920
FXUS65 KTWC 062110
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
210 PM MST Mon Oct 6 2025

.SYNOPSIS...Expect a warming trend this week as high temperatures
rise above normal through the work week. Moisture returns late
this week, initially providing increased cloud cover and very
slight chances for showers Wednesday with chances increasing late
this weekend into the weekend. Best chances for widespread rain
look to be this weekend.

&&

.DISCUSSION...Skies are clear across the CWA under southwest flow
aloft thanks to troughing over the western U.S. and a large high
over the Southeast. Over the next couple of days the ridge will
expand westward becoming centered over Texas and northern Mexico
by the middle of the week and a closed low will be moving into the
Pacific Northwest. In the tropics Hurricane Priscilla is centered
about 370 miles south of Cabo and is forecasted to travel north
northwest during the week paralleling the west coast of Baja.

The positioning of the high and Pacific low will allow
southwesterly/southerly flow to advect tropical moisture from
Priscilla into the region beginning Wednesday. Thursday into the
weekend PWAT values are expected to be 200-250 percent of normal
which translate to values around 1.3" at the AZ/NM border
increasing to 1.5" in Tucson and 1.8" in far western Pima County.
NBM PoPs have increased compared to previous forecasts, especially
Thursday and Friday. Slight rain chances (15-25 percent) begin
Wednesday along the AZ/NM border then increase in coverage Thursday
and Friday with area wide chances by this weekend generally 25-45
percent. Looking increasingly likely for moderate showers each
day late this week into the weekend, but the question still
remains on coverage of thunderstorms and intensity of the rain.
Ensembles place the Pacific low off the coast of Oregon and
Washington Thursday and Friday with high pressure centered over
West Texas. Synoptic scale forcing will be very limited during
this time with how far away the low is and the proximity of the
ridge. Thick mid-level cloud cover could also hinder storm
intensity without the extra upper level support. So while there
will likely be shower activity thanks to the anomalous moisture,
at this time don`t expect more than isolated thunderstorms and
limited heavy rainfall potential. However there is still some
uncertainty with the east/west positioning of the trough which
will influence rain amounts.

This weekend the low opens up and moves inland through the Great
Basin and the high shifts a little further south into Mexico. The
latest ensemble runs bring the trough further south than previous
runs which has resulted in PoPs increasing this weekend. The best
synoptic scale lift will still be to the north of the area, but
with the high possibly moving further south storms will have a
better chance of producing heavy rainfall. Still a lot of
uncertainty in rain amounts with Friday-Sunday rain total spread
between the 25th and 75th percentile generally 0.5"-1.5" and
1.5"-3.0" between 10th and 90th. Still a lot of details to work
out but higher confidence in a wet end of the week and weekend,
and lower confidence on the heavy rainfall threat. The heavy
rainfall will depend on how far south the low ends up. Rain
chances continue into early next week as the moisture sticks
around and another trough moves through the region.

&&

.AVIATION...Valid through 08/00Z.
SCT-BKN clouds AOA 20k feet in the vicinity of KOLS and KDUG
beginning this evening through the end of the period and SKC
elsewhere. Surface winds becoming southerly 5-10 knots through
the early evening then light and terrain driven overnight. Tuesday
afternoon winds become southerly 5-10 kts again. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Minimum relative humidities mainly 12-20 percent
through Tuesday. Winds on the lighter side to start the work
week, with gusty southeasterly winds in the Gila River Valley
Wednesday through Friday. A push of moisture should begin to bring
up minimum relative humidities through the second half of the
week. This will also increase rain chances beginning Wednesday
along the AZ/NM border then over most of southeast Arizona
Thursday into the weekend with the best chances this weekend.

&&

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

$$

Hardin

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