or discuss
Office: MFR
FXUS66 KMFR 040534
AFDMFR
Area Forecast Discussion
National Weather Service Medford OR
934 PM PST Wed Dec 3 2025
...Updated AVIATION Discussion for 06Z TAFs...
&&
.AVIATION...04/06z TAFs...Mid to high level clouds are staying at
VFR levels so far tonight. Guidance suggests that IFR to LIFR
ceilings may develop in the Umpqua Valley, but fog is looking less
likely. Chances for fog remain in the Rogue Valley, but should be
short lived if it does manage to develop. A weak front will help to
clear out any development and bring generally VFR conditions across
the area. Late afternoon/early evening showers along the coast and
into Douglas County as well as along the Cascades may bring periods
of locally lower ceilings and visibilities to these areas. -TAD
&&
.PREV DISCUSSION... /Issued 207 PM PST Wed Dec 3 2025/
DISCUSSION...
Key Points:
* Overall, minimal weather impacts through early next week
* By far and large, mostly dry conditions expected through Fri
* Next widespread chance for precipitation is mainly Saturday
- Could be as early as Friday and lingering into Sunday
- Very high snow levels (6,000ft+)
- See note at end of discussion on Crater Lake snow
* Signs pointing towards active weather around Dec 9th-12th
- Heavy rain (west of Cascades) and heavy snow (Cascades)
* King Tides are this weekend, but not expecting impacts/hazards
Further Details:
A ridge of H5 high pressure continues over the Pacific allowing
northerly to northwesterly flow aloft to dominate the region. The
ridge will slowly flatten out by Friday which will allow for more of
a westerly flow pattern through the weekend. Overall, deterministic
and ensemble guidance continues to be in fairly good agreement with
the general pattern this week. We do start to see some minor
discrepancies tomorrow where some guidance brings in light QPF.
However, this may end up being clouds without QPF, but recent trends
have showed an increase in measurable precipitation. Regardless, the
impacts look to be minimal in any solution as precipitation would be
very light through tomorrow night. The much better and more
widespread chances starts Friday/Saturday and continues through
Sunday morning. The result will be rainfall for most areas as snow
levels are 6K+ feet. For perspective, several ensemble members (both
GFS and Euro) continue to show no snow accumulation for Crater Lake.
In typical fashion, coastal areas will see the highest 48hr QPF
amounts, but the Umpqua Basin (especially higher elevations around
Douglas County) and the Cascades will also be on this list of higher
QPF amounts. Crater Lake could end up with close to an inch of
rainfall over 48 hours given the high snow levels. At this time,
flooding anywhere is unlikely, and we are not seeing any notable
river rises with this system.
Looking ahead, cluster analysis for 500mb anomalies is still split
on a potential trough in the area Dec 10th-12th (as early as the
9th). This could lead to a slight risk of both heavy rainfall and
heavy snowfall, but given the split (trough vs ridge) there is a lot
of uncertainty. Additionally, this is pretty far out in the future,
and a lot could change, but we are watching this time period for
potential active weather. We will continue to monitor and refine the
details in the coming days. Snow pack is really low for this time of
year. The average (1991-2020) snow depth for today (Dec 3rd) at
Crater Lake is is normally 28.0", but we are sitting at zero. It
will likely take a few systems to get back to normal, but this
potential system next week would be a good start.
MARINE...Updated 200 PM PST Wednesday, December 3,
2025...Advisory level north winds will maintain steep seas south
of Cape Blanco through Thursday morning. Long period, swell
dominated seas will persist north of Cape Blanco. Winds swing
around to the west and southwest late Thursday into Friday, and
the resulting wind seas will combine with ongoing swell to produce
steep seas through Saturday. Gusty south winds and additional
steep seas may develop Saturday night into Sunday.
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.
CA...None.
PACIFIC COASTAL WATERS...Small Craft Advisory from 4 PM Thursday to 4
PM PST Saturday for PZZ350-370.
