Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/18/25
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
502 PM AKST Fri Jan 17 2025
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
The primary weather focus through the short term remains the slow
progression of the frontal system and a series of shortwave
troughs and the evolution of a potential low development along
this boundary. Model guidance has trended toward slower
progression of the front into Southcentral Alaska, with broad
support for a developing low near Prince William Sound (PWS) or
eastern Kenai Peninsula Sunday into Monday. This slower evolution
increases confidence in prolonged precipitation along the coastal
areas but introduces significant uncertainty in the timing,
intensity, and inland penetration of precipitation and associated
impacts.
Strong easterly to southeasterly winds this afternoon,
particularly along the Anchorage Hillside and Turnagain Arm, are
expected to persist as a coastal ridge remains along the coast.
While the HRRR (and previously the NAM nest) depicts stronger
winds reaching lower further into Anchorage, other guidance (GFS,
NAM) suggests the pressure gradient will reorient down Cook Inlet
as the low forms. Coastal areas, including Seward and Whittier,
will see steady precipitation as the front lingers offshore.
Precipitation rates will likely increase through Sunday as the low
deepens. Inland areas will remain marginally cold enough for
snow, particularly in locations like Portage through Turnagain
Pass, where low-level thicknesses and temperatures support snow
through the events early stages. Portage could see several inches
of snow by Sunday evening, though warm air advection will
gradually erode the cold air, introducing the potential for
rain/snow mix or a changeover to rain. However, downslope effects
along the coastal mountains will continue to limit inland
precipitation, with areas like Anchorage and the Mat Valley
remaining largely dry through much of Saturday. Winds will also
strengthen to near storm-force in the northern Gulf as the front
progresses northward by Sunday morning.
As the trough becomes negatively tilted and the low develops,
precipitation will begin to overspread inland areas late Sunday
into Monday in the Mat-Su Valley, and potentially into the
Anchorage Bowl as well. However, timing discrepancies remain
notable among model guidance. For Anchorage, snowfall remains
uncertain as surface temperatures hover near freezing. Minor snow
accumulations are possible late Sunday into Monday. Marginal
temperatures could lead to variability depending on the timing and
intensity of the precipitation. Valdez will see snow early on
Sunday but will warm with increasing south to southeasterly flow,
with significant snowfall expected for Thompson Pass into Monday.
Overall, the exact timing and strength of the developing low in
the Gulf remain variable across models. The extent of inland
precipitation is tied to how quickly the trough progresses and the
intensity of the cross-barrier flow.
Eovino
&&
.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (Friday to Sunday)...
A trough traversing northward across the Eastern Aleutians this
afternoon will continue the gusty southerly winds present in
Alaska Peninsula (AKPEN) bays and passes through tonight.
Locations such Cold Bay and False Pass could see gusts up to 60
mph tonight before a gradual decline through tomorrow. As the low
pressure system moves north, the Southwest coast will see enhanced
southeasterly flow, prompting a Coastal Flood Advisory for the
Kuskokwim Delta Coast through tomorrow afternoon. The highest
threat is especially for the communities of Kwigillingok and
Kongiganak, where the timing of the strongest onshore winds
coincide with high tide.
Moderate to heavy precipitation is likely for the higher
elevations of the AKPEN and Wood River mountains while lighter
more showery precip is possible for much of the rest of Southwest.
Another low crossing the AKPEN tomorrow night will help a
resurgence of weather for the Bristol Bay region.
On Sunday morning a North Pacific low will send its front across
the Western Aleutians. There is some model disagreement about
exact track, but it is looking like multiple shortwaves will
rotate around the low center, bringing enhanced winds and
precipitation to the Aleutian chain as it moves east, making it to
the southern end of the AKPEN sometime Monday morning.
&&
.LONG TERM FORECAST (Days 4 through 7: Tuesday through Friday)...
The high amplitude weather pattern over Alaska for the past few
days will become more energetic as a number of upper level
shortwaves rotate across the region through the forecast period.
Stormy weather continues through Friday across the Southern
portions of Alaska. An elongated Bering trough reorients across
Mainland Alaska, briefly eroding the the downstream ridge before
continuing into Canada. Additional energy from transient North
Pacific low add to the movement. The ridge reestablishes itself
over the Interior as another trough deepens across the Bering for
Thursday, but back-to-back lows continue through the windflow. The
ECMWF and the EC mean solutions are preferred to cover both
synoptic features and the uncertainty with the finer details.
