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000
FXUS66 KMFR 260427
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
927 PM PDT Mon Sep 25 2017

.UPDATE...
Updates were made to the Coastal Waters Forecast to lower winds
and wave heights for tonight. The sky condition forecast was also
adjusted to diminish cloudiness for this evening. BTL

&&

.DISCUSSION...
Some cloudiness is still present across the forecast area, but not
much, as the frontal system that moved into western Washington
and northwestern Oregon in the last 24 hours has fallen apart.
High pressure will continue to build over the area as the thermal
trough deepens along and near the coast. This will set the stage
for the warmest days of the week Wednesday and Thursday, when the
Medford Airport is likely to reach 90 degrees.

Forecast models are now indicating the possibility of a cold
front bringing some rain to portions of the forecast area as
early as Friday. Also, there is growing confidence in significant
rainfall early next week. BTL

&&

.AVIATION...26/00Z TAF CYCLE...At the coast...areas of MVFR
cigs/vis are expected to develop between 06z-09z with conditions
lowering to IFR late tonight after 09z and continuing into Tuesday
morning, mainly north of Cape Blanco and Brookings. There is low to
moderate confidence on the timing of MVFR and IFR conditions along
the coast. Conditions are expected to clear to VFR along the in the
late morning around 17z. Elsewhere, VFR is expected through the TAF
period. -CC

&&

.MARINE...Updated 200 PM PDT Monday, 25 September 2017...High
pressure offshore and a thermal trough along the coast will maintain
gusty north winds and steep wind seas through Tuesday. Winds and
seas will peak in the afternoon and evening today and Tuesday.
Through Tuesday afternoon, small craft conditions will affect areas
south of Cape Blanco. Then north winds are expected increase late
Tuesday afternoon into Tuesday evening. Occasional gusts to gale
force are possible Tuesday evening mainly from Gold Beach south
beyond 5 nm from shore. Very steep wind-driven seas are expected to
develop Tuesday evening from Brookings south between 10 nm and 45 nm
from shore with small craft advisory winds and seas affecting most
other areas from Cape Blanco southward and beyond 5 nm from shore
north of Cape Blanco. North winds and steep seas will gradually
diminish Wednesday afternoon. Light southerly winds and light seas
are expected Wednesday night into Thursday. On Saturday, a weak
front is expected to brush northern portions of the waters and seas
will increase as a northwest swell moves into the waters. -CC

&&

.FIRE WEATHER...Updated 200 PM PDT Monday, 25 September 2017....
The warming and drying trend will continue over the next several
days, with breezy north winds this afternoon, and breezy northeast
to east winds overnight tonight and again Tuesday night on the mid
slopes and ridges of Western Siskiyou County and Curry County. It`s
possible the higher peaks along the Cascades could get breezy winds
tonight, but we think winds could be stronger Tuesday night into
Wednesday morning and maybe Wednesday night into Thursday morning.
Offshore flow is expected to weaken Wednesday night along the coast
as the thermal trough moves inland. Weak onshore flow is possible
Thursday along the coast which could result in higher relative
humidities.

Confidence is now high that some poor to moderate humidity
recoveries will affect upper slopes and ridges Tuesday night through
Wednesday night. The overall breeziest night will be Tuesday night,
but the driest conditions are expected Wednesday night into Thursday
morning.

Afternoon temperatures are expected to peak, and humidity values are
expected to be at their lowest, Wednesday and Thursday as the
thermal trough moves inland. With dry and unstable conditions
expected by that point, if there is a period of time where fire
activity picks up, then that would be it.

At no time during the week do we expect critical fire weather
conditions. There will be periods of breezy and dry conditions, but
winds and humidity aren`t expected to align enough to warrant any
Fire Weather Watches or Red Flag Warnings.

A cold front will move through the area on Friday. The models differ
slightly with the timing, but it looks like westerly winds will
become gusty for much of the forecast area Friday afternoon and
evening. Also this front could bring some light precipitation along
the coast, north of the Umpqua Divide and northern Cascades. However
confidence is low how much rainfall these areas will get.
-Petrucelli

&&

.PREV DISCUSSION... /Issued 301 PM PDT Mon Sep 25 2017/

SHORT TERM...A warming and drying trend continues through the
middle of the week as a ridge expands into our area with northerly
flow into southern Oregon tonight. A weak impulse moving south in
this flow will bring occasional mid and high clouds and is
expected to generate light showers in the coastal waters north of
Cape Blanco. The impulse could also be enough to deepen the marine
layer in Coos County with occasional drizzle late tonight and
early Tuesday morning. At the coast the thermal trough is expected
to build up to Cape Blanco. This will lead to dry offshore flow
over the coastal range and western Siskiyou Mountains and warm
temperatures at Brookings both during the day and at night.

