Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Tucson Arizona
919 PM MST Thursday Jul 30 2015
Synopsis...enough moisture for a chance of showers and
thunderstorms for much of Southeast Arizona into next week.
Discussion...a few showers and thunderstorms continued across the
area late this evening. These will likely dissipate by midnight.
Current forecast looked on track...so no updates this evening.
Please refer to the additional sections for more details.
Aviation...valid through 31/06z.
Decreasing clouds...with a few clouds at 8-12k feet above ground level by 31/10z. Scattered-
broken clouds at 6-9k feet above ground level and broken clouds at 10-14k feet above ground level after
31/19z. Isolated -shra/-tsra over the higher terrain through 31/03z...with
scattered rain showers/thunderstorms and rain developing after 31/20z. Brief wind gusts to near 35 kts
possible in and around the stronger thunderstorms and rain. Outside of storm
influences...surface winds will generally be less than 12 kts with a few
higher gusts in the afternoon/early evening hours. Aviation
discussion not updated for taf amendments.
Fire weather...drying is then expected across the western half of
the forecast area into early next week...with isolated to scattered
showers and thunderstorms continuing over eastern areas. Strong
outflow winds will be possible near thunderstorms. Otherwise...20-ft
winds will generally be terrain driven and less than 15 miles per hour...with
some afternoon and early evening breeziness due to the strong
Previous discussion...even though we are drier than the past 12 to 24
hours...models show precipitable waters increasing Friday into the 1.5 - 1.7 inch
range as a weak disturbance moves up from the southeast late in the
day and potentially enhances activity. By Saturday a weak impulse to
our west moves to the north across western Arizona with precipitable waters around
1.4 -1.6 inches. So...I maintain a low grade monsoon forecast with
low end scattered activity for much of the forecast area Friday and
mostly central and eastern areas for Saturday.
By Sunday the models show high pressure centered either just to our
east or south (gfs has it over New Mexico and European model (ecmwf) extending from
eastern Pacific across central Baja California and northern sonora). Both
models show a drying trend with precipitable waters from the GFS down to about 1.2
inches. So...I have the best threat for showers and thunderstorms
between Tucson and the New Mexico border.
From Monday through Thursday the high will meander across the Desert
Southwest in some form or fashion. European model (ecmwf) has been the drier model
between the GFS and European model (ecmwf). For now I continue with a forecast on
Monday that is similar to Monday...but then each day thereafter
should be a Standard low grade monsoon forecast...with the best
threat between Nogales and Douglas as well as the mountain tops.
For Tucson...high temperatures will be slightly above normal Friday and
Saturday and 4 to 6 degrees above normal Sunday through Thursday...
although the warmest day should be Tuesday.
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