Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/26/24
Area Forecast Discussion
National Weather Service La Crosse WI
529 PM CST Mon Nov 25 2024
.KEY MESSAGES...
- No travel impacts are forecast in the local area through the
week at this time. Some flurries or light snow showers may
occur from time to time this week.
- A cold morning Tuesday with wind chills in the single digits
to teens. Bundle the kids up for the morning school bus.
- An unusually cold period is coming up for late week with wind
chill values generally not getting above 10-15F Friday through
Monday.
&&
.DISCUSSION...
Issued at 242 PM CST Mon Nov 25 2024
Cold Overnight, Monitoring for Light Snow Chances Late Tuesday
A dreary day should come to an end over the next several hours as an
upper-level shortwave trough continues through the region this
afternoon and evening. The precipitation from this morning
associated with a 700-600hPa frontogenetic band has moved east of
our area this afternoon as high pressure currently located across
the central plains moves east into the region. Subsidence and drier
air associated with the high have begun to move into the area which
will allow for clearing skies from west to east this afternoon and
evening. Areas along and north of I-94 remain cloudy overnight
though as the drier low-level air remains farther south.
Otherwise, overnight temperatures drop into the low 20s to upper
teens as cold air advection takes over. Stronger winds mixing
to the surface given the cold air advection should drop apparent
temperatures into the single digits to low teens by Tuesday
morning with the 25.12z HREF suggesting a 60% probability of
apparent temperatures < 10F across much of the area.
Later in the afternoon tomorrow and into tomorrow night, warm
advection in the lower levels in southerly flow provides some lift
across northeast IA into northern IL, suggested by many of the
deterministic models. The 25.15Z RAP continues like its
previous version of suggesting the most aggressive mid-level
/~600-700mb/ frontogenesis signal as winds back to w-swrly ahead
of the Rockies shortwave trough. This trough is currently seen
in GOES water vapor imagery at 20Z as a subtle trough over
Reno, NV. This provides a bit deeper ascent across southwest WI
and northeast IA for some light snow in the RAP...but also is
the stronger and further north outlier. Comparing the 25.12Z
HRRR in that area, forecast soundings in the lowest levels are
still quite dry. There is good consensus in the HREF members on
a west->east reflectivity suggestion from NE->IL with various
intensities and coverages, and mainly south of the forecast
area. This is left as a target to monitor moving forward...no
action was taken to add it to the forecast as it is a low
probability at this point (10-15%).
Wednesday into Thursday night: Quiet Weather Expected
This period begins the transition to a deepening longwave trough and
much colder air over the east CONUS into next week. Forecast models
continue to converge and maintain the highest precipitation
chances south of the local area and central IL is still
suggested by the ECMWF ensemble system for accumulating snow.
The local area will be under northwest flow with passing shortwave
troughs Wednesday afternoon and eve...and Thursday night. Model
guidance on these shortwaves suggests some Qvector convergence
in the 500-300mb layer and weak tropospheric vertical motion
under weak cold advection in the low levels. Some light snow
showers or flurries probably will occur but no impact is
expected. Will leave out precipitation chances in the forecast
for now with 25.00Z Grand Ensemble guidance in the 10-15%
range, with the idea that we probably will add in some flurries.
Friday into Monday: Unusual But Not Record Cold
Confidence continues to be high (90%+) in a noticeable cool down
later in the week and for the weekend. The area will be under
prolonged northwest flow with low-level temperature anomalies in the
2.5 range per Grand Ensemble forecasts...which suggests unusual but
not record cold. Predictability seems good with the 25.00Z Grand
Ensemble having only about a 4-5F range in the Max Temp 25-75th
percentile Fri-Sun. Temperatures will remain fairly consistent
during the period with lows in the 0 10F range and highs in the
18-25F range across the area. Record low temperatures for
Rochester and La Crosse are in the 10 to 20 below zero range
during the period (unattainable). Impact: The wind speeds
remain above 10 mph in a semi-static surface pressure gradient
meaning wind chills will be lower...bottoming out in the 0 to
-10F range, with afternoon maxes in the single digits to lower
teens across the area. That will be a jolt.
The only other weather we are monitoring is a northwest flow system
which looks like it will track through Iowa and may brush northeast
Iowa with light precipitation later Friday night and early Saturday.
