Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/10/24
Area Forecast Discussion
National Weather Service La Crosse WI
959 PM CST Tue Jan 9 2024
.KEY MESSAGES...
- Winter storm entering its final stages with an additional 1-3
inches of accumulation possible across our south and east
through this evening. Gusty winds and blowing/drifting
concerns will gradually subside through the evening.
- Round of widespread light snow expected Wednesday night
(80-100% probability) with potential for 1-3 inches.
- Another potent winter system likely to brush our area late
this week with snow potential for some, especially our
southeastern counties.
- Blast of Arctic air heading into Sunday and Monday with a
stretch of subzero low temperatures likely.
&&
.DISCUSSION...
Issued at 258 PM CST Tue Jan 9 2024
Ongoing winter storm in its final stages:
Radar at 1930Z continues to show the deformation band really doing
well across the southwest WI and northeast IA with many observations
near 1/4SM and winds now gusting to about 35 mph. Radar also
indicates a great cyclonic airstream advecting into the
deformation band across northern IL and southern WI from the
southeast and strong QVector convergence in the 500-300 mb layer
providing a great region of lift /per RAP/. The low center is now at
981 mb so almost a mb per hour fall today.
Latest CAMS are doing a great job helping with guidance on the
evolution of the deformation band and the western edge to the snow
today. They accurately depicted the brief lull on I-90 in WI, then
moved the deformation west again to its current location. Thus, have
timed the snow dissipation from west to east based on blend of
CAMS later this afternoon as the low center and wave pull away. This
will clear central Wisconsin in the late evening. Roads are
doing surprisingly well
with blacktop seen in many areas, probably
because temperatures are near freezing.
Snow totals of 8-11" look on track for northeast Iowa and southwest
Wisconsin. With little snowfall to drift and slightly less wind,
will cancel the Advisory for parts of southeast MN and Buffalo
county WI, and let the evening shift consider the remaining Advisory
and Warning cancellation based on conditions.
Widespread light snow Wednesday night:
With one winter system wrapping up, attention quickly shifts to the
next, which is set to impact the area from late Wednesday afternoon
through early Thursday morning. A deepening upper shortwave will
rotate out of the Plains Wednesday afternoon, with morphing into an
intensifying upper low as it crosses our area through the evening
with favorable upper divergence. This near vertically-stacked but
progressive system will also feature forcing from a modest low level
jet out ahead of the compact surface low. Now that the system is
starting to come within the window for hi-res guidance, starting to
see some hints of higher QPF potential. The 09.12Z HREF would
suggest a broad 40 to 60% probability for greater than 0.10" in our
area. Have therefore increased precipitation chances to 80-100%
across the area. There are some signals there could be deformation
banding on the system`s northern edge, which makes it difficult at
this time to pinpoint exactly where an axis of heavier QPF would set
up. Colder temperatures dropping into the 20s favor higher snow
ratios, so have nudged those toward 16:1 or slightly higher. For now
that brings snow totals into the 1-3 inch range across most of the
area, perhaps locally higher if/where any banded snow develops.
Another potent winter system late we
ek:
Thursday looks to bring a brief dry reprieve before yet another
potent winter system sets its sights somewhere in the region heading
into Friday and Saturday. Interestingly, ensemble means and
deterministic guidance show it following a similar overall track and
intensity as the present winter storm, but there are some large-
scale pattern differences, chiefly 500mb flow. Broad longwave
troughing will encompass the entire CONUS by Thursday night. The
embedded shortwave is progged to rotate through the Ohio Valley with
an intensifying surface low favored to track into the eastern Great
Lakes. Despite some evident ensemble differences in how far west or
east the system would track, it looks safe to say our area will once
again find itself on the northwest periphery. Favorable upper
divergence and dynamics will provide widespread snow chances across
the forecast area heading into Friday, once again with highest
chances (~60% per latest NBM) presently from northeast Iowa into
southwest/central Wisconsin. Snowfall probabilities will of course
depend on the track of the system. Both the 09.12Z and 09.00Z EPS
ensemble means have the surface low tracking further west into Lower
Michigan than the GEFS and CMCE, which track it over eastern Lake
Erie. As a result, snowfall probabilities for our area are presently
highest with the EPS, which shows a greater than 80% probability for
at least 3 inches in our southeastern counties compared to ~20% from
the GEFS/CMCE.
Arctic blast heading into the new week:
There may be some additional light snow chances into Saturday with a
weak disturbance, otherwise the main story heading into the weekend
will be an influx of Arctic air. A deep upper trough carves into the
western CONUS by Friday, with frigid 850mb temperatures plunging
into the nation`s midsection over the weekend. While our area looks
to lie more on the periphery of this polar airmass, we will
certainly experience a temperature plunge by Sunday and Monday when
highs look to range from the single digits above/below zero (coldest
west of the Mississippi). There will also likely be a several night
stretch of below zero lows starting Saturday night. Nothing too
atypical for the Upper Midwest by mid-January standards, but
definitely an abrupt shift from the overall mild conditions we`ve
been used to so far this winter.
&&
.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 953 PM CST Tue Jan 9 2024
CIGS: IFR/MVFR cigs will hold into Wed morning with some of the
short term guidance suggesting a few hour window where cigs could
break out into VFR (late morning/mid afternoon Wed). Confidence
remains low on timing this (if realized) while latest RAP holds the
low clouds in place. Low clouds would quickly return by Wed evening
as the next upper level shortwave trough spins across the region.
Will hold with at least MVFR for now.
WX/vsby: Next shot for -SN will come toward 00Z Thu. Expect a few
hours of IFR/MVFR vsby with the snow with perhaps a quick 1-2" of
accumulation.
WINDS: north/northwest on the decrease overnight, becoming more
westerly by 12z Wed. Weak ridge of high pressure builds in Wed,
lightening up the winds further while also swinging them southerly.
Winds will continue to shift counter-clock wise later Wed afternoon
into the evening as the ridge exits and the next snow-maker moves
in.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Warning until 3 AM CST Wednesday for WIZ044-054-
055-061.
MN...None.
IA...None.
&&
$$
DISCUSSION...Baumgardt/Kurz
AVIATION...Rieck
forecast discussion below for more details.
Previous discussion...
* A burst of accumulating snow expected for the higher elevations
during the evening commute.
Main issue for the late afternoon/evening period is a burst of
moderate to heavy snow across interior MA, especially the higher
elevations. Snow is moving into central and western New Eng this
afternoon where temps are in the upper 20s and lower 30s. Precip
will overspread eastern New Eng after 4 pm. The column is
sufficiently cold to support all snow across interior MA with a
brief period of snow possible in northern CT, northern RI into
NE MA before changing to rain. Precip will be mainly rain at the
onset across southern RI and SE MA.
Models are indicating a decent thump of snow late afternoon and
evening coinciding with the evening commute, especially over
the Berkshires and northern Worcester Hills. A brief period of
strong omega in the DGZ will support a few hours of 1"/hr
snowfall rates and this is supported with HREF/SREF probs and
there is even a low prob of brief 2"/hr rates in the Berkshires.
This will result in hazardous travel during the evening
commute, with main impact over the higher elevations. Snow will
change to rain between 7 and 10 pm from south to north across
interior MA.
Total accum into the evening before the changeover will be 1-3"
in the Worcester Hills with locally up to 4" near the NH
border. In the Berkshires, expecting accums of 2-5" with locally
up to 6" near the VT border. Across the low elevations of
interior MA, accums up to an inch is possible before it changes
to rain.
&&
.SHORT TERM /TONIGHT THROUGH THURSDAY/...
Key Points...
* Heavy rain with widespread 2-3 inches and locally 4 inches tonight
into early Wednesday leading to river and poor drainage flooding
* Strong to damaging winds late tonight and early Wed resulting in
tree damage and power outages, especially near the coast
* Minor coastal flooding during the Wed morning high tide, with
pockets of moderate flooding along the south coast
A highly anomalous multi hazard storm will impact SNE later tonight
into early Wed. A rather strong and anomalous low pres moves into
the Gt Lakes late tonight and early Wed with forecast SLP below the
minimum of the CFSR climate database. Ahead of this storm will bring
a highly anomalous wind field, PWATs and integrated water vapor
transport leading to strong winds and heavy rainfall. Did not make
any changes to the wind and flood watch headlines. Regarding the
coastal flood headlines, we upgraded to coastal flood warnings for
Narragansett Bay and the south coast and Marthas Vineyard, with
coastal flood advisories along the east coast.
Rain and flooding...
A strong signal for heavy rainfall with 3-4SD PWAT anomalies and 5-
6SD wind anomalies leading to highly anomalous integrated water
vapor transport. Strong forcing for ascent acting on this anomalous
moisture will translate to widespread heavy rainfall with peak
rainfall rates up to 0.5-0.75"/hour during the 03-09z period. May
also see a few t-storms given strong forcing and marginal elevated
instability. In fact, a fine line is possible toward daybreak along
the cold front. Heaviest rain will move to the east by daybreak as
dry slot moves in, with just a few showers during Wed as strong
shortwave moves through.
HREF probability matched mean rainfall which normally offers a
reasonable scenario indicating widespread 2-3 inches rainfall with
locally up to 4 inches across portions of RI and CT. In fact, 100
member NBM ensemble has 70-80 percent probs of greater than 3 inches
in RI.
In addition to rainfall, snowmelt will play a big role in
exacerbating any flooding as about 0.75" to 1.50" SWE exist in the
snowpack. All of this will be released south of the MA Pike adding
to the amount of water going into rivers/streams across CT/RI and
eastern MA. The biggest concern is the Pawtuxet River at Cranston
which is forecast to exceed major flood threshold with a forecast of
14.1 feet. The Blackstone river at Northbridge is forecast to reach
moderate flood with many rivers in eastern/NE MA and CT reaching
minor flood. In addition to river flooding, considerable poor
drainage and urban flooding is likely, especially in areas with snow
clogged drains.
The amount of snowmelt is less certain across interior northern and
western MA as temps will not get quite as warm as areas to the south
and initially the snow will be able to absorb a lot of the rainfall.
So while river flooding should not be a big concern across interior
northern MA, poor drainage flooding is possible given many storm
drains are still clogged by snow.
Strong winds...
Hi-res guidance is indicating 80-90 kt low level jet at 925 mb
across SE New Eng, peaking 06-10z and moving east of the Cape by
12z. This jet peaks at 5-6SD above normal and the NAEFS ensemble
mean 850 mb wind is greater than the maximum of the CFSR climate
database for this time of year. While this is a very strong signal
for strong to damaging wind, there is some uncertainty with how much
wind will mix down due to low level inversion which is usually the
case with S/SE flow. One strong signal that we normally see with
damaging S/SE wind events is anomalous low pres tracking to the west
with strong pressure falls. We certainly have this for this event.
In fact, guidance is forecasting 8-11 mb pres falls in 3 hours late
tonight which is quite impressive and this will help to enhance the
winds due to the isallobaric acceleration. Our current thinking is
peak gusts 55-65 mph near the south coast through SE MA and Cape
Ann, focused in the midnight to 6 am period. An examination of model
soundings indicate that we need to reach the mid 50s to erode
inversion enough to support these gusts. If temps only reach lower
50s, winds will probably underperform with gusts more in the 45-55
mph range. The other wildcard is all the hi-res guidance sources are
indicating some sort of fine line moving through 08-12z which will
help to enhance wind gusts. In fact, CSU machine learning severe wx
probs are indicating a low risk of severe wind. Overall, we think
this wind event will not be quite as strong as the Dec 17-18 storm
as the low level jet is a bit weaker and not as expansive.
