Area Forecast Discussion
Issued by NWS Medford, OR
FXUS66 KMFR 251056
Area Forecast Discussion
National Weather Service Medford OR
356 AM PDT MON JUL 25 2016
.DISCUSSION...Stratus is spilling into the umpqua basin this
morning behind a weak trough that moved through the area earlier.
this weak marine push will bring a day of similar to slightly
cooler temperatures to the region today. Heights slowly rise with
the thermal trough on the coast bringing offshore flow that will
spread across the east side by Wednesday morning. this offshore
flow will be briefly interrupted by weak marine pushes Tuesday
morning and Thursday, but this will not intrude much from the
coast. The upper level ridge continues to build into the end of
the work week with the thermal trough shifting inland Friday,
bringing the hottest stretch of the week. The GFS 850 temps
support a high of around 99 at Medford while the EC supports a
high of around 107. With uncertainty have gone with a compromise
of 103 for Friday at Medford. The GFS is indicating instability
over the Cascades and western Siskiyou county Friday, but the
700-500 MB RH is less than 40 percent over most of the area, and
barely above 60 percent in western Siskiyou county. current
thinking is that Friday will be the "prime the pump" day. Saturday
still looks better for convection. However, the area of
instability is shifted south from the Trinity alps to the Mt
Shasta area and to the northeast into southern lake county.
Steering flow is from the west at around 15 kt and should be
strong enough to dislodge any storms that develop from the
terrain. With only a weak short wave moving through, am keeping
chance at slight at this time. Sven
.AVIATION...25/06Z TAF cycle...Stratus with MVFR CIGS is
banking against the coastal range as of 05Z and is trying to spill
into western Umpqua Valley due to a moderate marine push. Latest
guidance now indicates that stratus is likely to reach KRBG as the
coastal mountains between Coos and Douglas Counties go up to around
2800 feet. The stratus could also spill over the Umpqua divide into
the Illinois Valley. Terrain will be obscured. Elsewhere, VFR
conditions are expected to continue but southern end of Jackson
County could see MVFR cigs near Ashland around day break. /FB
.MARINE...Updated 800 PM PDT Sunday 24 July 2016...A thermal
trough along the coast and high pressure offshore will produce
strong north winds and wind driven seas over the waters through the
week. Gales are certain over the waters south of Cape Blanco beyond
roughly 5 NM from shore with small craft advisory level conditions
On Tuesday, surface pressure gradients tighten considerably, and
winds just above the surface increase to as much as 50 kt. As a
result, the area of gales expands, and there may be a small area
over the southern outer waters where winds approach storm force.
This also the most likely time when gales could affect a small
part of the northern zones as well. -Wright
.FIRE WEATHER...Updated 110 PM PDT Sunday 24 July 2016.
Hot and dry weather will continue through the week. Breezy north
winds are expected west of the Cascades the next several afternoons.
East Side winds will be relatively light today with typical
afternoon breezes but will trend higher Monday afternoon.
A Haines Index of 6...indicating very dry and unstable
conditions...is expected east of the Cascades this afternoon. Areas
west of the Cascades will feature a Haines Index value of 5, with
more stable conditions compared to the East Side.
The long-duration surface thermal trough will continue to bring
periods of breezy northeast overnight winds and moderate humidity
recoveries through Thursday at the coast and in Western Siskiyou
County. Moderate humidity recoveries are also expected east of the
Cascades through Thursday. Wednesday morning is beginning to look
like the driest and windiest of the week for the high terrain in
Western Siskiyou and Curry counties. Humidity recoveries could be
poor there overnight Tuesday into Wednesday morning with east to
northeast wind gusts to 30 mph. Weak instability is expected to
produce a few buildups on Friday then increase on Saturday for a
slight chance of thunderstorms.
Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT Friday for PZZ350-356-370.
Gale Warning until 11 PM PDT Friday for PZZ356-376.
Small Craft Advisory until 11 AM PDT Tuesday for PZZ376.