Area Forecast Discussion
Issued by NWS Boise, ID

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
000
FXUS65 KBOI 140347
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
847 PM MST Wed Dec 13 2017

.DISCUSSION...Stratus has eroded from the west more rapidly than
expected, and an update will be out shortly. There remains much
uncertainty concerning fog formation in the areas where the
stratus has departed (most of southeast Oregon and much of the
Lower Treasure Valley of Idaho). For now, will put in patchy fog
where stratus has vacated, but would not be surprised to see dense
fog form in these areas tonight.

&&

.AVIATION...Widespread fog and stratus will continue overnight,
with most locations expected to deteriorate to IFR/LIFR conditions
by 06Z. Surface winds will be light and variable. Winds aloft
will be northerly, averaging 15kt through 10K ft MSL. Expect the
stagnant upper level pattern and associated surface-based
inversion to persist through Friday afternoon.

&&

.AIR STAGNATION...Inversion will hold through Friday and most
likely be broken Friday night into Saturday as a moderate cold
front moves through. Air quality will not improve until then. Air
Quality Alert remains for Burns, Baker City, and Ontario, and
surrounding areas.

&&

.PREV DISCUSSION...
SHORT TERM...Short wave trough and scattered light snow showers
passed through Idaho zones this morning, and was already out of our
CWA by noon.  The trough weakened the inversion and decreased the
fog, but the inversion is still there.  Any light snow that
accumulated today will lower temps slightly tonight and help fog
re-develop.  Dense fog is possible but not sure where it will form,
so no dense fog advisory will be issued with this package.
Otherwise, persistence still looks like the best forecast through
Friday before a stronger upper trough and surface cold front from
the Gulf of Alaska reach the northwest coast.  That system will bring
a slight chance of snow showers to northern-most mountains as early
as Friday afternoon.  Light winds.

LONG TERM...Friday night through Wednesday...An upper level trough
and associated cold front will push through the region Friday night
and Saturday morning. Increased wind speeds and cold air aloft will
work to mix out the inversion that has been in place for so long.
Temperatures in the valleys will rise and temperatures in the
mountains
will fall to about normal. Most locations will see a dusting of snow
with this feature by Saturday morning, while mountains will see no
more than an inch. By Saturday afternoon, a cold northwesterly flow
aloft will set up in the trough`s wake, keeping a slight chance of
precipitation across the east-central Oregon and west-central Idaho
mountains. While there will be a few degrees variation in the max
and min temperatures each day through the extended, temps will
stay within a few degrees of normal.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.

&&

$$

www.weather.gov/Boise
www.facebook.com/NWSBoise
www.twitter.com/NWSBoise

DISCUSSION...SP
AVIATION.....MT
AIR STAGNATION...SP
PREV SHORT TERM...LC
PREV LONG TERM....AB/WH



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.