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Area forecast discussion 
National Weather Service Medford or
420 am PST sun Nov 23 2014

Updated aviation and marine discussions

several snotels north of Highway 140 from Fourmile Lake north to
Summit Lake reliably indicate between 3 and 6 inches of new snow
accumulated in the last 24 hours between 5000 foot and 6200 foot
elevations. We expect to have a new report from Crater Lake
National Park later this morning, which may have received a little
more than tehse mentioned snotels. Further south, from Lake of
The Woods to Mount Ashland, snow reports above 5000 feet were 1 to
3 inches.

This morning a 100 to 130 knots jet stream is still present over
the forecast area at 30,000 feet mean sea level. This jet is streaming high
clouds across the area, with lower clouds and some fog below at
many locations. We expect that these clouds will continue across
the forecast area through much of the day as the jet stream
remains nearly stationary, and actually strengthens some to
120-145 knots.

Today and then more so tonight through Tuesday there substantial
disagreement amongst the models as to how much precipitation will
fall across the area and where it will fall. The hrrr is
indicating precipitation along the coast and Coast Range today.
The NAM and sref models show widespread light precipitation
beginning this evening and continuing through Tuesday affecting
nearly all of the forecast area, at times, whereas the GFS and
European model (ecmwf) show lesser amounts and keep it more in the Cascades, Umpqua
basin, and the Oregon Cascades. This pattern is a favorable one
for light overrunning precipitation. We often term it a 'high
precipitation probability, but low qpf' type of event when this
pattern occurs. However, given model differences, while probability of precipitation have
been increased, they may need to be increased a bit more,
especially in the higher confidence areas mentioned. It is notable
that the 06z GFS has trended more toward the nam12 and sref and
the the 06z nam12 stuck to the same solution as was depicted on
the 00z run. This lends increasing confidence in the wetter nam12
and sref solutions. With this light precipitation, snow levels
will be of some concern, though it appears that the overrunning is
weak enough that we should be looking at rain and snow rather than
any freezing rain.

Sunday through Wednesday temperatures will be warming
significantly aloft. In fact, they warm to above freezing to about
the 11,000 foot level. Low dewpoints should help to protect the
snow pack from too much loss, but it will still be very notably
warm. Due to generally light winds, have undercut model
temperatures guidance for highs at Interior Valley locations for
this time period.

It does still look like a return to wet weather this upcoming
weekend. Details are still to be determined, but snow levels
look as if they are most likely to be on the high side with that
frontal system. It currently appears these snow levels will
remain above the primary mountain passes through next weekend. Btl


Aviation...based on the 23/12z taf cycle...low level moisture
combined with high clouds and weak stability is bringing a mix of
low clouds and fog in inland valleys this morning. Expect IFR/LIFR
ceilings/fog in the valleys west of the southern Oregon Cascades,
including kmfr and krbg and possibly in northern California this
morning. East side areas will have a mix of VFR and MVFR ceilings this
morning. Along the coast, expect mainly VFR conditions with local
MVFR ceilings. Conditions are expected to improve to VFR this afternoon
and continue into this evening. Then overnight, expect areas of
valley IFR ceilings in patchy fog to develop for areas west of the
Cascades. /Cc


Marine...updated 4am PST Sat Nov 22 2014... steep west swell will
persist today into Monday, then slowly diminish Monday evening and
Tuesday. A warm front will lift northward through the waters Sunday
night and Monday. Winds are expected to be mainly light and
southerly around 10 to 20 knots on Monday. Although at least one model
shows 25 knots Small Craft Advisory winds possible Monday into Monday
evening. Weak high pressure is expected Tuesday into Wednesday.
Then a couple frontal systems will move into the waters Wednesday
night through Friday, bringing an increase in south winds and seas.


Mfr watches/warnings/advisories...


Pacific coastal waters...
- Small Craft Advisory for hazardous seas until 4 PM PST Monday
for pzz350-356-370-376.



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