Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 251606
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
906 AM PDT Mon Sep 25 2017

.DISCUSSION...Mid level clouds are streaming into southern Oregon
and northern California under a northerly steering flow. A weak
impulse is also moving into northern Oregon and models show light
showers in the northern part of the coastal waters but none
inland. This looks reasonable as time height display of points in
Douglas County shows cloud base to be quite high. The surface
analysis also shows the thermal trough is building along the coast
up to Gold Beach. This will lead to offshore winds tonight and
Tuesday night. It appears that NE to E winds will be strongest
tonight but the lowest humidity will not be until Tuesday night.
This will present a fire weather concern especially for the Chetco
Bar Fire area and other fires in western Siskiyou County, although
recent rain could mitigate some of the concern.

Wednesday and Thursday will be the warmest day for inland area as
the thermal trough moves inland. Confidence is moderate to high
that the high temperatures for the Rogue Valley will be around 90.
The next front is still on track to bring slightly cooler
temperatures to our area Friday and next weekend but it will also
bring breezy conditions. /FB

&&

.AVIATION...25/12Z TAF CYCLE...Patchy IFR to LIFR fog and low
ceilings are occurring along the coast north of Cape Blanco, and
these should lift to VFR later this morning. There is moderate
confidence in IFR conditions returning to the coast
tonight. Elsewhere, VFR will prevail. SK

&&

.MARINE...Updated 230 AM PDT Monday, 25 September 2017...High
pressure offshore and a thermal trough along the coast will maintain
gusty north winds and steep wind seas south of Cape Blanco through
Tuesday. Winds and seas will peak each afternoon and evening through
Tuesday. North winds may increase even further late Tuesday
afternoon into Tuesday evening and bring a mix of steep to very
steep seas south of Cape Blanco with steep seas and small craft
advisory winds possible north of Cape Blanco. There is a slight
chance that gales develop late Tuesday afternoon south of Cape
Blanco beyond 10 NM from shore. North winds and steep seas gradually
diminish Wednesday. Light southerly winds and light seas are
expected Wednesday night into Thursday. SK

&&

.PREV DISCUSSION... /Issued 632 AM PDT Mon Sep 25 2017/

Updated aviation discussion.

DISCUSSION...Now that we are officially in Fall, Summer like
conditions make a return this week. The weak system that is
visible on satellite washes out to the north of our forecast area
as the upper level ridge nudges over the top of our area. As the
upper ridge continues to move over the region, offshore flow
spreads across the east side by Tuesday morning. This pattern
remains in place through the middle of the week with temperatures
rising to near 90 in the west side valleys on Wednesday. The
thermal trough at the coast moves inland Thursday, bringing the
warmest day of the stretch. At the end of the week the GFS and the
ECMWF remain in good agreement, with both showing the upper ridge
moving east and a weak front moving in Friday. A weak ridge
builds Sunday, and another, slightly stronger front moves in
Monday.

Even though we are officially in Fall, Fire season is NOT OVER!
Across the region things will heat up and become very dry again
by mid week, and the things that can cause fires, like backyard
debris burning, including the use of burn barrels are still
prohibited and can cause wildfires!

Sven

AVIATION...25/12Z TAF CYCLE...Patchy IFR to LIFR fog and low
ceilings are occurring along the coast north of Cape Blanco, and
these should lift to VFR later this morning. There is moderate
confidence in IFR conditions returning to the coast tonight.
Elsewhere, VFR will prevail. SK

MARINE...Updated 230 AM PDT Monday, 25 September 2017...High
pressure offshore and a thermal trough along the coast will maintain
gusty north winds and steep wind seas south of Cape Blanco through
Tuesday. Winds and seas will peak each afternoon and evening through
Tuesday. North winds may increase even further late Tuesday
afternoon into Tuesday evening and bring a mix of steep to very
steep seas south of Cape Blanco with steep seas and small craft
advisory winds possible north of Cape Blanco. There is a slight
chance that gales develop late Tuesday afternoon south of Cape
Blanco beyond 10 NM from shore. North winds and steep seas gradually
diminish Wednesday. Light southerly winds and light seas are
expected Wednesday night into Thursday. SK

FIRE WEATHER...Updated 300 AM PDT Monday, 25 September 2017....
The warming and drying trend will continue over the next several
days, with breezy north winds in the afternoon, and breezy northeast
to east winds overnight in the high terrain of Western Sikiyou
County and Curry County, as well as the Cascades. Confidence is now
high that some poor to moderate humidity recoveries will affect
upper slopes and ridges Tuesday night through Thursday 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, around 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 next 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.

When the thermal trough moves east of the forecast area on Friday
afternoon, westerly winds will become gusty for much of the forecast
area.

Looking further out, recent trends in the long range models suggest
some wetting rains are possible roughly by the middle of next week,
but confidence on this is low. -SK/BPN

&&

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

CA...None.

Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Wednesday for PZZ356-376.
     Hazardous Seas Watch from Tuesday afternoon through late Tuesday
     night for PZZ376.

$$

FJB/FJB/NSK



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