979
FXUS66 KMFR 302153
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
253 PM PDT Thu May 30 2024

.DISCUSSION...Satellite imagery shows only the slightest scraps of
cirrus clouds moving over northern California and southern Oregon
this afternoon. A building upper level ridge will generally keep
skies clear and bring warming temperatures across the area today and
Friday. Today`s highs will be very near seasonal norms. The Oregon
coast will be in the low to mid 60s today, with the exception of
Brookings. The Chetco effect is already clear today, with an
observed temperature of 78 degrees already. West side valleys will
be in the high 70s to low 80s, and areas east of the Cascades will
generally be in the low to mid 70s. Friday`s highs are forecast to
rise another 5 to 10 degrees over inland areas. Then an upper trough
will push the ridge to the east, bringing Saturday`s temperatures
back down to seasonal levels.

Precipitation chances are generally slim to none through Saturday,
although slight (~5%) thunderstorm chances remain in small areas.
Model guidance has these chances in place in southern Siskiyou
county on Friday afternoon and in eastern Lane and Modoc counties on
Saturday afternoon.

On Sunday morning, a cold front will use moisture from an
atmospheric river to bring substantial rainfall over the area that
will continue through Monday morning. Coastal areas will see the
highest rainfall totals, with cities forecast to get 1.5 to 2 inches
of rain while the coastal ranges in Curry and Coos counties could
see 2 to 3 inches of rainfall. Northern Douglas and inland Coos
county will see between 0.5 and 1 inches of rainfall. Other areas
will see lower amounts of rainfall. This front will also bring gusty
(but non-advisory) winds to east side areas, especially over
elevated terrain.

This event is definitely impressive, with precipitable water amounts
in the 99.5th percentile per NOAA ensemble tables. While no specific
hazard products are currently being issued for Sunday and Monday,
localized water flow or ponding is not impossible. This is
especially true in urban areas. Extra caution is encouraged while
traveling, especially along the Oregon coast or over higher terrain.

Conditions beyond Monday`s front remain uncertain. Both ECMWF and
GFS deterministic patterns show an upper ridge, but the placement
varies. The ECMWF outcome puts Oregon squarely under a large ridge,
while the GFS model puts the area near the back of a slightly weaker
ridge. The uncertainty is reflected in ensemble meteograms for both
long-term models, with a mix of precipitation and dry outcomes failing
to indicate any clear signal. The NBM is also showing uncertainty,
with interquartile ranges of 10 to 15 degrees in daytime highs from
next Wednesday and beyond. For example, Medford has a 45% chance of
seeing 100 degrees next Thursday, but could also see temperatures
as low as 91. -TAD


&&

.AVIATION...30/18Z TAFs...VFR conditions prevail over the region and
are expected to persist through the day. Northerly winds will pick
up again this morning and afternoon, and gusts could reach 20-25 kts.

Some low clouds could form in the valleys of Coos and western
Douglas County, but are not expected to impact the North Bend or
Roseburg terminals.
-Miles

&&

.MARINE...Updated 145 PM Thursday, May 30, 2024...A thermal trough
will peak this evening, and persist through at least Friday evening;
resulting in gale force winds for most areas south of Cape Blanco
and for isolated instances across the waters between Bandon and Cape
Blanco. Meanwhile, small craft conditions exist north over the rest
of the waters and will last into at least Friday evening.

The thermal trough will weaken overnight Friday into Saturday and
north winds will diminish as an upper trough approaches. Calmer seas
are expected on Saturday after the wind waves have diminished.

Sunday, a front with the energy more similar to a late winter/early
spring front will move through the region. Gusty (20-30 kt) south
winds will exist ahead of and along the front, while behind it, a
moderate west swell (7-9 ft around 10 sec) will build into the
waters. The result will be a period of at least advisory conditions
from roughly Sunday evening through Monday evening, along with rainy
conditions.
-Miles

&&

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

PACIFIC COASTAL WATERS...Gale Warning until 11 PM PDT Friday for
     PZZ356-376.

Small Craft Advisory until 11 PM PDT Friday for PZZ350-370-376.

&&

$$

TAD/JWG/MCB