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Area forecast discussion 
National Weather Service Sacramento California 
930 PM PDT Monday Oct 6 2008 


Discussion... 
Pacific westerlies now driving a weak frontal system into the 
Pacific northwest while flattened high pressure ridge over 
California keeps skies mainly clear. Some warm sector cirrus 
currently spreading over far northern County Warning Area and may see more as the 
tail end of the weak cold front moves over the north end of the County Warning Area 
on Tuesday. Otherwise...fair skies will continue over the forecast 
area. Fair skies and warming airmass brought in maximum 
temperatures today about 5 to 12 degrees above yesterday and 
temperatures this evening still running about 2 to 5 degrees above 
24 hours ago. Should see overnight lows just a bit warmer tonight 
than last under slightly warmer airmass and in line with current 
forecast package. Current forecast package for Tuesday increases 
highs a few degrees but considering forecast 850 mb temperatures and 1000 
to 500 mb thickness values are predicted similar to today...tuesdays 
highs may be slightly high. 


Middle of the week will be dominated by zonal flow across the 
Pacific northwest and norcal. Daytime highs should begin to slip a 
bit as airmass cools down to right around normal for this time of 
year. Surface high pressure over the Pacific northwest will bring 
breezy north winds at times but westerly flow aloft will limit upper 
support so do not expect winds to be significantly strong during the 
middle week period. Models still uncertain about outcome for end of the 
week as cool for the season upper low drops out of Canada and into 
the Great Basin. 18z GFS and 12z European model (ecmwf) place the lows center over 
northern Nevada by Friday afternoon while UKMET and Canadian move 
the low farther to the east. Quick look at 00z GFS now places the 
low center even farther west. All solutions would result in dry 
conditions for the County Warning Area...cooler temperatures and breezy conditions 
but how cool and how breezy or windy will depend on where the low 
end up. If GFS verifies...gusty winds and lowering humidity will 
bring significant fire weather concerns Friday and Saturday. High 
pressure rebuilds over the West Coast over the coming weekend for a 
warming trend and lighter winds. 


&& 


Aviation... 
hi pressure weakens and moves east as southern portion of cold front moves into far northern cal 
Tuesday and dissipates. Areas scattered-broken clouds at or above fl150 generally north of kuki-kcic- 
ksve line with fnt after 12z Tuesday. VFR conds over interior norcal next 24 hours 
with westerly flow aloft exc local IFR conds with terrain obscured in mountain valleys from 
fog and St through 19z Tuesday. 


&& 


Sto watches/warnings/advisories...none. 


&& 


$$