Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Medford or
100 PM PST Wednesday Mar 4 2015
Discussion...04/12z NAM/GFS in.
Mostly clear skies prevail this afternoon across the Medford County Warning Area.
On the global scale...the wave number is a bit difficult to
determine...but it looks like a 3-4 wave pattern around the
northern hemisphere. This would argue for a slow progression or
stationary pattern around the Globe. Over time this pattern
changes little...remaining a 3 to 4 wave pattern through the week
with the coldest air generally retreating towards the pole. Looks
like a seasonal change in the making.
Currently a long wave ridge remains offshore along 14ow with dry
northerly flow aloft over the Pacific northwest. The ridge will
move slowly west into Thursday while slowly weakening. This may
allow some high level moisture to move over the ridge...but that
will just bring some high clouds to the area. Expect dry
conditions to continue with a gradual warming trend inland...along
with some morning fog in the west side valleys. Marine stratus
will likely surge northward along the coast Thursday into Thursday
night...but the marine inversion will remain low due to subsidence
aloft and the low clouds and fog will be limited to the offshore
waters and coastal areas.
The ridge will become stationary along the West Coast and
strengthen Thursday into the weekend...then weaken in place Sunday
into Monday before moving off to the east next Tuesday. Expect the
dry conditions and warming trend to continue through the weekend.
Overnight lows will be slightly above seasonal normals by this
weekend...but inland highs will be 10 to 15 degrees above normal
by that time.
Tuesday is when the next chance of precipitation creeps into the
forecast. Even that is looking iffy at this time...it might not
actually happen until next Wednesday or Thursday. However...
medium-range models are making strong indications that wet
conditions will develop in the 7-14 day period.
Aviation...for the 04/18z taf cycle...VFR area wide the rest
of today through tonight except for areas of IFR low clouds and fog
in the Coquille Valley and the Umpqua basin near krbg toward sunrise
Marine...updated 9 am PST, Wednesday 4 Mar 2015...high pressure
offshore and thermal low pressure along the coast will keep north
winds and steep seas going today. Winds will weaken tonight into
Thursday as the high pressure builds eastward...then reverse to
southerly by Thursday night. The thermal trough will redevelop
this weekend with light to moderate northerlies returning. Spilde
Climate...there is high confidence in a pattern change to wetter
and less warm conditions for the week 2 period, which is March
10th to the 17th. There are several reasons to have high
confidence in this change occurring, as the Arctic oscillation is
expected to go from positive to very positive and the Madden
Julian oscillation is expected to become active again as it
propagates through the western Pacific Ocean. Low pressure near
Hawaii is likely to interact with this flow sending storm activity
into the region. With the storm track coming from the Hawaiian
Island area snow levels usually end up 6,000 to 8,000 foot range.
Beyond week 2 model guidance is generally indicating an active
storm track along the West Coast focused across California. How
far north this will extend is uncertain, but it does appear it
will reach north into our area, at times. It should be noted that,
with low pressure near Hawaii, that precipitation from single
storms could be significant if a consolidated jet stream reaches
into our area. Btl
Pacific coastal waters...Small Craft Advisory for hazardous seas
until 4 am PST Thursday for pzz370-376.
Small Craft Advisory for winds until 4 PM PST this afternoon