Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/21/22
Area Forecast Discussion
National Weather Service Gaylord MI
959 PM EST Sun Feb 20 2022
.UPDATE...
Issued at 949 PM EST Sun Feb 20 2022
Cold front pushing through southeast parts of the area, with
cooler air filtering into the area in its wake. A fairly quiet
night in store for northern Michigan with clouds on the increase
as a precursor to the mixed precipitation mess headed our way
later tomorrow into Tuesday. Lows will settle into the teens to
lower 20s. A few flurries or light snow showers possible over
parts of eastern upper, otherwise conditions should be dry.
Made a few tweaks to precipitation timing on Monday, pushing the
onset of precipitation a bit later in the afternoon or early
evening for most areas. 00z models have remained generally in
line with previous thinking on mixed precipitation event. Largely
a snow event over eastern upper, mainly a sleet and freezing rain
event from just south of the bridge to M-32, with mainly a
freezing rain event south of M-32. All of this is subject to
change with just a small adjustment in storm track. Whichever way
you slice it, an icy mess for much of northern lower setting up
Monday night through Tuesday night.
UPDATE Issued at 803 PM EST Sun Feb 20 2022
An early update this evening to expand the watch further north all
the way to the bridge. Some troubling ice signals in the latest
models including the 21z RAP showing >.50" of ice accumulation
over much of northern lower while the 18z HRRR shows 0.25" to
0.50" of ice accumulation over the same area. Certainly have some
concerns that parts of the area end up with an extended sleet
event but even that would likely yield a fairly large impact to
travel.
Otherwise, front is slicing through northern lower this evening.
Will have to watch for the potential for a bit of patchy freezing
drizzle behind the front over the next few hours, especially
across the higher terrain of northern lower. Will also likely see some
slippery side roads as slushy areas freeze up with dropping
temperatures.
&&
.NEAR TERM...(Through Tonight)
Issued at 323 PM EST Sun Feb 20 2022
...Gusty winds diminish; Patchy freezing drizzle?...
High Impact Weather Potential: Minimal despite diminishing winds and
at least some potential for patchy freezing drizzle.
Pattern Synopsis/Forecast: Early this afternoon, broad upper-level
troughing is evident across much of central Canada with flow
becoming flatter/more zonal across the northern tier of the CONUS.
Low pressure is currently centered just south of James Bay and is
expected to quickly race east into Quebec this evening. This will
ultimately drag a cold front across northern Michigan late this
afternoon and evening before slowly losing its southward push with
time and settling across southern lower Michigan by Monday morning.
Primary Forecast Concerns: Diminishing winds and potential for
patchy freezing drizzle behind the aforementioned cold front.
Very gusty southwest winds early this afternoon will slowly diminish
through the remaining daylight hours and especially this evening as
that cold front alluded to above treks north to south across the
forecast area through this time frame. This will result in veering
winds to a more northwesterly direction by late evening...veering
farther north-northeasterly by early Monday morning. As a result,
above normal afternoon temps will fall back to reality tonight, but
with a north-south gradient in low temps with single digits expected
across eastern upper, teens across the majority of northern lower,
while areas south of M-72 feature lows in the low-mid 20s.
Other issue to watch heading into tonight is pre-frontal snow
currently ongoing across eastern upper exiting over the next couple
of hours. However, this may transition to a bit of patchy freezing
drizzle immediately behind the cold front where latest trends
continue to signal for rather brief shallow saturation at
temperatures that are likely a touch too warm to support ice
nucleation. So while any patchy freezing drizzle isn`t expected to
be widespread or amount to much in the way of appreciable icing,
it`s conceivable that we may wring out a bit here and
there...initially across eastern upper late this afternoon (perhaps
mixed with some snow given slightly deeper moisture) then across
northern lower later this evening into early overnight.
&&
.SHORT TERM...(Monday through Wednesday)
Issued at 323 PM EST Sun Feb 20 2022
High Impact Weather Potential: Accumulating snow/sleet/freezing rain
Monday into Wednesday...
Pattern Synopsis/Forecast:
Last 24-48 hours has seen the trough axis aloft shift eastward out
of the area...with ridging building through the Great Lakes ahead of
another bit of shortwave energy diving southeastward into the Upper
Midwest this morning, evidenced by some semblance of a baroclinic
leaf to our north on satellite imagery...as closed low initially
over Nunavut in northern Canada pivots southeastward into central
Hudson Bay. Upstream flow is again amplifying...with energy south of
the Aleutians helping to build ridging across the western Gulf of
Alaska...as shortwave that had previously beat down the ridge
continues to trek eastward through the flow, with additional arctic-
based energy swinging down behind it from the north/northwest.
Meanwhile...in the southern stream of the flow...a closed low still
hang out off the coast of southern California, noted by a nice
swirl in water vapor imagery...though it is weakening in its
intensity to some degree as the aforementioned additional energy
dives into the northern stream of the flow. Some weak energy
extends across the southern US, under the subtropical jet aloft
down there...and ahead of a weak shortwave over Kansas.
The above results in baroclinic zone stretching from east central
Ontario, more or less back along the international border into
Montana...with a northwestward turn through Alberta and into British
Columbia...reflected by a surface cold front extending from a couple
low pressure centers to our north (just north of Lake Superior) and
northwest (near International Falls), following that BCZ right on
into British Columbia. Surface warm front extends more or less from
the International Falls low southward into central Iowa...along cusp
of warmest air aloft...and an area of marginally higher dewpoints in
the 20-25F range (as opposed to 0-10F ahead of the front). Tight
pressure gradient between the surface low to our northwest...and
surface high across the Mid-Atlantic...results in stronger winds
across Michigan this morning, as well as temperatures already
approaching the freezing mark in some locations as of 15z.
