FXUS66 KMFR 192152

Area Forecast Discussion
National Weather Service Medford OR
252 PM PDT Mon Aug 19 2019

.DISCUSSION...Clear skies prevail across the area, with the exception
of the coast south of Cape Blanco where coastal stratus lingers.
Temperatures are similar to what they were this time yesterday,
and overall conditions this afternoon will resemble those of
yesterday and the day before. The marine layer will make a return
to the coast and inland into portions of the Umpqua Divide
tonight, but should be less extensive since the marine layer won't
be quite as deep. Conditions on Tuesday will be a near repeat of

On Wednesday, a front moves through the area and this will change
things up a bit. Models have trended stronger and farther south with
this front and the forecast has been adjusted accordingly. Although
models have trended stronger, this front is still relatively weak
compared to the more fall like systems. While it does have a decent
chance of bringing rain to the area (mainly west of the Cascades),
we aren't expecting wetting rains. This front is more of a high PoP,
low QPF system; high chance for a little rainfall. Winds are also on
the meager side. We'll likely see some increased afternoon breezes,
but nothing really to raise any eyebrows about. Given the time of
year, we're on the watch for any thunderstorm potential, but current
models don't show favorable conditions for thunderstorm development
ahead of or with this front. The biggest change most of us will
notice is increased cloudiness and cooler temperatures on Wednesday.
How much cooler is still up for debate, however. The GFS is the
cooler solution, but even the newest run of the EC has trended
cooler. Regardless we aren't' talking about a huge cool down here,
only on the order of about 5 to 10 degrees, but it will feel more
like early September than middle August.

The front exits the area Wednesday night into Thursday, and behind
it, the thermal trough quickly redevelops and summer like
temperatures return. This will bring the return of hot, dry days
with nightly intrusions of marine stratus along the coast through
Friday. An even weaker front will brush the area Saturday. This
front is drier and will only knock temperatures down by a degree or
two on Saturday. Beyond Saturday, models show a ridge building over
the area with a warm up for next week. /BR-y


.AVIATION...For the 19/18Z TAFs...VFR conditions will prevail
for most areas through the next 24 hours. Along the coast and just
inland, marine layer MVFR is expected to return this evening and
possibly lower to IFR by early Tuesday morning. Ceilings are less
likely to return to the Umpqua Basin tonight as the marine layer is
expected to compress some. -BPN


.MARINE...Updated 245 PM PDT Monday 19 August 2019...Mostly light
winds and low seas will prevail over the waters through Tuesday
morning. A cold front will bring a period of increasing south winds
Tuesday afternoon into Wednesday with building swells late Tuesday
night through Thursday. We've added a small craft advisory for the
waters beyond about 20 NM from shore and north of Cape Blanco due to
south-southwest winds, steep south-southwest wind waves and
increasing west swell Tuesday night into Wednesday morning.

Short period waves ease Wednesday afternoon, but mixed swell will
persist into Thursday. Then, model data suggest that the thermal
trough will restrengthen quickly on Thursday with rapidly increasing
north winds and steepening short period seas. Gale force winds and
very steep seas are possible south of Cape Blanco by late Thursday
afternoon/evening. After Thursday, much will depend on the strength
of the thermal trough. Guidance shows the thermal trough weakening
Friday night into Saturday, but then strengthening again Sunday into
early next week. -Spilde


.FIRE WEATHER...Updated 200 PM PDT Monday 19 August 2019...Warm
and dry conditions are expected across the area for the next couple
of days. Temperatures will become slightly warmer on Tuesday with
typical humidity values. Winds will become gusty for the Shasta
Valley and portions of the East Side this afternoon and evening, and
again Tuesday.

A front will move into the area on Wednesday, producing much cooler
temperatures and increased cloud cover for much of the forecast area.
More importantly, humidities will see a significant improvement, and
overnight recoveries Wednesday night into Thursday morning will be
very good across the board. Some light drizzle or rain will be
possible for areas west of the Cascades on Wednesday, mostly along
and west of the coastal ranges, but wetting rains are not likely.
Areas east of the Cascades and in northern California should remain
dry, but should see a period of gusty west winds as the front
passes. No thunderstorms are expected in the area, but a few cumulus
build-ups could be possible east of the Cascades on Wednesday.

Thursday, the thermal trough makes a very fast and very strong
return, and humidities will drop just as quickly as they rose on
Wedensday. A quick warming and drying trend is then expected through
the rest of the week and into the weekend, with breezy afternoon and
evening winds. Overnight east flow and moderate recoveries are
likely across the ridges, especially across the southern coastal
ranges and over western Siskiyou County. -BPN




Pacific Coastal Waters...Small Craft Advisory from 8 PM Tuesday to 11 AM PDT Wednesday
for PZZ370.


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