Debris Flow and Flooding in Washington, March 5 to 6, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
224 AM PST Wed Mar 5 2014

.SYNOPSIS...
A wet storm system will bring periods of moderate to heavy rain
to the Inland Northwest today and tonight. The combination of
rain and melting snow will likely produce minor farmland flooding
and ponding of water in urban areas with poor drainage. Mild and
breezy conditions are expected Thursday with scattered showers.
There should be a break in the active weather Friday and Saturday
before the arrival of more rain Saturday night into Sunday.

&&

.DISCUSSION...
Today through Thursday...A pair of surface low pressure centers
will whirligig around each other just offshore through the next
36 hours...each in turn flinging it's complex of warm fronts and
occlusions through the forecast area. These frontal surface
lifting mechanisms will be well fueled with deep fetches of
Pacific subtropical moisture. Satellite indicates the offending
lows pirouetting on the Pacific dance floor along 140W latitude.
The first warm front appending from the northern storm is forming
over the forecast area at this time and will push through this
morning followed immediately by an occluded front which is
approaching the Pacific coast at 2 am. A short but perceptible
break period will occur this afternoon (from steady moderate rain
in the morning to simply scattered/numerous showers in the
afternoon) before the southern storm of the couplet hurls it's
warm front through the region tonight for another wet overnight
period. The forecast area will reside in the breezy warm sector
during the day on Thursday before the second occluded front sweeps
through late Thursday or Thursday evening.

Ramifications of this series of rain events will include rising
snow levels to the point where only the higher elevations will
receive relatively moderate wet snow accumulations. The valleys
and basin locations will receive...from today through Friday
morning...anywhere from 1/4 to 1/3 of an inch in the deep basin to
3/4 to near 1 inch over the east basin rise to well over 1 inch of
rain in the valleys of the northeast Washington mountains and
Idaho Panhandle. Small stream and urban flooding will likely be a
factor to contend with over the next few days. The current Areal
Flood Watch for much of the eastern forecast area is well
justified and will probably be upgraded to a warning or at least
advisory in the next 24 hours or so.

Also...a handful of mainstem rivers mainly draining the Idaho
Panhandle will experience sharp rises probably at least to Action
Stage over the next few days and may kiss Flood Stage in the
coming week. This is not a certainty yet but the situation will be
monitored closely by subsequent shifts. See the latest river
statement for details. /Fugazzi

Thursday night through Sunday night: Expect continued rain and
high mountain snow chances, especially Thursday night and again
Saturday night into Sunday. Initially PoPs remain high Thursday
evening, save for the lee of the Cascades and deeper basin. This
is the product of wrap-around moisture, a lingering surface trough
and passing upper disturbances. Between late Thursday night
through Friday night a ridge of high pressure builds in, the flow
turns northwest and somewhat drier air invades. So precipitation
chances will gradually retreat to the mountains and wane. However
with high pressure building in and a warm front approaching, look
for the potential for fog across the northern valleys (including
the Spokane/C'DA area) and the more sheltered Cascade valleys
Friday night into Saturday morning.

Saturday the SFC-850 mb flow becomes southerly and a warm front
lifts in, while the next cold front approaches the coast. Isentropic
ascent increases but the best moisture remains near the Cascades
and Canadian border. Here is where the main shower chances will
lay.

Saturday night into Sunday the precipitation threat blossoms
across the region. Current model depictions show the best chances
start near the Cascades and expand east late Saturday evening or
early overnight. This will be thanks a modest moisture tap feeding
in ahead of a cold front and upper wave. Some models indicate PWATs
rise to between 0.60 and 0.90 inches (or ~200-250% of normal).
Then sometime between Sunday afternoon and Sunday night the cold
front pushes through, leading to rapidly waning precipitation
chances from the west so that by early Monday morning the primary
threat will be backed against the Cascade crest and across the
eastern mountains. With cold front and upper wave passage some
models suggest a few pockets of instability (including low-grade
CAPE). So I cannot rule out the potential for a few thunderstorms,
including near the Cascades to Upper Columbia Basin and southeast
WA/southern Panhandle. At this time, however, model agreement is
too low to place such a threat in the forecast with any confidence.