Some lingering areas of rain occur across the Southcentral coasts
with gusty winds over the Gulf of Alaska. The next low brings
locally moderate rains or rain and snow mixed and gusty winds from
the Central Aleutians to Kodiak Island and Kamishak Bay into
Southwest Alaska Tuesday. Locally heavy rain or rain and snow
mixed spreads Eastward along the Eastern Kenai Peninsula into
Prince William Sound Wednesday, and continuing to the Canadian
Border through Thursday before diminishing. In the West, a well
developed low and front bring heavy rain and gusty winds to the
Western Aleutians Tuesday. This system marches over the Aleutians
and Bering, spreading into Southwest Alaska, Northern AKPEN and
Kodiak Island for Friday
&&.AVIATION...
PANC...Light north to northwesterly winds at the surface with
southeasterly winds of 30-40 kt at or above 1500 ft will
contribute to continued low-level wind shear through Saturday.
Ceilings remain VFR with only a low chance for ceilings to lower
below 5000 ft at times.
&&
$$
Area Forecast Discussion
National Weather Service Binghamton NY
1005 PM EST Fri Jan 17 2025
.SYNOPSIS...
Partly to mostly cloudy and not as cold tonight. A gusty breeze
will develop around the Finger Lakes region. The dry conditions
will be brief as the next storm system brings a mix of rain and
snow to the area Saturday. A chance of snow Sunday will be
followed by very cold Arctic air that settles in through the
first half of next week.
&&
.NEAR TERM /THROUGH SATURDAY NIGHT/...
1000 PM Update..
Southerly winds are increasing and an area of mid level clouds
is streaming into CNY at this time. Bumped overnight lows up a
few degrees, especially in the Syracuse metro area, where
temperatures are currently rising through the mid-30s. Touched
up PoPs, weather type, QPF and snow amounts for Saturday; but
overall the latest data was still on track with the forecast,
and any snow amounts will be low and slushy during the day
Saturday, as highs reach well into the 30s areawide.
00z guidance is starting to come in for the Sunday/Sunday night
system. The 00z HRRR continues with a more westward track,
spreading steady snow back well west/NW of Binghamton. The 21z
RAP is also in-line with, if not even further NW than the 00z
HRRR. The 00z NAM remains further south and east with the low
and steady snow area (compared to the HRRR and RAP). Still
awaiting the 00z CMC-regional, GFS, ECMWF and other guidance.
640 PM Update...
Low stratus is clearing out with the strengthening SW flow this
evening. With winds increasing through the boundary layer the
temperatures should hold pretty steady or slightly increase
across higher elevations despite the clear skies with the warm
air advection.
350 PM Update...
Dry conditions will be in place across the area tonight with
weak high pressure building in at the surface and ridging aloft.
Clouds continue to linger around the area, but are expected to
give way to some clearing this evening before thickening back up
again prior to daybreak tomorrow. Southwesterly winds are
expected to increase tonight with wind gusts of 25 to 30 mph
possible, especially around the Finger Lakes region and higher
terrain south of the I-90 corridor. With SW flow in place it
won`t be quite as cold tonight with low temperatures in the low
and mid 20s for most. Areas immediately around Finger Lakes
will be in the upper 20s to near 30 degrees.
The break from precipitation will be brief as high pressure
slides off to the east early tomorrow morning giving way to a
shortwave trough and surface cold front. Showers, mainly in the
form of snow initially push into the area from the south and
west during the mid to late morning hours, then transition to
elevation dependent rain and snow through the remainder of the
day. Model guidance and the high res CAMS do support there being
a dry slot developing across portions of NE PA and the
Catskills during the afternoon, so PoPs generally top out around
50% in this area tomorrow vs. likely (>60%) elsewhere. The
mixed precipitation is expected to change back over to all snow
showers tomorrow evening before tapering off. Snowfall amounts
tomorrow through tomorrow night are expected to be light on the
order of a coating to around an inch, with the exception being
northern Oneida County where two to three inches is possible as
precipitation looks to stay mainly in the form of snow combined
with a little lake enhancement during the afternoon. High
temperatures are expected to be in the low to mid 30s with upper
30s in some valley locations.
Winds shift back around to the northwest tomorrow night and it
will turn colder again with lows mainly in the teens. The
southern Catskills and portions of NE PA drop back into the
lower 20s.
&&
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
430 PM Update...
Accumulating snow may occur for much of the area as a second
wave of low pressure passes during the second half of the
weekend, especially towards the Poconos and Catskills where an
Winter Storm Watch has been issued.
Models have been trending towards a likelihood of snow for a
good chunk of the area Sunday midday through evening, though
there is still a good deal of uncertainty for how far west the
heavier snow potential could reach. Before the associated wave
of low pressure, cold air will already have advected into the
region, which will allow all new precipitation to be in the
form of snow; generally of a dry and fluffy texture. Highs will
e mostly 20s Sunday, to perhaps around 30 in the lower reaches
of the Delaware-Susquehanna valleys; yet even there as soon as
the snow starts temperatures will fall.
