Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/31/24
Area Forecast Discussion...Updated
National Weather Service Billings MT
842 PM MST Mon Dec 30 2024
.KEY MESSAGES...
- Light snow/flurries will persist tonight, mainly west of Rosebud
county. Additional accumulations will be less than an inch.
- Light snow over south-central Montana (including Billings)
Tuesday morning. Accumulations of a half inch to 2 inches
forecast.
- Below normal temps continue through the week, with additional
periods of light snow; a stronger system may impact our region
Friday & Saturday.
&&
.Updated Aviation Discussion Below...
Minor update for temperatures, which are dropping near or below
forecast already this evening. Also increased coverage of fog with
current RH values near saturation across the area. Light snow
currently in the forecast for this evening is on track based on
latest radar imagery. HRRR continues to show additional area of
snow developing around sunrise as another push of colder air drops
down the front range and strengthens the low level convergence
area over western and central forecast zones. Current forecast has
this covered well. Finally, roads have iced up as anticipated this
evening. MTDOT webpage indicates most rural roads are showing
icy/snow covered and MHPs website shows numerous
slideoff/accidents. So, please slow down and drive with extra
caution tonight so you can get to your destination safely.
Chambers
&&
.DISCUSSION...
Rest of Today through Wednesday Night...
The light to moderate snow persisting across portions of the area
this afternoon will taper off by this evening. Additional
accumulations with this activity are expected to be light. While
the threat for snow will decrease this evening, temporarily, the
threat for slick roads will continue through tonight as air
temperatures drop into the 20s in south-central Montana and teens
in south-eastern Montana. Patchy fog may develop as well (overall
low chance). Use caution walking or driving tonight into Tuesday
morning as wet roads and sidewalks could become slick. For the
latest road conditions, call 511, or visit 511mt.net (MT) or
wyoroad.info (WY).
The chance of snow then increases again tonight into Tuesday
across south-central Montana. While the snow looks to be overall
light, the temperature and moisture profile will allow the
dendritic growth layer to be at play. Because of this, forecast
snow totals are generally around a half inch to 2 inches.
Probabilities for more are low (30 percent or less, highest south
of Billings into the Pryor Mountains). With this event, south-
eastern Montana looks to remain dry. Drier conditions return
across the area later Tuesday into Wednesday with flat ridging
aloft. By Wednesday night into Thursday, the chance of snow
increases once again over south-central Montana (15 to 60 percent
chance, highest in the mountains).
With the snow, temperatures look to remain cooler through mid-
week with highs in the low 30s to 20s Tuesday and Wednesday.
Overnight lows look to drop into the teens to single digits,
coldest in the east. Arends
Thursday through Sunday...
Models continue to show 500 mb ridging over the Rockies for the
latter part of the work week while colder air persists over the
high plains. Minor weak waves in the mid level flow Wednesday
night into Thursday set-up weak overrunning pattern and may produce
some NW/SE bands of light snowfall over the middle sections of
our CWA during this time. Its very difficult to determine exactly
how far west a band may set up, as the cold air is shallow and may
wash back and forth easily, but an inch or so locally through
Thursday night is a possibility within any persistent band that
may develop. It does appear the pattern will favor easterly
surface winds over the lower elevations, possibly backing up all
the way into the foothills. So temps will remain on the colder
side of normal the rest of the week with highs mainly teens east
to 20s or lower 30s along the western foothills. We will continue
to adjust temps in the foothills lower than our NBM guidance which
is still 10 degrees above ensemble means for some locations like
Livingston. In addition...this pattern, with persistent shallow
easterly winds, may also support an extended period of stratus
and/or fog keeping temps colder than models may suggest.
Models are in agreement that a mid level Pacific trough will
track across the region late Friday through Saturday. While the
exact strength, timing and track remain uncertain, we should see
an increasing chance of accumulating snow. For lower elevations,
ensembles suggest a 25-50% chance of 2+ inches of snow next
weekend (highest NE of Billings), and a 15-30% chance of 4+
inches. Western mountains could see significant snowfall from
Friday through Saturday with a 70% chance of exceeding 6 inches
(west aspects favored).
It should be noted there is a risk of subzero temperatures toward
the end of the week over the east depending on how much we tap
into colder Canadian air, eastern locations could flirt with highs
near zero Friday thru the weekend (currently a 15-30% chance of
sub-zero highs at Miles City, Baker and Ekalaka). So don`t be
surprised if you see forecast temps trend down later this week.
If you have travel plans late this week, be sure to monitor the
forecast closely. BT
&&
.AVIATION...
Light snow continues around KBIL to KSHR. Expect MVFR/IFR
conditions, with LIFR conditions possible with lower ceilings.
