Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Spokane Washington
254 am PDT Mon Mar 17 2014
a vigorous cold front will exit the region by late this morning.
This will result in a chance of rain and snow showers...cooler
temperatures and breezy to windy conditions today. Drier weather
returns Tuesday, but another threat of precipitation will be
possible by the middle of the week. Temperatures will remain near
seasonal norms through the week.
today through Tuesday...the cold front is slowly moving southeast
through the forecast area this morning....with warm stratiform
precipitation across the southeast zones and convective showers
across the northwest zones. The front is still expected to be
south and east of my forecast area near or just after 12z. This
will allow the flow to veer to the west-northwest and become
increasingly unstable through the day. This will support showers
and gusty winds. Late this afternoon through Tuesday high pressure
will begin to build in from the west. This will result in a
cool and mainly dry northerly flow tonight and dry conditions on
For the remainder of the day...the upper level low will move
across the eastern zones this morning and exit this afternoon.
This will help to destabilize the atmosphere. 500mb temps drop to
-30 to -32c with steepening lapse rates and some marginal mu cape.
With the flow veering to the west-northwest the best chances for
precipitation will shift to the central Panhandle...the Camas
Prairie and the Blue Mountains through the remainder of the day.
However showers will be possible back west to a line from about
Republic to Walla Walla through the morning. Satellite imagery
shows quite dry air moving in behind the cold front and that
should shut off convection from the northwest through the day.
Snow levels are still pretty high...4500-5000 feet as of 200 am
but these should come crashing down behind the front to below
3000 feet. As such the convective showers will likely contain
brief heavy rain or snow...and possibly graupel and/or small hail.
Accumulations should be little to nothing for all areas except
near the Cascade crest...central Panhandle mountains...the Blue
Mountains and the Camas Prairie. A Snow Advisory is in effect
through this afternoon and with the convective nature of the
precipitation in those area it is a good idea to keep that going.
Winds are on the increase this morning behind the front. Expect
breezy to windy conditions across most of the forecast area.
Sustained winds of 15 to 30 mph with gusts 35 mph will be common
through mid afternoon before decreasing. The Waterville
Plateau...Columbia Basin and the Palouse will see a little
stronger winds with 20 to 30 mph and gust 40 to 45 mph or higher.
A Wind Advisory was put out for those zones and that will be kept
in place as well.
Tonight and Tuesday the are will see a break in the weather as
high pressure builds. There will still be some low end pops for
the Panhandle mountains for isolated orographic showers but these
should be very hit and miss.
Temperatures will be near or on the cool side of normal both today
and Tuesday. /Tobin
Tuesday night through Thursday night...the next frontal system
will bring precipitation to the inland northwest during the mid
week period. Models have not quite settled in on the timing of the
warm front and the start of precip but are in better agreement on
the cold frontal passage. The GFS continues to bring the warm
front to the Cascades late Tuesday then spreads light precip
across the northern zones by early Wednesday morning. The European model (ecmwf)
lags the warm front and precip along the crest until Wednesday
morning. While the region is in the warm sector, precip will be in
the form of valley rain and mountain snow. Snow levels will be
above 3k feet in the Cascades Tuesday night but the passes will be
affected. The best chance of precip will be Wednesday into
Wednesday night as the cold front moves through the forecast area.
Winds will be on the increase and will become gusty with the
fropa. Behind the cold front, snow levels will fall to most valley
floors Thursday morning. There will be a chance for some light
snowfall accumulations but precip will become more showery in
nature and any snow that falls during the day Thursday will
probably not accumulate. The most favored areas for some snowfall
accumulations will be the central Panhandle of Idaho, Camas
Prairie, and possibly the higher elevations of the Idaho Palouse
where northwest upslope flow will enhance lift. Temperatures will
start out below seasonal normals and will continue the downward
trend with the passage of the cold front and the shift to
northwest flow aloft. /Kelch
Friday through Monday night: the flow pattern over the inland
northwest will begin to flatten out some by early in the weekend,
followed by a transient ridge to close out the forecast. The
exiting system on Friday will keep showers going over parts of the
Idaho Panhandle, with maybe a final weaker weather disturbance sneaking
through Friday night or Saturday. Precipitation amounts will
likely be light as very limited moisture will be available. A
ridge of high pressure will traverse the region to round out the
weekend into early the following week. This ridge is just ahead of
a potentially stronger system for periods just beyond this
forecast. Temperatures should hover a degree or so from where we
should be this time of year. TY
06z tafs: wet frontal zone working its way east through Washington
and north Idaho...aviation locations impacted with rainfall
with ceilings primarily MVFR. The back edge of the front sweeps
through near 12-14z Monday with a winds increasing and shifting to
more from the southwest. May see some blowing dust appear tomorrow
due to this increased wind. /Pelatti
Preliminary point temps/pops...
Spokane 49 29 47 34 50 30 / 50 20 0 20 60 50
Coeur D'Alene 48 29 45 32 48 30 / 50 20 10 30 70 70
Pullman 46 30 46 34 49 31 / 70 10 10 10 60 60
Lewiston 53 34 51 36 55 35 / 70 10 0 10 40 60
Colville 54 28 51 33 53 31 / 40 20 10 30 60 40
Sandpoint 46 28 43 31 45 30 / 60 20 10 30 60 70
Kellogg 42 27 41 30 43 29 / 70 20 10 30 70 80
Moses Lake 56 30 54 37 58 33 / 10 0 0 10 30 20
Wenatchee 52 30 52 35 55 32 / 10 0 0 10 40 20
Omak 56 26 53 32 56 30 / 10 10 10 10 40 20
Idaho...Winter Weather Advisory until 5 PM PDT this afternoon for
central Panhandle mountains-Lewis and southern Nez Perce
Wind Advisory until 5 PM PDT this afternoon for Idaho Palouse.
Washington...Wind Advisory until 5 PM PDT this afternoon for lower Garfield
and Asotin counties-Moses Lake area-upper Columbia Basin-
Washington Palouse-Waterville Plateau-Wenatchee area.