Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/14/24
AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
933 PM EST Sat Jan 13 2024
.SYNOPSIS...
Cooler weather moves in this afternoon with much cooler weather
expected next week. There is the potential for wintry weather
across portions of the area late Monday through Tuesday. Very
cold temperatures are expected by midweek and again next
weekend.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
As of 930 PM EST Saturday...
High pressure is centered over the Deep South this evening, with
low pressure centered well to the N over southern QB. Clear this
evening, with a W wind diminishing, and temperatures ranging
from the mid 30s to lower 40s. The wind will continue to
diminish and shift to SW tonight. Lows tonight will be in the
upper 20s to mid 30s under a clear sky.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY NIGHT/...
As of 355 PM EST Saturday...
A secondary cold front will push through the area from late Sun
morning through Sun aftn with SW then W winds increasing to
15-20mph with gusts 25-30 mph (30-35 mph over the Eastern Shore)
during the aftn. Additionally, some of the CAMs including the
HRRR and Nam 3km show a narrow band of convection forming along
the arctic front across N portions of the FA late Sun morning
into Sun aftn, as it moves across the area. If there is enough
moisture, this would likely fall as snow/graupel, potentially
mixing with rain as it moves across the Eastern Shore during the
aftn. As such, have maintained a slight chance PoP to account
for this possibility (15-20% chance). Highs on Sun will range
from in the mid 40s extrm NW to the lower to mid 50s SE.
Clouds increase Sun night in response to an elongated shortwave
beginning to push toward the area from the WSW. Lows will range
from the lower 20s N, to the upper 20s to lower 30s SE. Much
colder on Mon with highs ranging from the mid to upper 30s NNW,
to the mid 40s extrm SE VA/NE NC under a cloudy sky. The
shortwave continues to move into the area under zonal flow
aloft Mon into Mon night, with a slight chance to sml chance
of light snow Mon aftn into Mon evening across cntrl/scntrl/SE
portions of the FA. PoPs increase Mon night with a 30-40% chance
for light snow across nrn portions of the FA, and chance of rain
or snow, or chance of rain across the SE third. Any accumulations
would be light with <1" of snow across NNW areas Mon night. Lows
Mon night will range from the mid to upper 20s NNW, to the lower
to mid 30s SE.
A positively tilted shortwave trough digs into the TN Valley on
Tue, before becoming neutrally tilted Tue night into Wed morning,
as it moves to the coast. This will result in sfc low pressure
tracking from just off the SE coast, NE to well off the Mid Atlc
coast by Wed morning. Details continue to change wrt the setup
but 12z trends continue to show a more suppressed system with
snow probs continuing to decline. NBM snow probs are now <50%
across the entire FA for 1" of snow. That being said, given the
180 degree shift in model guidance over the past 24 hrs, will
maintain a limited risk for snow impacts Tue into Tue night
across central VA, the Northern Neck, and the MD Eastern Shore.
Highest PoPs are Tue morning into early Tue aftn with 20-40%
PoPs W and 45-60% PoPs E. Given the more suppressed storm track,
rain over SE VA/NE NC may end as snow Tue evening into Tue night
as colder air moves farther ESE with snow the dominant p-type
across the NW half of the FA. Highs on Tue will range from the
mid to upper 30s NW, to the mid to upper 40s SE.
The arctic airmass moves in Tue night into Wed with very cold temps
expected. Lows Tue night will range from the mid teens to the
mid 20s. Wind chills will be even colder with minimum wind chills
in the single digits into the teens across much of the area
possible Tue night into Wed morning.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 355 PM EST Saturday...
Very cold and dry on Wed, with sfc high pressure building in
from the W. Becoming mostly sunny with highs only in the mid to
upper 30s. Clear or mostly clear Wed night with lows in the mid
teens to mid 20s.
Temps moderate somewhat Thu and Fri but it remains cold with highs
ranging from the upper 30s NW, to the mid to upper 40s SE. The
next trough and sfc low pressure area arrives for Fri into Fri
night, bringing the chance for rain/snow. Lows in the mid 20s to
lower 30s Thu night, and in the upper teens to upper 20s Fri
night. Sat will be very cold with highs in the lower 30s NW to
the upper 30s SE.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
As of 655 PM EST Saturday...
High pressure is building in from the W as of 00z. VFR under a
clear sky with a WSW wind of 10-15kt with gusts ~20kt. High
pressure continues to build into the region tonight with VFR
conditions continuing under a clear sky. The wind will gradually
become SW and diminish to 5-10kt, with the gustiness subsiding
by 02-03z. Breezy conditions return Sunday with a SW wind
becoming W as a secondary cold front pushes through the region.
Wind speeds will increase to 15-20kt with gusts to 25-30kt.
Mostly sunny and VFR with SCT aftn CU from RIC-SBY.
Mainly VFR Sunday night into midday Monday with increasing
clouds. Weak low pressure approaches from the SW and slides
across the area later Monday aftn through Tuesday morning. This
could bring some light snow and reduced vsby to RIC and SBY,
with lowering cigs at all sites. Another area of low pressure
organizes in vicinity of the Outer Banks later Tuesday into
Tuesday night, which could produce some light rain and snow,
primarily SE. Dry and VFR conditions return Wednesday into
Thursday as high pressure builds into the region.
&&
.MARINE...
As of 650 PM EST Saturday...
Strong low pressure has moved into southeastern Canada this
evening, and westerly winds have diminished to 20-25kt with
gusts to 30kt. The Gale Warnings for the Lower James River, Ches
Bay, and coastal waters S of Cape Charles have been converted
to SCAs that are in effect through Sunday evening. Seas are
3-6ft S/5-8ft N. Overnight, winds are expected to turn back to
the SW and diminish to 15-20kt. On Sunday, a dry front will push
through local waters, allowing for another increase in winds.
Northern coastal waters (N of Cape Charles Light) will likely
see another period of Gales starting mid- morning and lasting
until the evening as winds become westerly. Therefore, have
elected to extend the gale warnings through tomorrow evening to
accommodate the wind increase given the lull overnight will be
relatively brief. Elsewhere, expect strong SCAs with gusts
around 30kt with perhaps a few gusts to 35kt in the upper bay
during the late afternoon.
High pressure will move in Sunday night, leading to a period of
benign marine conditions through Tuesday afternoon. The next
chance for marine hazards will be Tuesday night into Wednesday
as potential low pressure passes by offshore and much colder air
moves into the region. At this time, expecting NW winds 15-20kt
during this time period. Then expecting benign conditions late
Wednesday night through Friday afternoon.
