Area forecast discussion
National Weather Service Spokane Washington
503 am PDT Fri may 24 2013
Synopsis...
cool and showery weather will continue through Saturday, then a
subtle warming and drying trend is anticipated by Monday as the
upper-level low moves out of the area. The break will be
short lived as another cool, showery pattern returns around the
middle of next week.
&&
Discussion...
today and tonight: an upper low and the shortwave pivoting around
it will provide a good chance of showers for the inland northwest,
especially this afternoon. The low and its associated shortwave
disturbance were tracking through Portland, Oregon this morning.
It was helping to generate the swath of precipitation along the
west and central Washington/or border and it was starting to reach toward
the Chelan-Grant-Adams-Garfield County borders.
Satellite/radar extrapolation and models are in good agreement in
tracking the low into the lower Columbia Basin later this morning,
before it pivots northeast through the Blue Mountains through
central Panhandle of Idaho this afternoon and early evening. This
will allow the swath of precipitation to continue it expansion
east and northeast. Coverage increases through the afternoon, with
the added threat of thunderstorms, working with the increased
convective instability with daytime heating. On average models
depict 100-200 j/kg of cape this afternoon and early evening,
before conditions begin to stabilize with the loss of daytime
heating.
The lack of strong lift and/or 0-6km shear suggests that any
thunderstorms that develop should not be too organized. The
exception lays around the Blue Mountains, Camas Prairie into the
clearwaters where 30-60kts of shear are indicated. A few stronger
storms are possible here in the afternoon and evening. The
limiting factor may be cloud cover which could inhibit the
atmosphere from reaching it full convective potential.
After dark the threat of precipitation wanes, but doesn't entirely
end and skies do not appear to clear completely as models string a
secondary weaker vorticity lobe in from the west. The primary
shower threat linger in the Cascades and northeastern mountains.
/J. Cote'
Saturday through Thursday...model agreement exists as far as
maintaining an overall troughy flow regime over the region through
the extended period. There are significant differences in the
depiction of minor waves and disturbances transient through this
overall regime. The GFS is most consistent with the timing of the
only major feature/wave to impact the region...a beefy cold front
with plenty of precipitation potential way out on next Wednesday
or so.
So...for most of the forecast period a generally slightly cooler
than average regime featuring general small to medium chances for
afternoon and evening showers concentrated especially over the
mountains ringing the basin is called for. There will be no major
storm systems to impact the region until the aforementioned cold
front toward the middle of the new work week. Thus while the
Holiday weekend will feature a threat of showers from time to
time...there does not appear to be any day that will be
particularly wet...or particularly dry either. The smallest chance
for showers will be in the Cascades Lee zones and deep basin
with the highest chance in the mountains north and east of the
basin. The broad brush approach of daily small to moderate shower
chances may come across as somewhat weaselly...but is well justified
in this regime. /Fugazzi
&&
Aviation...
12z tafs: some patchy fog will impact the northeast valleys this
morning, mainly before 16z. However it should remain largely away
from taf sites. Low pressure and energy moving around it will help
push a swath of precipitation from Oregon into southern Washington
and the central Panhandle this morning. It is expected to weaken
as it pushes north, but the still approaching upper disturbance
and daytime heating will help develop other scattered showers this
afternoon and evening, with a chance of thunderstorms. Expect
primarily VFR conditions but local MVFR cigs are possible in
heavier showers. The threat of showers will wane after dark.
/J. Cote'
&&
Preliminary point temps/pops...
Spokane 57 42 63 44 67 47 / 60 40 20 10 10 10
Coeur D'Alene 57 42 63 42 66 43 / 60 50 20 10 20 20
Pullman 55 40 63 42 66 44 / 60 30 20 10 40 20
Lewiston 61 45 70 48 73 50 / 60 30 20 10 30 30
Colville 63 42 67 42 72 43 / 60 60 40 30 20 20
Sandpoint 58 41 62 39 66 41 / 60 60 30 20 30 30
Kellogg 54 42 60 43 64 46 / 70 60 40 30 30 30
Moses Lake 64 47 72 47 75 49 / 50 20 10 0 0 10
Wenatchee 63 49 68 48 72 51 / 40 20 10 0 10 10
Omak 63 42 68 42 73 44 / 40 40 20 20 10 10
&&
Otx watches/warnings/advisories...
Idaho...none.
Washington...none.
&&
$$