The right entrance region of the northern stream jet maximum
will have some overlap with the left exit region of the southern
stream jet with the surface low. This will cause a period of
forced ascent including the dendritic growth layer for a period
of steady snow, peaking mid afternoon through evening Sunday
when snowfall rates could reach or perhaps slightly exceed 1
inch per hour. For locations that get squarely under the
heaviest snow, 6-9 inches could easily occur. This is most
probable in the Poconos-Catskills, and thus the Winter Storm
Watch. There does appear to be an upper bound of what is
possible, because the system moves rather briskly; there is only
so much that can occur in that timeframe. Even the reasonable
worst case values, that is with a 10 percent chance of
occurring, are still under a foot. Monitor the forecast for
updates, because slight shifts in the storm track could relocate
the axis of heavier snow. Even outside of the heavier snow,
there should be a sizable area that receives at least a plowable
snow.
Snow heads out later Sunday night, and temperatures will plummet
into the single digits-lower teens by dawn. That will be just
the start of the Arctic Blast headed our way.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
430 PM Update...
Bitterly cold arctic air will impact the region through at least
the first of half of next week. There will also be some
potential for lake effect snow and/or snow squalls on Monday.
This is likely to be the coldest air we have seen in the last
couple of winters.
Low level flow will be mostly westerly and lake effect from
Lake Erie may push far enough eastward to impact the Twin Tiers
for a short time. Some of the snow showers could take the form
of mini-squalls Monday, though actual additional snow
accumulations should be on the low side as temperatures are
almost too cold and outside the Dendritic Growth Zone. Also,
there will be very little moisture available after Monday
afternoon. That said, temperatures will be very cold which may
limit the effectiveness of snow treatments on roads.
Forecast confidence is very high that the coldest air thus far
this season will occur Monday night through Wednesday.
Temperatures are forecast to dip well below zero overnight with
lows dipping below zero and only single digit to to low teens
for highs each day Monday through Wednesday. When incorporating
the winds, apparent temperature values of 15 to 25 below zero
look very achievable through the overnight hours. Widespread
Cold Weather Advisories, at the very least, can be anticipated.
Some moderation in temperatures is anticipated for Thursday-
Friday, but it will still be below freezing.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions are expected through at least 12Z for all
terminals tonight. An increasing low level jet will lead to some
LLWS at most terminals that have winds fall below 10 mph. BGM
and SYR look to stay windy at the surface so the LLWS was not
added.
Tomorrow, precipitation moves in from the west. At first, enough
cold air in place will support mostly snow so around 16Z to 21Z
there is a chance at IFR or worse vis from snowfall at all
terminals. As temperatures warm, snow chances to mostly rain
with improved vis by the late afternoon. Cigs fall as better
moisture moves in through the day with IFR cigs at most
terminals by the evening.
Outlook...
Saturday afternoon...A mix of rain and snow and associated
restrictions.
Saturday night...A mix of rain and snow showers changing back to
all snow with restrictions possible.
Sunday...Some snow and associated restrictions possible.
Monday through Wednesday...Lake effect snow showers and
associated restrictions possible, especially for KSYR-KRME.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...Winter Storm Watch from Sunday morning through late Sunday
night for PAZ040-044-047-048-072.
NY...Winter Storm Watch from Sunday morning through late Sunday
night for NYZ062.
&&
$$
SYNOPSIS...DK/MDP
NEAR TERM...AJG/DK/MJM
SHORT TERM...MDP
LONG TERM...MDP
AVIATION...DK/JTC
Area Forecast Discussion
National Weather Service Charleston SC
1038 PM EST Fri Jan 17 2025
.SYNOPSIS...
High pressure will prevail through the rest of the week. An
area of low pressure and associated cold front will impact the
region this weekend. Another low pressure system could impact
the region early to mid next week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Just like the past few nights, temperatures are the biggest
challenge overnight. Late Friday temperatures ranged from 33F
near Huger to 51F on Tybee Island. Temperatures will cool a bit
more early tonight, before cloud cover thickens from the west in
advance of a 175+ kt upper jet moving through the Deep South,
and some mid level energy out ahead of it. Actual lows will
occur early tonight in the upper 30s and lower 40s most places,
except for some lower and middle 30s in Berkeley County an
parts of northern Charleston and northern Dorchester. A few
places closer to the ocean will only drop to the mid 40s.
It`ll take some time for the lower levels to moisten up, so we
feel that any rainfall will stay offshore near a coastal trough
and upstream to the west in advance of better dynamics.
