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fxus66 kpqr 180335 aaa 

Area forecast discussion...updated
National service Portland or
835 PM PDT Sat Aug 17 2019

Updated aviation discussion

Synopsis...after today's marine push of cooler air and partly to
mostly cloudy conditions, temperatures will warm slowly but steadily
through Tuesday. A weakening cool front will approach the coast
Wednesday afternoon, bringing increasing clouds, cooler air, and a
slight chance of showers Wednesday night or early Thursday. The end
of the week looks dry, with morning clouds and daytime temperatures
near normal.


Short term...tonight through Wednesday...a fairly uneventful pattern
for the next several days in terms of sensible weather. The Rex block
over the Pacific begins to break down, with the upper high over the
Aleutian Islands and Bering Sea retrograding, and the persistent
Upper Cutoff around 42n/160w moving slowly eastward. This cutoff is
eventually entrained by an upper trough dropping southward over the
Gulf of Alaska. Heights build over the pacnw in advance of this
system, with temperatures peaking on Tuesday several degrees above
normal. As the aforementioned upper trough and its surface low move
into the central British Columbia coast Wednesday, a decaying cold front will drag
across the pacnw late Wednesday or Wednesday night. At 18z
Wednesday, ensemble mean ivt is a not-too-shabby (for august) 350-
400 kg/M/S over the eastern Pacific as the front approaches the
or/Washington coast, but ivt quickly diminishes as low-level southerly flow
collapses in the 6-12 hours thereafter. There could be enough
lingering moisture and ascent for a slight chance of light
precipitation across southwest Washington and far northwest or, particularly
along the coast. Precipitation certainty aside, there is high
confidence of a moderate marine intrusion and seasonably cooler
airmass arriving by Wednesday evening. Bright

Long term...Wednesday night through Saturday...following the passage
of the decaying cold front Wednesday night, onshore flow persists
through the end of the week. With the break down of the Pacific
block, westerly flow with embedded progressive shortwaves will bring
a seasonable August weather scenario for the end of the week. The
timing of individual shortwaves will augment the morning
cloud/afternoon clearing regime, but ensemble mean heights are high
enough that precipitation appears unlikely Thursday through
Saturday. Bright


Aviation...clouds are trying to break up across our northern
interior counties, but skies remain broken north of mmv and uao.
With the sun setting, expect cloud cover to start to redevelop
overnight, with MVFR cigs for at least a portion of the night
inland, and widespread MVFR cigs along the coast. Everywhere
should see MVFR cigs sometime between 09z-15z. Eug may be the
only exception, staying VFR through Sunday. MVFR cigs around
2500-3000 ft should lift to 3500-4500 ft between 18z-21z at most
if not all terminals, and start to clear out. Expect greater
clearing on Sunday afternoon as northwesterly flow starts to

Kpdx and approaches...broken VFR cigs will likely persist,
solidifying again later this evening and sinking to 2500-3000 ft
by 12-13z Sunday morning. Cigs should lift again to 3500-4000 ft
by 18z, and probably will clear out by 22z. -McCoy


Marine...high pressure remains in place well offshore as thermal
low pressure persists over northwestern California and
southwestern Oregon. The surface pressure gradient isn't
particularly strong and will maintain winds closer to 15 kt over
most of the waters, though a few gusts to 20 kt possible over the
southern and outer portions of the coastal waters.. meanwhile,
seas holding around 6-7 feet, with a mix of a larger 8 second
and smaller 15 second swell.

Little change to the overall pattern through the start of next
week. A front will move near the waters early next week,
bringing south winds to the waters Tuesday and Wednesday. Cullen


Pqr watches/warnings/advisories...



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