Winter Weather in Washington, February 15 to 16, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
946 PST Sat Feb 15 2014

.SYNOPSIS...
A series of storm systems will track across the region through
the middle of next week. Each delivers periods of rain and mainly
mountain snow. However there is the potential for snow in the
northern valleys during the night and early morning hours through
next Tuesday, then into all valleys by Wednesday. Some moderate
precipitation amounts are possible, along with breezy conditions.

&&

.DISCUSSION...
Today and tonight...Another day...another storm. And the parade
of storms continues. Unlike the past several though this one will
be a little different. The big change is this system will be
accompanied by a well defined warm front which will deliver
precipitation to many locations during the warmest part of the
day. The past few delivered their precipitation beginning during
the nighttime hours. So why will this make a difference? It should
make it much tougher to deliver accumulating snows to the valley
locations save one location and even there its a little fuzzy. But
more on that later. First off it looks like the morning will begin
quietly enough as the latest atmospheric river position was
pointed toward the southern Oregon Coast as of 2am. The
positioning of the river will gradually shift northward and
eastward through the day in response to very deep upper level
trough...poised just inside of 140w as of 2am. Models in good
agreement that this will push a rather strong warm front into the
southern quarter of Washington by late morning and to the Canadian
border before late afternoon. Isentropic ascent and moisture
transport associated with this front is very strong and suggests
just about all locations will receive precipitation. Snow levels
are expected to soar for all locations...suggesting that valley
snow will not be an issue with this system. Again with the bulk of
the frontal precipitation coinciding with the warmest time of day
that gives us even more confidence to downplay valley
accumulations. Even if snow does fall in the valleys it will
likely have to do battle with warm road temperatures. There is one
exception to this and that is the lee of the Cascades. Models have
consistently depicted some decent cold air damming there in
response to the low/mid level flow turning to the east-southeast.
Just how low this will keep snow level is the big question.
Current wet bulb temperatures in the north Cascades are below
freezing...generally ranging from 27-29 degrees...which is
sufficient for snow provided temperatures don't climb. But they
should climb...at least a little during the day. We suspect they
will remain below freezing...but not by much. Above the valley
floors snow will be no problem...and it could be plentiful. We are
forecasting precipitation totals of ranging from 0.50-1.00 inches
in that area which depending on snow ratios should translate to
heavy snow. Since the heaviest will fall over the mountains...and
not where people generally live...we will issue a winter weather
advisory for snow...rather than a heavy snow warning.
Elsewhere...locally heavy precipitation is expected especially
over the Idaho Panhandle with precipitation totals will fall just
a tad under what's expected in the Cascades. However unlike the
Cascades...snow levels will skyrocket. Some of the model solutions
take snow levels as high 6500 feet over the central Panhandle and
up to 3500-4000 ft over the northeast Washington Mountains and
north Idaho by late afternoon. While snow will initially be
possible in the northern valleys...it shouldn't amount to much.
Over the remainder of the forecast area we are looking for
precipitation amounts ranging from .20-.50 inches...which could
exacerbate any flooding issues as the ground remains frozen in
many locations. The high snow levels will also lead to increased
snow melt.

By early evening drier air begins to cross into southern Washington
as the dry slot moves in. This will be followed by the cold front
which is expected to pass through the Cascades later in the
evening. This will quickly lower snow levels...as well as end the
threat of precipitation across much of the Basin and eastern
Washington. Upslope flow will allow post-frontal showers to
continue at the crest and over the Panhandle but by that time the
atmospheric moisture content plummets.

