Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Portland or
248 am PST Monday Feb 8 2016
Synopsis...high pressure over region will maintain dry mild days though
will have areas of late night/am fog and low clouds in interior
valleys. Weak front will arrive later Wednesday...but not much in way of
rain. Other fronts arrive later in the week...bringing an increasing
chance of rain to close the week.
Short term...today through Wednesday...
not much change. High pressure will sit over the region...maintaining dry
and mild conditions. With thermal low pressure along the coast and higher
pressure east of the Cascades...low level offshore flow will continue.
But since this is a mostly gap driven wind event...the breezy winds
will be generally through the Columbia River gorge...and somewhat
through the gaps in the coastal mountains into the coastal lowlands. At 2
am...cross gorge gradient running near 7 mb offshore. This will
tighten a bit more today...holding at 7 to 8 mb through Tuesday. So...
can expect gusts around Troutdale of 35 to 45 miles per hour. Further into the
western Columbia Gorge...winds will gust 45 to 60 miles per hour.
Air mass aloft is rather warm for this time of the year. Will likely
see many locations reaching the 60s again today...especially along
the coast...Coast Range and through the inland valleys. Would not be
surprised if a few spots along the coast reach around 70 degree today.
Challenge is for the inland areas. With The Gap driven winds keeping
bulk of Portland/Vancouver area in the clear with temperatures
climbing into the upper 50s to lower 60s. But...areas to short wave of
Portland and north of Vancouver will see areas of low clouds and fog this
am. At 2 am...fog still affecting Scappoose and Hillsboro...and to
south of Salem. While not all that deep... local guidance indicates
that the fog/low clouds burn off later this am...with the south
Willamette Valley clearing last...sometime between 1 and 3 PM. As a
result... temperatures will but somewhat cooler...with highs mostly
50 to 55 for areas S of Salem...and maybe in Cowlitz valley.
East winds relax Tuesday night and Wednesday as the upper ridge moves
east and the first system trying to knock down the upper ridge
reaches or approaches the coast. We should still see quite a bit of
morning fog inland Wednesday morning...and perhaps some small chances
of rain along the coast as this first system weakens dramatically.
Long term...Wednesday night through Sunday...active and
more seasonable weather pattern sets up for late this week. Coast
may see some sprinkles or light rain Wednesday night into Thursday
as a frontal boundary stalls offshore. The front is finally pushed
eastward on Friday...bringing a decent chance for rain across
western Oregon and southwest Washington. Rain turns to showers
behind the front and starts to taper off late Friday into Saturday.
Saturday could be mostly dry before another system brings more rain
on Sunday. -McCoy
Aviation...offshore flow pattern to continue for the next 24 hours.
This means VFR to prevail across most of the area...except for
LIFR in the southern Willamette Valley. Do not expect this area
to improve much until this afternoon. There is also chance of
patchy IFR in the interior valleys north of kcvo through about
Kpdx and approaches...VFR expected to prevail through tonight.
However...there is a slight chance of patchy IFR around the
terminal between 13z and 16z. East wind gusting to 35 knots at the
west end of the Columbia Gorge will increase today...with gusts
up to 50 knots possible by 00z Tuesday. Pyle
Marine...offshore wind will continue through tonight...with
gusts up to 20 knots likely near coastal terrain gaps. A warm front
may bring southerly wind gusts to 20 knots Tuesday. Another system moves
through the waters Wednesday and may bring a period of Small Craft
Advisory winds. Additional systems are expected later in the week
and next weekend as the weather pattern becomes more active.
Seas running 5 to 6 feet this morning. However...a westerly long period
swell is beginning to build in and has shown up at buoy 89. Seas will
be peaking in the 10 to 12 feet range...before dropping below
10 feet again tonight. Seas will increase during the second half of
the week due to the increasingly active weather pattern. Pyle
Pz...Small Craft Advisory for hazardous seas today through early
this evening on all coastal waters.
Small Craft Advisory for rough Columbia River bar conditions
today through early this evening.
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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.