844
FXUS66 KMFR 180539
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1039 PM PDT Fri May 17 2024

...UPDATED AVIATION AND MARINE DISCUSSIONS...

.SHORT TERM...Friday through Saturday night...An upper low will slide
by northeast of the area today. This upper low will be followed by
another upper low north of the area Saturday. Temperatures will be
near normal and similar both Friday and Saturday. There will be
less cloud cover inland Saturday morning compared to Friday
morning. For Friday night and Saturday morning, low clouds should
be mainly north of Cape Blanco on the coast and in the Umpqua
Basin. Afternoon winds will be gustier Saturday, especially east
of the Cascades. 700 mb (10,000 ft) winds are expected to be
stronger as the 2nd upper low will be closer to the area.
Afternoon heating and mixing will create gustier surface winds
between 2 and 8 pm Saturday.

.LONG TERM...An upper level low will be in southwestern Canada and
this will dip into the PNW this weekend. However, the placement
of this dip Sunday will still be far enough for our area to see a
large increase in precipitation chances. I have added a ~15% PoP
from 00Z Sunday to 00Z Monday near the Lane-Douglas Cascades with
a lower PoP added farther south in Douglas County to account for
the ensembles supporting more of an isolated chance in these
areas.

While this trough lowers, a cooldown will come for the day Sunday.
For comparison, temperatures Saturday afternoon are expected to be
slightly above normal near Medford and east with slightly below
normal temperatures west. By Sunday all locations will be 5 to 15
degrees below normal. The spots that will see the largest cooldown
will be east of the Cascades as they`ll go from highs in the low 70s
to the upper 50s on average.

By Tuesday an upper low will come from western Canada and this path
will come closer to the western United States coast, so more impacts
will be possible. For now, the PoPs have increased for more of
southern Oregon in the Cascades and northern and central Lake and
Klamath counties. A 300 mb northerly jet of 55-65 knots, but CAPEs
are over 100 J/kg farther in eastern Oregon, so thunderstorm chances
are under 15% with this precipitation chance. Rain chances will be
highest in this area through Wednesday afternoon. Lingering rain
chances will be kept in the long term, however with more
disagreement on the placement of the trough during that time it
could change. -Hermansen

&&

.AVIATION...18/06Z TAFs...Clear skies and VFR conditions across the
forecast area will continue through most of the TAF period. Some
higher cirrus may filter in from the north, especially in Oregon.
The main concern tonight will be LIFR ceilings along the coast later
tonight as the boundary layer compresses, however; guidance is not
showing this potential, and Satellite currently does not show the
indications yet. Will put this at a 40% chance, and will leave it
out of the TAFS for now.

Then, tomorrow, higher clouds may filter in from the north, mostly
staying confined to Oregon. The bigger concern will be gusty
northwest to north winds 25 to 30 kts across most of Oregon and
California, impacting all terminals in the afternoon. Breezy winds
will are most likely to occur between 2pm and 11pm PDT. -Schaaf


&&

.MARINE...Updated 830 PM Friday, May 17, 2024...A thermal
trough pattern will maintain gusty north winds and steep to very
steep seas through the weekend. Seas will be highest south of Cape
Blanco around Brookings with waves reaching up to 10 to 12 feet and
around 5 to 7 feet near Florence and Coos Bay. Seas will be a
combination of fresh swell out of the northwest and some wind waves
moving through the waters. Seas will remain hazardous to small
crafts through the weekend and into early next week.  Waves will
subside to around 5 to 6 feet across all the waters around Tuesday
and Wednesday of next week.

-Schaaf/Smith


&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 PM PDT
     Saturday for PZZ350-356-370-376.

Hazardous Seas Warning until 11 PM PDT Saturday for PZZ356-376.

&&

$$