Snow activity will diminish overnight, before picking back up
around KLVM- KBIL- KSHR around 12z and ending by midday. Patchy
fog is possible for all sites into the morning hours. Mountain
obscurations will persist through the forecast period.
Matos
&&
.PRELIMINARY POINT TEMP/POPS...
Tue Wed Thu Fri Sat Sun Mon
-----------------------------------------------------------
BIL 021/032 016/028 015/024 011/020 010/021 008/021 008/022
56/S 01/E 33/S 33/S 56/S 52/S 22/J
LVM 022/034 016/032 018/033 022/029 020/028 020/034 019/034
53/S 02/S 43/S 35/S 76/S 42/S 43/J
HDN 021/030 014/029 014/023 010/023 010/022 006/019 003/021
45/S 11/E 44/S 43/S 67/S 63/S 33/J
MLS 017/023 012/022 008/016 001/012 001/015 000/010 908/009
11/E 10/E 22/S 31/E 56/S 61/E 11/B
4BQ 019/027 013/028 012/022 009/020 008/020 005/015 901/016
21/E 00/B 11/E 20/E 46/S 61/E 11/B
BHK 015/021 008/023 004/016 902/012 904/010 904/010 909/009
11/E 00/E 10/E 10/B 46/S 51/E 11/B
SHR 018/031 009/031 010/029 011/030 013/029 008/026 007/027
23/S 00/B 11/B 11/E 36/S 62/S 22/J
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings
Area Forecast Discussion
National Weather Service State College PA
753 PM EST Mon Dec 30 2024
.SYNOPSIS...
* Blustery conditions will continue today with occasional rain
and snow showers across northern PA today.
* A ridge of high pressure brings dry conditions tonight into
Tuesday morning followed by another round of rain later
Tuesday afternoon into early Wednesday.
* Gusty winds and a colder airmass arrives on Wednesday and
continues through the end of the week as lake effect/upslope
snow ramps up to kick off 2025.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
745 pm update... The current forecast is in very good shape, so
just some minor tweaks were made at this time to reflect the
latest observational trends.
Water vapor satellite imagery continues to show the southeastern
Canadian upper low lifting out to the northeast this evening,
along with its associated pool of cold air aloft and moisture.
As this northeastward shift continues overnight, we expect a
clearing trend to develop across the northern tier by around, or
shortly after midnight.
The combination of clear skies and diminishing winds should lead
to good radiational cooling conditions, in all probability
producing at least patchy river valley fog for northern PA,
given fairly wet ground conditions from recent rainfall. As a
result, we added a mention of patchy late night fog for areas
near and north of I-80.
Thicker mid to high-level cloudiness in advance of tomorrow`s
rain making system should begin to impinge on at least the
Alleghenies and Laurels, as we approach sunrise.
Lows by daybreak should range from the upper 20s across the
northern tier, to the mid 30s for many locales south of I-80.
Previous discussion... Unsettled weather continues as a potent
mid and upper level trough moves across the region. Scattered to
numerous rain showers are expected to continue this afternoon
and gradually taper off as the trough lifts northeast tonight.
Thermal profiles support a few snow showers mixing in across the
northern tier this evening. Gusty west-southwest winds will
gradually weaken into the overnight hours as the pressure
gradient lets up and high pressure builds in.
High temps across the Western Mtns in the upper 30s to mid 40s will
occur early today before leveling off or even sliding by a few
degrees this afternoon. The Central Ridge and Valley Region and
Susq Valley will see just a slight rise in temps in the
downslope westerly flow behind the cold front before the cold
air deepens later today.
A ridge of high pressure at the sfc and aloft will slide east
across the region tonight with a brief period of clear to partly
cloudy skies early, followed by thickening high clouds late. Mins
tonight will be in a rather tight range (in the upper 20s to
mid 30s) as the cloud cover cuts off radiational cooling first
and most across the typically colder NW Mtns and Laurels -
leveling the playing field for temps.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Tuesday starts off relatively mild for this time of year (+10 to
+15 compared to average) with increasing clouds and building
southeasterly flow. By Tuesday afternoon, precipitation ahead
of our next weather maker will move into southwest PA. Rain will
overspread the region during the day on Tuesday as an occluded
front crosses the state attached to a center of low pressure
that will move across northwest PA Tuesday night into Wednesday
morning. Convection allowing models indicate potential for some
heavier showers and a quick quarter to half inch of rain for
much of southwest and central PA on Tuesday afternoon. Near and
southeast of the triple point (where the cold/warm/occluded
front meet), there appears to be a narrow corridor of potential
for elevated convection and perhaps a rumble of thunder or two.
This is outlined in the Day 2 SPC Convective Outlook, with
General Thunder across much of the eastern seaboard extending
northwest into the Lower Susquehanna Valley.
