Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/06/25
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
907 PM CST Sun Jan 5 2025
.KEY MESSAGES...
- Light snow chances (20-40%) return to central SD Monday and
expand into portions of eastern SD on Monday night. Minimal snow
accumulations (< 0.5") expected.
- Below normal temperatures (by 10 to 20 degrees) will remain in
place through Tuesday before a warm up to near-above normal
(5-10 degrees above normal) the latter half of the week.
- A couple of clipper-like systems tracking through the region
will potentially produce light snow opportunities (~20% chance)
on Thursday and Saturday.
&&
.UPDATE...
Issued at 906 PM CST Sun Jan 5 2025
Current forecast is on track, therefore no changes made at this
time.
&&
.SHORT TERM /THIS EVENING THROUGH MONDAY NIGHT/...
Issued at 122 PM CST Sun Jan 5 2025
A partly/mostly sunny and cold afternoon across central/northeast SD
and west central MN, as Canadian high pressure is settling in over
northeast ND and southern Canada. A ridge associated with this high
has sunk south over central SD and brought abundant dry air below 15-
20kft, as seen on 12Z KABR sounding and RAP analysis. There`s still
some high cirrus over the area, but thus far the mid cloud decks
have been staying off to the west of the area. 1pm temperatures are
in the single digits to low teens across the area.
Main concern for the next 12 hours is how quickly the mid-high
clouds move into the area tonight. Models are pretty aggressive on
them moving in tonight, but they`re pretty spotty up stream, so the
cloud cover forecast could be a touch overdone. That could lead to
temperatures dropping off pretty quickly tonight under light winds.
Current forecast has lows in the single digits below, but if the
skies stay clearer for a longer period of time, would expect to see
some teens below zero in the James River valley.
Focus then turns to the shortwave currently in Alberta that will
drop southeast across the area late tomorrow afternoon and through
Monday night. This shortwave and associated 850-700mb trough will
bring the potential for light snow to the area as cold air advection
increases over central SD behind the trough. Deterministic/ensemble
soundings showing the entire cloud profile within the DGZ, but only
limited lift/omega associated with it. Thus, expect there to be some
light/occasional snow occurring first over north central SD on
Monday, then spreading southeast over areas along/west of the James
River. One question is how far east the snow will go. EC-Ens has 45-
70% of its members showing some light snow east to Aberdeen and
Watertown for late Monday afternoon into Monday night. While
GEFS/GEPS don`t go quite as far east (limit it to James River and
westward), they also have higher probs of measurable snow. So while
amounts aren`t much (0.01-0.03" liquid equivalent), do feel like it`s
worth mentioning some precipitation chances, so have bumped up PoPs
to the low end chance values. Really looks like a high PoP, low QPF
situation, so wouldn`t be surprised if future shifts need to
increase PoPs further.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 122 PM CST Sun Jan 5 2025
Center of the high pressure center will track south on Tuesday and
the progression of the trough to the east out of the region will
allow a new airmass to take hold. Temperatures will flip from below
normal to above normal Wednesday and Thursday before cooling back
down slightly to normal for next weekend.
No major systems are expected to impact the forecast area through
next weekend, but there will be a couple instances where some light
precipitation will be possible. The first instance is in the
Thursday to Friday time period where a shortwave trough will move of
the area and develop a surface low to the northeast. There is still
a lot of uncertainty in the amount of moisture aloft and whether or
not it will be enough to keep the profile saturated. Even if there
is moisture, the highest totals looks to stay to the north for the
forecast area, and only a couple tenths of snow may fall. NBM
probabilities for measurable snow (0.1" or higher) hold at a broad
20-40% over the forecast area, with some slightly increased chances
(up to 50%) over the Prairie Coteau.
On Saturday the front side of a ridge will bring a jet streak
overtop part of the northern plains and create the aforementioned
second chances for precipitation. The jet streak currently looks to
be lined up over western South Dakota in the deterministic models,
but given the time range a shift is very likely. NBM probabilities
of measurable snow once again range from 20-40%, with a swath up to
50% west of the forecast area.
A final note on these low-QPF/light snow events is that for both the
Thursday and Saturday systems, the GFS and Euro ensembles show
significantly higher chances than the NBM (70-90% across the
forecast area). While the NBM has historically struggled in these
light snow scenarios in this area, the values resolved in the
GFS/Euro ensembles seem quite high given the time range and
uncertainty present. At this point have opted to stick with the NBM
PoPs in the forecast, but adjustments upward may need to be made
when the events draw closer or some of the uncertainty is resolved.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 524 PM CST Sun Jan 5 2025
Terminals KABR,KATY,KPIR,KMBG
For the most part, VFR conditions will prevail across the area
tonight and through the day Monday. The exception will be across
central South Dakota late in the TAF period when some MVFR cigs
and MVFR vsbys in light snow are expected, affecting KMBG and
KPIR.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...Parkin
SHORT TERM...SRF
LONG TERM...BC
AVIATION...Parkin
Area Forecast Discussion...DELAYED
National Weather Service La Crosse WI
957 PM CST Sun Jan 5 2025
.KEY MESSAGES...
- Scattered flurries where low clouds are located mostly east of
the Mississippi River tonight.
- Outside of flurries, meaningful snow chances remain low
through midweek.
- Below normal temperatures through Wednesday with a return to
more seasonable levels for the end of the week into the
weekend.
&&
.DISCUSSION...
Issued at 215 PM CST Sun Jan 5 2025
Tonight - Monday:
Locally, fairly quiet conditions have continued into the day today
as surface high pressure remains centered over the Dakotas while a
significant storm system moves eastward across the Ohio Valley to
the Mid-Atlantic. Have been watching an area of lower clouds off
Lake Superior that have been drifting southward into north-central
Wisconsin early this afternoon. Model progs have shown a continued
signal in increasing low level moisture into the local area this
evening. Though, guidance does vary on the depth of this low level
moisture, with the RAP being the more aggressive. Overall, all this
to say some scattered flurries under these clouds cannot be ruled
out, as has been observed already across northern and north-central
Wisconsin this afternoon. Otherwise, below normal temperatures will
follow into the start of the work week, with lows tonight in the
single digits to around 10F and highs Monday in the teens to low
20s.
A short-lived ridge over the Upper Mississippi Valley is forecast to
break down Tuesday night with troughing for Tuesday night into
Wednesday. Once again, short-lived ridging builds in for Thursday,
however already by Thursday night, a stronger trough from Manitoba
and Ontario deepens southward into the Upper Midwest through Friday
night. This trough swings eastward through the Ohio River Valley
and eastern Great Lakes with weak ridging, then another trough
pushing eastward from the Plains Saturday night into Sunday.
Ensemble probabilities for measurable snow remain low for Wednesday
(0-15% - however northern Taylor Co is 15-40%). The 05.00Z
GEFS/ECS/Canadian ensembles have a 55 to 85% probability for
measurable snow, however the 05.12Z deterministic EC was a bit
drier, so stay tuned. The ensembles show a 40 to 60% probability
for the Saturday night into Sunday trough, however there are
still disagreements with the weekend system on timing and
strength as well. Temperatures remain below normal through
midweek, however return to seasonable levels for the end of the
week into the weekend.
&&
.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 954 PM CST Sun Jan 5 2025
While VFR conditions will more likely than not prevail, some
short term guidance has been hinting at ceilings in the
1500-2500 foot range from around 15z to 19z in west central
Wisconsin Monday, including at LSE. Since this has been a recent
trend that is only seen in some models, have elected to include
a SCT mention for now as a heads up. Otherwise, winds generally
out of the north with a bit of cirrus should occur over the next
24 hours.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...EMS/Zapotocny
AVIATION...Ferguson
Area Forecast Discussion
National Weather Service Columbia SC
725 PM EST Sun Jan 5 2025
.SYNOPSIS...
Moisture spreads into the area tonight leading to increasing
shower coverage as a cold front approaches from the west.
Strong, gusty winds are likely on Monday along with some brief
heavy rain as this front moves through, with much colder air
filling behind this for the rest of the week.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Key message(s):
- Strong winds and rain move into the area early Monday morning
Well, our streak of quiet weather is coming to an end tonight.
