Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 301037
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
337 AM MST Fri Jul 30 2021

.SYNOPSIS...Scattered to perhaps numerous storms are expected
today into the weekend. Overall, storm activity early next week
will be less with any activity focused south and east of Tucson.
High temperatures will run near to a few degrees below seasonal
normals.

&&

.DISCUSSION...Light to perhaps moderate showers with a slight
chance of a thunderstorm will continue across western Pima County
through the morning hours. Thereafter, showers should
dissipate/move west of the area by mid to late morning.

Expect another active day across southeastern Arizona with the
upper level low beginning to rapidly fill/shear out as it lifts
north through Arizona by this evening. This will provide a
favorable environment for a few strong storms with heavy rain and
strong winds. There are a couple features to watch, but based on
high res models and HREF, central/western Pima County should be
favored. Storms should develop primarily in western Cochise, Santa
Cruz, and eastern Pima Counties between 19/20Z and push W/WNW
through the rest of the afternoon. HREF probabilities are hinting
that Santa Cruz to central/western Pima Counties of seeing decent
probabilities of greater than 1" in 1hr/3hr. With multiple rounds
and the potential for training/cell mergers, this seems every bit
reasonable. Would not be shocked to see a few isolated locations
receive 1-3" in three hours or less. Not too mention, storms will
also be moving into an increasingly moist/unstable airmass into
the lower deserts. With that being said, the Flash Flood Watch
looks in good shape and no changes were made.

By Saturday, thunderstorm coverage will become more isolated with
any storms focused over the higher terrain. This pattern will
continue into Sunday, before an uptick in activity for areas
primarily south and east of Tucson into mid-week. One thing to
watch will be an upper level col developing, likely enhancing
thunderstorm development. This could promote more sustained areas
of convection/stronger storms with heavy rain. Best chance for
this appears to be Cochise north into Graham/Greenlee Counties.
Something to watch as we head into next week, since models have
been bouncing the feature around.

There is decent agreement among the ensembles the high pressure
briefly shifts to SW AZ and SoCal, before gradually moving back
into the vicinity of the 4-Corners by late week. This return to
the 4-Corners would signal another possible uptick of activity and
be more widespread with increasing chances in the Tucson Metro.

&&

.AVIATION...Valid through 31/12Z.
SCT-BKN clouds 8k-12k ft AGL mainly W and N of KTUS will be pushing
W/NW this morning. Mostly clear across most of the area after
sunrise then clouding up again this afternoon with another round of
scattered afternoon and evening SHRA/TSRA. Storm impacts include
strong erratic wind gusts in excess of 30 knots, heavy downpours,
lowered vsbys, and CIGS dropping to 5k-8k feet. Outside of TSRA
outflows winds will be below 10 kts. Aviation discussion not updated
for TAF amendments.

&&

.FIRE WEATHER...Scattered showers and thunderstorms today before
a downward trend in storm activity this weekend into early next week
when storm chances will mainly be from Tucson eastward. Storms will
likely produce erratic, gusty winds and locally heavy downpours. RH
values remain well above critical thresholds through early next
week. Temps will remain near to slightly below normal. 20-foot winds
will generally be less than 15 mph when not influenced by
thunderstorms.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from noon MST today through late tonight for
AZZ501-502.

&&

$$

Public...Public Forecaster
Aviation...Aviation Forecaster
Fire Weather....Fire Weather Forecaster

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