Area Forecast Discussion
Issued by NWS Boise, ID
FXUS65 KBOI 101615
Area Forecast Discussion
National Weather Service Boise ID
915 AM MST Sat Dec 10 2016
.DISCUSSION...As seen on KCBX radar pcpn was ending from the
northwest as of 8 AM MST. We have cancelled all winter weather
advisories and updated forecasts. Pops have been lowered in
Oregonzones and western-most idaho zones. Weak cold front now
passing through our CWA from wnw to ese. Pcpn will decrease in
south-central Idaho this afternoon. The cold front will bring
cooling to higher elevations but slight warming at low elevations
as it scours out colder air trapped in the lowest valleys.
Chance of snow showers will continue in northern-most zones
through Sunday from moisture still coming in from the northwest
coast. Next mid-latitude Pacific storm progged to bring pcpn
to our southern zones Tuesday, with pcpn continuing into Friday.
GFS and ECMWF have arctic surge into our area Friday and Saturday.
.AVIATION...Varying MVFR-IFR and some VFR conditions expected at most
locations through the day. Rain/snow ending from NW to SE by 11/00Z.
Valley fog is likely 11/06Z - 11/18Z. Surface winds: varying
directions, but under 10 kts. Winds aloft near 10 KFT MSL: West 30-
40 kts, decreasing to 15-20 by 11/03Z.
SHORT TERM...Today through Sunday...Plume of deep moisture
responsible for the steady precipitation yesterday and overnight
will shift south through the day as a weak upper trough and
accompanying surface front track through the region. This will
bring an end to the precipitation across much of southeast Oregon
and the lower Snake Plain by noon. Showers will continue across
the mountains of southwest Idaho and Western Magic Valley through
the day. Cold air will remain trapped in the lower Treasure
Valley from Boise to Ontario/Vale and the Weiser Valley through
this morning. With temperatures of 30-32 degrees these areas will
continue to see freezing rain or in the Weiser Valley a mix of
snow and freezing rain. Expect precip intensity to decrease after
15Z this morning. Will see additional liquid amounts up to a tenth
of an inch during the morning which will add to the current ice
accretion on colder objects and untreated surfaces. Will continue
current advisories through 18Z this morning, minus Baker county
where little additional accumulation is expected after 12Z.
For tonight and Sunday slightly cooler northwest flow will keep
focus of snow showers in the east-central Oregon and west-central
Idaho mountains. Additional accumulations will be light.
Temperatures are slightly below normal on Sunday.
LONG TERM...Sunday night through Friday...An active weather pattern
still on track through the extended. Sunday night through Tuesday
zonal flow will be over the region with widespread mainly snow over
the forecast area. Tuesday night flow aloft will shift to a
northerly direction pushing most of the precipitation to the
southern half of the forecast area. Models differ on how dry the
northern half of the forecast area will get so will leave at least a
slight chance of precipitation. Wednesday through Friday models
differ on how to handle an area of low pressure and associated upper
level trough as is moves south. The Canadian is the outlier with no
run-to-run consistency, while the GFS and ECMWF are similar with the
latest trend a bit faster in shifting the axis of the trough to the
south. Models do agree that this weather pattern will bring much
colder air to the region so have lowered temperatures a few
degrees Thursday and Friday. Models do not agree on where
precipitation will be with the weather pattern for Thursday and
Friday so will trend pops toward climatology and wait to see what
later model runs do with the weather pattern.
PREV SHORT TERM...DG
PREV LONG TERM....JA