FXUS66 KMFR 162316 CCA
Area Forecast Discussion...CORRECTED
National Weather Service Medford OR
415 PM PDT Wed Oct 16 2019
Updated Aviation Discussion.
.SHORT TERM...Tonight through Saturday night...A frontal system
is bringing rain to areas west of the Cascades this afternoon.
Winds are gusty ahead of this front, peaking near 40 mph in the
Shasta Valley at Weed and over higher terrain east of the
Cascades. Rain will spread over the entire forecast area
overnight. Showers will diminish Thursday morning but a cooler air
mass will keep temperatures Thursday afternoon about 10 degrees
High surf will impact the coast Thursday through Thursday evening
and a High Surf Advisory continues for that area.
A weak disturbance arrives late Thursday into Thursday night and
will bring another chance of rain for most areas from the Cascades
and west, but we it doen't look like much in the way of
precipitation amounts. The main system arrives Friday night and
Saturday, and this will bring significant rainfall and high mountain
snow to the forecast area. Strong westerly flow will favor the
Cascades and other north to south oriented mountain ranges for
enhanced precipitation. Moderate to heavy rain will reach the coast
Friday night and quickly spread to the Cascades and eastward late
Friday night and Saturday morning. One model does suggest a lot of
downsloping and drying in the Rogue Valley and severely limits the
amount of rainfall with the Saturday system, but we are favoring the
other models because generally there is less downsloping with
westerly flow systems than southwesterly. We expect total
precipitation Friday night through Saturday evening to reach 1-1.5
inches at the coast and in the Cascades (heaviest north of Lake of
the Woods), 0.5 to 1 inch in West Side Valleys and Siskiyou County,
and 0.5 to 1 inch east of the cascades.
Snow levels will lower behind the Saturday front, and we expect a
period of snow to impact Diamond Lake (down to around 5000 feet)
Saturday afternoon as colder air arrives. Latest data suggests
several inches of snow are possible there, but more snow is expected
above 6000 feet near Crater Lake. We're forecasting about a foot
of snow at Crater Lake from Friday night through Saturday evening.
Another component of the Saturday system will be moderate to
strong winds. GEFS ensemble mean suggests 57kt of wind at 10000
feet, and this typically results in wind advisory type criteria
being met east of the Cascades. Straight westerly flow is not
favorable for really strong winds at locations like Summer Lake,
but we do expect gusts to 45 mph in areas east of the Cascades,
and we'll be considering Wind Advisories for portions of the
forecast area on Saturday.
.LONG TERM...Sunday through Wednesday Night...The wet and cool
pattern will continue through Sunday night as a warm front pushes
through the region. Snow levels will begin Sunday morning at around
5000 feet, but will quickly rise through the day to well over 8000
feet. The front itself will pass to the north, but then stall out
across the center of Oregon. Meanwhile, the upper level flow will
split the region, with swift onshore flow to the north and drier
ridging to the south. The result will be a slight ongoing chance for
showers, mainly across Douglas County and into the Cascades, but
most other areas should remain dry and warmer through Tuesday
morning. The boundary is expected to move back south later Tuesday
as a weak cold front, and showers are possible, but details of any
resulting precipitation remains uncertain. -BPN
.AVIATION...For the 16/18Z TAFs...From the Cascades
west...A front is bringing areas of MVFR cigs and local IFR in rain
to the coastal waters and coast with areas of higher terrain
obscured. Widespread MVFR conditions, local IFR cigs/vis, and
widespread mountain obscurations are expected to develop from the
Cascades west this evening through tonight. Rain will decrease late
tonight and early Thursday morning, but expect continued areas of
MVFR/IFR Thursday morning from the Cascades west.
East of the Cascades...VFR conditions will persist this afternoon
then areas of MVFR cigs will develop with rain this evening through
Thursday morning. -CC
.MARINE...Updated 300 PM PDT Wednesday 16 October 2019...The first
in a series of fronts is moving through the waters this afternoon,
producing gusty south winds and steep to very steep seas. Winds will
be strongest from Cape Blanco north and beyond 2 nm from shore.
Isolated areas of Gales are possible. The greater threat will be
very steep seas, thus a Hazardous Seas Warning remains in effect.
Winds will ease this evening but building west swell will bring
small craft advisory conditions to all of the waters through
High and long period west to northwest swell will build into the
coastal waters tonight through Thursday evening. Seas are expected
to become a mix of steep to very steep by Thursday morning, peaking
out between 16 and 19 feet at 16 seconds Thursday into Thursday
evening before gradually diminishing late Thursday night into
Friday. A Hazardous Seas Watch remains in effect for this event as
does a High Surf Advisory, and bar crossing will become hazardous.
For details on all the hazards, please see MWWMFR and CFWMFR.
Small craft advisory conditions are expected Friday. Another strong
front follows on Saturday with strong winds and steep to very steep
seas possible. -CC
OR...High Surf Advisory from 8 AM Thursday to 2 AM PDT Friday for
Red Flag Warning until 7 PM PDT this evening for ORZ624-625.
Pacific Coastal Waters...Small Craft Advisory until 2 AM PDT Friday for
Hazardous Seas Watch from Thursday morning through late Thursday
night for PZZ350-356-370-376.
Hazardous Seas Warning until 5 PM PDT this afternoon for
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