Southwesterly flow has increased dramatically over the past
12 hours as a robust synoptic cyclone translates eastward over
the Mid-Mississippi valley. 850 hPa flow has increased quickly
and is forecast to continue doing so over the next 12 hours or
so as the cold front approaches the region. An increase in
moisture is occurring with this increase in flow, and
isentropically forced showers have developed across central and
northern Georgia, moving northeastward currently. Much of this
is not making it to the ground initially but eventually the
persistent showers should be able to overcome the large
dewpoint depressions that are out there in the obs. The best
isentropic ascent is forecast to remain across the central and
northern portions of the forecast area and into the upstate, so
PoPs have been raised into the low-mid chance range here. This
batch of isentropically forced precip is likely to shift to our
north and northeast between 06z and 09z, with some isolated
showers lingering in a strong warm advection regime ahead of the
cold front.
PoPs look solid later in the night, though may have to touch up
the speed of the cold front and moderate to heavy precipitation
along it just a tad. Recent observational trends suggest it may
arrive slightly earlier than forecast by most guidance right
now. Otherwise, the forecast is mostly on track through tomorrow
morning. Temps will likely only fall marginally tonight given
expected cloud cover, though they should be aided by wet-bulbing
with light precip and associated evaporation. It wouldn`t
surprise me if temps bottomed out over the next 5-7 hour before
bumping up again as we enter the "warm sector" ahead of the
approaching cold front. The last thing we are watching closely
is what that warm sector looks like just ahead of the front.
Winds are forecast to be howling just above the surface from
10z-16z, with winds around 60-70 knots forecast around 3000
feet. However, a strong inversion is expected to keep the
majority of these in check, with only breezy to blustery winds
expected in the morning. There is an outside chance that a
robust shower is able to mix some of these winds down, which
would result in strong gusts. But for now, that "warm sector"
looks very stable, which should impede the strongest winds from
actually reaching the surface ahead of the front & mid-level
trough axis.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
- Strong frontal passage Monday will bring some heavy rain and gusty
winds throughout the day.
- A Wind Advisory is in effect from 6am through 7pm Monday.
By 7am, the strong front will be pushing into the western Midlands
with expected gusty winds within the prefrontal trough. HREF members
are fairly consistent in bringing the showers (possibly weak
convection) through the region from roughly 7am through 12pm. There
will not be the typical strong, fast cold pool propagation that we
get with mature convective, so the HREF speed bias should not be as
slow as it sometimes is. The winds ahead of and behind this front
will be the main story, with a highly anomalous 850mb jet within the
prefrontal trough of 60-70 knots; over the 99.5th percentile for
wind speeds in both the EC and NAEFS. EC EFI has continued to
increase, now sitting between 0.8-0.9 for surface wind gusts but
relatively minimal Shift of Tails. So confidence is high in notable
wind event across much of the area but very unlikely to be a record-
setter. HREF wind gusts have now pushed the mean over 50 mph, with
the HRRR the weakest around 40 mph. In the same thinking, NBM QMD
max wind gusts for Monday now show a median of 45 mph. Now while
guidance is certainly buying a strong wind event, low level
stability ahead of the showers underneath the 850mb jet will
help limit the gust potential, likely more than guidance shows.
So blending this thinking in, wind gusts to around 40-45 mph
look likely for a period Monday morning, between 7am and 10am.
Confidence is lower across the northern half of the area, but
enough shower activity and associated mixing should push the
wind gusts up to the SC-NC border.
The line of showers will move out by early afternoon making way for
a strong cold advection regime to setup through the afternoon.
Guidance is a bit weaker for the afternoon cold advection related
gusts than the prefrontal trough in the morning. But as is typical
with cold advection, guidance is probably too low and under-
mixed considering the unidirectional low level shear, dry
adiabatic lapse rates, and low level of max boundary layer
winds. While there will likely be a brief period of higher gusts
as dry air intrusion develops directly behind the front,
generally thinking gusts between 35-40 mph will persist
throughout the afternoon and into the evening.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
- Cold and very dry air will fill in for remainder of the week.
Strong cold and dry advection will continue throughout Tuesday and
usher in well below average temps for the remainder of the week.
NAEFS and EC EFI highlights the Tuesday-Friday period clearly with
well below average heights, temps, and moisture; bottom 10th for
heights and temps in the NAEFS and 0.7-0.8 in the EC EFI. As in
typical with these airmasses, guidance steadily moderated with the
extreme cold potential as we got closer. Having been consistent now
for the last few days, it looks like this will be 5-10th percentile
type airmass with daytime highs and overnight lows 10-15 degrees
below average. Depending on exactly where the surface high pressure
settles, we could approach Cold Weather Advisory criteria a couple
nights this week, but confidence is currently low in getting temps
that low.
But late this week, confidence continues to increase in a developing
GoM surface low that will push into the area sometime Friday-
Saturday. GEFS and EC suites appear to be converging (at least as
much as reasonably possible for 5+ days out) on pulling this
surface low east-northeast and over our area. There has been a
notable trend in the last couple ensemble suites to favor a
single low pressure center, with a more southerly track, rather
than a pure Miller B type setup with a coupled low across the TN
Valley. While confidence is increasing in this potential,
frozen precip chances are still extremely uncertain as in
typical in this range due to both the borderline thermodynamics
in place, possibly surface wedging, and low track. Hopefully
guidance continues to converge on at least low track so that
portion of the forecast can get reasonably cleared up but
specifics about precip type, timing, etc. will all take several
days to even have a decent idea.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Rain, strong winds and restrictions likely Monday morning.
Light winds this evening with VFR mid level ceilings expected.
Radar is showing patchy light showers in the area but appears
limited and more focused in north GA into the Piedmont/Upstate
SC. Visibility restrictions not expected overnight. Virga more
likely due to dry low- levels.
A strong cold front will approach the forecast area late
tonight along with a line of widespread showers developing
around 12z. Low level wind fields increase significantly after
06z as a 50 to 70 kt Low-Level jet moves across the Southeast
ahead of the front below 5000 ft. Strong Low-level wind shear
is a given with 2000 ft wind speeds from 40 to 60 kts between
06Z and 18Z. It may be difficult to mix down these values,
particularly in the morning, due to stable low levels but gusts
near 30 kts are likely with gusts near 40 kts possible. The
strongest gusts are expected to be late morning into the
afternoon as the front moves through and in the cold advection
behind the front. Winds will shift from SW to W on Monday
afternoon behind the front with gusts continuing into the
evening.
EXTENDED AVIATION OUTLOOK...Widespread restrictions unlikely
until Friday when the next low pressure system moves into the
Southeast.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...Wind Advisory from 6 AM to 7 PM EST Monday for SCZ016-018-
020>022-025>031-035-037-038-041-115-116-135>137.
GA...Wind Advisory from 6 AM to 7 PM EST Monday for GAZ040-063>065-
077.
&&
$$
Area Forecast Discussion
National Weather Service Charleston SC
1026 PM EST Sun Jan 5 2025
.SYNOPSIS...
A cold front will quickly move through the region on Monday,
followed by cold high pressure into late week.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
A warm front will lift across the forecast area tonight. Behind
the front, SSW winds should gradually increase across the
forecast area, resulting in WAA. The combination of the WAA and
thick cloud cover should result in warming temperatures through
the rest of the night. A sprinkle or two may track across the
CWA tonight.
Based on recent high resolution guidance and HREF information
indicates that gusts 40 mph or greater is likely after sunrise
Monday across Charleston County. A Wind Advisory has been issued
for Charleston from 8 AM to 4 PM.
Lake Wind: Given the increasing pressure gradient and winds
later tonight, have maintained the Lake Wind Advisory for Lake
Moultrie. Expect winds to reach advisory levels after 4 am or so
on Monday, and remaining through Monday night.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
Progressive southern stream short-wave over the Kansas/Missouri
border this afternoon will open and advance through the southeast
region on Monday and off the East Coast heading into Tuesday.
Attending surface low will follow suit tracking across the Tennessee
Valley to the mid Atlantic through Monday, leaving a nice corridor
of wintry weather from the Central Plains to the Mid Atlantic.
