806 
FXUS66 KOTX 162334
AFDOTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
334 PM PDT Sun Mar 16 2014

.SYNOPSIS...
A mild early evening under southwest flow will be followed by a
strong cold front passage late tonight and Monday. This will
increase the chances for rain and mountain snow...as well as
produce very gusty winds tonight through Monday. Drier weather
returns Tuesday, but another threat of precipitation will be
possible by the middle of the week. Temperatures will remain above
seasonal norms through the middle of next week.

&&

.DISCUSSION...

Tonight through Mon: With the next cold frontal boundary
crossing the Cascades beginning this evening, our focus will
shift to the Nrn Wa zones overnight as winds begin to back to a
more southerly direction and enhance isentropic ascent over the
warm front that will stretch west-to-east across Nrn Wa. This
ascent is not deep and, with winds veering to westerly south of
the warm front, our best chance of pcpn overnight will be near
the Cascade crest and across Far Ern Wa and the N Id Panhandle. Snow
levels should remain high enough in the E Slopes of the Cascades
to not produce heavy accumulations for most valley locations.

As the quick-moving, but strong short-wave trough moves into Ern
Wa overnight, large-scale ascent increases rapidly along and ahead
of the vort max. Though the GFS is one of the deepest with this
low, and shows cyclogenesis that even exhibits a trowal structure,
the heaviest influence on pcpn production will likely be deep
instability, cyclonic convergence and upslope into the Id
Panhandle late tonight and Monday. Not only will this prolong
showers Monday for the area, bit will also help to lower snow
levels. We should see a mix of rain and snow showers Monday morning
even for the lower valleys (Spokane included). Graupel or even
small hail will be possible Monday. Thunder is not out of the
question. We've issued snow advsys to take into account the
lowering snow levels and the aforementioned upslope and
instability for the Cntrl Idaho Panhandle Mtns and the Camas
Prairie. For the wind advsy...Pressure gradients will strengthen
quickly tonight and, given the nearly unidirectional WNW profile
of 35-45kt winds through a deep layer of CAA across the entire
region, very gusty winds will be likely. bz

Monday night through Wednesday: The pattern remains active. One 
system pulls away early in the period, offering a brief lull in
the shower threat, before the next frontal wave moves in late
Tuesday night into Wednesday. Regarding the latter system, models
have been back-and-forth over the timing and some uncertainty
remains. More on that in a moment. Temperatures are expected to be
near normal.

First Monday night into Tuesday low pressure pulls into the Plains.
The inverted surface trough trailing it into the northern Rockies
to central WA weakens as high pressure builds in. The northwest
flow and exiting upper impulse, in tandem with the weakening
surface trough, will keep the threat of a few showers going across
southeast WA through the central Panhandle and the Cascade crest
but the threat will wane into early Tuesday. By late Tuesday
afternoon, however, clouds will begin to stream in ahead of the
next system and a chance of precipitation will increase near the
Crest of the Cascades. The winds that blow on Monday are expected
to remain in the breezy category Monday evening, at least early
on, but these too should abate through the later evening into
Tuesday morning. I add some patchy fog in the sheltered north and
east valleys, the L-C valley and along the higher Palouse.

Tuesday night into Wednesday the next frontal wave is expected to
slide through. Over the past few days models have exhibited wide
swings over when it passes. Earlier model runs indicated the
system passed around this time, then backed it off to Wednesday
night or Thursday. Now some models bring it back to the late
Tuesday night into Wednesday time frame, others keep it at the
slower time (particularly the EC), while some start to bring
leading warm front precipitation toward northeast WA and north ID
as early as Tuesday afternoon. The middle-ground approach favors
the late Tuesday night/Wednesday time frame. So I increased PoPs
in this time frame. I kept the primary precipitation threat near
the Cascades Tuesday evening, then expanded some into the
northeast WA/north ID mountains overnight. PoPs were increased
Wednesday as well. However with continued model disagreement with
regard to the precise timing, I kept the likely PoPs limited to
the Cascades and mountains. However PoPs will be above average,
especially toward northeast WA.

