Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/29/20
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
601 PM EST Tue Jan 28 2020
.AVIATION...
Weak subsidence overnight will result in a subtle lowering of the
inversion. This along with slight boundary layer cooling will
support some degree of lowering clouds overnight. Rap soundings with
the support of recent trends across the thumb suggest ceilings at
PTK/FNT/MBS may drop just below 2k feet overnight. The weak gradient
will generally keep sfc winds at or below 6 knots as they veer from
the NNW to the NE tonight.
For DTW...A little bit of divergent low level flow and late
afternoon diurnal heating as lifted some of the cloud bases just
above 3k feet. Nocturnal boundary layer cooling this evening should
support a more sustained MVFR based ceiling. The probabilities for
cigs to drop below 2k feet are lower within the lower elevation at
metro in comparison to PTK and locals to the north.
DTW THRESHOLD PROBABILITIES...
* High for ceiling at or below 5000 ft tonight and Wednesday.
&&
.PREV DISCUSSION...
Issued at 415 PM EST Tue Jan 28 2020
DISCUSSION...
Persistent low-level cloudiness will continue into the evening and
overnight hours as a stubborn inversion intersecting the 800 mb
level shows no signs of breaking down. This is largely due to the
lack of a mechanism facilitating thermal modification as the 850-700
mb layer mean temperature advection rates are locked within a narrow
range from about -1.5 to 2.0 C/12hr over the next couple days
allowing 850 mb temperatures to hover near -8 C at bottom of the
inversion layer. As noted in previous discussions, moisture content
will remain elevated beneath this layer supporting the possibility
for light flurries with maybe some drizzle mixing in. The main
forcing to support this is tied to a relatively low amplitude mid-
level shortwave trough being nudged onshore north of Grand Rapids
ahead of the inbound ridge. Weak vorticity with this wave that is
already apparent in GOES-E visible imagery warrants the inclusion of
low-end PoPs for this evening and early tonight. Weak dBZ returns
are noted on both KDTX and TDTW radars over the southwestern
counties, but there are currently no obs to suggest any precip is
reaching the ground at this time. This isn`t too surprising given
dewpoint depressions have risen to between 7 F and 10 F at the
surface. Even once saturation extends down to the surface, no
measurable accumulation will occur due to low precip rates given the
lighter nature. Temperatures spread will be a smidge larger tonight
as afternoon highs in the mid 30s should fall into the mid-upper 20s
overnight.
By Wednesday morning, the upper level ridge axis will be in place
over the Great Lakes. Weak winds will veer easterly by daybreak as
Canadian high pressure drifts south a bit. Subsidence is fairly week
as 18Z forecast soundings on Wednesday show limited variation from
18Z today except a slight decrease in column moisture as PWATs will
drop below 0.20 inches during the afternoon. Sub-inversion stratus
also continues, but conditions will be less favorable for drizzle or
flurries given the lack of dynamic support. As it stands with this
update, a dry forecast will be carried from Wednesday into Thursday
night with highs in the low-mid 30s and overnight lows in the low-
mid 20s.
More active pattern is more likely this weekend, although medium-
range guidance is not fully in-sync yet. Friday should be fairly
dry, but slight chance PoPs are included owing to the arrival of
several shortwaves with some evidence of upper level cyclonic
circulations. Main precip will arrive as a longwave feature
intersects with a southern stream jet over the Mississippi. Current
analysis points to snow showers on Saturday and Sunday on the north
side of the surface low that tracks through the Ohio Valley. High
degree of uncertainty remains with this setup. Warmer southwest flow
arrives behind the wave allowing for temps to rise into the 40s or
perhaps 50F along the MI/OH border by Monday.
MARINE...
Light northwest flow of 10 to 15 knots this afternoon will veer to
the northeast tonight and continue through the day on Wednesday as
high pressure drops south from James Bay. Even with the onshore
flow, waves should remain below 4 feet.