Small Craft Advisory until 4 PM PST Saturday for PZZ356-376.
&&
$$
Office: PQR
FXUS66 KPQR 040530
AFDPQR
Area Forecast Discussion
National Weather Service Portland OR
930 PM PST Wed Dec 3 2025
.SYNOPSIS...Today is the last dry day before a series of fronts
will bring a period of wet weather Thursday through at least
the middle of next week across southwest Washington and
northwest Oregon. Ensemble guidance suggests a potentially
impactful atmospheric river event next Monday into midweek,
though uncertainty is very high.
&&
.DISCUSSION...Wednesday afternoon through Tuesday...Today is the
last dry day in at least the next week before a series of
weather systems associated with Pacific moisture produce
multiple rounds of widespread rain over NW Oregon and SW
Washington. Although today remains dry, satellite imagery
indicates mid- to high-level clouds streaming over the region
Wednesday afternoon ahead of the first frontal system. These
clouds are keeping temperatures on the cooler side with 2 PM PST
temperature observations in the low to mid 40s across much of
the interior except for the 30s over the Cascades. Areas of
patchy fog and frost are possible for interior valleys once
again late tonight through early tomorrow morning before rain
begins spreading inland.
Upper level high pressure over the region and into the eastern
Pacific will become more zonal over the next couple of days as
the first weather system moves over the ridge. A warm front
associated with this weather system will approach the coast from
the northwest late tonight, then stall just off of the coast
through tomorrow. This will bring the first round of widespread
rain, beginning around midnight to 3AM along the northern coast
then quickly spreading inland through the early morning hours
with showers continuing through the night. Due to the northwest
orientation of winds, the Willamette Valley will likely be rain
shadowed and see lower rain accumulations. By Friday morning,
the cold front begins moving closer to the coast, pushing the
warm front inland. This cold front will bring a stronger surge
of moisture with IVT values peaking around 500-700 kg/m/s, and
round two of widespread heavier rain impacts the region through
Friday afternoon. The flow will be more westerly at this point,
allowing more precipitation to fall in the Willamette Valley.
The precipitation amounts through Saturday night are expected to
be around 0.4-0.6 inches for the central and southern Willamette
Valley, 0.6-1 inch from the Portland area north through the I-5
corridor, 0.9-2 inches along the coast and Coast Range, and
0.9-3 inches along the Cascades. Some elevated winds are likely
as the cold front passes through on Friday with a 20-40% chance
of wind gusts of at least 30 mph for inland valleys and a 50-75%
chance along the coast. There's a 20-50% chance of gusts of 40
mph or higher along the Cascades.
Guidance suggests the cold front might stall and weaken over the
PacNW into Saturday, with showers lingering through Saturday.
Then, another frontal system is slated to move through the area
on Sunday. Ensembles indicate IVT values could peak around
400-500 kg/m/s with this frontal system which would produce
another surge of widespread rainfall. A bit uncertainty exists
in rain amounts during this 48 hour period. Looking at the 25th
to 75th percentiles, the interior lowlands could receive
anywhere from 0.3-1 inch of rain, lowest amounts in the southern
Willamette Valley. The coast, Coast Range, and Cascades could
see anywhere from 0.5-2.5 inches, lowest in Lane and Lincoln
counties. Impacts are not expected with rain amounts Thursday
through Sunday, unless rain rates exceed 0.2-0.3 inches for
multiple hours over certain watersheds leading to rivers that
are prone to flooding quickly, such as the Grays at Rosburg and
Willapa River at Willapa. This will be something to monitor
during heaviest periods of rain.
The main period of concern for the forecast period is next week
as ensemble guidance continues to indicate the potential for an
impactful atmospheric river event Monday through Wednesday.