&&
.HYDROLOGY...
As of 930 PM EST Saturday...
Ongoing river flooding will continue tonight. Most of the river
sites have crested or are near crest at this time, except for
Sebrell, which is in moderate flooding and still rising this
evening, and will not crest until Monday. Matoaca has dropped
below minor flood stage this evening. Some nuisance flooding of
smaller creeks and streams is again possible given the very
saturated ground and any rainfall from last night turning into
runoff.
&&
.TIDES/COASTAL FLOODING...
As of 650 PM EST Saturday...
Have allowed the Coastal Flood Warning for Dorchester/Wicomico
to expire. No additional coastal flooding is forecast in the
next few days given the offshore winds and expected strong ebb
tides.
The Coastal Flood Advisory for Virginia Beach and Currituck
County has been allowed to expire.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until 10 PM EST Sunday for ANZ630>632-634-
656-658.
Small Craft Advisory until 4 PM EST Sunday for ANZ633.
Small Craft Advisory until 7 PM EST Sunday for ANZ635>638.
Gale Warning until 7 PM EST Sunday for ANZ650-652-654.
&&
$$
SYNOPSIS...TMG
NEAR TERM...AJZ/TMG
SHORT TERM...RMM/TMG
LONG TERM...RMM/TMG
AVIATION...AJZ
MARINE...AM/CP/ERI
HYDROLOGY...AKQ
TIDES/COASTAL FLOODING...AKQ
AREA FORECAST DISCUSSION
National Weather Service Albany NY
948 PM EST Sat Jan 13 2024
.SYNOPSIS...
Along with gusty winds, much colder air will be working
into the region behind a departing storm system. Thanks to the
colder air in place, locally heavy lake effect snow will be
developing across the Adirondacks for the rest of the weekend.
Outside of the Adirondacks, all areas will have the potential to see
some passing snow showers and squalls on Sunday due to an upper
level disturbance. It will remain cold into much of the upcoming
week, with some additional light snow possible on Tuesday.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Lake effect snow band extending into extreme northern Herkimer
and Hamilton Counties, with more isolated to scattered snow
showers/flurries into the Mohawk Valley, Lake George Saratoga
Region, southern VT and Berkshires. Gusty west to southwest
winds will continue and some breaks in the clouds outside of the
flurries/snow showers. The most breaks are and will remain in
the mid Hudson Valley and NW CT. Just minor adjustments to
clouds, temperatures and precipitation chances through tonight.
PREVIOUS DISCUSSION:
Strong area of low pressure (around 983 mb) is now located over
western Quebec and it continues to lift northeast. The large
upper level trough associated with this occluded storm system is
moving from the Great Lakes towards the Northeast, allowing for
much colder air aloft to finally move back into the region.
Some lingering rain showers are still ongoing across western New
England on the leading edge of the upper level trough, but
these should be ending shortly. Elsewhere, some snow showers are
starting to develop over the western Adirondacks, as the
combination of upslope flow, cyclonic flow and lake effect will
be allowing for periods of snow showers over the western
Adirondacks for this evening and into the overnight hours.
For much of the overnight hours, lake effect (aided by upslope
and cyclonic flow) will be aimed towards the western
Adirondacks, with a westerly flow in place. Several inches of
snow is expected by the late night hours in these most
persistent bands, mainly north of Route 28. The flow may start
to become southwesterly, allowing for the best bands of start
shifting north of the area by the late night hours. With lake
effect expected, a Winter Storm Warning will begin in effect at
4 pm this afternoon for the western Adirondacks. By the late
night hours, the southwesterly flow may break of pieces of snow
showers off the Lake Erie band and these may eventually make
their way towards the Mohawk and Schoharie Valleys, although
amounts should be fairly light with this activity.
In addition to the pressure gradient in place, the colder air
moving into the region aloft is resulting in good mixing, which
is finally allowing for some gusty winds to develop over the
area. West to southwest winds have increased, with some gusts
over 30 mph at times. These winds look to continue for this
evening and into much of the overnight hours. While it will be
rather gusty, winds should stay below advisory criteria over the
entire area through tonight. Still, these gusty winds will make
for some blowing/drifting of snow over the western Adirondacks,
adding to the hazardous conditions for that area.
Temps will be falling this evening and into tonight thanks to
westerly flow bringing some colder air into the area. Lows will
generally be in the 20s, with some upper teens over the
Adirondacks.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
On Sunday, another upper level disturbance will be making its
way across the region. CAMs (such as the 3km HRRR and NAM)
suggests that a batch of snow showers and squalls will be making
their way west to east across the area from about mid-morning
through the late-afternoon hours. Model soundings suggests it
will be fairly unstable, with the sounding showing it unstable
from the surface up through the tropopause (which will be fairly
low around 500 hpa). CAMs suggest some small amounts of SBCAPE
will be present as well, so it certainly looks like a good setup
for some squalls, which may drop a quick burst of snow, along
with low visibility and gusty winds. Will continue to message
the potential for this through our HWO, social media and DSS
packages. Although snow amounts will only be an inch or two,
there could be some travel impacts. Otherwise, temps look to
reach the upper 20s to mid 30s ahead of the squalls/snow
showers, but will be falling behind this activity. In addition,
gusty southerly winds ahead of the disturbance, will switch to
the west to southwest behind the activity and continue to be
rather windy, with some gusts up to 40 mph as well.
Lake effect will continue in the Adirondacks, although it will
briefly be disrupted by this passing disturbance. The flow will
return to being westerly for a period of Sunday night, which may
allow for another round of moderate snow accumulation for the
western Adirondacks north of Route 28. Elsewhere, it will remain
blustery and cold on Sunday night, with some passing flurries.
Temps will fall into the single digits and teens on Sunday night
and the gusty winds will make it feel even colder, with wind
chill values below zero in spots.
The lake effect will finally start to shift north of the area by
Monday morning and will be tapering off. As a result, quieter
weather is expected across our area, although it will still be a
little on the breezy side and cold, with temps only in the
teens and 20s for highs. Although there will be some breaks in
the clouds on Monday, cloud cover will increase again on Monday
night as the next system approaches, with some light snow
possible by the late night hours for southern areas. Temps will
fall into the single digits and teens once again on Monday
night.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
Long term period will feature below normal temperatures and chances
for precipitation Tuesday/Wednesday and again for the end of the
week...
