Weather

749 
fxus66 kmfr 052258 
afdmfr 


Area forecast discussion 
National Weather Service Medford or 
258 PM PST Monday Jan 5 2009 


Discussion... 
the polar jet stream is currently draped northwest to southeast 
from about Juneau Alaska...to Seattle Washington...across eastern 
Oregon to southern Nevada. Warm air and subtropical moisture riding 
over the top of a large ridge of high pressure centered between 
California and Hawaii is resulting in a broad overrunning pattern 
across the forecast area with high snow levels but only light 
precipitation across the region. 


Morning reports indicate that mostly rain fell overnight at all 
elevation below tree line from Howard Prairie southward. Reports 
from the Warner Mountains west to Bly Mountain to Crater Lake 
indicate 2.5 to 6 inches of new snow. Water amounts were near 20 
percent even at Crater Lake National Park. Winds have been quite 
strong across the higher elevations of Lake County with the high 
blower Summer Lake gusting over 80 miles per hour early this 
morning. Gusts in the low 70s were also reported at the exposed 
Cape Blanco Headland site with solid gales across the most of the 
waters. 


For tonight another warm frontal wave will push into the coast and 
then across the forecast area through Tuesday morning. Snow levels 
will remain high...fluctuating between 4000 and 6000 feet east of 
the Cascades and between 5000 and 7000 feet from the Cascades 
westward. Precipitation amounts will generally be less than a 
quarter of inch for this event...except along the coast and in and 
near the coastal mountains where they will be a bit higher. The 
bottom line. 


The jet stream will generally lift north through early Wednesday 
after tomorrows warm frontal wave causing precipitation coverage 
and amounts to decrease across the area. Have followed the European model (ecmwf) 
for the most part...but with quantitative precipitation forecast leaning on the low side for the 
period given the primary forcing remaining north of the area. 


A modest front will push into the area late Wednesday through 
Thursday evening delivering another slug of moisture across the 
region. This system should drop snow levels low enough for a few 
inches of snow across most of the mountains and modest rain 
amounts across the region. This still is unlikely to result in any 
river problems across the region. 


High pressure then build in with Norma to above normal 
temperatures across the area and below normal precipitation. 
These conditions are currently expected to persist through th 8 to 
14 day period...which is Jan 11th through the 19th. Confidence is 
high for this pattern change. Btl 


&& 


Aviation... 
mountain obscurations continue across the forecast area at this 
time as warm air continues to overrun cooler conditions along and 
surface. Aside from the mountains IFR and LIFR conditions due to 
fog and low clouds exist in western Siskiyou...Curry...eastern 
Coos...and western Douglas counties at this time. Other areas are 
VFR with local MVFR and IFR near the mountains. The first 
warm/occluded boundary that pushed through most areas last night 
through this morning is still lingering across Lake County. This 
combined with the jet stream moving over the Cascade mountains and 
east side are leading to plenty of mountain Lee wave clouds and 
likely some bumpy air near ridge top level. A new warm front will 
push into the coast this evening and then move across the west 
side which is likely to decrease ceilings and visibilities 
overnight. On the east side MVFR and IFR are expected tonight. 
Conditions tomorrow will be similar to what they were this morning 
as the warm front lingers in the morning...and the jet stream 
drifts northward in the afternoon. Btl 


&& 


Mfr watches/warnings/advisories... 
or...none. 


California...none. 


Pacific coastal waters... 
- hazardous seas warning until 10 PM PST this evening for 
pzz350-pzz356-pzz370-pzz376. 


$$ 


Btl/fb/rh