Going forward...will look for baroclinic zone to get hung up across
the region somewhere...as southern stream energy continues to deepen
across the southwestern US. Niblet of energy trekking through the
flow later Monday night into Tuesday will be slightly negatively
tilted as it heads northeastward along the BCZ through Tuesday
night...resulting in a strong surface cyclone trekking northeastward
through the flow for the first half of the week. Monday
night...looks as though we should be between departing polar jet to
our north...and approaching subtropical jet to our south...and as
the southern stream jet max lifts through the region, strengthening
as it does so...another period of jet coupling may be possible later
Tuesday into Tuesday night. Jet max aloft moves more or less
overhead beyond midweek...as we sit a little deeper into the cold
side of the BCZ later Wednesday into Wednesday night, following the
passage of the aforementioned surface cyclone and strong northerly
flow with very strong (1040+mb) cold, dry surface high pressure
settling into the Central Plains.
Primary Forecast Concerns: Breezy conditions at
times...precipitation types, amounts, timing, and locations through
the period...
Cold northeasterly surface flow north of the front should ramp up a
bit going into Monday night as the pressure gradient tightens
between the developing surface low to our southwest...and surface
high to our north. Would not be surprised to see some surface winds
in the 10-20kt range Monday night into Tuesday, particularly north
of the warm front, which currently looks to stretch across central
or southern Lower...so would look for breeziest conditions generally
closer to the Tip of the Mitt and Eastern Upper, where the potential
for snow is greatest...so there could be some blowing snow concerns
to contend with. Strongest winds aloft currently appear to be in the
warm sector of the system, and it should be somewhat difficult to
get those winds (~30-40kts at 850mb) to mix down, given the strong
inversion aloft with the warm nose...but some of the lower level
winds toward 925mb (closer to ~30kts or so) may be low enough to
have a better shot at mixing down.
Mid-level moisture will begin to advect into the area from the west
along and north of the BCZ aloft early in the day Monday,
particularly across eastern Upper and Tip of the Mitt...perhaps as
far south as M-32 or M-72...as warm, moist, gulf-based flow rises
over the frontal surface. Plan views and soundings support the idea
of a low-stratus deck over northern Lower Monday into Monday
afternoon, and as some of that moisture moves in aloft, would look
for seeder-feeder processes to commence, leading to some snow
starting perhaps as early as late Monday morning into early Monday
afternoon for some areas...though it may be a little more transient
initially. Can`t entirely rule out freezing drizzle potential early
in the day, though suspect there may be a layer of the cloud cold
enough to support ice nucleation. Something to watch. Better, deeper
moisture will spread northward with time later Monday night into
Tuesday...with pwat values in excess of 0.5" on the high end of
climo for this time of year for our area (pwat values should be even
higher across southern Lower, on the south side of the front).
Attm...push of moisture across northern parts of the CWA Monday into
Monday night will be associated with better forcing aloft that way
early in the day...associated with the right entrance region of the
upper level jet to our north. Areas of low-level convergence will
generally be associated with the warm front across parts of
central/southern Lower...and also eastish flow convergence along
northern Lake Huron and parts of eastern Upper...though overlake
instability will likely be waning as temps aloft, even at 925mb,
approach levels nearly too warm to support sufficient delta Ts
overtop lake surface temps in the 1-3C range. Will leave some slight
chances for the Lake Huron coast early Monday till things warm up.
Will have concerns for frontogenetical processes to enhance
snowfall/precip Monday night especially, as the warm side of some
fgen signals in model guidance appears collocated with some of the
better moisture and upper level divergence across eastern Upper and
the northern half of northern Lower Monday into Monday night. Above
the inversion...lapse rates aloft should be rather steep, which
makes sense as we`d be warming and moistening a layer in the mid-
levels beneath colder air further aloft. There are signals for
perhaps some low-level cape across parts of the warm sector late
Monday night into early Tuesday, as 850mb dewpoints approach +10C,
which could be of concern as it could further locally enhance
precip...and perhaps also rob us of moisture (which may be a concern
otherwise, given convective potential across the Tennessee Valley
during this time).
Going into Tuesday...better forcing will lift in from the south as
southern stream jet max approaches and some jet coupling comes into
play...just as the deeper moisture advects in from the south. Will
look for good precipitation rates to occur through Tuesday
afternoon...petering off going into Tuesday night as the system
departs. Warmest air aloft looks to move in during the day
Tuesday...and will therefore look for greatest potential for
freezing rain and sleet Tuesday...though the transition should start
across the southern portions of our CWA Monday night as that warmer
air advects in aloft. As mid-level drying occurs with the dry slot
later Tuesday...will look for bulk of the precipitation to
ultimately focus itself up across eastern Upper again later Tuesday
into Tuesday night, under wrap-around moisture behind the system.
Lake convective potential returns by Tuesday night into Wednesday as
temps aloft fall again...and winds become more north/northwesterly
with time. As mentioned in last night`s AFD...a period of freezing
drizzle is not out of the question across the southern CWA Tuesday
night (to add insult to injury) as the column potentially remains
warm enough to minimize potential for in-cloud ice nuclei activation
as we lose moisture aloft.
A major concern with Monday night into Tuesday will be surface
temperatures, given the warm nose aloft. Attm...suspect much of the
area will remain below freezing, given the cold northeasterly
surface flow in place, with areas closer to central Lower and
Saginaw Bay potentially getting closer to freezing if the warm front
lifts far enough north. Attm...latest guidance seems to be trending
the warm air a bit northward compared to yesterday at this time...so
am somewhat concerned that the ice/mixy potential may spread further
north than previously expected. The battleground for the mixy precip
will remain across northern Lower...generally along and south of M-
32/M-68, though we`ll see how things fare in future model runs as
guidance still tries to nail down the exact track of the surface low
and northward extent of warmth aloft/depth of cold air near the
surface. Signals continue, however, to point toward freezing rain
across areas south of M-72, where ice accumulations in excess of
0.25" over the course of the event aren`t out of the question.
.LONG TERM...(Wednesday night through Sunday)
Issued at 323 PM EST Sun Feb 20 2022
High Impact Weather Potential: Minimal attm...additional periods of
active weather possible late next week, though...
Pattern Synopsis/Forecast:
As southern stream energy begins to dig eastward Thursday...will
look for another round of cyclogenesis to our southwest. Noting that
the baroclinic zone will be a bit further south this time...will
expect this system will also be further south than the early-week
system...suggesting that we should remain cold enough for all snow
this time (yay!)...assuming the storm remains close enough to bring
us some impacts...so will have to monitor this in the coming days.
Meanwhile...with that strong surface high nearby and slowly drifting
in with time...it could get quite chilly at times, particularly
early in the extended, when the coldest air aloft (-20C or colder)
is overhead. Signals currently point toward another clipper dropping
into the region for next weekend, as the upper level pattern appears
to shift eastward again, with ridging returning to the western US
and troughing potentially returning to the eastern US. Will keep an
eye on it in the coming days...as this would suggest active and
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 618 PM EST Sun Feb 20 2022
A cold front will slide through the area this evening with winds
shifting to the north and eventually northeast. There is a low
confidence chance of patchy freezing drizzle immediately behind
this front. Clouds will gradually lower throughout the day on
Monday to MVFR with light precipitation possibly developing by
later in the day as low pressure begins to push toward the Great
Lakes out of the central Plains.
&&
.MARINE...
Issued at 323 PM EST Sun Feb 20 2022
Gusty southwest winds remain in place this afternoon, but will be
gradually diminishing through the remainder of the daylight hours,
and especially this evening with conditions expected to fall below
small craft advisory criteria across the majority of northern
Michigan`s nearshore waters. Winds will turn northerly tonight and
eventually northeasterly during the day Monday...likely increasing
again to advisory criteria Monday afternoon into at least Monday
night.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER STORM WATCH from Monday evening through Tuesday evening
for MIZ016>018-020>036-041-042-097>099.
LH...NONE.
LM...NONE.
LS...NONE.
&&
$$
UPDATE...JK
NEAR TERM...MJG
SHORT TERM...FEF
LONG TERM...FEF
AVIATION...JK
MARINE...MJG
Area Forecast Discussion
National Weather Service Denver/Boulder CO
840 PM MST Sun Feb 20 2022
.UPDATE...
Issued at 820 PM MST Sun Feb 20 2022
Only minor adjustments to tonight`s forecast. First cold front
still expected to push into the Denver area around 21z, with light
snow developing Monday night. HRRR model suggests enough snow in
zone 33 to possibly warrant a Winter Weather Advisory, but will
let the mid shift have the final decision on that issue.
&&
.SHORT TERM...(This evening through Monday)
Issued at 230 PM MST Sun Feb 20 2022
Hope everyone enjoyed today because we`ll be back to winter by
later Monday with a return to colder temperatures and light snow.
A broad upper trof is developing over the Pacific Northwest and
Northern Rockies today which will very slowly approach Colorado
during the day on Monday. For tonight the flow aloft will shift
more southwest with a bit of a lull on speeds over the mountains
this evening. Expect an increase in flow and mid/high level
moisture later tonight with 40kt cross barrier flow by Monday
morning over the higher mountains. Airmass is still dry during the
morning hours so no chances of showers yet except snow showers
developing over zone 31 by late morning and then increasing in the
afternoon. Will be issuing a winter weather advisory for zone 31
for snow increasing Monday afternoon and through early Tuesday
morning with preferred southwest orographic flow there. Given the
strong southwest flow don`t see much snow in the Summit county
mountains at least through Monday afternoon.
As for the lower elevations, the associated strong cold front will
move across the plains during the mid and late afternoon hours.
There is some timing differences with the GFS/NAM showing an
earlier arrival at Denver around 20-21z while HRRR/RAP is slower
around 23-00z. For now will split the difference with lowering
clouds and scattered snow showers developing late in the day
especially in the foothills and west of Interstate 25. The brunt
of the snowfall will hold off until Monday evening. High
temperatures will be tricking depending on frontal passage. For
now will go with higher temperatures than guidance with the later
front arrival from Denver southward.
.LONG TERM...(Monday night through Sunday)
Issued at 250 PM MST Sun Feb 20 2022
A deep upper level trough will dominate the weather pattern for the
upcoming week resulting in an extended period of well below normal
temperatures as well as snowfall in the mountains into the Urban
Corridor. There is lower confidence with respect to the snow
duration and amounts for the foothills, urban corridor, and plains.
Slick travel conditions are possible, especially over the higher
terrain Monday evening into Tuesday.
Mountains...
Monday evening, the large upper level trough slowly approaches
the region and the first piece of shortwave energy ejects across
the state. QG fields indicate a good period of synoptic ascent
overnight. Moist southwesterly flow aloft will support of light to
moderate snowfall to continue in the mountains overnight. There
is a period between the exit of the first shortwave and the next
shortwave on Tuesday where there could be a lull or decrease in
precip coverage. QG fields show an area of downward motion over
the region which may limit snow. Ahead of the next "wave", snow
increases Tuesday night in the mountains. Light snow continues
Wednesday into early Thursday. Conditions dry out after, as the
region becomes under the influence of synoptic scale subsidence.
