Area Forecast Discussion
Issued by NWS Medford, OR

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316
FXUS66 KMFR 250545
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
1045 PM PDT SUN JUL 24 2016

.UPDATE...See Aviation Discussion below.

&&

.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


&&

.PREV DISCUSSION... /Issued 801 PM PDT SUN JUL 24 2016/

DISCUSSION...Stratus low clouds are moving quickly inland this
evening, approaching Scottburg in NW Douglas County as of 730 PM.
In Coos County stratus has moved past Myrtle Point. The question
remains whether the low clouds will make it all the way into
Roseburg by morning. The 18Z GFS MOS for Roseburg introduced some
clouds but not quite the ceiling. This would suggest widespread
low clouds into the Sutherlin area with scattered low clouds for
Roseburg. We have updated the sky grids to reflect quicker
movement inland of these low clouds.

The latest 00Z NAM12 model shows no major changes. Warm and dry
weather continues next week and 100 degrees possible for the high
in the Rogue Valley from Wednesday onward. /FB

AVIATION...25/00Z TAF cycle...Stratus with MVFR CIGS has already
moved onto the Coos Coast this evening and will continue to slowly
edge inland due to a moderate marine push. Latest guidance continues
to indicate that stratus is unlikely to reach KRBG, but given the
strength of the push, it remains possible nonetheless. Elsewhere,
VFR conditions are expected to continue. -Wright

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 elsewhere.

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

PREV DISCUSSION... /Issued 200 PM PDT SUN JUL 24 2016/

DISCUSSION...24/12Z NAM/GFS/EC in.

Clear skies this afternoon over the Medford CWA...except for some
areas of marine stratus over the coastal waters..

Flow aloft remains nearly westerly this afternoon. The upper
level pattern will alternate between weak zonal flow and weak
troughing through Wednesday...with little in the way of short wave
activity over our area. The ridges of the coast range will be dry
and breezy during the overnight hours due to low to moderate...but
persistent...easterly low level flow. The thermal trough is also
supporting strong winds over the coastal waters.

Temperatures will change little between today and Tuesday.
Highs in the Umpqua Basin will be near normal. Inland highs over
the remainder of the area will be 5 to 10 degrees above normal.
One exception will be the Brookings area...where easterly low
level flow will allow high temperatures to warm to 10 to 15 degrees
above normal Tuesday.

Upper level ridging will build in more strongly Wednesday into
Thursday...bringing hotter temperatures to the area. Inland highs
Thursday will warm to 5 to 10 degrees above normal over Oregon and
10 to 15 degrees above normal over northern California.

The ridge will begin to weaken Thursday into Friday as short waves
embedded in the westerly flow move through...but inland
temperatures will keep on warming. Thursday highs will be 10 to
15 degrees above normal. Friday highs will be similar to the
Thursday highs over northern California and east of the
Cascades...but the thermal trough will move over the west
side...and highs there will be 2 to 3 degrees higher than the
Thursday highs.

The ridge will weaken further Saturday as more short waves move
through and a long wave trough approaches from the west. Inland
temperatures will cool a few degrees. At this time Saturday still
looks to be the most favorable day for thunderstorm activity. It
will likely be too dry for any activity Friday. On Sunday...the
approaching trough will induce stronger southwest flow aloft...
which will shunt the activity to the east of the Medford CWA.
Inland areas will cool down next weekend...and by Sunday inland
highs will be 2 to 7 degrees above normal.

AVIATION...24/18Z TAF cycle...North winds will increase again along
the coast around noon with gusts to 30 knots expected at KOTH into
the evening. Latest model data suggests a stronger marine push this
evening and overnight, so MVFR then IFR conditions are expected
tonight and Monday morning at KOTH, and a short period of MVFR
conditions is possible at KRBG. We have, however, kept ceilings out
of the KRBG TAF at this time due to low confidence. Elsewhere, skies
are expected to remain clear through Monday. SK

MARINE...Updated 100 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
elsewhere.

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.
-SK/DW

&&

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

CA...None.

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.

$$

FJB/FJB/FJB



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