-- Discussion containing changed information from previous version are highlighted. --
875
FXUS66 KMFR 131126
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
426 AM PDT Thu Jun 13 2024

...New Aviation Section...


.AVIATION (12Z TAFs)...

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Current observation at North Bend (KOTH) doesn`t indicate low
clouds, but satellite suggest this is a possibility this morning,
so went ahead and added some IFR ceilings based on satellite
trends. Otherwise, the inland TAF sites are expected to remain in
VFR throughout this cycle, but expecting high clouds to infiltrate
over the region tonight. KOTH will likely see some relief and VFR
conditions later today, but another round of low stratus is
anticipated Friday morning. Lastly, breezy afternoon wind speeds
are expected today.

-Guerrero
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&&

.PREV DISCUSSION... 
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/Issued 258 AM PDT Thu Jun 13 2024/

DISCUSSION...Fog is building in the Coquille valley and current
expectations are for there and portions of Curry county around
Brookings to be the only places where fog forms.

The thermal trough along the coast will shift inland today. This
will bring a small 1 to 3 degree bump up in temperatures from
yesterday and drier conditions along the I-5 corridor. The
displacement of the thermal trough is being driven by the
overspreading of a mid-level trough over the Pacific coast. In
addition to the small fluctuations in temperature and humidity,
the larger impact will be to winds. The west east pressure
gradient will amplify, causing the typical diurnal winds to be a
bit stronger than normal (10-20 mph, gusts around 30-35 mph). This
will be especially true in the lee of the Cascades, where the
downslope winds and humidities below 15% could lead to brief
critical fire weather conditions for 1 to 2 hours in Modoc, Lake,
and eastern Klamath County. Critical fire weather conditions may
also exist for an hour or two around the Scott Valley today.
However, it`s important to note that these conditions are fairly
typical in the summer and not really uncommon.

Friday, a noticeable cooldown is expected as the trough moves a
cooler polar air mass into the region. Conditions will again be
windy in the afternoon as the diurnal winds get an enhancement,
but with humidities trending up a few percentages, no fire weather
concerns are expected. Perhaps the bigger concern will be the
cold temperatures in the mountains and areas east of the Cascades.
Near to below freezing temperatures are expected Friday night and
continuing through the weekend. Anyone in these areas with plants
outside will want to consider covering them, and campers will
want to make sure they plan appropriately for these cold
temperatures.

There is a small chance for rain amounts less than 0.05" Friday
night across Coos, Douglas, and northern Klamath County,
especially in the higher terrain. The more moist front is
expected Sunday into Monday. Chances are peaking around 40%, so
nothing is certain with this front other than some elevated wind
speeds and a good marine push leading to increasing humidities.
If enough moisture does arrive with the front to produce
precipitation, amounts are generally expected to be less than
0.1", except in the coast range and the Cascades, where up to 0.2"
seems reasonable. There could also be a thunderstorm threat with
this system, but for right now, the greatest instability is ahead,
not along, the front and the core of the trough is too far north
to add thunderstorms to the forecast. That said, some showers will
still be strong and their heavier precipitation rates combined
with snow levels near or below below 6kft, the peaks of the
Cascades (including at Crater Lake NP) could pick up some new wet
snow cover.

We will remain in this cooler, unsettled weather pattern into the
start of next week.

-Miles

AVIATION...13/06Z TAFs...VFR continues nearly everywhere late this
evening. For most of the area, it will remain that way for the next
24 hours. Patchy MVFR ceilings are developing in portions of
northern Curry County and along the coast north of Cape Blanco. With
the wind expected to be slightly E of due north, the clouds that
continue to form overnight may just hug the immediate coastline. At
North Bend, we`re maintaining SCT010 after 10Z, with the idea that
perhaps it could go either way (50/50 chance of BKN or SKC) in the
early morning hours Thursday. Similarly, patchy MVFR ceilings are
possible in the Umpqua Basin, though again, confidence in a BKN
ceiling is low. As such, the Roseburg TAF continued with SCT020 for
a few hours (14-17Z) Thursday morning (with about a 30% chance of
BKN). Gusty northerly winds will redevelop along the coast Thursday
afternoon, but won`t be as strong as today. Breezes similar to
today`s will develop over the inland valleys, though it`ll probably
be a bit gustier over the east side, including at Klamath Falls.

-Spilde

MARINE...Updated 230 AM Thursday, June 13, 2024...Steep seas will
continue across all waters through Friday morning, with areas of
very steep seas (Hazardous Seas Warning) continuing south of Port
Orford this morning across the outer waters. Thereafter, relatively
calmer seas are expected through Sunday morning. By Sunday
afternoon, there is a lot of uncertainty with model guidance, and
there is at least some potential for a strong closed low to pass
aloft. This could bring in a strong fresh swell in addition to
stronger wind speeds than we currently have forecast at the moment.
We essentially have a scenario where either an upper level low takes
a northern track or a southern track through the PacNW Sun-Mon. As
the track becomes clearer, we should have a much better idea of
potential hazards (or lack thereof) over the waters.

-Guerrero
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&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 2 AM PDT Friday
     for PZZ350-356-370.

Hazardous Seas Warning until 11 AM PDT this morning for PZZ376.

     Small Craft Advisory from 11 AM this morning to 2 AM PDT Friday
     for PZZ376.

&&

$$