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000
FXUS66 KMFR 250341
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
841 PM PDT Wed Apr 24 2024

.DISCUSSION...Showers and thunderstorms have largely laid down for
the day and a period of calm is expected through the rest of
tonight. This will change Thursday morning as a front moves
onshore. Compared to winter standards, the front looks to be
fairly low impact, although a fresh coating of Cascades Concrete
(high density snowfall) is expected from 5500 feet and above,
which could disrupt some weekend plans for anyone hoping to enjoy
some sunshine in the mountains. Instead, be prepared for
subfreezing temperatures, snow, and wind gusts peaking around 35
kts, which may cause visibility restrictions during the peak
snowfall Thursday evening and night.

Away from the mountains, storm total rain amounts of 1 to 1.5
inches along the coast and in Douglas County, and less than half
an inch in most other places, should provide beneficial rainfall
that will keep water year totals around normal across the region.
The change in airmass will also trend afternoon high temperatures
back into the 50s across most of the region, which is more like
early March like temperatures.
-Miles

&&

.AVIATION...25/00Z TAFs...
Isolated thunderstorms remain ongoing across NorCal and east of the
Cascades. This activity should decline once the sun sets. With a
front expected to move in tomorrow, the current cloud cover will at
least remain the same or increase through the night; making terrain
obscuration more common. The front is expected to arrive tomorrow
afternoon. This front will bring rain to the whole region, including
east of the Cascades, but it is unlikely to be heavy enough to
restrict visibility.
-Miles

&&

.MARINE...Updated 800 PM Wednesday, April 24, 2024...Relatively calm
seas are anticipated tonight ahead of an approaching front which is
slated to come through Thursday afternoon.

By tomorrow, the approaching front will bring increased wind speeds
along the coast and rainfall chances. These wind speeds will create
conditions hazardous to small craft and we could see isolated gales
across the northern waters. Rainfall chances are very high around
90+% across the waters starting Thursday afternoon. The probability
of getting 0.25" or more of rainfall over 12hrs is around 40%-70%
for the inner waters Thursday afternoon through Friday morning. The
probability for wind gusts of 34 knots or greater is only around 20%-
30% and hence the thinking for low end chance of isolated gales,
mainly across the northern waters where the strongest wind speeds
are anticipated.

The biggest change for this forecast was to extend the small craft
advisory both earlier in time and later in time to account changing
conditions. We may need to consider adding in portions of the
southern waters for later in the week, but we can address this in
coming forecast.

We get a little bit of a break Saturday with calmer seas, but the
seas become active again starting Sunday and going into next week.
Additionally, this will be a rainy pattern with chances over the
waters essentially everyday tomorrow onward. The best chance for
rainfall at this time is the early period Thursday afternoon through
Friday morning.


&&

.PREV DISCUSSION... /Issued 513 PM PDT Wed Apr 24 2024/

SHORT TERM...Tonight through Friday night.

Scattered showers and isolated thunderstorms will continue into
this evening over eastern Siskiyou, Modoc, southern Lake, and far
southeastern Klamath counties. This includes the vicinities of
Alturas and Lakeview. A few light showers are also popping up
over the Cascades. This activity will diminish after sunset this
evening.

A significant change to cold and wet weather accompanies a frontal
system late tonight into Friday, and post-frontal showers Friday
into Friday night. High temperatures on Thursday will be around 5
to 15 degrees cooler than today`s readings, and a few additional
degrees of cooling on Friday.

-DW

LONG TERM...Saturday morning through Wednesday night.

Conditions trend drier around Saturday morning as a ridge sets up
over southern Oregon and northern California.  This should result in
a period of high pressure building and the chance of rain decreasing
around Saturday morning.  Some warmer moist air will push into the
forecast area ahead of the next cold front. This should lead to a
persistent light rain along the coast, although it will be drier
inland, especially east of the Cascades. Eventually, a cold front
will push into the region, although the PoP doesn`t change
much Saturday evening and Saturday night.

This cool unsettled flow will continue into Sunday with the best
chance of precipitation west of the Cascades and within Oregon.
However, locations east of the Cascades and in northern California
are anticipated to be dry.  This is most likely due to weak forcing
and a lack of moisture farther to the south under this zonal flow.
This synoptic pattern will likely continue into Monday as short
waves move through this zonal flow.

Eventually, an upper level low out of the Gulf of Alaska will likely
push into the Pacific Northwest around Wednesday. However, some of
the ensemble members keep this low offshore, which would result in
relatively drier weather around mid week. If the low does stay
offshore, then GFS does present a very interesting thunderstorm
event for the region with ample shear and the potential for building
instability. However, this forecast is 7 days away and pretty
unlikely with the evolution of the upper level low track.

Overall, the extended forecast looks active yet with little to no
impacts. We`re lacking significant moisture or forcing to bring
impactful rain or snow to the region.

-Smith

AVIATION... 25/00z ...

Isolated thunderstorms remain ongoing across NorCal and east of the
Cascades. This activity should decline once the sun sets. With a
front expected to move in tomorrow, the current cloud cover will at
least remain the same or increase through the night; making
terrain obscuration more common. The front is expected to arrive
tomorrow afternoon. This front will bring rain to the whole
region, including east of the Cascades, but it is unlikely to be
heavy enough to restrict visibility.
-Miles

MARINE...Updated 200 PM Wednesday, April 24, 2024...Relatively calm
seas are anticipated today and tonight ahead of an approaching
front which is slated to come through Thursday afternoon.

By tomorrow, the approaching front will bring increased wind speeds
along the coast and rainfall chances. These wind speeds will create
conditions hazardous to small craft and we could see isolated gales
across the northern waters. Rainfall chances are very high around
90+% across the waters starting Thursday afternoon. The probability
of getting 0.25" or more of rainfall over 12hrs is around 40%-70%
for the inner waters Thursday afternoon through Friday morning. The
probability for wind gusts of 34 knots or greater is only around 20%-
30% and hence the thinking for low end chance of isolated gales,
mainly across the northern waters where the strongest wind speeds
are anticipated.

The biggest change for this forecast was to extend the small craft
advisory both earlier in time and later in time to account changing
conditions. We may need to consider adding in portions of the
southern waters for later in the week, but we can address this in
coming forecast.

We get a little bit of a break Saturday with calmer seas, but the
seas become active again starting Sunday and going into next week.
Additionally, this will be a rainy pattern with chances over the
waters essentially everyday tomorrow onward. The best chance for
rainfall at this time is the early period Thursday afternoon through
Friday morning.

-Guerrero

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory from 5 AM Thursday to 2
     AM PDT Saturday for PZZ350-356-370-376.

&&

$$