Area Forecast Discussion
Issued by NWS Eureka, CA

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FXUS66 KEKA 281215

National Weather Service Eureka CA
515 AM PDT Tue Mar 28 2017

.SYNOPSIS...Upper level ridging will maintain dry weather
today through tonight. A cold front will bring a chance of rain
Wednesday through Thursday morning.


.DISCUSSION...Upper level ridging will build over the area
today providing dry weather conditions and warmer afternoon
temperatures. Satellite imagery has been showing mid layer
clouds swiftly moving over the area from time to time in the
northwesterly flow aloft. Even with the high and mid clouds,
it is shaping up to be a fine day with fairly pleasant afternoon
temperatures, primarily for the interior.

We do have a frost advisory for interior portions of Mendocino
county for early this morning. Temperatures across northern
Mendocino county interior valleys were running in the mid to
upper 30s. The mid clouds have been hindering the full rate of
cooling. The advisory will be close. Thus will leave it as is.

What a surprise, the one dry weather day will not last. On
Wednesday a cold front will approach the north coast and rain
will once again enter the forecast picture. Broad scale ascent
will increase through the day on Wed and light rain will probably
start in the afternoon for areas north of the King Range. The cold
front will push through Wednesday evening when most of the rain
will occur. Highest amounts and chances will be in Del Norte and
Humboldt counties. Southern Mendocino may not see any measurable

A mid level shortwave trough will generate additional showers
later Wed night into early Thu. Instability will increase Wed
night into Thu morning in response to strong 500mb cooling.
Isolated thunderstorms will be possible out near the coast and
over the coastal mountains north of the King Range. The NAM and
GFS were not in great agreement with the degree of instability.
This will need to be looked at more closely by the next couple of
shifts for inclusion into the forecast.

The GFS has also been hinting at the possibility of convection in
Trinity county Wednesday afternoon as a 110KT westerly speed max
noses toward Cape Mendocino. The NAM and BUFKIT soundings were not
as aggressive with the convective threat. Confidence is not high
enough to include thunder in the forecast at this point due to the
incongruities between these two models.

Upper level ridging will quickly rebuild later on Thursday after
the shortwave trough progresses eastward. Robust northerly winds
will develop behind this shortwave on Thu. The brisk north flow
will last through Friday. Blustery northerly winds are expected
at the coast, primarily on Friday. The ridge will start to flatten
out and weaken on Saturday in response to another upper trough.
This trough will probably produce some light rain or showers on
Sunday. Additional light rain chances may follow on Monday before
the ridge rebuilds on Tuesday.


.AVIATION...VFR to MVFR conditions and light winds to calm
conditions will continue at KCEC through early this morning. The
lower conditions will due to reduced ceilings and/or visibilities.
VFR conditions and light winds will prevail at KCEC late this
morning through tonight as a high pressure ridge persist across
the region. VFR conditions and light winds to calm conditions will
continue at KACV and KUKI through tonight.


.MARINE...Light to moderate winds will continue today through
Wednesday as a high pressure ridge maintains a relaxed pressure
gradient across the waters. An elevated westerly swell will
continue propagating across the waters this week. The seas will
diminish slightly Wednesday night. A weak cold front will move
across the region early Thursday. The winds and seas will increase
Thursday. Small craft advisories will continue in effect across
all the waters through Wednesday afternoon due to the westerly
swell. Another weak cold front will move across the waters late
Saturday and early Sunday. Small craft advisories are likely
across the southern outer waters Thursday through Saturday due to
elevated winds and seas. Small craft advisories are likely across
the northern outer waters through Saturday due to elevated winds
and/or seas. Small craft advisories are likely across the southern
near shore waters Thursday and again on Saturday due to elevated
winds and/or seas. Small craft advisories are likely across the
northern near shore waters on Saturday due to elevated seas.


CA...Frost Advisory until 9 AM PDT this morning for CAZ110-111-113.

until 3 PM PDT Wednesday for PZZ450-455-470-475.



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