Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 261640

Area Forecast Discussion
National Weather Service Tucson AZ
940 AM MST SUN JUN 26 2016

.SYNOPSIS...We now have enough moisture for isolated to scattered
showers and thunderstorms this weekend. A more favorable flow
regime will then provide increased coverage of showers and
thunderstorms Monday through next Saturday.


.DISCUSSION...Still plenty of debris cloud this morning with
embedded light showers. This is going to slow the heating a bit
with initial clearing underway in portions of Cochise and Santa
Cruz counties. The 12Z KTWC sounding still has plenty of moisture
at 1.4 inches precipitable water. The mid level easterly flow has
already increased substantially accompanied by an increase in
shear that should help to organize outflow activity this
afternoon. The direction favors strong outflow off the Mogollon
Rim through Graham county.

Latest HRRR trends push 2 strong outflows westward, including the
Rim shot and a second outflow from activity in Cochise county
pushing west and northwestward. The 12z UofA WRF-NAM paints a
similar scenario with the outflow from the Cochise county activity
pushing through the Tucson Metro area around mid to late
afternoon. Minor adjustments to increase activity in the east
central mountains and subsequent outflow westward, otherwise we
have solid forecast trends. Please see the previous discussion
below for additional details.


Isolated to scattered -TSRA/-SHRA. The best timing for TSRA at
the KTUS/KOLS/KDUG terminals is mostly from 20Z this afternoon
until 27/02Z this evening. Brief wind gusts to near 40 kts and
MVFR conditions due to reduced visibilities will be possible with
the stronger TSRA. Isolated -SHRA/-TSRA will be possible area-wide
late tonight into early Monday morning. Otherwise, cloud decks
generally ranging from 10k- 15k ft MSL, and surface wind terrain
driven mainly less than 12 kts. Aviation discussion not updated
for TAF amendments.


.FIRE WEATHER...Expect isolated to scattered showers and
thunderstorms this afternoon and evening. Greater coverage of
showers and thunderstorms should then occur Monday through next
Saturday. Otherwise, daytime minimum relative humidity values will
generally range from the mid teens to around 30 percent with fair
to good nighttime recovery. 20-foot winds into Monday as well as
Thursday through Saturday will be terrain driven at less than 15
mph. 20-foot winds Tuesday and Wednesday will generally be from
the east at 5-15 mph with gusts of 15-20 mph. The strongest speeds
Tuesday and Wednesday should prevail from shortly after sunrise
into the early afternoon hours.


.PREV DISCUSSION...The hi-res models suggest a scenario late
tonight similar to that presently occurring across the area. In
other words, a fairly widespread convective debris cloud cover
with patches of sprinkles or light rain.

26/00Z GFS/ECMWF/CMC remained fairly similar regarding the synoptic
scale pattern regime over the southwestern states starting Monday
and continuing into early next weekend. Strong high pressure aloft
Monday is progged to become centered over southern Utah. The GFS/
ECMWF depict an inverted trough to move into southwestern AZ from
the northern Gulf of California Monday.

Quick glance at the U/A WRF-NAM suggests that showers/tstms Monday
afternoon would only be confined to the White Mountains and near the
international border adjacent Santa Cruz/southern Pima County. Thus,
there is the potential that Monday may be a "down day" perhaps due
to subsidence on the eastern periphery of the aforementioned
inverted trough. Forecast confidence in this particular detail is
somewhat low, however. Thus, for this forecast package, have
continued with scattered showers/tstms mainly from Tucson

Thereafter, not much daily variation in shower/tstm coverage is
anticipated Tuesday into next Saturday. The deterministic GFS/ECMWF/
CMC were similar with maintaining fairly ample moisture across this
forecast area. These solutions were similar with the continuation of
a light ely/sely mid-level flow regime thru about Wednesday. The mid-
level flow regime is then progged to become more wly/swly especially
from Tucson westward starting Thursday and continuing into next
Saturday. This subtle change may be sufficient for at least a slight
downward trend in shower/tstm coverage, especially across western
sections. Again, forecast confidence is fairly low at this time in
stating that a definitive downward precip trend anywhere in the area
is in the offing late this week.

High temps for the Tucson metro area and locales west-to-northwest
of Tucson will be near normal during much of this forecast period.
However, daytime temps for locales east-to-south of Tucson, such as
Safford, Douglas and Nogales will average a few degs below normal
this week.






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