Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/04/21
Area Forecast Discussion
National Weather Service State College PA
1034 PM EST Sun Jan 3 2021
.SYNOPSIS...
High pressure ridging is likely over the area early next week.
But, the northwest flow will last for a few days, keeping it
more cloudy than a typical high pressure set up. The only thing
of note for this week is a storm system which looks like it
will scoot by just to our south late next week.
&&
.NEAR TERM /UNTIL 7 AM MONDAY MORNING/...
All is working out very well. Snow amounts are near 6" (and
maybe slightly higher by now) to the NE of KIPT where elevation
and pivoting band of precip put them in a sweet spot. The rest
of the area has warmed just a degree or two as the high clouds
exit and the lower clouds are keeping the temps from dipping
just yet. The possibility of freezing drizzle will return to the
western highlands when the temps get to freezing later tonight.
Most roads are probably well treated, and the FZDZ should be
patchy at worst. If it does start to look like the FZDZ will be
more- widespread, we can issue an advy.
Prev...
Snow is a little slower to exit the northern tier than expected,
and latest RAP has some good slantwise convection parameters
going over the next two hours for the NE 4-5 zones. Have tweaked
the timing/groupings of advy segments very slightly to allow for
this. Snow amounts may be an inch or so higher, too, as we got
to 2-3 inches across much of Happy Valley, and likely a little
more on the surrounding hill tops. Temps have gone above
freezing for the areas behind the snow shield and may hold
steady for a few hours with lots of clouds overhead. But, a
slight slide is still expected later tonight. Have continued to
mention patchy -ZL/--SHSN for the overnight over the western
mountains.
Prev...
Quick hitting snow from closed upper trof pushing into western
PA this afternoon with 1 to 3 inches of snow across much of
central and north central PA. HREF indicates locally heavy
snowfall rates from KIPT northeastward through 00z this evening,
so locally higher amounts of 4"+ expected in parts of Sullivan
and Lycoming Counties.
Precip tapers off from west to east this evening, as upper low
exits the state. Nearly saturated forecast soundings beneath
subsidence inversion indicate there will likely be lingering
very light precipitation tonight where the westerly flow is
forced to ascend the Alleghenies Plateau. Model soundings
indicate cloud top temperatures will be too warm to support
snow, so expect patchy drizzle/freezing drizzle. Do not expect
lingering travel issues however, as road surfaces should already
be treated and temperatures should be no colder than the low
30s.
&&
.SHORT TERM /7 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
Surface ridge builds into the region Monday, resulting in dry
weather for most of the area. However, shallow layer of moisture
beneath inversion is likely to result in persistent stratocu.
Model soundings still are nearly saturated between 0-1km over
the Allegheny Plateau, where upslope flow could yield lingering
spotty drizzle/freezing drizzle.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Most of the coming week looks relatively benign, weatherwise,
with seasonably chilly temperatures for early January. Highs
will be a few degrees above normal while lows will be 5-10
degrees above normal.
There could be a few snow showers through Tuesday, primarily
over the northern and western highlands, but nothing widespread
or particularly heavy is expected. Cloud cover will be
widespread across the northern and western mountains and only
partial coverage south and east of the Alleghenies.
A low pressure system will pass to our south on Friday, but
model consensus keeps precipitation south of the Mason-Dixon
line. As such, have kept PoPs very low. Will continue to
monitor.
&&
.AVIATION /04Z MONDAY THROUGH FRIDAY/...
Light snow continues at IPT, but should taper off soon. DZ/FZDZ
may develop at JST and BFD this evening, resulting in reduced
visibility toward daybreak. As the band of snow drifts south and
east, could see reductions to IFR become persistent at MDT and
LSN for a few hours. Light westerly winds and steady- state
cigs will continue through the overnight hours, with IFR
continuing in the western airfields and MVFR elsewhere.
Cigs will rebound a bit during the day on Monday, though MVFR
will prevail across the area.
Outlook...
Tue...Lingering reductions in -SHSN at BFD and JST. Becoming VFR
elsewhere.
Wed-Fri...Generally VFR.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 11 PM EST this evening for
PAZ037-041-042-046.
