Area Forecast Discussion
Issued by NWS Portland, OR

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854
FXUS66 KPQR 221159 AAA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
330 AM PST Tue Jan 22 2019


.SYNOPSIS...A series of fronts traversing the region through the
middle of the week will bring periods of valley rain and mountain
snow before high pressure brings drier weather late in the week and
this weekend.


&&


.SHORT TERM...Today through Friday...Water vapor satellite imagery
early this morning shows a shortwave ridge off the California coast.
Mid and upper level moisture is moving eastward into the Pacific
Northwest as it rides over the top of the upper level ridge. Modest
isentropic lift associated with a passing warm front should allow
light rain to spread across the northern half of the forecast area
later this morning and early this afternoon. Snow levels will
initially start off near 2000 feet this morning before rising to
near 5000 feet by this evening. This should keep snow impacts at a
minimum, even in the south Washington Cascades where precipitation
will be most prevalent.

Once the warm front passes later this afternoon, there will likely
be a break in the rain except across our far northern zones until a
trailing cold front drops southeastward across the area late tonight
and early Wednesday. Precipitation rates will likely be a bit
heavier right ahead of the cold front with hourly rainfall totals of
0.1-0.2" per hour in the Willamette Valley and 0.2-0.4" per hour
across the orographically favored sites in the Coast Range and
Cascades.

Once the front passes, a few light showers will be possible
Wednesday into Wednesday night, but overall the trend will be
towards the area drying out. In locations that clear, areas of late
night and morning fog will develop Wednesday night and early
Thursday. With little to no cold air east of the Cascades, Thursday
and Friday appear mild areawide with lowland and foothill
temperatures rising into the 50s in most locations.

It should be noted that models are converging on the idea that a
shortwave trough will drop southeastward through the Inland
Northwest late Thursday. The most likely impact from this storm
system will be a temporary spike in winds and moisture across the
higher terrain, but there is an outside chance light rain could fall
along the south Washington coast Thursday night. /Neuman


.LONG TERM...Friday night through Tuesday...Operational models and
their ensembles are in good agreement the area will remain under a
large shortwave ridge into early next week. This will produce a
multi-day stretch of dry weather, mild temperatures and areas of
late night and morning valley fog. East winds will initially be near
nonexistent, but appear increasingly likely to strengthen late in
the weekend into early next week.

It should be noted that models suggest the flow will turn weakly
offshore Saturday, particularly along the central Oregon coast. With
850mb temperatures climbing into the 11-13C range, many locations
along the coast, in the Coast Range and even in the Cascade
foothills will climb into the upper 50s to low 60s. Even mid to
upper 60s do not appear out of the question. Willamette Valley
temperatures will be a little more tricky given areas of morning fog
could hamper temperatures from climbing too high. Held temperatures
on the warm side to even slightly above model guidance for most
areas, but still kept temperatures well shy of records for now.
/Neuman


&&


.AVIATION...Conditions are mainly VFR across SW Washington and
NW Oregon this morning. There are a few pockets of fog and low
stratus around, but so far the only TAF site being impacted has
been KHIO. Expect the predominantly VFR conditions to persist
through most of the morning. A warm front approaching the region
is resulting in increasing mid and high clouds right now. Expect
light rain to spread onto the coast by mid-morning, with cigs
lowering to MVFR by 18Z. The rain will spread over the interior
lowlands, mainly north of KSLE by midday. The northern interior
sites may also see some MVFR cigs developing later in the
afternoon as well. Expect little change in the conditions
tonight into early Wed.

KPDX AND APPROACHES...VFR conditions continue through the
morning. Light rain is expected to develop by around midday and
continue at times through tonight into early Wed. Cigs will
gradually lower through the day, with MVFR possible by 21Z-00Z.
Pyle


&&


.MARINE...A low pressure system will be moving toward the
northern end of Vancouver Island today. This will bring a warm
front through the waters today, resulting in increasing southerly
winds. Then the trailing cold front will move through tonight. The
strongest winds look to be over the northern waters, where
consistent gusts of 25 to 30 kt are expected to persist through
much of tonight. There may even be some occasional gusts to 35
kt. Winds should be a little lighter over the central OR waters.
A small craft advisory for winds is in effect for all of the
waters through early Wed morning. Winds will drop off fairly
quickly Wed behind the frontal passage. Then expect a period of
rather benign conditions to develop that will likely last into at
least early next week.

Seas will remain around 6 to 8 ft this morning. Then expect them
to build into the low teens this afternoon. A small craft
advisory has been issued for seas from this afternoon through Wed
afternoon. Seas may end up remaining near or above 10 ft into
early Thu. Seas then subside below 10 ft Thu and should remain
below for the next several days. Pyle


&&


.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Coastal Flood Advisory from noon today to 4 PM PST this
     afternoon for North Oregon Coast.

WA...Coastal Flood Advisory from noon today to 4 PM PST this
     afternoon for South Washington Coast.

     Winter Weather Advisory until 10 PM PST this evening for South
     Washington Cascades.

PZ...Small Craft Advisory for winds until 7 AM PST Wednesday for
     Coastal Waters from Cape Shoalwater WA to Cascade Head OR
     out 60 NM.

     Small Craft Advisory for hazardous seas from 10 AM this morning
     to 4 PM PST Wednesday for Coastal Waters from Cape
     Shoalwater WA to Florence OR out 60 NM.

     Small Craft Advisory for winds until 7 AM PST Wednesday for
     Coastal Waters from Cascade Head OR to Florence OR out 60
     NM.

     Small Craft Advisory for Rough Columbia River Bar from 4 PM
     this afternoon to 8 PM PST this evening.

&&


$$

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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. This area is
commonly referred to as the forecast area.



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