Models are obviously still coming together on precise amounts, but
24-hour precipitation amounts range between 0.25 to 0.50" in many
areas, with local 24-hour precipitation amounts approaching 0.75
to 1.00" near the Cascade crest and near the WA/ID border eastward.
Not all areas of the Inland NW may see much precipitation, including
the lee of the Cascades and deeper Basin. Some higher resolution
models show 24-hours amounts of less than a tenth of an inch. This
is a definite possibility. These details carry low confidence as
there are some definite differences in the precise timing of the
cold front passage. A slower passage could mean more
precipitation, while faster passage would limit amounts.

The stout southerly flow is expected to push mild air into the
region with snow levels ranging from near 5kft near the Canadian
border to near 7.5kft toward the southern WA and the Camas Prairie.
"Normal" highs are in the mid to upper 40s to lower 50s this time
of year. So the southerly flow could easily pushing temperatures
above normal (or into the 50s or even lower 60s in the case of the
deeper Basin). These numbers could be held back some by cloud
cover and/or developing precipitation. The modest south to
southwest winds and mixing along the incoming cold front will
contribute to the breezy to locally windy conditions by Sunday
afternoon. And while winds in the lower elevations are projected
to abate some later Sunday night, they will remain stronger in the
mountains. The combination of rain, mild winds and snow melt may
bring additional flooding concerns. /J. Cote'

Monday and Tuesday: Region looks to stay in somewhat of an active
pattern as another storm moves in from the Pacific. The difference
between this storm and the last few is that it is coming from the
northern Pacific rather than the southern subtropical region. This
being said, it will lack a good subtropical moisture feed limiting
the precipitation we can expect. Snow levels will also be
considerably lower allowing for mountain snow and valley rain.
With the system lacking sufficient moisture for abundant,
widespread rain, this should allow some of the hydro concerns of
the past to diminish. POPs were increased Monday afternoon into
Tuesday as the Euro, GFS and GEM all seem in agreement of the
incoming system. The higher elevations of the Cascades and
Panhandle will likely receive the best precipitation amounts due
to its westerly track through the region. Specifics on the system
will have to wait, but overall models like the chances of this
system passing through the Inland NW.

Concerning temperatures, the region looks to remain near normal
with valleys highs in the 40s and 50s with overnight lows dipping
into the 30s. The main thing to note in this period will be the
passing of the mentioned system as other aspects of the forecast
look to remain seasonal. /Fliehman

&&

.AVIATION...
06Z TAFS: A break in the precipitation will occur over the next
few hours with just isolated showers over the Idaho panhandle and
along the Cascade crest. The next in a train of weather
disturbances will move over the Inland Northwest later tonight.
This next round of precipitation will develop around 09Z and
should overspread all sites by 13Z. TAF sites will see a brief
break in precipitation Wednesday afternoon then the next warm
front will bring another round of rain to the area. /EK

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        47  38  48  35  47  34 / 100 100  70  60  10  10
Coeur d'Alene  46  37  46  35  46  32 / 100 100  90  70  30  10
Pullman        50  39  49  36  49  35 / 100 100  80  60  20  10
Lewiston       55  43  54  40  55  35 /  80  90  70  40  20  10
Colville       45  37  49  33  47  32 / 100 100  80  60  10  10
Sandpoint      42  37  45  34  44  31 / 100 100 100  80  30  10
Kellogg        43  37  44  33  43  31 / 100 100 100  80  50  20
Moses Lake     54  41  57  38  56  37 /  90 100  40  20  10  10
Wenatchee      49  38  52  37  53  34 /  90 100  60  20  10  10
Omak           44  37  49  34  48  31 / 100 100  70  20  10  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Flood Watch through Friday morning for Central Panhandle
     Mountains-Coeur d'Alene Area-Idaho Palouse-Northern
     Panhandle.

