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Area forecast discussion 
National Weather Service Boise Idaho
834 PM MST Sat Nov 28 2015

Discussion...persistent weather next several days especially at low
levels where cold air is firmly established with areas of low clouds
and patchy fog. We have updated colder Sunday night and Monday to
reflect this persistence. A strong surface-based inversion has
formed. Above the inversion...near 6000 feet mean sea level...the air is
warmer and further gradual warming is expected through Tuesday as
high pressure aloft passes through. A weak Pacific storm Wednesday
will bring clouds and a slight chance of snow showers but will not
break the inversion. But a stronger storm Thursday night might do it.


Aviation...IFR and low MVFR in low stratus and fog over the snake
plain...Weiser basin...and areas of northern Harney County. Could
see patchy fog at kbke develop. Already seeing the stratus deck
build back over the western Magic Valley where it had briefly
cleared this afternoon. Will likely see similar afternoon erosion to
the stratus deck Sunday. Inversion conditions to persist into the
beginning of this week. Tops of stratus at kboi are about 1500 feet
above ground level. Surface winds generally 10 kts or less. Winds aloft at 10k feet
mean sea level...east 10-20 kts...becoming NE 5-15 by sun/18z.


Previous discussion...
short term...tonight through Monday...a cold stagnant pattern
expected to continue for the next few days. Some lingering cloud
cover from a cut-off upper low spinning in northern Utah may
impact southern Idaho...but upper high north of
the County Warning Area will dominate the weather through Monday. Fog and low
stratus from established inversion conditions are expected to
remain in place through the Treasure and Magic Valleys as well as
valleys in southeast Oregon. Brief breaks are possible in the late
afternoons...but with nightfall...conditions will likely
deteriorate once again. This will keep temperatures well below

Long term...Monday night through Saturday...upper level blocking
pattern begins to break down on Tuesday. This will allow for a
series of storm systems to push into the Pacific northwest next week...each one
making it further into the interior northwest with light precipitation.
Tuesday is dry with the inversion remaining in place and valley
temperatures staying well below normal. The first system to
make it to the interior arrives on Wednesday...bringing a slight
chance of snow showers to eastern Oregon zones and the west central
mountains a second wave follows for Thursday/Friday increasing chances for
light rain/snow across all zones. While the inversion will hold
through at least Wednesday do expect increased flow near the surface
to scour out any leftover low clouds and fog allowing for some
warming. Most noticeable warming in valleys will come Thursday/Friday as
cooling aloft breaks the inversion. An upper ridge builds back over
the area for Saturday.


Air stagnation...inversion conditions expected to continue
through possibly Wednesday. Mixing heights will remain below 1500
feet above ground level with light winds. Next upper low could impact the area late
in the week...which is the next best chance for the inversion to


Boi watches/warnings/advisories...



previous short term...ep
previous long term....dg/dd
air stagnation....ep

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