Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Boise Idaho
251 am MDT Sat Sep 5 2015
Short term...surface cold front moved through our County Warning Area from west to
east late Friday and Friday evening with gusty winds...showers...
and thunderstorms. Front is now east of our County Warning Area and all areas are
colder than 24 hours ago. At 08z satellite showed the upper low
in eastern Oregon. Instability showers were present in most of eastern
Oregon. Models take the upper low toward the northeast today with
the showers moving into western Idaho. Model consensus has high probability of precipitation
today in our northern zones...mid-range probability of precipitation in central zones...and low
probability of precipitation near the Nevada border. GFS probability of precipitation are considered a low outlier.
Cooling lower levels have stabilized the air mass and model
convective parameters are weaker for this afternoon than they
were Friday afternoon. We therefore have removed thunder from the
forecasts. Snow level will be low enough...near 6000 feet mean sea level...for
an inch or two accumulation on mountains in the path of the upper
low. As the low moves northeastward the rain and snow showers will retreat
into central Idaho tonight and gradually decrease through Sunday
morning in Eastern Valley County/ID. Clearing skies and light winds
will allow good radiational cooling tonight leading to the coldest
morning of the season Sunday. Relatively moist air will limit the
cooling however. Have included patchy fog in northern valleys Sunday
morning. Will continue the Flash Flood Watch for northwestern Malheur
County and southern Baker County as those places are still in the area of
greatest expected precipitation today.
Long term...Sunday night through Friday...northwesterly flow will
develop over the Pacific northwest Sunday night as an upper level
trough shifts east of the forecast area. This northwesterly flow
will bring dry conditions to the region through the rest of the
week. Flow aloft will briefly shift to westerly Tuesday through
Wednesday as two weak troughs move across southern Canada. Any
precipitation with these two troughs will remain well north of the
forecast area. Northwesterly flow aloft will return Thursday night
as a ridge of high pressure builds just off the West Coast.
Temperatures will slowly warm through the week with highs around 10
degrees below normal Monday...near normal on Wednesday...then
around 10 degrees above normal by Friday.
Aviation...across Baker County and central Idaho...mountains will
be obscured along with widespread rain and high elevation snow.
Areas of MVFR and local IFR conditions in heavier showers. Rest of
the forecast area will see scattered showers with local MVFR
conditions in heavier showers. Surface winds westerly 10-20 knots
with gusts to near 25 knots across southeast Oregon and the Magic
Valley. Winds aloft westerly around 10 knots surface to 5k feet
mean sea level...becoming southwesterly around 30 knots above 5k feet mean sea level.
Weekend outlook...decreasing precipitation tonight with patchy
valley fog Sunday morning. VFR conditions Sunday with decreasing
Or...Flash Flood Watch through Saturday morning orz062-063.