Area forecast discussion
National Weather Service Medford or
234 am PDT Thursday Jun 20 2013
Discussion...a broad upper level trough remains over the Pacific northwest. An
embedded short wave exited the area Wednesday afternoon which allowed
the atmosphere to stabilize ending the showers. Another weak short
wave trough will cross the area today bringing a slight chance of
additional showers to Coos and Douglas counties through tonight. The
Euro and GFS are in good agreement on these features as well as a
short wave ridge of high pressure for Saturday. This will allow
temperatures to jump around six to seven degrees.
The ridge breaks down Saturday night allowing the next trough to
approach the coast. Here the models begin to differ a bit. Both the
Euro and GFS bring a trough but the Euro is a bit deeper. I don't
think the difference is too significant. A cold front enters the
area Saturday night spreading rain across areas west of the
Cascades. The rain extends across the entire forecast area by Sunday
afternoon. The air mass becomes somewhat unstable east of the
Cascades Sunday afternoon with lifted indices right around zero but
the middle levels of the atmosphere don't cool appreciably so I don't
expect thunderstorms. Rather there should be showers. A bit farther
east of the forecast area the atmosphere will be more unstable and
favorable for thunderstorms.
A broad trough then settles in over the eastern Pacific putting the
Pacific northwest under a moist southwest flow. This will continue
the wet unsettled weather through Wednesday night.
Another item of note for this morning and Friday morning are the
cold temperatures east of the Cascades. A frost advisory is current
in effect for many parts of Klamath, lake, Modoc and NE Siskiyou
counties. The same areas will experience frost again Friday morning
so expect a second frost advisory to come during the day. Lovegrove
&&
Aviation...based on the 20/06z taf cycle.
Only isolated showers are expected this morning into this afternoon.
Along the coast MVFR ceilings are expected through the morning with
clearing to VFR around 17z to 19z. Although expect mainly VFR along
the coast this afternoon, some isolated MVFR ceilings may linger into
the the early afternoon. Then expect MVFR ceilings to redevelop along
the coast late Thursday evening. Inland, expect mainly VFR conditions
with isolated MVFR ceilings or mountain obscurations in showers this
morning especially in the Umpqua basin and over the higher terrain
along the southern Oregon Cascades...then mainly VFR this afternoon
and evening. Cirrocumulus
&&
Mfr watches/warnings/advisories...
or...frost advisory until 8 am PDT this morning for orz030-031.
Frost advisory until 8 am PDT this morning for orz029.
California...frost advisory until 8 am PDT this morning for caz084.
Frost advisory until 8 am PDT this morning for caz085.
Pacific coastal waters...Small Craft Advisory for winds from 2 PM to 11 PM PDT Friday for
pzz376.
Small Craft Advisory for hazardous seas from 2 PM to 11 PM PDT
Friday for pzz376.
$$
