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621
FXUS66 KMFR 210405 AAA
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
905 PM PDT Mon May 20 2024

Updated Aviation and Marine discussions

.AVIATION...
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21/06Z TAFs...VFR conditions will continue through the
TAF period. Guidance shows some clouds moving along the coast, north
of Cape Blanco later tonight, but it`s not expected to have an
impact on flight conditions. Breezy winds are expected at the
terminals Tuesday afternoon and early evening, but winds speeds
should be less than they were earlier this afternoon. -Petrucelli
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.MARINE...
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Updated 800 PM Monday, May 20, 2024...North gales and
very steep, wind-driven seas south of Cape Blanco will continue
through this evening. Model guidance continues to suggest periods of
off-and-on gales south of Cape Blanco, and a Gale Warning remains in
place for the areas where these gales are expected to surface.
Conditions will be relatively less severe north of Cape Blanco, but
still hazardous to small craft with breezy north winds and steep
seas.

Winds will diminish overnight tonight, then an area of low pressure
approaching from the north will disrupt the thermal trough on
Tuesday with winds and waves diminishing. Moderate winds will likely
continue into Wednesday with northwest swell gradually increasing
Wednesday afternoon. -Schaaf/Petrucelli

.SHORT TERM...

A lot of fair weather cumulus remains over eastern Oregon this
afternoon with some lingering moisture across the region. As for
later tonight, high pressure will build as a subsidence inversion
develops. There is a low potential for fog along the Central
Oregon coast and into the Umpqua Valley tonight. One can see
dewpoints dropping as we mix out, so there isn`t a whole lot of
moisture in the boundary layer.

In addition, temperatures will be on the cool side yet again
as lows fall into the lower 40`s and even upper 30`s in some
valleys. There are indeed some cooler spots in the forecast area
that will be in the lower 30s. Those areas will probably see some
patchy frost tonight, but regions west of the Cascades on average should
steer clear of widespread frost or damaging freeze.

Heading into Tuesday, temperatures will continue to trend warmer
with high pressure in control. Highs will trend about 5 degrees
higher farther inland with smaller trends along the coast. Other
than some breezy northwest winds, The weather on Tuesday will
remain fairly quiet before deeper northwest flow develops ahead of
the next upper level wave. High and mid level clouds will be on
the increase by Tuesday evening. The NBM also brings increasing
PoP chances to Coos, Douglas, and northern Lake and Klamath
Counties as this next wave approaches other locations farther to
the south should remain relatively drier into Wednesday.

Another thing that stood out was the strength of winds Wednesday
afternoon east of the Cascades. Forecast soundings show deep
mixing all the way up top 700 mb as this low approaches with dry
adiabatic lapse rates, which should really aid in momentum
transfer. Soundings suggests that there is a 50% chance for wind
gusts up to 45 mph over certain high terrain locations. Windy
spots like Summer Lake and highway 31 could see wind gusts impact
those locations Wednesday afternoon.

-Smith

.LONG TERM...

The longer term starts out with a cold front moving through
Tuesday night as an upper level wave departs the region. The best
chances for rain remain outside of the forecast area or in the
extreme northern portions of Douglas County. There aren`t many
weather impacts that we see on Wednesday before high pressure
begins to build on Thursday.

Another wave arriving Friday appears to hitting northern Oregon
and washington instead of southern Oregon. The result appears to
be a higher probability of drier weather in addition to
temperatures. There are still likely some ensemble members
choosing a more southern track with a very low chance of
precipitation within southern Oregon and northern California on
Friday. However, that seems like the least likely scenario at this
point in time.

The last topic worth noting is temperatures trending warmer
towards the start of next week. Ensembles show 850 mb temperatures
taking a notable path higher and this can be seen in next Monday`s
and Tuesday`s high temperature forecast. The region should see
highs in the lower 80`s with more late Spring like weather.
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&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...CA...None.

PACIFIC COASTAL WATERS...Small Craft Advisory until 11 AM PDT Tuesday
     for PZZ356-376.

Small Craft Advisory until 11 PM PDT this evening for PZZ350-
     370.

     Gale Warning until 11 PM PDT this evening for PZZ356-376.

&&

$$