&&
$$
SYNOPSIS...DeVoir/Dangelo
NEAR TERM...DeVoir/Fitzgerald/Dangelo
SHORT TERM...Fitzgerald
LONG TERM...Evanego/Banghoff
AVIATION...Banghoff
Area Forecast Discussion
National Weather Service Des Moines IA
519 PM CST Sun Jan 3 2021
...Updated Aviation Discussion...
.SHORT TERM.../Tonight through Monday Night/
Issued at 237 PM CST Sun Jan 3 2021
Confidence: Medium
Forecast confidence again reduced a bit due to the likelihood of
additional fog overnight tonight. Though the HRRR had a decent idea
of last night`s event, it took longer to develop and even then the
areas of fog bookending our county warning area did not fully merge
over the entire region. Not only affecting the visibility, but also
overnight lows that hit 0 or in the lower single digits at several
sites. Excellent examples of hoar frost/deposition overnight,
however. This morning`s sfc weather map shows the ridge of high
pressure now over eastern Iowa at 15z, while a warm front is
currently edging into the eastern counties of Nebraska. Temperatures
have warmed to above freezing over the west and southwest this
afternoon and with melting, dewpoints have climbed into the mid
20s to the lower 30s in those areas. Lower dewpoints continue
over the central to northeast counties, similar to last night.
Will need headlines tonight for some dense fog. The problem
remains how much coverage is anticipated and timing. Overall
thinking is that it may take a few hours to settle into the area,
so will delay start time until mid evening. For now will go with
more of a persistence forecast. Tonight`s fog is again a difficult
coverage issue due to the combination of radiational cooling
northwest, west and southeast and likely advection fog in the far
south. Some limiting factors are slightly stronger surface winds
at the sfc and a warming column which tends to mitigate fog
development somewhat.
Again tonight, it looks like we will end up with areas of dense fog
and areas of lesser to no fog, but attempting to nail those down
with certainty remains a challenge. Tonight`s advisory will have
an ending time at 15z. By early Monday morning, an approaching
cool front will sweep into western Iowa and eventually get through
our area by 18-20z. This will end the fog threat for the day. The
front is expected to pass through with little moisture, but may
be able to squeeze out a few light sprinkles/mist northeast in the
form of freezing precipitation with no impacts expected. The
remainder of the day will see highs in the mid 30s with some
locations in southwest Iowa in the upper 30s. With the front
having taken out some of the moisture tomorrow night, fog chances
now look less into Tuesday morning. Lows are expected to drop to
the teens.
.LONG TERM.../Tuesday through Sunday/
Issued at 237 PM CST Sun Jan 3 2021
Confidence: Medium through Wednesday Increasing into the Weekend
No significant changes to the extended period. The GFS/Euro split
ways again with the Euro holding onto the Great Lakes High through
midweek while the GFS allows a faster retreat of the ridge northward
into Canada. Overall climatology would favor a slower retreat of
the ridge. The GFS bias of more energy in the northern stream may
also be overdone. For now, we continue with slight/chance PoP for
rain or snow into midweek with no significant development or impacts
expected here. Both models are trending toward consolidating the
energy over the southern Mississippi River Valley and moving the
storm east. High pressure is expected to follow into the weekend
with generally dry and seasonal conditions expected through
Saturday. Sunday a subtle push of colder air will move south into
Iowa and will likely drop temperatures back into the 20s regionwide.
&&
.AVIATION.../For the 00Z TAFS through 00Z Monday evening/
Issued at 508 PM CST Sun Jan 3 2021
LIFR fog will once again overspread the state this evening into tonight.
KOTM and KDSM will likely be the first of our forecast terminals
to experience significant visby reductions as an area of fog moves
north out of Missouri. Eventually the rest of the central tier of
the state will fill in overnight. A front sweeping through the
state will help break up the fog Monday morning, however low cigs
will persist and keep IFR/LIFR conditions in place until clearing
up Monday afternoon.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory from 9 PM this evening to 9 AM CST Monday for
IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097.
&&
$$
SHORT TERM...REV
LONG TERM...REV
AVIATION...Martin
Area Forecast Discussion
National Weather Service Key West FL
1017 PM EST Sun Jan 3 2021
.DISCUSSION...