Total snow accumulations by Thursday still look to be in the 10-20
inch range in the higher mountains. Despite the higher amounts,
this is a long duration snowfall which has limited the need for
any headlines for most areas of the mountains. Only exception will
be zone 31 (near Rabbit Ears Pass) which will be under a Winter
Weather Advisory Monday evening into early Tuesday with potential
for 5-7 inches of snow.
Front Range, Urban Corridor, east plains...
There is more uncertainty in regards to the snowfall in the
foothills, urban corridor, and plains for this system. By Monday
night, a cold front will have pushed through the plains inducing
NE/ENE flow. Models cross sections show low level moisture
increasing with a deepening layer of upslope flow. There is still
a considerable amount of spread in solutions in the timing of
snowfall onset over the urban corridor and plains, but most hi-res
guidance has light snow developing before midnight. QPF is also
variance among deterministic and ensemble solutions with the ECM
and GEM continuing to be drier compared to GFS. After the first
shortwave exits Tuesday, snow chances decrease over the plains.
Model soundings still indicate shallow upslope flow in place
despite less favorable fields for upward motions which could keep
light snow around with better chances closer to the foothills
Tuesday. By late Tuesday evening chances increase ahead of the
next shortwave with potential for light snow into late Wednesday.
Next concern for impacts this week will be the arctic airmass that
accompanies this system. Given the slow moving nature of the system,
anomalous cold air will be in place Tuesday through Thursday.
Daytime highs will remain in the single digits to teens over most
areas. Low temperatures be will be near zero in the urban corridor
with values below zero in the NE corner of CO. Temperatures
gradually moderate Thursday/Friday and into the weekend. Into the
weekend, confidence in the upper level pattern decreases as there is
quite a spread in model solutions. Overall, signal for precipitation
looks zero to minimal.
&&
.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 820 PM MST Sun Feb 20 2022
South/southwest winds should continue at the terminals the rest
of the night into Monday morning. The next big change for Monday
afternoon with strong cold front expected in the 21-00z time frame
with only low confidence on exact timing and airmass saturation
after frontal passage. Expect ILS/MVFR cigs to develop after 22z
with snow developing by 00z, continuing into Monday evening.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from noon Monday to 6 AM MST Tuesday for
COZ031.
&&
$$
UPDATE...Cooper
SHORT TERM...Entrekin
LONG TERM...Mensch
AVIATION...Cooper/Entrekin
Area Forecast Discussion
National Weather Service Cheyenne WY
839 PM MST Sun Feb 20 2022
.UPDATE...We are tracking the arctic front this evening. An
observation site in Chadron has switched to a north wind around 720
PM MST. Comparing this arrival time to some HI-RES models
(HRRR/NAM/ARW) the arctic front running ahead of schedule compared
to all HI-RES outputs. The HRRR is doing the best being only 30-40
minutes behind. The temperature has dropped in Chadron but the bulk
of the cA (continental Arctic) airmass is lagging and is still
moving across southwestern South Dakota. This airmass will continue
push toward the NE Panhandle and overtime it will catch up to the
main frontal boundary by the early morning hours. We will continue
to track this front as it pushes across the NE Panhandle and some
slight tweaks in the hourly temperatures may be needed.
.SHORT TERM...(This evening through Tuesday)
Issued at 330 PM MST Sun Feb 20 2022
Very pleasant weather this afternoon, even with breezy to locally
windy conditions at times and some high clouds moving across the
region. Temperatures have climbed into the middle 50s to low 60s
across most of the eastern plains along and east of the Interstate
25 corridor. Temperatures should max out in the upper 50s to
middle 60s before the sun begins to set. Still need to monitor
the northern Snowy Range foothills, including Arlington and Elk
Mountain, for strong gusty winds. After a bit of a lull late this
morning, winds have increased once again closer to Elk Mountain
with gusts of 55 to 57 mph detected. Will handle this with a SPS
for now, but if gusts start climbing towards 65 mph...will likely
need a short fused High Wind Warning ahead of the arctic front.
Otherwise, you have one more relatively mild evening to enjoy
before the arctic blast plunges south tonight. Leading edge of the
arctic front is just starting to push into far northern Wyoming
near the Montana border, with winds shifting into the northeast
and afternoon temperatures beginning to fall into the 30s at this
time. If you go a few hundred miles northeast, temperatures have
lowered into the single digits and teens in North Dakota at this
hour.
Tricky forecast ahead for southeast Wyoming and western Nebraska
with multiple hazards. Arctic fronts tend to do this over this
general area, so decided to focus on the initial threat of
snowfall and the arrival of the arctic airmass. Will not go into
too much detail with wind chill temperatures since the primary
focus will be snowfall and snowfall rates in addition to the
arrival of the bulk of the arctic airmass.
Timing of the arctic cold front appears on track, and it should
start to sneak into our northern zones (Converse, Niobrara, Dawes
Counties) after midnight tonight, and moving into northern
Colorado sometime around sunrise Monday morning. Still not
detecting any freezing drizzle or fog at the arrival of the front.
We are pretty confident there will be some near the Laramie Range,
but the snowfall should begin pretty rapidly after FROPA, so will
not include fog in the forecast at this time mainly due to low
confidence in timing. Models continue to show better dynamic
forcing and higher snowfall rates in the Carbon County/Albany
County region. Models show two individual shortwaves, with the
western shortwave splitting as it ejects east. This shortwave will
likely be responsible for most of the snowfall across the area
where the current Winter Storm headlines are currently in effect.