WA...Flood Watch through Friday morning for Northeast Mountains-
     Okanogan Highlands-Spokane Area-Upper Columbia Basin-
     Washington Palouse.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SPOKANE WA
227 PM PST TUE MAR 4 2014

WAZ037-038-043-052230-
NORTHEAST MOUNTAINS-OKANOGAN HIGHLANDS-OKANOGAN VALLEY-
227 PM PST TUE MAR 4 2014

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

TEMPERATURES WILL CONTINUE TO WARM WHILE WET WEATHER WILL LIKELY
PERSIST FOR MUCH OF THE WEEK. THIS WILL ALLOW THE MAJORITY OF THE
LOWLAND SNOW PACK TO MELT...LEADING TO THE POSSIBILITY OF LOWLAND
FLOODING..

IDZ001-004-052230-
NORTHERN PANHANDLE-CENTRAL PANHANDLE MOUNTAINS-
227 PM PST TUE MAR 4 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH IDAHO.

.DAY ONE...THIS AFTERNOON AND TONIGHT

TEMPERATURES WILL BEGIN WARMING TODAY LEADING TO MELTING SNOW AND
POSSIBLE SMALL STREAM FLOODING.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

TEMPERATURES WILL CONTINUE TO WARM AND FURTHER PRECIPITATION WILL
BE MAINLY RAIN. WET WEATHER IS LIKELY TO PERSIST THROUGH MUCH OF
THE WEEK WITH MOST OF THE SNOW OCCURRING OVER THE HIGHEST
MOUNTAINS. MEANWHILE LOWLAND FLOODING WILL BE POSSIBLE DUE TO A
COMBINATION OF RAINFALL AND SNOW MELT.

WAZ042-052230-
EAST SLOPES NORTHERN CASCADES-
227 PM PST TUE MAR 4 2014

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

HAZARDOUS WEATHER IS NOT EXPECTED.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

TEMPERATURES WILL BEGIN WARMING AND SNOW WILL TRANSITION TO RAIN
IN THE VALLEYS. WET WEATHER IS LIKELY TO PERSIST THROUGH MUCH OF
THE WEEK WITH MOST OF THE SNOW OCCURRING OVER THE HIGHEST
MOUNTAINS. MEANWHILE LOWLAND AND SMALL STREAM FLOODING WILL BE
POSSIBLE DUE TO A COMBINATION OF RAINFALL AND SNOW MELT.

IDZ002-003-WAZ033-035-036-052230-
COEUR D'ALENE AREA-IDAHO PALOUSE-WASHINGTON PALOUSE-
UPPER COLUMBIA BASIN-SPOKANE AREA-
227 PM PST TUE MAR 4 2014

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

TEMPERATURES WILL BEGIN WARMING WHILE WET WEATHER WILL LIKELY
PERSIST FOR MUCH OF THE WEEK. THIS WILL ALLOW THE MAJORITY OF THE
LOWLAND SNOW PACK TO MELT...LEADING TO THE POSSIBILITY OF LOWLAND
FLOODING..

WAZ034-041-044-052230-
MOSES LAKE AREA-WENATCHEE AREA-WATERVILLE PLATEAU-
227 PM PST TUE MAR 4 2014

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

IDZ026-027-WAZ031-032-052230-
LEWISTON AREA-LEWIS AND SOUTHERN NEZ PERCE COUNTIES-
NORTHEAST BLUE MOUNTAINS-LOWER GARFIELD AND ASOTIN COUNTIES-
227 PM PST TUE MAR 4 2014

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

TEMPERATURES WILL BEGIN WARMING WHILE WET WEATHER WILL LIKELY
PERSIST FOR MUCH OF THE WEEK. THIS WILL ALLOW THE MAJORITY OF THE
LOWLAND SNOW PACK TO MELT...LEADING TO THE POSSIBILITY OF LOWLAND
FLOODING..