Trailing cold front will press through the southeast coastal region
during the day Monday bringing a narrow line of showers to the
forecast area primarily during the daylight hours with rainfall
amounts generally one-quarter of an inch or less. While winds aloft
with this system remain impressive /0-6km bulk shear values in
excess of 65 knots Monday afternoon ahead and along the front/,
overall instability remain anemic and thunderstorm probabilities
remain very low. Nonetheless, any stronger convection that manages
to develop and organize could warrant monitoring for strong gusty
winds (reference SPC Day 3 Convective Outlook).
Meanwhile, given the very strong wind profiles mentioned above, a
breezy-windy day is anticipated. Bufkit GFS soundings show mean
mixed layer winds of 30-35 knots across inland areas, a proxy for
top end gust potential. Stronger mean mixed layer winds are noted
across the coastal waters running 35-45 knots, highest off the SC
coast. Those values are in decent agreement with blended guidance
gust probabilities and MOS products. That said, there are higher
gust values (40+ knots) depicted by the 12Z/18Z HRRR and 12Z HREF
for Monday, which is a bit concerning. But given the strong lower
level inversion, cloud cover, eventual rain moving in and
under performing wind gusts upstream this afternoon, prefer to keep
wind gusts under Wind Advisory criteria at this time...except right
along the SC coast. Later shifts will need to further assess.
Clearing skies and cooler temperatures anticipated on Tuesday
and Wednesday with highs only in the 40s to lower 50s.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Large scale troughing remains dominant across eastern NOAM into the
Atlantic through much of the long term period with anomalously cold
air lingering across much of the eastern CONUS. The mid to late week
period will be dry, albeit on the cold side with highs in the middle
40s to lower 50s and lows largely spanning the 20s. There will be a
few overnight/early mornings where apparent temperatures may skirt
Cold Weather Advisory criteria, particularly Thursday morning. Will
deal with those one day at a time.
Meanwhile, a pseudo split flow pattern emerges across the western-
central CONUS around midweek as strong short-wave energy digs into
the southwest CONUS/northern Mexico region. Short-wave trough
briefly becomes cutoff/elongated late week before phasing with the
northern stream and advancing eastward through the southern
states/northern Gulf region late week and into the weekend. This is
expected to gin up surface low pressure along the northern Gulf
Coast region late week, which will then pivot and track up along the
Georgia and South Carolina coasts late Friday into Saturday bringing
a round of precip through the region. With ample cold air across the
southeast region, this continues to present winter precip type
concerns for the local forecast area. 05/12Z long term deterministic
and GEFS guidance has trended slightly cooler in the overall thermal
profiles suggesting at least some potential for a touch of wintry
precip inland on Friday...before warmer air eventually gets driving
into the region later Friday into Friday night. However, still lots
of uncertainty with this system and for now...prefer to maintain all
rain for the local forecast area.
&&
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
0Z TAFs: A warm front will lift across the terminals tonight,
with strengthening SSW winds expected through daybreak. Based on
forecast soundings and MOS, gusts may rapidly reach the mid 20s
around dawn. In addition, LLVL jet is forecast to exceed 50 kts
as early as 12Z, remaining until a line of showers sweeps
across the terminals early Monday afternoon. Each TAF will
feature a mention low level wind shear from around dawn until
17Z. Sfc winds should peak just ahead of the arrival of the rain
band/cold front, peaking around 17Z. High resolution guidance
indicates a solid band of showers, which could result in periods
of MVFR conditions. Each TAF will feature a TEMPO from 17-20Z
for 5SM and OVC030 during -SHRA. In the wake of the cold front,
winds should shift from the west by 20Z with gusts between 20-25
kts.
Extended Aviation Outlook: Flight restrictions possible at
KCHS/KJZI/KSAV Monday within showers occurring with a passing cold
front. In addition, wind gusts around 25-30 kt are possible through
Monday evening. Gusts could be stronger within showers.
&&
.MARINE...
Tonight: The waters will be between a surface ridge well to the
east and an approaching upper level trough and surface cold
front moving into GA and the Carolinas. Conditions are expected
to deteriorate rapidly overnight, especially after midnight, as
the low level pressure gradient increases ahead of the cold
front. Expect southerly winds of 15 to 25 knots with gusts to
around 30 knots most areas, especially toward sunrise. Seas will
also build rapidly, reaching 3 to 5 feet later tonight/early
Monday morning. Have raised a Gale Warning for all waters,
including Charleston Harbor, beginning later tonight.
Monday: A quick moving cold front will push across the local waters
Monday. Gale Watches have been converted to Gale Warnings for all
marine zones, including the Charleston Harbor, due to frequent SSW
gusts around 35-45 kt. The strongest gusts will target the
Charleston County nearshore waters where gusts could peak around 45
kt, which lends to a low-end chance for storm-force conditions.
Numerous showers are expected with the frontal passage, perhaps
containing a few thunderstorms in waters closest to the Gulf Stream.
Within pockets of deeper convection, strong wind gusts of 55 kt or
greater are possible. Seas will rapidly build, peaking around 6-11
ft late Monday afternoon. As the front pushes into the Atlantic
Monday night and strong high pressure builds in its wake, conditions
will be slow to improve, but eventually dropping below advisory
thresholds by Tuesday afternoon.
Tuesday through Friday: West-northwest winds will prevail through
the period with inland high pressure in place. A slight surge in
winds is possible Wednesday night into Thursday as a reinforcing
cold front pushes through the area. Per the latest forecast,
conditions looks to remain below Small Craft Advisory criteria.
&&
.TIDES/COASTAL FLOODING...
Strong southwest winds Monday could result in blow-out tides during
the Monday evening low tide along the southeast South Carolina and
southeast Georgia coast.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Lake Wind Advisory from 4 AM Monday to 7 AM EST Tuesday for
SCZ045.
Wind Advisory from 8 AM to 4 PM EST Monday for SCZ050.
MARINE...Gale Warning from 4 AM Monday to 1 AM EST Tuesday for AMZ330-
350-352-374.
Gale Warning from 4 AM to 7 PM EST Monday for AMZ354.
&&
$$
NEAR TERM...NED
SHORT TERM...Adam
LONG TERM...Adam
AVIATION...NED
MARINE...Adam/RFM
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
753 PM CST Sun Jan 5 2025
.KEY MESSAGES...
- Additional accumulating snow and gusty winds this evening
through Monday morning will result in potentially adverse
travel conditions.
- Cold temperatures each night through Wednesday night will result
in wind chill values near or slightly below zero.
&&
.UPDATE...
Issued at 749 PM CST Sun Jan 5 2025
Snow continues across central Illinois this evening and system
remains largely on track with a couple issues we`ve been working
through. Most notably, dry air on the north side of the system
with reinforcing low level dry advection has substantially delayed
precip onset along the I-74 corridor this evening. This will
result in the snow gradient on the north side of the system being
very tight and previous snow forecasts a bit overdone for this
area. Further south, snow amounts seem to be on track down through
the I-70 corridor, but we are starting to see a mid level dry
slot lift into region causing precip to either taper off or
transition to patchy light freezing drizzle in spots as we lose
ice nuclei in the column. RAP -10C to -13C layer RH shows the
drizzle potential is greatest roughly along and south of the I-72
corridor from Jacksonville through Springfield to
Champagne/Danville for the next several hours. RH increases again
in this layer (associated with the wrap-around moisture on the
back side of our low) from the west from midnight through 3AM CST
so precip should transition back over to light to moderate snow at
that point. Finally, we have received reports of very low
visibility (near white out) for parts of the area...and this may
become more common overnight as wind gusts are still expected to
increase into the 30 to 35 mph range as the last band of snow
moves across the region. Stay safe and warm, Central Illinois!
Deubelbeiss
&&
.DISCUSSION...
