Small Craft Advisory 62, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
1050 PM PDT Tue Jun 20 2017

Updated AVIATION Section

.DISCUSSION...Minor update this evening to remove the thunder
chances over the SE portion of the forecast area. Only had a few
isolated showers in SE Modoc County and these are in the process
of dissipating or have already dissipated. Marine stratus is
still holding strong over the coastal waters and along the
Coos/Douglas Coasts this evening. Models are indicating some
deepening of the marine layer overnight into Wednesday morning
with rising ceilings and some clouds moving inland across southern
Coos County and banking up against the Umpqua Divide. The hi
resolution guidance is even spitting out a couple of hundredths
from southern Coos into southern Douglas County overnight, so have
added slight chance POPs in those areas. However, by 15z (8am
PDT) Wednesday morning, increasing northeast winds will scour the
clouds quickly and most areas should turn out sunny. Most areas
will also be a touch cooler Wednesday, but perhaps more notably
will be the lowering of dew points and afternoon humidity across
the area. It should feel less humid than it has the last few days.
-Spilde

&&

.AVIATION...21/06Z TAF CYCLE...A deepening marine layer will cause
rising ceilings along the north coast and at KOTH overnight, but
they probably remain MVFR until the early morning hours. Ceilings
will also bank up against the Umpqua Divide overnight into early
Wednesday morning with the possibility of MVFR at KRBG for a few
hours. Some IFR fog/low ceilings are possible near Brookings by
early Wednesday morning too. Low clouds should retreat offshore
Wednesday morning yielding VFR the rest of the day as a drying air
mass and offshore flow take over. VFR will prevail elsewhere. It
should be noted that strong north winds will develop at KOTH
Wednesday morning with gusts to 40 kt possible in the afternoon and
early evening. Gusty north to northwest breezes will also develop at
the other TAF sites, but gusts should peak at 20-25 kt. -Spilde

&&

.MARINE...Updated 300 PM Tuesday, 20 June 2017...A thermal trough
along the coast will continue strengthening this evening, and
persist for several days, causing steep, wind driven seas. North
winds will increase this evening... hitting gale force for most of
the marine area by Wednesday morning. The steepest seas will
occur south of Cape Blanco... but even the northern portion of the
waters will still hit gale and haz seas criteria. Expect a slight
improvement of conditions Wednesday night and Thursday night...
but seas will remain dangerous hazardous to smaller vessels and
inexperienced mariners. Winds and seas will ramp back up during
the day. -MSC

&&

.PREV DISCUSSION... /Issued 549 PM PDT Tue Jun 20 2017/

DISCUSSION...An upper level trough tracking across western
Canada has weakened the ridging over the region. It is a bit
cooler across our area today, but a warming trend will resume on
Wednesday with the hottest temperatures of the year so far
expected as high pressure strengthens Friday through Sunday.
High temperatures will be near or above record levels. This will
include a strong Chetco effect with northeast winds producing
downslope warming at Brookings through Saturday. Low temperatures
will be around 5 to 15 degrees above normal and high temperatures
at 15 to 25 degrees above normal...including highs above 100 in
western valleys and in the 90s at east side valley locations.
Those planning outdoor activities Friday through Monday are
encouraged to take precautions to prevent heat related illness.

Besides the heat, the other main feature will be gusty north to
northeast winds which will be strongest through Thursday evening
near the coast and over the coastal waters. But, breezy to windy
northerly winds are expected across the area during the afternoon
and evening hours today through Thursday.

There are cumulus buildups and a slight chance of thunderstorms
this evening from southeast Siskiyou County near Mount Shasta east
and northeastward across Modoc County into southeast Lake County
near Lakeview and Hart Mountain. The air mass will dry later
tonight. The next slight chance of thunderstorms will arrive with
a shift in the pattern on Sunday afternoon back to a southwest
flow aloft. A shortwave or two may be embedded in the flow and
produce weak instability from the Cascades eastward. The
probability of an unstable airmass is higher on Monday afternoon
with good model agreement on a weak but relatively broad upper
trough approaching the Oregon coast. This trough will usher in an
onshore flow and is expected to lead to temperatures trending
down, closer to normal by the middle of next week. -DW

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.

CA...None.

Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Saturday
     for PZZ350-356-370.
     Gale Warning until 5 AM PDT Saturday for PZZ356-376.
     Gale Warning until 5 AM PDT Saturday for PZZ350-370.
     Small Craft Advisory until 11 PM PDT this evening for PZZ376.

MAS/DW/MSC