Area Forecast Discussion
Issued by NWS Tucson, AZ
FXUS65 KTWC 220356
Area Forecast Discussion
National Weather Service Tucson AZ
856 PM MST THU JUL 21 2016
.SYNOPSIS...Hotter and drier conditions are expected Friday into
Sunday with some record high temperatures likely to fall. There will
be just enough moisture around for a few storms near the Mexico and
New Mexico border each of those afternoons. Then moisture will
increase across much of the area early next week for an increase in
storms and somewhat cooler afternoon temperatures.
.DISCUSSION...Satellite and radar trends show lingering showers and
thunderstorms continuing to move in from the east across parts of
Greenlee, Graham and Cochise counties as they move to the west
northwest. A few lingering showers and storms also over parts of the
Tohono O`Odham nation, not to mention some isolated activity south
of the border. We should see a gradual decrease in shower and
thunderstorm coverage through the remainder of the night. Made some
minor tweaks to the POP grids to reflect these recent trends.
As of 03Z (8 PM MST), temperatures across the region ranged from the
upper 70s to the upper 90s, with the Tucson International Airport
reporting a temp of 94 degs, after achieving an afternoon high of
107 degs, which was 8 degs above normal for this date. The inherited
overnight low temperature forecasts seem to be fine, but will make
some adjustments to the short term hourly temperature grids to
reflect the most recent trends.
For details beyond tonight, please refer to the previous discussion
.AVIATION...VALID THRU 23/06.
Isolated showers and thunderstorms will continue mainly along the
border with New Mexico and also along the immediate border with
Mexico as a complex over Sonora helps to keep isolated convection
going mainly south of the border tonight, but can`t rule out
outflows triggering additional isolated showers and/or storms into
the early morning hours. Ceilings generally above 12K FT, although
lower ceilings expected near thunderstorms. Expect slightly lesser
showers and thunderstorms on Friday afternoon and early evening as
drier air from the east continues to push west. Winds generally
light with typical diurnal trends, except near thunderstorms where
winds will be variable and gusty. Aviation discussion not updated
for TAF amendments.
.FIRE WEATHER...Daily rounds of showers/thunderstorms will
linger into the weekend with coverage waning Saturday and Sunday.
A greater chance of storms will move into the area early next week.
Outside of gusty thunderstorm outflows, 20-foot winds will be
terrain driven and mostly less than 15 mph.
.PREV DISCUSSION...Friday and Saturday drier air invades the
region which is currently on our door step looking at the water
vapor loop. The overall result of this will be a reduction in the
convection and resultant cloud cover with much of it being limited
to our eastern and southern border areas. The other affect of this
will be to allow afternoon temperatures to increase the next few
days peaking Friday and Saturday afternoons about 10 degrees above
average and at or slightly above records for several locations. I
tweaked pops down a bit a few areas and added a degree to the high
temperature to many areas on Saturday.
On Sunday lower level thickness values begin to drop back with
moisture beginning to increase from the south. This is basically
beginning to occur thanks to a nudge from the tropics but at this
time believe the main push of moisture will be Sunday night into
Monday. So for now only made minor adjustments to the pops Sunday
and went with about 5 degrees of cooling for the afternoon when
compared to Saturday.
For Monday onward, nudged pops upward with the current trend in the
models and introduced chance of storms to the western deserts
throughout the week. May need to adjust them up further early in the
week but will wait a bit and see how this begins to unfold. I also
nudged afternoon high temperatures down a couple of degrees but
there is potential to nudge them down further one or two of those
days depending on the moisture surge. Still have a decent amount of
discrepancy in the lower level thickness forecast in the models with
the ECMWF being on the cooler side.
Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson