Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Boise Idaho
315 am MDT Friday Jul 29 2016
Short term...today through Saturday...northwest flow aloft today
keeps most of the forecast area dry, with temperatures about 10
degrees above normal. Monsoon moisture may just be barely able to
squeeze a thunderstorm north of the Nevada border into southeast
Oregon. However on Saturday, developing trough in British
Columbia turns the flow direction just slightly more southerly,
and allows this moisture to creep north. At the same time, the
approaching troubh is increasing from the westerly component of
the flow, so moisture wont be in the forecast area very long.
With temperatures so warm, instability should be plenty to
support isolated thunderstorms, and perhaps approaching scattered
coverage on Saturday afternoon and evening. We pulled the
thunderstorm threat a little bit further south, thinking that the
westerly flow will probably win out and keep thunderstorms out of
the northern half of the forecast area.
Long term...Saturday night through Thursday...isolated
thunderstorms near the Nevada border in Oregon and over the higher
terrain south of the Snake River Valley in Idaho will end Saturday
night as increasing westerly flow aloft transports monsoon moisture
out of our area. An upper level trough moving east across southwest
Canada will bring cooler air to our area on Tuesday, lowering high
temperatures by around 10 degrees. Precipitation with this system is
expected to stay mainly north of the Canadian border. Dry westerly
flow aloft will follow, with near-normal temperatures.
Aviation...VFR under mostly clear skies, except for smoke layers
and MVFR visibilities in the Lowman area and surrounding valleys.
Also expect patchy smoke in the Snake River Valley this morning.
Isolated thunderstorms will form near the Nevada border this
afternoon and continue through this evening. Surface winds variable
10 kts or less this morning becoming northwest 10-15 kts this
afternoon. Winds aloft to 10k ft msl northwest 15-25 kts.
Weekend outlook...mainly VFR. Areas of smoke will continue in the
Boise Mountains, filtering into the Snake River Valley during late
night and morning hours. Expect isolated thunderstorms Saturday
afternoon and evening over the Boise Mountains, the higher terrain
south of the Snake River Valley, and southeast Oregon south of a
kbno to Jordan Valley line.