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000
FXUS66 KOTX 180930
AFDOTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
230 AM PDT Sat May 18 2013

.SYNOPSIS...
Scattered showers and isolated thunderstorms will develop again
this afternoon and evening. The greatest threat of thunder will
occur over the northeast corner of Washington and much of the
Idaho Panhandle. Precipitation chances will diminish a bit on
Sunday and by Monday most locations will be dry. This drying will
come to an abrupt end by Tuesday afternoon and into Wednesday as a
a very cool and wet upper level low parks itself over the Inland
Northwest. Steady, moderate precipitation will be possible
especially over northeast Washington and the northern Panhandle.

&&

.DISCUSSION...
Today through Sunday...Low pressure trof containing typical spring
somewhat unstable air-mass along with nuisance mesoscale shortwaves
rotating through and around it remains. The subtle change is that
the axis of the trof moves east and as a result higher pressure
approaches from the west and gets in closer proximity with time.
The result of such a scenario described above is continued clutter
of moderate to low pops the show a decreasing but not disappearing
trend into Sunday to account for not only surface based convection
in the afternoon and evening but also some minor elevated
convection during the overnight and early morning hours associated
with these nuisance small scale shortwaves. Precipitation amounts
can be best conveyed by describing this convection as hit and miss
showers and even more remote weak thunderstorms. With the eastward
migration of the trof axis height rises moving in from the west
suggest an ever so slight and not entirely homogeneous warming
trend in max temperature going into Sunday. /Pelatti

Sunday night through Monday night: Evening showers will taper off
over north Idaho within the vicinity of the upper trough axis.
Meanwhile a high pressure ridge will nose in over eastern
Washington. A few more instability showers or thunderstorms are
possible Monday afternoon and evening over the higher mountains of
the Idaho Panhandle as the weaken trough axis slowly exits the
region. Temperatures will be close to seasonal normals.

Tuesday through Thursday morning: The weather will be focused on the
presence of a deep upper level low. This Pacific low will swing
toward the WA coast Tuesday morning with light showers spread east
of the Cascades by Tuesday afternoon. This is slightly slower than
previous forecast and have indicated this in the forecast and kept
seasonal temperatures through Tuesday. Then as the upper low
center slowly moves inland, the impact will be in the form of a
deformation band of steady moderate precipitation which will shift
across eastern Washington and into north Idaho Tuesday night into
Wednesday. There are a few model differences on the track and
placement of this low center, which will effect the type and
intensity of the precipitation, but for the part did show the
low center meandering on either side of the Cascades. Areas
closer to the low center will encounter more convective
precipitation and lower snow levels down to near 4k ft. The
majority of the medium range models show the best chance of the
steady moderate precipitation from the deformation band will be
across southern BC and into the Canadian Rockies from Wednesday
night through Thursday morning. This will impact runoff and
mountain snow melt from the headwaters of several Inland Northwest
rivers, including the Okanogan, Kootenai, Kettle and Moyie.
Overall, anticipate cooler temperatures by Thursday with a threat
of near freezing conditions by early Thursday morning. /rfox

Thursday Afternoon through Friday Night: This time frame will be the
continuation of the previous period as the stubborn low pressure
system will continue to influence our weather pattern. With the
low in control we will see our temperatures fall to below normal
and slowly creep back towards normal by the end of the period.
Models are in decent agreement given the time frame in keeping the
low pivoting around the Pacific NW region...but the precise
location still remains uncertain given model discrepancies. Longer
range models have the center of the low scattered throughout the
region so above normal climo POPs was the trend in the extended
with the unsettled weather pattern in place. As we progress models
should align better giving a better idea as to where precip will
be more likely. As temps do start to reach more normal values
towards the weekend snow levels will be on the rise...which will
allow for greater runoff contribution to streams. Overall given
current model runs it appears that the brunt of the precip will
have already past but we will need to continue to watch rivers and
streams for any flooding concerns. Even given the far
extended...models are still reluctant to move this system out of
the region so it looks like we will remain in this unsettled pattern
for quite some time. /Fliehman

&&

.AVIATION...
06Z TAFS: A slow moving system beginning to push into southern WA
late this evening will continue to produce isolated to scattered
rain showers across the region tonight into tomorrow afternoon. Cigs
are expected to remain above 4 kft agl with vfr conditions through
Saturday afternoon. Winds are expected to pick up a bit out of the
west late Saturday afternoon at KEAT with gusts up to 30 mph
possible. /SVH



&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        65  45  66  46  70  49 /  40  20  20  10   0  10
Coeur d`Alene  64  44  64  43  69  45 /  40  30  30  20   0  10
Pullman        63  43  63  41  69  45 /  20  20  20  10   0  10
Lewiston       70  49  70  48  76  51 /  20  20  20  10   0  10
Colville       70  44  73  43  76  44 /  50  40  30  20  10  10
Sandpoint      64  43  64  42  69  43 /  40  40  40  30  10  10
Kellogg        60  44  60  45  67  46 /  40  30  40  40  10  10
Moses Lake     73  47  76  45  79  48 /  10  10  10   0   0  10
Wenatchee      68  48  72  49  76  51 /  10  10  10   0   0  10
Omak           71  43  74  42  77  46 /  40  20  10  10  10  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&

$$