Some patchy fog is possible during the overnight hours over
Gulfside/Bayside waters and over the Keys. Winds are in the
process of turning light northerly right now thanks to an
approaching cold front. Even after the wind shift, it will take a
few hours for the near-surface layer to start drying. So the muggy
air (70+ dewpoints) coming off cooler waters (SSTs of 68-70F)
north and northwest of the islands could support some patchy sea
fog, which could then drift south across the islands. Observations
from Naples this evening would suggest more of a low stratus as
opposed to fog. However, the HRRR explicitly shows an area of
dense fog spreading southward across the islands overnight.
Unfortunately, it is hard to confirm fog in satellite imagery due
to a mid-level deck that is obscuring the view below. By daybreak,
dewpoints over the islands should be drying through the mid 60s,
which should put an end to fog potential and cause low stratus to
start lifting.
MIMIC PW imagery shows the greatest integrated moisture north of
the surface front, with PW values as high as 1.8" sliding down the
SW FL coast between Ft. Myers and Naples. The often happens when
the post-frontal layer of cooler air is quite shallow and a mid-
level reflection hangs back. This seems to be the case. So the
limited chance of showers will mainly occur on Monday morning,
well behind the initial northerly wind shift that is in progress
now.
On Monday afternoon, dry air will deepen. Skies will clear, and
shower chances will vanish.
&&
.MARINE...
The Pulley Ridge buoy, located 88 miles northwest of Fort
Jefferson, is observing a west-northwest wind wave of 4 feet at 6
seconds. The buoy is now well northwest of a weak cold front that
is now reaching the Keys.
Patchy fog is still in the forecast overnight over Gulf waters,
Florida Bay, and the Keys.
Northerly breezes will rise overnight and become moderate by
Monday morning in the wake of that cold front. There is no need
for cautionary headlines or a Small Craft Advisory at this time.
From synopsis...A weak cold front passed the Keys this evening and
will drag into the Straits overnight. Northerly breezes will
increase overnight and become moderate by Monday morning. Moderate
to possibly fresh northerly breezes will ensue Monday night and
Tuesday behind the front. Breezes will become northeasterly by
Tuesday night, and southeasterly by Thursday night. A second cold
frontal passage is possible by Friday or Friday night.
&&
.AVIATION...
SCT low stratus with bases below 010 are likely for a few hours
overnight in the wake of a shallow cold front that is now passing
the Keys. Short periods of BKN cigs and 3-6SM vsby are possible in
mist, though the latest HRRR shows a few hours of dense fog near
the terminals overnight. On Monday morning, a few sprinkles or
light rain showers are possible, originating from a cloud deck
above the shallow layer of cool air that will only be about 2,000
feet deep at sunrise. Later Monday morning, northerly surface
winds will increase to 10+ knots, bringing a drying and clearing
trend for Monday afternoon.
&&
.CLIMATE...
On this date in 2020, the daily record warm low temperature of
78F was last recorded at Key West.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...Haner
Aviation/Nowcasts....Haner
Data Acquisition.....DR/LIW
Visit us on the web at weather.gov/key
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Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
556 PM CST Sun Jan 3 2021
.SHORT TERM...
336 PM CST
Through Monday night...
An upper level low is moving away from us to the east, while a
surface high over Louisiana ridges up just west of our region.
Further west a trough is over the northern/central Great Plains
moving east. With ridging approaching our winds are light from the
west. An extensive area of MVFR to LIFR ceilings and low
visibilities covers are entire region, with ceilings from 200 to
1100 ft, and visibilities from a quarter mile up to 4 miles.
The low levels remain moist, and with the ridge axis moving over our
CWA, visibilities are expected to go down once again, with dense fog
expected west of a line running from McHenry County to Ford County
starting around 6 PM and going until mid morning Monday.
Visibilities are expected to reach 1/4 mile in the west, and 1 to 2
miles in the eastern CWA, although occasional lower visibilities can
occur. Cloud ceilings are expected to remain generally below 1500 ft
during the short-range forecast period.
Winds will back to southwesterly ahead of the trough, and a little
breezy in the northern counties. The trough reaches our region
Monday afternoon, with some light precipitation expected.
Atmospheric profile lowers the atmospheric column temperature below
freezing with arrival of this system, so precipitation is expected
to be light snow, with little accumulations expected at this time.
The system is expected to exit our region to the east sometime
around midnight Monday night, veering our winds more northwesterly.
