Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 261142

Area Forecast Discussion
National Weather Service Spokane WA
442 AM PDT Sun Mar 26 2017

A weak ridge of high pressure will keep dry weather across the
region this morning. Another wet weather system will move quickly
into the region this afternoon and result in widespread valley
rain and mountain snow. Showery weather is then expected to
persist into early next week. The next chance of widespread
moderate precipitation will arrive on Wednesday and Thursday.


Today through Monday night...Weak high pressure is over the Pac NW
this morning ahead of the next upstream weather system currently
moving into the eastern Pacific. We are already seeing high level
clouds move into the region from this disturbance. For this
morning there may be some localized fog/stratus along area rivers,
and likely pretty shallow that will dissipate quickly after
sunrise .

The next storm system will move into the region by mid-day. This
storm is very similar to the past several disturbances that have
moved through the region the past week or so. A wet warm front
followed quickly by a cold front 6-12 hours later. The biggest
difference is that it will not be able to tap into quite as much
Pacific moisture. The warm front will cross the Cascades before
mid-day today with the cold front following this evening.
Widespread light to locally moderate stratiform precipitation is
still expected this afternoon and through the evening, then rapid
drying from the west Monday morning, with showers Monday through
about sunset and through the night for the Panhandle mountains.

Precipitation amounts will range from around a tenth in the
Columbia Basin to about a quarter of an inch for the mountains
and possibly as much as a half inch for the Cascade crest. Snow
levels near the Cascades will be 3000-3500 feet and across the SE
zones and the Blue mountains between 4000-5000 feet. Snow amounts
of 3-5 inches will be possible for the highest elevations for the
mountains and for the Cascades 4-7 inches with up to a foot
possible near the crest.

Winds will become gusty behind the frontal passage on Monday across
the eastern Basin, the Palouse and north towards the Spokane-
Coeur D`Alene corridor Monday afternoon with gusts 20-25 mph.
Temperatures will be in the 40s and 50s today and a few degrees
warmer on Monday.

Impacts: Some mountain snow for the passes will be possible along
I-90, Highway 2 and over the Sherman Pass along highway 20 Sunday
night. While the precipitation with this storm system is expected
to be less than the last few storms we can still expect area
rivers and streams to run very high. Areas that have field
flooding and nuisance flooding will not see much relief.
Highlights are in effect and will be updated as needed. Tobin

Tuesday: The shortwave ridge begins to flatten as the next
weather system approaches the area. Precipitable water values
will increase through the day. Given the low level southerly winds
and moist atmosphere, there will be a good chance of showers
across the mountains.

Tuesday Night through Thursday Night: A warm front will spread
into the area. There is a very good precipitable water tap that
will continue to increase through the night and Wednesday. At 12Z
Wed the GFS, NAM and SREF are all in good agreement of PW values
across the region. At 00Z Thur the GEFS plumes for Spokane shows
the operational GFS having PW values of 0.79, which would be a
record for that day. The mean of the ensembles is 0.72. Given the
good agreement, have ramped up the chance of preciptiation as well
as amounts. Tuesday night our chance of precip will increase.
Expect another very soggy Wednesday. Precipitation amounts could
be high...with valleys seeing anywhere from a quarter to six
tenths of an inch with higher amounts in the mountains. Snow
levels will be fairly high, above 4500 ft. So a valley rain and
high mountains snow event is expected. Wednesday night the cold
front will pass and snow levels will start to come down, but still
remain above the valley floors. It will be possible for Spokane
to climb to the 2nd wettest March spot on the climate records. At
this time do not think Spokane will make it to the number one
spot. The chance of precipitation will decrease for the Columbia
Basin Wednesday night through Thursday night. Showers will
continue across eastern WA and north ID through Thursday and then
will finally decrease Thursday night as that ridge begins to push

*Expect area rivers to respond to the moderate to heavy rain
Wednesday. Rivers, small streams and creeks will rise once again.
Ponding of water over roadways and fields is quite possible as
well. Cannot rule out the continued problems of debris flows,
rock slides and wash outs as the ground remains saturated from
all the rain.

Friday through Sunday: An upper level ridge builds with dry
northerly flow moving into the region on Friday. Then Friday night
into Saturday the flow turns more westerly. The GFS and EC start
to diverge on whether to keep the ridge over the area (GFS) or to
bring another trough through the Pac NW (EC). Given the
uncertainty in the forecast did not change much in the forecast
for this period. Have mention of showers mainly for north ID.
Temperatures will remain near or slightly above average. /Nisbet


12Z TAFs: Clouds are increasing from the west this morning ahead
of an incoming weather system. For early this morning there will
be the possibility for localized fog/stratus along the river near
KSFF although confidence is not very high. Then expect the deck
to lower below bkn-ovc100 between 16-19z. Precipitation chances
will increase from the southwest after 18z at KEAT and after
20-22z for the eastern TAF sites...with cigs dropping down the
MVFR and likely remaining MVFR through 12z. Stratiform -ra will
turn to -shra for KEAT/KMWH after 04-06z. Tobin


Spokane        48  38  50  35  48  39 /  70  80  40  10  20  40
Coeur d`Alene  48  37  48  35  46  37 /  50  80  70  30  30  30
Pullman        49  38  50  35  49  39 /  70  70  60  20  10  30
Lewiston       52  40  55  37  54  42 /  20  80  50  20  10  10
Colville       48  36  50  34  47  36 /  40  90  40  10  50  60
Sandpoint      44  33  45  32  44  34 /  10  80  50  20  50  50
Kellogg        45  34  45  34  44  35 /  20  90  90  40  40  40
Moses Lake     51  38  58  38  56  42 /  60  60  10  10  10  60
Wenatchee      49  35  55  36  52  38 /  80  60  20  10  20  60
Omak           51  36  54  35  50  38 /  70  90  20   0  20  60



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