101
FXUS66 KMFR 182211
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
311 PM PDT Wed Sep 18 2024

.DISCUSSION...Satellite image shows the upper low digging south
along the California coast and is now centered west of the Bay Area.
At the same time some return flow is moving into portions of
northern California, with the net result being building cumulus.
Some of the data suggest instability will be marginal at best and
there could be a few isolated showers in southeast Modoc County this
afternoon. We dug further into the potential for isolated
thunderstorms and there`s not enough convincing evidence supporting
it, so we kept it out of the forecast. Elsewhere, it will remain
dry.

The rest of the forecast period will be rather quiet with dry
weather expected to last through at least the first half of next
week.

Tonight, cloud cover will dissipate and will end up with mostly
clear skies. However marine stratus will make a return along the
coast, north of Cape Blanco and into portions of the Umpqua Basin. A
thermal trough will set up along the south Oregon coast tonight with
offshore flow that will be sufficient enough to keep the marine
stratus offshore.

Thursday through early next week will be dry with afternoon
temperatures trending warmer for the interior. The thermal trough
will remain in place along the south Oregon coast and the pattern is
one where we could see afternoon temperatures at Brookings get into
the lower to mid 70s Thursday, then into the lower to mid 80s,
possibly the upper 80s Friday through the start of next week.
Tuesday, the thermal trough will build north and weaken some
allowing the flow to become weak onshore at Brookings, therefore it
should be cooler.

Upper ridging will build over the area Monday and Tuesday with
afternoon temperatures maxing out both these days, then the upper
ridge will flatten out some with the thermal trough shifting east of
the Cascades and being replaced with an onshore flow resulting in
cooler afternoon temperatures. -Petrucelli

&&

.AVIATION...18/18Z TAFS...Remaining cloud cover is clearing out
quickly across northern California and southern Oregon. While some
low levels are clinging to some west side terminals, VFR levels are
expected across the area this morning. Generally, VFR levels will
continue though the end of the TAF period. Marine stratus looks
likely to build later tonight, bringing MVFR and IFR ceilings. Some
guidance suggests a brief period of LIFR visibilities at North Bend
on Thursday morning, but there`s not high enough confidence to
include that in the TAFs quite yet. -TAD

&&

.MARINE...Updated 300 PM Wednesday, September 18, 2024...A thermal
trough will bring gusty northerly winds, building steep seas in
waters south of Cape Blanco this evening. Steep seas will spread to
waters north of Cape Blanco later Thursday morning, with very steep
and hazardous seas expected south of Pistol River. Periods of very
steep seas may be possible as far north as Port Orford on Thursday
and Friday afternoon and evening. Occasional gale gusts will be
possible on the afternoon and evening as well.

The thermal trough looks to remain in place through the weekend and
into next week, with signs of calming by Tuesday evening. A
Hazardous Seas Warning is in place for waters south of Pistol River
and beyond 5 nm from shore, and a Small Craft Advisory will cover
all other waters. Currently these hazards are in place through
Friday at 5 PM, bu are likely to extend through the weekend.
Additional guidance will help to determine the best areal
coverage for continuing chaotic seas. -TAD


&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory from 5 AM Thursday to 5
     PM PDT Friday for PZZ350-370.

Small Craft Advisory until 5 PM PDT Friday for PZZ356-376.

     Hazardous Seas Warning from 5 AM Thursday to 5 PM PDT Friday for
     PZZ356-376.

&&

$$

MAP/CZS/TAD