The thermal trough is expected to move inland Wednesday and remain
through Thursday. This will lead to very warm days with highs in
the Rogue Valley reaching the lower 90s. At the coast we could see
onshore flow and low clouds spreading into Curry County.

LONG TERM (Friday through Monday)...A cold front will move
through the area on Friday. The models differ slightly with the
timing, but it looks like westerly winds will become gusty for
much of the forecast area Friday afternoon and evening. Also this
front could bring some light precipitation along the coast, north
of the Umpqua Divide and northern Cascades. Both the ECMWF and GFS
maintains a broad trough over our forecast area so confidence is
moderate to high that temperatures will fall back to seasonal
normals. However confidence is low how much rainfall these areas
will get. /FB

AVIATION...25/18Z TAF CYCLE...At the coast...VFR conditions will
continue through this afternoon. There is moderate confidence in IFR
conditions returning tonight, mainly north of Cape Blanco, but
confidence on the timing is not as high. Elsewhere, VFR will
continue through the TAF period. -Petrucelli

MARINE...Updated 200 PM PDT Monday, 25 September 2017...High
pressure offshore and a thermal trough along the coast will maintain
gusty north winds and steep wind seas through Tuesday. Winds and
seas will peak in the afternoon and evening today and Tuesday.
Through Tuesday afternoon, small craft conditions will affect areas
south of Cape Blanco. Then north winds are expected increase late
Tuesday afternoon into Tuesday evening. Occasional gusts to gale
force are possible Tuesday evening mainly from Gold Beach south
beyond 5 nm from shore. Very steep wind-driven seas are expected to
develop Tuesday evening from Brookings south between 10 nm and 45 nm
from shore with small craft advisory winds and seas affecting most
other areas from Cape Blanco southward and beyond 5 nm from shore
north of Cape Blanco. North winds and steep seas will gradually
diminish Wednesday afternoon. Light southerly winds and light seas
are expected Wednesday night into Thursday. On Saturday, a weak
front is expected to brush northern portions of the waters and seas
will increase as a northwest swell moves into the waters. -CC

FIRE WEATHER...Updated 200 PM PDT Monday, 25 September 2017....
The warming and drying trend will continue over the next several
days, with breezy north winds this afternoon, and breezy northeast
to east winds overnight tonight and again Tuesday night on the mid
slopes and ridges of Western Sikiyou County and Curry County. It`s
possible the higher peaks along the Cascades could get breezy winds
tonight, but we think winds could be stronger Tuesday night into
Wednesday morning and maybe Wednesday night into Thursday morning.
Offshore flow is expected to weaken Wednesday night along the coast
as the thermal trough moves inland. Weak onshore flow is possible
Thursday along the coast which could result in higher relative
humidities.

Confidence is now high that some poor to moderate humidity
recoveries will affect upper slopes and ridges Tuesday night through
Wednesday night. The overall breeziest night will be Tuesday night,
but the driest conditions are expected Wednesday night into Thursday
morning.

Afternoon temperatures are expected to peak, and humidity values are
expected to be at their lowest, Wednesday and Thursday as the
thermal trough moves inland. With dry and unstable conditions
expected by that point, if there is a period of time where fire
activity picks up, then that would be it.

At no time during the week do we expect critical fire weather
conditions. There will be periods of breezy and dry conditions, but
winds and humidity aren`t expected to align enough to warrant any
Fire Weather Watches or Red Flag Warnings.

A cold front will move through the area on Friday. The models differ
slightly with the timing, but it looks like westerly winds will
become gusty for much of the forecast area Friday afternoon and
evening. Also this front could bring some light precipitation along
the coast, north of the Umpqua Divide and northern Cascades. However
confidence is low how much rainfall these areas will get.
-Petrucelli

&&

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

CA...None.

Pacific Coastal Waters...
- Small Craft Advisory until 11 AM PDT Wednesday for PZZ356-376.
- Small Craft Advisory from 5 PM Tuesday to 11 AM PDT Wednesday
  for PZZ350-370.
- Hazardous Seas Warning from 5 PM to 11 PM PDT Tuesday for
  PZZ376.

$$

BTL/FJB/MAP/CC