers and storms today is
locally brief, heavy rainfall leading to flooding conditions with
a secondary concern for gusty outflow winds.
The upper pattern noted in the previous discussion remains the
same, a SW- NE orientated trough of low pressure is off the
central California coastline and a subtropical high centered over
the southern Baja. By early this coming week, the trough off the
central coast of California will move southeast to the southern
California coast which will enhance the lifting mechanism needed
to complete the ingredients for thunderstorm development.
Enhanced by the trough, deep moisture will be funneled in from the
Gulf of California, keeping PWATs well above normal for the next
several days.
The low pressure system will linger off the coast of southern
California until the middle of the week encouraging daily chances
for thunderstorms. After this point, confidence in the direction
this trough will move is low. Generally, it appears to move
eastward but where and how quickly it does so is tricky to say.
The ECMWF and the Canadian suggest it will push into southern
Arizona, cutting off the moisture supply and weakening
instability, by Saturday while the GEFS is slower and has it move
in on Sunday. Time will tell how this trough will evolve. In the
mean time, expect temperatures in the 90s with daily chances of
thunderstorms through the middle of the week.
&&
.AVIATION...Valid through 22/00Z.
SCT clouds are developing, mainly along the terrain, AOA 8 to 10k
ft AGL. Clouds will stick around for much of the afternoon
becoming SKC to FEW by 21/02Z. Slight chance for isolated to
scattered -TSRA this afternoon into the evening with gusty and
erratic winds around 35 kts possible near thunderstorms. Chances
dwindle by 21/02Z. SFC winds will be from the northwest at 5 to 10
kts becoming light and variable by 22/04Z. Aviation discussion
not updated for TAF amendments.
&&
.FIRE WEATHER...Ample moisture will be present across Southeast
Arizona to result in generally isolated thunderstorms today.
Scattered storm coverage is expected to return Sunday and Monday.
Minimum RH values between 20-40 percent through Monday. Dry
conditions return later next week especially west of Tucson.
20-foot winds will be westerly 8-12 mph with some afternoon/early
evening gusts to around 20 mph. Breezy southwest winds 10 to 20
mph will be possible Thursday and Friday of next week.
&&
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Malarkey
Visit us on Facebook...Twitter...YouTube...and
at weather.gov/Tucson

NWS TWC Office Area Forecast Discussion