Once again much of the region will experience a rather mild
day...with increasing winds...especially late in the day as the
dry slot moves in followed by the cold front. Its possible we
could near wind advisory speeds once again the foothills of the
Blues during the late afternoon/early evening hours...and across
much of the Basin during the overnight hours after the passage of
the cold front. But expect most of the wind gusts to range from 35
to 45 mph...a little too weak for wind headlines. fx

Sunday through Wednesday...Progressive flow pattern with the jet
stream in close proximity passing low pressure systems with
efficient moisture taps continues through this time interval.
With this continued dynamic scenario in mind forecast low
temperatures remain on what would be considered the warm side of
normal for this time of year given the high likelihood of clouds,
mixing, and warm air advection at various times inhibiting
overnight radiational cooling mechanisms. Daytime highs near
normal given similar reasoning. Significant low pressure systems
of note include a wet system sagging slowly through Sunday until
its slow exit to the east and brief shortwave ridging Tuesday
morning, key word is brief because by Tuesday afternoon another
low pressure system is moving on through and as it exits to the
south and east Tuesday night into Wednesday there will be a time
that the jet stream is far enough into Oregon and Idaho that
Eastern Washington and Northern Idaho will be influenced by a cold
conditionally unstable air-mass conducive to cooler temperatures
and snow shower activity with models hinting at small scale
disturbances having enough kick to initiate convective snow
showers, in addition snow levels in such an air-mass will go back
down to most valley floors regardless of surface temperatures as
the air-mass aloft is such a cold and unstable one. /Pelatti

Wednesday Night through Saturday Night: Throughout this time frame
we will transition from a very mild and active pattern to a cooler
and calmer one moving into the second half of the week.
Wednesday Night we will be on the backside of the cold front
bringing a change to the flow pattern switching to a cooler
northwest pattern. Jetstream still looks to be pumping enough
Pacific moisture into the area to promote topographically induced
snow whereas the valley chances will diminish slightly. Thursday
will bring our final note worthy system into the region with a
upper level low passing along the southern BC border accompanied
by a surface low looking to pass directly over WA. This will
promote a good chance for snow over the majority of the region as
little shadowing should be noted with the weaker winds throughout
the column. With the surface low passing over the region, this will
help to increase the chances for precipitation due to increased
instability. Models have not been great in consistency as to how
this system will play out, but it will definitely be something to
keep an eye on as it will potentially bring snow to both mountains
and valleys. Winds with the system will increase, but currently look
to not cause any problems.

Behind the Thursday system we will enter a period of cold
northerly flow that will limit the amount of moisture making it
into the Inland NW while dropping our temperatures well below
seasonal normals. Even with moisture low, with us being on the the
cold side of the jet our temps through the column will become
quite cold bringing increased instability. This scenario would
allow for weak convective snow showers rather than widespread
snow. With the pattern likely to have embedded shortwaves, I would
not be surprised to see localized areas of light to moderate snow
showers. These will be tough to forecast, but worth the mention.
Winds look to decrease approaching the weekend leading to a cool
and much calmer weekend forecast. /Fliehman

&&

.AVIATION...
18Z TAFS: A moist warm front will bring lowering cigs from southwest
to northeast with rain developing at KMWH, KEAT 19-20Z spreading
north and east through the afternoon.  Ahead of these increasing
clouds areas of IFR/MVFR stratus have been observed at KMWH, KGEG,
KSFF, KCOE.  These will continue to lift north and west due to
southeast boundary layer winds and should move north of KMWH, KGEG
around 18z and thus started TAF's with VFR conditions at all TAF
sites.  Expect MVFR conditions to develop over most of the region as
precipitation develops with IFR conditions possible along the East
Slopes of the Cascades including KEAT where more significant precip
develops.  Breezy to locally windy conditions are expected to
develop around 3-6z this evening as a deep surface low tracks across
Central BC and pressure gradients tighten across the region.  JW

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        42  33  39  32  40  31 / 100 100  40  70  70  40
Coeur d'Alene  42  33  38  30  39  31 /  90 100  70  70  80  50
Pullman        46  33  40  33  41  32 / 100 100  50  60  70  50
Lewiston       52  36  46  35  46  35 /  80  80  60  50  60  50
Colville       41  33  40  33  41  31 /  80 100  60  80  80  40
Sandpoint      40  34  37  30  39  31 /  70 100  70  80  80  60
Kellogg        42  33  37  30  38  31 /  90 100  70  80  90  60
Moses Lake     44  33  43  34  45  32 / 100  80  20  40  40  30
Wenatchee      37  31  39  32  42  31 / 100  90  30  50  60  30
Omak           39  32  38  31  40  29 /  90 100  30  70  70  30