As for snow levels: these are projected to be between 2000 to 3000
feet over the counties along the Canadian border (with the lowest
closer to the Canadian border itself) and 3000-4000 feet elsewhere.
However some snow may mix with rain below these elevations,
including along the Highway 2 and I-90 corridor, from the Waterville
Plateau to northern Lincoln County to the Spokane/C'DA area, and
over the higher Palouse. However accumulations in this mixed area
should be limited or nothing. In addition to precipitation look
for breezy conditions again; right now values look below highlight
values but this will be monitored. /J. Cote'

Wednesday night through Sunday: The region will be transitioning 
into a cooler and showery weather pattern Wednesday night into
Thursday in the wake of a strong cold front passage Wednesday
evening. Precipitation chances will rapidly decrease in the lee of
the Cascades but isolated to scattered shower activity will
continue across the Cascade Crest, Idaho Panhandle, and far
eastern reaches of Washington. Snow levels will be lowering near
1000' late Wednesday night into Thursday indicating snow as the
dominate p-type for most valleys. It is now that time of year
where snow will have the potential to accumulate on roadways if it
was to fall overnight but is not expected to have much an impact
to travel during daylight hours. A few light showers will be
possible across the mountains Friday through Sunday but the
overall trend will be for a gradual warming trend aloft as a flat
ridge of high pressure attempts to become re-established. This
will increase stability around the region, starting across the
southwest then working northeast...leading to a decreasing threat
for precipitation. Forecast grids may not reflect this completely
yet as there were some rather big differences in the deterministic
and ensemble models how quick this will occur and 12z
deterministic guidance would suggest a much quicker drying trend
across the northeastern and eastern mountains than our forecast
would indicate. However, given the degree of wavering in the
models over the last 2-3 days, did not want to bite off on these
solutions quite yet. PoPs have been nudged downward region-wide,
especially for the Basin, but will wait for a bit more model
consistency before drying out the mountain zones completely.
Temperatures will be running below normal for March standards
Thursday and Friday then spring back closer to normal by the
weekend. /sb

&&

.AVIATION...
00Z TAFS: Showers and clouds ahead of wet frontal zone are overhead 
of Eastern Washington and North Idaho currently...the stable 
prolonged valley rainfall expected to start not too far from 00Z 
Monday near KEAT with a delay until about 3-4Z for Spokane and Coeur 
d' Alene aviation area. Ceilings associated with precipitation 
expected to be primarily MVFR. The back edge of the front sweeps 
through 8-12hrs later near 12-14Z Monday with a winds increasing and 
shifting to more from the southwest. May see some blowing dust 
appear tomorrow due to the increased wind. /Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        36  49  28  48  34  50 /  90  30  10   0  20  50 
Coeur d'Alene  37  49  28  46  32  49 / 100  50  10  10  20  60 
Pullman        35  46  29  47  34  49 / 100  60  10  10  10  50 
Lewiston       42  52  34  53  37  56 / 100  70  10   0  10  40 
Colville       34  56  27  52  32  53 /  80  10  10  10  20  50 
Sandpoint      34  47  27  44  30  46 /  90  60  10  10  30  50 
Kellogg        33  43  28  42  30  43 / 100  90  20  10  20  60 
Moses Lake     39  55  31  55  36  57 /  40   0   0   0  10  30 
Wenatchee      35  52  31  53  35  54 /  30   0   0   0  10  30 
Omak           33  57  27  52  31  54 /  20   0   0  10  10  30 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Weather Advisory from 11 PM this evening to 5 PM PDT 
     Monday for Central Panhandle Mountains-Lewis and Southern 
     Nez Perce Counties.

     Wind Advisory from 5 AM to 5 PM PDT Monday for Idaho Palouse.

WA...Wind Advisory from 5 AM to 5 PM PDT Monday for Lower Garfield 
     and Asotin Counties-Moses Lake Area-Upper Columbia Basin-
     Washington Palouse-Waterville Plateau-Wenatchee Area.

&&

$$