Light and variable winds on Thursday will become light southwest on
Friday as a weak cold front passes through on Saturday. Stronger
southwest winds (20+ knots) appear possible early next week.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....SC
DISCUSSION...KK
MARINE.......SF
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
951 PM CST Tue Jan 28 2020
.UPDATE...
Issued at 948 PM CST Tue Jan 28 2020
Updated the dense fog advisory to begin earlier tonight as we have
sites that have hit 1/2SM to 3/4SM already, with this occurring
more often and decreasing with time. Opted not to expand the
advisory east as GLAMP trending not as foggy in our east and SREF
and HRRR indicate that we will not fog up as much there as well.
With cloudy conditions, I went closer to CONSRAW and raised our
low temperatures to the upper 20s for Wednesday morning.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 155 PM CST Tue Jan 28 2020
Aloft: Progressive fairly low-amplitude flow conts over the CONUS
per aircraft wind obs and RAP tropopause analyses. They depicted
a narrow shrtwv trof from SA all the way down to TX. A shrtwv
ridge was over the Rckys...with the next trof along the W coast.
The trof currently over the Plns will cont moving E and cross the
CWA this eve. The Rckys ridge will diminish in amplitude and move
thru tomorrow. The trof along the W coast will be discussed below.
Surface: 1026 mb high pres was over ON and extended down to IA. A
sfc trof coincided with the mid-upr lvl trof. This trof will cross
the CWA this eve as well and then dissipate tomorrow. The ON high
will strengthen a bit and slide into QB...but still extend SW to
IA. The pres grad over NEB/KS will be very weak thru tomorrow.
Rest of this afternoon: Patchy -SN has been falling with VSBYs
mostly between 1 and 3 miles. The back edge of this snow will
gradually progress E...bringing the snow to an end W of Hwy 183.
The leading edge of the snow will also progress E with -SN moving
into the Hwy 81 corridor.
The snow is light and melting on contact with roads. With temps
hovering right around frzg...there will be little or no accum.
Skies are sunny immediately W of the upr trof. Clds will begin
breaking up W of Hwy 183.
Tonight: Patchy -SN will linger into the eve along and E of Hwy
281. Again...with little or no accum.
Believe we will have a fog problem on our hands tonight. Low
stratus will not be scoured out of the entire CWA. This low cld
cover and the precip has kept dwpt depressions very small today.
Winds will be very light or even calm tonight. As temps begin
falling after sunset...this is a recipe for stratus CIGs to
descend (where stratus remains) or dense fog to form where clds
temporarily decrease.
Have issued a Dense Fog Advisory for the W 2/3 of the CWA (along
and W of Hwy 281). It may take some time for CIGs to lower...but
believe this will need to be expanded to encompass the entire CWA.
We`ll let the next couple shifts monitor the trends. Regardless...
have strongly worded the fcst to indicate this potential.
Kept fcst lows on the higher side of the guidance envelope...but
did not go as high as I desired to remain in collaboration
thresholds with neighboring offices.
Wed: Foggy thru late morning...and while we will see gradual
improvement thereafter...it could linger well into the day from
the Tri-Cities N and E. Most the CWA will remain cldy...but the
stratus and fog should erode from the edges. Since it will be
sunny over Wrn NEB/KS...that means the best chance for sunshine
developing will be S and W of the Tri-Cities.
The clds will keep temps from warming much where there is no
sunshine. Wrn and Srn counties should at least get to 40F and
possibly into the low 40s.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 155 PM CST Tue Jan 28 2020
Aloft: The flow will become a bit more amplified thru early next
wk...but still remain progressive. The trof currently along the W
coast will split and the Nrn piece will cross NEB/KS Thu. The
passage of this trof will shift the flow to NW Fri. Significant
heights will occur heading into the wknd as a broad ridge builds
over the Wrn USA but conts moving E. NW winds over NEB/KS will
become W Sun as the ridge crests overhead. Winds will then become
SW Mon as the next fairly substantial Pac trof moves onshore and
approaches the rgn. This trof is fcst to cross the Plns Tue with a
positive tilt.
