Flash Flood Warning 33, NWS Tucson, AZ

953 
WGUS75 KTWC 030902
FFSTWC

Flash Flood Statement
National Weather Service Tucson AZ
202 AM MST MON SEP 3 2018

AZC019-023-030912-
/O.EXP.KTWC.FF.W.0033.000000T0000Z-180903T0900Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Pima-Santa Cruz-
202 AM MST MON SEP 3 2018

...THE FLASH FLOOD WARNING FOR SOUTHEASTERN PIMA AND NORTH CENTRAL
SANTA CRUZ COUNTIES HAS EXPIRED...

The heavy rain has ended. Flash flooding is no longer expected to 
pose a threat. Please continue to heed any remaining road closures.

LAT...LON 3180 11100 3170 11090 3164 11127 3173 11135

$$
Zell

Area Forecast Discussion
National Weather Service Tucson AZ
955 PM MST Sun Sep 2 2018

.SYNOPSIS...Expect scattered thunderstorms across much of the area
the rest of tonight, then scattered thunderstorms mainly from Tucson
eastward on Monday. A gradual drying trend should prevail Tuesday
into Friday, with isolated thunderstorms mainly east of Tucson.
Daytime temperatures will be a few degrees below normal through
Wednesday, then warming to near normal Thursday into next weekend.

&&

.DISCUSSION...Expansive area of showers and thunderstorms across
southeast Arizona as of this writing. The exceptions were across the
White Mountains and western Pima County where precip-free conditions
were ongoing. The strongest thunderstorms were generally in a line
from central Cochise County westward into far southeast Pima County
and northwest Santa Cruz County.

Another area of strong thunderstorms was northwest of Tucson in
south central Pinal County and far north central Pima County. IR
satellite imagery depicted warming cloud tops during the past hour
across eastern sections. However, cloud tops were cooling during the
past hour northwest to south of Tucson.

Water vapor satellite imagery depicts a cyclonic twist just west of
this forecast and embedded within the synoptic scale upper trough
over the southwestern CONUS. This feature appears to be enhancing
the showers/tstms northwest to south of Tucson. These stronger
showers/tstms are within the axis of higher instability as depicted
via the Storm Prediction Center Mesoscale Analysis ML CAPE valid
03/04Z.

Worthy to note that several HRRR solutions as well as the NAM12
suggests precip-free conditions across much of this forecast area by
the next few hours and continuing into early Monday morning.
However, based on radar/satellite trends, these solutions are
discounted. At any rate...

Expect scattered showers/tstms the rest of tonight, with precip-free
conditions likely across western Pima County and northeast of
Safford. Locally heavy rainfall with potential for flooding should
also occur. Isolated to scattered showers/tstms Monday afternoon and
evening mainly Tucson eastward still appears reasonable.

Please refer to the additional sections for further detail.

&&

.AVIATION...Valid through 04/06Z.
Scattered -TSRA/-SHRA across much of southeast Arizona the rest of
tonight. Scattered -TSRA/-SHRA mainly KTUS vicinity eastward to New
Mexico state line Monday into Monday evening. Cloud decks apart from
lower thunderstorm bases generally 8k-12k ft AGL. West of KTUS
mainly FEW-SCT clouds around 10k ft AGL. Surface wind variable in
direction mainly less that 12 kts, except brief gusts to 40 kts with
stronger TSRA. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Scattered thunderstorms mainly from Tucson eastward
to the New Mexico state line on Monday. A drying trend will then
occur Tuesday into next weekend, with isolated mainly afternoon
and evening thunderstorms especially east of Tucson. Expect terrain
driven 20-foot winds at less than 15 mph, with brief strong gusts
near thunderstorms.

&&

.PREV DISCUSSION /305 PM MST/...Satellite imagery this afternoon
showed partly cloudy skies across much of southeast Arizona. A few
showers and thunderstorms had also developed mainly east of a line
from about Gila Bend to Sierra Vista. Surface temperatures ranged
from the low 90s around Tucson to the mid 70s across Cochise County
where cloud cover has limited the extent of heating so far today.

The pattern was defined by an upper trough draped across the
southwestern states, which is progged by various NWP models to
deepen slightly as it pushes very slowly eastward into NM over the
next few days. As such, additional dynamics for storm development
will be in place today into Labor Day, with isolated to scattered
showers and storms in the forecast into tomorrow evening. In the
near term, this thinking was consistent with the latest solutions
from the HRRR, U of A and other local WRFs. The best chance for
measurable rainfall at KTUS is thought to be this afternoon or this
evening as suggested by the 02/20Z HRRR and 02/12Z U of A WRFNAM.

However, the continued robust westerly flow will work to push deeper
moisture eastward by Tuesday, confining convection to areas mainly
east and south of Tucson, and especially near the AZ/NM border. This
trend is expected to continue through Friday, when the trough
finally moves out and high pressure off the southwest coast of
California advances eastward. This will draw drier air into the
state on northerly flow aloft. There will still be some low level
moisture capable of supporting a few buildups, but activity should
by and large be limited this weekend.

High temperatures through Wednesday will be 3-5 degrees below
average. An increase in heights will then warm temperatures to
within a degree of average Thursday into next weekend.

&&

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

&&

Francis/Carpenter/Pegram

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