The shortwave to the north will quickly eject east early on Monday
bringing snowfall to the northern plains. The southern shortwave
is expected to slow down on Monday as it ejects east as a surface
low forms in Utah and moves eastward into Colorado. This surface
low will bring enhanced convergence to the Continental Divide
region along with impressive overrunning/isentropic lift as the
arctic front dives southward. ECMWF and GFS even more aggressive
with strong frontogenesis and high OMEGA across all of Carbon and
western Albany county compared to this time yesterday. As the high
res guidance is starting to arrive at the beginning of this
event, two primary areas are highlighted to possibly receive
upwards 1 to 2+ inch per hour snowfall rates (The mountains should
do very well with this system regardless, possibly up to 2 feet
of snow in areas); which are west central and south central Carbon
County and a secondary area along the northern Snowy Range
foothills. Model QPF and WPC QPF support the dynamic forcing in
this area, so expect a moderate to high chance of 8+ inches of
snow with locally higher amounts near a foot. Decided to upgrade
the Winter Storm Watch to a Winter Storm Warning for all of Carbon
County given the ample dynamics and potential snowfall rates. In
addition, pressure gradient will reverse behind the arctic front,
resulting in strong gusty winds coming out of the east for the
I-80 Corridor from Rawlins to Arlington. Expect some blowing and
drifting snow, which will add to the already dangerous travel
conditions. With lesser snowfall amounts further east, issued a
Winter Weather Advisory for the Laramie Valley and the I-80
Summit. There are some uncertainties with this system, such as the
timing of the arctic front, when it stalls near the mountains,
and moisture source. If the front stalls further south (or north)
and the position of the surface low over Utah is stronger/weaker
than expected, this could change snowfall rates and snowfall
totals. However, given how consistent models have been, confidence
in these possibilities are relatively low.
Further east, mainly along and east of the I-25 corridor, lower
confidence overall in snowfall amounts. Kept the Winter Storm
Watch going for Platte County extending northeast into Dawes and
Sioux County in the northern Nebraska Panhandle. This is mainly
due to the energy splitting as the southern upper level trough
slows down in Utah/Colorado. All models show a piece of this
energy ejecting northeast into the SD/eastern Wyoming area, with a
secondary QPF maximum around Niobrara and Sioux/Dawes counties.
Dynamic forcing will mostly be from the upper level jet max.
Models indicate an enhanced area of upper level diffluence near
the right-entrance region of the departing jet. Combined with
shallow upslope flow along the Pine Ridge, snowfall totals could
exceed 6 inches in addition to periods of one half inch to one
inch per hour snowfall rates. Currently most confident with this
general area for a potential upgrade to a Winter Storm Warning
with lighter amounts between the northern Laramie Range and the
I-25 corridor near Douglas and Wheatland. Further south, pretty
confident in 1 to 2 inches along the I-80 corridor from Cheyenne
to Sidney with an overall lack of forcing. Another concern is the
snow ratios. If the bitter cold airmass moves into the high
plains too fast, the dendritic growth zone will be a bit too cold
and fail to live up to the 15:1 to 20:1 snow ratios. Leaning
towards high end Advisory amounts or low end Warning amounts at
this time with all this in mind. However, this area on the Pine
Ridge east of Lusk towards Chadron have observed higher snowfall
totals compared to forecasted snowfall in more than one occasion
this season. Considering that the start of the snow will be later
than areas further to the west, figure we have another few more
model runs to add the specific details.
For Monday night and Tuesday, arctic airmass starts to settle over
the region. For low and "high" temperatures, blended CONSALL and NBM
10 Percentile which give us low temperatures in the single digit
to teens below zero and highs in the single digits on Tuesday,
which some locations remaining below zero through the day up
north. There is a chance that most locations may remain below zero
through the day on Tuesday east of Carbon county. Wind Chill
Temperatures will likely be brutal for late February with readings
between 25 below and 40 below zero through early Tuesday morning.
.LONG TERM...(Tuesday night through Sunday)
Issued at 124 PM MST Sun Feb 20 2022
The main focus of the long term forecast is the brutally cold
temperatures that will continue through the week, as well as
opportunities for light snowfall on Wednesday. There is also some
forecast uncertainty regarding the exit of the arctic airmass next
weekend.
On the synoptic scale, a deep 500-mb trough will dig well to the
south across the Great Basin on Tuesday evening as the initial
shortwave responsible for our first round of snowfall clears out to
the east. There is some uncertainty in the timing of the break in
moisture Tuesday afternoon through Wednesday morning. If dry air
moves in a little slower and the clouds break on Tuesday night, we
could see temperatures drop below the current forecast. However,
soundings seem to show the low levels remaining fairly moist so even
if the mid levels dry and clear, the low clouds could keep
temperatures from bottoming out too much. The GFS shows increased
moisture pushing in from the south by 06z, with light snow returning
to the I-80 corridor through Wednesday. This second round lacks
significant jet support, and the strongest 500-mb vorticity will be
well to our south. However, there will be some warm air advection at
700-mb and weak upslope easterly flow in the arctic airmass in the
lowest levels. Forecast soundings show the warm nose reaching the
dendritic growth zone over Cheyenne Wednesday morning, but not
expecting significant QPF due to the lack of deep ascent and support
for snowfall rates. More likely, this will be a prolonged round of
light snow with very low rates through Wednesday night before the
trough axis shifts east on Thursday. The mountains could stand to do
a little better with this second round with moist southwest flow,
but again the best moisture and dynamic forcing remains to our
south.
With thick clouds overhead on Wednesday, it looks unlikely the
arctic airmass will budge at all. We`ll be looking at another day of
very cold temperatures with highs in the single digits, and some
areas possibly staying below zero all day again. The cold may relent
some on Thursday, but we will still be well below average, and
struggle to reach the teens.
