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Area forecast discussion 
National Weather Service Portland or
340 am PDT Sat Oct 25 2014

Synopsis...a low pressure system will move north up the Oregon coast today
then move inland over SW Washington towards Puget Sound sound this evening
bringing windy conditions to the region this afternoon and evening.
A cold front will follow the low turning the flow onshore tonight
and sun as an upper level trough moves across. Weak high pressure will
move across the region Sun night...then another frontal system will
move in Monday and Tuesday as a low pressure system moves into British Columbia.
&&

Short term...surface low was seen in satellite imagery near 40n
129w at 08z moving NE. Buoy 46002 showed a pressure of 990 mb north of the
low...suggesting a central pressure at least a few mb below 990. Overall
prefer the European model (ecmwf) for placement and pressure...although models have come
around to a much more cohesive picture of low. A southerly jet along
the east side of the upper trough suggests a turn to the north for the low
today...which models now uniformly bring up just off the Oregon
coast today while beginning to fill. There is a little spread in
where the models bring the low inland...but consensus seems to
suggest the lowmaking landfall on the S Washington coast between 21z and 00z
today before heading towards the S Puget Sound sound area. With surface
pressure gradients generally depicted around 14 to 16 mb down the oreogn
coast as the low moves inland...will Post high wind warnings for the
central and north Oregon coast and the north Oregon Coast Range. S Washington coast
is a little iffy based on the uncertainty of the exact track of the
low. With the best guess for the low moving inland over Pacific
County will hold off on any warnings for the S Washington coast and Willapa
Hills...although it may ultimately require a warning later today. A
the track of the low expected across the S sound suggests windy
conditions extending into the Willamette Valley and I-5 corridor
late today and this evening. Models indicating about a 6 mb pressure
gradient between keug and kpdx as the low passes by to the
north..probably not enough for a High Wind Warning but gusts to 50 miles per hour
nonetheless. Overall the peak winds today and this evening expected
to be relatively quick to pass as the low moves through quickly and
cold front follows quickly.

Lighting indicated on lightning detection networks to the north of the
low early this morning offshore. Will add a mention of thunder to
the coastal waters today as the low lifts north...and include a slight
chance in SW Washington late today. With the warm front already north and the
low passing by to the north...rainfall is not a complete gimmie
today...especially points further inland. Better probability of precipitation will come tonight in
the westerly onshore flow following the cold front as the colder air
aloft with the upper trough destabilizes the atmosphere and
orographics add lift to the windward mountains. The cooler air
following the front expected to drop snow levels down to around 4500
feet by Sun morning...in time to expect at least a few inches of snow
for the passes in the orographic showers.

A weak ridge Sun night will bring a slow end to the showers as well
as some cooler temperatures. The next system though...this one tracking east
across the North Pacific towards British Columbia...will bring the next threat of rain
to the north part of the forecast area Monday in an area of moist warm air
advection.

Long term...no changes. Previous discussion follows. The long term
starts out wet with the next system moving into the forecast area
Monday night. This system contains the remnants of Hurricane Ana...that
skirted Hawaii last week. Models may be under doing the potential
with this one. A strong jet stream will remain directed at Washington and
northern Oregon through Tuesday night. Models show large variations beginning
Wednesday...but expect the active pattern to continue. The European model (ecmwf) and GFS
show a trend toward drier conditions late next week as a deep low in
the Gulf of Alaska amplifies the downstream ridge over the
intermountain west. Weishaar

&&

Aviation...the area is currently in the warm sector ahead of the
approaching low and associated front. VFR prevails currently with
offshore flow. However inland areas have increasing IFR fog
conditions as clouds have thinned so areas of fog will probably
persist through 16z. A strong low and associated front approach
from the southwest later this morning and afternoon. The low will
track to the South Washington coast. Expect gusty south winds to impact
coast after 18z...then after 22z inland.

Kpdx and approaches...partial clearing of middle and high clouds
allowing fog to develop. Expect IFR in fog at times through about
16z for western approaches. Gusty east winds near the Columbia River
gorge this morning then south to southwest winds with gusts 25-35 knots are
expected 22z Sat through 03z sun.

&&

Marine...deepening low pressure center off the northern California is
tracking north-northeast and is forecast to move through the
coastal waters later this morning and afternoon...making landfall
on the south or central Washington coast late this afternoon.
East to southeast winds are expected to rapidly switch to
southerly gales as the low and associated front nears. There could
be a brief period of coastal jet development as the front nears
later this afternoon...in the 2 to 5 PM period. Late afternoon
the winds will switch to the west to southwest then ease
overnight...but remain gusty especially in the northern zones
where gale gusts should persist into the evening. High pressure
builds into the Pacific northwest sun and Monday. Another front expected to
approach the region early next week with Small Craft Advisory
winds.

Seas generally starting out around 10 feet will probably build to
around 15-17 feet given the short fetch time. Seas gradually subside
below 10 feet Sunday. Seas likely to climb to around 14 feet with the
front late Monday or Tuesday. /26
&&

Pqr watches/warnings/advisories...
or...Wind Advisory from 3 PM this afternoon to 9 PM PDT this evening
for central Willamette Valley-greater Portland metropolitan area-
lower Columbia.

High Wind Warning from noon today to 5 PM PDT this afternoon for
central Oregon coast-north Oregon coast.

High Wind Warning from noon today to 7 PM PDT this evening for
Coast Range of northwest Oregon.

Washington...Wind Advisory from 3 PM this afternoon to 9 PM PDT this evening
for Greater Vancouver area-I-5 corridor in Cowlitz County.

Pz...Gale Warning until 11 PM PDT this evening for coastal waters from
Cape Shoalwater Washington to Cascade Head or out 60 nm.

Gale Warning until 5 PM PDT this afternoon for coastal waters from
Cascade Head or to Florence or out 60 nm.

Small Craft Advisory for rough Columbia River bar until 5 am PDT
Sunday.

&&

$$

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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.
&&

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