The last 2 runs of global mdls (GFS-FV3/EC/CMC/UKMET) are
generally in good agreement/tightly clustered. That said...there
are a couple runs that indicate the possibility of a closed low at
the base of the trof over KS Mon or Tue. That potential will need
to be monitored.
Surface: A sfc trof will move thru Thu in concert with its upr-
lvl reflection. Another sfc trof will slide thru Fri associated
with low pres heading E thru Srn Canada. Deep low pres will move
into SW Canada Sat and this will induce warm frontogenesis down
the entire lee of the Rckys...and downslope winds strengthen in
its warm sector. The strength of this low will increase temp
extremes both ahead of and behind it. The warm front will cross
the CWA Sat and we`ll remain in the warm sector Sun as the low
heads E thru Canada. The trailing cold front will slam thru here
Sun night or Mon with a surge of much colder air. Chilly high pres
over the Wrn USA will then build-in Tue.
Temps: We`re going to be stuck with lots of clds over the rgn
thru Thu. That will keep the diurnal range of temps suppressed
(cooler highs and milder lows). That should change Fri with a big
2-day warm-up in store for Sat-Sun. There will be an unusually
warm plume of air developing and spreading over the Plns. 850 mb
temps could be as high as +18C. Some guidance says our fcst is not
nearly warm enough! As of this fcst we are now advertising highs
ranging from 45 near OLU to 60 over the SW fringe of the
CWA...with low 50s in the Tri-Cities. Sun there is bigger bust
potential. We`re indicating 50s over the NE 1/2 of the CWA and 60s
over the SW 1/2. It`s psbl that mid-upr 60s could flood the
entire CWA. Even if that doesn`t pan out ...we`re still looking at
a very very mild wknd. Tue temps could be locked in the 20s for
highs with widespread cloud cvr.
Precip: Nothing significant in the offing. The 06Z and 12Z NAM
suggest there could be a touch of -SN Thu AM ahead of that shrtwv
trof. The 12Z EC lends a little support. The GFS doesn`t develop
any QPF until it`s E of the CWA. This minor potential is not
currently in the fcst...but it may need to be added if confidence
increases. If anything falls...it is looking very minor (less than
0.10 QPF) just acrs our NEB counties. The fcst is dry until Mon
night and even that`s not looking that good...with very
light/minor QPFs.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday)
Issued at 558 PM CST Tue Jan 28 2020
Ceilings will be difficult off the bat as there appears to be a
hole in the MVFR stratus, but this should fill in and lower over
time. I expect visibility to lower quite a bit over time as the
stratus descends. Winds will remain light.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...Dense Fog Advisory until 10 AM CST Wednesday for NEZ039-040-046-
047-060>062-072>075-082>085.
KS...Dense Fog Advisory until 10 AM CST Wednesday for KSZ005-006-017-
018.
&&
$$
UPDATE...Heinlein
SHORT TERM...Kelley
LONG TERM...Kelley
AVIATION...Heinlein
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
530 PM CST Tue Jan 28 2020
.SYNOPSIS...
Issued at 307 PM CST Tue Jan 28 2020
A fairly active H5 pattern was noted across the CONUS this
morning. A broad trough of low pressure extended along the ND/MT
border south into the panhandle of Texas. West of this feature, a
ridge extended from southern Nevada into southern Alberta. West of
this ridge, a trough of low pressure was off the coast of
Washington state, Oregon and northern California. Across the
eastern CONUS, a shortwave was located over the western portions
of Lake Superior with a stronger, closed low, over the Canadian
Maritimes. As of midday, the H5 trough had migrated east and
extended roughly along US highway 83 from Bismarck ND, south to
North Platte NE. Skies immediately west of the trough axis have
cleared and westerly winds have developed helping to scour out low
cloudiness. East of the trough axis, a broad shield of low clouds
were noted along with some patchy fog and light snow.
