Heat in Oregon, July 12 to 17, 2018

Area Forecast Discussion
National Weather Service Medford OR
932 AM PDT Thu Jul 12 2018

.UPDATE...The current forecast is on track and only a few updates
were made to todays forecast. Low stratus and fog is clearing from
the Coquille valley and coast north of Cape Blanco. A southerly
surge of low stratus has Orick (in Del Norte County) and is
approaching Crescent City. Brookings has probably already hit its
high temperature today, and conditions will cool over the next few
hours as low clouds, and some patchy fog move into the area.
Elsewhere, we're still expecting the hottest day of the year just
about everywhere. Expect temperatures to be around 4 to 10 degrees
higher than yesterday... or near 105 here in Medford, mid to upper
90s in Klamath Falls and Lakeview, and pushing 110 in lower
Klamath/Salmon river valleys. For more details view the forecast
for your area. See previous discussion for more information on the
forecast over the coming days.

&&

.AVIATION...For the 12/12z TAFs...Along the coast north of Cape
Blanco, IFR ceilings have moved into North Bend with occasional LIFR
around sunrise through mid morning. Most of the rest of the Coos
Coast and the Coquille Valley can expect IFR into this morning,
before clearing to VFR for the midday/afternoon. Satellite imagery
also shows widespread IFR in the coastal waters out to 20 nm from
shore down to just south of Cape Blanco. Weak offshore flow south of
Cape Blanco has been keeping Brookings VFR all night and into this
morning. Gusty north winds are expected again at North Bend this
afternoon with gust to 30 knots likely. Elsewhere VFR is expected
with light winds. -FB

&&

.MARINE...Updated 830 AM PDT Thursday 12 July 2018...The thermal
trough will weaken today, so winds will continue to ease, but seas
will remain steep to very steep through Friday morning. The highest
seas (10-12 ft) will be beyond 20 nm from shore between Cape Arago
and Cape Blanco, then beyond about 8 nm from shore south of Cape
Blanco. Seas will remain elevated and choppy, but sea heights will
trend slightly lower Friday into Sunday. -FB/DW

&&

.FIRE WEATHER...Updated 230 AM PDT Thursday, 12 July 2018...
A thermal trough will remain along the southern Oregon coast.
Northeast winds will not be as strong this morning compared with
Wednesday morning but it will trend drier along the coast.

Temperatures will be hotter than normal, roughly 10 to 15 degrees
above average through much of next week. There is a slight chance
for thunderstorms Friday afternoon into Saturday. The best potential
for thunderstorms is in Siskiyou county, the Siskiyou Mountains, and
across Modoc into southern Lake counties.

With monsoon moisture coming up from the south, any thunderstorms
could initially be dry late Friday but should quickly transition to
wet. -FB

&&

.PREV DISCUSSION... /Issued 554 AM PDT Thu Jul 12 2018/

SHORT TERM...Hot temperatures are expected across inland areas
today as high pressure builds over the region. High temperatures
this afternoon are expected to rise 5 to 10 degrees above
yesterdays highs. Models remain on track showing highs in the 100
to 107 range across inland valleys west of the Cascades and
possibly as high as 110 in portions of the lower Klamath River
valley in western Siskiyou County. Eastern valleys will see very
warm temperatures as well with highs in the mid  90s. On Friday,
expect temperatures to lower a few degrees as monsoon moisture
moves into the area from the south and brings some clouds and
slight risk for thunderstorms. Temperatures then rise again
Saturday and Sunday with very hot conditions continuing through
at least Monday.

The extended period of hot daytime temperatures with limited
relief at night will be the main weather concern today through
Monday. Models continue to show temperatures in the triple digits
for many inland valleys west of the Cascades today through early
next week. the hottest temperatures are expected today and again
on Sunday with high temperatures around 100 to 107 across inland
valleys west of the Cascades with temperatures locally up to 110
in some lower valleys in Western Siskiyou County. Temperatures
will dip slightly on Friday as monsoon moisture brings mid and
high clouds into the area along with a slight chance for
thunderstorms. However, this will provide little relief with
highs still expected to be at or near the low 100s in western
valleys. Then temperatures increase again Saturday into Sunday as
an upper level ridge builds into the area. The heat continues into
early next week with models indicating the strong high pressure
ridge remaining in place on Monday. Overnight lows are expected to
only lower into the lower 60s to lower 70s each night. The
prolonged heat may bring significant heat impacts to western
portions of the area. Heat advisories and excessive heat warnings
remain in effect through Monday for inland western valleys. Please
see the NPWMFR for details. Additionally, valleys east of the
Cascades will also see very warm temperatures through Monday with
highs expected to be in the 90s and possibly reaching near 100 on
Sunday and Monday.

Isolated thunderstorms are also a concern, mainly on Friday,  as
models continue to show mid and high level moisture and weak
shortwaves moving up from the south. There is good agreement that
moisture will move into Siskiyou County by Friday morning and
increase Friday afternoon with isolated storms expected to
develop over the mountains. The storms may slowly spread
northeastward into the Siskiyous and into portions of southern
Oregon, including southeast Josephine and Jackson counties as
well as into the Southern Oregon Cascades and Klamath county.
Additionally, storms may develop over southern Modoc in the
afternoon then spread north into portions of Lake county and
eastern Klamath county. The moisture for storms is somewhat
elevated so higher cloud bases are possible. Additionally,
variable and gusty outflow winds are possible near any storms that
develop.

On Saturday, moisture lingers across Siskiyou, Modoc and eastern
Klamath and Lake counties. With additional weak shortwaves moving
over the area from the southwest, a slight risk for thunderstorms
continues for these areas Saturday afternoon and evening.

LONG TERM...Tuesday through Thursday...High pressure is expected
to remain in place next week but a shortwave moving inland to the
north may weaken the high Tuesday into Wednesday. There is
variability in the models in the strength of the high pressure
ridge. So confidence is lower on the details of the temperatures
forecast during this period. Continued very warm temperatures are
likely for inland areas though. Coastal areas will generally see
cool conditions but a strengthening thermal trough along the coast
may bring a local Chetco effect to the Brookings area Tuesday
through Thursday. Also expect gusty northerly winds along the
coast and over the coastal mountains during this period. Overall,
models show dry weather on Tuesday. Then Wednesday into Thursday,
the GFS indicates some southerly moisture moving area. However,
not all model solutions support this. Of note, the ECMWF shows the
position of the ridge axis further west through Thursday and
keeps monsoon moisture well to the southeast. Given the lower
confidence in this period, have kept thunderstorms out of the
forecast for Wednesday and Thursday.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Heat Advisory from 2 PM this afternoon to 11 PM PDT Monday for
     ORZ023.
     Excessive Heat Warning from 2 PM this afternoon to 11 PM PDT
     Tuesday for ORZ024-026.
     Heat Advisory from 2 PM this afternoon to 11 PM PDT Tuesday for
     ORZ024-026.

CA...Excessive Heat Warning from 2 PM this afternoon to 11 PM PDT
     Tuesday for CAZ080-081.

Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Friday for PZZ350-356-370.
     Hazardous Seas Warning until 5 AM PDT Friday for PZZ356-370-376.

MSM/CC/FJB