Issued at 240 PM CST Sun Jan 5 2025
Synoptic overview and latest radar trends:
As of 3pm, we`re observing some of the heaviest snow we`ve seen
so far this event lifting northward across the I-72 corridor. This
is due in large part to strong synoptic ascent, with a broad
500-mb difluent zone spreading in beneath a loose jet-coupling
signature. This forcing/ascent is well-aligned with deep moisture
(RH) extending through the dendritic growth zone (DGZ), resulting
in fat fluffy flakes and efficient accumulations. Radar trends
have generally been in the 30-40 dBz range across this area of
snow, and as a rule of thumb, is yielding 0.5"/hr snowfall rates.
Meanwhile, further south along and south of I-70 where heavy snow
was observed early in morning, we are now seeing a bit of a phase
change take place. Glancing at current radar trends, we see at
least partial melting of hydrometers, as evident from the 0.8-0.9
values within the Correlation Coefficient data. With the vertical
temperature profile south of I-70 now flirting with the 0C
isotherm, we should begin to observe rimed-snow or sleet in these
areas over the next couple of hours, which is not going to lead to
efficient snow accumulations.
Further north, near and along the I-74 corridor, low-level dry
air has been very slow to mix away. Sfc dewpoint depressions of
5-12 degF have been noted all morning and have held steady into
this afternoon, preventing any snow from reaching the surface.
----------------------------------------------------------------------
Additional snow and blowing snow potential:
We will soon pump the brakes on snow and sleet across central and
southeast Illinois as a mid-level dry slot begins to work across
the region. This feature can easily be seen in the mid-level water
vapor imagery, and has already taken a bite out of precip further
upstream across the Missouri Ozarks. As this drier air wraps
around the center of surface low pressure and causes the system
to fill/occlude, forcing for ascent will become less robust
tonight across our area. A transition to freezing drizzle is the
most likely scenario tonight as the drier mid- level air robs us
of our ice nuclei, but something to keep watch for is the
potential for dynamic cooling to result in sufficient moisture
through the DGZ to support a continuation of light snow or
flurries. We do see some semblance of this upstream in Missouri
where light snow is still being reported beneath the 500-mb cold-
core low, despite the dry slow working through. Regardless of the
p-type, we are confident in there being a multi-hour lull this
evening and into the overnight period.
During this lull, we have concern for blowing and drifting snow
across areas that received a healthy snowpack. Blustery 20-30 mph
northerly wind gusts will spread across the region shortly after
sunset as surface low pressure passes just to our south. During
the overnight period, it may become extremely difficult for
primary and secondary roads to remain clear.
Behind the departing mid-level dry slot, a deformation axis will
slowly work its way across central and southeast Illinois. From
what we can tell, there does not appear to be any strong mid-level
frontogenesis co-located with negative EPV. The absence of these
features will preclude any threat for CSI and associated heavy
snow. Instead, any one location may experience a couple-hour
window of 0.25-0.50"/hr snowfall rates, perhaps resulting in
additional snowfall accumulations between 1-4" through early
Monday morning. The exception may once again be for locations
along and north of I-74 where low-level dry air may remain a
mitigating factor for snow.
---------------------------------------------------------------------
Behind the departing storm system, winds will gradually tail off
and very cold temperatures will spread across the Midwest and
Great Lakes region. Modified Canadian high pressure will slowly
build across the area resulting in overnight lows in the single
digits by midweek.
By late next week, progressive upper-level flow is threatening to
bring additional wintry weather to portions of the Midwest as a
southern stream wave attempts to phase together with a disturbance
digging into the Northern Plains. As you might imagine, we are
running lean on details in the extended due to our ongoing winter
storm.
MJA
&&
.AVIATION... (For the 00z TAFs through 00z Monday Evening)
Issued at 503 PM CST Sun Jan 5 2025
Moderate snowfall early in the TAF period will keep LIFR
visibilities near our I-72 terminals (KSPI/KDEC/KCMI) through
about 03z. Further north at KPIA/KBMI, little or no snowfall is
resulting in a continuation of VFR conditions, though we have
added a PROB30 group at KBMI for MVFR visibility through 03z to
account for vicinity snowfall.
As snowfall exits and we enter a definitive lull this evening,
visibility will generally improve to VFR. However, with additional
snow moving in overnight, occasional blowing snow (north wind
gusts up to 30 mph), and lowering ceilings beneath the occluding
storm system, have opted to maintain MVFR/IFR conditions through
at least 22z at all terminals, spare KPIA.
MJA
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon CST Monday for ILZ027-029-031-
037-038.
Winter Storm Warning until noon CST Monday for ILZ036-040>057-
061>063-066>068-071>073.
&&
$$
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
943 PM CST Sun Jan 5 2025
.KEY MESSAGES...
- Continued slick travel in spots tonight in snow.
- Lake effect snow is then expected to develop tonight through
Monday into the Chicago metro and could result in hazardous
conditions during the morning and afternoon commutes. A Winter
Weather Advisory has been issued for Lake County, IL.
- Below normal temperatures are expected through the upcoming
week.
&&
.UPDATE...
Issued at 942 PM CST Sun Jan 5 2025
Locally heavy snow associated with a small but fairly intense
f-gen circulation continues across parts of Livingston and
Kankakee Counties this evening. As expected, however, it appears
as if this circulation is starting to gradually weaken, with a
shrinking of the high-reflectivity areas over the last 30
minutes or so, with this band only covering a width of 15 miles
or so. As the f-gen zone weakens, snowfall intensities should
diminish, although light snow will continue off-and-on through
the night.
Did end up ending the Benton county winter weather advisory as
snow amounts and rates just won`t meet criteria here, although
light snow will continue tonight. Left Ford/Iroquois going for
now, although as the f-gen band diminishes, we`ll likely be able
to cancel this early as well.
Across northeast Illinois, light snow continues to spill in off
the lake. The TMKE radar shows generally ragged/disorganized
activity to the north, and the going forecast of up to maybe a
half inch tonight associated with this activity looks good. Main
focus continues to be on a more developed LES band on Monday.
Based on the latest guidance, the inherited forecast appears to
handle these trends well, with a winter weather advisory in
effect for Lake County, IL where the residence time of this band
is expected to be the longest, with intermittent rates near a
half inch to one inch per hour at times. Evening hires guidance
continues to suggest this band will then somewhat swiftly shift
southeast across central Cook county during the afternoon, and
eventually into NW Indiana. 00z HRRR offers up a bit of a
curveball, stalling this band on the Cook/Lake (IN) border
Monday evening as winds off of lower Michigan remain notably
more northeasterly than other guidance. Something we`ll have to
keep an eye on, but little/not predictability with this even at
this time range. Depending on how the rest of the overnight
model suite evolves, we may need to consider an expansion of the
advisory into parts of Cook County with LES intersecting the
afternoon/evening commute.
Carlaw
&&
.DISCUSSION...
Issued at 233 PM CST Sun Jan 5 2025
Through Monday Night:
Early this afternoon, a deep, tightly-wound center of low
pressure is spinning into the Midwest from the Plains.
Extending east of the low center is an expansive swath of precip
stretching across the lower Midwest. This system has brought
strong thunderstorms, heavy snow, freezing rain, and even
thundersnow to parts of the region today. Moderate to heavy snow
continues to trek across central IL, but a notably dry low
level air mass up this way has prevented any appreciable snow
from pushing into our southern CWA. It`s a sharp cutoff, though,
with Lincoln and Champaign having been under moderate snowfall
for a few hours now. As the surface low works into the TN valley
this evening, low level moisture is expected to spread
northward and the snow coverage will follow suit. Still, the
potential for any moderate snowfall out of this system looks
confined to our extreme southern CWA. Light snow looks to spread
as far north as roughly the I-80 corridor tonight with the
system snow expected to move away to the southeast early
tomorrow morning. No changes have been made to the going Winter
Weather Advisory in our south with the best chances for
hazardous travel remaining within and south of the Advisory.
Upwards of 3 to 4 inches could accumulate in our extreme south
with 1 to 2 inches possible up to the Kankakee River Valley.
Concerns are growing around the Chicago metro regarding the
lake-effect snow potential for tonight and tomorrow. The lake-
effect looks to get going late this evening. The RAP and HRRR
have consistently been resolving traces of freezing drizzle
across parts of the metro this evening prior to switching to
snow. The idea is that enough moisture and instability to
support light precip may build over the lake before we can
saturate deep enough for cloud glaciation. It`s possible that
this could result in some localized slick spots, but the
potential appeared too low for a formal mention in the forecast.
