160
FXUS66 KMFR 021129
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
429 AM PDT Thu May 2 2024

...New Aviation Section...


.AVIATION (12Z TAFs)...

Wind speeds along the coast have turned westerly with the front
moving inland now. This will lead to rain showers diminishing
through the morning hours with relief expected later today for
ceilings. In fact, VFR could become common across the region with
skies generally clearing through the afternoon and evening. North
Bend may be the exception here with MVFR sticking around. Timing
of MVFR and rainfall will be tricky this morning, but generally
looking at the "roughest" conditions this morning with noticeable
improvements later today.

&&

.PREV DISCUSSION... /Issued 326 AM PDT Thu May 2 2024/

DISCUSSION...The pattern continues to be progressive into the
next week, with several fronts bringing wet and cool weather with
brief dry breaks in between. The first system moves through
overnight today with light showers lingering into the evening,
followed by a stronger front Friday into Saturday. Showery weather
continues into next week, with another weak front moving through
Monday.

A broad precipitation shield associated with a frontal system is
moving quickly ESE through southwest OR. Radar returns are
indicating some pretty good areas of precipitation, with areas of
40-50 dbZ embedded in the main band. This front will pass through
the region early this morning, followed by light, scattered
showers which will bring on-and-off again precipitation for the
remainder of the day, mostly over the higher terrain. With
seasonably mild temperatures, snow levels will remain at or above
5,000 feet and snow restricted to the higher mountains.

After a brief break in the weather, the next front arrives Friday
and slowly pushes inland into Saturday. Similar to the frontal
system today, this front will move in from the west, resulting in
much less downsloping for western valleys than in other patterns.
Precipitable water associated with this front, however, will be
greater with a stronger inflow of moisture, resulting in greater
precipitation amounts. Rain amounts of a half inch or more are
almost guaranteed for almost all areas in southern Oregon and far
northern California, with up to 2 or even 3 inches of rain
possible along the coast.

Snow levels will initially be quite high at the beginning of the
event, rising to above 7,000 feet, before decreasing overnight
Friday into Saturday to 3,000 to 4,000 feet as the cold front
passes and precipitation becomes more intermittent/showery. This
will result in snow lowering down to area passes, including those
over the Cascades on Hwys 140 and 138 (where we`re expecting 3-6
inches early Saturday through early Sunday) and Siskiyou Summit on
I-5 (likely less than an inch). As road surfaces are still quite
warm, a lot of this will melt on paved surfaces, but lower
visibilities could still make travel over the mountains difficult.

Showery, on-and-off again precipitation continues late Saturday
into Sunday as low pressure lingers aloft. Shower coverage will
shrink and taper off through the day Sunday as the low moves SE
and another transient ridge moves into the area. Another front
moves in Monday, this one much weaker with the majority of light
to moderate precip falling over northwest portions of the region.
Snow levels will generally be 4,000 to 5,000 feet. Onshore flow
and lingering moisture will lead to light, scattered showers
continuing into Tuesday. About a third of models included in the
National Blend indicate periods of precipitation are possible into
the mid-week, but the outlook for the late week/following week is
for warmer, drier conditions per the Climate Prediction Center.
-CSP

AVIATION...02/06Z TAFs...Ceilings have lowered to MVFR along the
coast and just offshore and will likely lower to IFR as a front
reaches the coast. Even though the TAF at North Bend shows a prolong
period of IFR ceilings, it`s possible there could be brief periods
of MVFR ceilings after 15z.

Inland west of the Cascades, VFR ceilings will lower to MVFR late
tonight north of the Umpqua Divide, confidence on the timing of
lowering ceilings indicated in the Roseburg TAF could be delayed by
an hour or two. Medford is expected to remain VFR through the TAF
period, however the higher terrain will be at least partly obscured
towards 11z.

East of the Cascades, VFR ceilings will continue into tonight, then
MVFR will follow at Klamath Falls as precipitation moves in. Areas
of mountain obscuration are expected after 12z until the end of the
TAF period.
-Petrucelli

MARINE...Updated 230 AM Thursday, May 2, 2024...A weak front
will continue to move through the waters this morning with a modest
increase in short period west-northwest swell. A break later today
will bring calmer conditions this afternoon and evening; however,
the active pattern resumes Friday morning with rain over the waters
likely (90% - 100%) and small craft advisory conditions in place
through Saturday morning. Weak winds and a slight increase in short
period west-northwest swell dominated seas are expected during the
weekend with rainfall (no thunder) chances (60%-90%). The next in a
series of fronts is likely to arrive on Monday with conditions
hazardous to small craft possible Tuesday.
-Guerrero

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory from 8 AM Friday to 11
     AM PDT Saturday for PZZ350-356-370-376.

&&

$$