000
FXUS66 KOTX 162339
AFDOTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
439 PM PDT Thu May 16 2013

.SYNOPSIS...
A spring time progressive weather pattern will continue through
the weekend featuring seasonably mild conditions and occasional
weak storm systems bearing scattered showers and a few
thunderstorms. The next week will begin manly dry and mild...but
there is increasing confidence that a wet and cool period will
envelop the region by mid-week.

&&

.DISCUSSION...
Tonight through Friday...The forecast area is coming under the
influence of a deep upper level trough with it`s axis still off
the Pacific Coast this afternoon. In this pre-trough southerly
flow regime numerous relatively weak and amorphous spokes of
energy area transiting from south to north...each one capable of
exploiting a moist in-situ air mass into at least scattered
showers and an occasional stray thunderstorm. Last night featured
a more coherent wave in this flow leading to nocturnal
precipitation. Tonight models and satellite extrapolation suggest
the next coherent wave currently impacting Oregon will focus it`s
energy south of the forecast area. Thus...after afternoon diurnal
convection dies down this evening with the sunset...generally dry
and at least partially clearing conditions are expected. The moist
air mass will prevent temperatures from dropping out of the 40s at
most locations and there is a possibility of patchy morning fog in
low spots and river courses.

On Friday another and possibly more coherent wave will spread
across the region as the northern portion of the incoming trough
brushes by the forecast area. Model soundings indicate a couple
hundred joules/Kg of SB CAPE possible when morning and early
afternoon sunshine allows temperatures to approach 70 degrees
across much of the lower elevations. Thus on Friday expect a
somewhat broader threat of afternoon showers encompassing not only
the normal orographic influenced zones...but also out into the
basin...with a slightly better but still rather small chance of
thunderstorms. /Fugazzi

Friday night through Monday morning: A longwave trof will
continue to influence the weather over the Inland NW. The cool
temperatures aloft coupled with seasonal warming at the surface
will promote diurnally driven hit or miss showers each afternoon
with the northern and eastern mountains carrying the highest
threat for pcpn. Isolated thunderstorms will be possible but we
are not anticipated any strong to severe activity and only minimal
chances exist along the immediate Canadian Border. There will be a
few weak shortwaves swinging within the trof which will enhance
the precipitation threat at times...very similar to what occurred
Wednesday night/Thursday morning. Each will be capable of upwards
of a tenth of rainfall. The strongest of these waves arrives
during the day Saturday and we have expanded the threat for
showers into the Basin. Attm...we kept Wenatchee and Moses Lake
dry due to increasing northwesterly flow and moisture progs were
not overly impressive but this could be overly optimistic if the
wave is stronger then modeled. A broad upper-level low approaches
the region late Sunday into Monday morning from the north.
Shortwave ridging briefly ahead of this wave will bring some
midlevel warming and increasing stability so we adjusted PoPs
downward...especially near the Cascades and Columbia Basin. As for
temperatures, highs will be running near to slightly below
seasonal normals or 60`s and lower 70s`. Lows will be in the 40`s
to upper 30`s. /sb

Monday through Thursday...Cool and wet weather will prevail across
the Inland Northwest as an upper level low settles over the region.
Models are in general agreement with the synoptic pattern, but there
are some subtle differences in the exact track of the low pressure
center. This difference in track could lead to significant differences
in the amount of rain that falls and which areas receive the
heaviest amounts. While the last few runs of the GFS are rather
consistent, the 12Z run of the ECMWF has the system coming in a bit
slower now, which will cut down on the accumulated qpf. Even with
these differences, confidence is high that we will see an extended
period of cool and wet weather during the mid-week period. It just
remains to be seen as to just how wet it will be. Temperatures have
been trended cooler, especially on Wednesday when all models have
the upper low pretty much overhead. Snow levels have also been
lowered, to about 4500 ft by Wednesday. This will keep some of the
precip tied up as snow in the higher mountains. Area streams and
rivers will be on the rise again, with bankfull conditions possible
again by midweek. /Kelch

&&

.AVIATION...
00Z TAFS: A moist and weakly unstable air mass will reside over
the region through the TAF period. There is little in the way of
upper level dynamic support...thus clouds and showers will be
mainly driven by orographic influences and daytime heating. this
evening scattered mainly mountain showers will dissipate after
02Z-03Z followed by a quiet night with clearing skies. Patchy fog
is possible from 12Z to 18Z in northern river valleys. Scattered
afternoon showers will return on Friday with a small chance of
thunderstorms mainly over mountains. A weak disturbance aloft on
Friday may allow scattered showers to form over the Columbia Basin
after 20Z...but ceilings will likely remain VFR at all TAF sites.
/MJF

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        47  69  48  65  44  65 /  20  20  20  40  20  20
Coeur d`Alene  44  68  47  64  43  63 /  20  30  20  40  30  30
Pullman        44  67  47  63  41  62 /  10  30  20  20  20  10
Lewiston       50  73  52  70  48  68 /  10  20  20  20  20  20
Colville       42  74  47  70  44  72 /  30  30  30  50  50  20
Sandpoint      41  68  46  65  43  63 /  20  40  30  40  40  30
Kellogg        45  65  48  61  44  58 /  20  40  30  40  30  30
Moses Lake     48  78  51  72  47  75 /  10  10  10  10  10  10
Wenatchee      49  74  52  67  48  70 /  20  20  10  10  10  10
Omak           44  74  47  71  43  72 /  20  20  20  40  30  10

&&

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

$$