Most guidance has come to the consensus that the lake-effect
will be focused toward Lake County, IL through the night and
much of tomorrow morning. The convergence axis should slosh
south along the lakeshore during the afternoon bringing the
focus into Cook County and Chicago. A majority of models,
especially recent high-res camps, suggest that the band may
actually move down the lakeshore at a pretty good rate leaving
Chicago and neighboring communities with only a few hour window
for lake-effect snow. The band will swing over northwest Indiana
during the evening and should exit our CWA to the east prior to
dawn on Tuesday.
Given the much longer residence time expected over Lake County,
IL, we decided to issue a separate Winter Weather Advisory
just for Lake County from midnight tonight through tomorrow
afternoon. The updated forecast calls for 3 to 5 inches across
portions of the county by sundown tomorrow. However, we can`t
rule out the possibility of the band remaining parked over Lake
County even longer, or with higher rates than expected leading
to accumulations closer to the 7 or 8 inch mark. It`s possible
too that this advisory will need to be extended into northern
Cook County, if not beyond, sometime tonight. However,
confidence wasn`t quite there to include anyone but Lake County.
For now, we`re generally expecting 1 to 3 inches around the
lake outside of Lake County.
High res guidance especially has been resolving a push of gusty
winds tonight into tomorrow as well. The strongest winds look to
setup on either side of the convergence axis and lake effect
band with gusts to as high as 30 to 35 mph expected. These winds
may blow some snow around and further impact travel where we
see accumulations. The morning commute tomorrow may prove
slippery for those in Lake County and across our far south.
Concerns for impacts spread over and around the city for the
evening commute as the lake- effect band works across. Winds
will dampen through the evening while cooler air spills into the
region dropping temperatures into the teens by the start of
Tuesday.
Doom
Tuesday through Sunday:
A weak ridge trailing the winter storm brushing our area will
bring dry conditions Tuesday into Tuesday night. The one
exception will be a chance for residual lake effect clouds and
flurries across northeast Porter County amid persistent
northwest flow.
A vigorous but moisture-starved wave developing over western
Ontario Tuesday night will rotate across the western Great
Lakes on Wednesday. Precip at the surface should remain well to
the northeast over Lower Michigan, with a substantial dry layer
under 10kft limiting precip to only virga over the forecast
area.
After another dry day with a passing ridge on Thursday, a deep
mid-level wave will shift across the region Friday and Friday
night as a secondary trough over northwest Mexico ejects ENE.
There is a substantial spread on how much phasing, if any,
occurs with the two waves. Unsurprisingly, forecast guidance
varies considerably, with solutions ranging from snow showers
with only the non-phased northern wave to an expansive fully
phased mid-latitude cyclone brushing our area with accumulating
snow. Blended NBM guidance does look a hair too conservative at
this point with only 10-30% chances for snow across the area,
but felt it would be worth waiting another model cycle or two
before introducing any changes.
Temps will remain below normal through next weekend, though the
coldest arctic air will remain well north of the area in Canada.
Expect daytime highs in the 20s to be common. Low temps will be
locally augmented where snowpack develops over the next couple
days, but overall will be in the single digits above zero to the
teens. Thereafter, ensemble model guidance is hinting at a
return toward average temperatures by the middle of the month,
though much will depend on the location of any snowpack by then.
Kluber/Borchardt
&&
.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 603 PM CST Sun Jan 5 2025
Forecast concerns for the terminals...
- Periods of snow showers and flurries this evening and
overnight for the Chicago area terminals and points south
- Band of lake effect snow to impact the Chicago terminals and
GYY Monday afternoon through Monday evening
- Breezy northeast winds tonight through Monday afternoon with
gusts in excess of 25 kts possible especially near the lake
effect snow
A robust winter storm continues to traverse across central IL
towards central IN this evening, but the dry low-levels have
prevented any snow from materializing across northern IL and
northwest IN. However, light snow showers and flurries are
expected to develop after 02z this evening at the Chicago area
terminals and points south as mid-level moisture interacts with
the increasing low-level moisture off of Lake Michigan. While
these snow showers/flurries may result in some accumulations
(generally under 1 inch), the poor snow quality will make the
main concern reduced visibilities in the 3-5 mile range. The
snow showers/flurries are expected to persist off an on through
the night and into Monday morning before conditions begin to
improve.
Though, a band of lake effect snow is expected to develop near
the IL-WI line late tonight and gradually pivot southward
through the day on Monday. This lake effect is expected to bring
some impacts to the Chicago terminals towards midday and then
gradually move into GYY towards Monday evening. As a result,
sharp changes in visibility can be expected with this band along
with snow accumulations in the 1-3 inch range with locally
higher totals over 4 inches possible closer to the lake. While
confidence is somewhat high on the lake effect band developing,
there continues to be a good deal of uncertainty on the exact
timing the band will reach ORD, MDW, and GYY. Therefore, have
maintained PROB30s for now and will likely need to refine
timings with future TAFs especially at GYY where lake effect
should continue beyond the current forecast period. Once the
lake effect snow concludes, expect conditions to quickly improve
at the Chicago terminals towards the end of the forecast period.
Outside of the snow and lake effect, MVFR ceilings will continue
to spread inland from the lake this evening and persist through
the night areawide. While sites away from the lake and lake
effect snow will see ceilings improve to VFR by Monday
afternoon, MVFR conditions are expected to prevail for those
near the lake. Additionally, winds will also become breezy
tonight as a narrow convergence band sets up ahead of the lake
effect snow which will result in gusts in the 25-30 kt range
especially near Lake Michigan. Winds are expected to gradually
subside through the day on Monday as winds become more
northwesterly.
Note: while a stray flurry may occur near RFD this evening, the
bulk of accumulating snow and associated reduced visibilities
are expected to remain south of the terminal. Though the
aforementioned winds and ceilings can be expected.
Yack
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Winter Weather Advisory until 4 PM CST Monday for ILZ006.
Winter Weather Advisory until 6 AM CST Monday for ILZ033-
ILZ039.
IN...Winter Weather Advisory until 7 AM EST Monday for INZ019.
LM...Small Craft Advisory until 9 AM CST Tuesday for the IL
nearshore waters.
Small Craft Advisory until 3 PM CST Tuesday for the IN
nearshore waters.
&&
$$
Visit us at weather.gov/chicago
Area Forecast Discussion
National Weather Service Miami FL
719 PM EST Sun Jan 5 2025
...New AVIATION...
.SHORT TERM...
(This afternoon through Monday)
Issued at 1158 AM EST Sun Jan 5 2025
As winds veer from northeasterly to an easterly direction today,
airmass modification and warm air advection will be in full swing.
This is due to the surface ridge axis formerly located over the
southeastern United States pivoting eastward into the western
Atlantic waters. Maximum temperatures this afternoon will still be
comfortable in the low to mid 70s (near or just below climatological
norms) but a continued uptick in low-level moisture content across
the region will occur with the potential of greater cloud cover over
the east coast metro area for the remainder of the afternoon. The
easterly to southeasterly component overnight will result in
overnight temperatures several degrees warmer than what was observed
this morning. South Florida will be located in the warm sector of an
approaching frontal boundary as well as on the western periphery of
the departing surface ridge. Lows will range from the low to mid 60s
across all coastal locales to the middle to upper 50s across inland
locations where winds may decouple.
By daybreak, southeasterly flow will shift to a southerly to
southwesterly direction which will user in warm air advection and
bring above average temperatures to the region on the day Monday.
Taking a closer look at forecast model soundings from the CAMs
(convection allowing models), an envelope of deeper moisture does
advect into South Florida on Monday out ahead of the front boundary
sweeping into the region. However these same model soundings also
depict an environment that lacks much instability if any. Both the
HRRR and RAP hint at some potential of a few isolated showers
sweeping across the region out ahead of the front. However given the
lack of instability and the timing of the frontal passage during the
evening to overnight hours, any chance for rainfall accumulations
appears to be quite minimal. HREF Grand Ensemble probabilities of
seeing greater than 0.01 inches of rainfall (lowest amount of
measurable precipitation) on Monday evening remain largely below 40%
across most of the region, with higher odds (50-60%) possible near
Lake Okeechobee and southwestern Florida. With the passage of the
frontal boundary across the region, winds will veer westerly and
then northwesterly ushering in the arrival of another cold and dry
continental airmass.
