Flash Flood and Flood in Arizona, August 11 to 12, 2016

Area Forecast Discussion
National Weather Service Tucson AZ
300 AM MST THU AUG 11 2016

.SYNOPSIS...Isolated to scattered showers and thunderstorms, a few
with locally heavy downpours, can be expected today. Otherwise, a
drying trend with warmer daytime temperatures will prevail Friday
into early next week.

&&

.DISCUSSION...The synoptic pattern continues to be defined by a
ridge to our southeast and a trough axis that extends from the
northern Rockies into the Great Basin and into south central
California. Water vapor imagery shows a large swath of mid to upper
level dry air that covers much of the eastern Pacific waters,
California, northern Baja and much of western Arizona. Across
eastern Arizona lingering moisture in all levels of the atmosphere
continue with radar detecting showers and thunderstorms across
northern portions of Cochise county and extreme southern parts of
Graham county. These showers and storms have a history of producing
heavy rain and one automated gauge in the northern foothills of the
Chiricahua mountains of northeast Cochise county has reported nearly
2.25 inches in 3 hours. Other gauges in the area have reported
amounts ranging from 0.88 inches to 1.07 inches during the past
hour. In addition, radar rainfall estimates indicate amounts of up
to 1.8 inches just east southeast of Willcox. That said, I just
extended a small stream flood advisory until 515 AM MST for
northeast Cochise county and south central Graham county.

Yesterday afternoon the KTWC sounding revealed a precipitable water
value of 1.52 inches. However, the 0645Z GPS PW values from the Univ
of AZ showed a value of just over 1.75 inches. In addition, the 06Z
CIRA LPW Totals show values of 1.4 to 2 inches across central and
western deserts of southern Arizona and values well exceeding 2
inches over north central portions of the Gulf of California and
into extreme northwest Sonora. MOS POP values for today typically
range from the scattered to numerous category and this is what I
inherited for today, but I did make some minor tweaks here and
there. The main threat with the storms that occur today will once
again be heavy rain with our airmass continuing to be quite wet.
Could also see some strong and gusty winds near the stronger storms
today.

The trough to our west and northwest will continue to move eastward
and the tail end of this system will remain to our north and east
with moisture decreasing late into the week and into the weekend as
models show ridging trying to push in from the west behind this
system. Models prog PW's to range from 1.0-1.5 inches for Friday and
perhaps from 0.75-1.25 inches by Saturday and similar readings for
Sunday and even lower into Monday, which should be our driest day.
That said, only looking at isolated to low end scattered POPs for
Friday through Monday and mainly east and south of the Tucson area.
Storm chances will pick back up slightly during the early to middle
of next week as moisture will try to creep back in on easterly flow
aloft as the ridge tries to set up over the four corners region.

For Tucson, high temperatures generally ranging from 1 to 3 degs
below normal today and Friday, then 2 to 4 degs above normal for the
weekend, followed by near to slightly above normal for Monday
through Wednesday. Low temps will be slightly above normal Friday
and Saturday mornings, then 2 to 4 degrees above normal Sunday
through Wednesday.

&&

.AVIATION...Valid through 12/12Z.
FEW-SCT clouds generally 8-12k ft AGL with isolated to scattered
SHRA/TSRA through the period. Brief MVFR conditions and wind gusts
to 40 kts possible with the stronger TSRA. Otherwise, sfc winds
generally 10 kts or less except for slightly stronger NWLY winds
through the Gila Valley near KSAD. Aviation discussion not updated
for TAF amendments.

&&

.FIRE WEATHER...Scattered showers and thunderstorms will
occur once again today along with much higher relative humidity and
below normal daytime temperatures. Friday into early next week,
expect warmer temperatures and a drying trend which will keep rain
chances confined to locations from Tucson eastward. Outside of
thunderstorm wind gusts, 20-ft winds will generally remain less than
15 mph.

&&

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

&&

PUBLIC...Mollere
AVIATION/FIRE WEATHER...French

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