Both the 25.12Z EC ens and GEFS indicate a 50-60% chance for 1" of
snow across central and southwest IA. The 25.00Z Grand Ensemble
probabilities for very light precipitation (snow) are about 20%
for northeast IA with a stable forecast trend. The forecast is
currently dry for that period.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 529 PM CST Mon Nov 25 2024
Surface ridge will build into the Upper Mississippi River Valley
through the taf period. Subsidence and a dry airmass will erode the
low level stratus deck of clouds east of the Mississippi River this
evening. This will allow for VFR conditions at both RST/LSE taf
sites through the taf period. Gradient slackens during the day
Tuesday...wind speeds will diminish to less than 10 knots by 18z
Tuesday.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...Baumgardt
AVIATION...DTJ
Area Forecast Discussion
National Weather Service Bismarck ND
948 PM CST Mon Nov 25 2024
.KEY MESSAGES...
- Below normal temperatures are expected this week. The coldest
period is expected to be Friday through Sunday, when morning
wind chills may approach 35 below zero in some areas.
- A clipper system will bring light accumulating snow (an inch
or two) to much of northwest and central North Dakota Tuesday
afternoon through Wednesday. Little or no snow accumulation is
currently expected in southwest North Dakota during this
timeframe.
- Another weak clipper may bring some very light snow
accumulations to the area Wednesday night into Thanksgiving
Day, and will usher in very cold temperatures that last
through the weekend.
&&
.UPDATE...
Issued at 946 PM CST Mon Nov 25 2024
Lake-effect flurries continue along and to the south and east
of Lake Sakakawea late this evening. 850 mb winds are forecast
to weaken and turn more westerly overnight, and lower-level
winds should become light and variable. It is therefore unlikely
that the lake-effect flurries will persist much beyond midnight
CST.
All other aspects of the near-term forecast remain on track. 00Z
guidance maintains a general one to two inches of snow with the
shortwave traversing the region Tuesday afternoon through
Tuesday night, but steep lapse rates through and above the DGZ
could promote some isolated pockets of enhanced snowfall rates.
UPDATE
Issued at 636 PM CST Mon Nov 25 2024
Satellite continues to show lake effect clouds/flurries
streaming southeast off of Lake Sakakawea. Boundary layer winds
are forecast to weaken later this evening, but a mention of
scattered flurries was added to the forecast through 9 PM CST.
Guidance is also hinting at fog formation later tonight into
Tuesday morning, primarily along the surface ridge axis from
northwest to north central North Dakota. Confidence on areal
coverage and whether this would be manifest as fog, ice
crystals, low stratus, or a combination thereof is low. But
there is enough of a signal to add a mention of patchy fog to
the forecast with this update.
&&
.DISCUSSION...
Issued at 1242 PM CST Mon Nov 25 2024
Cold temperatures and light snow will be the main forecast
issues through Thanksgiving week.
We start of pretty quiet. It remains cold today, especially in
the north where temperatures are remaining in the single digits
above zero. There are some lake effect clouds coming off of Lake
Sakakawea we but do not expect them to impact Bismarck as winds
will diminish this evening and shift to the southeast overnight.
It will be a cold night tonight with lows possibly in the -5 to
around -10 degree range along the International Border. Farther
south, lows will be mainly zero to 10 above over central and
southern portions of the forecast area.
Tuesday will also start out cold and quiet, but a clipper system
will move into the northwest in the afternoon. The associated
shortwave is currently spinning over southwest Alberta and will
track into the area Tuesday. There is some modest synoptic
scale forcing with this wave that progresses southeast across
the forecast area Tuesday afternoon through Tuesday night. FG
forcing is strongest in the southwest at 850 mb and in the north
central at 700 mb so this would suggest that at least some
modest FG forcing across northwest and central ND. Lapse rates
are high across the area Tuesday afternoon and evening as well.
Would think there would be some potential for some banded
precipitation but given the progressive nature of the system and
the relative lack of sustained overlap of strong FG and
synoptic scale forcing, the impacts from banded precip look to
be minimal at this time. There is currently no banded precip
noted from the HREF or the HRRR on the WPC snowband probability
tracker. Our NBM guidance is producing an area of generally 1-2
inches of snow across northwest and north central ND and into
the Northern James River Valley.