&&
.LONG TERM...
(Monday night through next Saturday)
Issued at 106 PM EST Sun Jan 5 2025
With the front crossing South FL early Tuesday and strong high
pressure over the center of the country building in, persistent
northerly flow will usher in the coolest air of the season, and
perhaps some of the coldest air the east coast metro has seen in
almost two years. Daytime highs Tuesday through Thursday will be in
the 60s and around 70 over SE FL, while overnight lows will range
from the upper 30s to mid 40s inland and SW FL, to upper 40s and low
50s closer to the Atlantic coast. Best chance Miami and Fort
Lauderdale has to fall below 50 will be Wednesday and Thursday
morning, something neither city has seen since January 2023,
although probabilities continue to decrease with each days model
runs and would not be surprised at all if both sites remain 50 or
above each morning. High pressure shifts to the east for Friday and
Saturday resulting in the flow becoming easterly and therefore temps
will start to moderate closer to normal. This will be short lived
however, as another front crosses late Saturday ushering in another
shot of cooler air and below normal temps to end next weekend. A few
showers may accompany the front next Saturday, with the best chances
along and north of Alligator Alley.
&&
.AVIATION...
(00Z TAFS)
Issued at 716 PM EST Sun Jan 5 2025
VFR prevails through the period. Low ceilings early tomorrow
morning could result in brief periods of MVFR/IFR conditions
across all sites, but certainty remains low at this time so made
no inclusion in the forecast. Light southeasterly winds will start
to veer from the southwest tomorrow, and could become gusty at
times, all ahead of a cold front approaching.
&&
.MARINE...
Issued at 1158 AM EST Sun Jan 5 2025
With a lessening of winds across our area waters today, cautionary
across the Atlantic waters will gradually subside as wave heights
lessen. Conditions will continue to improve into the start of the
work-week before the next front arrives with conditions
deteriorating by mid-week.
&&
.BEACHES...
Issued at 1158 AM EST Sun Jan 5 2025
A high risk of rip currents remains in effect for all east coast
beaches of South Florida through this evening. The elevated risk
current risk will continue through early next week before winds veer
to an offshore direction mid-week.
&&
.PRELIMINARY POINT TEMPS/POPS...
Miami 65 79 56 66 / 0 10 10 0
West Kendall 60 80 54 67 / 0 10 10 0
Opa-Locka 63 80 55 67 / 0 10 10 0
Homestead 64 79 56 67 / 0 10 10 0
Fort Lauderdale 64 79 55 65 / 0 10 10 0
N Ft Lauderdale 64 79 54 65 / 0 10 10 0
Pembroke Pines 64 81 55 67 / 0 10 10 0
West Palm Beach 62 79 51 64 / 0 10 10 0
Boca Raton 64 80 53 65 / 0 10 10 0
Naples 59 76 51 61 / 0 20 10 0
&&
.MFL WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through Monday evening for FLZ168-172.
High Rip Current Risk until 7 AM EST Monday for FLZ173.
AM...None.
GM...None.
&&
$$
SHORT TERM...Hadi
LONG TERM....CMF
AVIATION...ATV
Area Forecast Discussion
National Weather Service Marquette MI
622 PM EST Sun Jan 5 2025
.KEY MESSAGES...
- Expect below normal high temperatures through midweek before
temperatures trend warmer Thursday onwards.
- With the colder conditions, periods of light lake effect snow
will continue, but there are no indications for any major
winter systems to impact Upper Michigan.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 200 PM EST Sun Jan 5
2025
Troughing over the Great Lakes is suppressing the newsworthy winter
storm well to our south, currently over the central Mississippi
valley. Here, we remain under chilly NW flow with 850mb temperatures
around -12C moving over Superior. Though soundings remain dry at
midlevels, this is enough to keep in persistent lake effect over the
NW wind belts - and some flurries and light snow showers are even
extending as far southward as the southern UP with occasional snow
ticking off at KLNL, KIMT, and KISQ. Otherwise, the UP remains under
a blanket of low-level lake clouds, though some breaks in the cloud
cover are apparent on satellite. Temperatures are coming in slightly
warmer than in previous days, reaching into the teens in the western
UP and the lower 20s to the east.
Meanwhile, water vapor imagery and RAP analyses show another weak
midlevel shortwave embedded in our broader troughing. As this drops
through this evening, expect flow to turn more northerly and LES to
migrate to the northerly wind snow belts as a result. Still, with a
sharp inversion at around 4kft in soundings and dry air aloft,
significant snowfall rates are not expected. Apart from where we can
see some terrain enhancement tonight, snowfall amounts even in
excess of a half-inch will be hard to come by. Where we can see that
localized enhancement in the north-central UP (just inland of
Superior across Marquette and Alger counties), a fluffy 1-2in will
be possible by sunrise Monday. Expect otherwise cloudy conditions as
temperatures fall back to lows mainly in the teens, and possibly
single digits in the interior-west.
&&
.LONG TERM /MONDAY THROUGH SUNDAY/...
Issued at 212 PM EST Sun Jan 5 2025
Upper air pattern consists of a 500 mb ridge off the west coast, a
deep and broad trough across most of the U.S. 12z Mon. A shortwave
over the Canadian Prairies drops into the northern plains by 00z Tue
and this moves into the upper Mississippi Valley 00z Wed. A deep
trough gets carved out into the Great Lakes region by 00z Thu. On
and off lake effect snow will continue for this forecast period and
did not make too many changes to the going forecast overall. The
snow will not amount to much.
In the extended, the GFS and ECMWF show a 500 mb ridge in the
western U.S., a trough in the western high plains down into Baja
California and a deep and broad trough in the ern U.S. 12z Thu.
Troughing moves into the plains and upper Great Lakes 12z Fri. This
trough then moves into the Great Lakes region and Mississippi Valley
12z Sat. Broad troughing remains over the area 12z Sun with an
Alberta Clipper type system moving through the area. Temperatures
will be around normal for this forecast period. Will be dry for Wed
night through Thu night. Otherwise, on and off LES continues.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 621 PM EST Sun Jan 5 2025
VFR conditions at KCMX/KIWD will fall back to MVFR overnight as
northerly flow prevails and cloud cover and lake effect snow showers
return, potentially bringing terminal conditions to IFR at times.
Improvement back to VFR is expected Monday afternoon at KIWD while
KCMX is slower to improve. At KSAW, the northerly, upslope flow will
result in continued scattered snow showers to the terminal and
prevailing MVFR for a majority of the period. IFR can`t be ruled out
by morning.
&&
.MARINE...
Issued at 212 PM EST Sun Jan 5 2025
North winds of 20-30 kts are expected through Monday and then stay
15 to 25 knots through Tuesday night from the north. Winds remain
mainly less than 20 kts the remainder of the forecast.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...LC
LONG TERM...07
AVIATION...JTP
MARINE...07
Area Forecast Discussion
National Weather Service Morristown TN
723 PM EST Sun Jan 5 2025
...New UPDATE...
.UPDATE...
Issued at 714 PM EST Sun Jan 5 2025
Temperatures across northeastern TN into southwest VA are stubborn
to rise versus the modeled rate, and that may continue to be the
case overnight for areas with frozen precipitate on the ground.
Lowered temperatures and slowed the overall rise overnight across
locations that are still sub-freezing with observations from area
airports and spotters with the latest HRRR and NAM guidance.
Product wise a SPS for the relevant TN counties and an extension
in time for the winter weather advisory in southwest Virginia have
been issued. A band of light rain is crossing much of the cold
portions of the area now, but will swiftly move through.
Additional light icing is likely from this rain swath.
