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Area forecast discussion 
National Weather Service Medford or
919 am PDT Thursday Oct 30 2014

Discussion...updates this morning included bumping up sky cover in
west side valleys for fog and adjusting probability of precipitation for the expected
slower arrival time of the front today. Visible satellite shows
valley fog in most side locations with middle and high clouds
covering most of the forecast area. The next system due in is
currently inside of 130w. This front is expected to become oriented
in more of a north-south direction and this will slow the
progression of the front. Expect rain to begin at the coast by this
afternoon and then spreading inland later this evening. Winds are
expected to be fairly light compared to previous systems. Winds will
still be breezy on the east side and Shasta Valley, but nothing
like we saw with the previous system. Today's focus for the
afternoon package will be timing of precipitation for today and for
tomorrow's trick-or-treating activities, as well as snow levels
and temperatures for the upper trough passage Friday into
Saturday. For more details see the previous discussion below.

&&

Aviation..for the 30/12z taf cycle...widespread IFR ceilings have
formed across SW Oregon valleys with local IFR visible in the Klamath
basin. IFR ceilings will decrease in coverage but remaining widespread
through the morning hours. A cold front will spread rain inland and
this will help to break up the low clouds with ceilings improving to
MVFR by noon across SW Oregon. Elsewhere mountains will be obscured
with local MVFR ceilings. Visible could drop to MVFR in areas of rain. /Fb.

&&

Marine...updated 230 am PDT Thursday Oct 2014...a cold front will
move towards the waters this morning. South winds will increase
ahead of it to low end small craft. The area of concern is very
small and fall mainly between 9-20nm offshore and only down to off
Cape Blanco. The front will move inland tonight with weak low
pressure moving into the waters Friday. High pressure then builds
southwest of the waters Saturday. The models are fairly consistent
showing increasing long period swell Friday night, but it won't last
long with swell heights decreasing on Saturday. West to northwest
swell is expected to increase again early next week. /Fb

&&

Previous discussion... /issued 321 am PDT Thursday Oct 30 2014/

Discussion...models continue to be in very good agreement
concerning the overall pattern for the next several days, and with
each run,. The details are becoming a little more clear. Overall,
there is higher than average confidence in a continuing wet
pattern for our area, with the coldest temperatures so far this
season expected to arrive over the weekend.

A warm front will slowly lift north of the area through this morning,
producing some light showers along the coast and into the Umpqua
basin. But lurking offshore will be the next cold front , due to
arrive this afternoon along the coast, then push inland through the
evening and overnight. Although the front does have significantly
colder air behind it, and lots of moisture inflow along it, there is
not much of a concern for gusty winds with it. This is mostly due to
the north/south orientation of the front, and the fact that as it
pushes inland, there will be very little pressure gradient between
it and a broad area of lower surface pressure over Oregon and
northern California. This is not to say it will not be breezy in many
places, including the coast, the Shasta Valley, and the east side,
just that strong winds like the ones we have seen with several
previous systems will most likely not materialize.

Precipitation will most certainly make an appearance for most, if
not all, of the forecast area. The system will carry with it a good
deal of moisture originating from the subtropical Pacific. 1 to 2
inches of rain or more are possible along the coast and the coastal
range as well as the Cascades, while a quarter inch to one inch is
likely for pretty much the rest of the area. The bulk of the
moisture will fall as the front itself pushes through, however, with
increasing instability behind the front, showers will develop and
continue to drop precipitation through Friday and into Saturday.
Instability may even be strong enough to produce a rumble of thunder
or two west of the Cascades. Snow levels will also lower
significantly Friday into Saturday, dropping to below 5000 feet
while the showers are ongoing. This will allow snow to fall along
the peaks and the higher passes, as well as some of the higher
elevations of the east side. While snow amounts will be light, roads
over higher elevations may become slick in heavier precipitation.
Showers will gradually come to an end by Saturday afternoon as high
pressure builds in.

Expect much cooler temperatures over the weekend, in fact, some of
the coldest temperatures seen in our area since last Spring are
possible Saturday and Sunday morning. Although too far out for
certainty at this time, frost or maybe even freeze headlines may be
needed for many portions of the west side, including the Shasta,
Scott, rogue, and Illinois valleys.

Sunday and beyond, uncertainty increases, but not because the models
are in any significant amount of disagreement. Although ridging and
high pressure will likely control the bulk of our area, we will lie
just along the periphery of strong southwest flow just to the north.
Some weaker systems may attempt to push through this flow, and the
northern half of the forecast area could see some light
precipitation as the tail of these systems pass through. The largest
of these is expected on Tuesday, and may be strong enough to be a
decent rainmaker for the Cascades and points west. The next more
potent weather maker is not expected until middle to late next week,
and this one has the potential to be a significant wind and rain
producer.

Temperatures through the long term will warm from the cold weekend,
mostly due to the southerly low level flow and the ridging overhead,
but daytime highs will still have some difficulty rising very much
higher than seasonal normals, with daytime highs in west side
valleys barely making it into the low 60s, and the east side firmly
entrenched in the 50s. -Bpn

&&

Mfr watches/warnings/advisories...
or...Small Craft Advisory for hazardous seas until 8 PM PDT this
evening for orz021.

California...none.

Pacific coastal waters...Small Craft Advisory for hazardous seas until
8 PM PDT this evening for pzz350-356-370-376.
Small Craft Advisory for winds until 8 PM PDT this evening for
pzz350-356-370-376.

$$

Mnd/btl/fjb

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