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Area forecast discussion 
National Weather Service Portland or
833 am PST Tuesday Mar 3 2015

Synopsis...high pressure will dominate this week and maintain a dry
weather pattern. Weak offshore low-level flow will diminish this
afternoon. It will be cold again tonight...especially in the interior
valleys. Daytime temperatures will gradually warm each day later in
the week and over the weekend.
&&

Short term...today through Thursday night...current forecast on
track with minimal changes needed for the short term. Water vapor
loop shows a high-amplitude ridge centered just inside 140w...a
cut-off low near Baja California and an upper trough extending over the northern
rockies into the Great Basin area. Also of note is a very weak
disturbance moving down the back side of the ridge near the Washington and
Oregon coast. Very cold start to the day with many areas at or below
freezing.

Although there will be more sun today...model 850 mb temperatures warm ever
so slightly today so values close to persistence look good. The
kttd-kdls gradient was at -2 mb as of 16z...not enough to produce
east wind at kttd just yet. Latest NAM shows the offshore gradient
gradually weakening this afternoon. Should just see patchy fog
tonight at best in the interior valleys. Min temperatures tonight will be
similar to this morning...although slopes and ridges will warm just a
bit as shallow inversions develop.

NAM shows another verly weak upper-level disturbance moving acorss
the area late tonight and Wednesday morning for some high clouds. Other
than that...850 mb temperatures slowly warm Wednesday and Thursday. The upper ridge
will flatten Thursday as an upper trough moves inland north of
Washington. There may be some cirrus with this feature...but will
otherwise have little impact to the weather. NAM suggests that there
will be a wind reversal along the coast Thursday night and there may
be an increase of coastal clouds. Weishaar

Long term...and the ridge continues. European model (ecmwf) actually shows the ridge
amplifying Friday as a short-wave drops through the northern rockies. 850 mb
temperatures warm a bit more Friday...which should be enough to produce maximum
temperatures in the lower 60s for a good portion of the southern two-thirds of
the forecast area. Upper ridge axis pushes a bit closer to the coast
Sat for a little more warming. European model (ecmwf) would suggest a little low-level
offshore flow Friday night and Sat. Little change sun. The latest GFS
has gone dry for Monday...more in line with the 00z European model (ecmwf). The gefs and
naefs mean charts valid 00z Monday suggest the ridge axis will shift
east of the Cascades. GFS and European model (ecmwf) show a more progressive pattern
developing around the middle of next week...with a fairly substantial
system moving into the area around next Thursday. Weishaar
&&

Aviation...dry and stable northerly flow aloft continues today
with variable thin high clouds. Few pockets of local fog continue
for a brief time...but these should clear by 18z. Locations that
saw fog develop early this morning may see a repeat again late
tonight...with the best chances around kkls and also the south
Willamette Valley including keug.

Kpdx and approaches...VFR under dry stable northwest flow aloft.

&&

Marine...high pressure remains firmly in control over the region
through much of the week. Surface pressure gradients remain fairly
weak which will keep light northerly winds below 15 knots for the
next several days. Models suggest a southerly wind reversal may
work up the coast late in the week. Seas currently 4 to 6 feet over
the waters...highest over the northern outer waters...and will
hold at this level through the next several days. Cullen



&&

Pqr watches/warnings/advisories...
or...none.
Washington...none.
Pz...none.
&&

$$

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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.

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