Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 212211

Area Forecast Discussion
National Weather Service Portland OR
311 PM PDT Wed Mar 21 2018

.SYNOPSIS...A large arae of precipitation spreading into California
today will move into western Oregon this evening and will overspread
the entire area tonight. Total rainfall of 0.5 to 1 inch is expected
in the valleys with 1 to 2 inches at elevation. An extended period of
cold weather behind this front will bring rain showers with mountain
snow showers through the weekend. Snow levels may drop as low as 1000
to 1500 feet on Saturday, but no snow is expected in the Willamette
Valley. Cool and mostly dry pattern continues through the first part
of next week.


.SHORT TERM...Today through Saturday...First round of rain lifted
through western Oregon this afternoon as an area of deep moisture
continues to push into the region. Precipitation rates will intensify
this evening as the upper trough and cold front approach the area.
The combination of strong forcing and PW values near the 90th
percentile will lead to a period of moderate to heavy rain this
evening. Initially, snow levels will be too high for any snow at pass
level, but snow levels will drop through the day Thursday with
accumulation expected down to at least 2000 feet starting Thursday
evening and through Saturday. During the showers on Saturday, snow
levels will be hovering between 1000 and 1500 feet. Therefore, some
of the higher hills in the Willamette Valley may see some snow mixing
in with the rain showers. However, at this time do not anticipate
much if any accumulations in this 1000 to 1500 foot range, and expect
roadways to remain wet. Did not make any significant changes to the
snow forecast with 10 to 20 inches still expected for the Cascades
and 3 to 10 inches of snow expected above pass level in the Coast
Range/Willapa Hills. /Bentley

.LONG TERM...Saturday night through Wednesday. Forecast models in
slightly better agreement today concerning the weekend and into
early next week. The upper level trough is expected to advance
inland into far southern Oregon or northern California late Saturday
night before reaching the Great Basin on Sunday. This will enable a
cold air mass to move into the Pacific Northwest and maintain lower
snow levels (1,500 to 2,000 feet) through Sunday afternoon or
evening. Meanwhile, a building upper level ridge over the Pacific
will eventually bring rising heights late Sunday through the start
of next week. While showers will continue in the northwest flow
aloft on Sunday, the flow will turn to a more north or perhaps
northeast direction early next week. Thus, restricted mention of
precipitation to a slight chance on Monday and removed all mention
of PoPs starting Monday night. Depending on the strength and
position of the ridge, it is possible some light precipitation may
be possible across the northern portions of the area at times given
some weak impulses embedded in the flow. Given this pattern, have
trended temperatures gradually warmer for the start of next, with
temperatures again approaching 60 in the interior lowlands for the
middle of next week.Cullen

.AVIATION...Expect a mix of VFR and MVFR for the inland areas
this evening through Thursday morning as a weak frontal system
moves across the area. A mix of MVFR and IFR s expected for the
coast through Thursday morning. Winds will be light and variable
tonight then predominately SW-S on Thursday. Rain tonight through
Thursday with showers Thursday afternoon and evening.
Gusty winds are likely along the coast Thursday afternoon and
evening. Thunderstorms are possible along the coast THursday
afternoon and evening.

KPDX AND APPROACHES...VFR likely to prevail tonight and Thursday.
MVFR cigs are possible with the steadier rain tonight into
Thursday morning. ~TJ


.MARINE...A weak warm front will move across the waters tonight
for light and variable winds and low seas. A cold front follows
close behind Thursday morning. West winds will increase behind
this front Thursday morning and seas will begin to build. The
winds and seas will intensify more Thursday afternoon as the next
stronger front approaches. Expect Small craft conditions for the
waters Thursday afternoon. There may be a brief period of gale
gusts Thursday night south of Cascade Head. Right now these gusts
look very short lived and over a small area so opted to not
issue a gale watch. However if the 00z models strengthen the
winds or become more in agreement with each other, a Gale Warning
may be needed for the southern waters.

The seas will build above 10 feet Thursday afternoon peaking at
12 to 14 feet late Thursday night and subsiding below 10 feet
Friday night or Saturday morning. The seas will be a mix of wind
wave, fresh SW swell and distant source NW swell. ~TJ


PZ...Small Craft Advisory for winds from 5 AM Thursday to 5 AM PDT
     Friday for Waters from Cape Shoalwater WA to Florence OR
     from 10 to 60 NM.

     Small Craft Advisory for hazardous seas from 5 PM Thursday to 5
     PM PDT Friday for Coastal Waters from Cape Shoalwater WA
     to Cascade Head OR out 60 NM.

     Small Craft Advisory for winds from 11 AM Thursday to 5 AM PDT
     Friday for Coastal Waters from Cape Shoalwater WA to
     Florence OR out 10 NM.

     Small Craft Advisory for hazardous seas from 5 PM Thursday to 5
     PM PDT Saturday for Coastal Waters from Cascade Head OR to
     Florence OR out 60 NM.


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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 CWA or forecast area. is the U.S. government's official web portal to all federal, state and local government web resources and services.