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fxus66 kpqr 260353 

Area forecast discussion
National Weather Service Portland or
851 PM PDT Thu may 25 2017

Synopsis...upper level high pressure builds over the region on
Friday, with dry and warmer conditions developing. High pressure
aloft will hold over the region through the Memorial Day Holiday
weekend, and afternoon temperatures will remain well above normal.
High pressure shifts eastward early next week ahead of the
next approaching disturbance. Temperatures trend gradually cooler
with a return of precipitation chances during the second half of next
week as a disturbance tracks across the Pacific northwest.


Short through has been a very pleasant late
Spring day across the cwa, with abundant afternoon sunshine and high
temps into the mid 70s over the interior lowlands and 60s at the
coast. The only weather of note has been some scattered showers over
the Cascades during the late afternoon and early evening hours,
which were associated with a low pres system centered near the or/Idaho
border. The circulation associated with the low is bringing north/NE
winds into the Cascades, so showers that formed along the crest were
drifting westward into our County Warning Area. We even detected a lightning strike
out of one of the showers to the north of Mt. Jefferson. Based on
the latest radar imagery, the showers have mostly ended at this
point, and the threat should be over by 06z. Other than some
scattered debris clouds from the dissipating showers, there is no
cloud cover over SW Washington and northwest Oregon this evening. Visible
satellite shows a marine stratus deck well offshore, and the current
trend is for the stratus to continue to clear from north to S. Based on
the current satellite trends and the fact that 850 mb flow will
become easterly overnight, decided to remove low clouds from the
fcst along the coast overnight into Fri am. There may be some patchy
stratus or flow along the central or coast south of konp, but think
that in general we will see clear skies overnight.

An upper level ridge currently well offshore will continue to
gradually shift eastward, with the ridge axis near the coast on
Friday and squarely over the Pacific northwest and Great Basin over
the weekend. With 500 mb heights rising steadily through the Holiday
weekend and 850 mb temperatures likewise warming, afternoon
temperatures will respond accordingly over the next few days. High
temperatures in the Willamette Valley will be in the lower 80s
Friday, and generally in the mid to upper 80s over the weekend.
However, models continue to suggest a weak surge of marine stratus
due to a southerly wind reversal along the coast on Friday night,
starting in south and pushing up to around Pacific City. This may
keep saturday's temperatures a little bit cooler along the southern
and central portions of the coast than the pattern might otherwise
suggest. Pyle/Cullen

Long term...Sunday night through Thursday. Little change to the
overall pattern for the Memorial Day Holiday, with the upper level
high pressure still squarely positioned over western U.S. And
temperature remaining well above seasonal normals. However, by Monday
night into Tuesday, heights begin to lower ahead of the next
approaching disturbance. Some discrepancies among the models with
respect to timing and strength of this feature, so for now have
trended the forecast in line with a blend of models for Tuesday and
Wednesday. For the second cycle, however, the deterministic GFS has
been very much on the cool end of the gefs ensemble spread with
respect to temperatures/heights. For this reason, have continued to
hold the temperature forecast a bit above the (deterministic)
consensus and have leaned towards the ensemble mean. Thus, confidence
in the forecast during the breakdown of the ridge is a bit lower than
average. Nonetheless, expect a cooling trend back to near or perhaps
slightly below normals for the start of June. Cullen


Aviation...VFR conditions for the entire area. Isolated showers
over the Cascades drifting toward the southwest are all but gone.
Some patchy low stratus may develop along the coast by morning
but not likely to affect kast or konp.

Kpdx and approaches...VFR through the period. /Mh


Marine...winds remain below Small Craft Advisory criteria but
there have been a few gusts near 20 kt over the central Oregon
coastal waters.

Seas have subsided a little in the 9 to 10 ft range and
continue 2 feet above guidance. With seas hovering around the 10
ft level with dominant period around 9 to 10 seconds have pushed
back the end time of the Small Craft Advisory through 3 am Fri.
Beyond tonight, winds and seas will remain benign until at least
the middle of next week. /Mh /Bentley


Pqr watches/warnings/advisories...
Pz...Small Craft Advisory for hazardous seas until 3 am PDT Friday
for coastal waters from Cape Shoalwater Washington to Florence or
out 60 nm.

Small Craft Advisory for rough Columbia River bar from 4 am to
8 am PDT Friday.



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