FXUS66 KMFR 311135
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
435 AM PDT Fri May 31 2024

...Updated AVIATION discussion...

.SHORT TERM...Warm and dry weather is expected today as a ridge of
high pressure remains over the area. High temperatures will be
around 10 degrees above normal across inland areas with highs in
the 80s west of the Cascades and in the upper 70s to low 80s for
valley east of the Cascades. On Saturday, expect temperatures to
trend slightly cooler as a weak upper level shortwave moves into
the area. This will bring increased cloudiness along with breezy
to gusty afternoon winds to the area (although, highest winds are
expected from the Cascades east and in the Shasta Valley with
gusts of 25 mph). Moisture  is limited with this disturbance. So,
expect mainly dry weather on Saturday, except for a low chance
(10%) for light rain or drizzle along the coast from Cape Blanco
north.

A stronger and moister frontal system will approach the area
Sunday morning, then move inland during the day Sunday through
Monday morning. This front is associated with a moderate to strong
moisture plume (precipitable water amounts in the 99.5th
percentile per NOAA ensemble tables) and is expected to bring
substantial rainfall to the area, with highest amounts along the
coast, over the coastal mountains and Cascades. Coastal cities in
southern Oregon may see rainfall totals of 1.0 inches or more
(40-60% chance) while the coastal ranges in Curry and Coos
counties could see 1.5 inches of rainfall more higher (and locally
up to 3 inches). Northern Douglas County, inland Coos County and
the southern Oregon Cascades (mainly north of Highway 140) may see
between 0.5 and 1 inches of rainfall. Other areas will see lower
amounts of rainfall. Localized water flow or ponding is possible,
especially for urban areas that receive heavier rainfall. Extra
caution is encouraged while traveling, especially for areas along
and near the Oregon coast. Temperatures on Sunday and Monday are
expected to be close to seasonal normals and breezy to gusty
afternoon/evening winds are expected, especially on Monday for
areas from the Cascades east.


&&

.PREV LONG TERM DISCUSSION... /Issued 253 PM PDT Thu May 30 2024/

.LONG TERM...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...31/12Z TAFs...VFR conditions will continue across
northern California and southern Oregon through much of the TAF
period under stable atmospheric conditions. Gusty northerly winds
along the Oregon coast will increase this afternoon before calming
this evening. Marine stratus may develop early Saturday morning, but
the timing will be more clear with the next update. -TAD

&&

.MARINE...Updated 200 AM Friday, May 31, 2024...A thermal trough
will continue to bring chances of northerly gale winds to waters
south of Cape Blanco today, with the highest chances within 30 nm of
the coast. Steep seas are expected to continue in all other waters.
A continuing Gale Warning for southern waters and a Small Craft
Advisory for northern waters will remain in place through 11 PM
tonight. Some localized areas of steep seas may remain after 11 PM
between Brookings and Crescent City, but not with enough consistency
to require any additional hazard products.

A weak upper trough moving over the area will help to break the
thermal trough up early Saturday morning, starting a period of calm
seas. Winds will turn westerly but remain light, and precipitation
chances from this trough are in the single digits for waters north
of Cape Blanco.

A more impactful front will arrive on Sunday morning, bringing
elevated westerly winds and fresh swell. Wide areas of steep seas
are expected on Sunday, but the timing and exact areas will benefit
from additional information. Moderate to heavy rainfall will be
possible Sunday evening into Monday morning, especially over all
waters within 10 nm from shore as well as outer waters north of Cape
Blanco.

Active seas continue behind the front, with current long term
guidance expecting long period westerly swell to enter area waters
on Wednesday morning. Present outcomes suggest seas of 9 to 12 feet
at 10 to 13 seconds will be built through Wednesday and Thursday.
Additionally, a thermal trough may return next Thursday. Confidence
in the trough development is minimal given current uncertainty in
atmospheric conditions so far out, but the chance is worth
mentioning to communicate the expectation of further chaotic seas
through the end of next week. -TAD


&&

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

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

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

&&

$$

CC