BKL
&&
.LONG TERM...
344 PM CST
Tuesday through Sunday...
After the quick chance of light rain or snow Monday afternoon into
evening, the remainder of the extended forecast looks relatively
quiet with seasonably mild temperature trends...generally in the
30s most afternoons. Late Wednesday into Thursday models are
showing a sprawling upper low passing to our south, so it is
possible we may see some light precip wrapping around the north
side of this feature. At this range only feel comfortable carrying
slight chance POPs and mainly for southern portions of the area.
Lenning
&&
.AVIATION...
For the 00Z TAFs...
Concerns:
-Lowering of cigs to LIFR tonight, possibly VLIFR late tonight
into early Monday
-LIFR visibility, and whether our not 1/2SM Vsby will make it to
ORD and MDW
-Continued LIFR/IFR cigs Monday
-Timing of a brief window of -SN Monday night
Cigs have lifted to MVFR near Chicago but this should be temporary
as low level flow turns around to the southwest with a plethora of
IFR and LIFR cigs upstream. Confidence on lowering cigs is
therefore high, and likely to go down to LIFR. Confidence is lower
with regards to how low the visibility will go. We do expect 1/2SM
to sneak into KRFD but unsure at ORD/MDW. LAMP, RAP, and HRRR all
bring very low visibility all the way to the Chicago terminals.
HREF and SREF probabilities are 70 and 60 percent respectively.
With this, we have left the 1/2SM TEMPO in, but forecast soundings
do depict 10-15 kt of wind at the top of the boundary layer
tonight which would suggest we keep things mixed and maybe it is
not as conducive to the fog.
Expect a slow lifting at best on Monday with the low level
inversion locked in place and the inversion height not expected to
move very much.
A band of light snow will move through quickly Monday evening.
This will be a quick hitter, maybe up to 2 hours in any one
location. Guidance is a tad slower than previous and currently
pegs a 2 hour window either from 1-3z or 2-4z for the Chicago
terminals, 0-2z for KRFD. Winds will hold SW through most of the
TAF period.
KMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Dense Fog Advisory...ILZ003-ILZ004-ILZ005-ILZ008-ILZ010-ILZ011-
ILZ012-ILZ019-ILZ020-ILZ021-ILZ032-ILZ039 until noon Monday.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion...CORRECTED
National Weather Service New York NY
852 PM EST Sun Jan 3 2021
.SYNOPSIS...
Low pressure off the Mid Atlantic coast will pass well south and
east of Long Island tonight into Monday, then meander out over
the waters south and east of Nova Scotia into much of this week
as high pressure slowly builds from the west. Another coastal
low pressure system is possible this weekend.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Low pressure about 275 miles southeast of Long Island will
slowly deepen as it tracks away from the coast tonight. A 500 mb
low is approaching and some energy should start to transfer to
the offshore low overnight. Light to occasionally moderate snow
has been falling across the Lower Hudson Valley and into SW
interior CT. Have even seen some snow make it towards I-95 in SW
CT. Precipitation has had a much more difficult time making it
to the ground across eastern CT due to weak lift and lingering
dry air. More than trace amounts in Middlesex and New London
Counties may be difficult to achieve.
Regional radar mosaic is showing the overall precip shield
diminishing somewhat and this trend should slowly continue
through around midnight. The overall intensity of the
precipitation will lighten in the next few hours so expect snow
accumulation across the interior to lessen heading towards
midnight. Still looking at a total of 2-3 inches across Orange,
Putnam and Northern Fairfield and possibly higher elevations of
northern New Haven. Across the rest of the advisory, amounts
are likely to end up lower.
As the energy from the 500 mb trough and opening upper low pivot
overhead tonight, there may be some light precip continuing in
the advisory area. Already noting precip with the upper low
holding together fairly well as it tracks across NE PA. The
HRRR is also indicating potential for a few bands of light snow
to pivot south overnight. There may also be some light freezing
rain or freezing drizzle across the interior or higher
elevations in areas with lack of snow growth. The advisory may
need to be extended into early Monday morning.
