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Area forecast discussion 
National Weather Service Medford or
257 PM PDT Monday Oct 20 2014

Discussion...the front has now pushed east of the Cascades. A cool
pool aloft is already starting to move into the area and showers are
developing just west of Crescent City. A couple of lightning strikes
have been observed offshore and I would not be surprised if we see
more strikes late this afternoon through this evening as the cool
pool aloft reaches the coast. The models suggest the trough will
have a slight negative tilt as it moves inland this evening and at
the same time there may be enough instability for a few isolated
storms east of the Cascades this evening. Showers will continue
through at least the first half of the night, then will decrease
from west to east as the trough axis moves east of the forecast
area. Weak shortwave ridging builds into the area Tuesday and we'll
get a relative break in the weather. Still could not rule out a few
showers early in the morning, otherwise it will be dry. Temperatures
Tuesday could end up higher than what's in the forecast if there's
enough breaks in the cloud cover.

Next we turn our attention to the next front which could impact our
area with moderate to heavy precipitation and gusty winds. The
models are in better agreement compared to yesterday with the timing
of the front. Steady rain will start to move into the northwest part
of the forecast area Wednesday morning, then slowly move south
during the day. This front will have good iv transport aimed right
at the Coast Range. So it's no surprise the models put the heaviest
precipitation along the coast and Coast Range. It's a goo bet 1-2
inches or more will fall in this area Wednesday. Further south and
east, specifically in the Rogue Valley we may not get any measurable
rain for two reasons. First the front will be slow to move
southeast, second we'll have a downslope component. I did keep it
dry in the morning and put in a slight chance mention in the

The front will gradually move southeast Wednesday night and the
focus for moderate to heavy precipitation will shift south into the
South Coast range. Also, moderate precipitation will move into the
Rogue Valley. Rainfall amounts Wednesday night at the coast could
easily range between 2-4 inches and 0.25-0.50 of an inch in the
Rogue Valley. The front will continue to move south into northern
cal Thursday morning and the focus for the heaviest rainfall will be
in western Siskiyou County. We could see improvement Thursday
afternoon and night, at least in terms of rainfall rates with
precipitation expected to become light and intermittent.

Next we'll address the winds. Winds near Weed have decrease over the
last few hours and expect this trend to continue into this evening,
therefore we'll be canceling the Wind Advisory. Moderate to strong
winds are likely ahead of the front Wednesday and Wednesday evening,
especially east of the Cascades and they could reach advisory or
warning levels near and just east of Summer Lake Wednesday afternoon
through Thursday morning. Models show 700 mb winds increasing and
peaking out between 40-50 kts Wednesday night into Thursday morning.
Additionally winds will crank up in the Shasta Valley near Weed and
they are also likely to reach advisory criteria. The 700 mb winds
are more westerly, but the Medford to Redding gradient is sufficient
enough for gusty winds. -Petrucelli

Long term...Friday through Monday...a large upper trough will move
to around 130w on Friday, and a strong shortwave will round its base
causing the trough to become negatively tilted. Surface low pressure
is expected to form under the area of upper diffluence and move
north along the coast. This will drag the front from Thursday back
north as a warm front on Friday. While there are some model
differences regarding the specifics, this will likely bring rain to
much of the area, especially the west side and south facing mountain
ranges. In fact, deep, moist southwest flow remains aimed at the
Curry coast and mountains and western Siskiyou Mountains as the
front drops in Thursday, as it lifts back north as a warm front
Friday, and into the weekend. This could be a very big rain maker
for these areas as this moist flow is wrung out over the terrain.

The key question regarding the winds is the location and strength of
the surface low. There is at least some potential for strong winds
over the waters, coast, and mountains on Friday, but given the
uncertainty of the low position, we weren't't able to get specific
just yet. We did raise the probability of precipitation for Friday, however. This will need
to be watched closely for wind concerns.

The main trough axis moves inland Saturday with showers and lower
snow levels (around 6000 ft). A weak ridge builds in on Sunday with
lower chances for rain. The models all advertise another front early
next week, but differ on the strength. We've obviously turned a
corner into typical Fall weather, and this pattern looks like it has
some staying power which should help with our water issues. -Wright


Aviation...20/18z taf cycle...showers with brief MVFR ceilings and visible
will continue to affect all terminals through this evening.
Conditions will be VFR outside showers. There is a slight chance for
a thunderstorm over the areas through this evening as well, but the
threat is not high enough to include in any of the tafs. Showers
diminish tonight. There may be enough clearing for some valley fog
and low cloud with IFR ceilings/visible tonight and subsequent tafs will
address this. -Wright


Marine...updated 600 am PDT Monday 20 Oct 2014...a series of
disturbances will impact the marine waters over the next week.
As weak low pressure moves into the waters today, expect south winds
to increase to Small Craft Advisory levels. Also a high
and steep long period west swell is building into the waters this
morning and will peak this afternoon and evening with seas around
14-16 feet. A dominant period of 15 seconds is expected with seas
today but steep short period wind waves will mix with longer period
swell at times. Also over the waters today and into this evening,
expect showers along with a slight chance of thunderstorms.

Tonight, wind waves will decrease and westerly swell will gradually
lower. Steep seas above 10 feet are expected to continue tonight
through Tuesday though.

Then, the strongest front of the week is likely to approach Tuesday
night and Wednesday. Small Craft Advisory level winds are likely to
develop Tuesday afternoon and into the evening. Then wind may reach
gales along with heavy seas with moderate to heavy rain Tuesday
night into Wednesday evening. There is still some uncertainty on the
timing and strength of this system but overall, models are beginning
to show agreement that gales are possible from around Cape Blanco
northward with this event. South of Cape Blanco, winds approaching
gales are possible as well on Wednesday. Building west swell is also
forecast on Wednesday. Given the slow movement of the front as it
pushes into the coast Wednesday, along with high end small craft or
gale winds and building west swell, expect that much of the waters
will experience very steep and chaotic seas. Current forecasts show
seas reaching 15 to 17 feet Wednesday. /Cc


Mfr watches/warnings/advisories...

Pacific coastal waters...gale watch from Tuesday evening through Wednesday
evening for pzz356.
Small Craft Advisory for winds until 5 PM PDT this afternoon for
Small Craft Advisory for winds from 11 am to 11 PM PDT Tuesday
for pzz356.
Hazardous seas watch from Tuesday evening through Wednesday
evening for pzz356.
Small Craft Advisory for hazardous seas until 11 PM PDT Tuesday
for pzz350-356.
Gale watch from Tuesday afternoon through Wednesday evening for
Small Craft Advisory for winds from 9 am to 5 PM PDT Tuesday for
Hazardous seas watch from Tuesday afternoon through Wednesday
evening for pzz376.
Small Craft Advisory for hazardous seas until 5 PM PDT Tuesday
for pzz370-376.
Gale watch from Tuesday afternoon through Wednesday afternoon
for pzz370.
Small Craft Advisory for winds until 11 PM PDT this evening for
Small Craft Advisory for winds from 9 am to 5 PM PDT Tuesday for
Hazardous seas watch from Tuesday afternoon through Wednesday
afternoon for pzz370.
Gale watch from Tuesday evening through Wednesday afternoon for
Small Craft Advisory for winds from 11 am to 11 PM PDT Tuesday
for pzz350.
Hazardous seas watch from Tuesday evening through Wednesday
afternoon for pzz350.


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