546
FXUS66 KMFR 031208
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
508 AM PDT Mon Jun 3 2024

.Updated Aviation Discussion.

.SHORT TERM...A very moist cold front associated with an
atmospheric river is moving inland across the area this morning.
This front is located just west of the Southern Oregon Cascades
and rain has spread inland across areas from the Cascades west
and is spreading into portions of the east side. 24 hour Rainfall
totals along the coast have been between 1 and 2 inches, with
heavier amounts of 2 to 4.5 inches in the coast ranges. Inland,
rainfall of 0.3 to 1 inches has been observed overnight in
northern Douglas County, the Southern Oregon Cascades and
southwest Josephine County with lighter rainfall observed
elsewhere. Slick roads from layers of water or from oils brought
to the surface are possible hazards and are worth being aware of.
Urban ponding is also a possibility, especially in areas with poor
drainage or accumulated debris. This front will shift eastward
early this afternoon, with rainfall tapering off over the area.

Gusty west to southwest winds are also occuring with this frontal
passage. Winds have increased across the mountains and higher
terrain (gusts 30 to 45 mph) with strongest winds from the
Cascades east. A Wind Advisory is in place for parts of Lake
County expected to see the strongest winds, including the Winter
Rim, Christmas Valley, and areas east of Adel. This Advisory is in
place through 5 PM this afternoon. Please see NPWMFR for more
details. Breezy to gusty winds will also develop across inland
valleys later this morning into this afternoon, especially for
valleys east of the Cascades.

A weaker front moves inland north of the area. This will bring a
chances (10-30%) for light rainfall along the coast (mainly from
Cape Blanco north), over far northern Douglas County and the
south-central Oregon Cascades. Elsewhere, expect dry weather on
Tuesday. Inland, temperatures will warm on Tuesday, with west
side valleys forecast to reach the upper 70s to mid 80s and areas
east of the Cascades will be in the mid to high 70s.


&&

.AVIATION...02/12Z TAFs...Along the coast and just offshore, MVFR
and IFR conditions are the predominate condition this morning and
this is expected to persist through at least 18z, followed by
improving ceilings in the afternoon. Although could not rule out
brief periods of MVFR ceilings along the south coast past 18z.
Ceilings will lower early this evening with MVFR conditions expected
to be the predominate condition.

Inland west of the Cascades, MVFR ceilings will prevail for most of
the morning with the terrain obscured north of the Umpqua Divide.
Elsewhere, VFR ceilings are expected, although could not rule out
brief periods of MVFR ceilings with rain until 16z, and the terrain
will at least remain partly obscured until 18z.

East of the Cascades, VFR ceilings are expected through the TAF
period, but it could be a close call at Klamath Falls between 16 and
19z, with the terrain partly obscured and ceilings lowering towards
3000 feet. Moderate to occasionally strong winds are likely in the
afternoon, especially over the higher terrain. Peak wind gusts could
push towards 30 kts at the Klamath Falls terminal this afternoon.
-Petrucelli

&&

.MARINE...Updated 200 AM Monday, June 2, 2024...Winds will diminish
early this morning. With winds diminishing, seas will become less
steep as the wind driven component no longer exists, but seas will
remain steep as a 8 to 10 foot west swell moves into the waters
during the day. Seas will likely remain hazardous to small craft
through Tuesday as southerly winds briefly increase again ahead of
another, weaker, cold front.

Another west swell around 10 to 12 ft at 14 to 15 seconds will build
into the waters late Tuesday into Wednesday and combine with some
stronger northerly winds on Wednesday and Thursday as weak thermal
trough develops. Overall, conditions hazardous to small craft will
likely continue through the week. -Petrucelli


&&

.PREV DISCUSSION... /Issued 221 PM PDT Sun Jun 2 2024/


LONG TERM...Wednesday through Sunday...

BY Wednesday morning, upper level ridging will have built in over
the western half of the country, bringing an end to the slight chance
of showers over the northern portions of the area. By Wednesday
evening, however, the ridge will shift slightly to the east, with
the main ridge axis extending north along the Rocky Mountains from
Mexico. Meanwhile, a closed low is expected to develop just west of
Baja California, creating a conduit for warm, moist air to feed
north from the tropics and into portions of southern Oregon and far
northern California. This pattern is then forecast to remain
relatively similar through the rest of the week and into the week,
before breaking down under pressure form the next approaching trough
over the weekend.

All of this will result in a very warm forecast for the area, with
inland high temperatures of around 15 to 20 degrees above normal for
early June. Some of our warmer spots, such as the Rogue Valley and
the valleys of Siskiyou County, may even touch on the triple digits
Friday and/or Saturday. Most coastal areas will be warm as well,
although not quite as warm as the inland areas, with the exception
of a very warm Bookings, where a Chetco effect is expected to
develop along with the thermal trough, and high 80s or low 90s are
quite possible Wednesday and Thursday. One thing could significantly
limit how hot highs will be late in the week: clouds.

With the moist inflow form the south, we will also be concerned with
a daily threat of afternoon and evening thunderstorms, or even
overnight thunderstorms, as some models suggest and the pattern
would support. The main area of concern for convection will be
northern California and areas along and east of the Cascades, where
moisture will be most abundant and lifting mechanisms will be
strongest, but we can not rule out a stray storm or two making it
over to the West Side. Wherever the storms may be, clouds are likely
to spread over much of the area, and these will be the wild card in
terms of how high the highs get throughout the rest of the week.

Late this weekend or early next week, another trough approaches the
area from the west, putting pressure on the ridge and Baja low,
shifting them to the east. However, the exact nature of this trough
is very uncertain, with a wide range of possibilities across the
model suites. There does seem to be two major possibilities. The
first would be a trough that simply replaces the previous one off of
Baja, while the ridge remains in control overhead, and this would
result in continued warmth and keep us under threat of convection.
The other solution has the trough arriving later, but fulling
eroding the ridge, allowing for a brief cooling trend and reducing
the threat of convection, at least temporarily. Hopefully the model
suites can come to a better consensus on the forecast, but this may
take several cycles given the known difficulty models have with
closed low scenarios. -BPN

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 5 PM PDT this afternoon for ORZ031.

CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory from 5 AM early this
     morning to 5 AM PDT Tuesday for PZZ350-356-370-376.

&&

$$

CC/CC/CC