Damaging Wind in Arizona, August 16, 2018

Area Forecast Discussion
National Weather Service Tucson AZ
118 PM MST Thu Aug 16 2018

.SYNOPSIS...Scattered thunderstorms will diminish later this
evening with skies gradually clearing. Then fairly typical monsoon
conditions are forecast for Friday well into next week with the
exception of Sunday which may be mainly dry. After a relatively
cool afternoon today, warmer high temperatures are in the forecast
through much of next week.

&&

.DISCUSSION...Convection already developing across western Pima
county this afternoon and the storms are quick to produce decent
rains according to radar estimates. As we progress further into
the afternoon the coverage of thunderstorms is expected to
increase with a threat of a few of them producing very heavy
rains thanks in large part to the abundant moisture in the
atmosphere. A flash Flood Watch is in effect for the SW part of
the forecast area with the main area of concern being generally
west of I-19. The convection will die off fairly quickly this
evening after 7-8 pm with skies clearing during the overnight
hours.

By Friday afternoon the upper level high that is currently just to
our SE will have settled overhead 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 during the afternoon 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. At this
time Sunday looks to be be a significant down day convection wise
if the current models are anywhere near to being correct. Time
will tell. Afternoon temperatures will be near to or slightly
warmer than normal under this scenario and will vary a few degrees
each day depending on the amount and exact location of any
convection. Further out, the Climate Center's outlooks continue
to indicate somewhat wetter than normal conditions on average
through the next 3 to 4 weeks overall. Monsoon 2018 continues

&&

.AVIATION...Valid through 18/00Z.
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 with another BKN later AOA 20k
ft AGL. Tomorrow afternoon isolated to scattered -SHRA/-TSRA will
again be possible mainly from Tucson eastward. 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. Near or slightly below average temperatures will continue
through 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...
Flash Flood Watch until 8 PM MST this evening for AZZ501>504-507-
513>515.

&&

PUBLIC...Carpenter
AVIATION....Hardin
FIRE WEATHER...Hardin

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