Less wind further inland across interior northern and western MA as
snowpack will help to keep temps cooler (mainly mid/upper 40s)
keeping inversion in place. Expecting peak gusts mainly 35-45 mph
here.
Coastal flooding...
See coastal flood section below
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Highlights:
* Quiet and dry Thursday and Friday with above normal temps
* Another strong storm system with a multitude of impacts Friday
night into Saturday
* Winds remain strong Sunday with near to below normal temps
Thursday and Friday:
Rising heights Thursday night will allow for things to dry out with
some clearing skies. A moisture starved shortwave passes over the
region late Thursday into Friday which could bring a very isolated
shower or two but nothing that would accumulate. Partly cloudy to
mostly clear skies both Thursday and Friday with slightly above
normal temps in low 40s for highs.
Friday night - Saturday:
Our next weather system takes aim at the region sometime Friday
night through Saturday with eerily similar characteristics to the
system effecting the region tonight.
Another deep neutrally tilted long wave trough becomes negatively
tilted as it lifts into the Great Lakes region and into New England.
A very strong sub 980mb low will make similar track through the
Great Lakes Friday night into Saturday with strong southerly winds
and heavy rain out of head of the low. There remains some
uncertainty in the track of the low with the GFS taking a stronger
eastern track while the EURO keeps it further west and a bit weaker.
Either way, impacts from strong winds and heavy rain will be felt
with this system and details for each threat are discussed below.
Winter/Snow:
Like with tonight`s system, A front end thump of snow is possible
with this system. At most, 1-3 inches of snow is possible across the
interior high terrain before precipitation flips to all rain. Temps
during the day Friday will be above freezing in the upper 30s to low
40s which could keep all precipitation as rain if temps never drop
below freezing.
High Winds:
There is a moderate signal for strong to damaging winds again
overnight Friday and even lasting into Sunday. Another robust
southerly LLJ with 925mb winds of 60-80 knots enters the region
overnight Friday into Saturday. There remains some uncertainty in
how strong the southerly winds can get due to the track of the low.
An eastern track would result in higher southerly winds and while
the western track would mean lower southerly winds. This is
reflected in the probs for highest wind gusts showing large spread
in the ensembles and deterministic guidance. regardless, NBM probs
for gusts greater then 58mph (High Wind Warning) are already low to
moderate at 30-60% for Cape Cod and the Islands. Further inland,
Wind gusts greater then 46mph (Wind Advisory) are low to moderate at
30-60% especially for SE MA. Behind the system on Saturday night to
Sunday, winds flip around to the WSW with Cold Air Advection (CAA).
The CAA will significantly increase our mixing potential and with
925mb winds possibly near 40-50kts, advisory level winds at the
surface are possible into the day Sunday.
Heavy Rain and River flooding:
Deep moisture streaming up from the Gulf of Mexico once again
will bring PWATS back up into the 1.2-1.4 range which is 2-3
standard deviations above normal for this time of year. Early
indications from the deterministic models show a wide spread 1-2
inches across the region with localized 3"+. Ensembles are not
as robust at the moment due to spread in the individual runs.
Ensembles show less then 10% probs of 2+ inches while probs for
1" are moderate at 30- 60%. Given the rain expected with
tonight`s system, rivers and streams will likely remain much
higher then normal heading into this weekend which could
exacerbate the flooding potential.
Coastal flooding:
With another round of strong southerly winds and increasing astro
tides, coastal flooding could become an issue. Early indications
call for 2-4 feet of surge which if lined up with the highest winds
overnight Friday, could bring minor to moderate flooding for the
south facing coasts. The east facing coasts could once again have
minor flooding due to the high astro tides and significant pressure
falls as the system approaches.
Sunday:
As the system pulls away, the winds flip around the SW and the
pressure gradient remains tight. As stated above, the SW winds will
actually be causing CAA allowing for good mixing. With 925mb winds
still near 40-50 knots, advisory level winds will remain possible
into Sunday which could effect any power restoration efforts.
Temperatures will be much colder Sunday behind the system only
topping out in the low to mid 30s.
Next week:
Monday should start off dry with near to below normal temps. Another
system takes aim at the region for Tuesday or Wednesday, however
guidance remains in large disagreement this far out.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF update:
Tonight: High Confidence:
Any remaining VFR/MVFR will quickly deteriorate to IFR/LIFR this
evening. Any remaining snow will turn to rain shortly after 02z.
Winds will be very strong out of the SE gusting 40-60 knots
with 60 to 80 knots of wind shear.
Tomorrow: High Confidence:
Rapid improvement from LIFR/IFR to MVFR/VFR tomorrow morning.
Winds remain gusty out of the SW but only at 20-40 knots. Wind
shear will also improve as the core of the LLJ moves offshore.
Tomorrow night: High confidence:
VFR with decreasing winds out of the SW.
KBOS TAF...High Confidence. VFR/MVFR will quickly drop to
IFR/LIFR this evening. Heavy rain, Gusty winds as high as 50
knots, and Wind shear as high as 70 knots tonight. Rain should
quickly end after 12z tomorrow with quick improvements to
MVFR/VFR. Winds shift SW and remain gusty at 20-30kts.
KBDL TAF...High Confidence. IFR/LIFR tonight with heavy rain and
gusty SE winds. Rain come to an end by 11z with quick
improvements to MVFR/VFR. Winds remain gusty tomorrow afternoon
out of the SW.