Long term period begins at 12z Tuesday with a tropopause polar
vortex (TPV) lobe located in south central Canada, with a shortwave
trough expected to move over our region as it rotates around the
periphery of the upper trough associated with the TPV. At the same
time, a southern stream disturbance will be tracking off the coast
of the southeast US Tuesday afternoon and night. While previous
sources of guidance phased these two shortwaves and showed a snow
storm for portions of the northeast, we have seen a trend for
less/no phasing between these shortwaves in recent guidance due in
large part to a trend further south the with TPV and a weaker
downstream ridge over southeast Atlantic Canada. This will help to
suppress the southern stream wave further to the south. While we may
still see some light snow/snow showers with the passage of the
northern stream trough combined with enhanced moisture from the
Great Lakes, it looks like the surface low and any heavier snow will
remain well offshore to the south and east of our region. Therefore,
opted to keep PoPs capped at high chance during this timeframe. So,
for Tuesday into Wednesday, expecting daytime highs in the 20s and
overnight lows in the single digits across the high terrain to 10s
for valley areas. Some light snow accumulations of up to an inch or
so are possible for areas along and south of I-90.
Wednesday evening through Friday morning, the TPV remains stationary
near the western Great Lakes but slowly weakens. Downstream of this
feature, we will be in fast zonal flow aloft with a few embedded
shortwaves moving through the flow. These shortwaves, combined with
continued cold temperatures, will lead to chances for additional
lake effect snow across the western ADKs and perhaps northwestern
Mohawk Valley, but with high pressure sliding by to the south most
of the rest of the region should stay mainly dry. Continued daytime
highs mainly in the 20s with overnight lows in the single digits
(high terrain) to 10s (lower elevations).
For the end of the week/early next weekend, there is yet another
chance for a coastal storm system as the TPV (or a piece of it)
drops south over the Great Lakes, but confidence remains very low at
this time. While the large-scale pattern generally looks favorable
for a storm system near the east coast with a decaying negative NAO
block over the Labrador Sea and positive PNA (ridging in the west
and troughing in the east), current guidance suggests that the
trough in the east may once again be too positively tilted,
essentially suppressing any storm system well to the southeast of
our region. Will mention slight chance to chance PoPs during this
timeframe as there is still time for things to change. Temperatures
remain below normal with temperatures similar to those through from
Tuesday through Thursday.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
Lake effect scattered sprinkles/flurries/showers/snow showers
are around KALB, KGFL and KPSF and intervals will continue
through the night. There should be no reduction in visibilities
in these very light showers changing to snow showers. Ceilings
will be predominantly VFR and any ceilings that trend to MVFR
will be too brief in showers and snow showers to indicate.
Ceilings above 3000 feet will continue Sunday with VFR
visibilities. A cold front is expected to bring a chance for a
line or band of snow showers in the afternoon. So, indicating
PROB30 for MVFR ceilings and IFR visibilities between 16Z-21Z.
Winds will be west to southwest at 10 to 20 Kt with gusts 20 to
30 Kt this evening, gradually diminishing through the night.
West to southwest winds will still be gusty Sunday, but winds
around 10 Kt, gusting to around 20 Kt.
Outlook...
Sunday Night: Moderate Operational Impact. Windy With Gusts To 31 kts. NO SIG WX.
Martin Luther King Jr Day: No Operational Impact. NO SIG WX.
Monday Night: Low Operational Impact. Slight Chance of SN.
Tuesday: Moderate Operational Impact. Chance of SHSN.
Tuesday Night: No Operational Impact. NO SIG WX.
Wednesday: No Operational Impact. NO SIG WX.
Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: Low Operational Impact. Slight Chance of SHSN.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Winter Storm Warning until 7 AM EST Monday for NYZ032-033.
MA...None.
VT...None.
&&
$$
SYNOPSIS...Frugis
NEAR TERM...Frugis/NAS
SHORT TERM...Frugis
LONG TERM...Main
AVIATION...NAS
Area Forecast Discussion
National Weather Service Caribou ME
920 PM EST Sat Jan 13 2024
.SYNOPSIS...
Low pressure will exit across the Maritimes overnight through
Sunday. High pressure crosses the region Monday. Low pressure
should track east of the region Tuesday into Wednesday. Low
pressure could cross the region Thursday.
&&
.NEAR TERM /THROUGH SUNDAY/...
9:20 PM Update: Low pressure lifting across northern Maine will
track north of the state by around midnight. The low will get
absorbed into another low across central Quebec by morning.
Colder air will work into the area from the southwest in the
wake of an occluded front. Precipitation which has become more
fragmented and convective in appearance will also shift out to
the north of the FA overnight. Temperatures are still in the low
to mid 40s Downeast with just a few rain showers. From around
Caribou north the precipitation will fall as a mix of snow,
sleet, and freezing rain. Any additional accumulations are
expected to be an inch or less, and any pockets of freezing rain
will be falling on the fresh snow. Only minor tweaks to the
PoPs for the next few hours, otherwise no significant changes.
Previous discussion:
Low pressure will lift north across the region early tonight
with an occluded front. The system then exits across the
Maritimes overnight through Sunday. Expect a snow/sleet mix
across northern and central areas early tonight, which will
taper to snow showers overnight. Additional snow accumulations
across northern areas will range from 1 to 3 inches, with around
an inch or less across central areas. Across Downeast areas,
expect precipitation in the form of rain early tonight, with
partly/mostly cloudy skies overnight. A low level jet will cross
the region early tonight in advance of the occluded front with
gusty winds, strongest along the Downeast coast. An upper low
tracks northwest of the region Sunday while an upper disturbance
rotates across the forecast area along with a surface trof.
Expect mostly cloudy skies along with scattered snow showers
across the north and mountains. Across Downeast areas Sunday,
expect partly/mostly cloudy skies along with mostly afternoon
isolated/scattered snow showers. Gusty southwest winds will
occur Sunday. Temperatures will rise this evening in advance of
the occluded front. Low temperatures tonight will range from the
lower to mid 20s north, to the upper 20s Downeast. High
temperatures Sunday will range from the mid 20s to around 30
north, to the mid 30s Downeast.
&&
.SHORT TERM /SUNDAY NIGHT/...
Sfc boundary will be on the international border Sunday evening with
snow shower along it. These snow showers look to be fairly
convective with decent instability after 00z acrs the northwest,
though short range models differ on location of approaching front.
Hires cams also differ on extent of low-lvl instability with latest
HRRR indicating weak sfc low moving along the coast Sunday night
bringing an area of measurable light snow along the coast. This will
need to be watch to see if more models jump on board with solution.
For now have isolated snow showers in the evening with little
accumulating snow expected. Sunday night continues to run in the
single digits across the north to the mid-teens over Downeast and
with winds remaining fairly gusty expect that wind chill temps drop
below zero after midnight across the north, with a few locations
falling just short of wc advisory criteria.
