Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 172335

Area Forecast Discussion
National Weather Service Spokane WA
434 PM PDT THU APR 17 2014

A strong and wet Pacific weather system will result in widespread
rain tonight, with windy conditions late tonight into Friday. A
weaker front will bring mainly windy conditions Saturday afternoon
and night with some showers across the north. Easter Sunday
should be mild and mainly dry. Active and occasionally showery
conditions will continue through the new work week.


Tonight and Friday...The forecast area is under the influence of a
moist Pacific feed which is enhancing into rain over much of the
area compliments of a warm front stretching west to east across
eastern Washington. This will continue through much of the
evening...culminating in a round of heavier showers along and
immediately behind a cold occlusion which is clearly visible on
satellite approaching the coast this afternoon. This front will
probably be sufficient to trigger showers even in the Cascades lee
this area that has thus far escaped any appreciable
warm frontal precipitation. Model consensus rainfall amounts tonight
will range from 1/4 inch over the eastern over 1/2 inch
in the Panhandle and northeast mountains and a tenth or so in the
deep basin. Snow levels will remain in the 4000 to 5000 foot
range with minor accumulations on the higher peaks.

After the occluded front passage...this evening in the west and
overnight in the east...precipitation will quickly taper off and
the weather issue will shift to winds. Strong cool and dry air
advection will fill the basin with a new air mass. This air
movement will manifest itself in windy and gusty conditions off
the Cascades and across the basin through Friday...with lingering
orographic showers over the Northeast mountains and Idaho
Panhandle. The gradient strength regardless of which model is used
will not support any wind advisory criteria...and gust potential
in the well mixed air mass will support gusts to 30 to 40
mph...windy but not bad enough to warrant any highlights. The
winds will promote adiabatic warming on Friday to only a few
degrees below average despite the cold advective scenario.
Convective parameters suggest only a minimal threat of isolated
and brief thunderstorms over the northeast during the afternoon.

Friday night through Sunday night: Anticipate clearing skies and
decreasing winds Friday night as one storm system departs the
east. Many valley temperatures will dip near the freezing mark and
patchy river fog is a strong possibility throughout the sheltered
northern valleys. Another potent midlevel shortwave will approach
the WA coast Saturday morning then swing through the Inland NW
late afternoon and into the night. This will usher another strong
cold front through the region. The available moisture with this
system will be nearly half of what is being transported inland
today (PWATS of 0.40" vs 0.80"). In addition, the system will pass
through rather quickly. This will mean little no rainfall for the
Basin and generally under a tenth for the surrounding
valleys/mountains. The Cascade Crest will receive closer to an
quarter of an inch. Snow levels will rise between 4000-5000` with
the main precipitation threat and given the nocturnal passage, a
few light snow showers could impact area mountain passes.

Gusty winds are expected to accompany the system. Cross CWA pressure
gradients become tightly packed but generally remain around 10mb
or less. This should drive sustained winds of 10 to 20 mph. The
trickier part of the forecast will be gusts. The cold front
presses through Ern WA and Nrn ID between 00-04z with sharp
cooling at 850mb from around 8C to 0C. Forecast soundings indicate
a well mixed profile from the surface to 750mb between 00-03z. If
this holds true, we should see wind gusts between 20-30 mph ahead
of the cold front and increasing to 35-45 mph along and immediate
behind the cold front. We have began to increase wind gusts with
the afternoon forecast package and will likely continue this trend
with the overnight package if model trends remain consistent.

The storm system will be out of the region early Sunday morning
and high pressure will begin to build in Sunday and Sunday night.
A weak warm front will lift through the area spreading mid and
high level clouds but most locations will be dry with seasonal
temperatures. There is a slim chance for a few light showers
across the northern mountains but the light nature of this
activity will have very little impact on travel or recreation. /sb

Monday through Thursday: Throughout this time frame the region
will remain in a pretty active pattern as a well defined trough
influences our weather pattern. Starting Monday we will be on the
backside of a ridge of high pressure giving us one final day of
pleasant warm conditions due to the associated warm SW flow.
Throughout Monday we will notice increasing clouds as moisture
from the incoming system begins to influence our weather pattern.
Increased moisture will enter the region re-saturating the
atmospheric column Monday into Monday Night. Given the need to
re-saturate, the best chances initially for precip will be in the
higher elevations.

For Monday Night, the precip associated with the trough will make
it to the Cascades before spreading east of the crest early
Tuesday and through the remainder of the day. With the trough axis
being directly off the WA coast, it will allow for an abundance of
Pacific moisture to advect into our area and with PWATs near .7",
this will lead to a good chance of widespread rain. As the trough
center moves overhead, we will then have cooler air aloft
allowing for lower snow levels and a much more destabilized
atmosphere. With associated weak waves within the closed low
trough, this will promote scattered weak convective showers on
Wednesday. The coverage of these showers will have to be better
refined in the future, but is something to note. Snow levels is
also something to watch as the system brings in quite a bit of
cool air aloft.

Thursday will see a brief drying trend before the next system sets
up for the end of the work week. Overall we can expect to see an
abundance of clouds throughout the period as enough moisture will
remain in place for a higher amount of cover. Aside from the 60s
on Monday, the remainder of the work week will feature below
normal temps in the 50s for most valleys. Winds will also remain
breezy throughout the period, but should not warrant any sort of
highlights. /Fliehman

00Z TAFS: A cold front running along the Pacific Coast at 00z will
move through the region and pass through KEAT around 03Z-04Z and
the eastern TAF sites between 06Z and 12Z Friday. Ahead of this
front a moist feed off the Pacific will promote widespread -RA
with mostly MVFR ceilings...with some brief periods of IFR
ceilings especially at the KPUW and KGEG TAF sites. After the
FROPA the air mass will dry quickly with VFR conditions at all TAF
sites...but gusty west/southwest winds developing Friday morning
and persisting through 00Z Saturday./MJF


Spokane        38  55  33  64  37  57 / 100  30   0   0  20  10
Coeur d`Alene  38  54  31  63  37  56 / 100  60   0   0  20  10
Pullman        38  52  34  66  38  56 / 100  20   0   0  20   0
Lewiston       43  60  36  72  41  63 / 100  10   0   0  10   0
Colville       38  60  31  67  34  62 / 100  50   0  10  20  10
Sandpoint      39  54  30  62  36  55 / 100  60   0   0  30  20
Kellogg        37  50  30  63  37  55 / 100  60   0   0  20  20
Moses Lake     40  62  33  69  40  65 /  50  10   0  10  10   0
Wenatchee      40  60  38  65  40  64 /  60   0   0  10  10  10
Omak           37  61  31  66  34  64 /  70  10   0  10  20  10



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