Flash Flood Watch 4, NWS Tucson, AZ

690 
WGUS65 KTWC 240304
FFATWC

Flood Watch
National Weather Service Tucson AZ
804 PM MST Thu Aug 23 2018


AZZ502>515-240415-
/O.EXP.KTWC.FF.A.0004.000000T0000Z-180824T0300Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Tohono O'Odham Nation-Upper Santa Cruz River Valley/Altar Valley-
Tucson Metro Area-South Central Pinal County-
Southeast Pinal County-Upper San Pedro River Valley-
Eastern Cochise County below 5000 feet-Upper Gila River Valley-
White Mountains of Graham and Greenlee Counties-
Galiuro and Pinaleno Mountains-Chiricahua Mountains-
Dragoon and Mule and Huachuca and Santa Rita Mountains-
Catalina and Rincon Mountains-Baboquivari Mountains-
Including the cities of Sells, Nogales, Tucson, Green Valley, 
Marana, Vail, Picacho Peak State Park, Mammoth, Oracle, 
Sierra Vista, Benson, Willcox, Clifton, Safford, Hannagan Meadow,
Mount Graham, Chiricahua NM, Bisbee, Canelo Hills, Madera Canyon,
Mount Lemmon, and Summerhaven
804 PM MST Thu Aug 23 2018

...FLASH FLOOD WATCH HAS EXPIRED...

The Flash Flood Watch for a portion of Southeast Arizona has
expired. The threat of flash flooding for heavy rainfall had
diminished significantly late this evening.

$$

Area Forecast Discussion
National Weather Service Tucson AZ
241 AM MST Thu Aug 23 2018

.SYNOPSIS...Abundant moisture will provide elevated shower and
thunderstorm chances into the weekend. Some storms will produce
heavy rain and gusty winds. We may start to see some drying early
next week with fewer storms. Temperatures will run near or slightly
below normal for late August.

&&

.DISCUSSION...Deep moisture is in place over Southeast Arizona,
with a high pressure center consolidated just east of our area and
a favorable southerly flow over the area. Precipitable water
values between 1.6 and 1.8 inches are well above the 90th
percentile for late August. Add in a mid level impulse immediately
south of our area in northern Sonora, and upper level diffluence
on the eastern periphery of the upper ridge axis and we have a
good recipe for showers and thunderstorms that don't follow a
typical diurnal cycle. Plenty of convection around this morning,
with a chance of showers and thunderstorms continuing into the
evening hours. With this much moisture and relatively modest storm
movement, the main focus will continue to be an elevated risk for
heavy rainfall and localized flooding issues.

We'll continue to maintain enough moisture for a decent chance of
showers and thunderstorms into the weekend. A trough pushing
through the northern Great Basin may introduce a westerly
component to the flow over at least western and northern portions
of our area early next week. Probably enough to slow storm
development once again, especially if the high responds by
temporarily elongating back westward in an east-west oriented
axis. If the trough gets deep enough early next week, the ridge
might even sink to a blocking position over northern Sonora. That
would bring a day or two of zero storm coverage by Wednesday or
Thursday.

&&

.AVIATION...Valid through 24/12Z.
Scattered TSRA/SHRA, with a possible increase this afternoon.
MVFR and local IFR conditions with brief gusts approaching 50 kts
with strongest TSRA. Otherwise, cloud decks generally 8k-15k ft
AGL and surface wind variable in direction mainly less than 12 kts
into Thursday evening. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...A favorable pattern for thunderstorm development
will continue into this weekend. Expect heavy rainfall to occur at
times. Terrain driven 20-ft winds persist at less than 15 mph,
except gusty and erratic winds near thunderstorms. A gradual drying
trend with less daily thunderstorm coverage may occur next week.

&&

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

&&

Meyer/Rasmussen

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