Temps tonight should either remain nearly steady or fall only
slightly, with lower 30s well inland, and mid/upper 30s closer
to the coast.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Low pressure will continue to deepen well east of the New
England coast with NE-N winds and temperatures slightly above
normal. Deep-layered cyclonic flow and residual low level should
maintain clouds, along with slight chance of a snow/rain shower
Mon night from NYC west.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
The area remains embedded in a longwave trough through much of
the middle of the week as pieces of mid-level vorticity round
the base of the trough and interact with the stalled surface low
S of the Canadian Maritimes. The interaction with the surface
low will allow for the low to wobble a bit. This may allow for
the low to retrograde slightly and bring in the potential for a
few rain or snow showers for the northern and easternmost
portions of the CWA.
With the trough overhead and very cold mid and upper level
temperatures, much of these showers may be driven by daytime
heating and associated instability as the boundary layer mixes
and becomes dry adiabatic during the daytime on Tuesday.
The low continues to spin S of the Canadian Maritimes on
Wednesday, but moves eastward as the longwave trough pushes it
away from the area. This allows for some brief ridging to set up
by Thursday with surface high pressure sliding into the area.
Global models continue to have decent agreement in the
development of a low pressure system to our south late in the
week and into the weekend, though timing is more uncertain. It
appears that a cutoff upper level low and associated mid level
vorticity over the Plains and Southeast states will eject off
the Coast and develop a surface low. Most models are keeping
the coastal low south of our area as there is no northern stream
blocking to provide for a northward push of the low or
substantial cold air over our area. With a very active and
amplified jet stream, confidence on any particular outcome is
low this far out. Details on the development, track, intensity,
and timing of the low should become clearer as the week
progresses but as of now, it`s just something to keep an eye on
in the Friday to Sunday time frame.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Low pressure will pass well SE tonight, intensifying as it
slowly slides out into the open Atlantic on Monday.
IFR conditions expected tonight with -RA at NYC metro and Long
Island terminal. There may also be some snow mixed in with rain at
times. At KHPN, the precip has changed to -SN with generally less
than an inch expected. There could be a mix of -RA at times as
well. At SWF, all snow is forecast with 1-3" of accumulation
before ending 04-06Z.
The precip should diminish in coverage after midnight, ending from
west to east early Monday morning.
IFR conditions become MVFR early Monday morning. VFR is possible
late Monday afternoon.
NNE winds 10-15 kt this evening, backing to the N 8-12 kt
overnight. N winds continue on Monday 10 kt or less.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Fluctuations in visibilities this evening, but flight category
should prevail IFR.
.OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY...
.Monday Night...MVFR ceilings.
.Tuesday-Wednesday...VFR. NW gusts 15-20 kt possible.
.Thursday...VFR.
.Friday...Mainly VFR. Slight chance of MVFR in -RA/-SN Friday
night.
&&
.MARINE...
An extended pd of SCA conds expected on the ocean as low
pressure passing to the south and east thru Monday meanders
about S and E of Nova Scotia for much of this week. Can`t rule
out occasional marginal SCA conds at times elsewhere Tue through
Thu as wind gusts approach 25 kt.
Winds and seas then look to drop below SCA thresholds throughout
from Thursday night through Friday night.
&&
.HYDROLOGY...
No significant precip expected through the week.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory until midnight EST tonight for CTZ005-
006.
NY...Winter Weather Advisory until midnight EST tonight for
NYZ067>070.
NJ...Winter Weather Advisory until midnight EST tonight for NJZ002-
004-103.
MARINE...Small Craft Advisory until 6 AM EST Tuesday for ANZ350-353-355.
&&
$$
SYNOPSIS...BG/MW
NEAR TERM...DS
SHORT TERM...BG
LONG TERM...MW
AVIATION...DS
MARINE...BG/MW
HYDROLOGY...BG/MW
Area Forecast Discussion
National Weather Service Portland OR
127 PM PST Sun Jan 3 2021
.SYNOPSIS...An active weather pattern will continue through at least
the middle of next week. The next weather system impacts the area
this evening through Monday night and will bring significant snowfall
to the higher elevations of the south Washington Cascades, with
lesser amounts in the north and central Oregon Cascades. Additional
weather systems follow through mid-week. A brief break in the action
is expected Wednesday night through Thursday, but a return to wet
conditions is likely Friday.