The NBM probabilities are producing a 40 to 80 percent
probability of greater than an inch of snow from eastern
portions of Williams county east through Rugby in Pierce county,
and north to the Canadian Border, but tapers as you go east of
Bottineau County. The southern edge also tapers quickly south
of Mountrail, Ward and McHenry counties. This is a 24 hour
probability ending at 18Z Wednesday. These probabilities drop
to around 20 percent from Bismarck to Carrington. Probabilities
of an inch or more are less than 10 percent south of a line
from Grassy Butte to Glen Ullin and Linton. Probabilities of at
least 2 inches of snow for the same timeframe are highest from
around Stanley to Minot AFB to Towner (around 50 percent). Winds
with this system are light as the snow is falling, but do pick
up a bit on Wednesday on the back side of the system, although
the winds are strongest south of the snowfall so impacts from
blowing snow on Wednesday appear minimal at this time.
Another weak wave comes through on Wednesday Night into
Thanksgiving day. This is mainly just a lull between High
pressure and Arctic high pressure. We could see some light snow
or flurries though on the leading edge of this chunk of Arctic
air dropping south. This will usher in a period of very cold
temperatures from late Thanksgiving night, through the Holiday
weekend. Wind chills during the overnight and early morning
hours will probably end up being cold enough for Cold Weather
Highlights over a good portion of the northern and eastern
forecast area Friday morning and again on Saturday and Sunday
mornings. At this time it looks like it will probably warm up
enough each day that one continuous Advisory is probably not
justified. We`ll have to see though how this plays out as we get
closer to the weekend. There may be another weak impulse or two
through the weekend that brings a brief period of light snow or
flurries, but other than the inch or two for parts of the area
Tuesday into Wednesday, any additional snows look to be of
little to no impact.
Beyond the weekend there are signals that we will see at least a
modest warm-up early next week. The NBM ensemble temperatures
indicate a definite warm-up as early as Sunday and into the
middle of next week, but ensemble spreads are quite large (in
the 10 to 15 degree range) for both low and high temperatures. A
look at a cluster analysis shows varying degrees of ridging
building over the area with a current 60/40 favoring of more
ridging than troughing over the forecast area early next week.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 946 PM CST Mon Nov 25 2024
VFR conditions are mostly expected through this forecast, but
there are a few possible exceptions. There is a low chance of
fog and/or low stratus developing across parts of northern and
central North Dakota later tonight into Tuesday morning.
Confidence on prevailing categorical restrictions is not high
enough to add to any of the TAFs at this time. Light snow is
forecast to spread across northwest North Dakota Tuesday
afternoon, possibly reaching central North Dakota by the
evening. Northwesterly winds will continue to diminish this
evening, becoming light and variable overnight and then
southeasterly around 10 kts in western North Dakota on Tuesday.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Hollan
DISCUSSION...TWH
AVIATION...Hollan
Area Forecast Discussion
National Weather Service Grand Rapids MI
946 PM EST Mon Nov 25 2024
.KEY MESSAGES...
- Snow showers possible later tonight into Tuesday, mainly north
- Light Snow Possible Wednesday Night
- Cold With Lake Effect Late This Week
&&
.UPDATE...
Issued at 945 PM EST Mon Nov 25 2024
The cold front has passed through and winds will continue to
increase out of the west-northwest overnight. Low level
convergence near/west of Hwy 131 has caused a recent uptick in
shower coverage just west of GRR/AZO but overall we should see a
diminishing trend in the light rain/drizzle overnight with arrival
of drier air from the west.
Will keep the snow showers in the forecast later tonight (after 4
AM or so) for areas near/north of Big Rapids. However latest HRRR
soundings at CAD indicate that the DGZ may be only marginally
saturated as moisture depth decreases by that time. This implies
mainly light snow showers/flurries or perhaps just a very light
drizzle/snow grain mixture. Either way minimal impact expected
given sfc temps which look to stay above freezing through the
majority of the night and current road temps in the lower 40s.
&&
.DISCUSSION...
Issued at 212 PM EST Mon Nov 25 2024
- Snow showers possible later tonight into Tuesday, mainly north
Cold air advection strengthens on the backside of the departing
storm system tonight. While considerable drying occurs over much of
the CWA during this period, northern zones are forecast to see
saturated conditions in the -10 to -15 deg C level with a west to
northwest flow. Low level convergence will be most favorable across
Mason and Oceana counties, including the Ludington area. Any bands
of snow will spread inland towards Baldwin and Evart. Surface
temperatures are shown to be near or just above freezing. Thus a
few slick spots appear possible, mainly for elevated surfaces such
as bridges and overpasses. We will increase POPs to account for
this scenario and add the risk to the Hazardous Weather Outlook.
