Area Forecast Discussion
Issued by NWS Medford, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
FXUS66 KMFR 291531

Area Forecast Discussion
National Weather Service Medford OR
831 AM PDT SUN MAY 29 2016

.Update...Other than some high level thin cirrus moving across
the area, cloud cover is limited to Coos county and far western
Douglas county. Onshore winds will keep this area of clouds in
place for much of the day, but coverage should decrease as daytime
warming continues through the morning and into the afternoon. Have
made adjustments to the forecast to account for this, and also to
trim back the chance of drizzle to the upwind side of the coastal
range. Otherwise, the forecast appears on track.

For more information, see the previous discussion below. -BPN


.Aviation...For the 29/12Z TAF cycle...Areas of stratus with MVFR
cigs has spread into the Coos coast (including KOTH).  We may see
local IFR cigs with drizzle this morning at the Coos County coast
but not at Curry County coast. Elsewhere, VFR conditions will
continue through the TAF period. /CC


.Marine...Updated 825 AM PDT Sun 29 May 2016...Small craft
conditions will continue over portions of the southern waters due to
the presence of the thermal trough, which will strengthen again late
this afternoon and evening resulting in an increase in winds and
seas, especially from Cape Blanco south. Winds will increase further
across all the coastal waters on Monday. In the late afternoon and
evening, gusts could occasionally approach Gale, especially south of
Gold Beach beyond 10 nm from shore. Winds and seas are forecast to
lower on Tuesday. -CC


.Fire Weather...Next week will be warm and dry with a rapid warming
from Tuesday onward. Confidence is high that the valleys west of
the Cascades will see high temperatures in the 95 to 100 degree
range as the thermal trough shifts inland and remains west of the
Cascades on Tuesday and Wednesday. Expect minimum relative
humidity for western valleys to be in the mid teens with fair to
poor recovery Tuesday night and Wednesday night. The thermal
trough is expected to shift east of the Cascades Wednesday but
any onshore push will be confined mainly to Douglas County of

Around Wednesday we will have to contend with thunderstorm chances
as southerly flow aloft strengthens and allows more moisture and
instability to spread north. Right now we see only the higher
terrain such as the Cascades/Siskiyous, Marble Mountains, the
mountains of the Fremont-Winema Forest as the most likely area to
see lightning strikes. Confidence is not high on how much rain
these storms will produce. By Friday, instability appears to be
shunted to central California and we have removed thunderstorm
chance from the forecast. Hot temperatures inland will continue
into the end of the week. /FB


.PREV DISCUSSION... /Issued 248 AM PDT SUN MAY 29 2016/

Discussion...A weak cold front and upper trough will swing
through the area today. This is deepening the marine layer along
the coast and NASA/SPoRT nighttime microphysics RGB imagery is
showing that marine stratus has moved into areas from Cape Blanco
northward to the lower Umpqua Valley. Stratus will infiltrate the
rest of the Umpqua Valley through the morning and there could be
a bit of drizzle here or there. But, we`re not expecting much
more than a hundredth or two north and west of Roseburg. Stratus
will tend to break up this afternoon north and west of the Umpqua
Divide, becoming more stratocumulus/cumulus as the stable marine
BL mixes. The front won`t be that noticeable across the rest of
the area since conditions won`t change much compared to yesterday.
Expect sun and some high clouds, a gusty north to northwest
afternoon breeze and temperatures very similar to Saturday.

Tonight into Memorial Day, a strong ridge will build just off the
West Coast, then move into northern California Tuesday and into
the Great Basin on Wednesday. This will bring a rapid warm-up with
temperatures reaching the upper 80s here in Medford Monday, then
into the mid or even upper 90s Tuesday and Wednesday. The warmest
day along the south coast will likely be Monday as offshore flow
will be strongest then due a thermal trough extending northward
from northern California into SW Oregon. The thermal trough never
really extends far enough north to bring warm air to the north
coast, but it should be a bit milder there on Tuesday. It should
be noted that during this time frame, there will be significant
mid slope and ridge top drying over the Coast Ranges due to the
offshore flow.

The thermal trough will move inland Tuesday night into Wednesday
and cooling will commence at the coast, where some patches of
stratus may develop by Wednesday morning. Wednesday will be a
very warm to hot day inland. Models are showing some moisture in
the 700-500mb layer from western Siskiyou county up along the
Cascades and portions of the east side Wednesday afternoon and
evening. We have a slight chance of thunderstorms in the forecast
for these areas then.

Model solutions have come into agreement that strong ridging will
remain over the Great Basin Thursday through Saturday with an
upper level low off the California coast. This will put SW Oregon
and northern California in a south to southwest flow aloft. It
will take quite some time for Pacific systems to break down this
ridge and the upper level low off the CA coast will also be very
slow to move. So, it will remain quite hot over inland areas with
an extended stretch of 90+ degree heat continuing for the west
side valleys. Isolated storms may develop over the Sierra at times
during this time frame, but most likely will dissipate before
reaching our area, so much of the area will also remain dry. It
probably won`t be until next Sunday that we see any appreciable
shower/thunderstorm chances. Spilde


.MFR Watches/Warnings/Advisories...


Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT Monday for PZZ356-376.
     Small Craft Advisory from 2 PM this afternoon to 11 PM PDT
     Monday for PZZ350-370.
     Hazardous Seas Watch from Monday afternoon through Monday
     evening for PZZ376.
     Hazardous Seas Warning from 2 PM this afternoon to 11 PM PDT
     this evening for PZZ376.


BPN/MAS/FJB is the U.S. government's official web portal to all federal, state and local government web resources and services.