&&
.SHORT TERM...Tonight through Wednesday...Early afternoon water vapor
imagery showed last night`s cold front extending from northwest
Montana to southern Oregon. Another surface low seemed to be
developing near 40N 139W. Weak ridging was noted at 125W. At 21Z KRTX
dual-pol doppler radar indicated scattered shower activity across
southwest washington and extreme northwest Oregon.
The 12Z model output suggests the southern end of the aforementioned
cold front will stall over southwest and south central Oregon through
early evening. The next approaching warm front absorbs the remnant
cold front and lifts north tonight for renewed precipitation. Snow
levels rise above the passes tonight. However, low-level east flow
will result in lower snow levels on the east slopes of Mt. Adams and
in east Skamania County. Expect snow levels in those areas to hover
in the 4000 to 4500 foot range through Mon morning and then lower to
2500 to 3000 feet by late afternoon. Snow levels in the north and
central Oregon Cascades will be above 5000 feet through Mon morning
and then lower to 3500 to 4000 feet by late Mon afternoon.
The NBM, 4km WRF-GFS and the high-resolution HREF suggest 24 hr
snowfall amounts on the order of 10 to 20 inches above 4000 feet in
the south Washington Cascades tonight through Mon evening. Per
coordination with SEW have gone ahead and upgraded the Winter Storm
Watch to a warning. Warm-frontal over-running precipitation persists
through 12Z Mon along the coast and mid-morning for the Cascades. The
actual cold frontal boundary then moves ashore Mon morning and should
reach the Cascades by late morning. Will go with a Winter Weather
Advisory for the north and central Oregon Cascades above 4000 feet
valid Mon morning through 08Z Tue. Snow levels will be close to 5000
feet at sunrise, lower fairly quickly in the afternoon. Expect 12-hr
amounts 18Z Mon through 06Z Tue generally 4 to 8 inches around pass
level, but much higher amounts above 6000 feet. Westerly 850 mb flow
of 20-30 kt Mon afternoon through late Mon evening will provide
favorable orographic enhancement for the Cascades.
The 1ZZ NAM shows an upper level trough passage Mon evening, with one
final short-wave disturbance moving through the forecast area 00Z to
06z Tue. Shower activity looks to diminish fairly quickly late Mon
night and 500 mb ridging moves closer to the coast and associated
negative vorticity advection. This upper ridge does not appear to be
strong enough to bring dry conditions to the entire forecast area
Tue. The NAM, GFS and ECMWF all suggest the potential for some
warm-frontal over-running precip in southwest Washington and the far
north Oregon coast and Coast Range.
Another baroclinic boundary is forecast to reach the coast Tue
evening and then slowly work inland Tue night and Wed. The NAM
indicates multiple surface low pres centers developing along the
boundary Tue night, which would act to slow its eastward progression.
The NAM also suggests stronger surface low development near 42N 128W
early Wed morning. Should this occur, the bulk of the energy would be
directed into southwest Oregon and northern California. The 12Z ECMWF
hints at this as well, but the GFS migrates the surface low northeast
to near KONP by 21Z Wed. This would focus heavier precipitation over
the south half of the forecast area and potentially increase hydro
concerns.
Not expecting coastal high wind tonight as the surface orientation is
more southeast instead of the more favorable southerly. The 80m HRRR
output shows solid 45-50 kt wind gusts over the coastal waters
tonight, but slightly lower along the coastline. Think peak gusts to
55 mph along the headlands will suffice, but would not be surprised
if there were a few 60 mph gusts, especially on elevated coastal
terrain. Not enough to warrant a headline. Weishaar
.LONG TERM...Wednesday night through Sunday...Models in general
agreement early in the period. The operational GFS and ECMWF show an
upper trough shifting east of the Cascades Wed night, with sharper or
more amplified 500 mb ridging reaching the coastline 12Z Thu. The
ECMWF ensembles and ensemble mean support this trend. Will likely see
offshore low-level flow develop late Wed night or Thu for reasonably
high confidence in a return to dry conditions. Nearly all ECMWF
ensemble members show no QPF Thu.