Behind the cold front, much colder air will pour into
Pennsylvania and support a transition to rain/snow during the
pre- dawn and morning hours on Wednesday. Accumulating snow
during the day on Wednesday should be generally confined along
and north/west of the Allegheny Front, though a coating cannot
be ruled out on grassy/untreated surfaces farther east. As
winds shift to the west/northwest Wednesday, a tightening
pressure gradient will generate very gusty winds Wednesday and
Wednesday night. Have trended above NBM guidance for winds and
wind gusts in that period to account for the synoptically-
enhanced pattern. A Wind Advisory will likely be needed for the
preferred downsloping regions in the Laurels and perhaps across
much of the forecast area.
By Wednesday night, subzero C 850mb temps traversing the Lake
Erie waters will reinvigorate the lake effect and upslope snow
machine by Thursday morning, which a preferred fetch into
northwest PA. A long-duration lake effect/upslope event appears
likely to continue through the weekend. Uncertainty remains with
where the heaviest snowfall will set up, but the highest
snowfall totals are expected in extreme northwest county, where
a Lake Effect Snow Watch is in effect from Wednesday morning
through Sunday afternoon. Winds are likely to be westerly for
much of that stretch with multiple periods of enhanced activity
over the 4.5-day stretch. As is typical with these events,
narrow bands of heavy snow are expected and will lead to a
sharp gradients of snowfall downwind of Lake Erie. The highest
probability for 6"+ is in extreme northwest Warren County, but
advisory- level snow amounts could be observed into McKean,
Potter, and Elk Counties as well as in the Laurel Highlands
(Somerset/Cambria).
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
Zonal flow aloft continues Thursday and Friday with a deep low
pressure center parked over the Canadian Maritimes and high
pressure over central Canada. The result with be a persistent
northwest flow with cold air funneling into much of the lower
48. Pennsylvania looks likely to be in gradient flow for the
end of the week and into the weekend. The result will be
blustery winds, lake effect snow, and a downward trend in
temperatures each day to kick of 2025.
Highs on Friday are progged to be in the low 20s to mid 30s. By
the end of the weekend, highs may be 10 or more degrees colder,
with lows in the upper teens to near 30. Add in some winds, and
single digit wind chills are likely for through the extended
period. On the heels of 2024, which is likely to be the warmest
year on record across much of Pennsylvania, 2025 is expected to
start off will a prolonged stretch of below- normal
temperatures.
The next chance for widespread snow showers will come Sunday
night into Monday morning of next week as the pattern shifts
from zonal to meridional. Long range ensembles depict a stacked
low pressure system tracking across the Ohio Valley, bringing
southerly surface flow with moisture and reinforcing cold air
from the upper level flow.
&&
.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
Clouds continue to decrease in coverage this evening as low
pressure drifts off to the northeast and upper level ridging
moves in from the west. The back edge of the clouds is near BFD
and IPT as of 00Z and will be northeast of those sites within
the next hour or two. Mainly clear skies are expected overnight
areawide with fairly high confidence with the exception of BFD
where guidance disagrees on the evolution of the cloud cover.
The GLAMP suggests MVFR ceilings stick around through much of
the night while RH profiles from the HRRR and RAP suggests that
skies will clear out there as well. Based on current satellite
trends, stuck much closer to the HRRR and RAP and show VFR
conditions returning to BFD by 03Z. Winds will also continue to
decrease overnight, with winds generally dropping below 5 knots
after 06Z. Patchy fog can`t be completely ruled out near BFD
overnight, but confidence is low on any visibility restrictions
developing.
High clouds increase once again Tuesday morning ahead of another
low pressure system that will track through the region. Ceilings
will gradually lower through the morning from west to east and
rain will begin to approach BFD and JST after 18Z. The rain will
push eastward through the afternoon with all airfields seeing
rain by 00Z. Ceilings will lower to MVFR as the rain moves in.
Outlook...
Wed...Rain pulls east of the area, with gusty west winds
developing. -SHSN developing N/W PA.
Thu-Fri...Restrictions remain poss N/W in -SHSN; gusty west
winds continue areawide.
Sat...Lake effect SHSN continue across N/W.
&&
.CLIMATE...
Williamsport...A record high temperature of 60 degrees was set
at Williamsport, Pennsylvania today. This break the old record
of 56 degrees set in 1984.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Wednesday morning through Sunday
afternoon for PAZ004.
&&
$$
SYNOPSIS...Banghoff
NEAR TERM...Jurewicz/Banghoff
SHORT TERM...Banghoff
LONG TERM...Banghoff/Bowen
AVIATION...Bauco
CLIMATE...Evans
Area Forecast Discussion
National Weather Service Des Moines IA
623 PM CST Mon Dec 30 2024
...Updated for the 00z Aviation Discussion...
.KEY MESSAGES...