As the longwave trough shifts east on Thursday into Friday, guidance
is starting to show another shortwave dive south over the northern
Rockies. The GFS shows a decent round of mountain snowfall with
moist northwest flow amounting to nearly 0.5 in. additional QPF in
the Snowy Range by Saturday morning. The European shows much more
paltry QPF with ensemble support. Cluster analysis reveals that the
main difference in these outcomes can be traced to the strength of
the 500-mb ridge off the west coast. The European and its ensembles
show a narrow but intense ridge building off the west coast of North
America, reaching the Yukon in northern Canada. This effectively
cuts the shortwave off from the moisture source of the Pacific,
leading to the dry solution. The GFS and Canadian as well as their
ensembles display a shallower and more progressive ridge, extending
hardly much further north than the US/Canada border, which allows
moisture to flow over the top of the ridge and supply the passing
shortwave.
That divergence in the models also extends to the duration of the
arctic airmass next weekend. The GFS shows the ridge shifting
eastward quickly behind the shortwave Saturday, leading to nice warm
air advection by Sunday with the arctic air long gone and above
average temperatures returning. The European is much slower to push
the ridge through to the east, resulting in temperatures returning
to slightly below average by Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 422 PM MST Sun Feb 20 2022
Wyoming TAFS...VFR at Rawlins until 16Z, then MVFR until 19Z, then
IFR. Wind gusts to 35 knots until 10Z.
VFR at Laramie until 19Z, then MVFR until 21Z, then IFR. Wind
gusts to 32 knots until 02Z, then to 25 knots after 19Z. Low level
wind shear from 05Z to 16Z.
VFR at Cheyenne until 18Z, then IFR. Wind gusts to 25 knots until
21Z.
Nebraska TAFS...VFR at Chadron and Alliance until 12Z, then MVFR
until 17Z, then IFR. Wind gusts to 27 knots until 03Z, and to
30 knots after 12Z.
VFR at Scottsbluff until 17Z, then IFR. Wind gusts to 22 knots
until 06Z, then to 25 knots after 13Z.
VFR at Sidney until 20Z, then MVFR. Wind gusts to 33 knots after
15Z.
&&
.FIRE WEATHER...
Issued at 159 PM MST Sun Feb 20 2022
No fire weather concerns due to extreme cold & widespread snow.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Watch from late tonight through Tuesday morning for
WYZ101>103-106-107.
Winter Weather Advisory from 3 PM Monday to 11 AM MST Tuesday
for WYZ115-116.
Winter Storm Warning from 5 AM Monday to 11 AM MST Tuesday for
WYZ104-105-109>111-113.
Winter Storm Warning from 11 PM this evening to 11 AM MST
Tuesday for WYZ112-114.
NE...Winter Storm Watch from late tonight through Tuesday morning for
NEZ002-095.
&&
$$
UPDATE...AW
SHORT TERM...TJT
LONG TERM...MN
AVIATION...RUBIN
FIRE WEATHER...CLH/TJT
Area Forecast Discussion
National Weather Service Jackson MS
546 PM CST Sun Feb 20 2022
.UPDATE...
Updated for 00Z aviation discussion
&&
.AVIATION...
00Z TAF discussion:
VFR conditions will continue to prevail through the evening, then
dropping to MVFR by around 09Z at KGLH/KGWO/KJAN/KHKS, and around
12Z for KGTR/KMEI/KHHBG/KPIB due to low stratus. Categories will
continue to drop during the afternoon to IFR and some locations
may see LIFR conditions all due to shower and thunderstorm
activity, lowered ceilings and some reduced vis. Winds could gust
to near 20kts in the Delta as well tomorrow. Sites will remain
below VFR through the rest of the forecast period. /28/
&&
.DISCUSSION...
Today and tomorrow...
The remainder of this afternoon will remain mostly clear with a
couple of mid-level clouds developing. Some low stratus clouds
have already moved into our southwest CWA and will continue to
develop further northeast throughout the evening and overnight.
Low RH values in the northwest combined with sustained winds up to
15 mph are continuing to pose a "Limited" risk for fire weather
for this afternoon. By this evening, sustained southerly flow will
allow an unstable, moist, Gulf airmass to lift into the W-SW
portions of the region.
Tomorrow, the beginning of a rainy and wet week will begin with a
"Marginal" risk for severe weather in the W-NW portions of our CWA.
Mid-level lapse rates ranging between 7.0-7.5 C/km will allow for
sufficient mid-level convection to generate storms in the early
morning hours. Throughout the day, moisture and instability will
increase as the unstable airmass continues to lift to the north.
This will allow for scattered to widespread showers and
thunderstorms continue throughout the day. The main risk for severe
weather will bring the isolated potential for damaging winds, hail,
and a tornado can`t be ruled out. /AJ/
Tomorrow night through Saturday...
As the trough deepens over the desert southwest, the flow remains
southwesterly aloft, ejecting a series of small waves through the
region. The first of which is the low moving into the Midwest and
dragging dragging a front into the region tomorrow night.
Increasing southerly flow with a tightening pressure gradient will
pull warmer temps/more moisture/increasing instability overnight.
Forecast soundings show little CAPE early on, but moderate mid
level lapse rates and both low directional and deep layer speed
shear at least in the northwest will be contribute to a marginal
severe risk for whatever storms remain in the overnight hours.
Tuesday, guidance is creeping up with the high temperatures climb
into the upper 70s/low 80s with the prev precip and increasing
southerly winds enhancing bl RH. As a result, the afternoon MUCAPE
values increase quite a bit ahead of the cold front that will
likely be moving into steep low level lapse rates. One concern is
the northerly trend in the track of the sfc low as it moves from
the SW to the NE. The further away from the region it gets, the
less height falls/support for organized severe. But again, the
deep shear and advancing cold front will collide with decent
MUCAPE dependent on forward motion/timing of the front later Tues
afternoon and evening. The timing of the boundary is tricky and
not coincident with the advancing line of convection in the
various model runs...losing some of its forward motion getting
hung up a bit in parallel flow aloft. With that in mind...the HRRR
latest runs have been more discrete in the development of
cellular storms in the warm sector that may encompass a large
portion of the forecast area. For now, much of the forecast area
remains in a slight risk for Tuesday afternoon/evening.