Further south the forecast soundings look too dry to support much in
the way of snow showers. Ensemble guidance does support windy
conditions Tuesday with coastal locations expected to see values in
the 25 to 35 mph range.
- Light Snow Possible Wednesday Night
Snow chances return across the area late Wednesday into Wednesday
Night. This is due to the phasing of a shortwave out of Canada with
a wave crossing into the CONUS off of the pacific coast. The
associated surface low that develops across the Ohio Valley looks to
clip areas south of I96 with the northern edge of its precipitation
shield Wednesday Night into Thursday morning.
The most likely outcome is that our southern few rows of counties
get clipped with a few tenths of an inch of snow Wednesday Night,
possibly mixing with rain initially as the low stays well south.
While 12z guidance continues to converge on this solution, there are
still a few members (mainly from the EPS) that nudge the low
northward and drop a few inches in our southern forecast area. Some
uncertainty also exists on the northern end thanks to the potential
for dry air eroding at the precipitation shield. Overall, impacts
should be lower since the snow occurs overnight after holiday travel
is over for most. However, we will continue to monitor and refine
the forecast as needed. Thursday itself should be dry, albeit cool,
across West Michigan.
- Cold With Lake Effect Late This Week
The Thanksgiving reprieve is short-lived however as much colder air
aloft arrives Thursday Night as longwave troughing sets up across
the Great Lakes. With water temps still near +12C, 850mb temps
falling to near -12C will generate notable over-lake instability.
Combined with cyclonic flow as the jet moves south, lake effect snow
develops Thursday Night and continues into Friday. Based on forecast
flow patterns from the WNW to the NW and best forcing, the heaviest
snow will be for areas south and west of Grand Rapids. With
probabilities of exceeding 4 inches near 50 percent in this region,
advisory level conditions are possible. Lesser snow amounts are
expected across the rest of the CWA.
Saturday sees snow showers diminishing as mid-level height rises
occur over lower Michigan, before cyclonic flow takes hold again
Saturday Night. Once this happens, the continued cold airmass allows
lake effect to redevelop and continue into early next week in more
of a WNW flow pattern. In addition to the periods of lake effect
snow, a significant cooldown is expected as the modified arctic air
mass takes hold. In sharp contrast to the 50s observed this
afternoon, highs Friday into the weekend look to remain below
freezing.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 647 PM EST Mon Nov 25 2024
Widespread IFR/LIFR conditions prevailing this evening with low
stratus clouds and areas of rain/drizzle. Cigs and vsbys
improving later this evening to mostly MVFR as the rain exits and
winds increase with a cold frontal passage. West-northwest winds
will frequently gust to 25 to 30 kts overnight into Tuesday
behind the cold front. Cigs should finally improve to VFR levels
by Tuesday afternoon with drier air pouring in.
&&
.MARINE...
Issued at 212 PM EST Mon Nov 25 2024
Close call for gale conditions over the nearshore waters
tonight into Tuesday. Bufkit overviews for BIV show mixing heights
reaching into the 30 to 33 knot range tonight. Thus, it`s looking
likely that coastal sites will reach 30 knots. While a few gale
gusts appear possible, at this time, they are not expected to be
frequent. Thus we will keep the Small Craft Advisory going.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 7 PM EST Tuesday for LMZ844>849.
&&
$$
UPDATE...Meade
DISCUSSION...MJS/Thomas
AVIATION...Meade
MARINE...MJS
Area Forecast Discussion
National Weather Service Marquette MI
714 PM EST Mon Nov 25 2024
.KEY MESSAGES...
- Snow continues this evening, mixed with rain near the Great
Lakes. The highest snowfall rates this evening will be across
the eastern half of the UP. Generally speaking, 2-4 inches of
snow accumulation through this evening with less than an inch
along the Great Lakes.
- System snow changes over to lake effect snow tonight,
continuing through Tuesday. The heaviest snowfall rates will
be across the western snowbelts of the western UP tonight,
then the west-northwest snowbelts in the eastern UP Tuesday.
- Lake-effect snowfall continues over the west-northwest to
northwest snow belts the rest of this week through this
weekend. Expect several inches of fluffy snowfall over these
snow belts through the next 7 days.
