Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Phoenix Arizona
805 PM MST Monday Jul 28 2014
drier air will move into the region Tuesday through late week...with
significantly reduced storm chances and hotter temperatures. Better
storm chances will eventually increase again Friday into the weekend
as moisture moves back into the southwest United States.
other than an isolated rain showers/ts percolating over higher terrain of
northern Pinal County...activity is virtually absent over the
forecast area this evening. A larger circulation center propagating
north into southern Nevada has brought a combination of deeper
subsidence and drying westerly flow aloft into the southwestern
quarter of Arizona. 00z ktwc and kpsr sounding data shows boundary
layer mixing ratios still lingering in the 9-11 g/kg range while
total column precipitable waters sit between 1.25 and 1.50 inches. However...a
notable shift in 700 mb-500 mb winds to a westerly direction and
introduction of less favorable midlevel lapse rates portend little
additional support for convective activity and mostly quiet
conditions for the remainder of the night. Therefore...have
significantly reduced probability of precipitation through Tuesday..while also making some
modifications of hourly temperatures based on current trends.
/225 PM MST Monday Jul 28 2014/
Tuesday through Sunday...a dramatic decrease the amount of
convection across the area...with the focus for any precipitation in
the mountains east of Phoenix through the middle of the week. Mean
bl mixing ratios drop to around 6 g/kg during the middle part of the
week and even climatology probability of precipitation may end up being too high. With drier air
working into the area middle week...temperatures will likely take a run into
the 105-109 range across the deserts. Consequently...there should be
a slight drop-off by the weekend as deeper moisture makes its way
back into the area. Still above 100 but somewhat lower than the middle
week values. Made slight reductions to probability of precipitation across the board from
Tuesday through Thursday based on latest guidance with the highest
values displaced well east of the deserts. The monsoon moisture
won\t be terribly far away...winds per the two-three most recent
runs of the European and GFS bring increased mixing ratios back into
the area Friday and almost certainly by the weekend. Precipitation chances
once again look favorable for the latter portions of the forecast
period although it\s still difficult to highlight one day vs another
until we get a little closer.
south-central Arizona including kphx...kiwa...and ksdl...
although an isolated ts will still be possible this evening
surrounding central Arizona...direct impacts on terminals are
unlikely. No other storms were noted in the southern or eastern parts of the
state...and light westerly or variable winds will likely prevail
longer into the overnight hours than previous nights.
Otherwise...only few/scattered middle/high clouds expected through
Tuesday...with storm chances Tuesday afternoon far lower than recent
Southeast California and southwest Arizona including kipl and kblh...
no aviation impacts expected through Tuesday afternoon with only
occasional middle/high clouds generally clearing through Tuesday. Storm
chances will be almost none beyond this evening through Tuesday.
Aviation discussion not updated for amended tafs.
Thursday through Monday...
drier than normal conditions expected through Thursday. Storm
chances will be slight and will be limited to the higher terrain of
eastern Arizona. Late in the week and over the weekend...an
increase in moisture and associated humidities is anticipated and
storm chances...though slight...expand to the lower elevations. High
temperatures trend downward as well.
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