With the front slipping into more parallel flow aloft, the cold
front is less of a scouring out than we have seen recently, and
instead acts as a focus for a series of disturbances to produce
periodic rainfall...and the remainder of the week stays dominated by
precip. Temperatures eventually get more of an impact from the
cooler air filtering into the region with the western trough
eventually moving out to the NE. But the temperature forecast from
midweek on through the weekend is low confidence given the impact of
periodic precip...not to mention that the ECMWF at least builds in a
ridge over the Gulf Coast somewhat limiting how far south some of
that cold air can get. Eventually the deep low over the SW lifts
across the CONUS late Thursday/Friday, bringing another chance for
storms potentially on Friday/Friday night.
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 53 70 62 81 / 59 91 22 71
Meridian 50 67 59 79 / 48 90 27 59
Vicksburg 55 74 64 82 / 61 90 13 66
Hattiesburg 52 73 62 80 / 30 68 11 50
Natchez 55 75 65 82 / 48 81 7 65
Greenville 51 70 64 79 / 21 90 43 80
Greenwood 52 68 62 79 / 15 93 55 84
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
28
Area Forecast Discussion
National Weather Service New Orleans LA
844 PM CST Sun Feb 20 2022
...EVENING UPDATE...
Performed a gridded update this evening to reflect recent short-
range guidance and obs trends. It`ll continue to be quiet tonight
underneath mostly cloudy skies. 00Z KLIX RAOB indicated multiple
moist/cloudy layers aloft sandwiched between a few small
subsidence inversions but overall we remain within a weak
veering/return flow pattern. We will begin to see tightening low-
level isoheights/attendant wind magnitude increase over the
south/central Plains and MS valley region through the rest of the
night in response to surface cyclogenesis over the Rocky Mountain
Front Range. Closer to here, we`ll see a very weak and subtle
mid-level impulse/PVA will ride northeast along southwesterly
flow. Meanwhile, isentropic ascent steadily increases
characterized by an enhancement in 300k moisture transport
magnitude aligned well with a corridor of total moisture fetch
from coastal Texas, northeast across central LA and into central
MS. Recent 00Z HRRR trends catch on this increase in low to mid-
level ascent by developing elevated showers and thunderstorms
early Monday morning (after 06Z) right within this zone of best
lift. Not going to entirely rule out some southward extent of this
activity likely getting into areas along/north of I-10/12
daybreak Monday, and have made no changes to NBM 1hr PoPs as a
bias into recent HRRR guidance looks very realistic. Only lower
confidence is for areas south of I-10/12 where upglide/forcing is
minimalized but is within deeper total moisture... can`t rule out
drizzle in a weakly forced environment but overall, better rain
chances today will be towards the north this morning/afternoon.
Worthy to mention about the overall environmental conditions today
within this area of scattered showers and storms, we will see a
gradual increase in surface to low-level moisture throughout the
day thanks to increasing southerly return flow. But, as the better
low to mid-level dynamic ascent drifts northeast, it will carry
any elevated showers/storms with it likely leading to conditions
becoming more dry this evening and into Monday night.
Additionally, NBM <1sm fog probabilities for this morning remain
relatively low (lower than 10%), but low clouds will continue to
remain thicker this morning within a moistening vertical profile.
Deterministic NBM MaxT`s did come in on the lower end of the 25th
to 75th percentile ensemble spread, and this looks very plausible
given the potential for thicker cloud cover (mostly cloudy skies)
throughout the day. So no major changes were needed for
temperatures on Monday. KLG
&&
PREV DISCUSSION... /issued 359 PM CST Sun Feb 20 2022/
SHORT TERM (TONIGHT THROUGH WEDNESDAY)...A persistent deep layer
southwest flow regime will continue in the mid and upper levels
through Wednesday night. A series of fast moving and weak
vorticity maxima embedded within this deep layer flow pattern will
pass through the Mid and Lower Mississippi Valleys during this
period of time. A persistent south-southeast will be in place in
the low levels, and this flow pattern will usher in a warm and far
more humid airmass. Temperatures are expected to be well above
normal with lows warming from the 50s tonight into the lower to
middle 60s for Monday, Tuesday, and Wednesday nights and highs
climb into the upper 70s and lower 80s. The two primary impacts
from this warmer airmass moving into the region will be an
enhanced risk of sea fog impacting the area each night and higher
risk of showers and thunderstorms forming each afternoon.
The fog risk will tend to peak both Tuesday and Wednesday nights
when onshore flow of around 10 to 15 knots, high dewpoints in the
lower 60s, and continued strong warm air advection passing over
cooler nearshore waters allows for saturation of the airmass to
occur. As a result, fog is expected to develop over the nearshore
waters starting as early as Tuesday evening and then spread inland
through the overnight hours. The fog will likely be dense at
times, and will be slow to clear during the morning hours on
Wednesday. In fact, the nearshore marine zones and locations
along the immediate coast may stay fogged in throughout the entire
day given the ideal fog conditions in place. Dense fog is
expected to spread back inland Wednesday night and linger through
Thursday morning.
The convective risk will peak on Tuesday when surface based
thunderstorms are most likely to occur, but the risk of
thunderstorms will be in place for Monday and Wednesday as well.