Monday will see vertically stacked low over Hudsons Bay with
southwest flow aloft bringing upslope snow showers at time across
the North Woods. High pressure will remain over CWA thru the end of
the period though uncertainty still surrounds the incoming wave from
the southern stream and this will likely determine pops Tue
afternoon into the short term.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Significant uncertainty still exists with the track of the southern
stream moving northeast along the eastern seaboard. How far north
this wave gets likely will be determined by strength of hipres over
the N Atlantic with GFS/EC keeping it to our south or just scraping
the Downeast coast with light snow. Meanwhile NAM and Global CMC
moving it thru the southern half of the Gulf of Maine and into swrn
Nova Scotia. Have continued with hichc pops acrs the Downeast coast
Tuesday night, exiting late.
Cold pattern continues through the end of the week with quick moving
s/wvs zipping across as H5 low digs into the northeast. Temps will
remain below normal throughout the end of next week with windy
conditions bringing wind chill below zero across the north each
morning.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
NEAR TERM: IFR to MVFR overnight with conditions to improve to
MVFR at the northern terminals Sunday. Conditions at KBGR and
KBHB are expected to improve to VFR overnight. An east wind will
shift into the southwest at 10 to 20 knots with a few higher
gusts overnight and Sunday.
SHORT TERM:
Sunday night...MVFR possible over Aroostook terminals in -shsn.
SW 5- 15kts
Monday-Monday night...VFR with MVFR across the north. SSW 5-15kts.
Tuesday...IFR possible at southern terminal with VFR/MVFR elsewhere.
SE 5-10kts.
Tuesday night...MVFR/IFR possible. Lgt/variable becoming light W.
Wednesday...Mainly VFR. MVFR possible across the north. W
5-10kts.
Wednesday night-Thursday...VFR/MVFR in scattered snow showers.
WSW 5-10kts.
&&
.MARINE...
NEAR TERM: A gale warning is in effect on all the waters
through Sunday. Seas will slowly subside overnight through
Sunday.
SHORT TERM: Gales on the outer waters continue Sunday night and then
drop to SCA levels Monday morning. Seas will remain elevated into
Monday evening. Waters will be free of headlines from late Monday
night through Tuesday afternoon with winds and seas after this
time will depend on track of surface low.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...Gale Warning until 6 PM EST Sunday for ANZ050>052.
&&
$$
Near Term...CB/Norcross
Short Term...Buster
Long Term...Buster
Aviation...CB/Norcross/Buster
Marine...CB/Norcross/Buster
Area Forecast Discussion
National Weather Service Grand Rapids MI
950 PM EST Sat Jan 13 2024
LATEST UPDATE...
Update
.UPDATE...
Issued at 926 PM EST Sat Jan 13 2024
Overall no changes needed to the forecast at this time. Radar
trends confirm the formation of stronger bands of lake effect
snow. As of 930 PM, the main band stretched eastward through
central Allegan County into western Barry County and into the
Lansing area. This feature was lifting slowly north and is
forecast to stall out over portions of Ottawa, Kent and Ionia
Counties later this evening. Aleady reports have indicated an inch
per hour rates within this band. This band may strengthen further
as it continues to lift north. From SPC`s Meso Analysis page,
very strong low level convergence was depicted within this band.
That low level convergence has been shifting north with time.
Surface observations also showed this convergence. Northwest winds
up in Hart and southwest winds in Kalamazoo depict the
directional component. Speed convergence was enhancing the lift as
well with lakeshore stations showing onshore winds of 25 to 30
knots, while KBIV was only 10 knots. Another factor in all this is
the low level frontongenesis going on with KBTL showing a surface
temperatures of 15 degrees and falling, while KBIV has been
holding steady at around 24 degrees. Finally, the moist 700 mb
trough was over central WI will cross lower MI enhancing the
lift and seeding the ongoing lake effect tonight. High res models
continue to show a swath of 8 to 12 inches overnight into early
Sunday morning where the main band that is lifting north stalls
out. At this time it looks like that will occur near and/or just
north fo I-96.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 353 PM EST Sat Jan 13 2024
- I-96 convergence band setting up tonight
Winter headline adjustments were made earlier to account for the
round of heavy lake effect snow tonight into Sunday. We`re
entering a bit of a lull in snow shower intensity currently due a
brief drop in moisture depth and subsidence related to a shortwave
ridge behind the departing system.
The lull will be short-lived however as deeper moisture/lift
returns after 00Z relayed to a shortwave approaching from the west
which brings an appreciable uptick in L.E.S. intensity. H8 temps
will continue to fall with delta Ts reaching 20-25C by morning
creating moderate to extreme instability off the lake. RAP
soundings indicate moisture depth to almost 20K feet and strong
omega in the snow growth region between 3-7K Ft.
The low level flow will be backing westerly this evening and
initially as the snow perks up again the bands may favor areas
south of I-96. However with time the heavier snow showers should
lift northward to align more with the I-96 corridor as very cold
sfc air pouring in around the srn bowl of Lk MI pushes in toward
the I-94 corridor with continued backing of the low level flow in
that area.
The strong low level FGEN response and enhanced convergence later
tonight near the interface of the much warmer lake modified air
and the non-Lk MI trajectory cold air in the south is expected to
generate a zone of intense lake effect. Guidance continues to
favor the area from near MKG and BIV east across the GRR area to
near St Johns, peaking between about 10 PM and 10 AM.
While we can`t pinpoint exactly where this band is going to set
up, we think it is safe to say that a few places could see up to a
foot of new snow where it sets up and persists. Kent County has
the highest likelihood of this; we`re just not sure yet which
part(s) of the county gets it.
While snow intensity should drop off later Sunday with passage of
the shortwave, numerous snow showers will still persist into
Sunday night with additional accumulations near and west of Hwy
131.
.LONG TERM...(Monday through Saturday)
Issued at 353 PM EST Sat Jan 13 2024
- Cold and Snow
Cold and snow are the main themes of the long term forecast between
Monday and next Saturday. Upper troughing will be firmly entrenched
in the Great Lakes region for the upcoming work week with winds off
the lake. Wind flow will be somewhere between southwest and north-
northwest through the entire week. 850mb temperatures will range
from -14C to -22C through the week. With water temperatures
around +5C we are looking at delta t`s from 20C to 27C.
