Wildfire in Oregon, August 1 to 10, 2016

Area Forecast Discussion
National Weather Service Medford OR
1109 PM PDT SUN JUL 31 2016

Updated Aviation section

.UPDATE...
Marine and Fire weather updates have been made through the evening,
primarily to account for changing hazard headlines. btl

&&

.DISCUSSION...
A very dry air mass lies over the forecast area this evening. Red
Flag criteria was easily reached across the Modoc this afternoon
and evening, and is expected to again tomorrow. Meanwhile, the
subsidence inversion continues to lower tonight and even tomorrow
night, so there is concern that it will remain fairly dry at
higher elevations such as at the Bybee Creek Fire tonight and
tomorrow night. That fire was reported to be at 416 acres this
evening.

Tomorrow an upper level low approaching the Pacific Northwest
will enhance winds a bit over today's for inland areas resulting
in critical fire weather conditions for southeastern portions of
the area. Monday night into Tuesday this low will move inland to
our north resulting in the beginning of a cool down, but also more
wind and low humidity that could again reach critical levels in
some areas.

a warming trend Wednesday and Thursday will end Friday through
Sunday as two upper level lows move in from the southwest. there
is growing concern that these two low pressure systems will bring
lightning across portions of the area in the Friday through Sunday
time period. BTL

&&

.AVIATION..01/06Z TAF cycle... Northeast winds will lessen
overnight, so IFR cloud decks should be more widespread and
persistent tonight through Monday morning than was observed along
and near the coast last night. Confidence is moderate that KOTH will
see IFR conditions 10z-17Z. Otherwise, VFR conditions area expected
with gusty afternoon and evening winds, especially along and near
the coast. BTL

&&

.MARINE...Updated 252 PM PDT, Sunday, 31 Jul 2016...
A thermal trough along the coast and high pressure offshore will
continue to produce moderate to strong north winds and steep to very
steep wind driven seas through this evening. The area of gales and
hazardous seas is expected from  near Cape Blanco southward for the
waters beyond 6 nm from shore. Elsewhere, small craft advisory
conditions are expected. Winds will lower slightly on Monday but
still expect gales and steep to very steep seas over the waters
south of Cape Blanco with steep seas and periods of moderate winds
elsewhere. North winds will lower briefly below gales for areas
south of Cape Blanco and below small craft advisory levels from Cape
Blanco north beginning late Monday evening and continuing through
Tuesday morning. However, winds will rise again Tuesday through
Thursday.  Moderate to strong winds and steep to very steep seas are
expected to redevelop for areas south of Cape Blanco Tuesday
afternoon into Tuesday evening. Then gale conditions south of Cape
Blanco with small craft advisory conditions from Cape Blanco
northward area possible Wednesday through Thursday. -CC

&&

.FIRE WEATHER...Updated 130 PM PDT Sunday, 31 July 2016...
There is concern for gusty winds and low relative humidities for the
next few afternoons/early evening hours east of the Cascades. The
Red Flag Warning for a good portion of FWZ 285 remains in effect for
this afternoon and early evening. The fire weather watch for Monday
has been upgraded to a red flag warning for FWZ 285 and the
southeastern portion of FWZ 624.

The models continue to show Tuesday being windier. An upper low is
expected to drop southeast towards northwest Washington Tuesday
afternoon into with an increasing southwest flow ahead of the low. A
fire weather watch has been issued for fire zone 285 and eastern
portions of 624, extending up the Winter Ridge, and southern
portions of 625.

Lastly, latest models are suggesting increased moisture and
instability on Friday and Saturday as upper troughing moves into
Northern California. Sven

&&

.PREV DISCUSSION... /Issued 256 PM PDT SUN JUL 31 2016/

SHORT TERM...Two features will affect us in the next 24 hours.
The first is the thermal trough along the coast that will drive
gusty north winds again tonight over the coastal range of Curry
County. Winds will not be as strong tonight as last night but we
still expect conditions to be very warm and dry. The other feature
is the moderate strong west winds that are surfacing in NE
California and the Klamath and Tulelake Basins. The combination of
winds and low humidity in Modoc County is significant enough to
warrant the Red Flag Warning, but conditions in southern Klamath
and Lake County comes close to but does not meet the criteria.

On Monday a low pressure will approach Vancouver Island. This low
will move inland over Washington State but the trough is deep
enough to help bring cooler air into southern Oregon and northern
California. Gusty west winds will occur again over most areas east
of the Cascades and wind speeds appear stronger than this
afternoon. Onshore flow increases Monday night and will bring
lower marine clouds into the Umpqua Basin by Tuesday morning. High
temperatures on Tuesday will be up to 5 degrees cooler than
seasonal norm, even down in the Mount Shasta and Happy Camp areas.

By the end of Tuesday the main upper level low pressure is
forecast to into northern Idaho with westerly flow becoming
dominant as far south and Siskiyou/Modoc County. The atmosphere
will continue to be dry and this will also be a concern due to
another day of breezy conditions. In Lake and western Harney
county winds are expected to be out of the north and could be
quite gusty on Tuesday. As with these summertime trough, the cool
air is quite shallow and temperatures will rebound quickly Tuesday
and Wednesday. The cool temperatures will be felt more at night
with lows remaining closer to seasonal norms.

LONG TERM (Thursday to Sunday)...Both the GFS and the ECMWF are
in reasonable agreement at bringing a low pressure down to south
central BC. This will send a cold front into southern Oregon on
Thursday. Both models are starting to show a short wave trough
moving into northern California Thursday with increasing moisture
coming into the Cascades from the south. We would like to see one
more run on this feature but if present this could lead to
thunderstorms toward next weekend; otherwise, we can expect
temperatures to decrease down toward seasonal norms next by next
weekend.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from noon to 9 PM PDT Monday for ORZ624.
     Fire Weather Watch from Tuesday afternoon through Tuesday
     evening for ORZ624-625.

CA...Red Flag Warning from noon to 9 PM PDT Monday for CAZ285.
     Fire Weather Watch from Tuesday afternoon through Tuesday
     evening for CAZ285.

Pacific Coastal Waters...
- Small Craft Advisory until 5 AM PDT Wednesday for PZZ356-376.
- Hazardous Seas Warning until 8 PM PDT Monday for PZZ356.
- Small Craft Advisory until 8 PM PDT Monday for PZZ350-370.
- Gale Warning until 8 PM PDT Monday for PZZ376.
- Gale Warning from 2 PM Tuesday to 5 AM PDT Wednesday for
  PZZ376.
- Hazardous Seas Warning until 2 PM PDT Tuesday for PZZ376.

BTL/FJB/CC