spokane wa: fxus66 kotx 081157 aaa

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fxus66 kotx 081157 aaa
afdotx
area forecast discussion
national weather service spokane wa
357 am pst mon feb 8 2010
.synopsis...tthe primary storm track for the first part of the
week will remain over the southern united states leaving the pacific
northwest in a mild and dry...but occasionally foggy...weather
pattern. a weak low pressure system will have the potential to bring
mountain snow and valley rain back to the northwest wednesday night
through friday.

.discussion...
today and tonight...satellite pictures tell the story though the
short term. a short wave disturbance is currently moving into the
ridge and getting sheared apart...meanwhile another deeper upper
level low is moving into the eastern pacific and will bring the
next shot of widespread moisture later in the the week.
for today the models are following the satellite loopers showing the
weak wave losing much of it's energy as it gets pulled apart as it
moves into the ridge that is in place. there is some mid and upper
level moisture...but the only lift will be provided by a period of
southerly flow into the higher terrain of the north cascades and
northern highlands. and even this will only provide marginal
potential for light rain and snow showers. only a few areas west
of the cascades have reported a trace so far tonight and would
expect eve less east of the cascades today. more challenging will
be what to do with fog/stratus over the inland northwest. no major
changes to the air mass are expected for today and tonight. some
increased mixing is possible with the passing wave. so...with
this in mind will keep some patchy fog in the forecast for the
spokane area and the northern mountain valleys...otherwise guidance
suggests mainly stratus across the region. both the nam and the gfs
area showing some drying in the boundary layer through the basin
and nosing north towards spokane after 18z and this seems
acceptable. the challenge then becomes what to do with temps.
thinking at the time is that clearing will be later in the day for
the basin and east slopes and thus slightly lower temperatures
than yesterday. across the eastern zones partial clearing will
bring a few degrees of warming and i tried to show that in the max
temperatures.
for tonight the ridge holds strong and firm and the next wave
again splits with the main energy diving south into northern
california. with plenty of boundary layer moisture in place
tonight looks to be a near repeat of sunday night with fog and
stratus reforming over the region soon after sunset. /tobin
tuesday and wednesday...strong high pressure over the region
will temporarily weaken as a shortwave tracks through the region.
this shortwave is evident via evening water vapor along 135w. as
we have seen throughout a majority of this winter...the wave will
become meridionally stretched with the core of its energy splitting
either south into california or north into southern bc. as per
evening satellite imagery...the split is underway with the two
most pronounced circulations and areas of darkening either digging
south toward 45n or north toward 55n. by the time the system
passes over the inland nw tuesday nt...there will be very little
left to the wave outside a narrow ribbon of vorticity yielding
very little impact except passing clouds and possibility for
sprinkles/flurries; especially if these flurries or hydrometeors
from aloft are able to seeder-feeder areas of stratus in place. by
anymeans...the chance for measurable pcpn is extremely small.
wednesday night through friday...the pattern will become
increasing wet and unsettled as a deep moisture fetch currently
streaming ahead of a trough over the dateline shifts eastward
toward the pac nw. there is strong agreement amongst the gfs and
ecmwf regarding the positioning of a 180kt jet along 40n which
will propel the trough and associated deep moisture fetch toward
the pac nw. additionally...there is small spread amongst the
operational and ensemble guidance...and it appears the gfs has
initialized the moisture fetch vs the amsu which measures near 1.50".
as the trough nears the coast wednesday nt...we will begin to see
the strongest downstream height rises take place further inland
closer to the spine of the continental divide. there's little
doubt that the shortwave energy pivoting around the offshore low
will continue to weaken and stretched meridionally while moving
onshore...however this process will take place much closer to the
coast...if not along...resulting in much stronger mid and low
level pressure gradients; especially associated with a pair of warm
fronts that will pivot through. the result is a prolonged period of
modest and moist s/sw flow...ie. moisture transport...with pwat's
across the region climbing near 0.70" (roughly 170% of normal). due
to the fact the the dynamics will remain weak as the energy
continues to split...the main forcing driving the pcpn will be
isentropic omega along the 290-305k surface which will generally
result in generally light pcpn for the valleys but become enhanced
along the mtns where the 15-25kt s/sw 85h flow will enhance
orographic omega. due to the warm nature of the subtropical air
mass... 85h temperatures will be climbing near +3 celsius along the
southern basin and 0 c north near the canadian
border...yielding snow levels roughly 5000 - 3000 feet.
saturday through tuesday...the pattern will change very little
after a brief break as the central pacific becomes renewed with
another deep trough and taps into subtropical moisture. midlevel
flow will generally remain sw so temperatures look to remain at or
above normal with the chance for pcpn arriving every 24 hours.
with some model disparities noted...have left the climo pops
intact for now. /sb

.aviation...
variable conditions will continue around kgeg...ksff and kcoe with
lcl fzfg reducing vis to below 1/4sm around kgeg. around the area
vsby are generally 5sm or better. expect conditons to deteriorate
between now and sunrise...before improving again this afternoon.
near kpuw...klws conditons mvfr at times...but mainly vfr. the
challenge will be kmwh and keat...light east winds will result in
variable conditons at kmwh...but result in stratus development
around keat...with conditions improving aft 00z as winds shift back
to west-northwest. /tobin

.preliminary point temps/pops...
spokane 36 29 43 29 43 32 / 0 0 0 0 10 30
coeur d'alene 43 29 42 29 42 31 / 0 0 0 0 10 30
pullman 39 30 43 30 43 32 / 0 0 0 0 10 20
lewiston 43 33 47 33 48 35 / 0 0 0 0 10 10
colville 46 27 41 26 42 30 / 0 0 0 10 20 40
sandpoint 43 28 40 28 40 30 / 0 0 0 0 20 30
kellogg 39 26 39 26 39 29 / 0 0 0 10 20 30
moses lake 43 32 47 30 48 32 / 0 0 0 0 0 20
wenatchee 44 32 42 31 44 31 / 0 0 10 0 0 20
omak 46 30 41 28 42 31 / 10 10 0 0 0 30

.otx watches/warnings/advisories...
id...none.
wa...none.

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