Significant uncertainty still remains in the length of elevated
IVT values, location of the moisture along the WA and OR coast,
and exact peak of IVT values (the 12z GEFS mean is around 550
kg/m/s with +1 standard deviation around 800 kg/m/s and the 12z
Euro EPS mean is around 700 kg/m/s with +1 standard deviation
around 900 kg/m/s). These factors have jumped around between
forecast runs over the past 24 hours and will likely continue to
fluctuate until we get closer to the event. There is the
potential that this ends up being another moderate atmospheric
river event, similar to the preceding events. If this is the
case, impacts are likely to be minimal once again. However, if a
strong to extreme atmospheric river event materializes, there
is the potential for widespread river flooding and/or wind
damage as soils will already be saturated and river levels
higher from the rain from the 4 days prior. The main period for
river flood concerns is Tuesday into Wednesday as it takes time
after rain begins for rivers to rise. HEFS guidance indicates a
10-25% chance of rivers reaching Minor flooding for Coast Range
and Coastal rivers and 5-20% chance for Willamette River
tributaries, mainly focused on Tuesday into Wednesday, possibly
beyond depending on the rain forecast and/or response times of
the rivers. Additionally, there are signals for breezy winds
with the frontal passage, although the ensemble spread remains
very wide leading to low certainty. If winds do end up even
around 30-40 mph, saturated soils could cause some localized
impacts due to downed trees. Keep an eye on this forecast,
especially if you live in flood prone regions. -03
&&
.AVIATION...Largely VFR flying conditions remain in place across
the region, with intermittent MVFR cigs at terminals along the
Lower Columbia and in the Portland area head of an approaching
frontal system. Abundant low-level moisture will favor
widespread MVFR cigs inland as rain begins by 12-15z Thu. Ahead
of the onset of rainfall, the southern Willamette Valley may see
enough clearing to yield areas of IFR vis/cigs within fog and
mist after 09-12z Thu, including at KEUG. As rain continues
through the morning, there are 50-60% chances for IFR cigs for
most inland terminals, however cigs look to lift into the
afternoon while chances for vis restrictions increase after
18-21z Thu. Calm to light and variable winds overnight will
increase out of the south to southeast at around 5 kt.
Along the coast, there is higher confidence in persistent VFR
conditions are expected overnight with light offshore flow,
before cigs trend downward to MVFR as rain begins by 09-12z
Thu along the southern WA and northern OR coast, and by 12-15z
along the central and southern OR coast. While MVFR conditions
are most likely after 12z Thu, there is a 10-20% chance of IFR
cigs Thursday afternoon as rain continues. Winds will turn out
of the south-southwest and increase to around 10 kt by 18z Thu.
KPDX AND APPROACHES...Mixed VFR/MVFR cigs expected ahead of
precipitation onset by 12z Thu with calm to light and variable
winds. 40-60% chance of IFR cigs through the early morning,
trending toward MVFR by Thursday afternoon with southerly to
southeasterly winds around 5 kt. -36
&&
.MARINE...High pressure over the waters today will maintain
northerly winds 10 kt or less through tonight. Seas around 6 to
7 ft continue to subside as well.
Active weather returns as winds turn southerly on Thursday ahead
of the first in a series of fronts. Chances for frequent wind gusts
greater than 21 kt remain below 15% on Thursday, with winds
turning more westerly behind the front. However, another slightly
stronger front moving through on Friday will bring a 50-70% chance
for wind gusts greater than 21 kt, with the highest chances north
of Cape Foulweather. Will likely need to issue a Small Craft
Advisory for Friday with the upcoming forecast package. The only
Small Craft Advisories in effect right now are for the Columbia
River Bar this afternoon and Thursday afternoon due to very strong
ebbs bringing seas in the Main Channel up to 9-10 ft.
