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Area forecast discussion 
National Weather Service Medford or
828 PM PDT sun Mar 29 2015

Short term...models remain on track with high pressure persisting
tonight into Monday...then a front approaching the coast Monday
afternoon and moving inland Monday evening and night. On Tuesday
this front will shift east and a cold upper trough will move into
place bringing a cold showery airmass to the area.

Tonight expect the only concern to be valley and coastal low
clouds and fog. Expect low clouds to move into the coast, mainly
north of Cape Blanco this evening...with models showing the low
clouds lingering into Monday morning. Inland expect partly cloudy
to mostly clear conditions with patchy valley fog possible in
western valleys, mainly in the Umpqua valley and in the Grants
Pass area. Guidance continues to indicate fog will be brief and
limited to the early morning hours Monday.

Then, ahead of the front late Monday afternoon into Monday evening
expect southwest to west winds to increase, especially over the
mountains and east of the Cascades. Winds gusting to around 20 to
30 miles per hour are expected for these areas. Precipitation is expected to
begin along the coast in the early evening Monday, then inland in
the late evening and overnight Monday. Models continue to show
mainly light precipitation with the front and snow levels
lowering from 8500 feet to around 5000-6000 feet with the front. The
upper trough moving into place Tuesday will bring lower snow
levels of 4000 to 4500 feet over the Cascades and western mountains,
and locally down to 3500 feet. East of the Cascades expect
slightly higher snow levels of 4500 to 5500 feet. This cold
unstable airmass on Tuesday will also bring the chance for
isolated thunderstorms, mainly to Coos and Douglas counties. Also
isolated heavier showers over northern portions County Warning Area may have
small graupel or ice pellets with them on Tuesday.


Aviation...for the 30/00z taf cycle...VFR conditions will persist
for the next 24 hours for inland areas except for brief IFR ceilings
in the Umpqua basin early Monday morning. Along the coast expect
VFR with areas of MVFR/IFR ceilings beginning this evening and
continuing Monday morning. Along the coast IFR is forecast to
clear to VFR in the late morning. -Petrucelli/cirrocumulus


Marine...updated 800 PM PDT Sunday 29 Mar 2015...high pressure
will persist over the waters into Monday morning then move east as
cold front approaches from the west Monday afternoon. A moderate
west swell will diminish late this evening. South winds will
increase Monday afternoon and evening ahead of a stronger cold
front...which will move onshore Monday night. At this time it
looks like seas will reach Small Craft Advisory criteria...but the
winds will remain just below small craft. High pressure will
briefly rebuild from the southwest Tuesday...then weak low
pressure will move into the waters Tuesday night. Offshore high
pressure will return Wednesday and Thursday. -Petrucelli/cirrocumulus


Previous discussion... /issued 243 PM PDT sun Mar 29 2015/

Short term...tonight through Wednesday night...warm, dry weather
will prevail late this afternoon and early this evening with just
some high clouds. With high pressure in control, expect clear to
partly cloudy skies overnight, though some low clouds and fog may
redevelop along the coast, the coastal valleys and in the Umpqua
basin. It should be a few degrees higher than it was this morning.

Monday will be the last warm day for a while. Most inland areas
will have temperatures similar to today...even a few degrees
higher east of the Cascades. A gusty breeze will develop in the
afternoon. The ridge responsible for the warm weather will shift
to the east...and west to southwest flow aloft will strengthen as
an upper level trough approaches from the Pacific. This system
will bring a major change in the weather pattern Monday night
through Wednesday.

A sharp cold front will reach the coast by Monday evening...and
move across the remainder of the area Monday night. Expect a
period of light to moderate precipitation with the front along
and west of the Cascades during this time. Snow levels will drop
very quickly from 8000-9000 feet Monday evening down to 4500-5000 feet
by Tuesday morning. Some light precipitation will accompany the
front east of the Cascades Tuesday, while west-northwest onshore
flow keeps moderate showers going along and west of the Cascades.
Gusty winds are also expected in many areas, though probably
remain just below advisory levels. The air mass is unstable enough
to support an isolated thunder threat from the northern coastal
waters across portions of northern Douglas County. Overall,
precipitation amounts will be 0.25-0.75 of an inch with snowfall
above 5000 feet of 1-3 inches. Some of the higher mountains could
see 3-6 inches.

Showers will diminish Tuesday night, but probably continue across
northwest sections of the cwa, mainly north and west of the Umpqua
Divide. If clouds break across northern California, we may need
to consider a freeze watch for the Shasta Valley.

Another strong short wave will dive down the back side of the
trough Wednesday with very cold air aloft (-30 to -33c at 500 mb).
Expect more showers to develop with the potential for
thunderstorms along and west of the Cascades. Since it will be so
cold aloft, any showers will have the ability to produce graupel.
Snow levels will be down to 3000-4000 feet, but with less
precipitation expected, snow amounts should be light. Expect
another cold night Wednesday night...though there should still be
enough cloud cover around the west side valleys in Oregon for
lows in the middle to upper 30s. Freeze potential exists again in the
Shasta Valley. Spilde

Long term...Thursday through Sunday...the short wave trough will
continue to push east of the Cascades throughout Thursday. Probability of precipitation will
be waning from the west with only slight chance across Coos County
and the Umpqua Divide. West-northwest flow will provide for upslope showers
into the Cascades and the Warners. East side could see snow showers
in the early morning but precipitation is expected to turn to rain
showers or mixed rain-snow by afternoon. Fairly cool min temperatures
look likely Thursday morning with some west side frost potential.
Then there is a fair potential for a period of short wave ridging
Thursday night through Friday. Clearing skies may allow min temperatures to
dip closer to freezing for the rural area of Rogue Valley Friday
morning. For next weekend...the past 12 runs of the GFS have
indicated a digging trend of a trough coming into the West
Coast Saturday. The European model (ecmwf) is a tad slower but still shows a trough
digging offshore. We're continuing to steer with the cooler forecast
for now. On the precipitation side, we're maintaining a slight
chance to chance probability of precipitation. Would have gone higher with probability of precipitation but the ec
solution would confine precipitation closer to the coast. /Fb


Mfr watches/warnings/advisories...


Pacific coastal waters...Small Craft Advisory for hazardous seas until 11 PM PDT this
evening for pzz350-356-370-376.



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