Area Forecast Discussion
Issued by NWS Portland, OR
FXUS66 KPQR 271002
Area Forecast Discussion
National Weather Service Portland OR
259 AM PDT Mon Jun 27 2016
.SYNOPSIS...Summer time weather over the region through next weekend.
High pressure over the region will maintain dry and warm conditions.
But, a bit more onshore flow tonight and Tue will push the marine low
clouds from the coast into the interior valleys.
.SHORT TERM...(Today through Wednesday)...Warm southwest flow aloft
will maintain warm air mass across the region. Should see another
great early summer day, with inland temperatures reaching back into
the lower to middle 80s. Solid marine clouds on the Oregon coast
from Lincoln City southward, with areas of low clouds forming to the
north. Suspect all of the coast will fill in with low clouds this am.
But, should see clouds burn back to within a mile or two of the
beaches by afternoon.
Weak upper level disturbance in the flow sits to our west. This
disturbance is not all that organized, and lacks a lot of moisture.
That said, will keep cloud cover down for today. But models still
indicate some weak instability over the Cascades later today into
this evening. Will likely see a few cumulus clouds form over the
Cascades this afternoon, and still a small chance one of those could
grow into a shower or thundershower. So, will maintain 20 pct PoP for
the Cascades, mainly along the crest.
This disturbance will have one major effect...to increasing the
onshore componet later today and tonight. So, marine clouds will
reform along the coast early this evening, and spread inland
overnight. While this will not be a strong marine push, inland areas
will feel the ocean air spilling inland this evening on gusty
northwesterly winds. Area of low clouds will push through the Coast
mtn gaps and up the Columbia River. While good part of the Willamette
Valley will stay rather free of marine clouds tonight, should see
plenty of low clouds Tue am, especially against the Cascades
foothills and north of Salem. The onshore flow will also give a few
deg of cooling for the interior, with highs 80 to 85.
High pressure offshore will dominate weather for Tue afternoon and
Wed, with light to moderate northwesterly flow. This will ensure Wed
will be similar to Tue, only with much less inland low clouds. Should
see temperatures warm up a few deg as a result. /rockey.
.LONG TERM...(Wed night through Sunday)...Long term period begins
with above normal temperatures tapering closer to normal by the
weekend as PacNW ridging is replaced by low amplitude troughing.
Despite our pattern shifting into one more dominated by a longwave
trough, majority of disturbances will remain north of our area which
will keep conditions mostly dry through the period. Depending on the
exact track of the disturbances, may need to add low chance POPS at a
later time, but given current data, see no reason to change course
from persistence dry forecast. /Bentley
.AVIATION...VFR conditions prevailing inland for the next 24
hours. At the coast expect low MVFR or lower conditions primarily
south of KTMK with some clearing this afternoon. KAST may see
several hours of low MVFR or lower conditions this morning between
12Z and 18Z. IFR conditions are likely to develop at the coast
this evening and slowly push inland overnight.
KPDX AND APPROACHES...VFR for the next 24 hours. However stratus
moving up the lower Columbia River will bring low MVFR or IFR
conditions to western approaches and possibly to KPDX near 12Z
.MARINE...High pressure over the waters combined with a thermal
low over northern California and the southern Oregon Coast is
maintaining northerly winds over the waters. Small craft
advisories for winds continue early today for the outer marine
zones. Winds ease a little today due to a weak disturbance that
moves across the area. The thermal trough strengthens again up
the coast Tuesday and Wednesday, strengthening the surface
pressure gradient to bring a return of northerly winds gusting to
25 to 30 kt. Winds near shore should ease during the late evening
and morning hours. Another weak disturbance weakens the surface
pressure gradient Thursday and Friday.
Seas currently around 4 to 6 ft today should build to 5 to 8 ft
Tuesday and Wednesday. Choppy conditions ease some today, but
potentially hazardous steep seas will likely return as the winds
increase again Tuesday and Wednesday. /mh
PZ...Small Craft Advisory for winds until 5 AM PDT early this
morning for Waters from Cape Shoalwater WA to Florence OR
from 10 to 60 nm.
Small Craft Advisory for hazardous seas until 5 AM PDT early
this morning for Waters from Cape Shoalwater WA to
Florence OR from 10 to 60 nm.
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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.