Harshaw, Arizona Weather Forecast Discussion

142
FXUS65 KTWC 162010
AFDTWC
Area Forecast Discussion
National Weather Service Tucson AZ
110 PM MST Tue Sep 16 2025
.SYNOPSIS...Moisture has moved into the region which will lead to
scattered showers and thunderstorms through the end of the work week
with gradually diminishing thunderstorm chances over the weekend.
Temperatures near to just below normal into the weekend.
&&
.DISCUSSION...Partly cloudy skies this afternoon across southeast
Arizona with isolated to scattered shower and thunderstorm activity
now getting underway mainly across Santa Cruz, Cochise, Graham and
Greenlee Counties. Moisture levels are above normal for this of year
with the 18Z KTWC sounding showing a PWAT of 1.28 inches with PWAT
values across the forecast area ranging from about 120 to 140
percent of normal. Modest instability on the 18Z KTWC with MLCAPE
around 200-300 J/KG, though this should increase and range from 500-
1000 J/KG from Tucson south and eastward this afternoon. Moisture
import will continue over the next few days with help from TS Mario
and eventual remnants. Mario is currently located about 465 miles
west of the southern tip of Baja California and continues to move NW
but is forecast to weaken into a remnant low by tomorrow. For storms
this afternoon into evening, individual storms will move slowly
towards the north to west with the main concerns being locally heavy
rain with isolated flash flooding threat and gusty outflow winds.
An active period of weather for mid September will continue over the
next few days as additional moisture translates northward into our
forecast area, especially the western half where PWATs will be up to
around 1.5 to 1.7 inches Wednesday through Friday. These values are
up to around 150 to 180 percent of normal. In terms of thunderstorm
development, moisture availability will certainly be there. Mid
level support broadly looks more favorable Wednesday for
thunderstorms compared to today. The HREF is focusing on areas from
Tucson westward with locally heavy rain and isolated flash flooding
being the main threat. Biggest uncertainty for Wednesday (and
beyond) is how much pre-existing cloud cover will limit stronger
convective development which would mean precipitation is more
showery in nature with just some embedded thunderstorms. By Thursday
and Friday, the mid level remnants from Mario will shift into
California with mid level west to southwest flow becoming more
prevalent. Given the deep moisture in place, any disturbances in
this flow pattern will aid in thunderstorm development.
Drier air aloft will gradually increase over the weekend as the flow
becomes more west to even potentially northwesterly with ridging to
our south to southwest. This will result in gradually reduced
precipitation chances this weekend with mostly dry conditions by
early next week. We should note that the NHC does have a 90% chance
of tropical cyclone formation off the coast of southwestern Mexico
over the next 5 days but at this time it looks like this system will
have little to no impact for us.
Temperatures will generally be near to slightly below normal through
the weekend, warming up to slightly above normal levels early next
week.
&&
.AVIATION...Valid through 18/00Z.
SCT-BKN clouds 6k-10k ft AGL through the period with a BKN-OVC layer
AOA 20k ft AGL thru the end of the valid period. Scattered TSRA
mainly from KTUS south and eastward through 17/04Z. With showers and
thunderstorms, 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...Above normal moisture this week leading to min RH 20-
40 percent through the weekend. Expect scattered shower and
thunderstorm chances (30-60 pct chance) each day through Friday,
then gradually diminishing thunderstorm chances this weekend into
early next week. 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.
&&
$$
GL
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NWS TWC Office Area Forecast Discussion