Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 190423
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
923 PM PDT Wed May 18 2022

.UPDATE...
Updates to the forecast have been made and sent for winds and
precipitation potential for this evening through Thursday evening.

&&

.DISCUSSION...
Winds have been strong and gusty across much of the east side and
many of the mountains this afternoon and evening. Observations
from Crater Lake National Park indicate gusts around 40 mph, Grey
Butte on Mount Shasta near 8kft elevation is reporting gusts to
71 mph, the Summer Lake area saw gusts in the 50s, and many other
locations across Klamath and, especially, Lake County experienced
gusts 30 to 50 mph.

Winds began lifting off of the valley floors on the east side a
couple of hours ago, but the Summer Lake area is still seeing
gusts around 45 mph. We`re keeping the existing Wind Advisory for
portions of Klamath and Lake counties, including many valley areas
from Valley Falls northward out until 11 PM PDT. Thereafter, through
8 AM PDT (the advisory has been extended 6 hours), the Wind
Advisory there is for higher elevation areas, including a small
portion of Highway 31 near Summer Lake and parts of Highway 140
east of Lakeview. We`ve also added a Wind Advisory through 8 AM
PDT for the Warner Mountains area of Modoc County which could
affect Highway 299 at Cedar Pass some overnight into the early
morning.

Thursday`s highs will be around 10 degrees cooler than today`s
across inland areas south and east of the Umpqua Divide. The newer
model runs do indicate some precipitation potential generally
from around Roseburg and Union Creek northward Thursday
afternoon. Northwest winds will become gusty in the afternoon and
are likely to carry on well into the evening in many areas as
they become more northerly in direction.

Frost and freeze potential for Friday morning is still there for
many areas, but we`ll need to assess the effects of both clouds
and winds further before issuing any related headlines. ~BTL


&&

.AVIATION...19/00Z TAFs...Conditions are mainly VFR and this
will persist through Thursday. But, patchy MVFR is present this
evening from the coastal waters into the coast, Coquille Valley, and
Umpqua Valley. This will expand to areas of MVFR with mountain
obscuration from around 06Z late tonight into 15Z Thursday morning.
These conditions will gradually improve to VFR during the remainder
of Thursday morning. Also, gusty northwest winds will develop again
Thursday with the strongest winds east of the Cascades from Thursday
afternoon into the early evening. -DW

&&

.MARINE...Updated 800 PM PDT Wednesday 18 May 2022...Winds are at a
minimum this evening, but steep seas linger north of Cape Arago with
west-northwest swell dominated seas at 9 to 10 seconds. Offshore
high pressure and a thermal trough near the coast will return
Thursday, and strengthen through Friday evening. This will bring
gusty north winds and steep seas to the waters, with gales and very
steep seas possible south of Cape Ferrelo Friday afternoon through
Friday night. The thermal trough pattern is likely to persist
through the first half of next week with the strongest winds in the
southern portion of the waters. -DW


&&

.PREV DISCUSSION... /Issued 237 PM PDT Wed May 18 2022/

SYNOPSIS...A front will move through southern Oregon and northern
California this evening bringing some gusty winds and some cooler
weather to the area. Then, a ridge of high pressure will bring our
first thermal trough that we have seen for a while with conditions
turning drier and warmer beginning this weekend.

Potential Impacts:

*Breezy to Windy conditions east of the Cascades this afternoon
 and evening may make travel difficult for high profile vehicles.
*Dust may be picked up over some of our dry lake beds and could
 reduce visibilities this afternoon and evening.
*Overnight low temperatures have trended slightly lower for Friday
 morning. Frost formation may be possible west of the Cascades.
*Periods of breezy to strong winds and steep seas possible
 through the weekend. See the marine discussion for more details.

SHORT TERM...Tonight 5/18 through Friday night 5/20...Satellite
imagery is showing cloud cover across most of southern Oregon and
parts of western Siskiyou County. Meanwhile, the RADAR is showing
some returns, although it is unclear whether it is virga or if the
rain is reaching the ground. This is all part of a frontal
boundary that will be moving through the area this evening into
tonight. The biggest consideration with this frontal boundary will
be the winds ahead of the front, especially east of the Cascades.
Ensembles, including the NBM, as well as statistical guidance are
showing some gusty winds across the Summer Lake Area, Winter Rim,
and other portions of Lake County. A wind advisory remains in
effect for these areas through 2AM. Please see the NPWMFR for more
details.

