Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 281639
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
939 AM PDT Wed Jun 28 2017

.DISCUSSION...Another quiet morning in southern Oregon and
northern California. The marine layer made its morning push into
the western valleys but it wasn`t as thick and didn`t push as far
inland as it did yesterday. The Umpqua Basin filled up with marine
clouds but just a small patch of clouds developed in southeast
Josephine County. As such, the marine layer is retreating faster
than yesterday. Thus sunny skies earlier in Douglas County should
allow temperatures there to be around 5 degrees warmer than
yesterday. Current forecast looks on track so no updates needed.

&&

.AVIATION...28/12Z TAF CYCLE...A mix of IFR and MVFR cigs and vsbys
with patchy drizzle extends from the coastal waters into the coastal
valleys and the Umpqua Valley. These conditions will slowly improve
after 15Z into the early evening with VFR expected at Roseburg by
18Z then to North Bend around 20Z. Stratus is expected to surge
inland again into the Coquille Valley by 04Z this evening and into
the Umpqua Valley after midnight. Otherwise, VFR is expected away
from the coast. -DW

&&

.MARINE...Updated 430 AM Wednesday, 28 June 2017...
Gusty north winds and steep to very steep seas are likely through
early next week with high pressure offshore and a thermal trough at
the coast expected to be persistent features. Winds and seas will be
highest south of Cape Blanco...especially south of Cape Sebastian
beyond 10 NM from shore. Winds and seas will reach a peak this
evening...diminish slightly Thursday night into Saturday morning
then build through the weekend into early next week with a
possibility of gales beginning Sunday afternoon. The main
uncertainty in the forecast is regarding the extent of improvement
Thursday night into Saturday morning. Seas may remain steep south of
Cape Blanco or at least south of Cape Sebastian through that period.
-DW


&&

.PREV DISCUSSION... /Issued 307 AM PDT Wed Jun 28 2017/

DISCUSSION...
68 lightning strikes occurred across northern Lake County this
past evening as an upper level trough of low pressure moved
overhead while just enough moisture and instability developed
from afternoon heating. Today will be the first day of this
current week without any thunderstorm activity as a drier
northwest flow develops over us and temperatures warm aloft.

All in all, there will be little day to day variation in the
weather for most of us over the next week. Daytime highs will
fluctuate from right about normal to 5-10 degrees above normal.
The marine layer will continue to bring low clouds, fog, and some
drizzle to areas along and near the coast and into the Umpqua
Basin. Afternoons will be dry with typical afternoon and evening
breezes.

Temperatures today are expected to be a little cooler than 24
hours ago at most inland Oregon locations outside of the marine
layer due to the increased onshore northwest flow caused by the
upper level trough that moved through this past evening. Tonight
through Thursday morning light northeast winds will develop above
the valleys resulting in a cooler and drier night for valley
locations. Temperatures are expected to warm up a few degrees
Thursday and Friday.

Upper level diffluence and some cooling aloft from an upper level
low moving into California has been depicted by some of the model
guidance for Friday afternoon and evening. A slight chance of
thunderstorms has been added to the Friday afternoon and evening
forecast for portions of Siskiyou County from around the Trinity
Alps and Scott Valley northeast to the Goosenest Ranger District
area north of Mount Shasta. Both moisture and instability are
marginal for thunderstorms for that time period, hence the slight
chance wording.

Behind the Friday upper level low northwest winds will again
increase Friday night into early Saturday. It appears that this
time period will need to be monitored for a possible inland surge
by the marine layer. By late Saturday into Sunday temperatures
will warm again as stronger high pressure ridging builds in. An
approaching upper level trough on Monday will bring another
slight threat of thunderstorms to portions of Siskiyou and Modoc
Counties under a west-northwest flow.

In other words, summer is surely here, as each day will be quite
similar to the previous one with very warm afternoons, cool
nights, and increasing dryness. BTL

AVIATION...28/00Z TAF CYCLE...09Z Update...
IFR along the Curry County coast south of Gold Beach is expected to
drift southeastward this morning as northwest winds build back in.
MVFR across the coastal waters northwest of Port Orford and across
Coos County is likely to continue through the day today. MVFR from
the Umpqua Divide northward across Douglas County is likely to
expand into Josephine County this morning and could even affect
portions of Jackson County, though confidence is low that the MVFR
ceilings will make it into Jackson County. Ceilings are likely to
again dissipate around midday for the inland counties. Otherwise,
VFR is expected away from the coast. BTL

MARINE...Updated 300 PM Wednesday, 27 June 2017...
North winds will increase and seas will steepen through Wednesday
evening as high pressure rebuilds offshore and the thermal trough
deepens over California. Warning level seas are expected to
develop over a portion of the area south of Cape Sebastian and
beyond 10nm from shore Wednesday into Thursday. Northerly gales
are possible south of Cape Blanco and about 20nm out this weekend
as cooler air pushes southeastward from the Gulf of Alaska.

&&

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

CA...None.

Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Thursday for PZZ356.
     Hazardous Seas Warning until 5 AM PDT Thursday for PZZ356-376.
     Small Craft Advisory for hazardous seas until 11 AM PDT this
     morning for PZZ356.
     Small Craft Advisory for hazardous seas from 5 AM to 11 PM PDT
     Thursday for PZZ356.
     Small Craft Advisory for hazardous seas until 11 PM PDT Thursday
     for PZZ350-370-376.
     Small Craft Advisory until 11 PM PDT Thursday for PZZ376.

$$

KRS/KRS/RES



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