Outlook /Thursday Night through Saturday/...
Wednesday Night: VFR. Windy with gusts up to 35 kt.
Thursday through Friday: VFR. Breezy.
Friday Night: MVFR/IFR conditions possible. Strong winds with
gusts up to 45 kt. RA, chance SN, isolated TSRA.
Saturday: MVFR/IFR conditions possible. Strong winds with gusts
up to 50 kt. RA, isolated TSRA.
Saturday Night: Mainly VFR, with local MVFR possible. Strong
winds with gusts up to 45 kt.
Sunday: VFR. Strong winds with gusts up to 45 kt.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Overall high confidence through Wed.
Storm warnings remain in effect for all waters. Winds ramping up
this evening with peak gusts 50-60 kt after midnight and diminishing
after daybreak as the low level jet moves to the east. Winds shift
to SW Wed with 30-40 kt gusts. Seas build to 20-25 ft over outer
southern waters. Heavy rain and reduced vsbys tonight with a few t-
storms late tonight, improving during Wed.
Outlook /Thursday Night through Saturday/...
Wednesday Night: Strong winds with gusts up to 45 kt. Rough
seas up to 19 ft.
Thursday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Rough seas up to 12 ft.
Thursday Night: Low risk for Small Craft Advisory winds with
local gusts up to 30 kt. Areas of rough seas.
Friday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Friday Night: Low risk for gale force winds with gusts up to
45 kt. Areas of rough seas. Chance of rain, isolated
thunderstorms.
Saturday: Moderate risk for storm force winds with gusts up to
50 kt. Rough seas up to 16 ft. Rain, isolated thunderstorms.
Saturday Night: gale force winds with gusts up to 45 kt. Rough
seas up to 17 ft. Slight chance of rain.
Sunday: gale force winds with gusts up to 45 kt. Rough seas up
to 15 ft.
&&
.TIDES/COASTAL FLOODING...
We are expecting minor to moderate coastal flooding during the Wed
morning high tide. Impressive 24-hour pressure falls exceeding 40 mb
combined with strong S/SE winds will result in a peak surge of 2-3
ft along the east coast of MA and 3-4 ft along the south coast.
However, in Narragansett Bay, potential exists for a 4-5 ft surge.
Latest forecasts indicate that the peak surge will likely precede
high tide by 2-3 hours which will help to reduce the magnitude of
flooding. However, we decided to upgrade to a coastal flood warning
for Narragansett Bay and the adjacent south coast including Westport
to New Bedford where greatest risk of moderate flooding. If peak
surge is within an hour or 2 of high tide that will likely be enough
to reach 9 ft at Providence and Fall River. Even if it falls short,
widespread minor flooding is a high confidence forecast. We are also
concerned with ocean exposed coastline as very high seas just
offshore will make the flood risk worst than the tides would
otherwise suggest. Beach erosion is also a concern.
We also upgraded to a coastal flood warning for Marthas Vineyard,
mainly for Edgartown and Vineyard Haven. A surge up to 2.5-3 ft at
high tide is forecast which would result in moderate flooding.
For the eastern MA coast, we issued a coastal flood advisory. The
flood risk is a bit less here but a 2-3 ft surge would be enough for
minor flooding, especially when adding the effects of the high seas
offshore. While winds will be shifting to SW toward high tide on the
east coast, wave energy will be directed toward the coast for
several hours preceding the high tide.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch through Wednesday afternoon for CTZ002>004.
Wind Advisory until 1 PM EST Wednesday for CTZ002>004.
MA...Flood Watch through Wednesday afternoon for MAZ002>021-026.
Wind Advisory until 1 PM EST Wednesday for MAZ002>006-008>016-
026.
Winter Weather Advisory until midnight EST tonight for MAZ002-
008.
High Wind Warning until 1 PM EST Wednesday for MAZ007-017>024.
Coastal Flood Advisory from 8 AM to noon EST Wednesday for
MAZ007-015-016-019-022-024.
Coastal Flood Warning from 5 AM to 9 AM EST Wednesday for
MAZ020.
Coastal Flood Advisory from 5 AM to 9 AM EST Wednesday for
MAZ021.
Coastal Flood Warning from 6 AM to 10 AM EST Wednesday for
MAZ023.
RI...Flood Watch through Wednesday afternoon for RIZ001>007.
Wind Advisory until 1 PM EST Wednesday for RIZ001>003.
High Wind Warning until 1 PM EST Wednesday for RIZ004>008.
Coastal Flood Warning from 5 AM to 9 AM EST Wednesday for
RIZ002-004>007.
MARINE...Storm Warning until 7 AM EST Wednesday for ANZ230.
Storm Warning until 1 PM EST Wednesday for ANZ231>237-250-251-
254>256.
&&
$$
SYNOPSIS...KJC/KP
NEAR TERM...KJC/Dooley/KP
SHORT TERM...KJC
LONG TERM...KP
AVIATION...KP/JWD
MARINE...KJC/KP
TIDES/COASTAL FLOODING...KJC
Area Forecast Discussion
National Weather Service Duluth MN
536 PM CST Tue Jan 9 2024
.KEY MESSAGES...
- Patchy freezing drizzle continues through early Wednesday
morning. Roads may become slippery.
- Widespread snow chances return Wednesday and linger through
Friday.
- Localized bands of heavy lake-effect snow may develop for
portions of the North Shore Wednesday night and for portions
of the South Shore Thursday.
- Arctic air pours into the region this weekend and into next
week. The first wind chill advisories of 2024 may be needed.
&&
.DISCUSSION...
