Area forecast discussion
National Weather Service Medford or
846 am PDT Wednesday may 22 2013
Short term...an upper low will remain over the area today through
Friday. This low will gradually fill and the air mass will
gradually warm. Continued moisture and shortwaves will move into
the area over the next few days and bring showers. The preferred
area for shower activity will be across the coast and the Umpqua
as well as the southern Oregon Cascades with areas of showers
moving into other west side locations and east of the Cascades at
times.
Satellite imagery shows another shortwave off the southern Oregon
coast this morning. Models are indicating this area of showers will move
inland and bring showers to the coast and Umpqua this morning
then showers will spread further inland across the west side and into
some east side locations this afternoon. Some of the showers may
bring small hail and gusty winds this afternoon. Also models are
depicting marginal instability in Northern Lake County. Expect
mainly scattered showers to develop there but will monitor for
chance of thunderstorms later this afternoon.
Shower activity is expected to continue into the evening for many
locations with showers decreasing overnight. Cold overnight
temperatures are expected again tonight into Thursday morning.
Skies will likely stay cloudy overnight with some partial clearing
inland during the morning. Temperatures Thursday morning will
likely be similar or just a couple degrees warmer than this
morning.
Then another round of increased showers activity is expect during
the day Thursday into Friday as another significant shortwave
moves inland.
&&
Aviation...widespread MVFR ceilings will continue at the coast with
occasional lift to VFR in the afternoon. However MVFR ceilings will
return again at the coast tonight. Inland...VFR conditions are
expected to prevail today. However temporary MVFR conditions with
partial mountain obscurations are possible near and within rain
and snow showers with locally gusty winds.
&&
Previous discussion... /issued 305 am PDT Wednesday may 22 2013/
Discussion...the upper low that brought much cooler
temperatures...rain and mountain snow showers including some
accumulating snow near Crater Lake and Diamond Lake yesterday will
linger over the forecast area for the next couple of days. The upper
low will weaken and move northeast Friday and Saturday.
Plenty of cold air aloft is moving overhead as evident by the
satellite image which shows plenty of cumulus clouds over the ocean
and are moving southeast into southwest Oregon. Of note is some
enhancement northwest of North Bend...so we can expect showers to
increase over the northwest part of the forecast area early this
morning. Snow levels start out around 2800 feet early this morning
and could briefly drop to around 2500 feet in heavier showers.
However due to warm Road and ground temperatures i'm expecting wet
snow showers to melt. The exception will be around Diamond and
Crater Lake and Lake of The Woods where a trace to an inch of slushy
snow could accumulate prior to 8 am PDT. Anything after that should
melt with snow levels expected to rise between 4000 and 4500 feet in
the afternoon.
The upper low remains overhead today with multiple shortwave
rotating around it along with cold air aloft. Therefore we can
expect almost a repeat of yesterday where showers will tend to
increase from late morning through the afternoon. Some of the
showers will bring locally gusty winds and small hail from about middle
afternoon into early this evening.
Showers will decrease some Wednesday night...but do not expect much
clearing to take place west of the Cascades and temperatures will
remain above freezing. It will be a close call in the Klamath basin.
There is a chance for less cloud cover there and any clearing will
allow temperatures to drop quickly. So we'll play it safe and issue
a freeze watch for late tonight/early Thursday morning.
The upper low lingers over the area Thursday with shower activity at
a minimum in the morning then increasing again in the afternoon. The
NAM and GFS show a stronger shortwave swinging into southern Oregon
in the afternoon. This along with increasing daytime heating could
be enough to generate isolated thunderstorms east of the Cascades
late in the afternoon and early evening.
Another shortwave is expected to swing into western Oregon Friday
morning...then move northeast Friday afternoon. So we can expect
another round of showers with a slight chance of isolated storms
east of the Cascades Friday afternoon. -Petrucelli
&&
Mfr watches/warnings/advisories...
or...freeze watch from late tonight through Thursday morning for
orz029.
Freeze warning until 9 am PDT this morning for orz029.
California...freeze watch from late tonight through Thursday morning for
caz084.
Freeze warning until 9 am PDT this morning for caz084.
Freeze warning until 9 am PDT this morning for caz081.
Pacific coastal waters...Small Craft Advisory for hazardous seas until 11 PM PDT this
evening for pzz350.
Small Craft Advisory for hazardous seas until 5 PM PDT this
afternoon for pzz356.
Hazardous seas warning until 11 am PDT this morning for pzz376.
Small Craft Advisory for winds until 5 PM PDT this afternoon for
pzz370.
Hazardous seas warning until 5 PM PDT this afternoon for pzz370.
$$
Cirrocumulus