- Temperatures will become below normal for this time of year by
late this week, with high temperatures failing to reach
freezing by then.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 412 PM EST Mon Nov 25 2024
Water vapor imagery and RAP analyses show a midlevel low over
Manitoba, while to the south, a shortwave continues to move into the
Upper Great Lakes. At the surface, low pressure is moving east of
Lake Michigan through the Lower Peninsula. Our second batch of snow
is already east of M-95 this afternoon, with radar and satellite
trends indicating an uptick in snowfall rates (will also note that
visibility dropped below a mile at KSAW at the onset of higher
reflectivity). Ensemble mean snowfall rates are at around a half-
inch per hour throughout the eastern UP through the evening,
but hi- res guidance does show around a 40% chance for snowfall
rates in excess of an inch this evening, mainly from Delta and
Alger county eastward. This should manifest at the ground as
another 1 to 3 inches of snow accumulations across most of the
area, with higher totals of 2-4in possible across the eastern
UP before 00Z. Nearer the Great Lakes, lighter amounts are
expected with milder lake temperatures. Meanwhile, to the west,
drier midlevel air nosing in will help to cut back snowfall
rates from west to east into the early evening.
System snow wraps up in the eastern UP by 06Z tonight. However,
winds shifting over to the west, then eventually northwest will see
a change over to lake enhanced and then eventually lake effect
snowfall. Additionally, guidance continues to hint at enhanced
convergence into the western UP as the surface low moves
towards the "thumb" of Lower Michigan. Simulated reflectivity
shows stronger banding pointed...somewhere between southern
Ontonogan county and Houghton beginning around 03Z. For what
it`s worth, ensemble mean snowfall rates also pick up to around
an inch at that time, lingering into Tuesday. SLRs remain on
the lower end for lake effect given rather mild soundings;
expect SLRs initially at around 9-11:1 across the UP the first
half of the night, increasing to around 10:1 east and 12-14:1
west after 06Z. The exception, as always, will be those
lakeshore areas which will continue to see SLRs below 10:1. With
a widespread 0.10-0.25 in the eastern UP and the western
snowbelts, expect this should yield another 1-3in of snow away
from the lakeshores by sunrise (lighter amounts in the south-
central UP). However, where we can get that local enhancement in
the west, heavier totals up to 3-5in wouldn`t be ruled out.
With lake effect snow expected to continue into the daytime
Tuesday, our winter weather advisories in the western and
eastern UP have been extended into Tuesday afternoon and
evening.
Otherwise, expect temperatures to turn much cooler compared to last
night with a cooler airmass working in.Lows range in the mid/upper
teens in the interior-western UP, and in the 20s in the eastern UP
and the Keweenaw. Westerly winds will also be on the uptick the
second half of the night, gusting up to 20-25mph in the western UP
after midnight.
&&
.LONG TERM /TUESDAY THROUGH MONDAY/...
Issued at 412 PM EST Mon Nov 25 2024
Lake-effect snow is the primary story of the extended forecast as a
broad mid level troughing pattern sets up over the eastern CONUS and
eastern Canada. With this generally northwest to northerly flow
continuing for a lengthy period of time, temps trend below normal.
Highs already on Thursday are expected to mainly be below freezing
with lows over the weekend falling into the teens in the interior
and 20s by the lakeshores.
Starting on Tuesday, a shortwave over western Upper MI darts east
while another shortwave over the Lower Great Lakes lifts north,
phasing together over southern Ontario/Quebec Tuesday night. WNW LES
is expected Tuesday morning with anomalously warm sfc temps on Lake
Superior (~7.75C) and 850mb temps ranging from -6C to -14C, colder
west. Upstream pre-treatment from Lake Nipigon and converging flow
over the longer fetch of north central and eastern Lake Superior
means the best potential for accumulating LES is over the east as
winds veer more NW. This all coincides with the best synoptic lift
from the passing shortwave and descending DGZ down to 5-10kft.
