Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Tucson Arizona
230 PM MST Tuesday Jun 2 2015
Synopsis...strong high pressure aloft will continue the above
average temperatures through at least middle week. Dry most of the
week...then a moisture increase from the south may bring a chance of
showers and thunderstorms by weekend into early next week.
Discussion...SW flow aloft over the area today with high pressure
to our south and an upper level trough over the Pacific northwest. Highs so far
today have been running a degree or two cooler than Monday.
Wednesday...energy currently moving through the Gulf of Alaska today
will deepen upper level trough over the West Coast. Some middle to high
level moisture will be pulled from a weakening hrcn Andres and
spread toward northern Baja California by late the day. Otherwise highs will be at
or slightly cooler than what will occur today.
Thursday...West Coast upper level trough continues to deepen with a
closed low developing near Frisco. This will increase SW flow aloft
over the state with middle to high level moisture from Andres moving
across the state. With model cross sections showing the low levels
being on the dry side...any showers or thunderstorms that develop
will be high based.
Thursday night into Friday...models fairly similar on placing upper
low over the la basin with dynamics aloft increasing over the area.
At this time GFS/ECMWF/NAM all show best dynamics being west of
Tucson closer to the low.
Based on latest model trends we have the right set-up...upper ridge
to our east and upper level trough to our west...to have moisture
pulled north across the area from the tropics this weekend into
early next week from ts/hrcn Blanca. Can't hang my hat on any
operational model run yet with the GFS still the wettest model
versus the ECMWF/Canadian. Still plenty of time for the models to
come more in line and thus the forecast will be tweaked accordingly.
Aviation...valid through 04/00z. Sky clear with breezy SW afternoon winds
around 12 to 18 kts...gusting to around 20 to 30 kts. Strongest
winds near kdug and kols. Winds diminishing after sunset. This
evening winds will become light and terrain driven through
03/17z...W/SW winds will begin to pick up again thereafter at kdug
and kols...around 3/19z at ktus. Strongest winds will again be at
the southern terminals. Aviation discussion not updated for taf
Fire weather...dry conditions will prevail through Thursday.
Daytime minimum relative humidity values will mainly be in the
single digits to middle teens. 20-foot winds will generally be west
to southwest at 10 to 20 miles per hour with gusts to 25 to 30 miles per hour during the
afternoon and early evening hours. Expect light and variable winds
at other times.
Thereafter...increased moisture will bring a slight chance of
showers and thunderstorms Friday through Monday. There is
considerable uncertainty regarding the extent of this expected
increase of moisture across the area. Thus...the forecast of
rainfall probability...coverage and amounts will be subject to
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