Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 121017

Area Forecast Discussion
National Weather Service Boise ID
317 AM MST Thu Dec 12 2019

.SHORT TERM...Today through Sunday...Moisture will continue to
flow over the region on zonal flow through Saturday morning. We
will continue the Winter Weather Advisory for snow for the
mountains, which runs through 12Z Friday. The most significant
change in the forecast this morning is the introduction of a
slight chance of thunderstorms this evening over mainly northern
and eastern sections of the CWA. The SPC in Norman, OK has put
much of our area in a category known as "general thunder". This
simply indicates that conditions are favorable for thunderstorms,
but not for severe storms. We will see instability increase late
this afternoon and peak this evening as colder air moves in aloft.
We do not expect lots of storms, but certainly can`t rule out a
few cells and therefore chose to include a mention of a slight
chance of thunderstorms from roughly 5 pm MST to 11 pm MST. Heavy
snow has been occurring in the mountains this morning, with
Brundage receiving close to 4 inches, Bogus Basin 5, and Tamarack
close to 6. At slightly lower elevations, McCall has received
around 2 inches so far. More is expected today, with totals
through 11 pm MST Friday forecast to be near a foot at Bogus, 8 to
10 inches at Tamarack and Brundage, and 4 at McCall. McCall`s
precipitation type may change to rain this afternoon, limiting
their snowfall total, as they are right on the predicted rain/snow
line. If they manage to stay all snow, they will get 6 to 8
inches. A cold front will sag south over the region late today,
bringing lower snow levels and colder temps for tonight through
the remainder of the short term. Snow levels will fall from a
range of 5000 in the north and 7000 in the south this morning to a
range of 3000 in the north and 5000 in the south Saturday morning.

After this first main push of moisture passes through, the focus
will shift to the southern part of the CWA, where snow is forecast
to increase late Friday and continue into Saturday morning. At
this time, it does not appear that there will be enough snow to
warrant an advisory, but that doesn`t mean there won`t be areas of
slick roads. Anyone planning travel on SH 95, 51, or 93 Friday
night or Saturday morning should be prepared for wintry travel
conditions. Total snow for the higher elevations in the south will
range from over a foot on top of Steens mountain, to near a foot
in the Owyhees, to 6 to 10 inches in the mountains of southern and
southeast Owyhee County and southern Twin Falls County. Lower
elevations in these areas will see 1 to 3 inches along the state
highways listed earlier. These amounts will fall from this morning
through Sunday, with the bulk falling Friday into Friday night.

Saturday, snow will become less likely and accumulating snows will
be confined mainly to the mountains. After seeing temps around 10
degrees above normal today, readings will only be around 5 degrees
above normal Friday, and then just a degree or two above normal
Saturday. Cooling continues through Sunday, when temps will be
near normal.

.LONG TERM...Sunday night through Thursday...Northwest flow sets
up over the Intermountain West on Sunday night as the trough
progresses eastward. A ridge builds off the Pacific Coast through
Wednesday as conditions stay mostly dry. Model solutions split on
Thursday over the progression of an upper trough as it approaches
the coast. A chance of rain and snow showers was maintained across
the region as there appears to be ample moisture. Temperatures
will remain a couple degrees above normal through the period.


.AVIATION...Mountains obscured. Widespread MVFR and local
IFR/LIFR conditions in rain, snow, and low ceilings continuing
through the afternoon. Snow levels 3500-4500 ft MSL. Surface
winds southeast- southwest 10 kts or less becoming west- northwest
around 10 kts this afternoon. Winds aloft at 10k ft MSL: west
40-50 kts becoming west-northwest 30-40 kts after 18z/Thu.


ID...Winter Weather Advisory until 5 AM MST Friday IDZ011-013.



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