FXUS66 KPQR 151652
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
952 AM PDT Wed Apr 15 2026

Updated aviation discussion and hazards. 

.UPDATE...Observations show the freezing level remains around 2500 ft. Mixed 
rain/snow showers are expected to continue through today down to 
1500 ft elevation, but these showers are unlikely to produce 
accumulating snow.


&&

.SYNOPSIS...The back edge of a cold frontal boundary which has 
spread ample precipitatiion and mountain snowfall across the 
Pacific Northwest quickly progresses through the region this 
morning followed by a showery airmass and a 15-30% chance for 
thunderstorms this afternoon. A Winter Storm Warning remains in 
effect for the Cascades through tonight. Concerns shift to 
cooler overnight temperatures and possible frost/freeze 
conditions to round out the week. After a brief stint of dry and
warmer weather Saturday, precipitation chances return by early 
next week although forecast confidence Sunday onward is low.

&&

.SHORT TERM...Now through Friday Night...
Now through Thursday Night...Early this morning
satellite and radar observations show our latest weather
disturbance in the form of a cold-frontal boundary and the wide
band of stratiform precipitation dropping NW to SE across 
western Oregon. Snow-levels are expected to quickly bottom out 
around 1500-2000ft in the cold airmass behind the frontal 
boundary by late morning with snowfall continuing to be the 
primary impact with this disturbance focused over the Cascades. 
We're still watching for a potential for 1-3 hr period of 
dynamic cooling artificially lowering snow levels closer to 
~1000ft around sunrise this morning, particularly in coast range
and southwest Washington southward through portions of 
Clackamas County. However, as far as travel is concerned, it'll 
be challenging to get accumulation on roadways at this elevation
should a period of wet snow or a rain/snow mix occur. The 
chances for a light slush-up gets higher once you reach 1500ft, 
particularly in the Cascade foothills/valleys, but due to the 
warm antecedent conditions most impacts remain 2000-2500ft+. 
The heavier precipitation early to mid morning helping to drive 
these lower snow levels will also help to boost snowfall rates 
at pass level, likely reaching 1-1.5+ in/hr until the frost 
passes. If you plan to traverse across the mountain passes 
today, please prepare for winter-like travel conditions.

Once we get into the midday and afternoon hours we'll have
transition to a more convective and showery post frontal 
environment thanks to the core of a upper level low moving
overhead. Most models still show Convective Available Potential
Energy (CAPE) values peaking around 200 to 500 j/kg this
afternoon leading to a 15-30% chance for thunderstorm 
development across the CWA. The main time period of focus is 
11AM to 7PM today when heating between shower bands is 
maximized. Convective Allowing Model (CAM) soundings are showing
a skinny CAPE profile and along with cooler temperatures aloft,
this does support tiny hail/graupel development with any 
thunderstorms that develop and given that when spring time 
thunderstorms develop within our CWA, they have a tendency to 
produce a lot of tiny pea size hail. Also be on the lookout for
infrequent lightning, gusty winds, and heavy rain associated
with any activity. With the loss of daytime heating 
thunderstorm chances decrease Wednesday night although showers 
likely persist.

At this point the axis of the upper-level low pulls to our east
with increasing heights on northerly flow aloft by sunrise
Thursday morning helping to decrease shower activity. The
lingering cooler temperatures aloft and partial clearing by
sunrise should allow overnight lows to drop below normal 
bottoming out in the mid 30s across the lowlands. Below 
freezing temperatures are even forecast for the higher coast 
range/Cascade valleys, including the Hood River Valley, and
potentially in the Cascade foothills mainly around and south of
OR-22. Give the moderate to high confidence in these low
temperatures panning out, have issued frost advisories for much
of the region including a Freeze Watch for the Upper Hood River
Valley and a couple of the aforementioned Oregon Cascade
foothill zones. A few showers likely lingering through Thursday,
increasing in the afternoon due to daytime heating, however, the
bulk of the activity will be pinned to terrain features in the 
Cascades and coast range. Similar frost/freeze conditions may 
develop again Thursday night into Friday morning and additional 
highlights may be needed for this period. Even though 
temperatures warm slightly aloft Thursday night compared to 
Wednesday night/Thursday morning, weak pressure gradients 
combined with a building ridge of high pressure aloft and better
clearing may prove to be a better set-up for frost development.

