087
FXUS65 KTWC 010909
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
209 AM MST Sun Jun 1 2025

.SYNOPSIS...Temperatures cool to below normal as a weather system
moves through today and Monday. This system will bring a
substantial moisture increase into the region leading to
widespread showers and isolated thunderstorms through Monday
morning. Slight chance for storms Tuesday then expect dry
conditions and warming temperatures thereafter.

&&

.DISCUSSION...Light shower activity has begun west of Tucson as
an upper level low currently west of Baja begins to slowly move
eastward. Moisture is streaming in from the south thanks to
tropical storm Alvin. PWAT values are currently around 1.1" west
of Tucson and will increase to 1.3"-1.6" by this afternoon, which
is 250-300 percent of normal. A couple lightning strikes have also
be detected in the showers.

This activity will continue through the morning hours, slowly
expanding eastward increasing in coverage and strength late this
morning into the afternoon. HREF members show showers and
thunderstorms reaching the Tucson area by mid to late afternoon.
Then by evening covering most of southeast Arizona. The dynamics
brought by the low combined with surface heating could lead to
some stronger storms capable of localized heavy rainfall. The
01/00Z HREF paints areas over the Tohono O`odham Nation and Santa
Cruz County as the most at risk for heavy rainfall with
probabilities for 1" or greater of rain generally 30-60 percent.
General rainfall totals are expected to be 0.2"-0.8" for valley
locations with localized areas possibly seeing up to 1.25" through
Monday. The bulk of this is expected to fall this afternoon and
evening. Soils are very dry across the area, so a lot of this rain
will quickly runoff and could lead to flooding issues. Because of
this and the threat of debris flows over new area burn scars a
Flash Flood Watch is in effect Sunday from Tucson westward. Gusty
outflow winds will also be a threat before low levels moisten up,
especially east of Tucson late this afternoon into the evening.
HREF shows probabilities of 30-50 percent for winds in excess of
30 knots east of Tucson.

Overnight showers will continue, but rain amounts will be on the
lighter side as the upper low weakens and moves northeastward
towards the Four Corners. During this time PWAT values also begin
to decrease, although they will still be above normal for this
time of year. As synoptic scale forcing decreases shower activity
will decrease from west to east Monday with additional rainfall
amounts up to 0.25". High temperatures today and Monday will be
moderated by the moisture and cloud cover with Tucson possibly
seeing sub 90 degree highs both days.

Tuesday PWAT values will be diminished compared to today, but will
still be around 150 percent of normal. Another low will move
through Tuesday and will tap into the leftover moisture leading to
a slight chance for showers and thunderstorms. Best chances will
be in the White Mountains. Thereafter southeast Arizona stays
under dry southwest flow with high pressure becoming centered over
northern Mexico and shortwave troughing over the West Coast.
Temperatures will stay below normal through Wednesday then
increase to normal or a few degrees above normal Thursday into
next weekend.

&&

.AVIATION...Valid through 02/12Z.
Expect BKN clouds 4k-8k ft AGL through the period. -SHRA and
isold -TSRA dvlpg west of KTUS this morning and spreading east
across the remainder of fcst area this afternoon. Thereafter
expect SHRA/TSRA at most terminal locations through the end of the
forecast period. Brief MVFR cigs will be possible after 02/03Z in
SHRA. SWLY/SLY winds 8-15 kts thru much of valid pd. Isold gusts
to 30-40 kts near any TS that develop. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...Tropical moisture moves into the area today which
will lead to widespread showers and isolated thunderstorms. This
activity begins this morning west of Tucson, spreading to cover
most of southeast Arizona late this afternoon into the evening.
Showers and thunderstorms decreases from west to east Monday.
Rain could be heavy at times leading to possible debris flows over
new area burn scars. Overall winds remain light but gusty and
erratic winds would occur with any thunderstorm activity. Another
weather system moves through Tuesday with a slight chance for
precip east of Tucson along with breezy winds. Thereafter expect
dry and warming conditions.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Flood Watch from this afternoon through this evening for
AZZ503>507-513-514.

Flood Watch from 7 AM MST this morning through this afternoon
for AZZ501-502-515.

&&

$$

Hardin

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