• Currently

    Reported at Medford, Rogue Valley International Airport, OR
    4:53 AM PST THU JUL 27 2017
  • 68°F20°C
  • Clear
  • Feels Like:68°F20°CDew Point:54°F12°CHumidity:60% Winds:SSW 3 mph 5 kph
    Pressure:30.09 in1019 hPaVisibility:10.00 miles16090.00 meters
  • Area Forecast Discussion

439 AM PDT Thu Jul 27 2017

.Updated marine weather discussion.

.DISCUSSION...The thunderous stretch of the past several days has
come to an end in our forecast area as the upper low that pulled
moist unstable air into the region has exited, stage right.
Heights will slowly rise over the region into the weekend, with a
thermal trough deepening along the coast. The deepening trough
will increase offshore flow as we head into the weekend and
contribute to temperature rising above 100 degrees in the Rogue
valley and near 110 degrees in the Western Siskiyou county
valleys on Saturday. Increased offshore flow will bring Chetco
effect heating to the southern coast and have increased high
temperatures Friday and Saturday, and low temperatures Friday
night a good deal above guidance on the extreme southern coast and
the southern coastal range. Southerly low level flow returns
Sunday and starts to feed most unstable air into the region and
returns a slight chance of thunderstorms to the region Monday from
Western Siskiyou county and to the east and northeast, from the
cascades across the east side. Sven


.AVIATION...27/06Z TAF CYCLE...Along the coast...IFR cigs and
visibility will prevail north of Cape Blanco the rest of tonight
through about 20z Thursday, then scatter out thereafter with gusty
north winds developing again Thursday afternoon. South of Cape
Blanco, VFR this evening will become IFR again overnight into
Thursday before clearing out in the afternoon.

Models continue to indicate a deeper marine push into the Umpqua
Basin with some lower ceilings developing at KRBG toward
morning. Confidence here isn`t high, so have indicated just a
scattered deck around 3000 feet in the morning, but there is a
chance of MVFR ceilings for a couple of hours. Either way, VFR will
prevail there after 18z. VFR is expected across the remainder of the
inland west side. Breezy NW winds at KMFR could gust to near 20
knots toward 00Z. /FB


.MARINE...Updated 430 AM PDT Thursday 27 July 2017...The thermal
trough pattern and northerly winds will remain in place into next
week. Small craft advisory conditions will persist south of Cape
Blanco through Friday morning. Then the thermal trough strengthens
some and gales will be possible south of Cape Blanco with small
craft advisory conditions likely reaching north of Cape Blanco. The
strongest winds are expected in the afternoons and evenings, and
they will be closest to the coast during these times as well. Models
suggest the strong north winds south of the Cape will persist
through Sunday. SK


.FIRE WEATHER...Updated 350 AM Thursday 27 July, 2017...
After days of thunderstorms (4448 total cloud to ground lightning
strikes in the forecast area since the weekend) mainly from the
Siskiyous and Cascades eastward, and patches of wetting rains, we
are transitioning to drier and hotter conditions. This trend will
begin to erase any temporary dampening effects from rainfall over
the past couple days and promote the growth of sleeper fires in the
area. Additionally, the relatively weak general winds of the past
several days will begin to increase to moderate, more typical
afternoon breezes. A disturbance aloft will enhance surface winds
locally on the West Side today and moreso east of the Cascades on
Friday. Specifically, Modoc County will likely return to its typical
20mph+ afternoon west to southwest winds. Furthermore, GFS20 output
suggests the potential for very dry and unstable conditions
affecting new fires in Modoc County (FWZ 285) on Friday afternoon.
We have issued a Fire Weather Watch for that. Trends from model runs
of the past several days lean drier for Friday, and this nudged us
to issue the Watch. Will examine today to see if confidence
increases and warrants a Warning.

Given the thermal trough pattern strengthening along the coast and a
hot air mass overhead, east winds and moderate to poor overnight
humidity recoveries become a concern Friday night and Saturday night
at least. Latest data does not support conditions reaching critical
criteria, so will be headlining in the Fire Weather Forecast for now.

In summary, hotter and drier conditions will increase potential for
fire growth after this long-duration lightning event. High
temperatures will affect fire crews as afternoon readings reach
about 10 degrees above normal during this hottest time of the year,
from this weekend through next week at least. Long-term guidance
suggests no relief from the hot conditions through next week. SK




Pacific Coastal Waters...Gale Watch from Friday morning through
Sunday evening for      PZZ356-376.      Small Craft Advisory until
11 PM PDT Sunday for PZZ356-376.      Small Craft Advisory from 11
AM Friday to 11 PM PDT Sunday for      PZZ350-370.