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Area forecast discussion 
National Weather Service Medford or
354 am PST Thursday Feb 11 2016

Updated aviation and marine sections

Short term...a shortwave riding up through the southwest flow
aloft has kicked off a few showers over our area this morning. No
rain has hit any of the observing sites yet, but radar shows
isolated showers drifting through right now. Shower coverage will
increase this morning as the main part of the shortwave arrives,
and radar is showing a lot more showers off the northwest California
coast moving our way. Models show these showers being confined
mostly to the Cascade crest and west side, but some showers
certainly could drift over onto the east side. Probability of precipitation have been
raised this morning.

We will probably see at least some lingering showers this
afternoon and evening as a weak cold front approaches. This cold
front will move onshore tonight and Friday morning and bring light
rain to most west side locations as it moves inland Friday. We're
not expecting a lot of rain with valley locations probably only
seeing a few hundredths of rain. However, mountain locations could
see up to a quarter of an inch of rain. Snow levels will be high
(above 8000 feet most of the day), so it will be rain except at
the highest peaks. Snow may make it down to Crater Lake and Montana
Ashland by day's end, but most of the precipitation will have
already fallen by then. Probability of precipitation were raised to at least likely on the
west side for Friday.

Saturday should be a bit of a break with leftover morning showers
over the north decreasing through the day. Elsewhere, the day
ought to be dry. The previous shift's thinking regarding sunday's
system still looks reasonable and the previous long term
discussion follows. The one change made to the extended forecast
this morning was to raise probability of precipitation on Sunday. -Wright

Long term...Sunday through Wednesday...a warm front with good
isentropic ascent will ride over the top of a Flat Ridge on
Sunday. This combined with deep onshore west-northwest flow will
result in rain, focused on north and west facing terrain along
and west of the Cascades with lighter rain in the valleys. Rain
chances diminish south and east of the mountains. Snow levels will
be well above the major passes and likely above 8000 feet in most
areas. The warm front will shift northward in the afternoon and
isentropic lift will ease...effectively shutting off rainfall
from south to north across the County Warning Area late Sunday afternoon and
night.

Models indicate the ridge will strengthen a bit over the area
Monday with most, if not all precipitation remaining to the
north of the County Warning Area. Models differ a bit with respect to another
shortwave riding over the ridge Monday night into Tuesday. The GFS
keeps it way to the north where it would have no impact on our
weather. The European model (ecmwf) though has it farther south. Due to the
uncertainty, we have indicated slight chance to chance probability of precipitation from
the coast to the Cascades and north of the Umpqua Divide. It
should stay dry in the Rogue Valley.

Confidence is fairly high that the next significant upper trough
to impact the area will arrive Tuesday night into Wednesday. The
surface cold front will be just offshore late Tuesday night, then
move across the area Wednesday into Wednesday night. Rain is
likely from the coast to the Cascades with high chances even over
the east side. Snow levels start out high ahead of the front, but
could drop down to 3000 feet behind the front by Thursday morning.
-Spilde

&&

Aviation...for the 11/12z taf cycle... VFR conditions are expected
to prevail across the valleys and primary airfields through the taf
period. A warm front moving through this morning into early
afternoon will result in some light shower activity. Expect some
partial terrain obscurations this morning into the early afternoon
mainly from the Cascades westward, and greatest over the Coast
Range. A brief period of MVFR is possible along the coast late this
morning through early afternoon. Btl

&&

Marine...updated 305 am PST Thursday Feb 11 2016...long period west
swell will build today through Friday and then persist through
Saturday. A warm front will move through today followed by
increasing south winds ahead of a cold front tonight.
This cold front will move through late tonight through Friday
morning. After a break on Friday and most of Saturday another front
will move through Saturday night into Sunday. High pressure is then
likely to rebuild along the West Coast early next week before a
stronger front arrives Wednesday through Thursday. Btl

&&

Mfr watches/warnings/advisories...
or...
California...none.

Pacific coastal waters...
- Small Craft Advisory for hazardous seas until 10 PM PST Sunday for
pzz350-356-370-376.
- Small Craft Advisory from 10 PM this evening to 4 am PST Friday
for pzz370-350.

$$

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