													-99/42


.LONG TERM...Friday through Tuesday...Looking towards the 
weekend confidence is high among both deterministic and 
ensemble guidance in a ridge of high pressure continuing to 
build aloft allowing temperatures to gradually warm and reduce 
frost concerns. However the pattern remains rather progressive 
as models show the ridge quickly followed by another low 
pressure system on Sunday originating from the Gulf of Alaska. 
WPC Cluster Guidance does favor this low dropping almost 
straight southward across the eastern Pacific favoring this low 
holding just off the OR/WA coast. How far this low holds off the
coast will heavily modulate conditions locally. Should it stay 
more to our west, warmer conditions and broad southerly flow 
would be favored, That said, any moisture riding south to north 
within this flow pattern could spell the return of convection. 
Thus forecast confidence Sunday onward into the middle of next 
week is low. -99/42


&&

.AVIATION...Post frontal showers are expected to persist through
the day with increasing chances for convection in the afternoon
after 20Z Wed. Highest probabilities lie along the Cascade
foothills and to the north with around a 25-35% chance inland 
within the Willamette Valley. Thunder is challenging here as often
it may be one storm that pops up, while other times it can be a 
wide swath. In this case, because the flow is northwesterly (not 
as favorable) behind the previous system, would trend towards a 
more isolated thunderstorm scenario. Overnight, showers will 
slowly dissipate and clear. Dropping temperatures mean that there 
is a slight chance for frost formation over exposed surfaces. 


KPDX AND APPROACHES...Combination of MVFR and VFR conditions with
showers. Around a 30% chance of thunderstorms between 20Z Wed
through 06Z Thu. Thunderstorms will trend towards an isolated
scenario. Frost potential overnight if skies remain clear. -27

&&

.MARINE...
A cold frontal boundary is quickly progressing across
the coastal waters early this morning with winds switching 
northwesterly in its wake. Expect gusts between 20-30 knots the
remainder of the day as an area of low pressure drops along the 
Canadian coast toward the region. This feature will also bring a 
15-25% chance of thunderstorms over the waters into the evening
hours. Seas are expected to persist at around around 9 to 10 ft, 
building slightly to around 10 to 12 ft tonight as a fresh northwest
swell moves through the waters. The Small Craft Advisory remains 
in place through Thursday morning for both the inner and outer
waters, including the Columbia River Bar. High pressure then 
builds over the waters Thursday into the weekend as northerly 
winds return and seas gradually subside to around 3 to 6 ft Friday
into Saturday. It appears there's a 40-60% chance for north winds
to gust above 21 knots into Small Craft Criteria on Saturday.
Looking ahead there is potential for another weather system to 
impact the waters later this weekend, possibly increasing winds 
and seas.  -99/DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Frost Advisory from 1 AM to 9 AM PDT Thursday for ORZ104>107-
     109-114>118-123.
     Freeze Warning from 1 AM to 9 AM PDT Thursday for ORZ121.
     Freeze Watch from late tonight through Thursday morning for 
     ORZ124-125.
     Winter Storm Warning until 5 AM PDT Thursday for ORZ126>128.
WA...Frost Advisory from 1 AM to 9 AM PDT Thursday for WAZ204-205-
     208.
     Winter Storm Warning until 5 AM PDT Thursday for WAZ211.
PZ...Small Craft Advisory until 5 AM PDT Thursday for PZZ210.
     Small Craft Advisory until 11 AM PDT Thursday for PZZ251>253-
     271>273.
--------------------------------------------------------------------

FXUS66 KMFR 151101
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
401 AM PDT Wed Apr 15 2026

.DISCUSSION...Precipitation ahead of an approaching cold front is 
falling across areas west of and along the Cascades, with a few 
stray showers getting farther east. Tripcheck webcams are showing 
snowfall around Diamond Lake as well as along parts of Highway 97 
early this morning.

The most active period for this front looks to be through this 
morning and afternoon. Coastal areas may see periods of moderate to 
heavy rainfall, with moderate rainfall also possible into the Umpqua 
and Illinois valleys. Impactful snowfall over the Cascades is also 
expected to continue in this timeframe, with SPC guidance keeping 80-
90% chances for snowfall rates to reach 1 inch per hour over peaks 
and ridgelines and 60-80% chances for neighboring areas. 

