Scientific Forecaster Discussion
fxus65 ktwc 222200
Area forecast discussion
National Weather Service Tucson Arizona
300 PM MST Thu Aug 22 2019
Synopsis...a more active monsoon pattern will occur through
this weekend with temperatures returning to near or slightly below
normal. High pressure builds back overhead for the first half of
next week which will usher in drier conditions along with above
average temperatures. Another chance for showers and thunderstorms
will then exist toward the latter half of next week.
Discussion...as expected, isolated convection has developed
across the higher terrain early this afternoon. The increase in
moisture which is helping to fuel our storms today is also keeping
temperatures from reaching record levels once again, with values
generally running 3 to 6 degrees cooler than 24 hours ago. That
said, still expecting Max temps this afternoon to top out 4 to 7
degrees above normal.
Expect showers and thunderstorms to increase in coverage into the
early evening hours, especially with colliding outflows and
subsequent storm development. A few storms will be strong or severe,
primarily producing gusty winds and isolated heavy downpours, as Storm Prediction Center
mesoanalysis valid 22/21z shows dcape between 1300 and 1900 j/kg and
up to 1.3" precipitable water over most of southern Arizona. With how hot and dry its
been the last several days, expect especially the stronger outflows
to kick up some dust with reduced visibility at times.
Another shot of reinforcing moisture is expected to arrive Friday
which will push chances for showers and thunderstorms up even more.
We'll have to see how things unfold particularly Friday night into
Saturday morning, as remnant cloudiness from convection could do well
to inhibit development on Saturday afternoon. For what its Worth,
temperatures this weekend will peak at or even slightly below
normal. This more typical monsoon pattern will be short-lived, as
models indicate high pressure setting up overhead early next week
which will dry things out and allow the return of very hot
Thereafter, particularly from next Wednesday Onward after a few days
of sustained easterly flow aloft, moisture looks to once again
return along with an uptick in convection and a cooling of
Aviation...valid through 24/00z.
Few-scattered clouds at 10k-14k ft mean sea level west of ktus and scattered-broken clouds
south and east of ktus through the forecast period. Isolated to
scattered thunderstorms and rain/rain showers primarily from ktus/kols eastward with brief
MVFR vsby/cigs possible, particularly near terrain. Precip
decreasing this evening though a few -shra could linger overnight
near the international border including kdug/kols. Gusty outflow
winds are possible near thunderstorms and rain/rain showers up to around 40 kts. Otherwise,
surface wind mainly southwesterly to westerly around 7-14 kts becoming primarily southerly
overnight. Thunderstorms and rain/rain showers redevelop Friday afternoon. Aviation discussion
not updated for taf amendments.
Fire weather...mainly afternoon and evening thunderstorm chances
increase to include much of Southeast Arizona into the weekend
before drier weather returns early next week. The return of deeper
monsoonal moisture will allow temperatures to fall back to near
seasonal levels by Friday which will remain through the weekend
before warmer temperatures return next week. The return of high
pressure early next week will allow temperatures to rebound back
above normal for a few days. As is typical this time of year,
thunderstorms may produce gusty and erratic outflow winds.
Otherwise, 20-ft winds will generally follow normal diurnal trends
at less than 15 mph.