Meanwhile the main band of rain still lies to our west, and a few
rumbles of thunder or direct lightning bolts cannot be ruled out
as the storms have been rather persistent while crossing Middle
Tennessee. This line of primarily showers should rumble through
during the overnight hours in agreeance with the forecast and
guidance.
&&
.SHORT TERM...
(This evening through Monday)
Issued at 301 PM EST Sun Jan 5 2025
Key Messages:
1. Lull in precip this evening before it fills back in tonight
with the occluded front. Temperatures will continue rising into
Monday.
2. High winds across the mountains and adjacent foothills tonight
will bring gusts up to 60 mph with isolated gusts up to 80 mph
for highest peaks and the most downslope affected areas.
3. NW flow snowfall will develop behind the low`s passage later
Monday when temperatures fall, bringing snowfall to the mountains,
northern plateau & valley, and southwest Virginia.
Discussion:
A pretty messy one earlier across the area with freezing rain,
sleet, and snow. We are currently in a lull period with
precipitation, though some places may still be experiencing some
light precip. Take extra care out there as some temperatures below
freezing with anything on the ground will be frozen and slippery.
Many of the Winter Weather Advisories were cancelled a few hours
ahead of time. It still remains in effect for southwest Virginia
for any lingering precipitation.
It may seem backwards, but we will continue to warm with southerly
flow increasing tonight. Our warmest temperatures or highs for
Monday will be around or just before sunrise before the tumble.
As a result, a LLJ will form a mountain wave set-up over the
Southern Appalachians. Southerly winds with gusts in warning
criteria can be expected for the stereotypical impacted areas;
highest peaks, adjacent foothills, and downslope attracted areas.
Expect this increase to occur in the next couple of hours closest
to sunset, and for peak winds to occur between the 12-3 AM EST
time frame or so. Winds are expected to come down headed into
daybreak Monday. A High Wind Warning and also a Wind Advisory are
in effect beginning tonight and will go through the morning.
Fortunately with warming temperatures, the returning precipitation
will primarily be in the form of rainfall. Heaviest of the system
will arrive before midnight persisting overnight. Generally,
everywhere will see at least half an inch of QPF. Upslope spots of
the southern plateau, the Smokys & southward, and SW VA mountains
may amount to over an inch of rain. The main line will exit to the
east after 7 AM EST, however, wraparound will develop and bring NW
induced snow to the slopes. Some might reach the lower elevations
of the upper valley. Temperatures are expected to fall with time
Monday behind the front, so the NW wraparound will primarily be
snow. Do not believe sleet or freezing rain will be an issue with
the last push because of dropping temperatures from the SFC to
aloft and we will have been in a period of warmth where elevated
surfaces and roads should be above freezing.
Will see if anything will need issued when we get closer, but, NW
winds may increase over the mountains behind the departing low and
high pressure building in over the Plains. NW winds aren`t
typically "blowers" per say, but the pressure gradient does
increase across the Appalachians.
&&
.LONG TERM...
(Monday night through next Sunday)
Issued at 301 PM EST Sun Jan 5 2025
Key Messages:
1. Continued cold.
2. Wintry precip moving out of the area Monday night.
3. Uneventful through mid-week.
4. Another possibility for wintry precip next Friday afternoon
through Saturday morning.
Discussion:
Cold air will remain entrenched across the area this week, generally
running 5 to 10 degrees below normal. Zonal flow will keep the
midweek period fairly quiet.
However, the next southern Rockies system will begin ejecting into
the central and southern Plains states Thursday-Friday, drawing up a
large slug of Gulf moisture into the southeastern U.S. and Tennessee
Valley on Friday, persisting Friday night and departing Saturday.
This event continues to show model potential for being another
wintry weather system. The latest 12Z GFS run is bringing with it 6
to 8 inches of snow to our Valley, although the previous 06Z run
kept those impacts away from us and in the Ohio Valley. The previous
00Z GFS run before that covered our Valley with 4 to 6 inches. The
ECMWF has been less aggressive with the 00Z and 06Z runs, and am
still awaiting the 12Z run. So, besides the inconsistent (but not
unexpected) flip-flops in the GFS runs, there remains disagreement
between the GFS and ECMWF overall.
This situation will continue to bear monitoring, as surface
temperature forecasts beneath a good southwesterly flow aloft (which
this will have) tend to warm - and impacts wane - as such events
&&
.AVIATION...
(00Z TAFS)
Issued at 633 PM EST Sun Jan 5 2025
Freezing rain still possible in northeastern TN and north until
wetbulb temperatures can rise above freezing mark tonight.
Temperatures will continue to rise overnight before falling
tomorrow. CIGs are expected to slowly drop through the period,
with widespread MVFR conditions expected. KTRI may resist MVFR as
a strong wind event sweeps through between 03z and 12z with wind
shear in the forecast. During this period a band of rain is
expected to also cross the region from west to east. As the
system moves out, wraparound snow late in the period post 18z is
possible, especially KTRI and surrounding area. Winds will
gradually pivot through the period, and may be gusty at times
upwards to 25 knots.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 38 43 25 40 / 100 10 0 0
Knoxville McGhee Tyson Airport, TN 34 46 23 35 / 90 30 10 0
Oak Ridge, TN 34 44 22 35 / 100 20 10 0
Tri Cities Airport, TN 32 43 20 31 / 100 70 30 0
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Wind Advisory until 7 AM EST Monday for Johnson-Southeast Carter.
High Wind Warning until 7 AM EST Monday for Blount Smoky
Mountains-Cocke Smoky Mountains-Sevier Smoky Mountains-
Southeast Greene-Southeast Monroe-Unicoi.
VA...Winter Weather Advisory until 10 PM EST this evening for Lee-
Russell-Scott VA-Washington VA-Wise.
&&
$$
SHORT TERM...Wellington
LONG TERM....GC
AVIATION...Wellington
Area Forecast Discussion
National Weather Service Pocatello ID
143 PM MST Sun Jan 5 2025
.SHORT TERM...Today through Monday Night.
The first of two shortwaves is moving through today and has brought
light snow to much of the area with more snow showers expected
through the evening, especially in parts of the Eastern Highlands
and South Hills. The valleys will still see some light snow through
the afternoon, which will mean about a half inch to an inch of
snowfall and closer to 1 to 3 inches in the mid elevations. Behind
this moisture, more patchy, dense fog is expected to form tonight
throughout parts of the upper Snake Plain, eastern Magic Valley, and
across the Arco Desert with the potential for visibility to drop
below a mile at times. We will likely see more of it Monday night
into Tuesday morning, too.
A Winter Weather Advisory remains in effect for the Bear River Range
where an additional 6 to 10 inches of snow are likely by midday
Monday, so went ahead and extended the advisory for 6 more hours.
About 3 to 5 inches of snow will fall in the rest of the mountains
in the South Hills and Southeastern Highlands throughout the day on
Monday, but the bulk of it will be done falling by midday. In the
valleys, the main push of moisture with Monday`s shortwave will be
during the morning hours with the rain/snow line likely falling
somewhere between American Falls and the Coldwater rest area based
on HRRR and NAM 12Z model data. This means a 40 to 50 percent chance
of at least an inch of snow in the eastern Magic Valley (though it`s
very dependent on marginal temperatures producing rain vs snow) and
about a 30 to 50 percent chance of 2 inches of snow around
Pocatello. Of note, the 18Z data shifts this band of moisture
farther south and wants to keep more of is out of the Snake River
Plain. We will have to see how this trend through the rest of today
and tonight. Any lingering snow tapers off Monday night and we dry
out for Tuesday. AMM
.LONG TERM...Tuesday through Sunday.
Upper ridge with northerly flow over Idaho builds in for most of
the work week. Model temperatures, including ensemble
deterministic and blended bias corrected all keep trending
slightly colder especially for mid week. Would not be surprised to
see forecast highs dip colder. A weak shortwave slides by just to
the east Wednesday, and may be enough for a few weak showers
mainly along the WY border. Rest of the forecast area looks to
remain dry. A stronger feature collapses the ridge Friday into
Saturday, leading into another weekend of active weather and
potential precipitation. DMH
&&
.AVIATION...18Z Sunday to 18Z Monday.
