Area Forecast Discussion
Issued by NWS Spokane, WA
FXUS66 KOTX 251154
Area Forecast Discussion
National Weather Service Spokane WA
454 AM PDT Sat Mar 25 2017
Mainly mountain showers and breezy winds can be expected for
today. Sunday will start out dry, but the chances for
precipitation will increase from the west late Sunday afternoon
and Sunday night. Afternoon showers will be possible through next
week, with several more rounds of rain and mountain snow
Today and Tonight...Satellite imagery gives a good idea on what to
expect today. An upper level trough will move across the region
and eject east into Montana by late this afternoon. A
conditionally unstable atmosphere will be over the region. 500Mb
temps will be -28C and lapse rates 6-7 C/km. Not much in the way
of a kicker except afternoon heating. Another thing the satellite
loop shows is a mass of quite dry air moving with the trough.
Showers will be likely in our normally favored orographic areas,
it will be much tougher to get showers initiated out side of the
Cascades, the Blue mountains and the Panhandle mountains.
Precipitation will be as valley rain and graupel and mountain
snow. Temperatures will be on the cool side of seasonal norms.
Southwest winds will be on the increase slightly through the
afternoon with gusts 20 to 25 mph.
High pressure will move into the region late this afternoon and
move slowly across the forecast area tonight and early Sunday.
This will bring a break in the active weather. Lighter winds and
mostly clear skies will result in localized stratus/fog
development, likely near water sources.
Sunday afternoon and Sunday night...The next weather system will
quickly move into the region Sunday afternoon. A warm front will
drag increasing Pacific moisture back into the region by late
Sunday afternoon and track across the forecast area Sunday night.
Moisture again increases to around 200 percent of normal and will
result in another period of widespread light to moderate
precipitation. The accompanying cold front is expected to follow
after 06z Sunday night or so and will result in drying from the
west Monday morning.
Precipitation amounts and impacts: Precipitation amounts from
around a tenth of an inch in the Basin to between a quarter and a
half inch for the higher terrain of the Panhandle mountains will
be possible. Snow accumulations of 3-6 inches will be possible for
the mountains, with locally higher amounts near the Cascade crest.
High water levels on small rivers and streams will continue.
Localized field flooding will also remain problematic. Tobin
Monday and Tuesday: The trough axis pushes through the region
Monday. Chance of precip will decrease in the morning, but as
things become unstable in the afternoon, the chance of showers and
isolated thunderstorms will increase. 500mb temps range from -28
to -31C in the aftn. The 00Z GFS is showing less instability than
earlier runs, but the 00Z NAM is similar to its previous run and
is showing good instability in the afternoon and early evening
hours. Currently have thunder across Spokane and Whitman counties
and eastward. If the NAM continues its trend, may have to extend
that further west into the Columbia Basin during the afternoon
hours. The chance of showers will decrease through the overnight
hours. A shortwave flat ridge moves in on Tuesday. Precipitable
water values remain high...about a half inch or more. There should
be enough orographic flow for showers to develop once again, with
the best chance in the mountains.
Wednesday through Saturday: The general pattern between the
models is in pretty good agreement. A warm front will move in
Wednesday followed by an upper level trough and cold front Wed
night or Thursday. Then a ridge builds in by Friday and flattens
Saturday as the next weather system approaches the area from the
northwest. The specifics between the models are different such as
timing and strength. Kept chance of showers in the forecast
through Thursday then start to dry things out Thur night through
Friday night as the ridge builds in.
Daytime temps will be around or slightly below average while
overnight lows will be around or slightly above average. Or for
the valleys...high temps in the upper 40s and 50s with lows in the
12Z TAFs:An unstable air mass will support isolated showers at
times for the eastern TAF sites with scattered showers near the
Cascades and Panhandle mountains through sunset. Cigs/vsby will
remain VFR through the forecast period...however with heavier
showers conditions may drop to MVFR/VFR briefly. Southwest winds
will be on the increase through the morning with gusts 15-20kts
through sunset. High pressure building into the region tonight
will result in lighter winds and clearing skies. Stratus/fog
development will be possible for the northern valleys and along
water sources and this may affect KSFF/KGEG 06-12z. Tobin
.PRELIMINARY POINT TEMPS/POPS...
Spokane 49 33 48 38 51 37 / 10 10 30 70 70 30
Coeur d`Alene 47 31 48 36 48 35 / 20 10 20 80 70 40
Pullman 47 34 49 38 49 36 / 20 10 40 70 80 30
Lewiston 56 36 53 41 55 38 / 40 0 20 80 70 20
Colville 48 29 47 36 49 35 / 10 10 20 70 60 10
Sandpoint 46 29 47 33 46 33 / 50 20 10 70 70 40
Kellogg 43 31 45 34 44 34 / 50 20 20 90 70 50
Moses Lake 56 32 52 38 58 40 / 0 0 50 70 20 10
Wenatchee 51 31 47 35 53 37 / 0 0 70 80 20 10
Omak 50 30 47 35 53 37 / 10 0 70 80 20 10