Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Portland or
300 PM PST Wednesday Feb 10 2016
Synopsis...mild air mass to remain over the region through Friday.
Weak fronts offshore will brush the northwest today and Thursday...with variable
cloudiness across the region...along with some spotty light rain
along the coast and possibly inland. That changes by Friday...as first
in a series of fronts push into the Pacific northwest. Showery on Saturday...but
more rain arrives on Sunday.
Short term...today through Saturday...satellite imagery this
afternoon shows the remnants of a middle level front pushing eastward
into the Cascades after bringing a few sprinkles to parts of the
Willamette Valley earlier today. Low level clouds and areas of
drizzle and light rain have pushed into the coast this afternoon.
This area of wet weather should have a difficult time pushing inland
overnight before it falls apart. Will keep in slight chance to low
end chance probability of precipitation across much of the Willamette Valley to account for
uncertainty...but at this point...it appears any wet weather will
primarily remain confined to the coast and Coast Range. The area
along the lower Columbia River between Portland and Kelso/Longview
being the most likely area in the interior to experience some wet
A low pressure system is still on track to deepen as it moves
northward along 140w on Thursday. A warm front will spread northward
in response and increase rain chances across the area on Thursday. At
this point...the deepest moisture and best dynamics will primarily
stay offshore...but nonetheless...there should be enough moisture and
lift to produce periods of rain...particularly near the coast and
across our more northern zones Thursday afternoon.
There is still some modest disagreement in regards to the timing of
when a trailing cold front will push through the region Thursday
night and/or Friday morning. While timing is still
uncertain...confidence is high that the area will receive a solid
round of rain at some point during this time. 12z model guidance
suggested there may be enough instability aloft to produce a few
elevated thunderstorms ahead of the front...but will hold off on
adding thunder to the forecast until models display better
As colder air spreads into the region Friday...expect snow levels to
lower into the 4000-4500 feet range and perhaps another 500-1000 feet
lower Friday night into early Saturday. Quantitative precipitation forecast should be sufficient to
bring some accumulating snow to the Cascades and create a period of
hazardous travel conditions...but not sure it will be enough to
warrant a Winter Weather Advisory. /Neuman
Long term...Saturday night through Wednesday...the progressive
weather pattern will persist into next week. Models continue to show
a front moving across the Pacific northwest late Saturday/early Sunday. Have
increased probability of precipitation across much of the region Saturday evening to account
for the faster timing of the European model (ecmwf). Not expecting to see a lot of
Cascade snow with this front as snow levels quickly rise above 7000
feet early Sunday. We could see a brief break from the rain Monday as
a transient upper level ridge moves across the region...but will
maintain chance probability of precipitation due to some lingering instability. A weak
shortwave could bring some light showers Tuesday. Another front
arrives late Tuesday and should bring more rain and Cascade snow to
the region...with snow levels lowering to around 3500 feet Wednesday
afternoon. Temperatures look to remain slightly above normal through the
forecast...but will trend cooler after Monday. /64
Aviation...mostly VFR inland this evening with a mix of MVFR and
IFR along the coast. Conditions should improve along the coast
briefly later this evening then deteriorate again late tonight
into Thursday morning as a warm front approaches. The warm front will
bring a mix of VFR and MVFR conditions across the area Thursday.
Kpdx and approaches...VFR conditions tonight and Thursday morning.
MVFR ceilings possible late Thursday morning through Thursday
Marine...buoy observations show that south winds are gusting to
25 knots across the waters this afternoon. These winds should ease
early this evening then back to the southeast tonight. A frontal system
will support another round of small craft winds Thursday and
Friday. A series of lows offshore will result in confused seas
Thursday and Thursday night...with a long-period SW swell and a
shorter period northwest swell moving through the waters. The combined
seas will range between 10 and 14 feet. Tj
Pz...Small Craft Advisory for winds from 10 am Thursday to 4 am PST
Friday for waters from Cape Shoalwater Washington to Florence or from 10
to 60 nm.
Small Craft Advisory for hazardous seas from 10 PM this evening
to 4 PM PST Friday for coastal waters from Cape Shoalwater Washington
to Florence or out 60 nm.
Small Craft Advisory for winds from 4 PM Thursday to 4 am PST
Friday for coastal waters from Cape Shoalwater Washington to Florence or
out 10 nm.
Small Craft Advisory for rough Columbia River bar until 9 PM
PST this evening.
Small Craft Advisory for rough Columbia River bar from 4 am to
9 am PST Thursday.
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This discussion is for northwest Oregon and southwest Washington
from the Cascade crest to 60 nautical miles offshore. The area is
commonly referred to as the forecast area.