Inversion heights on model soundings look to reach into or through
the DGZ over the eastern UP with ample available moisture below the
inversion. A similar vertical profile is noted near Copper Harbor;
moisture decreases and inversion heights lower when moving
southward. This should be a drier and fluffier snowfall compared to
today, although deep moisture is not expected. Thus, the forecast
reflects SLRs in the low to mid teens:1. Initially the dominant LES
band Tuesday morning, highlighted by the high-res guidance, has a
more west to east orientation over the Keweenaw and bends southeast
toward Munising. Later in the morning, stronger LES bands look to
develop over the north central and eastern portions of Lake
Superior, impacting the eastern UP Tuesday afternoon into Tuesday
night. Much of the guidance is leaning into the Lake Nipigon pre-
treatment and confluent flow resulting in a stronger band delivering
advisory level snowfall somewhere in the eastern CWA. Where this
sets up is still uncertain as WNW to NW solutions leave the
potential area of this more dominant band setting up large;
somewhere between Munising and White Fish Point. This band is likely
to hold into Tuesday night. Opted to continue the Winter Weather
Advisory for Alger, northern Schoolcraft, and Luce counties through
7PM EST Tuesday to account for potentially moderate to heavy LES
snow, providing additional snow accumulations as high as 4-8" and
possible travel impacts. Also continued the Winter Weather Advisory
for Ontonagon, Houghton, and Baraga counties through 1PM Tuesday for
the additional accumulating snow up to 1-3" earlier in the day.
Otherwise, some gustier winds up to 20-30 mph are likely near Lake
Superior and in the Keweenaw on Tuesday. Highs will peak in the mid
20s to mid 30s, colder interior west.
Weak sfc ridging with drier air lifts northeast into the Great Lakes
moving into Wednesday, dissipating over the Lower Great Lakes
Wednesday night. Meanwhile, the mid level closed low spins over
Quebec while a shortwave swings southeast through the Midwest. This
may result in drier periods and/or weaker LES, driest conditions
expected over the west half of Upper MI, Tuesday night through
Wednesday. PoPs re-invigorate moving into the rest of the week as
the shortwave moves over the Great Lakes. Sfc high pressure then
builds in the lee side of the Canadian Rockies and descends south
into the Plains for the weekend with a sfc low spinning northeast of
the Great Lakes. Meanwhile, mid level troughing continues to impact
the Great Lakes and 850 mb temps gradually lower to between -10 to
-12C across the region for the weekend. With northwest to north flow
persisting through next weekend, LES continues the rest of the
extended forecast. Additional winter weather products may be needed
in future forecast packages to cover LES accumulations and hazards
during the coming days, especially with holiday travel.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 714 PM EST Mon Nov 25 2024
Ongoing light system snowfall is slowly departing as low pressure
over Lower Michigan continues its northeastward trek. Low end MVFR
to mainly IFR conditions are expected to continue overnight before
drier air works its way into the UP tomorrow. Widespread snow will
be transitioning to lake effect snow overnight as winds turn west-
northwest and increase with gusts 20-25 knots, upwards of 30 knots
at CMX. Noted on KDLH radar and observations, convergence and lake
effect snow is beginning to take shape near the Bayfield Peninsula.
As a result, some stronger snow showers are briefly possible at IWD
for the next several hours.
As westerly flow continues developing across western Lake Superior,
guidance is in good agreement of a dominant convergence LES band
impacting CMX just after midnight. LIFR conditions, possibly as low
as 1/4mi visibility, are under this band between around 06z and
could last until ~12z. NNW lake effect snow will continue into the
afternoon hours with conditions improving to MVFR at SAW and IWD.
&&
.MARINE...
Issued at 412 PM EST Mon Nov 25 2024
Light east becoming north winds 20 kts or less are expected ahead of
cold front passing east over the lake this evening through tonight.
Behind the front, northwest winds of 20-30 kts are expected across
the lake that continue through Tuesday. A few gale force gusts up to
35 kts are possible (~20-40% chance) during the day Tuesday, mainly
over the southeastern waters between Big Bay, Stannard Rock, and
Grand Marais. This also could yield significant wave heights up to 8
ft over the southeastern waters Tuesday into Tuesday night.
Northwest winds gradually weaken Tuesday night to around 20 kts or
less, continuing through Wednesday night as weak ridging skirts its
way across the Upper Midwest. With a troughing pattern persisting
over the Great Lakes, generally northwest winds continue the rest of
the forecast with 15-25 kt winds expected Thursday and Thursday
night, increasing to 20-30 kts for the weekend.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory until 1 PM EST Tuesday for MIZ002>004-
084.
Winter Weather Advisory until 7 PM EST Tuesday for MIZ006-007-
085.
Winter Weather Advisory until 1 AM EST Tuesday for MIZ013-014.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...LC
LONG TERM...Jablonski
AVIATION...BW
MARINE...Jablonski
Area Forecast Discussion
National Weather Service Pocatello ID
147 PM MST Mon Nov 25 2024
.SHORT TERM...Today through Tuesday Night.
