856
FXUS66 KMFR 142106
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
206 PM PDT Sat Sep 14 2024

.DISCUSSION...Satellite shows cumulus building along the Cascades
with passing high/mid-level clouds. Today is a normal/near normal
afternoon with highs in the 70s and low 80s across southern
Oregon and Northern California. A cold front is passing that will
drop temperatures by tomorrow to be 10-15 degrees below normal!

The next system is crossing Alaska and will transverse south along
the Canadian border and will bring our next chance of rain tomorrow.
A drying trend is evident for areas west of the Cascades Sunday
morning and afternoon, so have decreased PoPs to show the lower
chance there. However, there is still the potential for drizzle/a
light shower in the waters north of Bandon so have a 20-40% prob in
these areas for Sunday. The rain along the Cascades will begin later
tomorrow morning and showers will develop east of the Cascades
through the rest of the day. The probability for seeing 0.25" of
rain from 5 AM Sunday to 5 AM Monday is highest east of the Cascades
in central Lake and central/southern Klamath counties at 60-80%.
Thunderstorm chances exist east of the Cascades at 10-20% Sunday
afternoon/evening with the highest points also being in central Lake
and central/southern Klamath counties. Showers will continue farther
east of the Cascades Monday afternoon with a slight chance of
thunder.

The next system moves in quickly Tuesday and will bring more rain
west of the Cascades than the Sunday system. The rain will move into
the coast Tuesday morning and will continue tracking inland through
the afternoon. Most of the rain will fall in the afternoon/evening
Tuesday. Rainfall amounts with the mid-week system could reach 0.50-
0.75" west of the Cascades into the coast (expect for the Rogue
Valley that could see less than a quarter of an inch), and then
overall less than a quarter of an inch east of the Cascades. After,
drier conditions are favored and temperatures return to near normal
through the end of the week.

&&

.AVIATION...14/18Z TAFS...VFR conditions prevail across much of the
area this morning. MVFR cigs linger along the coast north of Cape
Blanco with LIFR conditions impacting areas from Brookings
southward. These lower conditions are likely to persist through the
TAF period, though there may be a brief period of VFR conditions
this afternoon. Otherwise, high level cloud cover is streaming
across the region associated with a dry cold front and this will
persist through the evening.

Tonight into Sunday, an upper level trough will move into the
region, bringing increasing lower level cloud cover west of the
Cascades. Low end VFR cigs are expected to develop in West Side
Valleys between 15/03z-15/08z and terrain will likely become
obscured. /BR-y

&&

.MARINE...Updated 200 PM Saturday, September 14, 2024...Relatively
calm conditions will persist through the afternoon and into tonight.
Northerly winds will increase Sunday morning as an upper level
trough settles over the region. This will bring the return of steep
wind driven seas to areas south of Port Orford by early Sunday
morning. Northerly winds strengthen as the day progresses Sunday,
resulting in steep seas spreading north of Cape Blanco to all areas.
Additionally, very steep and hazardous seas will develop late Sunday
afternoon for areas from Gold Beach southward. These conditions will
persist through Monday night, then winds will ease and seas will
briefly lower through Tuesday.

This improvement will be short lived. A front will move into the
region on Tuesday bringing widespread precipitation and isolated
thunderstorms. Behind the front, gusty north winds and steep seas
return late Tuesday into Wednesday, likely bringing the return of
conditions hazardous to small craft. /BR-y

&&

.FIRE WEATHER...A moist northwest flow on the backside of the
departing upper trough is helping to keep the cloud cover around a
little longer than anticipated in Oregon. In northern Cal, clouds
are much less extensive. Cloud cover should dissipate early this
evening and moreso late this evening and tonight, especially east of
the Cascades. West of the Cascades, we could see stratus develop in
the Umpqua and Coquille Basin late tonight and lasting into at least
the mid morning hours Friday.

As mentioned mostly clear skies are expected east ofthe Cascades
tonight, and this will allow temperatures to drop off fairly quickly
after dark with near or below freezing temperatures late tonight
into tomorrow morning. Given this will be the first freeze of the
season and the fact the typical first freeze of the season in these
areas take place right around this time, a Freeze Warning and Frost
advisory has been issued in the event folks have any outdoor plants
will take the necessary steps to protect them.

Dry weather will continue Friday into Saturday with warmer
afternoon temperatures for the interior Friday. Saturday will be
cooler as an upper trough approaches the area along with increasing
cloud cover.

Another upper trough will drop in from the northwest later Saturday
night into Sunday bringing another round of showers for most of the
area. Showers will tend to develop sooner west of the Cascades
Sunday morning, then showers will pop up in most areas, including
east of the Cascades late Sunday morning and afternoon. Instability
will be marginal east of the Cascades and this in combination with
some PVA moving in from the west to southwest could be enough to
trigger isolated thunderstorms in southeast Klamath and Siskiyou
County, all of Modoc county and most of Lake County from mid
afternoon Sunday into early Sunday evening.

The upper trough will dig south of the area Sunday night into Monday
morning with weak ridging nudging in from the west. Meanwhile,
there`es pretty good agreement for wraparound moisture to impact
areas from the Cascades east and in northern California. These areas
could experience persistent, steady moderate rain for most of the
day Monday. Right now, the forecast rainfall amounts could get close
to an inch for eastern portions of Fire Zones 285 and southeast 625,
with up to 0.50 of an inch in central fire zone 285 and southeast
Fire zone 624. Meanwhile, precipitation will be more isolated the
farther northwest we go. For example showers could end up being more
isolated west of the Cascades and in the northwest part of the
forecast area.

A brief break in the action is expected Monday Monday night, then
another upper trough will drop south into the area Tuesday bringing
another round of precipitation, first impacting the westside
Tuesday morning, then east of the Cascades and northern Cal Tuesday
afternoon and Tuesday night.

Cool and unsettled weather is likely Tuesday night into Wednesday
morning with scattered showers likely. Showers will gradually
diminish Wednesday afternoon as the upper trough/upper low digs
south of the forecast area.

After Wednesday, there`s increasing evidence for upper ridging to
build back into the area with dry and warmer weather that could set
up by next Thursday and last into the following weekend. Stay tuned.
-Petrucelli

&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory from 5 PM Sunday to 5
     AM PDT Tuesday for PZZ350-356-370-376.

Hazardous Seas Warning from 5 PM Sunday to 5 AM PDT Tuesday for
     PZZ356-376.

&&

$$

ANH/MAP/MNF