NWS Medford, OR wrote its last area forecast discussion before the first event at Oct 14, 7:00 AM PST, 6 hours earlier.
Area forecast discussion, Oct 14, 7:00 AM PST, 6 hours before
Area Forecast Discussion
National Weather Service Medford OR
800 AM PDT Sun Oct 14 2018
.DISCUSSION...14/12Z NAM in.
Mostly clear skies prevail across the Medford CWA this morning,
except for some low clouds and fog in the Umpqua Basin. Marine
stratus is creeping up from the south, but it hasn't reached the
MFR coastal waters yet. The 14/12Z Medford sounding was remarkably
dry, with a precipitable water value of 0.15 inches.
An omega block remains over the northeast Pacific, drifting very
slowly east. The anchor lows are now over southern California and
north of Hawaii. The high portion is centered near 42N 133W.
The block will continue drifting east, and the ridge axis will finally
finally move onshore Tuesday afternoon. By that time the anchors
will be over Arizona and near 32N 140W.
A thermal trough remains along the coast, bringing breezy east to
northeast winds along the coastal mountains in southwest Oregon
and mid slopes and ridges in western Siskiyou county. This trough
will remain in place into Monday morning, then move onshore in a
weakened state Monday afternoon, ending this prolonged easterly
wind scenario.
It will remain dry over the Medford CWA through Tuesday with
mostly clear skies inland, except for possible late night into
morning low clouds and fog in the Coquille and Umpqua valleys.
Usually after an easterly wind event, a southerly surge over the
coastal waters brings marine stratus into the area. In this case,
however, any southerly surge will be brief and confined to the
immediate coast, so if any part of the area sees marine stratus
Monday night into Tuesday, it will be the Brookings area.
Today will be the last warm day along the coast. The return of
onshore flow will make for a cooler day Monday. However, the
inland migration of the thermal trough will heat up inland areas,
especially the west side on Tuesday. By that time highs will be
10-20 degrees above normal over the inland west side and 5-10
degrees above normal east of the Cascades.
As far as lows go, tonight will be the last cold night over the
inland valleys. Overnight low temperatures may dip below freezing
in the coldest portions of the Rogue, Applegate, Illinois, and
Klamath valleys, and possibly the Umpqua as well.
The omega block will break down Wednesday, but ridging will
persist over the area through Saturday. This will make for
continued dry weather, with inland highs around 10 degrees above
normal. Skies will remain mostly clear inland, but marine clouds
will return to the coast and coastal waters, at least during the
late night into morning hours.
The forecast becomes much more uncertain from Sunday on as the
medium range model solutions diverge. Both the EC and the GFS
advertise the ridge breaking down, but differ on the progression
and strength of any fronts that may move onshore after the
breakdown.
&&
.AVIATION...For the 14/12Z TAFs...VFR will prevail throughout the
TAF period. There is some patchy low end MVFR stratus developing in
the Umpqua Basin, and this may reach KRBG before sunrise. However,
confidence was not high enough to include a broken deck in the TAF
but will monitor trends for updates.
Elsewhere, breezy east to southeast winds will keep skies clear and
marine stratus non-existent through this evening. Winds will be
quite breezy over the higher terrain and east of the Cascades today,
including KLMT, but also in portions of the Rogue Valley. Southeast
winds will align with the terrain and funnel into the Rogue valley
with the strongest winds expected towards the southern end. /BR-y
&&
.MARINE...Updated 800 AM PDT Sunday 14 October 2018...Gusty north to
northeast winds will continue to diminish this morning, dropping
below small craft advisory levels by this afternoon. Seas will also
gradually subside through today, but will remain steep due to fresh
swell through early Monday morning. Meanwhile, persistent long
period southerly swell around 3 feet may produce rough bar
conditions at Brookings and elevated surf at Port Orford. Aside from
this persistent southerly swell, conditions will remain relatively
calm for Monday and Tuesday.
Wednesday into Thursday, guidance continues to indicate a long
period west to northwest swell at 16 to 20 seconds building into the
coastal waters and will combine with the aforementioned smaller long
period southerly swell. Overall, wave heights are expected to remain
just below 10 feet, but hazardous bar and surf conditions will be a
concern for the latter half of the week. /BR-y
&&
.FIRE WEATHER...Updated 230 AM PDT Sunday 14 October 2018...Gusty
east to northeast winds are being observed in many locations near
and at the ridges with the thermal trough situated along the
Oregon Coast.
Strong high pressure extending over the area from western Canada and
the thermal trough along the Oregon Coast will persist into early
next week. This has brought gusty winds to many locations near and at
the ridges in southwest Oregon and western Fire weather zone 280.
Therefore we can expect critical weather conditions through Monday
morning time frame for most areas west of the Cascades. However, due
to significant wetting rainfall in many areas since September 30th,
most areas are at and forecast to remain at low to moderate fire
danger. This means fire spread concerns are generally low.
However fire danger is high in fire weather zones 621 and 280
because there was much less rain in these areas. Therefore, with the
expected weather conditions and the fuels status, red flag warnings
remain in effect for much of Fire Weather Zones 280 and 621 through
11 AM PDT Monday morning. Guidance suggests that sustained winds for
the higher terrain from the Cascades westward, could reach 20 to 30
mph with gusts 30 to 40 mph this morning which is being supported by
surface observations.
Also the winds are likely to reach down into valley areas that are
aligned with the terrain such as the southern end of the Rogue
Valley from Ashland to Talent where winds are likely to reach
sustained values of 15 mph with gusts to 25 mph. Winds could be as
strong tonight into Monday morning with some of the high res model
guidance showing a southeast component at 925mb with winds between
25-30 kts.
During this, the air mass will be generally drying out. Ridgetop
recoveries could end up as low as 15 to 25% in some areas, and many
areas will see afternoon RHs of 5-15%.
While east winds and low RHs will continue next week we're expecting
light winds Monday afternoon through next weekend as the thermal
trough shifts inland and pressure gradients aren't as tight. We
should also get a bit of a reprieve from the very dry air Wednesday
night through next Sunday morning. Steep overnight and morning
inversions will be common in the valleys during this time frame
providing chilly to cold mornings, but also seasonably mild to warm
afternoons. Dry weather will continue through at least next weekend.
-Petrucelli
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Frost Advisory until 9 AM PDT this morning for ORZ023.
Freeze Watch from late tonight through Monday morning for
ORZ023-024-026.
Frost Advisory until 9 AM PDT this morning for ORZ024-026.
Red Flag Warning until 11 AM PDT Monday for ORZ621.
Freeze Warning until 9 AM PDT this morning for ORZ024-026.
CA...Freeze Watch from late tonight through Monday morning for
CAZ080>082.
Frost Advisory until 9 AM PDT this morning for CAZ080.
Red Flag Warning until 11 AM PDT Monday for CAZ280.
Pacific Coastal Waters...Small Craft Advisory until 5 PM PDT this
afternoon for PZZ350-356.
Small Craft Advisory until 5 AM PDT Monday for PZZ370-376.
15/15/13