A series of fronts continue through the weekend and into early
next week. There is a 50-60% chance for isolated gale force wind
gusts on Monday, but chances for frequent and widespread Gales are
only 15-30%. Seas remain around 6-8 ft at 11-12 seconds through
Friday, building on Saturday due to an increasing west-northwesterly
swell. There is a 60-80% chance of seas exceeding 10 feet by late
Friday night into Saturday morning. -10
&&
.BEACH HAZARDS...There is a Coastal Flood Advisory for minor
tidal overflow flooding during high tide from 9 AM to 3 PM
Thursday and Friday for the South Washington Coast and the Clatsop
County Coast in Oregon. Minor flooding up to 1 foot above ground
level is possible during high tide in low lying areas near bays,
sloughs, and the low reaches of the coastal rivers. Coastal
residents in the warned area should remain alert for rising water
and take appropriate action to protect life and property. Remain
out of the water to avoid hazardous swimming conditions. -10
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Coastal Flood Advisory from 9 AM to 3 PM PST Thursday for
ORZ101.
Coastal Flood Advisory from 9 AM to 3 PM PST Friday for ORZ101.
WA...Coastal Flood Advisory from 9 AM to 3 PM PST Thursday for
WAZ201.
Coastal Flood Advisory from 9 AM to 3 PM PST Friday for WAZ201.
PZ...Small Craft Advisory from 2 PM to 6 PM PST Thursday for PZZ210.
&&
$$
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Office: PDT
FXUS66 KPDT 040618
AFDPDT
Area Forecast Discussion
National Weather Service Pendleton OR
1018 PM PST Wed Dec 3 2025
.UPDATE AVIATION...06Z TAFs...Thanks to the low stratus layer,
this will drop KDLS/KPSC to MVFR with KYKM at IFR and KPDT/KALW to
LIFR conditions. KDLS/KPSC may briefly see patchy fog overnight
into early Thursday morning (35% confidence), but dense fog could
redevelop for KYKM/KALW while continuing for KPDT thus dropping
VSBYs to 1/2sm or less. The fog should then dissipate around 12Z
for KDLS/KPSC and later in the afternoon for KYKM/KALW. KPDT may
have lingering fog/mist through the day Thursday (40-50% confidence).
In addition to the fog and low cloud decks, a weak system will
begin approaching early Thursday morning with light rain starting
KDLS first before other sites. KRDM/KBDN will be VFR with light
rain Thursday morning until MVFR conditions return early Thursday
evening when low clouds redevelop. Winds will remain less than
10kts. Feaster/97
&&
.PREV DISCUSSION... /issued 229 PM PST Wed Dec 3 2025/
.DISCUSSION...Rest of Today through Thursday Morning: A weak
shortwave moving over the region has helped to lift fog impacting
areas of the Columbia Basin and adjacent valleys/foothills this
afternoon, though cloud decks remain fairly low across these
areas. This reprieve is expected to be brief, as there is mod-high
confidence (55-85%) that dense fog will redevelop in these areas
by this evening. That said, confidence is low(25-40%) in the
exact timing and areal extent of the fog redeveloping. Regardless,
opted to extend the current fog advisories through 12PM PST
tomorrow for the Kittitas/Yakima valleys and the Northern Blue
Mountain Foothills of OR/WA.
By Thursday morning, the first in a series of coupled shortwaves
and surface lows will arrive to the PacNW, while a plume of
moisture originating from the Hawaii region will aid precipitation
amounts with each incoming system. As for impacts Thursday
morning, dense fog is expected to persist across portions of the
Columbia Basin and adjacent foothills/valleys, with rain and
high mountain snow or rain/snow mix starting developing along the
Cascade Crest, then spreading southeast to the remainder of the
forecast area. One concern with incoming precipitation will be the
potential for freezing rain to develop tomorrow morning if the
cold pool strengthens and drops to or below freezing tonight.
Areas that would be most likely impacted would be portions of the
Kittitas/Yakima valleys, and along the northern Blue Mountain
foothills. That said, confidence is very low (<15%) in this
scenario playing out with onset of precipitation tomorrow.