Issued at 451 PM CST Tue Jan 9 2024
Low stratus lingers over the Northland with pockets of snow
flurries and freezing drizzle expected to persist through the
night into late Wednesday morning. Conceptual models haven`t
been helpful for forecasting freezing drizzle over the past 2
weeks. Ice accumulation reports from INL, PKD, AXN, combined
with reduced visibility and low ceilings, seems to suggest
pockets of freezing drizzle under the low stratus. Decided to
hold onto a 20% chance of freezing drizzle/snow over the
Northland through 15Z Wednesday. Northeast winds over western
Lake Superior will produce lake-effect snow showers with an
additional 1 to 3 inches of snow possible.
Attention then shifts to a complex scenario for the second half
of the week. Several fast propagating shortwave troughs will
move eastward across the central Plains while a slower-moving
virtually cutoff low will slide southeastward into the northern
Plains and Upper Midwest. Light snow is forecast to spread
eastward across northern Minnesota during the day Wednesday,
arriving over the Northland late Wednesday morning and
continuing to spread east through the afternoon. Easterly winds
over western Lake Superior will lead to enhanced snowfall over
portions of the North Shore late Wednesday afternoon through
Thursday morning. Several models are depicting a narrow
convergence band of snow which is nearly stationary. The latest
HRRR solutions point to the feature stretching from between Two
Harbors and Silver Bay southeast across the Bayfield Peninsula.
The RAP highlights an area slightly farther south, including Two
Harbors. The HiRes-ARW and FV3 shows the band closer to the
Twin Ports while the hi-res NAM solution features a broader
orographic signal from near Duluth to Tofte. In the event the
band develops and remains nearly stationary, snow amounts will
stack up quickly. There`s a potential for 6 to 12 inches of
accumulation under a potential stationary band from Wednesday
evening through early Thursday morning while the remainder of
the Northland picks up a dusting up to around 2 inches.
The northern trough will loiter over the Northland Thursday
through Friday before being absorbed into a storm system lifting
northeast across the Ohio River Valley. Winds will gradually
back northwesterly over western Lake Superior and light snow
will continue through Friday. The focus for lake-effect or lake-
enhancement will shift to northwest Wisconsin Thursday and
Friday.
Arctic air will pour into the region Friday through the weekend
with some of the coldest air of the season to-date. Air
temperatures Sunday morning will dip into the single digits and
teens below zero with wind chill values of 25 to 40 below zero.
Wind chill advisories will be needed later this week into early
next week and wind chill warnings are possible.
A large cutoff upper-level low is forecast to develop over
Hudson Bay early next week. Temperatures over the Northland will
tick slightly warmer as modified Atlantic air wraps around that
system. Expect chances of snow showers through the first half
of next week.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 533 PM CST Tue Jan 9 2024
IFR stratus with pockets of snow flurries and freezing drizzle
expected to persist through late Wednesday morning. Mentioned
light fzdzsn in TAFs with P6SM just to relay the light nature
of what is expected. KHYR has the best shot at IFR snow
visibilities. IFR chances decrease Wednesday afternoon, but
return Wednesday evening mainly for snow reducing vsbys. Winds
switching to the east, but remaining fairly light.
&&
.MARINE...
Issued at 451 PM CST Tue Jan 9 2024
Northeast winds will increase to 15 to 25 knots this evening
with gusts of 20 to 30 knots. The long fetch over western Lake
Superior will allow waves along the South Shore to build to 2 to
8 feet. The tallest waves will be found over the Outer Apostle
Islands and near Saxon Harbor. Wind speeds will diminish to 5 to
15 knots with gusts of 5 to 20 knots by late Wednesday morning.
Waves will subside below 3 feet by early afternoon. An area of
low pressure will approach Lake Superior from the west Wednesday
evening. The pressure gradient will tighten and east-northeast
winds will increase to 10 to 20 knots with gusts of 15 to 25
knots by 12 AM Thursday morning. Waves will build once again for
portions of the North and South Shore waters. Winds will
diminish and waves will subside for a time Thursday evening and
early Friday morning before strengthening and building once
again during the day Friday. Gales may develop by Friday evening
for portions of the South Shore waters, mainly from Port Wing
east through the Outer Apostle Islands. Arctic air will pour
into the region Friday through the weekend. Very cold air
temperatures will increase the risk of heavy freezing spray
Saturday through early next week.
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
MARINE...Small Craft Advisory until 8 AM CST Wednesday for LSZ140.
Small Craft Advisory until 2 AM CST Wednesday for LSZ141.
Small Craft Advisory until 2 AM CST Wednesday for LSZ145.
Small Craft Advisory until 6 AM CST Wednesday for LSZ146-147.
Small Craft Advisory until 4 PM CST Wednesday for LSZ148-150.
&&
$$
DISCUSSION...Huyck
AVIATION...Wolfe
MARINE...Huyck
Area Forecast Discussion
National Weather Service Grand Rapids MI
650 PM EST Tue Jan 9 2024
LATEST UPDATE...
Aviation
.SHORT TERM...(This evening through Wednesday)
Issued at 342 PM EST Tue Jan 9 2024
- Ongoing Winter Storm
We have extended the Winter Weather Advisory for the central 2
rows of counties in the GRR forecast area. These are the Ottawa
through Clinton row and the Muskegon through Gratiot row of
counties encompassing I-96 and M-46.
