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Area forecast discussion 
National Weather Service Medford or
244 PM PST Monday Nov 24 2014

Discussion...a rather quiet pattern is ahead for the next few days over the
forecast area. The models continue to show warm frontal precipitation
into the area tonight, but I find is suspect for the following
reasons. First, the satellite image is not that impressive second,
there have been no reports of precipitation. Third, the radar has yet
to show any returns. At the same time, 500 mb heights are rising and
will continue to increase tonight and gut feeling is that most of
the precipitation will get directed north of the forecast area. I
have decreased probability of precipitation and quantitative precipitation forecast amounts for tonight, but they may need
to be adjusted down further if the warm frontal precipitation does
not materialize.

The ridge will ampifly over the area Tuesday and Wednesday with the
storm track remaining well to our north. However the atmosphere will
be stable and we could have a subsidence inversion resulting in low
clouds and fog for most, if not all of the Westside valleys. This
could be of concern for anyone planing on traveling out of Medford
on Wednesday for the Thanksgiving Holiday. It's possible that low
clouds and fog could linger for most of the day Wednesday and not
break out until late in the day.

The ridge will begin to flatten out Thanksgiving day and this will
be the beginning of a pattern change. The models show a front
approaching the coast Thursday morning, then slowly move inland
during the day. Based on current timing, most of the precipitation
will remain west of the Cascades. The front is expected to remain
nearly stationary Thursday night and the focus for heaviest
precipitation will be along the Coast Range and coastal mountains.

Long term...Friday through Monday...confidence is high that a mean
trough axis currently near 160w will move to near the U.S. West
Coast late this week and remain in place through early next week.
This will open the door to wet weather over the Pacific northwest
during the period. Confidence is little lower in the details of
specific systems within this mean trough, but a shift in the overall
pattern later this week looks imminent.

The initial frontal system will slowly move through our region on
Friday. Snow levels will be Above All major passes on Friday which
should preclude any travel impacts from snow. It will probably be
wet for those traveling on Friday, especially from the Cascades west
(including all major passes), so take that into account when making
plans. The flow aloft backs to the southwest on Saturday as another
system drops into the mean trough. This should keep precipitation
going over the mountains and much of the west side, but snow levels
are expected to remain above pass level.

On Sunday, the next system drops in along the coast with a closed
upper low taking up a position around Cape Mendocino. Both the GFS
and ec are in rather good agreement about this and show the first
real southerly flow precipitation event of the season through the
Sacramento Valley and into the Shasta area. While i've kept probability of precipitation
high for much of our area, the heaviest precipitation will be in the
northern California mountains if this scenario pans out. At this
time, the situation is not ideal for a snow event along I-5 around
Montana. Shasta city, but it is something to watch. 850 mb temperatures
are too high and the flow is not aligned as well as we'd like to see
to get snow down to the Interstate. However, given that this will be
a heavy travel day, I did put in a rain/snow mix over the Shasta
area for Sunday.

Snow levels do finally fall to pass levels early next week as the
mean trough axis moves inland. The heaviest precipitation will be
gone at that time, so major impacts are not expected, but there
certainly could be some slippery travel in the mountains early next
week. -Wright


Aviation...based on the 24/18z taf cycle...VFR conditions are
expected over the area through this evening. There may be a little
light rain along the north coast and Umpqua this evening, but
conditions should remain MVFR or better. IFR/LIFR ceilings in fog/low
cloud will be possible in west side valleys again tonight.
Elsewhere, VFR conditions will prevail tonight. -Wright


Marine...updated 230 PM PST Monday Nov 24 2014...a weak front moves
inland this afternoon with seas and winds diminishing late this
afternoon into the evening. West swell continues to diminish with
generally light winds until Thursday when a stronger front increases
southerly winds. This will combine with increased west swell to
bring a chaotic mix of increasing southerly wind waves and west
swell for the tail end of the week. However...the period on the
westerly swell for the crab season pre-soak period looks to start at
around 13 seconds and remains in that range into the weekend. Sven


Mfr watches/warnings/advisories...


Pacific coastal waters...Small Craft Advisory for winds until 7 PM PST this evening for
Small Craft Advisory for hazardous seas until 10 PM PST this
evening for pzz350-356-370-376.


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