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fxus66 kmfr 272100 

Area forecast discussion
National Weather Service Medford or
200 PM PDT Mon Mar 27 2017

Discussion...27/12z NAM/GFS/ec in.

The northern hemispheric projection shows a wave number of four
around the Globe and occasionally hints at a five over the next
several days. This argues for a moderately progressive pattern.
That is indeed what we will get over the next several days.
Overall the pattern looks quite Spring like...with weaker storms
driven by low amplitude upper level troughs. The primary storm
track will remain to the north of the area...but there will be
some action down here.

A long wave trough has moved out to the east and a long wave ridge
is now building into the West Coast. Shower activity is
diminishing and the heaviest activity is occurring from the
Cascades east.

The ridge will bring dry and warmer weather to the area Monday
night into Tuesday. The ridge axis will break to the east of the
area Tuesday night and a strong short wave riding up the back side
of the ridge will move onshore to the north of the area
Wednesday. A warm front will move onshore Tuesday night...followed
by a trailing cold front Wednesday afternoon. With most of the
upper level support remaining to the north...both fronts will be
relatively weak this far south. Even so...most if not all of the
Medford County Warning Area will get some light precipitation Tuesday night into
Wednesday night. A stronger short wave with a more southerly
trajectory will move onshore late Wednesday night or early
Thursday morning with the long wave trough. This along with short
waves diving down the back side of the trough will support Post-
frontal showers lasting into Thursday evening...but shower
intensity and coverage will diminish through the day Thursday.

After that...another long wave ridge will build into the West
Coast and this will bring another round of dry and warmer weather
beginning Friday.

Long term...Friday through Monday.

After a chilly morning, high pressure ridge is likely to bring a
warming and drying trend Friday into Saturday with the storm track
pushed northward into Canada. Model uncertainly continues to be high
for next weekend with the European model (ecmwf) being quicker to push the ridge east
and allow a trough to move into Washington and northern Oregon. We have
introduced a slight chance of rain for Coos and northwest Douglas County
for Saturday but confidence is not very high as the GFS continues to
maintain the ridge over our forecast area. Ensemble forecast high
temperature for SW Oregon points to a warm day so we are leaning
toward no mention of precipitation for the Rogue Valley. Confidence
is only slightly higher for precipitation Saturday night into Sunday
as the driest solution (ec) shows westerly flow instead of a ridge,
with a deep trough per the GFS. The GFS solution bears watching as
it develops a closed low near the Tahoe area. This would bring more
mountain snow to the Warners early next week. /Fb


Aviation...27/18z taf cycle...showers are decreasing across the
forecast area to mainly isolated coverage, and the trend for
decreasing coverage into the afternoon. VFR ceilings are expected to be
the predominate condition today. Could not rule out temporary MVFR
or even isolated IFR ceilings in snow showers with partial mountain
obscurations. Freezing levels are expected to rise to around 5000
feet mean sea level this afternoon. Confidence is higher for VFR conditions
this afternoon through this evening as the atmosphere becomes more
stable. For now kept VFR ceilings in tonight, but later shifts may need
to evaluate the potential for low clouds and patchy fog for west
side valleys if there's enough clearing. /Fb


Marine...updated 200 PM PDT Monday 27 March 2017...with high
pressure building into the waters, winds have diminished but seas
will be at a peak this evening. Seas will be very steep in the outer
waters and steep in the inner waters. Seas are dominated by a west
swell at 12 seconds and another west swell at 18 seconds. Seas
diminish very slightly on Tuesday and remain high through Wednesday
night. An occluding front will then bring increasing southerly winds
Tuesday night into Wednesday morning with speeds reaching advisory
strength north of Cape Blanco beyond 8 nm from shore. Winds will veer
to north Wednesday night then may reach advisory strength in the
outer waters south of Gold Beach Thursday afternoon into Saturday.
Uncertainty in the forecast increases rapidly on Saturday and is high
into early next week. /Dw


Mfr watches/warnings/advisories...


Pacific coastal waters...Small Craft Advisory for hazardous seas
until 5 am PDT Thursday for pzz350-356-370-376.
Small Craft Advisory from 11 PM Tuesday to 1 PM PDT Wednesday
for pzz350-370.
Hazardous seas warning until 11 PM PDT this evening for

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