The surface low is taking a bit more of a south and east track
with regard to the GRR forecast area. It is only a slight nudge to
the southeast though as the latest RAP model still brings it up
through Lansing and Jackson. Given this track we feel ok with no
headlines over our southern two rows of counties. There is enough
of a signal that several inches of snowfall will be possible near
M-46 with tapering amounts as you head south from there towards
I-96. The snow this evening will be deformation zone snow, the
snow that is seen on the backside of winter storms. This is easily
seen in region radar loops stretching from portions of Northern
Lower Michigan southwestward into portions of Southern Wisconsin
and on into Eastern Iowa. As the low pivots to the east this band
of snow will drag across Southwest Lower Michigan. We are going to
stick close to HREF probability matched mean snowfall totals for
tonight which range from a trace to around an inch towards
I-94...1-4 inches in our central two rows of counties with the
highest towards M-46 and 3-5 / 3-6 inches across Central Lower
Michigan. The deformation zone can be seen in omega in 850-700mb
layer. The strongest lift drags across our forecast area between
7pm and 4am. RH and lift really dwindle in that layer after 4am on
Tuesday. The overnight shift will be looking into whether or not
headlines can be dropped early, but for now feel comfortable
with them stretching through the night.
- Wednesday weak lake effect
Some very marginal conditions are in place for lake effect snow on
Wednesday with delta T`s barely at 13C and RH depth decreasing to
below 5000 feet. Any lake effect snow towards Lake Michigan will
be light and inconsequential.
.LONG TERM...(Wednesday Night through Tuesday)
Issued at 342 PM EST Tue Jan 9 2024
- Clipper system Wednesday Night into Thursday -
A quick hitting clipper system will bring a burst of snowfall
Wednesday night into Thursday morning that may impact conditions for
the morning commute. Deeper saturation into the DGZ places
confidence on a mainly snow event with amounts to 1 to 3 inches
possible across the area. Highest amounts will be west of US 131 and
north of M 20. Slick and snow covered roads will be possible
Thursday morning.
- Strong System Possible Friday / Saturday -
Confidence grows on the possibility for a strong winter weather
system late Friday into Saturday morning.
An elongated North Pacific shortwave will dive southwards into the
southern plains early Friday, then will progress northwards and
become negatively tilted as it moves into the region late Friday
through Saturday morning. Some deterministic models suggest this
wave will become enclosed as it moves into the southeastern Great
Lakes Region, though there are still some discrepancies on timing
and location. At the surface, a rapidly deepening surface low that
originates in the Mississippi Valley and is favored to move through
southeastern lower Michigan / the Ohio River Valley, putting our
area in a favorable location for enhanced deformation snowfall.
The euro ensemble and deterministic seem to favor the higher snow
amounts for Lower MI, with the latest Euro ensemble highlighting
a swath from Allegan County up towards Alpena of 80+ percent
chance of snowfall amounts of 6 inches or more. Conversely, the
GFS ensemble is a bit more tame on snow amounts, highlighting
along and east of the 1-69 corridor with 50-70 percent chance of 3
inches or more snowfall. This is likely due to the fact that the
euro favors a deeper low (deterministic down to 968mb, ensemble
mean to 975mb) as well as a slightly more northerly track of the
surface low through lower Michigan. The GFS deterministic and
ensemble are a bit delayed in the progression of the deepening of
the low, and have the low tracking further south through the Ohio
Valley.
Winds will be the next piece to the puzzle in this system. Bufkit
overviews highlight the mixed layer will tap into 40 to 50 knot
gusts, while ensemble wind gusts across the Euro and GFS suggest
gusts to 35 to 45 mph. In this case the euro is on the higher end
given the deeper low.
All in all, still a few discrepancies in model output and therefore
forecast uncertainty remains. However, confidence is ever growing on
the possibility for a more significant winter weather system Friday
night into Saturday. The risk for significant impacts such as heavy
snow accumulation and significant blowing and drifting snow exists.
- Multi-Day Lake Effect and Cold Next Week -
The surface low pulls away Saturday afternoon but cold arctic air
filtering in from the northwest and perpetual upper troughing will
support lake effect snow showers through the rest of the weekend and
into next week. Highs will stay in the teens to low 20s with wind
chills down to -20F or colder at times. With multi-day lake effect
snow expected, travel impacts are expected near and west of US-131
next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 650 PM EST Tue Jan 9 2024
Widespread IFR with areas of LIFR will continue tonight. Southern
Lower Michigan will see rain this evening transition over to snow
overnight. Conditions will improve to MVFR on Wednesday morning as
the steady snow moves out. Winds will increase from the northwest
later tonight and through Wednesday with gusts over 25 knots
expected.
&&
.MARINE...
Issued at 342 PM EST Tue Jan 9 2024
We have maintained the ongoing headlines over Lake Michigan with a
Small Craft Advisory transitioning into a Gale Warning at 10pm
this evening. Winds begin to really crank up this evening as
north and northwest winds fill in behind the low. As the current
winter storm moves off to our east this evening and tonight we
should see north-northwest gales develop quickly between 11pm and
2am. Winds in the mixed layer would suggest gales to 45 knots are
possible from roughly about 1am and 9am or so. Waves should peak
in the 10-15 foot range. Remember we have two SPOT buoys still in
the water, one at mid lake and one off shore of Muskegon. The data
can be accessed on the NDBC website. Currently as of 230pm waves
range from around 1 foot with the off shore wind at Muskegon and
nearly 7 feet at mid lake. After gales subside Wednesday morning
we will need to transition into another Small Craft Advisory which
will likely persist through the day on Thursday.
The next system to watch will be out in the Friday night and
Saturday time frame as a very strong winter storms looks to impact
the Great Lakes region. Gales will be likely and storm force winds
are certainly in the realm of possibilities as well. Our somewhat
conservative winds at that range in the forecast are already
producing 15 footers at mid lake Friday night into Saturday.
Suffice it to say we have entered an active and hazardous period
on Lake Michigan. Freezing spray will become a concern as well as
we get beyond the Fri/Sat system.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 10 AM EST Wednesday for MIZ037>040-
043>046.
Winter Weather Advisory until 7 AM EST Wednesday for MIZ050>052-
056>059.
LM...Small Craft Advisory until 10 PM EST this evening for LMZ844>849.
