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Area forecast discussion 
National Weather Service Medford or
801 PM PDT Friday Jul 25 2014

Discussion...today featured mostly sunny skies with temperatures
near normal for this time year. Temperatures will steadily climb
through Monday as ridging over the Desert Southwest builds
northwestward into southern Oregon and northern
California...bringing temperatures to about 10 degrees above
normal by Monday. Sunny skies are expected again on
Saturday...except at the coast where stratus will form later
tonight and clear out by late Saturday morning.

Please see the previous discussion below in regards to the threat
of thunderstorms entering the forecast on Sunday.



&&

Aviation...guidance suggest IFR ceilings developing at the coast after 8z
north of Cape Blanco. South of Cape Blanco, the offshore flow should
be sufficient enough to keep marine stratus offshore. Inland, VFR
conditions will continue for the next 24 hours. The NAM continues to
show MVFR ceilings developing in the Umpqua basin around 12z and
continuing to middle/late morning Saturday. However this model appears
to be too moist in the boundary layer based on current observations.
So have leaned towards the the lamp guidance which indicates VFR
conditions at krbg and the GFS model which shows only marginally
favorable moisture to support MVFR ceilings. Overall expect local MVFR
ceilings in the Umpqua basin early Saturday morning. /Cc





&&

Marine...updated 700 PM PDT 25 July 2014...a thermal trough
will persist over the southwest Oregon coast through at least
Monday resulting in high confidence in the marine forecast during
this time. This will result in moderate to strong north winds and
steep to very steep wind-driven seas. The strongest winds and
highest seas will occur in the outer waters south of Cape Blanco,
but may nudge into the southern inner waters at times in the
afternoons and evenings. Gales are expected beyond 10 nm from
shore south of Gold Beach today and tonight and will expand north
to areas from Port Orford south Saturday afternoon and
evening...then persist into Monday. Very steep hazardous seas will
accompany these gales for areas beyond 5 nm from shore south of
Cape Blanco during this period. North of Cape Blanco expect mainly
Small Craft Advisory winds and seas. The northerly winds may
weaken on Tuesday but then strengthen again Wednesday trough late
next week. /Cc



&&

Climate...interestingly...we are reaching the apex of daily
normal high temperatures...which is 93 at Rogue Valley
international Airport in Medford. This lasts through early August
before daily normal high temperatures begin to drop.



&&

Previous discussion... /issued 242 PM PDT Friday Jul 25 2014/

Discussion...heights continue to rise as the upper level ridge
builds over the Great Basin though Sunday. Temperatures are expected to
rise above 100 degrees in many west side locations Monday and
possibly Tuesday. As per the last stretch of hot temperatures have mixed
the layer down adiabatically from 700 mb top determine the high
temperatures Sunday and Monday rather than 850 mb temperatures which support a
much lower high temperature. By Sunday the upper high shifts east
with the upper low deepening offshore. This pattern brings a
southerly low level moisture flow into the region and a cooler air
mass aloft. 500 mb temperatures drop from -8 to -9c Saturday to -11
Sunday...and generally stay in the -9 to -11 range through Friday.
Confidence is not high with the convection as the moisture flow is
not strong and does not precede it for a long period of time...with
700-500mb relative humidity barely topping 60 percent over western Siskiyou
County and the northern east side Sunday afternoon. Monday's
confidence in convection is not much better with 700-500 relative humidity only
slightly higher...but instability is slightly higher. By Tuesday
Theta-E advection has persisted long enough to finally bring the
700-500 relative humidity above 80 percent with lifted indice's around -4 on the west side.
This will combine with a strong short wave moving through around
maximum heating on the east side and another slightly weaker short
wave moving in from the south on the west side where the strongest
instability is located. By Wednesday the area of instability
spreads to the coast with the GFS indicating lifted indice's lower than -5
over the west side with another strong short wave moving up from
the south around maximum heating. With due southerly 700 mb winds
around 10 knots and precipitable water values around 1.25 inches localized very heavy
rain may also be possible. This pattern looks to shift to the east
side Thursday with the same instability pattern remaining...but
the only short wave on the east side as a kicker and very weak
steering winds. As all of this is in the extended have left the
chances at slight chance and will walk the probability of precipitation up as we approach
if the model solutions remain the same.

&&

Mfr watches/warnings/advisories...
or...red flag warning until 8 PM PDT this evening for orz620.

California...none.

Pacific coastal waters...Small Craft Advisory for winds until 11 PM PDT Monday for
pzz350-356-370-376.
Small Craft Advisory for hazardous seas until 11 PM PDT Monday
for pzz350-356-370-376.
Hazardous seas warning until 11 PM PDT Monday for pzz356-376.
Gale Warning until 11 PM PDT Monday for pzz376.

$$

Nsk/sbn/cc

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