Visibility early Friday evening was reported down to 1 1/4
miles at KMHP, and KSAV has shown smoke in its observation for
several hours (but with no reduction in visibility). The HRRR
and RAP do have smoke persisting to some degree overnight, but
does not show any reductions in visibility. For now we prefer
not to include smoke in the forecast, but be advised that a few
places still might have minor reductions in visibility due to
smoke from the fires.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
Saturday and Sunday: Saturday will be a wet day across
Southeast South Carolina and Southeast Georgia ahead of cold
front. Model vertical cross sections show strong forcing induced
by a series of embedded southern stream shortwaves passing
through juxtaposed with deep moisture with mean RH values >90%
throughout the column. This should result in a large area of
light to moderate rain moving steadily east across the Deep
South, which is on target to push west- east across the local
area during the day Saturday. HREF pops for QPF >0.01" remain
near 100% and the forecast will continue to reflect categorical
pops with the highest pops focused on the morning hours.
Elevated rain chances will persist into Saturday night into
Sunday as anther surge of shortwave energy passes through ahead
of the arctic cold front. A drier trend should occur Sunday
afternoon as the front pushes offshore and colder, drier air
begins to advect into the region. High will warm into the 58-65
degree range Saturday (warmest south of I-16) with lower-mid 60s
Sunday before FROPA. Lows Sunday morning will drop into the
upper 40s/lower 50s. It will begin to get a bit breezy mid-late
afternoon Sunday with the onset of post-frontal cold air
advection.
Sunday Night and Monday: Both periods look to remain dry as
arctic high pressure builds into the region. Highs will only
reach the lower 40s for many areas Monday afternoon with lows
Sunday night dropping into the mid 20s inland to upper 20s
closer to coast. Enhanced northwest winds will help push wind
chills into the 15-20 degree range, which is solidly in Cold
Weather Advisory criteria.
Lake Winds: Breezy conditions will develop on Lake Moultrie
late Sunday afternoon as a cold front pushes through. Strong
post-frontal cold air advection will push winds into the 15-20
kt range with gusts 25-30 kt Sunday night and a Lake Wind
Advisory could be needed during this time. Speeds should below
advisory criteria by mid-morning Monday.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
The forecast is starting to narrow in on a wetter and colder
solution for the upcoming mid-week winter event as arctic high
pressure settles in. All of the operational runs of the GFS, EC
and CMC are starting to align with support from many of their
accompanying ensemble members. This coupled with trends noted in
the NBM is finally allowing for some increased confidence in
how the event will unfold as low pressure passes by to the south
and offshore. There remains some uncertainty on how the p-types
will evolve as the event progresses, but it is becoming
increasingly favorable for a snow/freezing rain event which
could bring impacts, possibly significant, to Southeast South
Carolina and Southeast Georgia. Complicating matters is there
are signals that enhanced forcing induced by bands of mid-level
frontogenesis could yield corridors of enhanced precipitation
rates, which could result in pockets of moderate to locally
heavy precipitation. How much of this enhancement will occur is
yet to be determined and can not be readily identified this far
out. This is certainly something to watch as these bands could
augment both p-types, precipitation rates and accumulations. It
is still too far out to identity any specific snow/ice
accumulations and impacts this far out, but the probabilities
for both accumulating snow and ice are increasing and the
forecast will reflect this trend. Timing for the period of
greatest impacts looks to center on the Tuesday afternoon to
early Wednesday period when the coldest air will align with the
strongest forcing and heaviest precipitation. Some light
precipitation could reach parts of the Georgia coast before
daybreak Monday with precipitation ending Wednesday morning.
In addition to winter weather, bitterly cold temperatures will
occur. Temperatures are trending colder with highs mid-week
poised to stay in the 30s both Tuesday and Wednesday afternoons.
Lows Tuesday night will drop into the lower-mid 20s with upper
teens/lower 20s Wednesday night. Wind chills will drop 15-20
Monday night, 8-15 Tuesday night and just a tad warmer for
Wednesday night. A Cold Weather Advisory will likely be needed
during this time and there is even a chance for some areas to
reach Extreme Cold Warning criteria (10 or colder), especially
Tuesday and Wednesday nights.
Another area of low pressure could develop off the South
Carolina coast Thursday into Friday. With temperatures still
quite cold, a brief period of freezing rain could occur, mainly
Thursday morning and again early Friday morning with the best
chances across the interior.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
KCHS/KJZI/KSAV: VFR will prevail at all sites tonight, although
there could be a little smoke at time impacting KSAV due to
nearby wildfires/brushfires. At the moment no visibility
restrictions have been included in the latest forecast. Light
to moderate rains will develop in advance of energy aloft on
Saturday, most numerous during the late morning through mid
afternoon (15Z-21Z). These will be accompanied by lowering
ceilings, and perhaps brief MVFR visibilities. But the better
chances for MVFR or IFR conditions will occur late Saturday when
the atmosphere becomes fully saturated.