Shortwave swings through Idaho overnight tonight and
through Monday. Light SHSN consolidate late today and overnight
mainly over the southern and eastern highlands, though some snow
will still be possible in the interstate corridor. This would mean
that KSUN would be the LEAST impacted terminal through the forecast
period, with respect to SN. Stratus/fog remain a significant
concern, so expect conditions to vary between MVFR/IFR. SN ends
north to south through the day Monday, but stratus/fog could remain
a concern through that time period. DMH
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 11 AM MST Monday for IDZ060.
&&
$$
Area Forecast Discussion
National Weather Service Raleigh NC
827 PM EST Sun Jan 5 2025
.SYNOPSIS...
A developing storm system will bring a mix of precipitation types to
central North Carolina through Monday evening. Below normal
temperatures will then move back into the region for the rest of the
week.
&&
.NEAR TERM /TONIGHT/...
As of 827 PM Sunday...
Mid evening radar imagery suggests most of the precip from earlier
today has exited the area. There were a number of mPing and social
media reports of snow and sleet mainly along and north of US-64,
with around 0.2-0.5 inches of snow in the Triad and a few reports of
around an inch on elevated surfaces. Lesser amount were seen around
the Triangle where precip was mainly an hour or two of a snow/sleet
mix. More importantly, the precip earlier today managed to lower
temperatures along I-85 into the upper 20s to lower 30s which is
where they remain as of 01Z. Elsewhere to the south temps range from
the upper 30s to mid 40s. Dewpoints area-wide have started to
recover from the single digits earlier today and are now in the low
to mid 20s.
Forecast concerns tonight are along I-85 where precip fell earlier
today and knocked temps below freezing. Wet bulbs in these areas
remain in the mid to upper 20s and there is an area of rain across
upstate SC that should be arriving just before midnight. It will be
a close call to see if wet bulbs can rise above 32 ahead of that
precip shield. HRRR and NAM would suggest a minimal threat for icing
whereas the RAP has been holding onto cold air for longer and has
been verifying better so far this evening. Given the antecedent cold
air, precip occurring at night, and stubbornly low dewpoints, I went
ahead and expanded the Winter Wx Adv to include Durham Co westward
along I-85 through the Triad into Davidson/Randolph Co`s. The most
likely scenario would be a very light glaze of ice in these areas,
although it`s conceivable a few hundredths of an inch could be
measured before temps rise above freezing. The RAP would suggest
temps will be above freezing by 4-5 AM but wanted to tack on an
extra few hours at the end given overall uncertainty with how things
will evolve in those area. If temps clearly warm up ahead of
schedule, the Adv will be cancelled early. Ultimately, this is not
an ideal setup for widespread significant/impactful freezing
rain given the lack of a strong surface high to our north, and the
overall duration of this event should be relatively limited for that
reason.
The remainder of the forecast remains on track with precip
overspreading the area late tonight, falling primarily as rain
outside of the rain/freezing rain concerns mentioned within the
Advisory area. The original Winter Wx Advisory remains unchanged
from Person Co eastward to Halifax.
&&
.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 315 PM Sunday...
Although the primary low will be over eastern Kentucky as of Monday
morning, Miller B cyclogenesis will result in the surface low
redeveloping off the Norfolk coast Monday afternoon and continuing
to move offshore through the rest of the period. The heaviest
rainfall along the cold front should be moving through the region in
the morning, with freezing rain continuing near the VA/NC border
through mid-morning. Overall, models are now trending slightly
faster with the departure of precipitation, and the Triad could
spend much of the afternoon dry. Have somewhat sped up the departure
of precipitation, but did not want to jump onto that trend too
quickly. Nearly all precipitation still appears likely to be out of
the region by the evening, but cannot rule out some wraparound
precipitation on the western side of the new Atlantic low, which
would occur from Raleigh to the northeast. With cold air beginning
to funnel in, this could be a rain/snow mix. At the same time, there
is usually a model trend for the cold air to chase the
precipitation, so this precipitation may remain all rain. Any snow
that occurs should be short-lived and result in minimal
accumulation. Expect a wide range in temperatures during the day,
with highs ranging from near 40 at the VA/NC border to the lower 60s
across the south. As the wind picks up out of the northwest behind
the departing low Monday night, lows will fall into the 20s
everywhere.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY...
As of 340 PM Sunday...
...DRY WITH COLD/WELL-BELOW NORMAL TEMPERATURES THROUGH THE
REMAINDER OF THE WORK WEEK...
...POTENTIAL FOR WINTRY P-TYPE CONCERNS FRIDAY EVENING/SATURDAY
Underneath upper troughing and with an expansive area of Arctic high
pressure in place over over the central and eastern CONUS, cold,
well-below normal temperatures will be a main stay through the
remainder of the work week. Highs each day will generally range from
mid/upper 30s north to lower/mid 40s south, with Thursday
potentially being the coldest 24 hour period via renewed sfc
pressure rises and resultant CAA. Lows each night in the mid/upper
teens to lower 20s.
The next chance for precipitation will arrive late Friday and
Saturday with the northeastward ejection of a surface low through
the GOM, Deep South, and SE US. With the antecedent arctic air in
place, there is the potential for wintry precip across the region as
moisture overspreads the area from the SW Friday night and into
Saturday. The parent shortwave trough forecast to drive this
developing storm system is currently in a data sparse region off the
Pacific NW Coast. So unsurprisingly, model spread is currently high,
but should hopefully start to decrease once the trough moves
onto the NW coast onshore tonight and Monday.
NWP model guidance is starting to trend towards a complex,
Miller-B pattern across the region with insitu-CAD in place over the
NC Piedmont. This pattern typically results in well-defined
corridors of mixed precip types, which are closely aligned to the
eventual track and location of the southern stream low pressure
center. Even a slight northward or southward shift in track will
result in significant changes in precip types and amounts. At this
time, all wintry p-types remain a possibility across central NC.
For forecast simplicity, will stay with a snow-rain forecast, with
the snow largely confined to climatological favored areas across the
Piedmont, western Sandhills, and northern/central coastal plain.
Residents should closely monitor the latest forecasts for potential
winter impacts.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
As of 655 PM Sunday...
VFR conditions are expected to start the TAF period. The main
challenge for the 24-hour TAF period will timing the onset of
precipitation (with potential FZRA at GSO/INT) and associated sub-
VFR conditions, along with LLWS and perhaps gusty winds at FAY.
The next batch of precipitation is set to move across the terminals
between 03 and 09z. While this will predominately be in the form of
RA, wet bulb temperatures across GSO/INT suggest a period of -FZRA
may be possible between 03 and 07z. Given at least a 40-percent
chance of this in the guidance, introduced a TEMPO period for this,
including associated sub-VFR potential. There is also a non-zero
chance some brief low CIG/VIS could occur at GSO/INT prior to this
precipitation onset given high RH, but confidence was too low to
mention. Otherwise, this first batch of precipitation should move
through with mostly VFR conditions. The main band of precipitation
will come with the actual frontal system and low pressure, roughly
between 09-12z in the west and 13-16z at RDU/FAY/RWI, moving out
between 17 and 21z from west to east. IFR/LIFR conditions are likely
with this batch of rain. A strong LLJ between 40 and perhaps 55 kt
will overspread the terminals and this remains in the TAFs, ending
earliest at GSO/INT. Guidance suggests some mixing will occur at FAY
Mon morning and afternoon so introduced a period of gustiness
between 20 and 30 kt. Conditions are expected to slowly improve
after the rain moves out, but likely hover in the IFR/MVFR range
prior to the end of the TAF period.
Outlook: VFR conditions should return a cold front Mon evening, with
strong and gusty nwly surface winds. There is a chance of some light
snow Mon evening as the system pulls out, most favored at RDU/RWI.
VFR conditions are expected through Fri when the next weather system
should begin to impact central NC.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from midnight tonight to noon EST
Monday for NCZ007>011.
Winter Weather Advisory until 7 AM EST Monday for NCZ021>025-
038-039.
&&
$$
SYNOPSIS...Green
NEAR TERM...Leins
SHORT TERM...Green
LONG TERM...CBL
AVIATION...Kren