Area Forecast Discussion
Issued by NWS Medford, OR
FXUS66 KMFR 241609
Area Forecast Discussion
National Weather Service Medford OR
909 AM PDT TUE MAY 24 2016
.DISCUSSION...Morning low clouds will give way to partly cloudy
skies this afternoon for most areas. Shower chances will be
focused south and east of the Umpqua Basin with most of Douglas
and Coos Counties remaining dry today. There is enough instability
and moisture to keep a slight chance of thunderstorms in the
forecast for much of the CWA. There is a higher chance of
thunderstorms over Eastern Siskiyou, Modoc, and Southern Lake
Counties because of more instability per the model forecasts and
the observed clear skies leading to greater surface heating.
A solid push of marine air and clouds is expected tonight for
areas west of the Cascades as deep flow turns more onshore. This
will usher in a lot of the low clouds that are currently residing
over the Northeast Pacific waters per morning satellite imagery.
Please see the previous forecast discussion below for details on
this week`s forecast and the uncertainty of the weekend forecast.
We`ll be trying to resolve the low track this weekend to determine
how warm/dry it will be for Memorial Day.
.AVIATION...For The 24/12Z TAF Cycle...IFR cigs and vis will
continue over the Umpqua Basin through mid morning then burn off.
Elsewhere, conditions will remain generally VFR with patchy MVFR
cigs/vis this morning. Showers and isolated thunderstorms will
develop this afternoon, especially from the Cascades and Siskiyous
eastward. A marine push is expected tonight and will bring a mix
of MVFR and IFR ceilings to the coast and Umpqua Basin.
.MARINE...Updated 840 AM PDT Tue 24 May...As low pressure moves
inland today and high pressure to the northwest strengthens, north
winds will increase today and persist at least into early next week.
Winds will reach small craft advisory levels over the waters south
of Cape Blanco late Wednesday and remain at least that strong
through the remainder of the forecast period. Winds will peak,
possibly reaching gales, late this week into the weekend. Seas will
be wind driven with little contribution from swell, thus sea state
will closely follow wind conditions. Lighter north winds and sea
state will occur north of Cape Blanco. -BPN/Wright
.PREV DISCUSSION... /Issued 453 AM PDT TUE MAY 24 2016/
DISCUSSION...The GFS and ECMWF models have trended toward better
agreement into Saturday. Temperatures are expected to remain near
normal through Saturday. Today looks to be the most active day of
showers and thunderstorms of the next week...though it may have
competition for that honor from Sunday and/or Monday of the
holiday weekend if the pattern ends up closer to the GFS solution.
There is a slight chance of thunderstorms this afternoon and early
evening from the southern Oregon Cascades and Siskiyous southward
and eastward. There is good agreement between the GFS and SREF
models with the GFS indicating that the probability of
thunderstorms will be highest over far eastern Siskiyou County
while the SREF is focused a bit farther east...over Modoc County
extending into south central Oregon to around the vicinity of Bly
and Quartz Mountain on Highway 140.
The axis of the broad trough over the west will shift east of our
area Tonight with a ridge far offshore that will track closer to
the coast. A weak shortwave in a weak northerly flow aloft will
bring coastal low clouds Tonight into Wednesday and a slight
chance of light coastal showers north of Cape Blanco. The offshore
ridge may retrograde slightly on Thursday with the next upper
level trough forecast to move southeast into British Columbia.
This will send a very weak cold front into the Pacific Northwest
with a continued onshore flow...coastal low clouds and a slight
chance of light showers from Coos and Douglas County northward.
The weather on both Friday and Saturday is likely to closely
resemble the conditions from Thursday. The upper trough will
continue its relatively slow progression into Washington during
Thursday night into Friday then will likely linger into Saturday.
As mentioned above...model solutions have notable differences
between them for early next week and differences compared to their
12Z run of yesterday morning. We will maintain a broad brush
model blend at this early juncture. The models have trended toward
a less progressive though not stagnant longwave pattern. There is
a low to moderate confidence that temperatures will remain around
normal. The ECMWF solution is drier and warmer...highs would be a
few to several degrees above normal with an offshore ridge nudging
into the region and the trough axis with the threat of showers and
thunderstorms over the northern Rockies. Meanwhile...the GFS
solution suggests highs of a few degrees below normal to near
normal with another shortwave following the recent track south-
southeastward and forming a closed low before tracking across our
area with scattered showers and isolated thunderstorms Sunday
through Monday. The model solutions come back into phase next
Tuesday with the idea of a warming and drying trend.
Pacific Coastal Waters...None.