Scientific Forecaster Discussion

Return to Local Conditions & Forecast
Area forecast discussion 
National Weather Service Spokane Washington
443 am PDT Monday Apr 21 2014

Synopsis...
increasing clouds can be expected today with occasional sprinkles
through the day. Although we will see plenty of cloud cover
today, temperatures will be mild for mid April. A cool and showery
unsettled weather pattern returns Monday night and will linger
through much of the work week before showing signs of exiting for
the weekend.



&&

Discussion...
today: the flow pattern will become increasingly more southerly
today, which will draw up more moist and mild air into the region.
This will be in response to an approaching trough of lower
pressure in the eastern Pacific. The upper level trough will
continue to dig with time today as a moderately strong jet streak
of 160 kts pushes down on the backside of the trough. This will
Orient the jet on the westerly side of the trough more
meridionally this afternoon. With the jet oriented more north-
south instead of the west-east, the cold front will likely take a
slower progression across the region. The cold front is already
beginning to shift west of 130w, but is not expected to push east
of the Cascades until tonight.

We will see increasing mid level moisture today. This will result
in thickening cloud cover with an increasing chance for some light
showers mainly across the Cascades and in the northern mtns. There
is enough drier air near the surface across the basin that mainly
virga showers or some sprinkles is expected today ahead of the
front. Although there will be plenty of cloud cover, temps are
expected to warm up nicely over the eastern half of the forecast
area compared to yesterday and will feel quite mild.

Tonight into tuesday: precip chances will increase markedly from
west to east overnight into Tuesday as the front pushes through.
Good upper level dynamics and forcing along the front will result
in rain showers over most areas. Rain showers will push as far
east as the Idaho border tonight into early Tuesday morning. Then
pick up in intensity across the eastern third of the Washington and into
the Idaho Panhandle through Tuesday morning into the afternoon.
Pressure gradients will tighten behind the front with winds
increasing from the west through the afternoon. Expect sustained
winds of 20-25 mph with gusts up to 35 mph. Rain showers and
cloud cover on Tuesday will hold down our temperatures through the
afternoon hours. Temperatures are expected to be 10-20 degrees
cooler compared to Monday with highs in the low to mid 50s for
most valley locations. /Svh

Tue nt through Sat: as the cold upper trough moves NE into wrn
Montana Wed morning, we'll slowly transition from a highly
convective regime to a more stable pattern under short-wave
ridging. The valleys of the north Idaho Panhandle and NE WA Wed
morning are still under a threat of snow showers. But most likely
any significant accumulations will be limited to the mountains
above about 3k ft. The wrn end of the trowal structure that wraps
around the upper low nearly stalls across the British Columbia border with
Idaho even through Wed. Lingering rain/snow is the result for the
aforementioned valleys and mtns. Beginning Wed nt, a more
widespread stratiform pcpn event will keep high chances of pcpn
in the fcst for most zones... especially thurs as deep isentropic
ascent over an advancing warm front moves NE across the region.
Due to the shearing/splitting of the accompanying upper trough in
response to a jet speed Max digging toward northern California
thurs nt, the cold front will stall directly across ern WA and north
Idaho. This slowly weakening boundary won't begin to move out of
the area until Sat, leading to a very cool and showery Fri and
Sat. There is also a significant vort Max that moves north into
ern WA Fri as well, enhancing the prolonged pcpn threat. Bz

Sunday and monday: an exiting trough will signal somewhat of a
drying trend for the early week. However, there is some indication
that yet another moist weather system will affect the region soon
after. While precipitation were nudged downward, did not want to
bring them too far down given this possibility. Temperatures on
Sunday will be slightly below normal, while warming toward normal
on Monday. TY

&&

Aviation...
12z tafs: the region will come under an increasingly moist
southerly flow pattern out ahead of a cold front pushing into
western Washington. The main aviation impact for this afternoon into this
evening will be thickening mid to high level cloud cover. Any
precip that falls will be very light. The cold front in western Washington
will begin to move into the Cascades this evening. This will
increase chances for rain showers at keat with MVFR cigs possible
after 06z. /Svh



&&

Preliminary point temps/pops...
Spokane 64 44 51 35 50 36 / 10 40 80 30 50 10
Coeur D'Alene 68 44 51 34 49 35 / 10 30 90 50 60 20
Pullman 68 45 49 34 48 37 / 10 20 90 40 50 20
Lewiston 74 50 55 39 54 41 / 0 20 80 30 40 20
Colville 65 40 54 33 56 35 / 20 50 90 40 50 10
Sandpoint 66 42 52 33 49 36 / 20 20 90 80 70 30
Kellogg 66 42 51 33 48 36 / 10 10 100 80 70 30
Moses Lake 69 47 57 37 59 39 / 10 60 60 20 20 20
Wenatchee 67 48 55 41 57 42 / 10 70 60 10 20 20
Omak 66 43 54 34 57 36 / 20 60 70 20 20 10

&&

Otx watches/warnings/advisories...
Idaho...none.
Washington...none.
&&

$$