Temperatures as of 2 PM CST ranged from 34 at O`Neill to 45 at
Ogallala.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 307 PM CST Tue Jan 28 2020
The threat for precipitation will
end in the eastern forecast area late this afternoon. However, low
clouds will persist into the evening and overnight in the east. With
light winds in place and abundant boundary layer moisture from
precipitation currently falling, a good setup for fog exists in the
eastern half of the forecast area. The latest NAM12 and HRRR
indicate a saturated boundary layer tonight, east of highway 83 and
their surface visby fcsts, have widespread visibilities below a mile
tonight east of this line. Further support for fog lies with the
latest SREF ensemble fcst, as it has a 70-90% probability of <3 mile
visibility overnight from Custer county north to Keya Paha county
and points east. That being said, went ahead and inserted fog in the
forecast east of highway 83 tonight. Fog will persist into the
morning hours on Wednesday in the east and will be slow to burn off
as winds will remain light tomorrow. Further west, a weak
disturbance will push into the central Rockies. This will develop
some very light precipitation downstream, some of which may impact
the northern panhandle Wednesday afternoon. Elsewhere, mostly
cloudy skies are expected on Wednesday, however, temperatures will
remain fairly mild with highs in the upper 30s to lower 40s. Lows
Wednesday night will be in the mid 20s. Like tonight, winds will be
fairly light, so will need to pay attention to fog potential for
tomorrow night. This will be dependent on the amount of sun and
drying that can take place on Wednesday. Right now we could see some
decent drying in the west Wednesday which would limit fog
development. However, in the east, there is a much better
probability for fog development Wednesday night.
.LONG TERM...(Thursday through Tuesday)
Issued at 307 PM CST Tue Jan 28 2020
On Thursday into Thursday evening, a trough of low pressure aloft
will track across the northern and central Plains. The best
forcing will be well south of the area, so higher precipitation
chances will be seen in the southern plains. Across western and
north central Nebraska, weak forcing will lift across northern
Nebraska Thursday evening. Inherited some low pops in northern
Nebraska and will leave them in the current forecast package.
Beginning Friday, a large ridge of high pressure will build into
the western Conus. this ridge will transition east Saturday into
Sunday. After highs in the 40s for Friday, readings will reach
well into the 50s and 60s for Saturday and Sunday. Some readings
may approach 70 in far SW Nebraska for Sunday. Will need to
monitor the fire weather situation in SW and Wrn areas, especially
Sunday, as minimum RH may reach the 15 to 20 percent range and
some gusty winds may develop. A strong cold front will push into
the region Sunday night or Monday. The latest GFS has sped up the
frontal timing, no pushing it through the area Sunday night. Much
cooler temps are expected Monday into Tuesday behind the front.
Highs Monday will be in the 30s to lower 40s, with mid 20s to mid
30s for Tuesday. The threat for snow will increase as well behind
the front with the best chances Monday and Monday night.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 530 PM CST Tue Jan 28 2020
Widespread LIFR in fog and very low ceilings is likely to develop
along and east of a line from KANW-KBBW tonight from about 03z-06z
onward. These conditions will improve to IFR/local LIFR 18z-00z
Wednesday. VFR is generally expected along and west of highway 83
tonight and Wednesday.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Buttler
AVIATION...CDC
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
954 PM CST Tue Jan 28 2020
.UPDATE...
Issued at 922 PM CST Tue Jan 28 2020
Water vapor imagery and the RAP 1.5 PVU analysis field both
depicted one PV anomaly across TX/OK/AR and a second PV anomaly
across NEB which was more elongated and had significant
meridional extent. The locations of these features were in
generally good agreement with model guidance depictions of H5
vorticity for 03z which leads to greater certainty in the
forecast. These features are still expected to progress across
the region overnight and tomorrow, bringing light snow and minor
snow accumulations to the LSX CWA.
Overall, this looks like a minor snow event. The basis for this
statement is that forecast PW values are elevated but not
especially high (near the 75th percentile for Jan), BUFKIT
profiles do not show the classic cross-hair signature for enhanced
snowfall, overall synoptic lift appears quite modest based on
Q-vector divergence, and there does not appear to be any jet
coupling to provide additional large-scale ascent.