Snowfall over the Cascades continues into the afternoon, but at 
decreasing rates. Rainfall will reach the Rogue and Applegate 
valleys in this timeframe. Gusty winds look to develop over broad 
areas east of the Cascades as well. Precipitation and winds ease 
into the evening and night. Snow levels drop to 2500 feet late 
tonight and could reach 1500 feet by Thursday morning. At this 
point, only scattered post-frontal showers are expected and 
widespread winter impacts are not a concern. 

The cold air mass behind the front looks to bring cool overnight 
lows from tonight into Thursday morning and again from Thursday 
night into Friday morning. A Frost Advisory will be in place for the 
Rogue, Applegate, and Illinois valleys for tonight into Thursday, as 
lingering cloud cover looks to keep temperatures just above freezing 
concerns. Localized freezing conditions may be possible in some 
areas, notably in the southern Illinois Valley. A Freeze Watch 
covers the Thursday night-Friday morning timeframe, as there's some 
question how cold that night will get.

A number of hazard products are in place to further communicate the 
impacts of this active period. A Winter Weather Advisory for the 
Cascades from Crater Lake northward and above 4000 feet remains in 
place through Thursday morning. A Wind Advisory for most of Lake 
County as well as the Warner Mountains and areas north of Alturas in 
Modoc County highlights dangerous travel conditions in these areas.

An upper ridge will bring drier conditions and warmer daytime highs 
on Friday and Saturday. Long-term guidance shows a low pressure 
system approaching from the northwest. Details for this system 
remain coarse, with some variations between the ECMWF and GFS 
outcomes. This system may bring a southerly flow pattern that tends 
to focus precipitation at Curry County as well as parts of western 
Siskiyou County, per ECMWF imagery. Or it might bounce off a ridge 
and linger over the Pacific before moving inland on Monday, per GFS 
imagery. Initial snow levels are in the 5000-7000 foot range, which 
would limit winter impacts. Showers may continue beyond Monday, 
depending on how this system behaves. -TAD


&&

.AVIATION (06Z TAFs)...

A front will move across the area tonight and Wednesday. This will 
result in widespread precipitation through Wednesday afternoon. As a 
result, expect widespread MVFR conditions to develop. Areas of IFR 
ceilings and visibilities are expected along the coast late tonight 
and early Wednesday morning. Probabilities were not high enough to 
include IFR (ceilings/visibilities) for inland sites at this time, 
but there is an 8%-18% chance for IFR conditions inland. Widespread 
mountain obscurations are expected tonight through Wednesday. 
Conditions will gradually improve becoming a mix of MVFR and VFR 
late Wednesday afternoon and evening.  

&&

.MARINE...Updated 200 AM PDT Wednesday, April 15, 2026...A front will
bring rain, strong winds, and steep seas today. Localized areas of 
very steep and hazardous seas are possible north of Coos Bay today 
into Thursday morning. Conditions improve late Thursday, but a weak 
thermal trough may bring gusty northerly winds to the waters south 
of Cape Blanco late Thursday into Friday. Another active system may 
bring additional rainfall and steep seas this weekend. 

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Freeze Watch from late Thursday night through Friday morning for 
     ORZ024. 

     Wind Advisory from 11 AM this morning to 8 PM PDT this evening 
     for ORZ030-031. 

     Winter Weather Advisory until 5 AM PDT Thursday for ORZ027. 

CA...Freeze Watch from late Thursday night through Friday morning for 
     CAZ080. 

     Wind Advisory from 11 AM this morning to 8 PM PDT this evening 
     for CAZ085. 

PACIFIC COASTAL WATERS...Small Craft Advisory until 5 PM PDT Thursday 
     for PZZ350-356-370-376. 

--------------------------------------------------------------------

FXUS66 KPDT 151147
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
447 AM PDT Wed Apr 15 2026

.KEY MESSAGES...
- Mountain snow will persist through Thursday morning 

- Breezy conditions in the lower elevations through Thursday

- Near to below freezing morning lows Thursday and Friday for
  the lower elevations

&&

.DISCUSSION...Today through Thursday: Satellite and regional 
radar imagery show a cold front slowly pushing southeast across 
the PacNW this early morning, with snow showers along the 
Cascade crest and across the Blue mountains.