- Rain will transition over to snow this evening across central and
southern Iowa. Snow accumulations of 1-3" are possible with higher
end amounts most likely in west-central Iowa.
- Cooling trend this week with highs in the teens and low 20s by the
end of the week.
- A quick moving system will bring snow to central and southern Iowa
on Thursday (40-60% chance for accumulating snow).
- Large system may impact the area this coming weekend.
&&
.DISCUSSION...
Issued at 314 PM CST Mon Dec 30 2024
Another dreary day across Iowa has fog hung around through midday
and low stratus continues to blanket the area. A robust surface
low centered across southern Kansas and Missouri has allowed
for precipitation to develop on the northern side in southern
Iowa this afternoon. This low will continue to lift north and
east through the evening and into Tuesday with precipitation
becoming widespread through that time. While we lose daytime
insolation into the evening the system will pull in colder air
as it continues to wrap up across the midwest. This combination
will shift precipitation type from rain to snow this evening
with all snow generally after midnight. How quickly will this
transition to snow happen, and therefore how much snow can be
expected? Models, both CAMs and synoptics, have trended cooler
and therefore snowier over the past 12 hours. As the previous
discussion mentioned, the GFS remains warmer and less snowy
compared to the Euro, but it should be noted that even the more
recent GFS runs have trended towards snowier solutions. Right
now 2- 3" of snow are possible in west-central Iowa with an inch
or less into central Iowa. The HRRR and RAP have shown similar
trends, though with higher resolution have picked up on isolated
higher pockets of snow possible. Should an earlier snow
transition occur, a few spots may see over 3" of snow by
Tuesday morning. HRRR trends have been less consistent, wavering
on the rain-snow line more run-to-run compared to the more
consistent RAP. Another detail here is that the forcing shifts
east as temperatures drop below freezing, which may contribute
to lesser snow amounts (compared to raw guidance indicating
higher possible totals).
As the system shifts east, cold air advection, increasing
subsidence, and the enhanced pressure gradient will come
together and allow for increasing northwest winds. Current
soundings indicate gusts of 20-25+ mph gusts possible overnight
and continuing into Tuesday morning. This will help to further
reduce visibility in falling snow as light snow lingers into
Tuesday morning. While winds remain elevated into Tuesday after
snow comes to an end, blowing snow is generally not expected to
be a big problem as snow is expected to be of a heavier/wetter
variety rather than the lighter blowable type.
Tuesday will kick off the cooling trend through the rest of the
week with highs in the 20s and 30s. Reinforcing shots of arctic
air will continue with waves through the end of the week. While
a few will be dry, the next chance for snow (40-60% chance for
accumulations central and south) will come with a quick moving
shortwave on Thursday. While this may change in the coming days,
an inch or two of snow looks likely in central to southern
Iowa. And with colder air in place, snow will be the only
precipitation type.
By the weekend highs will be in the teens with lows falling below 0
and wind chills even lower. This means today is likely the last time
we will see temperatures above 32 for the foreseeable future. A
more robust system looks to impact the area by this coming
weekend/early next week, however significant model differences
still exist at this range resulting in lower confidence in the
details.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 623 PM CST Mon Dec 30 2024
Mainly rain showers at the start of the period over southern and
central Iowa will switch to snow this evening before ending in
most areas by sunrise Tuesday. Ceilings and visibilities through
tonight will be IFR or lower. Over northern Iowa, areas of
fog will persist with LIFR restrictions possible, particularly
at MCW. Visibilities will improve through Tuesday morning across
the state with ceilings gradually improving from IFR to MVFR
through the day from west to east.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Hagenhoff
AVIATION...Ansorge
Area Forecast Discussion
National Weather Service Green Bay WI
610 PM CST Mon Dec 30 2024
Updated aviation portion for 00Z TAF issuance
.KEY MESSAGES...
- Patchy dense freezing fog could produce hazardous travel
conditions tonight, mainly over central and north-central
Wisconsin. A Dense Fog Advisory has been posted for Marathon,
Portage, and Wood counties until midnight tonight due to dense
fog with visibilities of 1/4 mile or less.
- Sub zero wind chills are likely Thursday, Friday, Saturday and
Sunday nights across most of the region.
&&
.DISCUSSION...
Issued at 216 PM CST Mon Dec 30 2024
Short Term...Tonight and Tuesday
The latest RAP analysis and satellite/radar imagery show
disjointed shortwave energy moving east across the northern and
central Plains and low pressure over Kansas. Mid and high clouds
are already sliding into western WI ahead of these impulses. A
weak high pressure ridge axis extends from northern Minnesota,
across southwest Wisconsin and to the Ohio Valley. Low stratus and
dense fog continue within the weak wind fields of the surface
ridge, mainly across western Marathon, and Wood and Portage
counties. The leading edge of the stratus/fog is moving very
slowly east as it runs into drier air and solar insolation over
eastern Wisconsin. A recent report suggest dense fog is returning
into Portage county so will expand the Dense Fog Advisory there.