Instability will be in place as will moisture much of the time as
shortwaves rotate through the region. Time frames of enhanced snow
will occur Monday night, Wednesday and again late in the week
towards Friday. Periods of lake effect snow will continue right
through the next 7 days. The other theme that won`t change either
will be the cold. Monday and Tuesday look to be the coldest days
of the week with highs in the single digits in spots. So, bottom
line is cold and lake effect snow will continue. We will add to
snow totals especially for areas near and west of Highway 131.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 642 PM EST Sat Jan 13 2024
Lake effect snow bands have been on the increase since 6 pm and
they will continue to strengthen through the evening. As a result,
we moved up the timing of the sub IFR impacts. Much of the night
will feature those impacts as the bands continue to strengthen
due to the continued cold air advection and strengthening low
level convergence over that TAF sites. The strongest bands of snow
are likely to shift north of KJXN and possibly KBTL and KAZO
overnight as the wave of low pressure moves in. While lake
effect persists Sunday morning into the afternoon, the setup will
not be as favorable as tonight so we featured some improvement at
those sites. Wind gusts could still top 25 knots at the TAF
sites, especially KMKG and KJXN.
&&
.MARINE...
Issued at 353 PM EST Sat Jan 13 2024
We may be able to let the gale warning expire earlier than our 7
AM Sunday expiration given the slight diminishing trend noted in
the guidance tonight, particularly north of Holland. Small craft
advisories will be needed for the bulk of the week after the
gales subside.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until noon EST Sunday for MIZ037-038-043-
044-051-059-066-067-073-074.
Winter Storm Warning until noon EST Sunday for MIZ050-056>058-
064-065-071-072.
LM...Gale Warning until 7 AM EST Sunday for LMZ844>849.
&&
$$
UPDATE...MJS
SHORT TERM...Meade
LONG TERM...Duke
AVIATION...MJS
MARINE...Meade
Area Forecast Discussion
National Weather Service Louisville KY
921 PM EST Sat Jan 13 2024
...Forecast Update...
Issued at 910 PM EST Sat Jan 13 2024
Reinforcing cold front now bisecting Indiana, with a westerly wind
surge and a decent shield of snow behind it. Expect a quick hitting
shot of snow as the front pushes through southern Indiana and south
central Kentucky, with the best shot of up to 1 inch of accumulation
focused just either side of the Western Kentucky and Bluegrass
Parkways, where the arctic front will see its progress really slow
down. Lesser accumulations to the north, and POPs tapering off to
the south as we could be left high and dry near the Tennessee
border. Most locations that do get snow will see a half inch or
less, but with air temps solidly in the mid 20s it could be an
incovenience to Sunday morning travel, so we`ll continue to ride
with the current Special Weather Statement.
The other story overnight will be the wind, as there is a post-
frontal surge with solid 15-20 kt and gusts around 25 kt. As temps
bottom out after daybreak Sunday, look for wind chills ranging from
10 below to 20 below in southern Indiana and north central Kentucky,
while areas farther south will be a few degrees either side of zero.
Wind Chill Advisory looks to be in good shape, so no changes
planned.
.Short Term (Now through Sunday)...
Issued at 315 PM EST Sat Jan 13 2024
=====================================================================
Key Messages:
- Reinforcing shot of cold air moves into the region tonight with an
arctic frontal boundary
- A band of light snow is expected to develop along the front; light
accumulations of a coating to 1" expected
- Dangerously cold wind chills blow across the region along and
behind the front; wind chills Sunday morning as cold as -20 possible.
=====================================================================
Across the region this afternoon, visible satellite imagery shows
that much of southern Kentucky has cleared out, while areas across
northern Kentucky and southern Indiana continue to dwell under a
broken stratus deck. Temperatures currently range from the upper 20s
to around 30 across the northern CWA, with mid 30s in general across
southern KY. The most plausible explanation for the range in sky
conditions would be the influence of subtle mid-level ridging which
is creeping in from the southwest. SPC Mesoanalysis reveals a SW-NE
gradient in 850 mb temperatures, with weak warm advection likely
allowing low-level moisture to mix out above the aforementioned
regions.
As we head through the remainder of the afternoon and into the
evening hours, our attention will shift to the west where a cold
front is currently diving from NW to SE across the southern Plains
and mid-Mississippi Valley. This front is associated with a
shortwave trough that is currently diving SE from the northern
Plains and will move into the Ohio Valley later tonight. Along this
front, an area of light-to-moderate snow has persisted through the
day today and is expected to move across the OH/TN Valleys later
tonight. The main forecast question in the near and short term is
how expansive this snow band is at it crosses our region.
Working against the development of snowfall is the fact that there
is very little moisture in the atmosphere, especially above 850 mb.
However, as the mid-level trough swings through the region later
tonight, modest low-to-mid level moisture advection is expected
ahead of the trough axis, with soundings showing a 3-6 hour window
where there is saturation through much of the DGZ. Additionally, the
500 mb jet core looks to be positioned such that the OH Valley is in
the left exit region, promoting favorable conditions for broad low-
to-mid level rising motion. With this being said, it appears that
the main driver of widespread snow potential looks to be low-level
frontogenesis, which should provide mesoscale enhancement to rising
motion within the DGZ. It seems that the best 925-850 mb
frontogenesis will occur as the boundary is crossing through the
region, which may result in precipitation quickly developing just
west of or on top of the region.
The wavelength of the trough tonight is such that quick eastward
propagation is expected; thus, the surface front and precipitation
chances should quickly move off to the east by sunrise Sunday
morning. The main time window for snow would be from 9 pm EST in the
western CWA to 5 am EST in the eastern CWA. In general, snowfall
amounts between a coating and 1" are expected, even though expected
QPF is generally less than 0.05". This is thanks to high (15-20:1)
snow ratios given the arctic air mass. Locally higher totals in
excess of 1" would be possible given more robust mesoscale forcing
than currently expected. For now, will handle snow potential with an
SPS across the CWA, though a targeted Winter Wx Advisory may be
needed if high end amounts are borne out.
The potentially more impactful aspect of the front tonight is the
brutally cold wind chills expected along and behind the front as
quickly dropping temperatures combine with 15-20 mph WNW winds. Wind
chills between 0 and +20 ahead of the front will continually drop
through the mid-morning hours Sunday, with minimum wind chill values
ranging from +5 to as cold as -20. In fact, HREF probabilities of
colder than -20 wind chills are 30-40% across portions of southern
IN. The current wind chill advisory looks well placed, but may need
to be shifted slightly farther SE if the cold air is quicker to
arrive.