Extended Aviation Outlook: Flight restrictions are likely
Saturday evening into Sunday morning as widespread rains move
through in association with a cold front. The risk for
restrictions in low vsbys and ceilings will return Tuesday
morning into Wednesday morning as a potential winter storm
impacts the region. There is an increasing chance for freezing
or frozen precipitation to impact all terminals during this time
period.
&&
.MARINE...
Overnight: A weak pressure pattern will exist between a subtle
inverted trough nearby, and a frontal system stretching from
Hudson Bay in Canada, through the Great Lakes, continuing to
Texas and parts of the Gulf Coast states. This will result in
winds that are variable in direction at 5 or 10 kt, with limited
seas of just 1 or 2 feet. Showers are expected to develop as we
draw closer to daybreak across the local waters.
Saturday through Wednesday: Gusty southwest winds will prevail
Saturday into Sunday ahead of a cold front. Gusts will be close
to Small Craft Advisory criteria a times. Advisory conditions
are more likely Sunday night as strong cold air advection
spreads over the waters behind a cold front. Stronger winds are
expected Tuesday into Wednesday as the pressure gradient
tightens between inland high pressure and low pressure passing
well offshore. Northerly winds could reach as high as 25-30 kt
at times with periods of gale force gusts. Small Craft
Advisories are likely with a possibility for a Gale
Watch/Warning. Seas look to peak early Wednesday morning, 5-8 ft
nearshore waters out 20 NM and 9-14 ft over the Georgia
offshore waters out 20-60 NM. Finally, mariners should be alert
that some winter precipitation could fall over the coastal
waters Monday night into Wednesday morning, reducing vsby to 1
NM or less at times.
&&
.CLIMATE...
Record Low Temperatures:
Thursday, January 23:
KCHS: 19/1985
KCXM: 24/2003
KSAV: 19/1960
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
652 PM EST Fri Jan 17 2025
.KEY MESSAGES...
- Widespread rain/snow to snow expected tonight into Saturday
morning. Snow accumulation totals of a half-inch up to 2 inches
likely, with higher-end amounts possible within the Irish Hills.
- The coldest temperatures of the winter thus far arrive early next
week. Dangerous wind chills of -15 to -25 likely for the morning
hours, with little relief for the afternoon, centered Monday through
Wednesday.
&&
.AVIATION...
Dry and milder conditions through the evening hours, as a modest
gusty southerly winds persists. Sufficient magnitude to southerly
flow at 2000 ft to maintain a mention of low level wind shear during
this time. Plume of deeper moisture will arrive after 06z tonight,
resulting in a steady increase in precipitation potential through
Saturday morning with an accompanying reduction in both ceiling and
visibility. The milder temperatures at onset will support primarily
rain initially, with a transition toward a rain/snow mix and then
straight snow from northwest to southeast as precipitation rates
increase. This will afford a window of IFR conditions, with a brief
period of LIFR possible. Passage of an arctic front will bring a wind
shift to northwest by early afternoon, with a rapid decline in
coverage of snow. Cold northwest flow with some gustiness and
lingering MVFR stratus through the remainder of daylight period.
DTW THRESHOLD PROBABILITIES...
* Low for ceiling aob 5000 feet this evening. High after 06Z
tonight through Saturday.
* Medium for a precipitation type of rain and melting snow at
onset after 06z tonight. High for all snow post front late
tonight into Saturday morning.
* Low for crosswind threshold exceedence Saturday afternoon.
&&
.PREV DISCUSSION...
Issued at 348 PM EST Fri Jan 17 2025
DISCUSSION...
Shortwave ridge axis passed to our east this morning opening the
door for gusty southwesterly winds around the broad surface high
pressure centered over the eastern conus. Gusts to 30 knots have
helped usher a fairly warm airmass into the region this afternoon,
and aided by peaks of sun, has resulted in temps into the upper 30s
across southeast MI. This warm air will be short lived as a strong
low tracking through southern Canada tonight will open the door for
long duration cold air advection with multiple surges of arctic air
through the region as the longwave trough stalls and digs down to
the Gulf into the midweek period. This will be one of the coldest
airmasses we`ve experienced in the last few years.