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Winter Weather Advisory from Noon today to Noon PST Sunday for
     East Slopes Northern Cascades.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SPOKANE WA
618 AM PST SAT FEB 15 2014

IDZ001-WAZ037-038-042-043-161430-
NORTHERN PANHANDLE-NORTHEAST MOUNTAINS-OKANOGAN HIGHLANDS-
EAST SLOPES NORTHERN CASCADES-OKANOGAN VALLEY-
618 AM PST SAT FEB 15 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH IDAHO...
NORTH CENTRAL WASHINGTON AND NORTHEAST WASHINGTON.

.DAY ONE...TODAY AND TONIGHT

A MOIST STORM WILL MOVE INTO EASTERN WASHINGTON AND NORTH IDAHO BY
MIDDAY AND BRING PERIODS OF MODERATE TO LOCALLY HEAVY SNOW TO THE
CASCADES. ELSEWHERE THE HEAVY SNOW WILL BE CONFINED TO THE HIGHEST
MOUNTAINS. THE SNOW WILL TAPER OFF THE SCATTERED SNOW SHOWERS
OVERNIGHT.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

AN ACTIVE WEATHER PATTERN WILL CONTINUE THROUGH THE WEEKEND INTO
THE MIDDLE OF NEXT WEEK WITH SEVERAL ROUNDS OF HEAVY SNOW IN THE
MOUNTAINS. THE VALLEYS WILL SEE A MIX OF RAIN AND SNOW WITH
LIGHT TO MODERATE ACCUMULATIONS POSSIBLE SUNDAY NIGHT INTO
MONDAY. A STRONGER STORM IS ON TRACK TO IMPACT THE REGION ON
TUESDAY INTO EARLY WEDNESDAY.

IDZ002>004-WAZ031>033-035-036-161430-
COEUR D'ALENE AREA-IDAHO PALOUSE-CENTRAL PANHANDLE MOUNTAINS-
NORTHEAST BLUE MOUNTAINS-LOWER GARFIELD AND ASOTIN COUNTIES-
WASHINGTON PALOUSE-UPPER COLUMBIA BASIN-SPOKANE AREA-
618 AM PST SAT FEB 15 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH IDAHO...
EAST CENTRAL WASHINGTON...NORTHEAST WASHINGTON AND SOUTHEAST
WASHINGTON.

.DAY ONE...TODAY AND TONIGHT

A STRONG WARM FRONT WILL MOVE INTO THE REGION TODAY BRINGING
WIDESPREAD MODERATE RAINFALL AS WELL AS LOCALLY HEAVY SNOW TO THE
HIGHEST MOUNTAINS. WINDY CONDITIONS ARE ALSO EXPECTED TONIGHT.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

SEVERAL ROUNDS OF VALLEY RAIN AND MOUNTAIN SNOW WILL IMPACT THE
REGION THROUGH WEDNESDAY. THE RAINFALL COMBINED WITH RUNOFF FROM
SNOW MELT WILL KEEP SMALL STREAMS RUNNING HIGH WITH LOCAL
FLOODING POSSIBLE IN SOME AREAS. ANOTHER STORM WEDNESDAY NIGHT
WILL BE COLDER AND WILL BRING A BETTER CHANCE FOR SNOW
ACCUMULATIONS IN THE VALLEYS.

IDZ026-027-WAZ034-041-044-161430-
LEWISTON AREA-LEWIS AND SOUTHERN NEZ PERCE COUNTIES-
MOSES LAKE AREA-WENATCHEE AREA-WATERVILLE PLATEAU-
618 AM PST SAT FEB 15 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
IDAHO...CENTRAL WASHINGTON...EAST CENTRAL WASHINGTON AND NORTH
CENTRAL WASHINGTON.

.DAY ONE...TODAY AND TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.