As the previous AFD mentioned, there is some uncertainty about
the northern extent of the snow produced by the southern PV
anomaly (due to the location of the frontogenesis bands) and the
southern extent of the snow produced by the northern PV anomaly
(due to limited moisture availability). This means that the I-70
corridor in MO and the I-64 corridor in IL will effectively be on
the fringes of both features, leading to a minimum in snow
accumulations across the St. Louis metropolitan area. This agrees
well with the current gridded forecast, therefore no significant
changes have been made to the forecast snowfall amounts at this
time.
Kanofsky
&&
.SHORT TERM... (Through Late Wednesday Night)
Issued at 339 PM CST Tue Jan 28 2020
Tomorrow`s snowfall will be produced by two separate but
concurrent weather systems that will move over the bi-state
region. Both are embedded in a larger trough that will move over
the bi-state region. The large scale lift and moisture surging
northward around a surface low in the Texarkana region will
produce light snow across the southern half of the CWA tonight
into tomorrow morning. Light snow will fall throughout the day and
will be confined largely to areas south of the Missouri River.
Heaviest snowfall rates will occur early Wednesday morning,
producing up to 0.5 inches of accumulation in southeastern
Missouri. The northward extent of snowfall is still uncertain at
this time with a large spatial spread in the hi res models. It
currently looks like the cut off line for the snow accumulation
associated with this system will be around the St. Louis metro
area, where accumulations around 0.1 inches are anticipated.
The second system will move southeast through the Iowa-Missouri-
Illinois area during the day on Wednesday while snow is ongoing in
southern Missouri and Illinois. This second system is associated
with a strong upper level disturbance moving through the area along
the Missouri-Iowa border. This northern stream has limited moisture
supply and is expected to only produce a dusting of snow, if any, in
our northern CWA. The southern extend of this system is also
uncertain and could contribute an additional 0.1 inches of snow
accumulation to the broader St. Louis metro area.
Both systems will exit the area by early evening on Wednesday,
leaving as much as an inch of snow accumulation in the eastern
Ozarks and southeastern Missouri with less than a quarter of an inch
across the remainder of the CWA.
MRM
.LONG TERM... (Thursday through Next Tuesday)
Issued at 339 PM CST Tue Jan 28 2020
Dry weather will prevail for much of the long term forecast, our
next chance for precipitation looks to be early next week.
Temperatures will moderate through the week, peaking in the mid to
upper 50s by Sunday and Monday, almost 15 degrees above normal.
MRM
&&
.AVIATION... (For the 00z TAFs through 00z Wednesday Evening)
Issued at 527 PM CST Tue Jan 28 2020
SPECIFICS FOR KUIN, KCOU: IFR conditions are expected to prevail
for the majority of the valid TAF period due to a low pressure
system which is moving through the region. Light snow is also
expected at both terminals after 12z. Initially variable winds
will become northwesterly to northerly after 20z once the low
pressure system has moved away from the region.
SPECIFICS FOR KSTL, KSUS, KCPS: Intermittent IFR conditions are
possible at the St. Louis metropolitan area terminals, but MVFR
conditions should prevail for at least several more hours until a
solid IFR deck moves overhead. Light snow is also expected after
09z, although since the St. Louis area will be on the northern
edge of the precipitation shield, there is a slim chance that the
snow could remain south of some of the St. Louis metro area
terminals.
Kanofsky
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Winter Weather Advisory until noon CST Wednesday for Boone MO-
Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
Iron MO-Jefferson MO-Madison MO-Moniteau MO-Osage MO-
Reynolds MO-Saint Francois MO-Sainte Genevieve MO-
Washington MO.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Portland OR
253 PM PST Tue Jan 28 2020
.SYNOPSIS...An active weather pattern will continue to produce above
average temperatures, periods of rain and high mountain snow through
the weekend. Cooler temperatures and lower snow levels appear likely
early next week, though.
&&
.SHORT TERM...Today through Friday...Water vapor satellite imagery
shows a shortwave trough over the Pacific Northwest digging
southeastward into the Great Basin. A trailing surface-850mb low
pressure is located off the north Oregon coast this afternoon.