We really are in the "calm before the storm" today, but that will
end sooner rather than later. Satellite and radar early this
afternoon show our next system still to our south, but with cloud
cover increasing and moisture steadily lifting northward through
Nevada and Utah. This continues through the rest of the afternoon
and evening with snow finally arriving in the South Hills and
Southeastern Highlands around 11 PM, give or take an hour on either
side. This initial push of moisture continues northward through
tonight and is expected to fall as all snow given forecast
temperatures. This will be more of a rain/snow mix at times in the
eastern Magic Valley and parts of the lower Snake Plain, but a
transition from predominantly snow to mostly all rain becomes more
likely mid-morning on Tuesday, though this first push of moisture
will be wrapping up in these areas around the same time. Expected
precipitation on and off through Tuesday, though it does become a
bit more scattered and showery in nature during the afternoon. As a
cold front drops southeast Tuesday evening, the HRRR is doing a
decent job of showing a band of snow coming with it through the
Central Mountains and through a line from Driggs to Idaho Falls to
around Pocatello. The 4km NAM hasn`t quite picked up on this yet and
the NBM and U of A WRF are hinting at it, so this band potential
will be something to keep an eye on and could push overall snow
totals a bit higher (think closer to 2" for Pocatello and Idaho
Falls and 3" for Driggs) in that corridor. Surface winds aren`t
particularly impressive for a convergence band as they will be
mainly from the W/SW still and they look messy behind the cold
front, but 700 mb winds behind the front will certainly be from the
north by Tuesday evening, so that`s a small point in its favor.
A WINTER STORM WARNING continues for the Bear River Range for this
event as snow totals range from 6 to 12 inches and locally higher
amounts above pass level. The latest HREF data shows about a 40
percent chance of at least 8 inches of snow at Emigration Pass,
which is the area where travel impacts will be the greatest. WINTER
WEATHER ADVISORIES continue for the Bear Lake Valley, Blackfoot
Mountains, Big Hole Mountains, and Caribou Range where totals
generally range from 2 to 6 inches with locally higher amounts above
7000 feet. Briefly thought of adding the Ashton/Driggs zone into the
advisory, but snow totals there generally fall into the 2 to 3 inch
range with about a 20 to 30 percent chance of reaching 3 inches in
those two cities, so ultimately decided against it. Elsewhere, snow
totals will generally range from about a half inch to an inch in the
eastern Magic Valley, a half inch to one and a half inches in the
Snake Plain with a 10 to 20 percent chance of at least 2 inches of
snow, and 1 to 2 inches throughout the lower elevations of the
Central Mountains.
Thankfully, wind isn`t much of an issue with this system as gusts
generally remain around 15 to 20 mph tonight and tomorrow. They will
increase to 20 to 30 mph around Burley Tuesday night, but
precipitation will be finished in that area by that time. Either
way, falling snow across the area (especially in our advisory and
warning areas) will impact travel conditions at times.
AMM
.LONG TERM...Wednesday through Monday
By daybreak Wednesday, our latest round of winter weather will be
coming to an end. Still expecting to see some lingering snow showers
across the higher terrain of the eastern and southeastern highlands
but the majority of significant accumulation will have ended already
by this point. This will usher in a prolonged period of quiet,
albeit cold, weather across eastern Idaho. Strong NW flow aloft will
remain in place for the Thanksgiving holiday and through early next
week. Daytime highs in the 20s and 30s are expected during this time
period with overnight lows in the single digits and teens expected.
We will probably see some periods of prolonged stratus in the upper
Snake highlands and up towards around Island Park which may result
in some flurries, at times, but no significant snowfall
accumulations are expected anywhere across the area from
Thanksgiving and beyond. McKaughan
&&
.AVIATION...18Z Monday to 18Z Tuesday.
VFR conditions in place this afternoon with satellite showing
gradually increasing cloud cover ahead of an approaching weather
system that will bring snow to the region throughout much of the day
tomorrow. Winds will remain light, 10 maybe 15 kts at the highest,
throughout this storm which is a relative rarity around here. As
precip begins to move in during the overnight hours tonight, expect
gradually lowering CIGs and eventually snow impacting all the
terminals but still not much in the way of confidence or duration
based on hi-res model guidance. That being said, current forecast
shows the downward trend in CIGs and VSBYs in association with snow
but we`re probably not looking at continuous snow for the latter
portions of the 18Z TAF cycle, just too difficult to time out any
start/end times based on latest model runs so kept things a bit more
vague than preferred at the moment. McKaughan
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from 11 PM this evening to 10 AM MST
Wednesday for IDZ060.