Conditions will also gradually get cooler tomorrow as we remain
somewhat unsettled. Gradients--in particular the Medford to
Redding gradient is showing between 7.5 and 10.5 which is
relatively significant. If we were expecting south winds, we would
likely be issuing an advisory for the Shasta Valley for tomorrow
afternoon as well. That being said, winds are from the north, and
while breezy for areas east of the Cascades and for the Shasta
Valley, that pattern is not one that generally produces strong
winds. So have gone with more breezy winds in those areas.

Early in the week, we have been zeroing in on Friday as a
potential for frost formation on the West Side. Those temperatures
have been trending lower, and the NBM is now showing a 46% chance
for temperatures at the Medford Airport to be at or lower than 36
degrees-- which could promote frost formation. Rural areas in the
Rogue and Illinois Valley should prepare for frost formation at
this rate, and valleys in Siskiyou County may also consider the
possibility for frost/freeze conditions. Will continue to monitor
the temperatures, but held off on the frost advisory (since we
will have tomorrow to prepare) for now.

Then, conditions will begin to dry out on and warm up beginning
Friday as the upper low responsible for all of this moves away
from the area. For more information on the warming and drying
trend, see the long term discussion. -Schaaf

LONG TERM...Saturday, May 21 through Wednesday, May 25 2022...
The upper trough will gradually shift east and an upper ridge will
nudge inland Saturday into Sunday. Meanwhile, a surface thermal
trough will persist along the coast, with breezy to gusty north to
northeast winds.  With this pattern, expect mainly dry weather,
outside of a few showers possible on Saturday over the mountains
from the Cascades east with the exiting trough. There will also be a
trend towards much warmer temperatures for inland areas. At the
coast, a mild warm up is expected across southern Curry County as
well.  Breezy winds out of the north are expected in the afternoons
and evenings.

Early next week, ensembles indicate the upper ridge is likely to
remain in place with a front moving over the ridge Tuesday and
Wednesday. Models continue to show this will bring a slight chance
(15-20%) for light precipitation, mainly across portions of Coos and
northern Douglas Counties as well a into the South-Central Oregon
Cascades. However, the strength of the ridge will be a factor in how
much, if any, precipitation occurs as well as how warm temperatures
are during this period. -CC

AVIATION...18/18Z TAFs...Over the coastal waters, along the
coast, and in the Umpqua Basin...Areas of MVFR cigs/vsbys in low
clouds and rain with higher terrain obscured. Local IFR ceilings
and/or visibility are possible, especially north of Cape Blanco.
Precipitation will diminish this afternoon/evening, but the
MVFR cigs/vsbys and terrain obscuration will persist into Thursday
morning. Over the remainder of the area...VFR conditions will
persist through Thursday morning, but some higher terrain will be
obscured, especially from the Cascades west. Winds will be gusty
east of the Cascades this afternoon and evening. -Spilde

MARINE...Updated 200 PM PDT Wednesday 18 May 2022...Steep seas
persist into this evening, mainly north of Cape Arago. Offshore high
pressure and a thermal trough near the coast will return Thursday,
strengthen through Friday evening, then weaken Friday night into
Saturday. This will bring gusty north winds and steep seas to the
waters. Gale force winds and very steep seas are possible south of
Cape Ferrelo Friday afternoon into Saturday morning. -Spilde

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 8 AM PDT Thursday for ORZ030-031.

CA...Wind Advisory until 8 AM PDT Thursday for CAZ085.

Pacific Coastal Waters...
     Gale Watch from Friday afternoon through late Friday night for
     PZZ356-376.
     Small Craft Advisory from 8 AM Thursday to 2 AM PDT Saturday for
     PZZ356-376.
     Small Craft Advisory until 11 PM PDT this evening for
     PZZ350-370.
     Small Craft Advisory from 11 AM Thursday to 2 AM PDT Saturday
     for PZZ350-370.

$$

BTL/DW/BMS


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