Wildfire in Oregon, July 28 to 31, 2016

Area Forecast Discussion
National Weather Service Medford OR
926 AM PDT THU JUL 28 2016

.DISCUSSION...A few minor changes were made to the forecast this
morning, otherwise the overall idea remains the same. Continued
hot and dry conditions for the next couple of days. ^The main
concern ahead will be the potential for isolated thunderstorms
late Friday afternoon and evening and again Saturday afternoon and
evening. A preliminary look at the data does not show anything
significantly different. However they do suggest the best chance
for storms (if any were to develop) will be in portions of
Siskiyou County late Friday afternoon and evening, then the focus
for isolated storms shift east to northeast in southern Lake and
Klamath Counties late Saturday afternoon and evening. There's even
an argument that the focus for isolated storms on Saturday could
be mainly confined to Lake County, but we'll have look at this in
more detail. There is also some concern for nocturnal storms
overnight Friday in parts of northern Cal as the weak upper trough
moves inland in northern Cal/southern Oregon. This is due in part
to available moisture and slightly stronger trigger. -Petrucelli

&&

.AVIATION...28/12Z TAF cycle...VFR conditions will continue for the
next 24 hours at inland locations. IFR to LIFR marine stratus will
persist at the coast westward, especially from Cape Blanco northward
and into the Coquille Valley, through around 18Z this morning before
eroding back into the coastal waters. IFR ceilings will surge back
into the same areas late this afternoon into the evening. Moderate
to strong and gusty north winds are expected for most areas along
the coast and offshore, though with a decrease during the early
morning hours. BTL/DW

&&

.MARINE...Updated 235 AM PDT Thursday, 28 July 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 seas through the weekend and into next week. Conditions will
be most hazardous north of Cape Blanco today through Friday evening.
South of Cape Blanco the most hazardous conditions are expected to
be on Saturday. BTL

.FIRE WEATHER...Updated 655 AM PDT Thursday, 28 July 2016...
Moderate to locally poor humidity recoveries (30-50%) with light to
moderate east winds (Gusts 10-20 mph) across the upper slopes and
ridges of northern California and the East Side this morning will
repeat again tonight through Friday morning. These winds will then
generally persist through the weekend into early next week with
only brief rise in humidities. Yesterday unexpected gustiness in the
Modoc led to a period of critical wind/RH conditions there in the
afternoon and evening. Low afternoon and evening humidities are
expected again today, but with weaker late day breezes.

Building heat will peak Friday before temperatures cool to near
normal values through early next week. A weak low west of California
is expected to draw in elevated monsoonal moisture Friday into
Saturday bringing a slight chance of afternoon and evening
thunderstorms from the Salmon Mountains east-northeastward into
southeastern Oregon. Initially, moisture is near and above the
freezing level and could be capped in the Salmon Mountains to Mount
Shasta area. Friday evening some activity could develop across the
Modoc and/or drift in from the south. Saturday a more organized
shortwave associated with a cold front will bring a potential along
and north of the high terrain from Mount Shasta and Medicine Lake
northeastward onto the Modoc Plateau to souther Lake County. Gusty
winds will low humidity Sunday into Monday may reach critical
levels east of the Cascades. BTL

&&

.PREV DISCUSSION... /Issued 705 AM PDT THU JUL 28 2016/

SHORT TERM...A broad upper level ridge will remain in place over
the region through Friday. At the surface, high pressure offshore
and a thermal trough along the coast will bringing gusty
northeast flow to the coastal mountains and gusty northerly winds
during the afternoon and evening to the coast. Hot temperatures
are expected inland through Friday. Conditions will be dry today
then some mid level monsoon moisture is forecast to move into the
area Friday and may bring a slight chance for thunderstorms to
southern portions of the area. An upper trough will move inland
north of the area late Friday and Saturday then remain in place on
Sunday. This will bring slightly cooler temperatures on the
weekend. Additionally ahead of the front, gusty winds and
thunderstorms are possible east of the Cascades on Saturday.

Today, the main focus remains on the hot and dry conditions.
Temperatures are expected to warm into the triple digits for valley
locations across Northern California and into the Rogue, Illinois
and Applegate Valleys in Southern Oregon. Other inland valleys in
Southern oregon will see highs in the mid to upper 90s.

These hot temperatures continue into Friday. Additionally, some
mid level moisture moving up from the south may come into play on
Friday and will bring a slight chance for thunderstorms in
portions of Siskiyou County, Modoc County and southern Klamath
County. There is high confidence that there will be cumulus build
ups Friday afternoon into Friday evening. Models support a slight
chance for thunderstorms as well, showing mid level moisture
advection and weak instability moving into southern portions of
the CWA. Of note, the models continue to show only weak shortwave
triggers moving into the area on Friday, which may limit the
thunderstorm potential. Have leaned towards the slight chance for
storms given the monsoon moisture and potential for s high based
thunderstorms which may produce gusty outflow winds. Additionally,
any storms that develop over eastern portions of the area may not
have significant rain with them, especially over the Modoc County
area where cloud bases are forecast to be high, sub cloud
conditions are dry and storms motion is expected to be around 10
kts. In Siskiyou County, expect any storms that form to be slow
moving.

On Saturday, an upper trough will move inland to the north and a
front will push into the area. The front combined with lingering
mid level moisture and instability will bring a chance for
thunderstorms for areas east of the Cascades in Eastern Siskiyou,
Modoc, Southern Klamath and Southern Lake Counties. Additionally
winds are forecast to increase and become gusty east of the
Cascades late Saturday afternoon and evening. Temperatures will
be slightly cooler on Saturday over the area as the upper trough
moves inland but still expect very warm temperatures in the 90s
for most inland valleys.

Somewhat cooler conditions will develop on Sunday with high
temperatures in the mid 80s to mid 90s for most inland valleys.
Although relatively cooler, temperatures will still be above
normal by about 3 to 5 degrees on Sunday. Early in the day, expect
a marine push of low clouds along the Coos and Douglas County
coast and into the Umpqua Valley Saturday night into Sunday
morning. These clouds will clear off during the day Sunday.

LONG TERM...Another trough is expected to move inland north of
the area on Monday and Tuesday then shift eastward on Wednesday.
This pattern will bring sightly above normal to near normal
temperatures early next week. Conditions are expected to remain
dry. Additionally, expect gusty west winds on Monday ahead of
this next trough with strongest winds east of the Cascades in the
late afternoon and evening.

&&

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

CA...None.

Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT Sunday for
     PZZ350-356-370-376.
     Hazardous Seas Warning until 11 PM PDT Sunday for PZZ356-376.
     Hazardous Seas Warning until 11 PM PDT Friday for PZZ370.
     Gale Warning until 11 PM PDT Sunday for PZZ376.