Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 292142
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
242 PM PDT FRI JUL 29 2016

.DISCUSSION...The latest visible image shows cumulus starting to
develop in southeast Modoc County and some in Siksyou County near
the Marble Mountains and Medicine Bow peak. Our main focus will be
the potential for thunderstorms or lack thereof late this afternoon
into this evening and again Saturday afternoon and evening. The last
several runs of the HRRR have been consistent suggesting isolated
storms (if we get anything) will be confined to southeast Modoc
County which is where most of the cumulus is developing at. A look
at the latest mesoscale analysis from SPC shows the highest cape
values in southeast Modoc County, even then it`s nothing that would
suggest any concerns. Therefore we have decided to scale back the
thunderstorms and keep them confined to southeast Modoc County late
this afternoon into early this evening. As the models have been
suggesting the past few days, the instability parameters have been
marginal at best with little or no trigger. Despite this, fire
danger is high fuels are receptive in this area, so it probably
won`t take much (isolated thunderstorms) to get a fire started. Also
models soundings show an inverted "V" which suggest any storms that
develop could be mostly dry and produce gusty outflow winds.

For now were keeping tonight dry. The NAM and GFS show a weak vort
lobe moving east to northeast into northern Cal, but it may not be
enough to trigger convection. The GFS has since backed off on the
convective feedback in the QPF field during the overnight period and
the NAM and HRRR show nothing. The bottom line is we probably won`t
get anything, but this is something that will need to be watched
carefully.

The focus for thunderstorms on Saturday will shift east to northeast
into southern Lake, Klamath, northeast Siskiyou and northwest Modoc
County as the aforementioned vort lobe moves east to northeast as it
gets caught up in the westerly flow as the upper trough in western
B.C. begins to move south. The environment should be similar to
Friday, therefore we`ll keep a slight chance mention. Gusty winds
could be a concern Saturday afternoon and evening east of the
Cascades.

After Saturday the threat for thunderstorms is pretty much over
with. An upper trough will swing north of the area Sunday morning
bringing a dry stable westerly flow over the area with the threat
for storms shifting well east of us. Temperatures will continue to
cool, but will still remain near or above normal. Another upper
trough will swing north on Monday bringing further cooling and
continued dry conditions. Gusty winds are also expected, especially
east of the Cascades Monday afternoon and evening. After Monday,
weak troughiness will remain over the area with dry weather and near
normal temperatures. -Petrucelli


&&

.AVIATION...29/18Z TAF cycle...IFR marine stratus continues along
the immediate coast down to Bandon. KOTH is sitting right at the
edge and expect periods of IFR cigs this afternoon into early the
evening. Areas of IFR cigs and MVFR vis will increase along the
coast north of Cape Blanco overnight and continue into Saturday
morning. Moderate to strong and gusty north winds are expected this
afternoon for most areas along the coast and offshore. Cumulus
buildups are expected over the higher terrain of northern California
into south central Oregon this afternoon and evening with a slight
chance of thunderstorms. -FB/CC


&&

.MARINE...Updated 217 PM PDT Friday 29 Jul 2016...A thermal trough
along the coast and high pressure offshore will continue to produce
moderate to strong north winds and steep to very steep wind driven
seas into early next week.  Hazardous warning level seas and gales e
expected mainly beyond 5 NM from shore today through
Saturday...mainly for locations from Cape Blanco southward. However
an area of hazardous seas warning conditions is expected to next
extend northward to just south of Cape Arago. Winds and seas should
peak on Saturday afternoon and evening. On Sunday, warning seas and
gales are expected from Cape Blanco south with small craft advisory
winds and seas to the north. On Monday, winds may drop below gale
force across most the waters. However, hazardous warning level seas
remain possible from Gold Beach south on Monday. Winds are expected
to rise to gales again by Tuesday evening and continue into Thursday
of next week. -CC

&&


.FIRE WEATHER...Updated 200 PM PDT Friday, 29 July 2016...

As of 1400 PDT, cumulus clouds are forming along the line from SW
Lassen County northeastward clipping SE part of Modoc County from
Likely to Eagleville. There is little sign of cumulus buildups
elsewhere; as a result, we have removed thunderstorm forecast for
the Marble Mountains, and confined the forecast for isolated strikes
to SE Modoc County.

Latest high resolution models suggest Saturday features the better
chance for storms overall; but only with isolated coverage, a fire
weather watch will not likely be issued. With high fire danger, hot
and dry conditions, and limited rainfall from any thunderstorms, the
probability of any lightning starting fires is high.

Wind speeds this weekend will be slightly stronger than normal with
low humidities. So far none of the guidance shows wind to be strong
enough to warrant a Fire Weather Watch. We will continue to headline
the Fire Weather Forecast for this potential. On Monday the
potential is greater as a cold front is forecast to move inland
bringing in a more seasonal air mass. We may have to issue a Fire
Weather Watch if next model run strengthens the wind.

Another continued concern is moderate to locally poor humidity
recoveries (40-60%) across the upper slopes and ridges of most of
the forecast area except the Umpqua Basin. Gusty northeast winds
will accompany the low humidities in the Coast Range tonight and
Saturday night. /FB

&&

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

Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Monday for PZZ350-356-370.
     Gale Warning until 5 AM PDT Sunday for PZZ356.
     Hazardous Seas Warning until 5 AM PDT Monday for PZZ356-376.
     Hazardous Seas Warning until 5 AM PDT Sunday for PZZ350-370.
     Small Craft Advisory from 5 AM Sunday to 5 AM PDT Monday for
     PZZ376.
     Gale Warning until 5 AM PDT Monday for PZZ376.

$$

MAP/MAP/MAP



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