Differences within the operational runs become more apparent Fri. The
ECMWF brings another frontal system into the area Thu night, while
the GFS shows a splitting system falling apart Fri as it reaches the
coast. About half of the ECMWF ensemble members resemble the
operational GFS. Would think with offshore flow in place any
approaching weather system would weaken or at least slow down as it
approaches the coast. Will maintain the NBM-provided low-end POPS
Fri, but would not be surprised to see these lower with time. The 500
mb cluster analyses valid 00Z Sun suggest some degree of upper level
ridging centered near the coast. This trend continues 00Z Mon as
well. All in all, it appears the active pattern comes to an end
around mid-week, with more dry time vs. wet time for the latter
portion of the extended period. Do not see any sign of lowland snow
or unseasonably cold air for at least the next 7 days. Weishaar
&&
.AVIATION...Moist west to southwest flow aloft. Generally, VFR
with brief MVFR with passing showers through rest of this
afternoon. Increasing mid and high clouds this afternoon into
the early evening as a warm front approaches from the southwest.
This warm front will push rain from south to north, starting over
Lane County late this afternoon, and reaching Columbia River by
03Z. Generally, MVFR tonight over much of the region as this warm
front passes. Timing shows warm front should be well north of
the Columbia River just after midnight.
Moist and mild air mass over region rest of the tonight. This
maintains persistent low VFR, with mix of MVFR and VFR along the
coast. A cold front farther offshore will be racing to the coast.
This cold front will maintain rain and mix of low VFR and MVFR
CIGS late tonight into Mon am. Not a lot of change through Mon
am, as air mass remains moist as front slowly pushes inland.
For detailed regional Pac NW weather information,
go online to: http://weather.gov/zse
KPDX AND APPROACHES...VFR into early evening, with increasing
mid/high clouds as warm front off to the southwest approaches.
Rain expected over ops area from around 02Z through 09Z as the
warm front lifts northward. Less rain, but low VFR for later
tonight into early Mon. Cold front arriving early Mon am, with
increasing MVFR and rain by 13Z. /Rockey
&&
.MARINE...An active weather pattern will continue over the northeast
Pacific through the first half of next week, keeping seas elevated
with systems periodically moving through bringing gale force winds.
Somewhat benign at the moment, as winds mostly 15 kt or less.
But, a warm front off the south will lift northward across the
coastal waters this evening. Southeast winds will turn southerly,
and increase, with peak gusts mostly 40 to 45 kt. That said, can
not rule out a stray gust up to 50 kt well offshore.
Warm front lifts on to the north of the area overnight. But, cold
front will be approaching from the west later tonight. This front
will push across the coastal waters early Mon am, and onshore by
mid-Mon am. Will maintain Gale Warning overnight into early Mon
am, as gradients still supportive of gales. Winds will ease once
the front passes. Rest of Monday sub-gale, with 15 to 25 kt.
Combined seas still somewhat high, running at 18 to 22 feet,
with the higher seas over the northern waters. Overall, seas will
stay in that range tonight, as increased wind waves will offset
any decrease in baseline westerly swell.
Seas will gradually ease back to 17 to 18 ft on Monday, perhaps a
bit lower Mon night. But, another front will arrive on Tuesday,
with building winds and seas once again. Likely to be strong
southerly gales on Tue, with seas near 20 ft again.
Unsettled weather continues through rest of the week, though does
not look like winds will be as strong as have seen recently. Seas
as well will slowly subside, likely stay in 15 to 20 ft range
through Fri.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...High Surf Advisory until 9 AM PST Monday for Central Oregon
Coast-North Oregon Coast.
Winter Weather Advisory from 7 AM Monday to midnight PST Monday
night for Cascades in Lane County-Northern Oregon Cascades.
WA...High Surf Advisory until 9 AM PST Monday for South Washington
Coast.
Winter Storm Warning from 10 PM this evening to midnight PST
Monday night for South Washington Cascades.
PZ...Small Craft Advisory until 8 PM PST this evening for coastal
waters from Cape Shoalwater WA to Cascade Head OR out 60
NM.
Gale Warning from 8 PM this evening to 4 AM PST Monday for
coastal waters from Cape Shoalwater WA to Cascade Head OR
out 60 NM.
Small Craft Advisory until 6 PM PST this evening for coastal
waters from Cascade Head OR to Florence OR out 60 NM.
Gale Warning from 6 PM this evening to 7 AM PST Monday for
coastal waters from Cascade Head OR to Florence OR out 60
NM.
Small Craft Advisory until 6 AM PST Monday for Columbia River
Bar.
&&
$$
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