The cold front has mostly stalled along the Cascade crest this
morning, which has resulted in moderate snow showers impacting
the Cascade passes. The cold front is expected to pass over the
Cascade crest later this morning and continue to push southeast
across the forecast area through this evening, while a closed
low is expected to arrive to the region by this afternoon. The 
best chances for precipitation in the lower elevations will be 
associated with the frontal passage today, with many locations 
only seeing rain throughout the day. However, snow levels
plummeting to around 2kft behind the frontal boundary and 
anticipated post-frontal showers will bring chances (30-40%) of
light snow to portions of central OR this evening. By tonight,
the upper low will move over the forecast area, cutting off
precip chances in the lower elevations.

AS for the mountains, moderate to locally heavy snow showers 
will continue to develop across the Cascade crest and the 
northern Blues through this evening, with snow tapering off 
late tonight into Thursday morning. Multiple winter weather 
headlines are in effect today through tonight and early Thursday
morning in anticipation of impacts from the heavy mountain 
snow. There remains high confidence (85-90%) in snow 
accumulations totaling between 6-12 inches for the OR Cascade 
east slopes above 4000 feet, 4-8 inches for the upper east 
slopes of the WA Cascade east slopes, and 5-10 inches for the 
Northern Blues above 4500 feet. The heaviest snow accumulations 
are expected to occur with the cold front passage this morning, 
becoming light to locally moderate through the remainder of 
today.

Breezy winds will continue to impact the region through Thursday 
as the cold front passage and continued cold air advection into 
the forecast area result in tightened pressure gradients. 
Confidence is moderate-high (60-85%) that westerly winds will 
remain between 15-30mph and gusts 25-45mph. That said, wind-prone
areas in the Columbia Basin and Blue mountain foothills will 
see a 65-85% chance of gusts exceeding 45 mph today as the cold
front boundary moves through the region. Otherwise, clearing 
skies, dry surface conditions, and cold air advection into the 
region will result in near to below freezing morning 
temperatures Thursday and Friday. Of particular concern are the 
Kittitas and Yakima valleys, where there is 80-90% chance of 
morning lows below freezing both days; the northern Blue
mountain foothills of OR are also a concern where there is a
60-80% chance of below freezing lows, especially in areas prone
to cold-pooling. Freeze warnings have been issued in these areas
for Thursday morning, and will likely need to be reissued for
Friday morning.

Friday through Tuesday: Ensemble guidance is in good agreement 
of upper level ridging sliding across the PacNW with dry 
conditions and light winds by Friday (confidence 75-90%). The 
forecast area will remain under the influence of the ridge 
through Saturday, but ensemble members disagree on the 
evolution of the synoptic pattern Sunday into early next week. 
That said, there is good agreement in some form of upper low 
bringing another round of precipitation chances across the
PacNW, but confidence is low (15-25%) in timing, intensity, and
p-type. Lawhorn/82

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...VFR conditions to
prevail through the period. A cold front moving through the
region will bring rain shower impacts to all sites this morning,
with associated showers diminishing around 18Z. Post frontal
rain showers may impact sites DLS/PSC between 22-03Z, while
showers may start off as a mix and transition to snow at sites
RDM/BDN between 01-04Z. Winds will increase to 12-20kts with
gusts 20-35kts at all sites this morning, with these winds
prevailing at sites PDT/ALW late into the evening. Winds will 
shift to the west/northwest behind the frontal passage this 
morning and early afternoon. Winds will become light, 12kts or 
less, at sites DLS/RDM/BDN/YKM/PSC around or after 03Z.
Lawhorn/82

&&

.Preliminary Point Temps/PoPs...
PDT  51  31  54  33 /  90  40  10   0 
ALW  51  34  54  35 / 100  60  30   0 
PSC  58  34  61  34 /  70  20   0   0 
YKM  55  30  59  30 /  30  10   0   0 
HRI  56  33  59  34 /  70  20   0   0 
ELN  47  29  51  30 /  20  10   0   0 
RDM  49  22  49  22 /  90  30   0   0 
LGD  49  29  46  30 /  90  60  50  10 
GCD  50  26  45  25 / 100  70  50  10 
DLS  53  35  57  36 /  80  20   0   0 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 11 PM PDT this evening for 
     WAZ030-522.
     Freeze Warning from 11 PM this evening to 9 AM PDT Thursday 
     for WAZ026-027.
OR...Winter Weather Advisory until 11 PM PDT this evening for 
     ORZ502.
     Freeze Warning from 11 PM this evening to 9 AM PDT Thursday 
     for ORZ507.
     Winter Storm Warning until 5 AM PDT Thursday for ORZ509.