Further north, another area of stratus is surging south over the
Upper Peninsula and far northern WI. Fog potential and trends are
the main forecast concern.
Fog potential and trends: With nocturnal cooling and light wind
fields, think fog is likely to make a comeback and spread across
central and north-central Wisconsin this evening. There will be
more clouds in the mid-levels tonight and boundary layer wind
directions shift to the north, but because winds are light (less
than 4 kts), think favorable conditions for dense fog will remain.
It`s possible that the dense fog advisory will need to be
expanded later today across the remaining parts of central and/or
north-central WI.
As low pressure slides across the mid-Mississippi Valley, guidance
indicates a slight tightening of the pressure gradient and
boundary layer winds that could improve visibilities overnight.
Models generally show this gradually occurring after about 2-3 am
tonight. Confidence is low for trends/timing by this time.
Rest of the forecast: A northern stream shortwave will push a weak
cold front across central and north-central Wisconsin from late
Tuesday morning through Tuesday afternoon. If visibilities have
not improved prior to the arrival of this front, observations show
fog will lift following frontal passage. In addition, models
indicate weak ascent and a ribbon of moisture along the front that
could lead to light snow and flurries. Little to no accumulation
is expected. Highs will range from the upper 20s to middle 30s.
Long Term...Tuesday Night Through Monday
The main concerns for the extended period will be the arrival of
colder air through the end of the work week, which may be
accompanied by some light snow in the middle of the week.
Attention then turns to the passage of a larger system through
central CONUS late in the weekend into early next week.
Precipitation...
The first chance for some light snow in the extended arrives
overnight New Year`s Eve as a weak upper trough accompanies the
arrival of some colder air in the region. Forcing and upper
support appear weak during this event and unlikely to support much
beyond some light showers, so while a brief dusting is possible,
no travel impacts are expected.
The second chance will be through the end of the week, as colder
air pushes in from the northwest, which may yet bring some lake
effect into northern Wisconsin by the end of the week. As of this
forecast however, wind direction remains unfavorable for better
coverage so all of Wisconsin but perhaps far north-central along
the Upper Peninsula border remains dry.
Finally, attention then turns to the potential for a strong low
pressure system Sunday night into Monday. Ensemble guidance
remains generally aligned south of the region with this system in
the ECMWF and Canadian, but the GFS would bring some more
widespread snow reaching into Wisconsin. Individual members in
each ensemble still have a wide spread in solutions, keeping
confidence on this system low. Thus, kept the low pops for Sunday
night into Monday. Will continue to monitor this system as we get
closer, as this does have the potential to be the next widespread
snowfall and is currently the only significant chance for
precipitation in the forecast.
Temperatures...
Colder air arrives to start off 2025 as high temps head towards
the teens to low 20s for the end of the work week through the
weekend. Model agreement is fairly good on low temperatures during
this time getting into the single digits during the overnight
hours, which will bring sub- zero wind chills in the period. The
coldest nights are currently expected to be Friday night and
Saturday night, which may yet see air temperatures drop below
briefly below zero in the coldest spots of the northwoods.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 607 PM CST Mon Dec 30 2024
IFR ceilings will expand from the west and north overnight,
reaching a IMT to CLI line. LIFR ceilings (400 feet or less) and
vsbys (3/4 mile or less) are expected at AUW, CWA, MFI, ISW, PCZ,
Y50 and possibly RRL. Further east skies will be mostly clear this
evening, with MVFR ceilings arriving by daybreak.
Tuesday should have IFR ceilings through 18z west of a IMT to PCZ
line, improving to MVFR in the afternoon. MVFR ceilings are expected
to the east. An upper level disturbance could produce a dusting of
snow as it moves across the area during the late afternoon and
evening hours.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until midnight CST tonight for WIZ030-035-036.
&&
$$
DISCUSSION.....MPC/Uhlmann
AVIATION.......RDM
Area Forecast Discussion
National Weather Service Grand Rapids MI
944 PM EST Mon Dec 30 2024
.KEY MESSAGES...
- Areas of Fog Tonight
- Rain/Snow Mix Turning to Snow Tuesday; Snow Showers Wednesday
- Occasional Flurries and Light Snow Showers Thursday-Sunday
- Chance for Snow on Monday
&&
.UPDATE...
Issued at 944 PM EST Mon Dec 30 2024
Water vapor imagery shows an upper level shortwave sliding east
from KS/MO at 900pm. By 12Z, the upper wave will be moving into
the Ohio Valley from IL into IN/KY. The surface reflection of the
upper wave (a 993mb low) will be moving from Central IL into
Central IN at 12Z.
