Scientific Forecaster Discussion
fxus66 keka 262203
Area forecast discussion
National Weather Service Eureka California
303 PM PDT Wed Jul 26 2017
Synopsis...an upper level low will bring the potential for a few
thunderstorms this afternoon and evening over Trinity and northern
Mendocino County. High pressure will build across the region for
the remainder of the week, bringing drier and warmer conditions to
the area. Coastal clouds and patchy fog will develop each night
and persist through the morning for the next few days.
Short term (through friday)...the upper level low has started to
move out of the area this afternoon and is now over the Central
Valley. Water vapor shows more mid level moisture over the area,
but as of 3pm there has only been cumulus build ups over the mountains
of Trinity County and northeastern Mendocino County. Any storms
that do form will likely dissipate around sunset as the heating of
the day diminishes. This evening the marine stratus is expected
to spread inland quickly once the daytime heating diminishes. Low
temperatures will be near seasonal levels tonight.
Thursday dry weather is expected across the area as high pressure
builds in. At the coast the inversion looks slightly weaker behind
the upper level low. This should allow the stratus to mix out a
bit more quickly tomorrow than today. Inland temperatures will
warm a few degrees over today and will be slightly above normal.
The marine layer will likely shrink a bit as well. Thursday night
the marine layer will return and will be similar to the previous
night. Friday inland temperatures will remain above normal and the
coastal stratus will push back to the coast in the afternoon. Mkk
Long term.../Friday evening through Tuesday night/
Hot weather in store for the interior through early next week, with
highs in the low triple digits in Weaverville area, and highs near
100 degrees in Ukiah. This will be about 5 to 10 degrees above
normal. So far this month, temperatures in the area have been
running above 3 to 5 degrees above. Thus, the warmer than normal
trend will continue.
The 500 mb heights will continue to rise through the weekend, as
the upper level ridge builds into northwest California from the south.
The height rise will be subtle, however, as there is an upper
level trough holding strong over Gulf of Alaska. There will be no
precipitation potential through the weekend into early next week.
There maybe a few weak upper level disturbances passing through
the area. This may bring slight increase in sky cover. Don't
expect the weather pattern to change much in this typical Summer
pattern. Hot and dry inland, marine stratus along the coast.
Changes to the previous forecast package is minor.
Fire weather...there is still a slight chance some showers and
thunderstorms this afternoon over Trinity and northeastern
Mendocino County. Cumulus has been building and the hrrr forcasted
reflectivity is showing some storms building over Trinity County
late this afternoon/early evening. Once the heating of the day is
over the thunderstorms are expected to come to an end. Thursday
dry weather is expected along with warming temperatures. In the
afternoon 5 to 10 mph west to northwest winds are expected.
Thursday night northerly winds will increase slightly over the
higher terrain in Mendocino County. Poor recoveries are also
expected, mainly in southern Mendocino County. Mkk
Aviation...the upper low has moved to the east of the region
today. There is still the potential for thunderstorms this
afternoon and evening over northeast Mendocino County and Trinity
County. This threat will diminish this evening. The marine stratus
has pushed back to the immediate coast this afternoon, but is
expected to move back in tonight. It will be fairly widespread,
but is not expected to make it into Ukiah. Thursday the inversion
looks a bit weaker due to being on the backside of the low. This
should help clear skies a bit earlier than today. Mkk
Marine...summertime maritime pattern will continue over northwest
California waters through the weekend. There is a quasi-stationary
ridge of high pressure set up over the east Pacific, and a thermal
low over Central Valley. The combined weather systems will generate
strong north winds over the coastal waters through the forecast
period. There is a potential to see some gale force wind gusts
Friday through Sunday, especially over the outer waters.
Seas are expected to remain fairly steep and elevated for the outer
waters through the work week into the weekend. There will be a
healthy northerly wind waves, bringing wave heights of 6 to 8 feet
to the outer waters. For the inner waters, wave heights will be
around 4 to 6 feet. Starting on Sunday, a decent south swell will
move into the coastal waters and linger through early next week. The
south swell will have a wave period of around 15 seconds at around 5
to 6 feet. This swell is caused by hurricane hiary and Tropical
Storm Irwin, as these systems are expected to head north, and the
southerly swell will be generated on the east side of these tropical
systems. The south swell will be Worth watching for the next few
Northwest California coastal waters...
Small Craft Advisory until 5 PM PDT Saturday for pzz470-475.
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