Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus66 kmfr 152147 
afdmfr

Area forecast discussion
National Weather Service Medford or
247 PM PDT sun Sep 15 2019

Discussion...a strong and well defined front is knocking on our
doorstep. Moderate to heavy rain has already reached the coast. In
fact North Bend already picked up 0.45 of an inch of rain as of noon
and it starting raining there around 930 am PDT ans Brookings
recieved a whopping 0.70 of an inch in just 2 hours as of 2 PM PDT.
Meanwhile along and east of the Cascades, moderate to strong winds
are occurring, especially over the higher terrain.

The front will continue March inland early this evening and tonight
with moderate to heavy rain along and just ahead of it. Plenty of
dynamics exist with this front, so could not rule out isolated
thunderstorms over the marine waters and along the coast this
evening and tonight. Altogether, we're still expecting a 0.50" to
1.50" from the Cascades westward, except in the Scott Valley
northwest to the Klamath River, and in the Grants Pass area, where
amounts are more likely to be 0.30" to 0.50". 0.25" to 0.50" is
expected for most of the east side, except 0.10" to 0.30" is
expected in the drier portions of lake and Modoc counties.

Anyone venturing above the 8,000 foot elevation tonight through
Monday should expect moderate to heavy snowfall and near blizzard
conditions for about a 6 hour period as the front moves through.

Following the front will be an upper level trough bringing in cold
air aloft. So, we'll see a transition from steady rain to showers
later this evening and tonight. Also isolated thunderstorms are
possible over the marine waters. Scattered showers are likely for
the entire area Monday. Depending on the amount of surface heating,
instability could be sufficient enough for isolated thunderstorms
Monday afternoon and evening for most inland locations. Winds won't
be as strong Monday, but could not rule out gusty winds near any
thunderstorms.

We'll catch a brief break in the action Monday night, but another
front will be on the heals of this one. This front is expected to
bring stronger winds over the coastal waters as a low level jet
stream develops. Rainfall is likely to be most focused along and
near the coast, coastal mountains, and Cascades.

Following tuesday's front will be another upper trough with cold air
aloft. So we'll likely see scattered showers behind the front
Tuesday night through Wednesday.

Depending on the progression of the wednesday's upper trough.
Thursday could be transition day with the best chance for showers
in eastern Klamath, lake and Modoc County. Friday and Saturday look
dry and milder as upper ridging builds offshore followed by another
front Sunday. -Petrucelli



&&

Aviation...for the 15/18z tafs...VFR will prevail from the
Cascades eastward this afternoon with S-SW winds gusting to
30-40 kt, highest mainly south and east of Klamath Falls. There could
be enhanced turbulence on approaches/departures through this evening.

Widespread MVFR ceilings with areas of IFR ceilings and visibility
in rain will impact the coast, then spread inland to the Cascades by
this evening. Areas of higher terrain will become obscured. MVFR
ceilings, local IFR and terrain obscurations will then spread east
of the Cascades overnight into Monday morning. Precipitation will
become more showery on Monday, with conditions mostly varying
between MVFR/VFR, though higher terrain could remain obscured.
Isolated thunderstorms are possible along the coast in the morning,
then inland during the afternoon. -Spilde



&&

Marine...updated 230 PM PDT Sunday 15 September 2019...seas will
remain hazardous to smaller crafts this afternoon as a front
moves through the waters. Gale force winds will be possible on
Tuesday, mainly north of Cape Blanco. Hazardous seas will be
likely with this frontal passage on Tuesday as seas will be high
and steep to very steep. As a low moves eastwards, the waters will
probably remain hazardous to smaller crafts from Tuesday night
into Wednesday as seas remain high and steep. High pressure and
lower seas are expected Friday into Saturday.

&&

Fire weather...updated 130 PM PDT Sunday, 15 September 2019...
very windy conditions are developing east of the Cascades early this
afternoon with several RAWS sites already notching wind gusts in the
35-45 mph range. A new wildfire was reported in the Hart Mountain
area and can easily be seen in GOES-17 imagery this afternoon. Rhs are
expected to drop into the 8-15% range, so the red flag warning that is
out for those areas is on track. Expect these gusty winds to continue
into the evening hours and while they won't completely subside
overnight, the strongest wind gusts should end by around 8 PM.

After that, fire weather concerns diminish substantially with
widespread wetting rainfall expected with a cold front tonight into
Monday with a huge cool down east of the Cascades. Rain is already
falling along the coast and into the Umpqua valley with arrival times
late this afternoon and evening in the Rogue Valley/Cascades, then
overnight into Monday morning south and east of the Cascades (including
across the rest of northern california). Rain amounts of 0.50-1.00 inch
will be common from the Cascades westward (more along the coast) with
0.25-0.50 of an inch in northern California and east of the Cascades.
Amounts may be slightly lower than 0.25 of an inch east of the Warner
Mountains. 24-hour temperature change from this afternoon to Monday
afternoon will be 20-30 degrees over the east side. Precipitation will
become more showery Monday behind the front and there is a slight risk
of thunderstorms in the cool, unstable air mass, but we're not
expecting significant amounts of lightning.

More wet weather is expected midweek as another wet front moves
onshore Tuesday into Wednesday. Cool, showery weather will likely
continue into Thursday before some drying occurs late next week with
temperatures getting back closer to normal. -Spilde

&&

Mfr watches/warnings/advisories...
or...red flag warning until 8 PM PDT this evening for orz624-625.
Wind Advisory until 8 PM PDT this evening for orz030-031.

California...red flag warning until 8 PM PDT this evening for caz285.
Wind Advisory until 8 PM PDT this evening for caz084-085.
Red flag warning until 8 PM PDT this evening for caz284.

Pacific coastal waters...gale watch from late Monday night through
Tuesday afternoon for pzz350-370.

National Weather Service Glossary of Abbreviations