--------------------------------------------------------------------

FXUS65 KBOI 151156
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
556 AM MDT Wed Apr 15 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Rain, mountain snow and gusty winds on Wednesday, then snow
  level lowering to valley floors tonight and Thursday morning.

- Subfreezing morning temperatures Friday and Saturday in the
  agricultural areas.

- Warmer and drier over the weekend, with another chance of 
  precipitation early next week.

&&

.SHORT TERM /Through Friday Night/...
Issued 322 AM MDT WED APR 15 2026
The next strong upper trough from the Gulf of Alaska and 
surface cold front were approaching our area this morning 
with another round of moderate to heavy rain and snow today
and tonight. At 2 AM MDT the eastward-moving cold front was 
already onshore in western WA and OR, extending out into the 
Pacific along 42N. The supporting upper low was near 50/130
near the BC coast and moving southeastward. Radar was already 
showing areas of light rain and snow in eastern OR and western-
most Idaho but little was reaching the ground. But pcpn will 
increase around sunrise and continue through the day and this 
evening. This system is colder than the previous one and will 
lower the snow level to valley floors late tonight and early 
Thursday morning, but by then most of the pcpn will be ending. 
The surface cold front is slated to pass through eastern OR 
this afternoon and western Idaho this evening. Ahead of the 
front, heaviest pcpn will fall in the Boise Mountains and west 
Central Idaho Mountains with snow level near 6000 feet, with 
rain heavy enough to loosen rocks and mud on steep slopes, so 
travelers should avoid the Banks-Lowman road and similar roads
until rain changes to snow this evening. Total pcpn today 
through Thursday should be 0.75 to 1.25 inch in our northern
mountains, and generally 0.25 to 0.75 inch elsewhere, except 
0.15 to 0.25 inch in rain-shadowed southern areas. Total 
snowfall will be 8 to 15 inches above 6000 feet late today 
through tonight but only 1-3 inches near 5000 feet, including 
McCall/ID. Pre-frontal southwest to west winds will increase to
advisory speeds in the southwest Idaho Highlands, southern Twin
Falls County, and in southern Malheur and Harney Counties. A 
Wind Advisory has been posted for those areas this afternoon and
early evening. The frontal passage itself will be marked by a 
short period of heavy showers and isolated thunderstorms. After 
that the snow level will lower rapidly and rain will change to 
snow, with up to an inch accumulation overnight in the Magic 
Valley but little or none in the Treasure Valley. 

Thursday will be windy and cold with lingering snow showers as 
the upper low moves through, then clearing and quite cold 
Thursday night. A Freeze Watch has been posted for the Treasure
Valley and western Magic Valley agricultural valleys for Friday
morning and again Saturday morning, but Friday looks like the 
colder day. Low temperatures Friday will dip as low as 24 
degrees in the western Magic Valley which would be a hard 
freeze, with 27 to 30 degrees in the Treasure Valley, again 
cold enough to damage young plants unless they are protected.

&&

.LONG TERM /Saturday through Wednesday/...
Issued 322 AM MDT WED APR 15 2026
A ridge building in behind the system in the short-term period 
will allow for dry and milder conditions on Saturday, with 
temperatures near normal. Saturday morning will be the last 
morning (in this forecast period at least) with temperatures
near or below freezing across the area. Temperatures come 
Sunday will warm to 5-10 degrees above normal. 

This next week, guidance continues to resolve a low digging down 
from the Gulf Alaska and closing off from the main jet stream, 
but timing continues to be tricky. Over the past few runs, 
ensemble guidance has continually slowed the system, delaying 
its arrival into our area. With southerly flow ahead of this 
low, a slight warming trend would be able to sustain itself into
early next week with a slower arrival. The current forecast 
carries slight precipitation chances come Monday, increasing to 
20-40 percent area-wide Tuesday and Wednesday (where the 
consensus is starting to lean on the low's arrival). Temperatures
should be able to maintain the slight warming trend and remain 
above normal through Tuesday in the southerly flow, before 
cooling to near normal behind the system. Breezy south/southwest
winds are anticipated early next week as the low inches closer,
becoming W-NW following its passage.

