Scientific Forecaster Discussion
fxus66 kmfr 210349
Area forecast discussion
National Weather Service Medford or
849 PM PDT sun Oct 20 2019
no updates are needed this evening as the forecast for tonight
through tomorrow is on right on track.
Precipitation amounts today were light and mostly confined to
Douglas County despite plenty of clouds over the forecast area.
During the next 24 hours we'll see a subsidence inversion lower
across the forecast area as high pressure builds in from the
southwest. This will result in a warming and drying trend.
Temperatures on Monday will be very close to the 1981-2010 calendar
day averages, which are 41/67 for Medford and 30/60 for Klamath
Aviation...for the 21/00z tafs...coast and Umpqua basin...MVFR
ceilings are expected through the evening with limited shower
chances and patchy IFR. Ceilings are likely to lower and thicken to
IFR and more widespread mountain obscuration into Monday morning. No
LIFR conditions were included in the tafs with the reduced rainfall,
but isolated pockets are certainly possible. Some improvement to VFR
is expected late Monday morning or early Monday afternoon.
Elsewhere, showers through this evening will be less numerous with
areas of mountain obscuration and mainly VFR ceilings. Patches of
valley MVFR/IFR are likely late tonight into Monday morning; though
IFR is more likely in the Klamath Falls area if it does occur.
Improvement is expected late Monday morning.
Marine...updated 830 PM PDT Sunday 21 October 2019...west
swell will continue to lower slowly today. But, south winds will
remain moderate through the morning. The combination of wind waves
and swell will produce steep seas north of Cape Blanco and within 10
nm from shore. These conditions should diminish below those
hazardous to small craft by early morning.
High pressure builds over the offshore waters and will build in
Monday, weakening a front that will brush the waters north of Cape
Blanco late Monday night into Tuesday.
High pressure aloft will strengthen mid-week with a thermal trough
deepening over the South Coast. This will result in gusty north
winds and likely steep to very steep wind driven seas, with the
strongest winds and highest seas south of Cape Blanco. This pattern
will persist into Thursday. -Keene/miles
Previous discussion... /issued 240 PM PDT sun Oct 20 2019/
Discussion...the latest visible image shows plenty of mid
and low level clouds over the area. The radar is showing very light
returns with no areas having reported any precipitation for the last
several hours. A warm front will move into the area this evening and
there still could be intermittent light rain, mostly north of the
Umpqua Divide and Cascades. The latest short range high res guidance
shows very little quantitative precipitation forecast through this evening. Any precipitation will
end overnight tonight as the warm front lifts north of the area and
upper ridging builds in. Some clearing is expected overnight tonight
and if there's enough clearing, then patchy fog could develop in
most of the west side valleys late tonight into Monday morning.
Monday will be dry and milder with decreasing cloud cover. The upper
ridge will flatten out some Tuesday as a weak shortwave rides over
the ridge. At the same time a weak cold front will slowly sink south
towards our forecast area bringing at least a slight chance of
precipitation mainly north of the Umpqua Divide and northern
Any precipitation will end Tuesday evening with dry weather
returning Tuesday night and lasting through Wednesday as upper
ridging builds in. At the surface a thermal trough will develop
along the coast with increasing offshore flow. In fact the pattern
is favorable for a Chetco effect to take hold and we could see high
temperatures in Brookings and Red Mound pushing close to 80 degrees
f. Did not go that warm right now, but this will have to be
re-evaluated. It will also be milder for most inland locations.
Long term...Thursday, Oct 24 through Sunday, Oct 27, 2019...
deterministic and ensemble guidance is in good agreement throughout
the extended forecast period, thus confidence in the forecast is
good. We start out with a strong upper level ridge in place over the
Pacific northwest on Thursday. This will mean generally clear skies
and warmer than normal temperatures. This will be especially true
along the Curry coast where offshore flow and a potential Chetco
effect will set the stage for very warm weather. The majority of the
guidance shows temperatures well into the 70s in the Brookings area
Thursday, but some statistical guidance has it into the mid-80s.
While there isn't much question that the potential is there, we
won't go all the way just yet, but temperatures have been bumped up
over most guidance. It will be warm elsewhere, as well, with
temperatures likely around 10 degrees above normal.
A fairly substantial system will knock the ridge down Friday into
the weekend, but the majority of the dynamics and moisture will
likely remain north and east of US. We could see some light
precipitation north of the Umpqua Divide later Friday into Saturday
morning, but elsewhere, it is expected to remain dry through the
weekend. Depending on the timing of arriving cloudiness, Friday will
probably still be warm, but conditions will cool down significantly
over the weekend under cool, northerly flow. -Wright
Pacific coastal waters...
- Small Craft Advisory until 11 PM PDT this evening for