Small Craft Advisory 56, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
852 AM PDT Tue Jun 6 2017

.UPDATE...Clouds and patchy fog along the coast this morning is a
bit more extensive than previously thought, so have had to adjust
the sky cover there to account for the difference. Have also
adjusted some of the day two forecast just to be more in line
with the neighboring offices. Otherwise, the near-term forecast
looks good. For more information and the longer term forecast, see
the previous discussion below. -BPN

&&

.AVIATION...06/12Z TAF CYCLE...Low clouds with IFR cigs and local
IFR visibilities will continue along the coast and in the Coquille
valley  morning. Cigs are expected improve to MVFR late this morning
around 18-19z , then improve to VFR with areas of continuing MVFR
cigs along the coast after 21z this afternoon. IFR cigs are expected
to return to the coast early this evening between 02-05z. Elsewhere,
VFR conditions will prevail for inland locations for the next 24
hours. -CC

&&

.MARINE...Updated 830 AM Tuesday 6 June 2017...North winds and
seas will remain low through tonight. A front will approach the
coast on Wednesday and bring south winds to the waters. South
winds will increase and seas will build Wednesday afternoon
through Wednesday night with small craft advisory conditions
expected to develop. Winds will be strongest Wednesday evening,
then diminish by Thursday morning. Another front is expected
Friday into Saturday. - BTL

&&

.PREV DISCUSSION... /Issued 447 AM PDT Tue Jun 6 2017/

DISCUSSION...The weather today will be typical of summer. But, an
unusually strong and wet cold front late Wednesday into early
Thursday, and a following series of showery disturbances into the
weekend will make it readily apparent that it is still spring. It
will have been about 3 weeks since the previous episode of a cool
and wet pattern affected the area. Arguably, the biggest impacts
from late Wednesday through at least Saturday will be heavy rain
at the coast into Josephine and western Siskiyou Counties, and
strong winds and snow at the higher elevations including Mount
Mcloughlin, Mount Shasta, and the peaks surrounding Crater Lake.

Model agreement is very good through Thursday and still not bad
into Saturday. The main front will affect the coast beginning
late Wednesday afternoon and exit east of our area by Thursday
evening. There will be a bit of a lull Thursday night before the
next front affects the area Friday into Friday night. The weekend
will get off to a cold and wet start with a shortwave disturbance
to be the third feature to move into the area. From Sunday
onward, there is little agreement from run-to-run or model-to-
model regarding the progression of the cold upper level trough or
the strength and arrival time of a ridge to follow. We have gone
with a low confidence forecast close to the GFS ensemble mean for
early next week...with a diminishing probability of showers and
trend of temperatures back up to near normal.

First, the forecast for today is little changed. It will be
generally a few degrees warmer this afternoon than on Monday while
very weak instability could generate a few low-topped cumulus
clouds over the higher terrain...with a slight chance of
sufficient development for a convective afternoon shower over the
higher terrain over western Siskiyou County.

The models have shown a good bit of consistency during the past 3
model runs regarding the timing and impressive strength of the
late Wednesday into Thursday cold front. Rain is likely to begin
at the coast early Wednesday evening...around 5 PM and spread to
the Cascades by midnight...then across the east side through
Thursday afternoon or early evening. The 00Z GFS indicates
Alturas and Lakeview likely won't see a measureable amount until
after 8 AM Thursday. Coastal rainfall of half an inch to 2 inches
is expected with inland west side amounts in the ballpark of a
quarter of an inch to an inch and east side values up to a half
inch. Snow levels are forecast to fall to around 8000 feet.

Post-frontal showers and snow showers will diminish from west to
east Thursday through Thursday night with activity at a minimum
in the pre-dawn hours early Friday.

The next front will bring another soaking to the coast Friday
morning and afternoon then there will not be much, if any break
before a trailing shortwave trough brings additional rain showers
Friday night through Saturday. The strong cooling trend is likely
to reach its peak on Saturday as the parent upper level trough
swings into the Pacific Northwest. Snow showers are expected down
to around 6000 to 7000 feet on Friday and 5000 to 6000 feet on
Saturday.

Lighter showers and snow showers Saturday night may linger into
Sunday or possibly even through day 7/Tuesday. At the least, a
decrease in clouds should at least start a warming trend Sunday
afternoon after a cold northerly flow is likely to bring a chilly
start to the day.

&&

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

CA...None.

Pacific Coastal Waters...None.

BPN/BTL/DW/CC