Area Forecast Discussion
Issued by NWS Medford, OR
FXUS66 KMFR 262138
Area Forecast Discussion
National Weather Service Medford OR
238 PM PDT TUE JUL 26 2016
.DISCUSSION...Not much change is expected for the rest of the
week. It will remain dry and hot inland away from the coast.
Current visible image shows clear skies over the entire area,
except for the outer marine waters. Even then clouds there are
retreating and most should be gone by late this afternoon. Triple
digit temperatures are possible for many of westside valleys
locations including the Rogue, Illinois and Applegate valleys in
Oregon and the valleys in Siskiyou County on Wednesday. There`s a
better chance for triple digits in these same areas Thursday and
Friday. Models vary with the 850 mb temperatures, but suggest
temperatures will hit their peak Thursday and Friday.
Relief in a relative sense is on the way this weekend. The models
agree there will be a pattern change this weekend, but differ with
some of the details. Cooling will take place staring on Saturday
with max temperatures averaging 5-10 degrees lower than Friday,
but will still be above normal. Earlier model runs suggest there
may be enough instability for isolated thunderstorms to be a
concern for portions of Northern Cal and east of the Cascades.
However the past couple of runs (last night and this morning) have
shown marginal instability at best, mid level moisture is
noticeably absent and there is no trigger. Therefore we took any
mention of thunderstorms out for Saturday afternoon and evening.
However, this will still need to be monitored in the days to come.
Further cooling is expected Sunday, but it remains to be seen how
much cooling there will be. The EC shows a stronger shortwave
swinging over the northern portion of our area. In contrast, the
GFS does not and shows a west to northwest flow. Neither model
is conducive for thunderstorm development, so were expecting it
to remain dry. The bigger concern (especially for the fire weather
folks ) will be gusty winds east of the Cascades Saturday ahead of
a cool front and behind it on Sunday.
There`s general agreement a pattern shift will set up for the
early part of next week with the mean ridge shifting over the
eastern third of the U.S. and a general troughiness over the Pac
NW. This would at least result in temperatures near normal, but
remaining dry. -Petrucelli
.AVIATION...26/18Z TAF cycle...VFR conditions will continue area-
wide through early evening. Stratus with IFR CIGS is expected to
form again this evening along the coast, and it may spill into the
Umpqua basin overnight but is not expected to reach KRBG. Elsewhere,
VFR conditions will continue through the TAF period. -Wright
.MARINE...Updated 2:00 PM PDT Tuesday, 26 July 2016...
A strong and persistent thermal trough along the coast and high
pressure offshore will continue to produce strong north winds and
steep to very steep wind driven seas through this week and into the
weekend. Gales will continue south of Cape Blanco beyond roughly 5
NM from shore with small craft advisory level conditions elsewhere.
Winds will be strongest and seas will be steepest during the
afternoons and evenings.
Surface pressure gradients tighten through at least Thursday, and
winds just above the surface increase to as much as 50 kt. As a
result, the area of gales is expected to expand and there may be
occasional storm force gusts over a small area west of Brookings
between approximately 10 and 40 NM from shore. At that time, gales
may also briefly affect the waters north of Cape Blanco, but not
enough to warrant expansion of the Gale Warning north of the Cape.
What is more likely to occur north of the Cape, at times, is 9 foot
seas, primarily in the evening hours. Sven
.FIRE WEATHER...Updated 130 PM PDT Tuesday, 26 July 2016.
A coastal thermal trough pattern will dominate our weather through
the remainder of the week. Expect hot, dry conditions inland from
the coast with typical afternoon breezes. At the Curry coast and
over the coast ranges, offshore (east-northeast) flow is expected to
produce warm conditions with moderate to poor night time humidity
recoveries. The coast itself will likely recover well most nights,
but daytime conditions will be warm and dry.
The thunderstorm threat for Saturday has lessened, and while a storm
cannot be entirely ruled out, they were removed from the forecast.
The bigger concern is the potential for a dry cold front and the
gusty winds that may occur both ahead of the front on Saturday and
behind it on Sunday. Humidities will remain low over the weekend, so
the combination of low humidity and gusty winds will lead to at
least elevated fire danger, especially for east side locations.
The front will disrupt the thermal trough pattern over the weekend
with better humidity recoveries over the coast and adjacent
mountains. It will also bring a cool down area wide which will
eventually bring humidities up a few percent, at least west of the
Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Monday for
Gale Warning until 5 AM PDT Monday for PZZ356-376.