The precipitation field is forecast to begin to move into far
Southwest Lower Michigan late tonight. We are not expecting
significant precipitation in the forecast area through 12Z, but it
is right around that time that the steadier more widespread
precipitation moves in. Through daybreak, the precipitation will
likely be in the form of rain. It is not until after daybreak that
the column cools a bit and we begin to more significantly mix
with snow.
The fog threat looks a bit less as hourly guidance has come in
tonight. So, at this point we are not expecting dense fog.
Certainly some patchy fog, but our consensus of short term model
guidance has backed off on the fog in terms of extent and
impact/visibility.
Temperatures at daybreak will be a few degrees either side of the
freezing mark. A few upper 20s possible across Central Lower MI
and middle 30s down towards I-94.
&&
.DISCUSSION...
Issued at 323 PM EST Mon Dec 30 2024
- Areas of Fog Tonight
At a minimum, a stratus deck is expected tonight with abundant low
level moisture in the lowest 1000-2000 ft of the atmosphere per 12z
HRRR Bufkit soundings. These model soundings also support fog
development with winds going calm, prior to the area of low pressure
arriving later Tuesday morning. The greatest risk for fog appears to
be from 10pm tonight through 6am Tuesday morning. The most likely
region for this to occur will be from I-96 to I-94, though some
areas just north of I-96 may receive fog as well. NBM visibilities
reach 1/2 mile or less, with HRRR visibilities showing areas of 1/4
mile or less. We will have to assess whether or not a Dense Fog
Advisory will be needed later. Allow extra time to reach your
destination for any late night or early morning travel.
- Rain/Snow Mix Turning to Snow Tuesday; Snow Showers Wednesday
Any morning fog will begin eroding as an area of low pressure and
its associated precipitation arrives Tuesday morning. This system,
currently across KS and OK, will move ENE into IN and OH by
tomorrow. The previous discussion hit on the challenges facing this
system in producing impactful snowfall accumulations. Current road
temperatures are in the 40s, our ground is saturated, and minimum
air temperatures tonight are expected to drop to near freezing. When
it begins precipitating Tuesday morning, a rain/snow mix is likely
before transitioning to snow for most locations near and south of a
Grand Rapids to Alma line. Indeed, 12z HRRR soundings show that snow
is the dominant precipitation type for the majority of this event,
but changeovers between rain and snow and then back again could
certainly occur.
But with air temperatures likely staying just above freezing,
coupled with warm ground temperatures, it would take heavy snowfall
rates to overcome those factors. There is a low but non-zero
probability that a narrow region somewhere between I-96 and I-94
could locally achieve this, with perhaps 2"-4" of snow accumulating
(ie. the 12z Nam3km Bufkit overview using the Cobb snow technique
for LAN, where the Nam is depicting -12 to -15 ubar/s of vertical
motion within the DGZ). For most locations, an inch or less will
likely fall but 1"-2" could stick where snow is steadier. Overall,
only minor impacts to travel are expected with this event and no
headlines are planned at this time.
High temperatures Wednesday (near freezing) will occur early in the
morning before falling into the upper 20s during the day. This
occurs as cold air advection is underway at 850 mb, with
temperatures there falling to the -10C to -13C range. Snow showers
on the leading edge of an upper trough swinging through the region
will cross Lake Michigan in the 06z-12z Wednesday time frame,
providing a short window for the seeder-feeder mechanism to begin.
Lake enhanced snow showers appear likely Wednesday morning
transitioning to light lake effect snow showers Wednesday afternoon.
This doesn`t look like a very significant event, primarily because
of the shorter duration of deeper moisture beyond 5000 ft and weaker
omegas within the DGZ, but current WPC probabilities for 1" or more
on Wednesday are 60-70% near and west of US 131. Total accumulations
are favored to be 1"-2" for locations within the NW to WNW snow
belts.
- Occasional Flurries and Light Snow Showers Thursday-Sunday
Significant snow is not anticipated from Thursday through Sunday
with mainly light lake effect snow showers expected, though we`ll
need to keep an eye out for Friday into Saturday for possibly
heavier activity. Model RH from the 925-850mb layer over Lake
Michigan is shown to ebb and flow during this period, leading to
mainly light snow shower activity. However, the 12z GFS does show
another upper trough and vort lobe moving through Friday with better
lift shown within the DGZ for our lakeshore counties, and this could
flare up snow shower activity Friday into Saturday.
- Chance for Snow on Monday
Ensemble and deterministic model guidance have shown a plethora of
outcomes for a potential synoptic snow event next Monday, with the
big question being how quickly will upper troughing move out of the
region to allow for a potential mid level wave or closed low to
approach the Great Lakes from the Central Plains Sunday into Monday.