Thursday Afternoon through Saturday: Ensemble guidance is in
great agreement through Saturday night that a persistent upper
level ridge in the northeast Pacific will force several surface
lows and attendant shortwave troughs to dive southeast across the
forecast area. While each system will be approaching from the
northwest, which would generally mean their airmasses would be
fairly cool/cold, a plume of tropical moisture with IVTs in the
150 to 250 kg/m/s range will ride up and over the ridge into the
PacNW, keeping the airmass generally saturated with well above
normal temperatures than normal this time of year (confidence
70-90%). As the airmass infiltrates the PacNW, snow levels will
slowly rise above pass level, keeping any snow or wintry mixes to
the higher mountain ridges and peaks through this period.
By Thursday afternoon, the first in the series of systems will
glide over the forecast area, resulting in widespread rain and
high mountain snow chances the remainder of Thursday. By Friday, a
more potent surface low with a strong cold front will approach the
PacNW, resulting in a tightening of pressure gradients at the
surface. Westerly winds will increase as early as Friday morning,
with winds forecast to peak Friday evening as the surface low and
cold front move across the forecast area. Wind gusts will
increase to 25-40mph across much of the area(confidence 60-80%),
with a 50-80% chance that wind gusts will exceed 45mph across
portions of the OR Columbia Basin, Blue Mountain Foothills, North
Central OR, Simcoe Highlands, as well as ridges in the WA Columbia
Basin to the WA Cascade east slopes. Winds will gradually decrease
through Saturday as the low departs the region to the east.
Otherwise, during this period, there is a 60-85% chance of the
Cascade crest and east slopes receiving 1.5 inches of QPF while
the northern Blues will only see a 30-55% chance. Looking at 0.5
inches of QPF, the northern Blue Mountain foothills and the
remainder of the eastern mountains will see a 35-70%. For the
remainder of the areas, there is generally a 20-60% chance for
0.25 inches of precipitation, with the lowest chances in the WA
Columbia Basin and across portions of central OR.
Sunday through Tuesday: Guidance continues to be in good
agreement Sunday through Tuesday as all but about 10-13% of
ensemble cluster members show the ridge axis moving inland and
flattening Sunday and Monday, with zonal flow developing over the
PacNW. Meanwhile, ensemble members of the GFS and ECMWF continue
to depict a 60-80% chance of at least a weak atmospheric river
(AR) with IVT of 150 kg/m/s filtering into the area. Under the
zonal flow, weak shortwaves with surface fronts will continue to
impact the forecast area through Tuesday, and with the
accompanying AR, this will result in periods of moderate to heavy
precipitation in the mountains with lighter amounts further down
along the Cascade east slopes and the northern Blue Mountain
foothills. Of the ensemble cluster members, the solutions made up
of the earlier mentioned 10-13% favor lower 500mb heights over
the PacNW, which would translate to lower snow levels and
potentially snow at or just above pass level in the mountains.
Otherwise, the remaining members favor mostly rain with high
mountain snow during this period. Lawhorn/82
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 28 43 37 53 / 0 80 70 90
ALW 31 42 37 49 / 10 80 80 90
PSC 28 42 32 51 / 10 70 50 60
YKM 27 42 31 52 / 10 40 40 70
HRI 29 43 36 53 / 0 80 60 70
ELN 27 43 31 46 / 20 50 50 80
RDM 25 47 35 55 / 0 50 40 60
LGD 26 40 35 48 / 0 90 90 100
GCD 26 42 37 49 / 0 80 90 90
DLS 36 48 42 56 / 10 70 70 90
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Dense Fog Advisory until 11 AM PST Thursday for ORZ507.
WA...Dense Fog Advisory until 11 AM PST Thursday for WAZ029.
Freezing Fog Advisory until 11 AM PST Thursday for WAZ026-027.
&&
$$
DISCUSSION...82
AVIATION...97
