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041
FXUS66 KMFR 250327
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
827 PM PDT Fri May 24 2024

.DISCUSSION...
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One short wave trough is exiting to the east of the
area this evening while another is fast on its heels. The first
was able to touch off scattered showers over the East Side and
in portions of NE California this afternoon into this evening (no
lightning though). Most of these are diminishing, but some still
remain in southern Modoc County and south-central Lake County. The
second trough is moving into NW sections of the CWA this evening
where another area of scattered showers exists. These should stay
mostly north of the Rogue-Umpqua Divide tonight, with gradually
diminishing coverage overnight into Saturday morning. The trough
axis will shift to the east of the area Saturday afternoon and
things will dry out with increasing sunshine. It will remain on
the cool side for late May, with the complement of NW breezes in
the afternoon. Highs in the upper 60s and low 70s will be common
west of the Cascades, but generally from the upper 50s to the mid
60s from the Cascades eastward. Warmer and dry weather is expected
the rest of Memorial Day weekend. -Spilde
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&&

.AVIATION...
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25/00Z TAFs...Mainly VFR conditions prevail across the
region this afternoon with gusty northwest winds. A weak front is
moving through the region, with scattered showers moving across Lake
and Modoc Counties. These showers look rather weak on radar, but
there is about a 10-15% chance that a stronger shower could turn
into an isolated thunderstorm. Gusty winds will persist through this
evening, and ease after sunset.

MVFR and local IFR conditions are developing along the coast this
afternoon, mainly north of Cape Blanco, with additional shower
activity expected through this evening as well as into the Umpqua
Basin. Lower ceilings will push inland later this evening and
overnight, with MVFR expected in the Umpqua Basin, and VFR ceilings
expected south of the Rogue-Umpqua Divide and west of the Cascades.
Conditions are expected to improve to VFR areawide by late Saturday
morning. /BR-y
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&&

.MARINE...
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Updated 800 PM Friday, May 24, 2024...A weak front is
maintaining gusty north to northwest winds this evening. These winds
will persist overnight into Saturday with steep, short period seas
expected for all areas tonight through Saturday morning. Gusty north
winds (with gusts up to 25 kt) and steep seas will linger Saturday
afternoon and evening for areas south of Cape Blanco.

Winds and seas are expected to lower Sunday into Monday but may
remain locally gusty and locally steep for areas south of Cape
Blanco. Another front moves through next Tuesday but expect mainly
light winds. This is followed by a potential for increasing north
winds and seas on Wednesday and Thursday. -CC/BR-y
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&&

.PREV DISCUSSION... 
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/Issued 219 PM PDT Fri May 24 2024/

DISCUSSION...Satellite imagery shows varying amounts of high clouds
and building cumulus underneath the high clouds east of the
Cascades, which is where instability is greatest. To quantify
greatest, it`s expected to me marginal at best, but still sufficient
enough for a few isolated thunderstorms later this afternoon and
early this evening in portions of Lake, northeast Klamath, and Mount
Shasta and points east to northeast of Mount Shasta.

Upper troughing remains over the area tonight, with a few showers
north of the Umpqua Divide, and northern Cascades from about Crater
Lake north. Even then, precipitation amounts will be less than 0.10
of an inch.

Elsewhere it will be dry, but we`ll see increasing cloud cover
getting banked up along the Cascades and Siskiyous and we could see
it also fill into the Rogue Valley later tonight into most of
Saturday morning.

Other than a few intermittent showers north of the Umpqua Divide
Saturday morning, it will be dry with cloud cover gradually
diminishing during the morning with mostly clear skies in the
afternoon. Afternoon temperatures for the interior will be a couple
of degrees cooler on average.

Dry weather is likely Sunday through at least Tuesday morning.
Afternoon temperatures for the interior will be warmer Sunday and
Monday, then cooler Tuesday as an upper trough approaches the
forecast area. A weak front will approach the coast and could bring
light rain to the north coast and northwest Douglas County Tuesday
afternoon and remaining dry elsewhere.

The general consensus is for a deeper upper trough presence Tuesday
night through Thursday. The main impact will be cooler temperatures,
with the best chance for showers along and north of the Umpqua
Divide and northern Cascades. The operational ECMWF and GFS show
signs of convective feedback east of the Cascades which could
result in a slight chance of showers Wednesday and Thursday
afternoon and early evenings. This is in response to energy
(triggers) rounding the base of the upper trough. The NBM does not
pick up on this, but pattern recognition suggest it warrants at
least a slight chance.

Digging deeper, the ensemble means (GFS and ECMWF) show upper
troughing Wednesday and Thursday, but not as deep as the
operational models which could be a result of some individual
members washing it out. Last nights run of the clusters show split
solution (50/50) between the upper trough and ridging.

The upper troughing will eventually push east towards the end ofthe
week into the following weekend although about 33% of the members
maintain an upper trough over the PAC NW. -Petrucelli

AVIATION...24/18Z TAFs... An approaching weak front will move
onshore late this afternoon and inland tonight. Northwesterly winds
will pick up ahead of the front this afternoon and continue into the
evening as the front gradually moves inland, but winds won`t be as
significant as the system that passed through earlier this week.

Light, spotty precipitation will move onshore and inland late this
afternoon into tonight. Best chances will be in northern portions of
the region (northern Douglas, Coos, Klamath, and Lake counties) as
well as along the south OR Cascade crest. Additionally, there is
about a 15-20% chance for isolated thunderstorms developing later in
the afternoon into the evening in southern and eastern Lake, eastern
Siskiyou and Modoc counties.

MVFR and local IFR conditions will develop along the coast in the
late afternoon and early evening, continuing overnight. Inland MVFR
conditions are expected in Douglas County this evening and tonight.
Mountain obscurations are also expected from the Southern Oregon
Cascades west this evening through early Saturday morning.
Conditions are expected to improve to VFR areawide by late Saturday
morning. -CC

MARINE...Updated 200 PM Friday, May 24, 2024...AA front is
moving onshore this afternoon. Behind this front, expect moderate
north to northwest winds and steep, short period seas to develop
this evening then continue through early Saturday afternoon. Gusty
north winds (with gusts up to 25 kt) and steep seas will linger
Saturday afternoon and evening for areas south of Cape Blanco.

Winds and seas are expected to lower Sunday into Monday but may
remain locally gusty and locally steep for areas south of Cape
Blanco. Another front moves through next Tuesday but expect mainly
light winds. This is followed by a potential for increasing north
winds and seas on Wednesday and Thursday. -CC
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&&

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

PACIFIC COASTAL WATERS...Small Craft Advisory until 2 AM PDT Sunday
     for PZZ350-356-370-376.
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&&

$$

MAS/MNF/MAP/CC