Portal, Arizona Weather Forecast Discussion

151
FXUS65 KTWC 192003
AFDTWC
Area Forecast Discussion
National Weather Service Tucson AZ
103 PM MST Fri Sep 19 2025
.SYNOPSIS...Ample moisture across the region will result in
isolated to scattered showers and thunderstorms each day through
early next week. Temperatures near to just below normal into the
weekend before warmer and eventually drier weather returns later
next week.
&&
.DISCUSSION...Partly cloudy skies early this afternoon across
southeast Arizona with visible satellite imagery showing increasing
cumulus cloud cover which is now resulting in the development of
scattered showers and thunderstorms across the forecast area. With
considerable moisture in place (PWAT`s 1.1 inches east to 1.6 inches
west), moderate instability on the 18Z KTWC sounding (SBCAPE of 1100
J/KG) and 25-30 kts of 0-6km shear, scattered showers and
thunderstorms will continue to expand in coverage this afternoon
into evening as they shift to the east. Main concerns will be
isolated flash flooding threat where storms back-build and secondary
threat for gusty winds to around 40 mph.
We`ve been advertising a reduction in thunderstorm chances this
weekend and while by and large that is still the case in comparison
to what we`ve had the past few days, thunderstorm chances will still
continue, especially Sunday into early next work week. Saturday
looks to be the most down day as drier air aloft works its way in
along with increased ridging aloft. This will tend to result
recycled moisture providing isolated thunderstorms from Tucson south
and eastward. The most favored locales Saturday for showers and
thunderstorms will be the higher terrain.
Ensembles are in good agreement through Monday depicting a longwave
trough and upper low off the southern California coast. With ample
lower level moisture remaining in place and more favorable
southwesterly flow on the eastern flank of the trough, that will
continue to result in isolated to widely scattered showers and
thunderstorms on Sunday and scattered thunderstorms on Monday when
more favorable dynamics potentially help out.
More noticeable differences start to show up in the ensemble
guidance in the middle of the week with the evolution of the upper
low and how fast it kicks out. With that said, until we get a good
dry westerly push, which may not occur until the end of next week,
we will maintain daily slight chances of thunderstorms. Confidence
later next week is lower than normal.
Near normal temperatures continue into early next week, then warm to
above normal levels mid to late next week.
&&
.AVIATION...Valid through 21/00Z. SCT-BKN clouds 6k-10k ft AGL
and SCT-BKN layer AOA 18k ft AGL thru the valid period. Scattered
TSRA continues through 20/04Z then diminishes. Gusty and erratic
winds to around 35 kts possible near thunderstorms, especially to
the southeast and east of Tucson (near KALK/KDUG/KSAD) this
afternoon. Outside of thunderstorms, SFC winds mainly less than 12
kts, favoring WLY direction in afternoon hours and ELY/SELY
overnight and morning hours. Aviation discussion not updated for TAF
amendments.
&&
.FIRE WEATHER...Above normal moisture is in place leading to min
RH between 20-40 percent through the weekend. Expect generally
scattered shower and thunderstorm chances (30-60 pct chance) today,
then isolated to scattered showers and thunderstorms into next week
(10-40 percent chance). Heavy rainfall will be the main threat. Dry
conditions return later next week especially west of Tucson. 20-foot
winds will be 8-12 mph with some afternoon/early evening gusts to
around 20 mph over the next week with normal diurnal patterns
through the weekend.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
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NWS TWC Office Area Forecast Discussion