Gale Warning from 10 PM this evening to 10 AM EST Wednesday for
LMZ844>849.
&&
$$
SHORT TERM...Duke
LONG TERM...Thielke
AVIATION...Ostuno
MARINE...Duke
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
627 PM CST Tue Jan 9 2024
.KEY MESSAGES...
- Snow returns to the region Wednesday afternoon and evening,
with a couple inches of accumulation possible during the
evening commute. Slick travel is possible!
- Accumulating snow possible this weekend, as a major winter
storm barrels through the Great Lakes. The most significant
impacts will likely stay to the southeast of Minnesota/western
Wisconsin.
- Coldest air of the season will bring sub-zero high
temperatures and dangerous wind chills by the end of the
weekend.
&&
.DISCUSSION...
Issued at 216 PM CST Tue Jan 9 2024
System snow has all but ended across south central Minnesota and
western Wisconsin, thus the Winter Weather Advisory was allowed to
expire as scheduled. GOES satellite imagery shows widespread low
stratus across the region, which in true Winter fashion will
continue to be the theme over the coming days. Surface observations
in western Minnesota have noted reductions in visibility from
lingering flurries, though little to no additional accumulation is
expected in these areas today.
Quiet weather is expected overnight, as Minnesota and western
Wisconsin sit between the headline storm system over the Great Lakes
and the next incoming wave, which aims to bring snow showers to the
area tomorrow afternoon and evening. Starting with the setup aloft,
guidance swings a 500mb shortwave trough through central Iowa
Wednesday afternoon. At the surface, low pressure will move to the
east out of Nebraska by midday, followed by a progression to the
northeast within a region of warm air advection. Precipitation is
forecast to develop northwest of the surface low, where the latest
QPF output from WPC ranges from a few hundredths northwest of the
Twin Cities, to almost a tenth of an inch in the Twin Cities Metro
and locations to the southeast. Further sounding analysis reveals an
environment that will be supportive of "greater-than-climatology"
snow ratios (~13:1), due to a deeply saturated DGZ and light winds.
Putting the pieces together, it would appear that ratios will run
closer to say 18:1/20:1 by Wednesday evening, when the greatest
period of accumulating snow is expected. Snowfall totals of 1-2"
will be possible across southeastern Minnesota and western
Wisconsin, with up to an inch possible north and west of the Twin
Cities Metro. The highest PoPs move across the I-35 by early
evening, which will likely make for a slick evening commute.
A lull in the active weather will return for Thursday, before the
active weather pattern swings another major storm system towards the
Great Lakes region Friday into Saturday. Not much has changed with
the expected track of the winter storm, as the Grand Ensemble
continues to illustrate a blended track from southern Illinois
through eastern Michigan, with the greatest travel impacts from
wind/snow to the southeast of Minnesota/western Wisconsin (closer to
places like Chicagoland). With that said, the magnitude of lift
associated with this storm system will likely result in an expanded
precipitation shield that may extend into the Upper Midwest. NBM
blended guidance features chance PoPs for snow Friday and Saturday,
along with a likely increase in surface gusts. It`s too soon to say
just how much snow may fall, however the 12z guidance is trending
more favorably towards accumulating snow across the region to close
the work week and open the weekend.
The coldest air of the season will arrive on the backside of the
storm system, as a polar air mass dives south. A multi-day period of
bitter cold will begin Saturday morning and persist into the start
of next week. Saturday highs in the single digits will be followed
up by a reinforcing shot of dangerous cold for Sunday. NBM highs
appeared to be too warm through the weekend, so we opted to lean
with the 50th-percentile NBM. The end result drops highs into the
single digits below zero Sunday and Monday. An early look at
apparent temperatures shows the potential for advisory level wind
chills for an extended period early next week. NBM temperatures warm
a touch, back into he teens by the middle of next week.
It`s been awhile since temperatures dropped below zero at MSP, in
fact you have to go back to the morning of February 24, 2023 to find
a sub-zero reading. The morning low was -8 that day.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 556 PM CST Tue Jan 9 2024
Main concern tonight is what happens along the west edge of the
stratus deck over western MN. Right now, it has IFR cigs, but
the HRRR/LAV and several other models show dense fog forming
along the western edge of the stratus deck. We went this route
at AXN/RWF, but the one thing that may prevent fog from forming
are the high clouds from our next snow maker already moving into
western MN. As for that snow, we went admittedly aggressive
with pushing snow across the area. With that said, confidence is
high on seeing snow, but there some lower confidence with
potential timing, with us favoring the faster HRRR/RAP timing.
Wanted to get the idea going of snow impacting the MPX terminals
on Wednesday, with fine-tuning of timing/vis details with
future TAFs.
KMSP...With IFR cigs expanding to the west of MSP, did bring IFR
cigs into MSP for tonight into Wednesday morning. Still quite a
bit of spread on potential snow start at MSP, with the HRRR
starting it at 18z and the NAM not until nearly 00z. At the end
of the day, confidence is high it will snow Wednesday afternoon into
Wednesday evening, so wanted to get snow in the TAF, though
further refinements in the timing and vis impacts will be needed
over the next couple of sets of TAFs.
/OUTLOOK FOR KMSP/
Thu...MVFR cigs likely. Wind NW 10-15 kts.
Fri...MVFR likely. Chc IFR/-SN late. Wind N 10-15G25 kts.
Sat...MVFR likely. Chc IFR/-SN. Wind NW 15G25 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
DISCUSSION...Strus
AVIATION...MPG
Area Forecast Discussion
National Weather Service Reno NV
115 PM PST Tue Jan 9 2024
.SYNOPSIS...
