Area forecast discussion
National Weather Service Spokane Washington
431 am PDT Wed Jun 19 2013
Synopsis...
a band of moderate rain will continue over the Idaho Panhandle
and extreme eastern Washington today. More rain is expected on
Thursday, mainly across the northern and eastern mountains. The
rain will gradually subside on Friday with a drying and warming
trend expected this weekend. Wetter and cooler weather will return
early next week.
&&
Discussion...
today and tonight...the low pressure center remains off the
Washington coast this morning but is making some progress to the
east. The upper low is sending a swath of Pacific moisture into the
inland northwest on southerly flow. A north-south oriented band of
precipitation has been dumping steady rain on southeast Washington and the
Idaho Panhandle overnight and will continue today and into tonight.
An area of heavier precip is moving north across the Panhandle as of
2 am and will push into the northern reaches of the Panhandle by
sunrise. We have seen radar estimates of up to 0.4 inches an hour in
the vicinity of the Lewis-Clark Valley early this morning from the
area that is moving north toward Interstate 90. For now the rain has
not been consistently heavy, but has been coming in waves with
lighter rain at times. There have been a few lightning strikes near
our borders and the best instability is forecast to remain to our
south and east so I do not expect much convection from this system.
Most of the rain will be more stratiform in nature. The NAM
continues to be the outlier in bringing about twice the amount of
rainfall to the Idaho Panhandle today and so far this is not
verifying. The GFS brings from a third to a half inch over each 6
hour period today. This will bring rises to area streams and rivers
but they should be able to handle this amount.
As the low slowly makes its way inland tonight, the band of
precipitation will pivot, bringing the heavier rain into the
northern zones. There is some model disagreement on how far west
into eastern Washington the band will spread. The NAM brings an area of
heavier qpf into the Spokane area while the GFS keeps it along the
periphery of the forecast area with the bulk of the qpf in Idaho
then wrapping northwest across extreme northeast Washington. For now the qpf
forecast runs the middle of the Road. The 24 hours total qpf from 12z
Wed thru 12z Thu ranges from a tenth in the Lower Basin, around a
half inch for the eastern basin and east slopes of the Cascades,
around three quarters to an inch for the valleys of eastern Washington. The
valleys of north Idaho and NE Washington could see around 1.25 inches with
an inch and a half to 2 inches for the northern and eastern
mountains. /Kelch
Thursday through Friday...models continue to display close
agreement and consistency over previous runs in depicting the very
slow progression of the upper low through and finally to the east
of the forecast area. Wrap around moisture curling around the
north flank of the upper low will be the main fuel source for
further precipitation during this period...with increasingly
west/northwest flow in the mid levels promoting a more orographic
character to the continuing showers. On Thursday at least this
trend will be only weakly discernible with pretty much the entire
forecast area still subject to frequent showers...but by Thursday
evening and Friday the deep basin and Cascades Lee zones should
notice a slackening off of showers with the lion's share of
continuing showers focused over the zones north and east of the
basin.
Given the copious rainfall amounts expected over the next few
days subsequent shifts will need to monitor closely for small
stream flood issues. Snow levels are not expected to drop below
6000 to 7000 feet during this evolution...but high temperatures
win the populated low lands will remain far below normal mainly
due to heavy low level...dense cloud cover moisture and
precipitation presence.
Saturday and Saturday night...this period appears to be the driest
period of the extended forecast. Just in time for the weekend the
offending upper low will be skulking eastward and menacing Montana
while a short wave ridge pops up over the region. Both the GFS and
old ec models are coming in line with this solution which leads to
increasing confidence of a dry break on Saturday with some sun and
high temperatures approaching or even breaking 70 degrees at many
locations.
Sunday through Tuesday...latest GFS (latest European model (ecmwf) unavailable
tonight) returns the region to a progressive and moist southwest
flow punctuated by a few disturbances...any of which could trigger
showers and thunderstorms. The previous ec model also reflects
this regime. Thus after a needed break in the weather on
Saturday...maybe lasting through much of Sunday...expect a return
to unsettled conditions with temperatures remaining somewhat below
normal. /Fugazzi
&&
Aviation...
12z tafs: a band of moderate rain will persist over the Idaho
Panhandle today. This will bring MVFR/IFR conditions to most of the
tafs (aside from keat and kmwh). Kcoe will likely be IFR all day
long. Ksff will also see some near-IFR conditions. Tougher call at
kgeg which will be on the western edge of the rain band. Kpuw will
likely have an IFR cig in the morning but improve a bit in the
afternoon.
To the west, kmwh and keat will just have VFR clouds. Gusty west
winds will develop in the late afternoon at keat in response to a
strong pressure gradient. Gusty winds will diminish after 06z
Thursday. /Ek
&&
Preliminary point temps/pops...
Spokane 56 46 55 45 61 46 / 100 80 80 60 50 20
Coeur D'Alene 54 46 54 43 60 45 / 100 100 90 70 60 40
Pullman 54 45 56 42 60 43 / 100 80 60 50 50 50
Lewiston 59 49 64 46 67 50 / 100 80 60 30 50 40
Colville 62 51 57 47 67 45 / 100 100 100 90 50 20
Sandpoint 57 47 53 44 60 43 / 100 100 100 90 60 40
Kellogg 51 44 51 41 57 44 / 100 100 100 70 70 60
Moses Lake 68 52 65 49 69 50 / 40 50 50 30 30 10
Wenatchee 66 52 64 52 68 54 / 40 60 60 40 30 10
Omak 66 51 64 50 69 49 / 70 80 80 60 50 10
&&
Otx watches/warnings/advisories...
Idaho...none.
Washington...none.
&&
$$