There are also phasing implications with how deep another northern
stream trough digs as this system moves out of the Plains. It is
certainly within the range of ensemble solutions for a synoptic snow
event to impact Lower Michigan, but the system may stay south of the
region as well. Looking at the 00z Grand Ensemble (ECE/GEFS/CMC),
40% of the membership has snowfall of 2" or more and 10% has 6" or
more. A quick look at the individual ensemble systems from the 12z
runs indicates the GEFS is much further north with a low track than
the ECE and CMC ensemble means. At this point an impactful snow
event is not the most likely solution, but within the realm of
possibility. We will see how this system trends with time.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 626 PM EST Mon Dec 30 2024
Clouds will increase overnight as low pressure moves across
Indiana. There`s a good signal for IFR fog tonight prior to the
onset of mixed rain/snow Tuesday morning. Cigs aob 500 ft are
expected at the I-96 terminals Tuesday morning. Cigs will
eventually fall below 1k ft at the I-94 terminals too during the
afternoon. Little, if any, improvement is expected prior to the
end of the period.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 7 AM Tuesday to 5 AM EST Thursday for
LMZ844.
&&
$$
UPDATE...Duke
DISCUSSION...Hoving
AVIATION...04
Area Forecast Discussion
National Weather Service Raleigh NC
1000 PM EST Mon Dec 30 2024
.SYNOPSIS...
Pacific high pressure will linger near the South Atlantic coast
tonight. A frontal system will move across the Ohio Valley and
Middle Atlantic Tuesday and Tuesday night. Continental Polar high
pressure will follow and build across the Southeast Wednesday and
Thursday.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 1000 PM MONDAY...
High pressure over the region has kept skies clear this evening.
There are some mid/high clouds over TN/WVA. These should skirt by to
our north overnight. There is expected to be excellent cooling
overnight with lows in the mid 30s to mid 40s as high pressure moves
slowly east toward the Coastal Plain late. Roxboro was already
reporting 36 and Halifax 37 at 1000 PM. The dew points were in the
mid 30s N to mid 40s SE already - and with additional cooling
overnight expect some ground fog in the rural areas. In addition,
some stratus is forecast to arrive with the renewed WAA in the west
toward daybreak as the surface high slowly exits east.
&&
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 355 PM Monday...
A potent mid/upper low will move NE across the OH Valley on Tuesday,
opening up into a shortwave as it reaches the Lower Great Lakes and
Upstate NY on Tuesday night. An associated surface low will move
from IL/IN on Tuesday morning into the northern Mid-Atlantic and
southern New England on Tuesday night. This will push a warm front
north through central NC on Tuesday morning, then a cold front on
Tuesday evening. While mid-level height falls over central NC will
be fairly strong, on the order of 5-10 dam in 12 hours, moisture
looks fairly meager this far displaced from the low and largely
confined to the lowest ~850 mb. Instability also looks very minimal
to non-existent (maybe 100-200 J/kg of SBCAPE at most).
After any fog lifts by late morning, this system will bring a chance
of showers to central NC Tuesday afternoon and early evening.
However, coverage should be isolated to widely scattered, with the
highest POPs (low chance) across the far northern Piedmont,
decreasing to slight for much of the rest of central NC. Amounts are
expected to only be 0.05" or less on average, with isolated amounts
of one to two tenths of an inch possible. High-res guidance is in
fairly good agreement on timing, with showers beginning to enter the
NW Piedmont around 16-17z, traversing east across the rest of the
region through the afternoon. Due to the tight pressure gradient
from the surface low, S/SW winds may gust up to 20-30 mph in the
afternoon. Much of the high-res guidance shows Tuesday`s
temperatures being kept down some by the low clouds and showers
especially NW, but forecast highs are still above normal, ranging
from mid-to-upper-50s around the Triad to mid-to-upper-60s in the
far SE.
Another line of showers associated with the cold front may move east
across the area in the early evening until about 03z, especially if
the HRRR verifies. Skies will then clear out and much drier air will
move in on Tuesday night behind the front, so no rain is expected by
the time we ring in the new year at midnight. However, winds will
turn westerly and remain elevated, especially along and immediately
behind the front. Low temperatures will still be above normal (upper-
30s to mid-40s).
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 310 PM Monday...
From New Year`s Day into the weekend we will return to an extended
period of cool and dry northwesterly flow. Wednesday afternoon
should be gusty with high temperatures in the low to mid 50s. Lows
will be near normal in the upper 20s to low 30s. The end of the work
week should be cooler with highs in the mid 40s to low 50s. Lows
Thursday night are expected to be in around 30, dropping to the mid
to upper 20s Friday night. Another blast of dry Arctic air should
reach the area by Saturday, dropping temperatures even further over
the weekend. Saturday should have highs in the low to mid 40s with
lows in the low to mid 20s. Sunday should have similar high
temperatures, with lows warming to the mid 30s.
