Weather

227 
fxus66 keka 292244 
afdeka 


Area forecast discussion 
National Weather Service Eureka California 
330 PM PDT Friday Aug 29 2008 


Synopsis...one more day of hot and dry weather is expected today 
before an upper level trough brings significantly cooler weather to 
the interior by Sunday. At the coast...an increasing marine layer 
will bring cooler temperatures as well as a return of stratus and 
patchy drizzle during the overnight hours into Saturday. Pleasant 
sunny and warm weather returns next week as high pressure builds 
back over the region. 


&& 


Short term...sunshine was plentiful throughout most of northwest 
California today with only some high clouds moving through southern 
and eastern portions of the County Warning Area. Many interior locations saw hot 
temperatures...topping out in the middle 100s in the hottest spots. 
However...visible satellite image from 21z shows the marine stratus 
filtering into the Redwood coast...the first signs of the upcoming 
pattern change. 


An upper level trough will continue to slide down the Pacific northwest coast 
from the Gulf of Alaska tonight and Saturday...with a weak surface front 
expected to pass through northwest California overnight. Fog and patchy 
drizzle will plague coastal areas as the marine layer deepens ahead 
of the front...with not much more than partly cloudy skies 
elsewhere. With the upper trough moving overhead Saturday...should see 
the marine layer break with mostly sunny skies prevailing over the 
region again by the afternoon. Maximum temperatures will drop some 10 to 
20 degrees for interior locations on Saturday with the passing of 
the trough...and further cooling can be expected on Sunday. Saturday 
and Sunday night will be considerably colder as well...with 
sheltered interior valleys perhaps dropping into the middle and upper 
30s Sunday night with significant cold air advection behind the 
system. Breezy north winds overnight Sunday will keep more exposed 
areas warmer and drier...especially along the ridgetops. Monday will 
begin a warming trend to northwest California as the upper level 
trough pushes east. Rjm 






Long term...Monday through Thursday Monday will see a ridge of high 
pressure building aloft behind the the exiting trough late Sunday. 
This ridge will usher in northerly winds initially followed by east 
and northeast winds over much of the area Monday and Tuesday. The 
winds will be strongest during this period with decent upper level 
support...thus a Fire Weather Watch has been issued to reflect the 
pattern. The offshore flow looks to persist Wednesday through 
Friday however the winds do not look nearly as strong. Nonetheless 
the pattern should provide mainly sunny and warm conditions to all 
areas including the coastal zones if the flow is strong enough to 
prevent stratus from returning. One fly in the ointment is that 
extended forecast models are not in great agreement but have decided 
to go with the GFS which depicts the more typical fall pattern. 
Have upped the temperatures a couple degrees along the coast and removed 
fog. Tonkin 


&& 


Aviation...low stratus and patchy fog will bring MVFR to IFR 
conditions along the coast tonight into Saturday morning. Mainly VFR 
conditions will prevail inland. Th 


&& 


Marine...north winds will increase overnight as high pressure builds 
inland through the Pacific northwest and low pressure persists over 
northern California. The winds will be strongest over the outer 
waters with gale force gusts becoming widespread by Saturday 
morning. Have upgraded the gale and hazardous seas watches for the 
inner waters to warnings as it is likely that the gale force gusts 
will reach the inner waters by Saturday afternoon. Large and steep 
wind waves will accompany the strong winds with large fresh swell 
developing in the inner waters. Th 


&& 


Fire weather...two periods of concern on the horizon. The first is 
an unseasonably strong but dry upper trough swinging throught northwest 
California on Saturday night/Sunday. Gusty northerly winds will accompany 
the trough passsage and are expected to impact ridges and upper 
slopes on Sunday. Cooler temperatures will be observed during this 
period thus rh's should be somewhat favorable. Later on Sunday as 
the trough moves east...high pressure builds rapidly from west to 
east with a typical "offshore" surface pattern developing the next 
couple days. Forecast models are not in great agreement on the 
strength and placement of a developing thermal trough but at a 
minimum it appears that better upper level support may be present 
for stronger east and northeast winds. Have issued a Fire Weather 
Watch for all interior zones except for 203 and 204 where winds and 
relative humidity are not yet expected to reach critical values. Tonkin 


&& 


Eka watches/warnings/advisories... 


Fire Weather Watch in effect for fire zones: 211,212,276,277 and 283 
for wind and relative humidity. 


Gale Warning for... 
... From Sat morning through Monday morning. 
... From midnight tonight to Monday afternoon. 
... From Sat afternoon through Sun afternoon. 


Hazardous seas warning for... 
... From Sat morning through Monday morning. 
... From midnight tonight through Wednesday afternoon. 
... From Sat afternoon through Sun afternoon. 






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