For tonight, the low pressure system will pass through Ontario
tonight, pulling an arctic cold front through SE MI Saturday
morning. As this northern stream trough digs southward through the
MS Valley it will partially phase with the southern stream and a
shortwave tracking through OK/MO. A strong low level jet ahead of
the deepening trough will peak around 60 knots tonight over southern
MI and is already closing in on 40 knots helping to generate the
gusts this afternoon. This will also bring a surge of moisture up
into the area just ahead of the arctic front resulting in several
hours of precipitation tonight into Saturday morning. Models have
been fairly consistent with around 0.25 inches of QPF, but the ptype
will be an issue with this event. Starting off near 40 this evening,
with temps above 32F up through 6kft will offer the initial ptype
issue with too much warm air at onset around midnight. So first few
hours will be rain or a rain snow mix working south to north through
the region. Warm layer gradually cools through the night with
sounding favoring colder profiles after about 5am which would offer
more snow, or melting snow, for much of the area especially the
higher terrain of the Irish Hills. Lower terrain from Monroe County
up through Wayne and into Macomb are expected to hold the warm air
longer. Temps most of the night will reside in the low to mid 30s
also helping to reduce snow accumulation. NAM is definitely one of
the colder models which isn`t surprising with HRRR and RAP coming in
much warmer, keeping rain almost through 12Z Sat. So with such a
fine line between rain and snow in these scenarios, will hold with a
mainly 1-2 inch forecast for a portion of the area with 3 inches not
out of the questions if the cold air can surge in faster and mainly
for the Irish Hills. With warm temperatures holding at the surface,
any accumulation will likely be minimized on paved surfaces that are
wet to start and warm at transition. So higher accumulations
expected on grass or elevated surfaces.
With the arctic front sweeping across Saturday morning, the moisture
and warm air will all get shunted east with cold air advection
kicking in. Some lingering light snow in the morning will be
possible until the front finally passes but drier air will end that
by noon. Warmest temps will be early in the morning with temps then
falling through the day. After increasing to around +4C Friday
evening, 850mb temps will fall to around -4C by Saturday morning and
-10C by evening. After falling further to around -20C by Sunday
afternoon, ECMWF suggests -25C is in play for Monday with the
coldest airmass sweeping through Tuesday close to -30C. Expect a
long duration cold outbreak with temperatures holding below 20F from
Saturday night through Wednesday night with highs on Tuesday and
Wednesday in the single digits. Wind chill values will fall into the
negative range Sunday night and will remain below zero through
Wednesday night. At this time they look to bottom out in the -10 to -
20F range which will need to be watched as we refine things. Looks
likely that we will need a Cold Weather Advisory for a period this
week at a minimum.
MARINE...
A strong low pressure system tracking north of Lake Superior is
setting up a corridor of strong southerly winds over the central
Great Lakes this afternoon. These winds reach a peak in magnitude
this evening with gusts of 35 to 40 knots over central/southern Lake
Huron. A Gale Warning remains in effect there through tonight.
Elsewhere, winds will be mainly in the 20 to 30 knot range. Gales
will taper off early Saturday morning as the system`s cold front
slides through. This will be followed by northwest winds picking up
as cold advection ensues. These peak between 20 and 30 knots
Saturday afternoon but remain active through the weekend as frigid
arctic air works into the region. Intervals of lake effect snow
showers and freezing spray can be expected over Lake Huron Sunday
through Wednesday.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Warning until 4 AM EST Saturday for LHZ362-363-421-441-462>464.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....MR
DISCUSSION...DRK
MARINE.......TF
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Marquette MI
530 PM EST Fri Jan 17 2025
.KEY MESSAGES...
- Blustery southerly winds continue this afternoon, turning to
the NW tonight behind a passing cold front. Wind gusts up to
40-50 mph will be possible across the Keweenaw tonight.
- Lake effect snow develops across the NW wind snow belts
tonight, with 1-3 in of snow accumulations by the morning.
Gusty winds may lead to blowing snow and reduced visibility.
- Dangerously cold arctic air settles into the area this weekend
into early next week, leading to temperatures remaining
subzero from Saturday night through at least Tuesday morning
over interior western Upper Michigan. Much of the rest of west
and central Upper Michigan may see temperatures fail to rise
above zero on Monday and maybe Tuesday.
- Homeowners and property managers should take action now for
this cold period, especially if past very cold periods have
yielded impacts. Ensure your Winter Car Survival Kit is up-to-
date. This weekend through Tuesday, limit time outdoors for
you and your pets, and check on vulnerable neighbors.
- Frequent whiteouts are expected in the northwest wind snow
belts Saturday through Tuesday morning due to the falling snow
being a fine, powdery type snow that is highly effective at
reducing visibility. Expect very hazardous driving conditions in
the lake effect snow areas.
- No widespread, significant snowfalls for Upper MI through next week.
Nearly all of the snow that occurs will be lake effect driven.
&&
.SHORT TERM /THROUGH SATURDAY/...
