Scientific Forecaster Discussion
fxus66 kmfr 232153
Area forecast discussion
National Weather Service Medford or
253 PM PDT Fri Aug 23 2019
temperatures across areas inland from the coast are currently
running about 10 degrees above where they were this time
yesterday. Along the coast, however, temperatures are down
compared to yesterday- as much as 11 degrees in the Brookings
Tonight through Saturday morning we're expecting marine layer low
clouds and fog to develop again from about Cape Blanco northward
and into much of Coos County. A frontal system pushing in north of
US will increase the onshore flow along the coast a little, but
not much, as it will be riding by to the north. This frontal
system and cooler northerly flow behind it will serve to knock
temperatures down some this weekend, primarily on the west side,
though not by more than about 5 degrees from today's highs.
We're still expecting a fairly robust late season heat wave to
commence Monday and persist through Thursday, with the hottest
days on Tuesday and Wednesday. Current expectations are that
Medford will reach 104f and 102f on Tuesday and Wednesday, which
is within a couple of degrees of daily record highs for each of
those days. We anticipate issuing an excessive heat advisory or
watch for this heat wave sometime this weekend.
A shortwave trough is expected to ride northward in southerly flow
Wednesday into Thursday of next week. At this point, we've
expanded the thunderstorm threat a bit for Thursday based on
signals from the GFS and gefs mean. At this point, it does appear
that we'll probably see some thunderstorms across the area
Wednesday into Thursday (even possibly Wednesday night), but
pinning it down to where and when at this lead time is not
possible. Therefore, we'll be honing in on that time period for
future updates to the forecast. Btl
Fire weather...updated 200 PM PDT Friday 23 August 2019...it will
remain dry through at least the middle of next week. There are two
main short term concerns. First will be gusty winds east of the
Cascades Saturday afternoon and evening with low relative humidity.
Second is breezy winds with moderate to locally poor overnight
recoveries near and at the ridges in fire zones 618, 619 and 620
Sunday night and Monday night. However were not expecting any
critical fire concerns in these areas, therefore we'll just
highlight it in the fire weather forecast.
The main driving force for gusty winds east of the Cascades Saturday
afternoon and evening will be stronger winds aloft (at 700 and
600mb) along with an increasing pressure gradient and it will bring
speeds stronger than normal at 12 to 18 mph with gusts up to 25 mph.
Temperatures will be warmer today this afternoon compared to
yesterday and won't vary much through the weekend. This is because
we'll have a weak upper trough will slip into the region tomorrow
into Sunday. Therefore, temperatures won't change much, if at all
for most locations. However relative humidity may come up just a
The hottest and driest conditions are likely on Monday, Tuesday and
Wednesday with triple digit readings likely for interior Westside
valleys Tuesday and Wednesday.
The first hint any potential thunder could be Thursday afternoon and
evening. It's not a slam dunk, but something we'll keep a close
watch on. -Petrucelli
Aviation...for the 23/18z tafs...
VFR conditions are expected to prevail until this evening when areas
IFR and LIFR are expected to begin to develop along and near the
Douglas and Curry County coastlines. Overnight IFR to LIFR low
clouds and fog are expected to develop in these areas, as well as
further inland into the Coquille River Valley. Overall, conditions
are expected to be very similar to what was observed this morning
along and near the coast. We're not expecting as much fog and low
cloud development into interior Douglas County as we saw in the last
24 hours, however. Dissipation time for coastal and near coastal
areas is likely to be a little slower than it was today due to a
slightly stronger onshore component to the flow related to a frontal
system brushing by from the north. Btl
Marine...updated 230 PM PDT Friday, 23 August 2019...
a thermal trof along the coast will weaken overnight tonight. This
will result in winds decreasing over most of the coastal waters.
However, the thermal trof will stay just strong enough to keep seas
rather steep south of Cape Blanco. So, have cancelled the hazardous
seas warning and replaced it with a Small Craft Advisory. Also, have
cancelled the Small Craft Advisory for areas north of Cape Blanco.
This will be short lived as the thermal trof strengthens Sunday
afternoon and becomes very strong Monday and Tuesday. This will
crank up the winds again and the steep seas will return. Could see
gales also but for now, have issued a hazardous seas watch for the
outer waters south of Coos Bay beginning Sunday afternoon. -Sargeant
Pacific coastal waters...
- Small Craft Advisory until 11 am PDT Sunday for pzz356-376.
- Hazardous seas watch from Sunday morning through Tuesday
morning for pzz370-376.