Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 250410

Area Forecast Discussion
National Weather Service Tucson AZ
910 PM MST FRI JUN 24 2016

.SYNOPSIS...Adequate moisture will be around through the weekend into
next week for daily afternoon and evening showers and thunderstorms,
especially south and east of Tucson. Daytime high temperatures will
run near normal.


.DISCUSSION...Water vapor imagery shows high pressure aloft centered
over the lower Mississippi river valley with the associated ridge
axis extending across Texas toward New Mexico. Meanwhile, a weak
shortwave trough axis resides across Arizona with a very distinct
demarcation between dry air to our west and moist air to our east on
the western flank of the ridge, but also ahead of a low over
northeast Mexico. Between these systems lies a deformation zone over
parts of Sonora and Chihuahua Mexico. IR satellite imagery from
earlier today shows convection that blossomed over the Sierra Madre
Occidentals of Mexico, with a large swath of cloudiness and
convection over much of northern Mexico, eastern Arizona and western
two-thirds of New Mexico.

Convection developed relatively early today at around noon, mainly
between Tucson and Nogales and into parts of Cochise county.
Rainfall amounts were light, generally under a tenth of an inch,
with some isolated amounts of around a third to near a half. The
winner with respect to rainfall was the Long Park gauge in the
Chiricahua mountains of east central Cochise county where 0.75
inches fell.

Current satellite and radar trends are indicating that the cloud
tops over northern Mexico have been warming and most of the showers
over my forecast area have dissipated. Still some activity south of
the border and in southwest New Mexico, but the trend is for the
showers to gradually dissipate through the remainder of the evening
and into the overnight hours. Will make some adjustments to the POP
grids for the remainder of tonight. Will leave in some slight
chances near the international border and our border with New Mexico
in case outflows from the south and east trigger additional activity
later on tonight. Elsewhere, not much if any, precipitation is
expected for the rest of tonight.

As of 03Z (8 PM MST), temperatures ranged from the mid 70s to the
mid 90s, with the Tucson intl airport reporting a temp of 92 degs,
after reaching an afternoon high of 103 degs. Will make some
adjustments to the short term hourly temperature grids to reflect
the most recent trends, but inherited overnight low temps seem to be

For details beyond tonight, please refer to the previous discussion


Isold -SHRA possible overnight, mainly near the border with Mexico
and New Mexico. Debris clouds will continue to cover the eastern
half of the forecast area overnight, but will slowly erode through
sunrise Saturday. Isold -TSRA dvlpg Sat after 25/19Z mainly E and S
of KTUS. Sfc wind will be vrbl in direction at less than 10 kts
overnight, but expect generally west to northwest flow at 15 kts or
less during the afternoon on Saturday. Winds potentially strong and
gusty near thunderstorms. Aviation discussion not updated for TAF


.FIRE WEATHER...Isolated to scattered showers and thunderstorms will
occur across southeast Arizona through next Thursday. The best
chance of wetting rains during much of the period will be east-to-
south of Tucson. 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 through Sunday as well as
next Wednesday and Thursday will generally be terrain driven at less
than 15 mph. 20-foot winds Monday and Tuesday will generally be from
the east at 5-15 mph with gusts of 20-25 mph. The strongest speeds
Monday and Tuesday should prevail from shortly after sunrise into
the early afternoon hours.


.PREV DISCUSSION...The synoptic scale pattern was defined by
longwave ridging over much of the CONUS with low pressure moving
into northwestern Montana, as well as another disturbance pushing
northwestward along the Mexico/Texas border. Over the next several
days, it looks as though this Mexican low will stall before slowly
starting to move eastward through Texas, rather than move in our
direction. This will allow high pressure take hold of the desert
southwest early next week, with the center of high pressure setting
up near the favorable four corners region (for daily convection) by
Tuesday/Wednesday. Thereafter, high pressure seems to wobble around
the southwestern states a little bit, but overall remain in a good
position to ensure daily chances for monsoon activity. Showers and
storms this weekend will do well to moisten up the lower levels of
the atmosphere, so we will probably be looking at better coverage of
measurable precip and some higher QPF`s by the middle to end of next

Bottom line is a general ramp up in shower and storm coverage
through the weekend which will persist into next week. The forecast
challenge will then shift to determining which days will be "up" or
"down" in terms of coverage and storm severity. Temperatures will
generally remain near normal though the forecast period.






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