&&

.AVIATION /12Z Wednesday through Thursday/...
Issued 556 AM MDT WED APR 15 2026

Precip expanding from NW to SE through the day. low VFR/MVFR
ceilings in rain, IFR/LIFR in mtn snow. Snow levels 5-7kft MSL.
A cold front will bring sharp wind shifts and intensify precip,
MVFR/IFR in heavier rain showers. A 25% chance of thunder along
the front. Snow levels rapidly lowering to valley floors
following the front. Precip becoming scattered early Thu/AM. 
Surface winds: becoming SE-SW 10-20 kt with gusts to 20-35 kt. 
Then W-NW 15-30kt with gusts up to 45 kt Wed/PM with the 
frontal passage. Winds aloft at 10kft MSL: W-SW 25-40 kt. 


KBOI...Ceilings lowering to MVFR this morning with increasing
showers. Periods of VFR early this afternoon. A strong cold
front will arrive around Wed/23z-Thu/00z. The front will bring 
a sharp wind shift, heavier precip, temporary MVFR/IFR, and 
potential for graupel/lightning. Conditions returning to VFR 
following the front. Surface winds: Becoming SE 10-15 kt this 
morning. Then NW 15-25 kt with gusts to 25-35 kt behind the 
front. 


&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Freeze Watch from late Thursday night through Friday morning 
     for IDZ012-014-016.
     Wind Advisory from noon today to 8 PM MDT this evening for 
     IDZ015-030.
OR...Freeze Watch from late Thursday night through Friday morning 
     for ORZ064.
     Wind Advisory from noon MDT /11 AM PDT/ today to 8 PM MDT /7 
     PM PDT/ this evening for ORZ061-063.
--------------------------------------------------------------------

FXUS66 KSEW 151056
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
356 AM PDT Wed Apr 15 2026

.SYNOPSIS...
A cold front continues to shift eastward today, with steady snow
coming to an end in the Cascades. However, expect widespread
showers Wednesday across the area in the cool, unstable post-
frontal air mass. A few isolated thunderstorms are possible this
afternoon. Drier but cool conditions then develop later this
week until the next frontal system approaches the region
offshore this weekend.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...
A cold front passed through western Washington yesterday 
evening/this morning. This is being driven by an upper level 
low/trough that will dig southward today across the state. The radar 
remains active this morning with precipitation continuing in the 
lowlands and Cascades this morning. A convergence zone is keeping 
showers going between Seattle and Everett. Snow has been falling at 
all of the Cascade passes, and the surface temperatures up there 
have been just below freezing. The winter storm warning will 
continue through 11 PM this evening, with a couple additional rounds 
of snow expected through the day today. A couple of the snow-bands 
later may be able to produce heavier snow rates.

For the remainder of the area today, the cold air aloft with the 
trough sinking over will create an unstable airmass for a chance of 
convection today. SPC has the coastal areas in a general risk of 
thunder today, although the thunder risk will encompass the entire 
coverage area today. The risk is capped at 30% (with the coastline 
and interior/Puget Sound areas having the best chance of seeing 
thunder). These showers/thunderstorms are expected to be scattered 
in nature, with any breaks of sun during the morning able to add to 
the 200-300 J/kg of CAPE in place. The window for thunder will be 
from late morning through early evening. The main concerns are 
lightning, and downpours containing heavy rain and graupel/small 
hail. No organized severe weather is expected. Highs today remain 
cool - upper 40s to low 50s in the lowlands, and 30s/40s in the 
mountains. Winds will remain light out of the west 5-10 mph.

