Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Boise Idaho
951 am MST Monday Dec 9 2013
Discussion...local wind chill values between 20 and 30 below zero
are still occurring in the southwest Highlands and southern Twin
Falls County...so will let the wind chill warning ride until the 11
am MST expiration. Light snow has been falling in the west central
mountains...including McCall. Latest models show the light snow will
continue through the afternoon. Have already updated the forecast to
account for this by raising probability of precipitation in the north. Remainder of the
forecast is in good shape.
Aviation...VFR. Except MVFR light snow and mountain obscuration
will continue through the west central mountains including McCall
through 5 PM tonight. Elsewhere expect mostly clear skies. Light
surface winds. Winds aloft at 10k feet mean sea level...northwest 15-25kt.
short term...today through Tuesday...coldest temperatures of 20
to 25 below zero as of 3 am were across Harney County and the
Camas Prairie including Fairfield and Burns. Wind chill values
across south central Idaho were in the -15 to -25 range with parts
of the west Magic Valley near warning criteria. Wind chill warning
for Camas Prairie and south parts of Owyhee and Twin Falls County
will remain up. Winds from Mountain Home to Twin Falls were
around 10 miles per hour and lows have been around zero to 5 below there as
well as across central Idaho mountains where moisture was on the
increase per water vapor imagery. A weak upper level disturbance
will bring snow showers across Valley County today and another
will affect that area Tuesday. Infrared loop showed clouds from the
Panhandle to NE Oregon...and infrared radiative temperatures around -35
across most of southeast Oregon and the high terrain of the south half of
Idaho. Temperatures will be slow to recover today in Idaho due to
the cloud cover...and light flurries in the central mountains.
This in contrast to large 35 to 45 degree expected diurnal range
in Harney County. Strong high pressure will dominate surface
pattern in short term as upper level ridge axis remains to the
west...for temperatures well below guidance and light winds except for
the northwest Magic Valley where a moderate NE wind is expected to
Long term...Tuesday night through Monday...lowered the temperatures
through Thursday especially in the valleys due to the cold Arctic
air in place. Models tend to erode cold pools too fast in areas of
terrain because of terrain following coordinates within the model.
Thus do not believe it will warm up as rapidly as the models suggest
with the ridge building in our area. A weak shortwave will move
through the area Friday morning and the system is cool enough to mix
out the atmosphere even in the lowest valleys for milder
temperatures. Precipitation amounts with this system are light and
should be focused on the higher terrain. After the passage of the
shortwave on Saturday morning another dirty ridge will build into
the area for drier and mild conditions.
Idaho...wind chill warning until 11 am MST this morning idz015-030.
Wind chill warning until 11 am MST this morning idz028.
previous short term...vm
previous long term....ka