Gale Watch 31, NWS Medford, OR

Area Forecast Discussion
National Weather Service Medford OR
100 PM PDT THU JUL 21 2016

.DISCUSSION...21/12Z NAM/GFS/EC in.

Lots of marine stratus over the coastal waters...along the
coast...and in the lower Umpqua Basin. Mostly clear skies prevail
over the remainder of the Medford CWA...but some cumulus is
starting to pop over the higher terrain of the Umpqua Divide and
Cascades.

The area is under moderate southwest flow aloft between an
offshore long wave trough and a strong ridge centered over the
southern Great Plains.

A weak short wave ejecting from the trough will move onshore later
today. This will push a weak cold front onshore and this will
affect the area in two significant ways. First...it will bring
gusty winds to the east side and parts of the west side this
afternoon and evening. This...combined with dry air currently in
place...will make for Red Flag Warning conditions over parts of
the east side. Secondly...it will induce some instability over the
higher terrain around Crater Lake...bringing a slight chance of
thunderstorms to that area. There also has been some light
precipitation from the marine stratus...more than expected but
still less than 0.15 inches. Inland highs will be around 5
degrees below normal over Oregon and near normal over Northern
California.

The long wave trough will move onshore late tonight into Friday
morning...lifting north as it does so. Any lingering precipitation
associated with it or the front will end by daybreak Friday.

Friday will be the first day of a dry stretch that will last
through at least Monday. The upper level pattern will alternate
between weak zonal flow and weak troughing...with little in the
way of short wave activity over our area. Temperatures will warm
Saturday through Monday...and inland highs will be 5 to 10 degrees
above normal by Monday. Stronger winds will return to the coastal
waters as the thermal trough returns to the coast.

The forecast picture gets a bit murkier beyond Monday as some
model solutions bring stronger short waves through embedded int
the upper level flow. These waves...when timed to combine with
surface heating...may create enough instability to produce some
isolated showers and/or thunderstorms...but the timing and
strength of the the waves is uncertain at this time. Inland high
temperatures Tuesday through Thursday look to be within a few
degrees of the Monday highs.

&&

.AVIATION...21/18Z TAF cycle...MVFR stratus along the coast to
the coastal mountains will continue through this afternoon...lowering
to IFR this evening and tonight then continuing into Friday
morning. Inland expect VFR conditions today with isolated MVFR
cigs in the Umpqua Valley. Isolated showers are possible from the
coast to the Cascade foothills this afternoon and early evening.
Isolated thunderstorms this afternoon and evening as well from
Crater Lake northeast to northern Klamath and extreme northwest
Lake County. Low level westerly to southwesterly winds will be
strong this afternoon and evening...strongest east of the
Cascades. MVFR cigs will become widespread again this evening into
tonight for the Umpqua Valley and continue into Friday morning.
-CC

&&

.MARINE...Updated 1000 AM PDT Thursday 21 July 2016...Winds and
seas will remain light and there is a slight chance of showers
through tonight as broad, weak low pressure remains over the area.
On Friday, the pattern changes to high pressure aloft and a thermal
trough developing along the coast. This pattern will then continue
through the weekend and possibly through all of next week. There
will be an increase in north winds on Friday with advisory level
winds forecast to develop south of Cape Blanco. Stronger north winds
will follow with the winds south of Cape Blanco either at the high
end of advisory criteria or reaching gale force while low end
advisory level winds develop north of Cape Blanco. -DW/CC

&&

.FIRE WEATHER...Updated 600 AM PDT Thursday 21 July 2016.
There is relatively little change to the previous forecast.
Conditions will be of greatest concern today as a low off the coast
moves inland. This will create weak instability with a slight chance
of a thunderstorm or two during the afternoon and evening from the
southern Oregon Cascades northeastward into northern Klamath County.
More notable will be low humidity and strong gusty winds this
afternoon and evening. These winds will veer from south-southwest to
northwest with strong winds in Siskiyou County and Klamath County
including the Shasta Valley and Klamath Valley. But, the winds will
be stronger and humidities lower farther to the east. A red flag
warning has been issued for critical fire weather conditions in
Modoc County and east of the Klamath Valley in south central Oregon.
This includes Northern California fire weather zone 285, the
southeast portion of Oregon fire weather zone 624 and also zone 625.

There will be modest improvement on Friday with a couple degrees of
cooling and weaker winds. But, a warming trend will follow with hot,
dry, and breezy conditions expected from the weekend through at
least the first half of next week. A surface thermal trough will
develop along the coast and result in periods of breezy east winds
over the coastal ridges and the ridges in Western Siskiyou County.
Moderate humidity recoveries on many area ridges are expected this
weekend into next week. -DW

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Red Flag Warning from 2 PM this afternoon to 8 PM PDT this
        evening for ORZ624-625.

CA...Red Flag Warning from 2 PM this afternoon to 8 PM PDT this
        evening for CAZ285.

Pacific Coastal Waters...Small Craft Advisory from 11 AM Friday to
        11 AM PDT Saturday for PZZ356-376.
     Small Craft Advisory for hazardous seas from 11 AM Friday to
        11 AM PDT Saturday for PZZ356-376.

15/15/18