Flash Flood Watch 3, NWS Tucson, AZ

073 
WGUS65 KTWC 170306
FFATWC

Flood Watch
National Weather Service Tucson AZ
806 PM MST Thu Aug 16 2018

AZZ501>504-507-513>515-170415-
/O.EXP.KTWC.FF.A.0003.000000T0000Z-180817T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Western Pima County-Tohono O'Odham Nation-
Upper Santa Cruz River Valley/Altar Valley-Tucson Metro Area-
Upper San Pedro River Valley-
Dragoon and Mule and Huachuca and Santa Rita Mountains-
Catalina and Rincon Mountains-Baboquivari Mountains-
Including the cities of Ajo, Organ Pipe Cactus N.M., Sells, 
Nogales, Tucson, Green Valley, Marana, Vail, Sierra Vista, 
Benson, Bisbee, Canelo Hills, Madera Canyon, Mount Lemmon, 
and Summerhaven
806 PM MST Thu Aug 16 2018

...FLASH FLOOD WATCH HAS EXPIRED...

The Flash Flood Watch for a portion of Southeast Arizona has
expired. That said, a few thunderstorms with locally heavy 
rainfall will likely continue through midnight tonight but the 
threat for widespread flash flooding had ended.

$$

Area Forecast Discussion
National Weather Service Tucson AZ
915 AM MST Thu Aug 16 2018

.SYNOPSIS...Another relatively cool day with scattered to numerous
showers and thunderstorms expected later today. Then more typical
monsoon conditions is forecast for Friday into next week with
temperatures running near to or slightly warmer than normal.

&&

.DISCUSSION...Mid and high level cloud cover is currently over a
good portion of the area, however it is lifting northward which will
help out with solar heating, especially southern areas.  Near record
levels of PW on our and the PHX morning soundings and while the
instability isn't stellar, it is enough to be of some concern,
primarily due to the relatively light flow resulting in slower
moving storms.  Several CAMs continue to point toward convection
developing behind the clearing, mainly the western half/two thirds
of the forecast area and this is the area with the very high PW.
Excluding yesterday, many locations in this area have received heavy
rainfall over the previous 3-4 days and wouldn't need as much rain
to pose problems.  With all that and discussion with neighboring
offices, we are considering a Flash Watch for this afternoon and
early evening for portions of the area.  Will finalize that thinking
one way or the other over the next hour or two.  Any convection that
does develop is expected to dwindle off not too long after sunset
for another relatively quiet night.  High temps this afternoon will
generally run 3-8 degrees cooler than average.

By Friday afternoon the upper level high will have settled over the
region which will help to suppress convective development to a
certain degree. We will have plenty of moisture in place and enough
instability that we should be able to produce some convection over
higher terrain mainly east and south of Tucson. Temperatures will
rebound to mid August normals.

For the Saturday through Wednesday time period, the upper level high
will meander back and forth across the SW resulting in varying
amounts of convection from one day to the next. Afternoon
temperatures will be near to or slightly warmer than normal under
this scenario and will vary a few degrees depending on the amount and
exact location of any convection. Monsoon 2018 continues.

&&

.AVIATION...Valid through 17/18Z.
SCT-BKN clouds AOA 18k ft AGL will decrease throughout the late
morning. Isolated to scattered -SHRA/-TSRA develop this afternoon
and evening, decreasing in coverage after sunset. Brief MVFR
conditions possible with the +TSRA. Otherwise SCT-BKN cloud bases
generally 8-12k ft AGL this afternoon and evening. Outside of
thunderstorm gusts, expect SFC winds mainly less than 12 kts.
Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...The pattern is favorable for scattered showers and
thunderstorms through Saturday, with lower rain chances and drier
conditions by Sunday. Rain chances will increase again early next
week. Temperatures will remain cooler than normal today then near to
or slightly warmer than average temperatures will continue through
the remainder of the forecast period. 20-ft winds will be terrain
driven at less than 15 mph, except for in and around thunderstorms
where strong outflows may occur.

&&

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

PUBLIC...Cerniglia
AVIATION....Carpenter
FIRE WEATHER...Carpenter

Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson