Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Medford or
845 am PDT Friday Apr 18 2014

Short term...the current forecast is on track. Expect today to be
dry with the next front well offshore and not expected to enter
the area until Saturday morning. Low clouds are lingering in most
inland west side valleys and into some east side locations. The
low clouds are expected to clear by around noon today. Updated the
forecast sky cover for these trends.

The next front will approach the area tonight as the parent low,
well to the north, moves into the Gulf of Alaska. The area will
see the tail end of this front. Model forecast mainly just show
light rain spreading into the coast...coastal mountains and Umpqua
basin and southern Oregon Cascades Saturday morning into Saturday
afternoon. Behind the front...large seas are expected over the
coastal marine waters and high surf conditions are expected along
the coast Saturday night into Sunday.


Aviation...based on 18/12z taf cycle...MVFR/IFR conditions have
become common in many of the valleys within the forecast area. Low
clouds and areas of fog will likely continue through the morning
until a few hours after sunrise...with all areas expected to clear to
VFR by roughly 17 UTC. For the rest of the day...VFR should prevail
over all areas. Tonight...middle to high level clouds will increase
ahead of an approaching frontal system...and winds will become gusty
along the coast. However...VFR conditions are expected through the
remainder of the taf period.


Marine...there will be a number of concerns over the next several
days...with the most prominent issue being that of heavy swell
entering the area this weekend. But first...high pressure will
briefly build over the waters today...and increasing northerly winds
will approach Small Craft Advisory levels in the outer waters south
of Cape Blanco. These conditions will be short-lived as a front
will then approach and pass over the coastal waters
Saturday...resulting in a period of southerly Small Craft Advisory
winds and choppy seas...mostly along and north of Cape Blanco. The
heavy long period westerly swell will develop Saturday night into
Sunday...then gradually diminish through the day Monday. This swell
could relocate crab gear...and will support heavy breakers over bars
and within the surf zone. Although winds will become relatively calm
through much of next week...seas will remain steep through at least
Wednesday morning. -Bpn/dw


Previous discussion... /issued 349 am PDT Friday Apr 18 2014/

Discussion...precipitation was widespread across the region on
Thursday as a cold front pushed through. The highest rain amounts
of .15-.25" fell across the higher terrain of the Umpqua and in
the Oregon Cascades. Snow levels remained above the passes.
Satellite early this morning shows significant upper level drying
behind the front with partial clearing. This should allow for
patchy morning fog development across the western valleys. High
pressure will build quickly back in across the area today with
high temperatures rebounding up to 10 degrees over Thursday for many
areas. However areas east will see a cooler day versus Thursday
by up to several degrees.

The next frontal system to impact the region is seen offshore
spreading clouds between 130 and 140w. The parent low with this
system is robust with the latest GFS indicating a surface low of
970mb lifting north through the Gulf of Alaska. After the
associated cold front spread rain across mainly the coast and
Umpqua Saturday...the swell generated from system is expected to
impact the southern Oregon coast Saturday night through Sunday.
Swells of 16 to 17 feet with breakers up to 24 feet in the surf
zone are expected. A high surf advisory remain in effect.

Another impact of the front will be increased westerly winds
across the east side Saturday afternoon. Fire weather interests
should be prepared for gusty conditions. The system quickly dries
out through Saturday night with high pressure likely providing dry
and mild weather again on Sunday. Then...yet another trough
arrives over the eastern Pacific Monday with south flow increasing
over the area. Precipitation looks likely at least by Monday night as
this deepening trough pushes inland. Gusty south winds will likely
impact the mountains and east as well.

Thereafter through middle to late week the longer range Euro and GFS
both indicate subtle ridging but continued rain chances here and
there in somewhat unsettled flow. Later...toward next weekend...
there appears to be some consensus on an interesting change in the
weather that looks quite cool and wet as the polar jet takes a dip
well south. This may result in a period of active and unusually
cool and wet weather to round out the month. Stay tuned. Stavish


Mfr watches/warnings/advisories...
or...high surf advisory from 11 PM Saturday to 11 am PDT Sunday for


Pacific coastal waters...high surf advisory from 11 PM Saturday to 11 am PDT Sunday for
Hazardous seas watch from Saturday evening through Sunday
morning for pzz350-356-370-376.