Area Forecast Discussion
Issued by NWS Medford, OR
FXUS66 KMFR 260331
Area Forecast Discussion
National Weather Service Medford OR
831 PM PDT TUE OCT 25 2016
A warm front is located over western Siskiyou County and across
far southern Oregon this evening. This front is bring light rain
to areas over Southern Oregon and Siskiyou county. Rainfall
amounts have ranged from a hundreth of an inch to a third of an
inch over the last 3 hours. This front will lift north this
evening becoming located over Coos, Douglas, northern Klamath and
northern Lake counties by midnight...then it will shift north of
the area late tonight. However, a cold front will approach the
coast late tonight and Wednesday morning and send moisture and
rain into the coast with a chance for rain extending furtherinland
to the Cascades. This cold front will slowly move inland late
Wednesday through Thursday morning. Ahead of the front, the main
concern will be with strong gusty south winds, especially in the
Shasta Valley and east of the Cascades. The forecast remains on
track for winds and precipitation on Wednesday.
.AVIATION...26/00Z TAF cycle...An area of low pressure will bring
steady rain back to western Siskiyou County, the coast and the coast
ranges tonight. The initial VFR ceilings at the coast and just
inland will lower to MVFR tonight, with terrain becoming obscured
west of the Cascades and in Northern California. An area with
particularly low ceilings (IFR and LIFR) is the Mount Shasta area
where southerly flow typically brings poor conditions. Downslope
southeast winds should keep VFR at KMFR with just isolated to
scattered showers. Most east side locations should remain VFR
Additionally, increasing south winds over the area late tonight into
Wednesday will bring an increasing chance for turbulence.-SK
Note: The ceilometer at FAA site KOTH is out of service, so there
will be no ceiling observations available generally between the
hours of 04Z and 14Z.
.MARINE...Updated 245 PM PDT Tuesday, October 25, 2016...Approaching
low pressure from the southwest will bring another round of gales
and very steep seas late this evening through Wednesday afternoon.
Confidence is higher that gales will affect areas beyond 10NM from
shore and lower for areas within 10NM from shore. Winds and seas
gradually subside Wednesday night into Thursday and remain low
through Friday. The next front will arrive with increasing south
winds and steep seas Friday night into Saturday. SK
.PREV DISCUSSION... /Issued 449 PM PDT TUE OCT 25 2016/
Updated aviation discussion.
SHORT TERM...The PacNW will remain in a progressive pattern over
the next week and the weather will stay generally rainy. Though
there will be plenty of breaks between systems, timing is
**WINDS*** We are currently downstream of a longwave trough that
sent a shortwave over the area overnight. Some lingering light
showers will remain. A closed low will rotate around the base of
the trough...then move inside of 130W late tonight into tomorrow.
Most of the associated energy will remain offshore and to the
north of the Medford CWA...but still expect strong southerly winds
inland tonight and tomorrow, particularly over the ridges and in
the Shasta Valley...Scott Valley...and Summer Lake areas. A wind
advisory has been issued for tonight through tomorrow evening for
the Shasta Valley...Warners...Winter Rim...Summer Lake...and
Medicine Lake area. With the forecast pressure gradient from
Medford to Redding of 5mb, expect winds to remain below advisory
criteria in the Rogue Valley, but could have some gusts up to
30mph in the south end of the valley. A warm front associated with
the low will move over the CWA tonight...bringing steady rain to
the marine waters and coastal mountains. Also expect rain to form
over the Siskiyous, supported by upslope southeasterly winds.
Expect downsloping in the Rogue Valley to mostly prevent rain.
A weak system will move toward the area Thursday, bringing light
rain, with the heaviest amounts over the marine waters. Another wave
will approach Friday into Saturday. The last few model runs have
trended towards placing the bulk of the rainfall in the
southeastern portion of the CWA. Expect winds to stay well below
advisory criteria for both systems. -MSC
Long term...Saturday through Tuesday night.
The long term model solutions have a general consensus that the
pattern will be active and stormy with a series of low pressure
systems moving into the west coast. The trend was to adjust the
probability of precipitation higher and adjust temperatures lower.
In line with lower temperatures, snow levels were adjusted slightly
lower. These look to be normal to slightly warmer than normal fall
systems with snow levels in the ballpark of 5500 to 6500 Feet.
However, the model differences quickly grow beginning on Saturday
and have moderate to large differences in timing, track, and
strength of the individual systems. As a result, there is a broad
brush of mainly chance to likely PoPs with the highest probability
for Coos, Curry, Josephine, and Siskiyou Counties.
The long term looks to begin with a broad longwave upper trough
centered offshore from the Pacific Northwest. The ECMWF and GFS each
indicate a split flow with one closed low near Vancouver Island and
another of similar strength far offshore from far northern
California around 40N 135W. The GFS is showing its typical bias of
being more progressive than the ECMWF. It swings a cold front inland
on Saturday evening while the EC is nearly 12 hours slower. There
are differences in the extent to which our area is impacted by
either or both of the northern and southern branch of the trough.
The timing differences that grow with time lead to uncertainty in
whether our region will be in a stormy or post-frontal showers
environment in any of the individual day/night periods early next
OR...Wind Advisory from 11 PM this evening to 8 PM PDT Wednesday for
CA...Wind Advisory from 11 PM this evening to 8 PM PDT Wednesday for
Wind Advisory until 5 PM PDT Wednesday for CAZ081.
Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Wednesday for
Gale Warning from 5 AM to 2 PM PDT Wednesday for PZZ350-356.
Hazardous Seas Warning from 5 AM to 11 PM PDT Wednesday for
Gale Warning from 11 PM this evening to 2 PM PDT Wednesday for