Models are in good agreement it will continue to weaken as it pushes
ashore late this afternoon. Strong low to mid level flow in a
conditionally unstable environment will continue to wring out showers
to the south and east of the low pressure track late this afternoon
and early this evening. Snow levels are currently hovering between
3000-4000 feet this afternoon and will plan on letting the Winter Wx
Advisory for the Cascades expiring at 4 PM. Models are in good
agreement shortwave ridging will shift eastward towards the region
this afternoon and evening, which will result in a subsidence
inversion lowering to near 850mb by late this evening. This should
result in showers decreasing in both coverage and intensity through
that time.
The break in the wet weather will be short lived however. The next
storm system currently found in the Gulf of Alaska will drop
southeastward towards the region later tonight and Wednesday.
Models are in good agreement this will result in another round of
rain spreading southeastward across the region during this time.
This storm system appears progressive enough that hydrology impacts
should be limited, but brief sharp rises can be expected on our
smaller and faster responding rivers once again. Given the elevated
levels currently found on the Grays River, it will likely approach
minor flood stage once again tomorrow.
More uncertainty creeps into the forecast Wednesday night and
Thursday. Most model scenarios result in a warm front lifting back
northeastward across the region. While rain appears likely across our
northwestern zones regardless of model choice, particularly Thursday
afternoon and evening, there appears to be a decent chance that our
southern and inland zones could end up dry for most of the day. As a
result, have begun to lower PoPs, but even then rain chances may be a
bit overzealous.
Models then suggest an atmospheric river will take aim at western
Washington and Vancouver Island Friday. There is a lot of
uncertainty in where the southern extent of the precipitation will
end up. Current NBM guidance suggests areas north of Salem will end
up at least a little wet while areas south of Salem may in fact stay
dry the entire day. Anecdotally, it seems the southern periphery of
precipitation is often modeled too far south in these scenarios so
opted to keep temperatures on the warm side of model guidance. Our
current temperature forecast assumes that most areas from Portland
southward will dry out for at least a few hours Friday afternoon and
high temperatures will top out around 60F. /Neuman
.LONG TERM...Friday night through Tuesday...Guidance continues to
show the bulk of the moisture streaming into western WA late Friday
so will trend PoPs down for our southern zones Friday night into
early Saturday. Models then show the cold front sagging south across
the forecast area on Saturday which will result in another round of
valley rain and mountain snow. The upper level trough looks to then
swing inland late Saturday into Sunday which will keep unsettled
weather over the region, with snow levels lowering to the Cascade
Foothill and Coast Range elevations and temps falling from around 5
to 10 degrees above normal to near normal. A colder air mass looks
to then settle in over the region late Sunday into early next week,
with snow levels at night lowering to near the valley floor and
temps cooling to near freezing. This could result in a brief period
of lowland snow Sunday night, but due to model uncertainty will keep
a mix of rain and snow in the forecast. Despite the low snow levels
on Monday it also looks like rain chances will be waning so cannot
rule out the development of patchy fog, freezing fog, and frost
Sunday night. Transient shortwave ridging looks to then dry us out
even further late Monday, but with saturated soils and near freezing
temps expect areas of fog, freezing fog, and front across the
forecast area Monday night. Guidance then shows rain returning on
Tuesday as another disturbance moves across the Pac NW. /64
&&
.AVIATION...Upper level trough axis was crossing the Cascades
early this afternoon. Typical post-frontal MVFR/VFR mix along
the coast and interior lowlands early this afternoon and will
persist into early evening as daytime heating helps to promote
shower activity. Most persistent MVFR through 02Z Wed will be
over the Oregon Coast Range and Cascade foothills as well as the
west end of the Columbia River Gorge and Willapa Hills. West 850
mb wind flow of 15-30 kt through early evening will also result
in mountain obscurement. Conditions become more VFR by early
evening with decreasing shower activity, especially for the
inland TAF sites. Leading edge of the next warm front reaches the
coast between 09Z and 12Z Wed and will lower conditions to low-
end MVFR or even IFR. Inland areas become more MVFR overnight,
with steadier precipitation developing 12Z to 15Z. IFR to MVFR
conditions will prevail for the coastal areas through much of
Wed. Expect mainly MVFR for the interior lowlands north of about
KS12 Wed. Valley areas south of KS12 may see more VFR 16Z-21Z
Wed, ahead of the cold front.