The trough moves out going into Thursday. North flow behind the 
trough will bring in cooler Canadian air into the region. Conditions 
will be dry going into Thursday/Friday. Main concern will be the 
potential for any fog/frost/freeze conditions next couple mornings 
to finish the week. Mitigating factors will be the potential for 
some cloud coverage overnight, boundary layer conditions and the wet 
grounds from recent rains may favor some patchy fog development in 
spots. Light to calm winds and any clearing that does take place 
will allow temperatures to fall into the low 30s and upper 20s 
Thursday and Friday morning. Probabilities for a hard freeze are 
greatest in the Chehalis Valley/South Interior areas, with remaining 
lowland areas more likely to see frost at this point. If 
frost/freeze conditions do form, it will be important to protect any 
plants/crops outside susceptible to the cold conditions.

HPR

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Ensemble guidance continues to bring the next low pressure
system south from the Gulf of Alaska offshore past the region
this weekend. There remains a significant spread in the 
eastward extent of the associated front across the region, which
would impact the potential for additional rainfall this weekend.
While there remains some mention across most of the area, the
chances remain highest across the Olympic Peninsula and
coastline. Regardless, this looks to be a weaker system than
the currently passing front and a more seasonable air mass with
lowland temperatures returning to the 60s and snow levels
returning back above the Cascade passes.

12

&&

.AVIATION...
A cold front moved through the terminals this morning, with a post-
front convergence zone producing additional showers in Puget Sound. 
The showers were rotating around an anti-cyclonic meso-low, with 
some outflow turning the winds northeasterly at KSEA and KBFI this 
morning. The convergence zone is expected to last through 16-18Z, 
with winds turning back to the southwest 4-8 kt. Ceilings this 
morning have ranged between MVFR/VFR, but will trend towards VFR 
through the day. A trough will dig southward today, with north flow 
increasing late tonight/Thursday aloft. Breaks in the clouds with 
sun today will help destabilize the atmosphere for convection during 
the day. There is a 20-30% chance of thunder in the terminals this 
afternoon (most likely window is from 20Z-00Z this afternoon denoted 
with PROB30). Cloud tops on any storms are likely to remain under 
20,000 ft. Coverage will be scattered in nature. Main concerns are 
lightning, heavy downpours that may contain graupel/small hail, and 
gusty/variable outflow winds. Conditions will dry going into 
Thursday with an increased likelihood of MVFR ceilings Thursday 
morning. Winds become light out of the northwest tonight/Thursday 
less than 5 kt.

KSEA...Vicinity showers with a convergence zone to continue through 
late this morning. Brief NE winds with this feature will switch to 
the SW 4-8 kt around 16-18Z (few gusts up to 20 kt before the 
switch). MVFR ceilings improving to VFR this morning, with MVFR 
likely Thursday morning. Showers to continue through the day and a 
30% chance of thunder (most likely window is from 21Z-00Z). Drier 
conditions into Thursday morning. Lightning, graupel/downpours, and 
variable breezy winds are possible with storms in/near the terminal. 
Winds to become light under 5 kt later this evening (brief variable 
period possible from 22Z-02Z).

HPR

&&

.MARINE...
Winds have peaked over the waters this morning in the wake of
the passing cold front. Widespread showers can be expected
through the day with a few stronger ones potentially bringing
lightning and stronger wind gusts. Meanwhile, seas remain 7 to
12 ft over the coastal waters as they increase today. Even if
short of 10 ft, conditions will be rather steep with a dominant
period around 8 seconds over the coastal waters.

Conditions begin to subside later in the week with weak high
pressure building over the waters Thursday through Saturday. The
next front will approach the waters over the weekend bringing
another round of gusty winds and building seas over the waters
into the weekend.

12

&&

.HYDROLOGY...
No river flooding is expected during the next seven days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Storm Warning until 11 PM PDT this evening for Cascades 
     of Pierce and Lewis Counties-Cascades of Snohomish and 
     Northern King Counties-Cascades of Southern King County-
     Cascades of Whatcom and Skagit Counties.

PZ...Small Craft Advisory until 10 AM PDT this morning for Grays 
     Harbor Bar.

     Small Craft Advisory until 5 AM PDT Thursday for Coastal 
     Waters From Cape Flattery To James Island 10 To 60 Nm-
     Coastal Waters From Cape Flattery To James Island Out 10 
     Nm-Coastal Waters From James Island To Point Grenville 10 
     To 60 Nm-Coastal Waters From James Island To Point 
     Grenville Out 10 Nm-Coastal Waters From Point Grenville 
     To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point 
     Grenville To Cape Shoalwater Out 10 Nm.

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