Sunday will be a bitterly cold air, with slow clearing expected
behind the departing front. Sunshine, most prevalent across southern
and SE Kentucky will be of little comfort, as highs should only
reach the teens and lower 20s with wind chills remaining around 0.
.Long Term (Sunday night through Friday)...
Issued at 350 PM EST Sat Jan 13 2024
==================================================================
Key Messages:
- Bitter cold arctic air through Wednesday with highs in the 20s &
10s and lows in the single digits & teens. Near to below zero wind
chill values each morning through Midweek.
- Potentially impactful and advisory level snow accumulations
starting Sunday night through Monday. With the highest chances and
possible amounts along the KY/TN border and decreasing as you go
north towards southern IN.
- Another round of accumulating snowfall Thursday night into Friday
along with another shot of colder air and highs in the 20s and lows
in the teens and single digits Friday into Saturday.
==================================================================
Bitterly cold air will remain firmly in place thanks to a strong
arctic sfc high building in over the Central Plains and Lower
Mississippi Valley through the first half of the week. This will
result in temperatures staying below freezing until Thursday. Highs
will be in the 20s and 10s with lows in the single digits to around
10 above. Wind chill values will also be near to below zero each
night and early morning with the coldest values possible Wednesday
where another wind chill advisory might be needed. With increasing
chance of accumulating snow for early in the week, the addition of a
snowpack could cause the above mentioned temperatures to be even
colder.
Storm system currently working into the Pacific Northwest today will
have its moisture and energy ejected along the peripheral of the
upper trough and into the Ohio & Tennessee Valleys Sunday night into
Monday. The aforementioned Pacific moisture will meet up with low-
level moisture coming out of the Gulf of Mexico Sunday night into
Monday. Model soundings show a nearly saturated column through the
DGZ Sunday night through the day Monday thanks to the arctic air in
place over the Ohio Valley. This set up along with spokes of mid-
level vorticity and the placement of the upper and mid-level jet
streaks will be enough lift to get widespread snow showers over the
area. While confidence remains high that we will see accumulating
snow across southern IN and central KY, it becomes significantly
lower on where the most snow will fall. The current trend in the
deterministic models of the ECMWF and GFS pushes the main snow band
further south keeping the bulk of the snow across southern TN and
northern portions of MS, AL and GA while the more hi-res models of
the NAM & HRRR keep higher amounts across central TN into southern
KY. With snow liquid ratios close to 20:1 and storm total QPF
ranging from a few hundreths of an inch north of the Parkways with
amounts as high as a quarter to a third of an inch across Lake
Cumberland it won`t take much moisture to reach advisory level snow
amounts across central KY and potentially southern IN. After talking
with surrounding forecast offices, and the lack of confidence on the
northern extend of criteria level snowfall, decided to hold off on
any issuance of an advisory at this time but could see one issued
over the next 24 hours. Feel confident an advisory will be needed at
the very least our counties along the KY/TN border into the Lake
Cumberland region.
Snow will begin to taper off Monday night into Tuesday as the arctic
high starts to work eastward. Upper ridging will begin to develop
over the Ohio Valley Wednesday night into Thursday. This will return
temperatures to above freezing for the first time this week. This
will be short lived as another storm system and upper trough dig
southward into the Ohio Valley Thursday night into Friday. While not
as cold as earlier in the week, another shot of colder air and
possible accumulating snow could be possible for this time frame.
&&
.Aviation (00Z TAF Issuance)
Issued at 625 PM EST Sat Jan 13 2024
Main impacts will be continued wind gusts, and the impacts of snow
showers associated with a reinforcing cold front moving through
late this evening and overnight.
Winds have backed to WSW and slacked off a bit ahead of a cold front
diving through the mid-Mississippi Valley. Expect MVFR stratus to
build back in anywhere that broke out, with a period of light snow
beginning late evening at HNB, by midnight at SDF, and shortly after
for LEX and BWG. Both cig and vis look to settle in MVFR, though we
can`t rule out brief IFR where the wind becomes a factor in what
technically won`t be blowing snow, but just more like sideways snow.
Only included IFR at HNB.
Winds will pick back up to a steady 15 kt with 20-25 kt gusts with
the late evening fropa, and stay up into the morning. Look for
stratus to scatter out in the early afternoon, with lighter winds
and mid-level ceilings returning by late afternoon ahead of yet
another wave.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Wind Chill Advisory from 2 AM EST /1 AM CST/ to 11 AM EST /10 AM
CST/ Sunday for KYZ023>025-030>033.
IN...Wind Chill Advisory from 2 AM EST /1 AM CST/ to 11 AM EST /10 AM
CST/ Sunday for INZ076>079-083-084-089>092.
&&
$$
Update.........RAS
Short Term.....CSG
Long Term......BTN
Aviation.......RAS
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
642 PM CST Sat Jan 13 2024
.KEY MESSAGES...
- Light snow will end this evening, with blowing snow settling
down as well.
- Temperatures plummet below zero for an extended period
tonight through Tuesday morning. Wind chills will be between
20 and 40 degrees below zero much of this time.
- We`ll have a quieter week of weather this week.
&&
.DISCUSSION...
Issued at 257 PM CST Sat Jan 13 2024
The arctic air is here. However, the core of that arctic air is out
across the Dakotas, with a fairly pronounced temperature gradient at
925mb and 850mb across west central into south central MN.
Deformation along this gradient, combined with a cloud layer located
completely within the dendritic growth zone means we have an
environment where the generation of snow is super easy and
efficient. We have been following the idea of the HRRR and NAMnest
that this band of light snow nudges east the rest of the afternoon
to about the St. Croix/MS River before sliding southeast and snowing
itself out this evening. Looking at webcams and visibility
observations, there are a good deal of 1/2 mile or less visibilities
out in western MN, so did expand the Winter Weather Advisory east to
include Alexandria down to Mankato. For now, we have this advisory
ending at 9pm tonight, though it may need to be extended depending
on how observations trend this evening. In all likelihood, had we
had a better antecedent snow pack in place, we would likely be
dealing with a blizzard today in western/southern MN. With PWATs
down around 0.1", there`s very little moisture to work with, so snow
totals today will only amount to an inch or snow or less, if you can
figure out how to measure it... Strong northwest winds means this
snow is easily getting blown around and is getting sent to Iowa,
where an 18 to 24 inch deep snowpack is waiting for it. As for snow
chances the rest of the period, we did add some small snow chances
to western WI Wednesday morning, with the GFS/Canadian showing a
strong shortwave and associated cold front possibly generating
another massive 1 inch or less snow event, with another chance for
light snow at the end of the week as the Great Lakes through begins
to pull out and upper ridging moving in from the Rockies.