Issued at 331 PM EST Fri Jan 17 2025
RAP analysis and water vapor imagery reveal a clipper shortwave
skirting along the Minnesota/Ontario border into northern Lake
Superior with a 986mb sfc low pressure analyzed just north of Lake
Nipigon. Despite fairly active radar returns this afternoon across
portions of the south-central and east UP, very little precip has
made it to the ground thanks to a dry low level air mass. Will note
an uptick in radar returns in central Wisconsin, however with dry
air still hanging around confidence is low that any precip spreading
into the central UP will amount to anything at all aside from some
flurries.
The main forecast concern heading into tonight and Saturday is the
strong cold front currently barreling through north-central
Minnesota. With its passage across the UP this evening, winds will
back out of the northwest, ushering in cold arctic air and starting a
prolonged period of much below normal temperatures and lake effect
snow. Rapid pressure rises ~6-9mb/3hr behind the cold front across
western Lake Superior will accelerate northwest winds upwards of 40
to 50 mph tonight in the Keweenaw, thus, have opted to continue the
upcoming Wind Advisory for northern Houghton and Keweenaw counties.
Coinciding the winds, strong CAA aloft brings in 850mb temps near -
17C east and -21C west by Saturday morning, upticking lake effect
snow in the northwest snowbelts.
Snowfall amounts will be tricky to nail considering a few factors
working against efficient snow growth. With decreasing temps through
the early morning hours, there will only be a ~6 hour period of
solid lift through the DGZ before it ends up below the surface. Once
the DGZ falls below the surface, snow crystal habit will change to a
fine powdery type of snow that is tough to accumulate, but can
drastically reduce visibility at times. Strong northwest winds
during that period will work to fracture dendrites as they fall,
lowering SLRs further lessening snow accumulation at the surface.
Incoming arctic high pressure through Saturday will work to lower
lake induced inversion heights. All of this is to say that snow
amounts in the NW snow belts will be 2" or less per 6 hours through
Saturday, where totals amounts of 2-5" are possible, mainly in
terrain enhanced portions of the Keweenaw and in Alger/Luce counties
under the strongest convergent bands. Elsewhere, 1-2" or less is
expected where LES bands wobble about.
Otherwise, look for surface temperatures to begin their decent as
arctic air filters in through the weekend. Lows will drop tonight to
the single digits across the interior / teens near the lakeshores
and barely climb any higher for Saturday`s expected highs.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Issued at 323 PM EST Fri Jan 17 2025
The long term forecast starts us out with a large scale surge of
Arctic air continuing to cycle into the eastern 2/3rds of the CONUS
as displayed by the excellent agreement between the differing medium
range model suites and guidances. This plunge of polar air will be
caused by the building ridge over the northeast Pacific into Alaska
and beyond, causing significant troughing to develop over the
eastern 2/3rds of the CONUS this weekend through early next week
downstream of it. Guidance still brings 850mb temps as cold as -30C
over the U.P. late this weekend through early next week. Although
the coldest shot of air looks to miss us to our west (most likely
due to some latent heat release from Lake Superior), this will still
be supportive of high temperatures struggling to even get to 0F over
the interior west and most of the central U.P. Sunday through
Tuesday. Highs could even struggle to get above -10F in the cold
spots, particularly Monday and Tuesday when the core of the cold air
is projected to move overhead. While winds aren`t expected to be all
that strong late this weekend through early next week, with west to
northwest flow continuing throughout the first half of the extended
period, we could see wind chills drop down to the -20 to possibly
even -40F range, as the low temperatures in the coldest spots could
drop down to -30F or lower early next week. Therefore, cold weather
advisories have been issued for the conditions Saturday night
through Monday; we could see some upgrades to Extreme Cold Warnings
across much of the area Monday night/Tuesday morning, particularly
over Gogebic and Iron counties where wind chills below -35F are
expected; hypothermia and frostbite will set-in within 30 minutes or
less in these conditions, possibly even within 10 minutes or less
Monday night/Tuesday morning in the coldest spots. During this cold
spell, remember the "4 Ps": people, pets, plants, and pipes (the "4
Ps" are courtesy of Meteorologist Chanelle Stigger from WFO Lake
Charles). Make sure to not expose yourself to the outdoor conditions
for long/more than you absolutely have to. Limit your pets` time
outside these next few days. Put your plants in warm environments.
And if you live on a property that has a history of pipes freezing,
be sure to run the faucet to prevent ice buildup. Temperatures will
finally begin to climb back towards normal by the middle of next
week ahead of a Clipper diving down across the Canadian Prairies.