Model sounding analysis indicates that decent mid-level lapse
rates will be in place through the entire short term period with
lapse rates peaking at nearly 7C/km tomorrow before falling back
to between 6.0 and 6.5C/km for Tuesday and Wednesday. These lapse
rates will be supportive of deeper updraft development as a series
of weak upper level disturbances pass north of the area and
briefly increase upper level forcing across the area. Tomorrow
will find the area beneath the right entrance region of an upper
level jet streak. Upper level lift will increase due to this jet
structure, and this lift will tap into the steep mid-level lapse
rates and a building pool of moisture to produce non- surface
based thunderstorm activity tomorrow. Low level lapse rates will
remain very weak tomorrow as the airmass gradually modifies from a
cool and dry regime into a warm and humid regime. Convective
chances will tend to be highest across the northern third of the
CWA where forcing is expected to be greatest.
As mentioned earlier, surface based convection will be most likely
on Tuesday as the low level airmass becomes fully modified. Lapse
rates will rise above 6.0C/km in the low levels and these lapse
rates will support MLCAPE values of nearly 1000 J/KG by Tuesday
afternoon as temperatures climb into the upper 70s and lower 80s.
A very subtle upper level trough axis will slide through the area
on Tuesday, and this will provide the lift necessary to spark off
updraft development and thunderstorm activity. Model sounding
analysis indicates that shear parameters will be marginally
favorable for some strong to possibly severe thunderstorm activity
Tuesday afternoon, but the higher threat of severe weather will be
north of the CWA. If any severe storms form, damaging wind gusts
and hail will be the primary concern given the decent mid-level
lapse rates in place. The severe threat and thunderstorm threat
will quickly diminish in the evening hours as temperatures cool
back into the 60s and a thick marine layer airmass takes hold in
the low levels. By Wednesday, the convective risk will be
significantly lower as mid-level lapse rates weaken to around
6.0C/km and a weak shortwave ridge slides through drying out the
mid-level atmosphere a bit. At most, a very isolated thunderstorm
may form over parts of Southwest Mississippi or metro Baton Rouge
late Wednesday afternoon as temperatures climb into the 80s, but
any convection will be low topped and sub-severe.
LONG TERM (THURSDAY THROUGH SUNDAY)...The models are decent
agreement and overall forecast spread is on the lower end through
Friday, but then model spread begins to increase substantially
over the weekend. Again, this is tied directly into the timing of
these weak and fast moving southern stream vorticity maxima
sweeping through the Plains and into the Tennessee and Ohio
Valleys over the weekend. Given the model differences in place and
the large degree of spread noted, have opted to stick with the NBM
solution for the upcoming weekend.
A deeper shortwave trough will move into the Midwestern states
Thursday night into Friday, and a cold front will be driven
through the forecast area in response Thursday night into Friday
morning. In advance of this front, a fairly widespread dense fog
event is expected to occur Thursday morning, but increasing
gradient flow and forcing in advance of the approaching trough
axis should break up this fog and stratus bank by the afternoon
hours. Some compressional heating may also take hold in advance
of this system, and have very warm high temperatures in the mid
80s forecast for Thursday afternoon over much of the area. Despite
the warm temperatures in place, weak lapse rates aloft will
inhibit most deeper convective development, and no thunderstorm
activity is currently expected. At most, some passing light rain
showers can be expected Thursday afternoon and evening in advance
of the cold front. However, in the immediate wake of the front,
strong isentropic forcing is expected and this will allow for a
broad region of light rain and some elevated thunderstorms to
overspread the area late Thursday night into Friday morning. The
isentropic forcing will ease by the afternoon as the front pushes
further offshore and this will lead to drier weather moving in by
Friday evening. Temperatures will be significantly cooler as cold
air advects in from the north with highs only warming into the 50s
and lower 60s on Friday.
The NBM solution was used for the weekend forecast, and this
solution indicates that ridging and drier weather will dominate on
Saturday along with continued cooler than average temperatures. By
Sunday, the NBM is indicating that another cold front will slide
through the area with scattered showers and a reinforcing shot of
cooler air into the area. Temperatures will remain below average
with highs in the 60s and lows in the plunging into the 30s and
40s for Sunday night.
AVIATION (00Z TAF DISCUSSION)...
Expect primarily VFR conditions to prevail this evening into
portions of tonight with a BKN to OVC mid-level cloud deck in
place. Low clouds will build in early Monday morning introducing a
lower stratus deck with MVFR ceilings ranging 1000 to 2000ft AGL.
Additionally, some light showers will be possible as a warm front
surges north with main impacts being temporary reductions in VIS
reaching IFR at times. Otherwise, patchy low CIGs will persist
through the day as showers drift north going into Monday evening
with no additional impacts expected in the TAF period. KLG
MARINE...A persistent south-southeast flow of 10 to 15 knots will
develop tonight and continue through tomorrow as a ridge axis
extends west across the eastern Gulf of Mexico. The pressure
gradient should increase slightly tomorrow night into Tuesday as a
low pressure system passing north of the area deepens, and a
period of 15 to 20 knot winds and slightly higher seas can be
expected. As this low pulls away, winds will fall back into the 10
to 15 knot range for Wednesday and Wednesday night. A big concern
from Tuesday night through Thursday morning will be the risk of
sea fog impacting the coastal waters as a warm and humid airmass
advects into the area. By Thursday night, a cold front will begin
to move through the coastal waters. This front should clear the
marine zones by Friday afternoon, and a much colder airmass
advecting in will push winds into small craft advisory range for
Friday and Friday night.
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 55 75 65 82 / 40 70 10 60
BTR 57 79 66 82 / 20 50 10 50
ASD 54 76 63 79 / 10 40 10 40
MSY 58 77 66 79 / 10 30 10 40
GPT 54 71 62 72 / 10 30 10 30
PQL 51 72 60 76 / 10 30 10 20
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&
$$