Area Forecast Discussion
Issued by NWS Spokane, WA

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314
FXUS66 KOTX 170003
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
403 PM PST Sun Dec 16 2018

.SYNOPSIS...
An active and relatively mild weather pattern is expected this
upcoming week. Light precipitation will continue through tonight.
A wetter and warmer system arrives Monday night into Tuesday
night with the potential for heavy mountain snows and valley
rains. A third system arrives Thursday into Friday. Drier and
cooler weather arrives at the end of the work week.


&&

.DISCUSSION...
Update: The winter weather advisory for the Okanogan Highlands has
been allowed to expired. The winter weather advisory for the
Cascades, however, has been extended until 8 PM with cameras and
short-range models suggesting the potential for impacts
continuing. Will continue to assess.


.PREV DISCUSSION... /issued 229 PM PST Sun Dec 16 2018/

Tonight through Monday:
An atmospheric river system has been impacting the forecast area
for much of the day. Most valley locations have seen predominately
rain during the day. The exceptions include in northern Idaho,
where Sandpoint and Bonners Ferry have seen light snow, and in the
east slopes of the Cascades, where cold air remains trapped,
bringing snow into the Methow Valley. We`ve gotten reports of
nearly half a foot of snow in Winthrop, several inches of snow
Leavenworth, and 1-2 inches in Sandpoint and Republic. This
precipitation is expected to gradually diminish in intensity and
coverage this evening and tonight, with a few mainly mountain
showers lingering into Monday. With the boundary layer now
saturated, low clouds and perhaps some fog are likely to develop
across the valleys tonight, and could persist into Monday. Dang

Monday night through Wednesday night:

..Wet and windy with heavy high mountain snow Monday night
thru Tuesday night...

The next storm system to pass with a well established and maintained
tap of subtropical moisture looks to pass through during this time
period. Precipitation spreads from west to east starting Monday
night and allows for a substantially wet and windy conditions
with heavy high mountain snowfall on into Tuesday night. One
slight exception to this involves lower snow levels in the East
Slopes of the Washington Cascades allowing for snow to accumulate
in many of the valleys there including the Winthrop and Twisp
river valleys until warming up thru the day Tuesday. Heavy high
mountain snow accumulations would translate west to east allowing
for additional highlights for the mountains of Northeast
Washington and over to the mountains of North Idaho that end in a
similar west to east fashion Tuesday night into Wednesday. The
amount of rainfall for midslope and lower elevations locations
during this period will be high enough to possibly allow for some
nuisance flooding, likely some ponding of water on and along some
roadways. In addition some rises on Paradise Creek (in the
Moscow/Pullman area) and the Stehekin river (East Slopes of the
North Cascades) are likely during this time period with peaks
expected on Wednesday. The more vigorous southerly/southwest
winds are expected to blow at ridgetop thru much, if not all, of
this time interval while lowland locations will see a peak of the
gustiness with the cold front passage Tuesday afternoon.

Thursday through Sunday:
A third atmospheric river system will likely impact the region
Thursday into Friday. This system appears to be similar in
strength to the current one, and weaker than the Monday-Tuesday
storm. Mountain passes could see moderate snow accumulations with
this system, and the valleys could see rain initially but
transition over to light snow toward the end of the event.

Medium-range models are trending toward drier weather late Friday
into Saturday. The next system is currently on track for a Sunday
arrival. Dang

&&

.AVIATION...
00Z TAFS: a system slipping across the region tonight will
continue to provide areas of rain and mountain snow, though it
will be decreasing from the west through 02-05Z, leaving mainly a
limited shower threat into the overnight over GEG/SFF/COE/PUW/LWS
area. Area of VFR/MVFR conditions will continue, with the
potential for IFR conditions developing behind the front into
Monday morning. Some improvement is possible again later Monday.
/Cote`




&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        37  43  37  46  36  43 /  90  20  90  90  60  20
Coeur d`Alene  36  41  36  43  36  41 /  90  40  90 100  80  30
Pullman        38  45  36  46  37  44 /  80  40  80 100  80  20
Lewiston       41  49  40  51  42  51 /  70  50  80  90  70  10
Colville       34  41  35  45  31  44 / 100  30 100  90  50  20
Sandpoint      34  39  36  42  36  40 /  90  70  90 100  90  50
Kellogg        35  39  36  41  36  39 /  90  70  80 100 100  70
Moses Lake     34  45  38  50  36  48 /  90   0  90  70  20  10
Wenatchee      32  40  36  44  37  44 /  90  10  90  80  60  20
Omak           34  40  36  42  32  42 / 100  10  90  80  50  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Winter Weather Advisory until 8 PM PST this evening for East
     Slopes Northern Cascades.


&&

$$



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