Late Sunday night though Monday a deep trough will move through the
region, bringing the next chance for precipitation. It is currently
unclear how much/if any of the precipitation will be frozen as
models differ in timing and temperatures. However, this appears to
follow a Miller B type pattern, which can be conducive to frozen p-
types in our northern counties, so a chance of freezing rain and snow
were introduced mainly from 6-12Z early Monday morning, but as
models come to better agreement this is likely to change. Any frozen
precipitation that does fall is likely to be very short lived.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 700 PM Monday...
High pressure will favor calm and VFR conditions for most of
tonight, then the development of areas of radiation fog across the
Carolinas Tuesday morning. Increasing moisture, ahead of a frontal
system that will move across the Middle Atlantic, will result in a
good chance of MVFR ceilings and widely scattered showers across the
NC Piedmont Tue, especially at INT/GSO, with VFR conditions
otherwise and elsewhere. Sly surface winds will also strengthen and
become gusty into the 20s kts from late morning through afternoon.
Outlook: Marginal low-level wind shear will be possible Tue evening-
night, owing to the presence of a well-mixed layer that will include
wswly winds as high as 40 kts at 1500-2000 ft AGL, atop a shallow,
near surface stable layer characterized by much lighter winds.
An Arctic cold front will be accompanied scattered showers and
following strong and gusty nwly surface winds Fri-Fri night.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...MWS
NEAR TERM...Badgett
SHORT TERM...Danco
LONG TERM...Helock
AVIATION...MWS
Area Forecast Discussion
National Weather Service Topeka KS
556 PM CST Mon Dec 30 2024
.KEY MESSAGES...
- Light rain turns to rain/snow mix later this evening mainly north
of I-70. Little to no snow accumulation is expected.
- Wind turns breezy tonight with cooler weather to follow for much
of this week.
- Next system to monitor comes next weekend, which could bring
wintry weather to the region.
&&
.DISCUSSION...
Issued at 253 PM CST Mon Dec 30 2024
20Z water vapor imagery shows a shortwave trough making its way
across the Central Plains, with the associated sfc low in southeast
KS moving into southwest MO. Light radar returns have begun to fill
in across eastern KS, and while the highest rain chances remain
focused north of I-70, they should continue to increase this
afternoon as vertical profiles become more deeply saturated.
Additionally, the sfc cold front coming from central KS will bring
brisk northwest winds this evening with CAA strengthening into
Tuesday. The HRRR and RAP suggest wind gusts may flirt with advisory
criteria in our far southwestern counties, but think winds of this
caliber remain too isolated and short-lived to warrant an advisory
at this time. As colder air advects into the area behind the front
this evening, there is still an opportunity for snow to mix in with
rain, primarily north of I-70 starting around 8-9pm and exiting west
to east overnight. Still not expecting snow accumulations to cause
issues, but it is worth noting that the HREF has at least a 50%
probability for an inch of snow in northern locations along the Hwy
36 corridor. Think warm sfc temperatures in the mid 30s would make
it difficult for most snow to accumulate outside of grassy surfaces,
especially with temperatures likely not falling below freezing until
after precip ends.
Winds should slowly decrease throughout the day Tuesday, although
CAA will keep temperatures limited to the mid 30s to low 40s. The
pattern favors cooler weather to continue through the work week with
highs in the 30s and 40s and lows in the teens and 20s, as northwest
flow aloft continues to filter in cooler air. There is another
perturbation in the flow that looks to move through the region
Thursday, and while rain chances are favored just to the northeast
of the area, deterministic runs are placing some light QPF in the
area so would not rule out some rain in far northeast KS Thursday
morning.
The main weather system in the forecast period comes this upcoming
weekend, particularly on Sunday. However, long-range guidance shows
a 15-20 degree spread in temperatures Saturday and Sunday due to
variations in track and timing of the system. So far, the ECMWF has
shown a more southerly track with cold air moving in faster, while
the GFS has warmer temperatures to start and a slower-moving system.
These differences lead to low confidence in precipitation type, but
the potential exists for wintry weather in the region with this
system, so it will certainly bear monitoring over the next several
days.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 532 PM CST Mon Dec 30 2024
Light rain and drizzle will continue into the early morning
hours of Tuesday. MVFR ceilings will become IFR to LIFR through
the evening hours and remain below 1000 feet through 14Z TUE.
Ceilings will rise to MVFR levels through the late morning
hours. Ceiling should rise above VFR criteria during the early
afternoon hours of Tuesday. Northwest winds will increase to 14
to 18 KTS this evening with gusts of 25 to 35 KTS through the
night Northwest winds will gradually diminish Tuesday
afternoon.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Picha
AVIATION...Gargan