Looking at temperatures, observations today have actually been
coming in a couple of degrees cooler than we were forecasting.
However, our low forecast tonight didn`t change much as cloud cover
and continued winds will keep our boundary layer mixed, meaning
we`ll have lows close to the temperatures we`re seeing in the
airmass heading our way, which is in eastern NoDak, where
temperatures this afternoon range from 5 to 15 below zero. There was
a slight eastward expansion of the Wind Chill Warning for tonight.
Originally, our wind chill headlines dropped off at noon on Sunday,
but in MN, we have extended the Wind Chill Advisory to go through
Tuesday morning, with any further warning decisions coming on a day-
to-day basis. For WI, apparent temperatures "warming" above 20 below
during the afternoons kept us from extending the Wind Chill Advisory
through Tuesday morning, though they`ll likely see wind chill
headlines for Sunday night and Monday night as well. The airmass
does start to moderate some on Wednesday with that weak cold front
coming in. Highs will at least get above zero, but will still be
running 10 to 20 degrees below normal. It`s the later half of next
weekend into the following week where a more substantial moderation
in temperatures are expected as we get back into something
resembling what has been our El Nino base state. However, given the
deep snowpack across Nebraska and Iowa into northern Kansas and
Missouri, it may take a bit more work to warm us up than it did in
December.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 640 PM CST Sat Jan 13 2024
MVFR ceilings to prevail nearly this entire duration for all TAF
sites. Scattered bands of -SN will steadily diminish this
evening, but BLSN issues may continue, especially in the open
areas of western and southern MN, resulting in degraded
visibility potentially of a longer duration than currently
advertised. Visibilities are expected to return to VFR but
daybreak Sunday, but the daylight hours with fresh light powdery
snow could again present MVFR visibilities at times. NW winds
15-20kts with gusts 25-30kts will continue through the day
tomorrow, diminishing tomorrow evening a bit.
KMSP...No additional falling snow is expected so have run with a
dry forecast for MSP. There will still be blowing snow issues
for at least the evening hours, but visibilities will prevail at
6sm or more. There still may be short-duration visibility
restrictions, maybe even some brief -SN reported, but nothing
impactful. Breezy NW winds will persist overnight through
tomorrow then diminish to closer to 10kts Sunday evening.
/OUTLOOK FOR KMSP/
Mon...MVFR ceilings possible. Wind W 10-15G25kt.
Tue...VFR. Wind W 15-20G25-35kt.
Wed...MVFR ceilings possible. Wind 10-15kt.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...Wind Chill Advisory until 9 PM CST this evening for Blue Earth-
Brown-Chippewa-Douglas-Faribault-Freeborn-Kandiyohi-Lac
Qui Parle-Martin-Nicollet-Pope-Redwood-Renville-Sibley-
Stevens-Swift-Watonwan-Yellow Medicine.
Wind Chill Advisory from noon Sunday to noon CST Tuesday for
Blue Earth-Brown-Chippewa-Douglas-Faribault-Freeborn-
Kandiyohi-Lac Qui Parle-Martin-Nicollet-Pope-Redwood-
Renville-Sibley-Stevens-Swift-Watonwan-Yellow Medicine.
Winter Weather Advisory until 9 PM CST this evening for Blue
Earth-Brown-Chippewa-Douglas-Faribault-Freeborn-Kandiyohi-
Lac Qui Parle-Martin-McLeod-Meeker-Nicollet-Pope-Redwood-
Renville-Sibley-Stearns-Stevens-Swift-Watonwan-Yellow
Medicine.
Wind Chill Warning from 9 PM this evening to noon CST Sunday
for Blue Earth-Brown-Chippewa-Douglas-Faribault-Freeborn-
Kandiyohi-Lac Qui Parle-Martin-Nicollet-Pope-Redwood-
Renville-Sibley-Stevens-Swift-Watonwan-Yellow Medicine.
Wind Chill Advisory until noon CST Tuesday for Le Sueur-McLeod-
Meeker-Stearns-Steele-Todd-Waseca.
Wind Chill Advisory from 9 PM this evening to noon CST Tuesday
for Anoka-Benton-Carver-Chisago-Dakota-Goodhue-Hennepin-
Isanti-Kanabec-Mille Lacs-Morrison-Ramsey-Rice-Scott-
Sherburne-Washington-Wright.
WI...Wind Chill Advisory from 9 PM this evening to noon CST Sunday
for Barron-Chippewa-Dunn-Eau Claire-Pepin-Pierce-Polk-
Rusk-St. Croix.
&&
$$
DISCUSSION...MPG
AVIATION...JPC
Area Forecast Discussion
National Weather Service Pendleton OR
753 PM PST Sat Jan 13 2024
.EVENING UPDATE...The biggest question with regards to this latest
round of snow the southern half of the forecast area is
experiencing this evening was just how far north the snow band
would track. Last night`s HREF was divided, with the HRRR tracking
more south and the NAMNEST tracking more north, but it appears
the more northern solutions have won out, as areas as far north as
Yakima have reported snow this evening, with the Simcoe Highlands
and parts of the WA lower Columbia Basin receiving snow as well.
Based on spotter reports and comments on social media, overall
advisories and warnings appear to be tracking well, with the
biggest uncertainty remaining for the Oregon Basin and foothills
of the Oregon Blues. We have gotten a couple of inches here at the
office - at least enough for advisory level - but reaching warning
criteria will be tight. The system`s origin may provide for
favorable upslope to produce just enough snow to reach that 4-inch
criteria. 00z HREF this evening suggests that the forecast area
will dry out by 12z, leaving cold and dry conditions for the
remainder of the weekend heading into the start of next work week.
Only a few changes were made to the forecast package. Mostly made
touch-ups on PoPs based on latest hi-res guidance. Also adjusted
overnight lows down a tad, based on latest temperatures observed
across the area. Evans/74
&&
.PREV DISCUSSION... /issued 223 PM PST Sat Jan 13 2024/
SHORT TERM...Today through Monday night...Today is the primary
day of concern with regards to the short term forecast. Wind chill
advisories continue for a large portion of the CWA as well as
Winter Storm Warnings for all zones in OR with the exception of
Wallowa. Current ground observations are showing temperatures
across the CWA to continue to be below 10 degrees with a few
isolated locations of 12-15 degrees with wind chills of -8 to -20
degrees and lower. It’s cold out there so please remain diligent
if outside. Weather.gov/safety/winter is a great resource for all
things winter related. In regards to the Winter Storm Warnings,
the precipitation has already begun along the eastern slopes of
the Cascades and has begun to move to the northeast. Ground
observations in central OR have reported 0.1-0.13 inches of
precipitation of have fallen and based off the snow liquid ratio
this equates to roughly 1.2-1.5 inches of snow. The system is
expected to continue to travel northeast bringing snow
accumulations to the lower elevations.
