Area forecast discussion
National Weather Service Medford or
906 PM PDT Wednesday Jun 19 2013
Short term...a broad upper low remains over the region this
evening with the upper low center near far northeast Oregon and
eastern Idaho. Some light scattered showers remain mainly over
the higher terrain along and west of the southern Oregon Cascades
with a few showers elsewhere. Expect showers to continue to
diminish tonight into Thursday morning as the main upper low lifts
northeast. The upper low is bringing cold air aloft and this
combined with partial clearing east of the Cascades is expected to
bring areas of frost to east side locations. Have issued a frost
advisory for these locations...see pdxnpwmfr for details.
The broad upper low will remain over the region Thursday and
models show a shortwave moving into southern Oregon Thursday
afternoon and evening. The GFS and European model (ecmwf) agree well on the timing
of this shortwave. The NAM though is slower and does not bring the
shortwave into the area until Thursday evening. Overall expect a
chance for light showers to develop Thursday afternoon into
Thursday evening, mainly for the coast into Douglas County and
over the southern Oregon Cascades. As the shortwave moves east
during the evening expect a slight chance for showers east of the
Cascades as well, mainly for the mountains. Otherwise expect most
areas to see dry conditions and mild temperatures tomorrow. The
upper low will persist over the region into Friday, gradually
shifting east late Friday with weak high pressure building inland.
&&
Aviation...showers are tapering off this evening with only
isolated terrain obscurations and isolated MVFR ceilings. The air
mass will begin to dry out tonight with VFR in most areas. But,
MVFR ceilings and areas of light showers will linger at the coast
into the Umpqua basin overnight. Skies are expected to improve to
VFR in the Umpqua basin by 18z Thursday morning, but MVFR is
expected to linger into early afternoon at the coast.
&&
Previous discussion... /issued 304 PM PDT Wednesday Jun 19 2013/
Short term...numerous showers continue this afternoon over
southern Oregon. Much less shower activity as you cross the border
to California. Cloud tops with these showers are not too
impressive but there could by a stray lightning strike with a
shower through sunset. The upper level low responsible for these
showers is basically centered over Oregon. Several bands of energy
rotating around this low will act to slow down the eastward
progression of this low pressure system. Thus...chance for showers
will continue through late Thursday with the best chances
retreating northward as time progresses.
A weak ridge moves over the area Friday into Saturday as the next
trough begins to develop offshore.
Long term...models depict another trough moving onshore Sunday and
then over the entire forecast area Monday and Tuesday. Much
uncertainty about the strength of this system but latest model
runs have become more bold with it. Thus have trended forecast for
the wetter and cooler conditions in all areas.
&&
Mfr watches/warnings/advisories...
or...frost advisory from 2 am to 8 am PDT Thursday for orz030-031.
Frost advisory from 2 am to 8 am PDT Thursday for orz029.
California...frost advisory from 2 am to 8 am PDT Thursday for caz084.
Frost advisory from 2 am to 8 am PDT Thursday for caz085.
Pacific coastal waters...none.
$$
Cirrocumulus