KPDX AND APPROACHES...A mix of MVFR and VFR through about 02Z
Wed. Conditions become more VFR around 00Z Wed, but then settle
back into MVFR around 10Z as warm air advection results in lower
cloud bases. Steady precipitation develops around 15Z Wed for
continued MVFR conditions. Weishaar
&&
.MARINE...Timely 19Z ASCAT pass revealed a surface low pres
center just north of Cape Disappointment. This can also be
surmised from the 20Z wind speed observations. Buoy 46029 had
minimal wind, generally around 5 kts, while 46050 reported gusts
just above 25 kt. The 12Z GFS, ECMWF and even the 18Z NAM did
not seem to have a good handle on location and depth of the
surface low. The back edge of the bent back occlusion appears to
have moved through the central and south Oregon waters as of
18Z.
12Z model runs show a gradually weakening surface gradient through
the evening, with wind gusts south of Tillamook Bar falling below
20 kt by 06Z Wed. The next warm front reaches the north waters by
12Z Wed. The NAM and GFS suggest boundary layer wind speeds of
30-35 kt over PZZ270 around 12Z. Gale force wind gusts look
likely for PZZ270 and PZZ250 beginning around 12Z and then
spreading into the northern portions of PZZ275 by 15Z. The RAP,
Hi-Res ARW, NAM and higher resolution HRRR suggest 30 kt boundary
layer wind speeds spreading over the majority of the area by 15Z
Wed. Will go ahead and issue gale warnings for the waters with
valid times 12Z-21Z for PZZ250 and PZZ270 and 15Z-21Z for PZZ255
and PZZ275. Confidence is a little lower south Heceta Head, but
feel the area from Cascade Head to Heceta Head has a high
probability of gale force gusts. Yet another warm front moves
through the waters Thu, but not anticipating gale force gusts
with this system as models show it more north. Eventually, a sharp
cold front swings through the waters Sat, which may produce near
gale-force northwest wind gusts.
Seas will hold steady in the 12-15 ft range through Wed and then
may reach 14-17 ft Wed evening through Wed night. Seas settle
back into the 11 to 13 ft range late Thu, but build into the
mid-teens Sat. There is concern for sneaker waves Thu with wave
heights 13-15 ft and relatively long periods of 15-17 seconds.
The weekend also poses potential sneaker wave concern, although
shorter periods of 12-13 seconds are expected. The predominant
swell direction will be 240-270 degrees through Sat. Models then
show a 13-15 ft northwest swell becoming the dominant train Sat
night through Sun. Weishaar
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 4 PM PST this afternoon for
Cascades in Lane County-Northern Oregon Cascades.
WA...Winter Weather Advisory until 4 PM PST this afternoon for South
Washington Cascades.
PZ...Small Craft Advisory until 4 AM PST Wednesday for coastal
waters from Cape Shoalwater WA to Cascade Head OR out 60
NM.
Gale Warning from 4 AM to 1 PM PST Wednesday for coastal waters
from Cape Shoalwater WA to Cascade Head OR out 60 NM.
Small Craft Advisory until 7 AM PST Wednesday for coastal
waters from Cascade Head OR to Florence OR out 60 NM.
Gale Warning from 7 AM to 1 PM PST Wednesday for coastal waters
from Cascade Head OR to Florence OR out 60 NM.
Small Craft Advisory until 4 PM PST Wednesday for Columbia
River Bar.
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This discussion is for Northwest oregon and Southwest Washington
from the Cascade crest to 60 nm offshore. This area is commonly
referred to as the forecast area.