As for the precipitation expected from Saturday night through early
next week, expect the west to northwest flow to keep lake effect
snow showers going across the west to northwest wind snow belts
throughout the first half of the extended period. With temperatures
within the boundary layer being mainly outside of the DGZ (too
cold), expect the sand-like/sector-plated snow to be near a 10:1
SLR. While snowfall accumulations aren`t looking to be that
impressive due to the low PWATs in the polar air, we could see
visibilities significantly reduced in some of the snow showers down
to 1/2 mile or less, especially near the Lake Superior shoreline
where patchy blowing snow is possible and behind vehicles where
localized whiteout conditions are possible due to cars `kicking up`
the snowfall from the roadways. While snowfall amounts may not reach
Winter Weather Advisory criteria, some of these may be issued in the
future to account for the significantly lowered visibilities. In
addition, some stronger snowfall rates could be seen across the
eastern U.P. as medium range model guidance shows a remnant surface
low forming over the eastern lake, creating localized convergence
for the snow bands. In addition to the increased latent heat release
due to the longer fetch over Lake Superior, we could see moderate to
possibly even heavy snowfall at times (LREF showing 2 inches per 6
hour snowfall rates having up to a 20% chance); it will be
interesting to see if we get more dendrites to form in the stronger
bands over the east due to the increased latent heat flux and thus
warmer temperatures/longer time in the DGZ; should this occur, we
may see much higher SLR snow over the east and thus higher snowfall
rates/snow totals. As surface high pressure drops from the Northern
Plains into the Ohio River Valley early to mid next week, expect the
winds to become more westerly Tuesday to southwesterly by Wednesday;
this looks to kick the lake effect snowfall out of the U.P. into the
open lake by Wednesday as warm air advection moves in.
As we move into next Wednesday and onwards, expect temperatures
closer to normal as warm air advection moves into the Upper Midwest
ahead of a Clipper low running through the Canadian Prairies before
arriving over the Upper Midwest Wednesday/Wednesday night. This
Clipper may bring another round of light snow showers to the area,
but expect accumulations to not be much more than a dusting. While
we may see some lake effect snow showers behind it, we could see a
shortwave ridge move through late next week before another shortwave
low possibly brings additional light snow showers to begin next
weekend. Overall, expect the troughing pattern to remain through the
end of the period, keeping mainly normal to below normal
temperatures across our area; no notable system snowfall expected to
impact the U.P. through next week.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 530 PM EST Fri Jan 17 2025
VFR will continue into this evening. Deteriorating conditions are
expected through the evening and overnight hours as a cold front
currently trekking through north-central Minnesota presses into the
UP tonight. As this front crosses the lake near 00-03z, lake effect
snow in the northwest wind snowbelts will begin to uptick, thus,
bringing MVFR conditions at IWD and CMX tonight and then IFR
conditions Sat morning. SAW may not see any snow given the
unfavorable wind direction. Strong northwest winds upwards of 25-35
knots are expected behind the cold front, particularly at CMX where
gusts to 45 knots are not out of the question. Blowing snow could
cause visibility issues at all sites as snow crystal habit is
expected to change from snowflakes to a finer powder type into
Saturday afternoon, further reducing visibility at times.
&&
.MARINE...
Issued at 323 PM EST Fri Jan 17 2025
Southwest gales to 35 knots over the east and west gales to 40 knots
over the west this afternoon become northwest gales up to 45 knots
over the central and eastern lake tonight behind the cold front of a
Clipper lifting towards James Bay. As much colder air cycles over
the lake tonight through to early next week, expect heavy freezing
spray across much of the lake, even though the winds will slacken
this weekend to northwest winds of 20 to 25 knots by Sunday. The
gusty northwest winds look to continue until Tuesday, when a surface
high digging through the Northern Plains into the Ohio River Valley
shifts winds to the west Tuesday and the southwest Wednesday.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Wind Advisory until 3 AM EST Saturday for MIZ001-003.
Cold Weather Advisory from 10 PM EST /9 PM CST/ Saturday to 10
PM EST /9 PM CST/ Monday for MIZ001-003-009-010.
Cold Weather Advisory from 10 PM EST /9 PM CST/ Sunday to 10
PM EST /9 PM CST/ Monday for MIZ002-004>006-011>014-084-
085.
Lake Superior...
Gale Warning until 1 PM EST /noon CST/ Saturday for LSZ162-
240>248-263-264.
Heavy Freezing Spray Warning from 1 AM EST /midnight CST/
Saturday to 1 PM EST /noon CST/ Sunday for LSZ162-240>242-
263.
Heavy Freezing Spray Warning from 1 AM Saturday to 7 PM EST
Monday for LSZ243>251-264>267.
Gale Warning until 7 PM EST Saturday for LSZ249>251-265>267.
Lake Michigan...
Gale Warning until 7 PM EST this evening for LMZ221-248-250.
&&
$$
SHORT TERM...BW
LONG TERM...TAP
AVIATION...07
MARINE...TAP