Weather

435 
fxus66 keka 272227 
afdeka 


Area forecast discussion 
National Weather Service Eureka California 
325 PM PDT Wednesday Aug 27 2008 


Synopsis...hot and dry weather is expected through the remainder of 
the week as an upper level ridge builds into the West Coast. Light 
offshore flow in the night and mornings will mean mostly clear skies 
and warmer temperatures for the coast through Thursday. Slight cooling is 
likely this weekend as an upper trough dips into the Pacific 
northwest. 


&& 


Short term...upper ridge over the eastern Pacific will recenter 
itself over northern California tonight into tomorrow with very warm 
to hot afternoon readings away from the coast and plenty of 
sunshine. Afternoon temperatures will approach 105 degrees for the 
warmest inland valleys tomorrow although these same locations will 
have a lot of ground to make up as readings start the day out in the 
40s to lower 50s. At the immediate coast...mild and breezy 
conditions can be expected. Patchy stratus is possible along the 
coast north of Cape Mendocino from time to time...but should remain 
rather limited through Thursday. As the ridge begins to flatten out 
Thursday night through Saturday...coastal stratus will become 
progressively much more prevalent and the marine layer will probably 
deepen sufficiently by Friday night that the possibility for drizzle 
along the coast will be included in the forecast. Saturday will 
bring much cooler weather to inland locations as a seasonably strong 
trough dives into the Pacific northwest...with readings dropping 10 
to 15 degrees from Friday. Burger 


Long term...models are in good agreement in placing the trough axis 
along the West Coast Sunday morning. Thus...Sunday will likely be 
the coolest day of the forecast period for interior locations. As 
the trough shifts eastward...the West Coast will transition to weak 
ridging by Monday into Tuesday and bring a rebound in maximum temperatures 
inland. Though models are inconsistent and details are sketchy... 
the general model consensus is for a trough to move into the Pacific 
northwest in the Wednesday/Thursday time frame. The European model (ecmwf) keeps the trough 
further north and shows no weakening in the ridge to our 
southwest...while the GFS shows a slight breakdown of the ridge. 
Will generally go with persistence during this time with little 
change in weather or temperatures expected under the weak flow 
aloft. Kl 


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Aviation...visible images show streak of stratus cloud that formed 
near and southwest of Humboldt Bay moving southward through the 
afternoon. This feature was picked up by WRF model and included in 
acv taf for this afternoon. However...expect that the dominant 
condition across the forecast area will be clear skies and 
unrestricted flight conditions through the evening. By 0800-0900 UTC 
Thursday expect some haze and patchy ceilings to form along the 
coast...but the offshore flow will keep this from being widespread. 
Cirrocumulus 


&& 


Marine...high pressure over the eastern Pacific and Pacific 
northwest states has combined with thermal low pressure over the 
central California coast to produce a strong gradient over the 
coastal waters of northern California. The gales offshore will 
continue through late tonight and then abate to high-end small craft 
values Thursday morning. The winds near shore will also slacken 
Thursday into Friday...but steep short period swell from the 
offshore winds will continue to move through the near shore waters. 
The gradient is expected to strengthen again over the weekend...so 
that winds and seas rebuild with gales and very large wind waves 
expected offshore. Cirrocumulus 


&& 




Fire weather...very poor overnight humidity recovery will accompany 
moderate offshore flow overnight tonight. Exposed Ridgetop sites 
above 4-5k feet may experience critical fire weather conditions for 
several hours but the duration and coverage is not quite sufficient 
to justify a red flag warning. A shifting thermal trough will bring 
the highest winds to Ridgetop sites near the coast in Humboldt and 
del norte counties...where the most exposed sites will see gusts in 
the 25-35 miles per hour. In Trinity and Mendocino counties...winds will be of 
lesser magnitude and are likely in many locations to be a little 
less than last night but humidities are likely to be at or slightly 
lower than this mornings values. Humidity recoveries in these areas 
may only reach 25-35 percent along the ridges compared to 40-60 
percent closer to the coast. Valleys/drainages in all areas will 
continue to experience decent overnight humidity recoveries along 
with cool nighttime temperatures. NE to east winds tomorrow night will 
be less for all areas as the coastal thermal trough relaxes slightly 
and shifts north. Burger 


&& 


Eka watches/warnings/advisories... 


Gale Warning and hazardous seas warning until 6 am PDT Thursday for 
pzz470-475. 


Small Craft Advisory until 11 PM PDT Thursday night for pzz450. 


Small Craft Advisory until midnight PDT Sunday night for pzz455. 


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