594 
fxus66 kmfr 212222 
afdmfr 


Area forecast discussion 
National Weather Service Medford or 
222 PM PST Friday Nov 21 2008 


Discussion...the leading edge of the cold front is reaching our 
outer marine waters. The NAM and GFS appear to be too slow with 
the timing of the front. They both suggest the front will reach 
the coast until around 7 PM PST. So have opted to go with 
increasing probability of precipitation at the coast this evening...then spreading inland 
overnight tonight as the front continues to make progress inland. 


The front is expected to slow down Saturday morning. So expect 
showers to continue into the morning hours...then slowly decrease 
in the afternoon as 500mb heights rise in response to a shortwave 
ridge moving towards the County Warning Area. Conditions will be dry Saturday 
night into Sunday. However...conditions will be favorable for fog 
to develop in the Westside valleys. 


The ridge axis will move over the region Sunday morning...then 
shift east Sunday afternoon. Conditions will be dry and cool with 
fog lingering for most of the morning hours in the valley followed 
by partly cloudy skies in the afternoon. 


There is some uncertainty for the first part of next week. The 
NAM/GFS and European model (ecmwf) suggest a split flow will develop with an upper 
level low sinking south towards the central California coast. If 
this pans out...then precipitation will be delayed until Monday 
night at the earliest and at the same time could weaken to the 
point where there will not be much more than sprinkles developing 
at the coast. 


Petrucelli 


Tuesday through Friday... 
there is a high level of uncertainty in the timing...and moreso in 
the details...of the forecast in this critical time period. Model 
guidance has had a lot of run to run inconsistencies. 


At this point...have sided with the 12z European model (ecmwf) as it appears to be 
the consensus solution of the 12z GFS and the 12z Canadian. The 
GFS splits the Tuesday system and then brings in a system on 
Thursday with flow from the south. The Canadian...on the other 
hand...indicates a progressive northwest flow storm track over the 
area with snow levels that would be problematic for elevations 
above 4000 feet. The European model (ecmwf) indicates the Tuesday system 
splitting...but not until its over our area. It then brings in a 
system under northwest flow on Thursday that would bring snow 
levels around 3500 to 4500 feet. The concern...at this time...is 
the possibility that a blended solution could occur...in which the 
remnant cut-off low over California from the Tuesday system gets 
pulled northward ahead of the northwest flow storm system 
indicated. This would lead to travel troubles on Thursday. 


Thus...as mentioned...confidence is not high in the details of the 
forecast for Thanksgiving just yet. Instead...its low...but there 
is the potential of travel troubles for Thursday...so stay tuned. 
Lutz 


&& 


Aviation...high clouds are moving over the region at this hour 
and the trend is for ceilings to lower later this evening overnight 
tonight as the cold front moves into the area. Ceilings will lower to 
MVFR at the coast this evening with IFR overnight tonight. Ceilings 
tonight could lower to near 2000 feet with a scattered deck near 
1000 feet. Inland ceilings should remain above 3500 feet tonight into 
Saturday morning. However there will be occasions where ceilings from 
broken cloud cover will lower to 2000 feet. There is the potential 
for patchy fog to develop in the Rogue Valley early this 
evening...before the cloud deck lowers from the incoming front 
tonight. 




&& 


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


California...none. 


Pacific coastal waters...Small Craft Advisory for winds until 10 PM 
PST this evening for pzz350-pzz356-pzz370-pzz376. 
Small Craft Advisory for hazardous seas until 4 PM PST Saturday 
for pzz350-pzz356-pzz370-pzz376. 


$$