Winter Weather Advisory from 11 PM this evening to 10 AM MST
Wednesday for IDZ061>064.
&&
$$
Area Forecast Discussion
National Weather Service Riverton WY
422 PM MST Mon Nov 25 2024
.KEY MESSAGES...
- Dry and seasonable today with some breezy winds across Natrona
County.
- Next system pushes in after midnight and throughout Tuesday
into early Wednesday.
- Mainly dry but cooler than average for the rest of the week
into the weekend outside of minimal mountains snow out west.
&&
.DISCUSSION...
Issued at 1142 AM MST Mon Nov 25 2024
IR currently depicts the next Pacific northwest system pushing
over the Cascades and into the northern Rockies. Radar currently
dry and will remain so through the evening and early overnight
hours. The only element to be considered will be the breezier
winds across Natrona county with the lingering gradient across
there and points south and southeast. Gusts up to 25-30 mph
possible but quickly will diminish towards sunrise with
radiational cooling under mainly clear skies. As the shortwave
nears after midnight, the jet flattens across the CWA pumping in
the mid to upper level moisture with a more zonal pattern. The
main trough off the northwest coast actually is trending to fill
with decreasing divergence aloft. However, the jet will dig the
trough further south as it slowly pushes towards the CWA giving
way to a more southwest system influencing the western and
southwestern mountains for much of Tuesday. Snow will begin to
push in from the southwest after the 06Z timeframe spreading
north and northeast through the morning to the Divide. Short
fused models agree on snow pushing across the southern end of
the Divide through the wind corridor of Sweetwater to Natrona
counties. Where models disagree will be the wrap around moisture
behind the cold front Tuesday night into Wednesday morning. The
HRRR and NAM Nest are more prudent on snow development across
the Wind River and Bighorn Basins, mainly for the Lander
Foothills. PoPs were bumped up a bit in favor of this trend,
but, however, snow amounts have had little change as
accumulation looks to still be light at best with this quick
transition. Otherwise, highest accumulations for the western
mountains and even into the valleys of Star and Jackson Hole
with 60-70 percent probabilities of 2 or more inches.
With this system being a more progressive southwestern trough,
it will quickly push east Wednesday morning giving way to a
colder yet dryer day for travel and into Thanksgiving. A more
northwest, dry flow for the remainder of the week and into the
weekend. This will keep any subtle shortwaves to the north and
northeast with only minimal mountain snow chances sporadically
with the Bighorns being the better chance moving forward.
Ridging builds in with increasing convergence aloft remaining on
the cool side into early next week before it shifts a bit east
to bring in a warming trend to start the month of December.
Nothing significant is indicated with the longer term models,
but, as always, will be updated when things change over time.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 421 PM MST Mon Nov 25 2024
West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals
All terminals remain VFR through 06Z/Tuesday before a plume of
Pacific moisture reaches western Wyoming. Shortwave energy and jet
dynamics combine with the moisture to generate widespread light snow
and MVFR conditions beginning 08Z-12Z/Tuesday. The heaviest snow and
intermittent IFR is anticipated from 12Z-18Z/Tuesday. Current model
forecast soundings and IFR/MVFR percentiles indicate slowly
improving conditions between 20Z-22Z/Tuesday. Surface wind speeds
generally remain 10kts or less until gusty west-southwest wind 10-
15kts develops at KRKS early Tuesday afternoon. Mountain tops
obscured after 08Z/Tuesday.
East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals
VFR prevails at all terminals through the forecast period as
westerly flow aloft transports increasing mid/high cloud cover into
the region. Increasing Pacific moisture could lead to a few late
Tuesday morning and afternoon rain/snow showers developing over
central Wyoming, but terminals will not be impacted. Scattered snow
showers develop after 21Z/Tuesday over northern Wyoming with KCOD
possibly (30 percent or less) seeing a brief shower. In general,
these should largely miss terminals through 00Z/Wednesday. KCPR
southwest surface wind remains 12-16kts overnight before increasing
again to 18-28kts between 15Z-18Z/Tuesday as mixing improves.
Otherwise, surface winds generally remain less than 10kts.
Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on smoke, icing, and turbulence forecasts.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 11 PM this evening to 5 AM MST
Wednesday for WYZ012-013-023-024-027.
&&
$$
DISCUSSION...Lowe
AVIATION...CNJ