Models are finally coming into better agreement with the track of
the upper level low that will bring a decent amount of snow to the
majority of the CWA in OR with the exception of the Simcoe-Highlands
and high grasslands of the lower east slopes of the WA Cascades in
western Klickitat County. Winter Storm Warnings are in effect
through 4AM Sunday. The following regions have 70-90% probabilities
for the following snow amounts: OR Cascades, 2-3 feet, Blue
Mountains, 4-10 inches, John-Day Basin/Highlands, 7-15 inches,
Central OR, 5-10 inches, Eastern Gorge, 3-7 inches and lastly, OR
Columbia Basin and the foothills of the Blues, 3-5 inches of snow.
High confidence (70-90%) with the Wind chill advisories in effect
through Sunday 4AM for the Blue Mountain foothills, Central & North
Central OR, Lower Columbia Basin, Simcoe-Highlands, Wallowa County,
and the Yakima/Kittitas Valleys for temperatures reaching between
-10 to -20 degrees. Snow will continue through the overnight hours,
however will begin to tapper off in the early morning hours.
Sunday through Monday models are in firm agreement with the leading
edge of an upper level ridge will begin to push onshore keeping the
upper level winds aloft from the northwest. Some lingering snow
showers may linger across the OR Cascades as well as along the
eastern highlands due to the upslope flow and guidance shows amounts
to be up to 0.1 inches with 20-50% probabilities. As for the
temperatures through Monday, confidence is high (70-100%) that
temperatures will remain below freezing with over 60% of the raw
ensembles in agreement. Wind chill can still play a factor in the
apparent temperature so be mindful when outside during these
conditions. Please visit our website for more information regarding
winter driving preparation as well as winter weather safety at
weather.gov/safety/winter. Stay safe and warm out there!
Bennese/90
LONG TERM...Tuesday through Saturday...Sensible weather concerns
through the extended forecast will revolve around a couple of
winter weather systems that will bring moderate to heavy snow
across the area, with light snow continuing across the mountains
into next weekend.
Quiet weather conditions will continue across the forecast area
for the start of Tuesday, before a quick series of upper shortwave
troughs moves into the region. Ensemble guidance is in good
agreement that most of the forecast area will continue to be under
the influence of an arctic airmass that`s advecting into the
region, resulting in afternoon high temperatures in the upper
teens to low 30s. Late in the afternoon, shortwave energy
extending from a low in the north-central Pacific will quickly
move into the PacNW late Tuesday, followed by an upper shortwave
trough diving south out of BC early Wednesday morning. This one-
two punch of systems will result in heavy snow in the WA Cascades
and the northern Blues, with a 35-55% chance of meeting or
exceeding 10 inches of snowfall by 4pm Wednesday. Meanwhile,
ensemble guidance puts a 30-45% chance of 2 inches or greater of
snowfall by 4pm Wednesday in the lower Columbia Basin and
adjacent foothills/valleys. The shortwave trough Wednesday will
also result in breezy west southwest winds across the lower
elevations.
Late Wednesday, ensemble guidance is leaning towards a brief lull
in precipitation in the lower elevations, while most ensemble
members are showing light snow continuing across the Cascades and
into the Blues under a northwest flow aloft. This trend continues
into the early Thursday as upper level ridging offshore begins to
build into the west CONUS. By Thursday morning, a warm front
boundary under the ridge axis will again bring another round of
precipitation across the region through Friday morning. The
biggest concern with this system will be the possibility of
freezing rain developing if the warm front overrides the cold
airmass east of the Cascades. Currently, members of the GFS and
Canadian ensemble suites are showing a ~40% chance of at least 0.1
inches of freezing rain accumulations along the WA Cascade east
slopes and a less than 15% chance across the Columbia Basin and
the adjacent foothills/valleys by Friday morning. Confidence is
only low-mod (35%) at this time in the freezing rain
potential/amounts, but will continue to monitor if this trend
continues across guidance in the coming days.
Friday afternoon through Saturday ensemble guidance is in
agreement that ridge axis will continue to push east, placing the
PacNW under a southwest flow aloft. While the southwest flow aloft
is expected to bring a gradual warming trend to the region, this
will also allow a deep low in the northeast Pacific to swing
shortwave energy over the region. This will result in continued
rounds of light precipitation in the form of mountain snow and
snow to a rain/snow mix in the lower elevations (confidence
moderate or 40%). Lawhorn/82
AVIATION...00Z TAFS...A snow band gradually moving north and east
today continues to produce LIFR or lower conditions at affected
sites. A snow band will continue to gradually lift north across
OR and far southern WA today, mostly impacting sites
DLS/PDT/RDM/BDN. Site ALW is expected to see light snow after 00Z
with MVFR impacts expected. Sites YKM/PSC may see light snow
impacts this evening, however confidence in these sites seeing
impacts down to MVFR are low. The snow is expected to dissipate
around 06Z at all sites, with conditions at sites PDT/YKM/ALW/PSC
to be VFR and MVFR or less CIGS at sites DLS/RDM/BDN to persist
through tomorrow morning. Winds will be around 12kts or less
through the period. Lawhorn/82
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT -2 10 0 9 / 90 0 0 0
ALW 1 13 2 12 / 70 0 0 0
PSC 5 18 8 19 / 60 0 0 0
YKM -2 17 4 19 / 50 0 0 0
HRI 5 16 3 15 / 90 0 0 0
ELN -4 16 4 18 / 30 0 0 0
RDM -5 24 4 15 / 100 0 0 0
LGD 0 23 3 22 / 90 0 0 0
GCD 6 30 10 30 / 100 0 0 0
DLS 4 17 4 17 / 100 0 0 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Storm Warning until 4 AM PST Sunday for ORZ041-044-502-
503-505>511.
Wind Chill Advisory until 4 AM PST Sunday for ORZ044-049-050-507-
508-510-511.
Winter Weather Advisory until 4 AM PST Sunday for ORZ049.
WA...Winter Storm Warning until 4 AM PST Sunday for WAZ024.
Wind Chill Advisory until 4 AM PST Sunday for WAZ026>029-521.
Winter Weather Advisory until 4 AM PST Sunday for WAZ521.
&&
$$
SHORT TERM...74
LONG TERM....82
AVIATION...82