A winter storm will bring widespread wind and then snow impacts
to the region through tomorrow. Cold temperatures Thursday will
moderate slowly ahead of another storm Saturday, which could
result in additional snow and travel disruptions for the
mountains. The storm door remains open next week, but no clear
signals yet for large storms.
&&
.DISCUSSION...
* We`re seeing consistent signals in the latest high resolution
models (e.g. FV3/HRRR/HREF) which helps increase confidence in
wind and snow impacts through tomorrow. "Best guess" snow totals
have increased roughly 30-50% from previous forecast.
* Widespread strong and gusty W/NW winds are expected through
Wednesday as a pair of reinforcing cold fronts push southward
through the Great Basin. Solid wind advisory type scenario with
gusts 35-50 MPH, with localized damaging winds in wind-prone
areas such as Washoe Valley, 395 in Mono Co, and 95 along Walker
Lake. Lower valleys will lessen tonight, but wind-prone areas
and ridges should remain breezy all night.
* High-res models showing pronounced banded nature to snowfall
coming in waves tomorrow, with peak snowfall rates in the
afternoon and evening. With instability present there`s good
potential for 1"/hour rates in valleys and 2-3"/hour rates in
the mountains. Coupled with cold temps and winds, this will make
for rough travel conditions including the evening commute.
* Don`t be surprised to see us issue a rare Snow Squall Warning at
some point tomorrow once we see these features on radar. There`s
non trivial potential for over-performing snow (e.g. 6"+) in W
Nevada as HRRR showing those snow bands training/stalling for a
few hours. Example: NBM 60% odds of 6" & 10% of 10" at Carson
City.
* If you can hunker down or remote work tomorrow afternoon and
Thursday morning, it might not be a bad idea... Poor travel
conditions likely Thursday with cold post-storm temps keeping
many roads icy, so expect continued delays with Thursday morning
commute. A break in the weather is expected Thursday & Friday
for most areas.
* Good confidence in seeing another Pacific storm Saturday into
early Sunday, maybe as early as Friday night. This one has a
little warmer trajectory with NBM showing potential for
rain/snow mix even up to 6000`. Can`t rule out some freezing
rain in sheltered valleys. That being said, there`s still
appreciable variability in precip from dry to wet scenarios,
especially in Mammoth/E Sierra where many simulations show the
storm falling apart as it settles south. Breezy but not seeing
big wind signals at this point, even at 90th percentiles.
* Into next week, just seeing noisy 10-30% precip probabilities
much of the week, so no real defined big storm signals this far
out. Wait & see. Slow moderation in temperatures is projected.
-Chris
&&
.AVIATION...
Suffice it to say we`re looking at a rough couple of days for
flying via wind, turbulence, mountain waves, and snow squalls.
* Widespread strong and gusty winds are expected through Wednesday
as a pair of reinforcing cold fronts push southward through the
Great Basin. Solid bet for westerly gusts 30-40 knots today at
most airfields with potential for 40-45 knots Wednesday
especially from CXP/MEV south to MMH/HTH. Latest HREF showing
highest- feasible gusts (90th percentile) at MMH today around 45
knots, but 65 knots tomorrow. LLWS will be a factor overnight as
valleys see winds lighten a bit while mountain top flow varies
between 30-55 knots.
* Snow impacts will ramp up during the morning Wednesday becoming
more acute in the afternoon-evening. Latest HREF/HRRR/FV3
showing banded snow along secondary cold front, with good
potential for periods of 1"/hour snowfall rates for valleys
including RNO and 2-3"/hour in mountains including TRK/TVL.
Flight categories will be highly variable, from periods of VFR
to IFR/LIFR in short order. Latest NBM showing 13% chance of 4"
at RNO, jumping to 74% at CXP/MEV and points south/east
including HTH at 35%. So runway accumulations are highly likely.
-Chris
&&
.AVALANCHE...
* Winter storm with a pair of cold fronts moving into the Sierra
with widespread strong winds and heavy snow, with snow totals
trending up in latest high-res simulations which is reflected in
the forecast.
* In terms of SWE this is a modest storm, with roughly 0.5-1" east
side of Tahoe, 1-2" on west side of Tahoe near crest, and
0.75-1.5" along the crest in Mono County. Not much help to the
snowpack/water supply.
* Cold air will make snow ratios higher than a typical storm in
the Sierra, running roughly 16-18:1. This snow will be prone to
big time blowing and drifting due to strong winds. Snowfall
rates of 2-3" per hour are a good bet due to convective/unstable
nature of the precipitation Wednesday afternoon-evening.
Thundersnow with lightning cannot be ruled out in the mountains.
* West/northwest winds are projected to gust 80-110 MPH on the
Sierra ridges through early Thursday morning, with most valleys
30-45 MPH for gusts. Might see a little dropoff in winds both
ridges/valleys tonight as mountain top flow slows in between
cold fronts.
-Chris
&&
.REV Watches/Warnings/Advisories...
NV...Wind Advisory until 4 AM PST Wednesday NVZ003-005.
Winter Weather Advisory from 4 AM to 10 PM PST Wednesday
NVZ001-003>005.
Lake Wind Advisory until 4 AM PST Wednesday NVZ002.
Winter Storm Warning from 4 AM Wednesday to 1 AM PST Thursday
NVZ002.
Lake Wind Advisory until 9 PM PST this evening NVZ004.
CA...Wind Advisory until 4 AM PST Wednesday CAZ070-071.
Winter Weather Advisory from 4 AM to 10 PM PST Wednesday
CAZ070-071.
Lake Wind Advisory until 4 AM PST Wednesday CAZ072.
Winter Storm Warning from 4 AM Wednesday to 1 AM PST Thursday
CAZ072.
Winter Weather Advisory from 10 AM Wednesday to 4 AM PST
Thursday CAZ073.
&&
$$