Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/15/21
Area Forecast Discussion
National Weather Service Glasgow MT
815 PM MST Sun Feb 14 2021
.DISCUSSION...
800PM UPDATE:
Going forecast looks on track and no changes are expected this
evening. GAH
AFTERNOON DISCUSSION:
The most notable change from the previous forecast is with respect
to precipitation potential on Tuesday. While some of the typical
blended ensembles are trending towards almost no chance of
precipitation over the region, many of both the higher and lower
resolution deterministic models are painting a fairly broad brush
of slight chances for some precipitation. Thus, the forecast this
afternoon was altered to trend somewhat more towards the
deterministic solutions. However, the rest of the forecast remains
fairly unchanged and is in good shape. Cliff
MORNING DISCUSSION:
With the worst of the coldest winds chills finally moving behind
us as today progresses, we will be able to recover from the this
prolonged cold spell. Even though the coldest temperatures and
most dangerous wind chills will end later this morning, the Wind
Chill Warning will likely need to be replaced by a Wind Chill
Advisory. Will let the next shift handle that to avoid public
confusion will multiple headline products at the same time.
The unusually cold arctic air mass will shift more toward the
Great Lake region later today which will allow the beginning of a
shift in the weather pattern, bringing more moderating
temperatures to northeast Montana.
No great ridge of warm high pressure is forecast, but something of
a more progressive NW flow is expected amid a more relaxed
temperature field. Thankfully, as this next week progresses,
temperatures will steadily climb to above freezing by the latter
half of the week.
It should be noted that from Monday evening through Tuesday
morning, that a subtle embedded short wave disturbance has begun
to introduce slight chances for snow moving into portions of NE
Montana. Light accumulations if any are expected.
Otherwise, most of the expected precipitation over this next week will
be confined to the more terrain-induced areas of central and
southern Montana.
&&
.AVIATION...
FLIGHT CAT: VFR - MVFR
DISCUSSION: A few high clouds will pass over the area, with no
impact to flight conditions through Monday morning. During the
afternoon skies will become overcast and ceilings may lower to
MVFR at KGGW by the early evening. MVFR conditions may spread to
other locations Monday night.
EXTREME COLD: Temperatures below zero the next couple nights will
cause mechanical and equipment problems for aircraft and airfield
operations.
WIND: Southeast to east at 5 to 15 kts through Monday morning.
increasing to 15 to 20 kts in the afternoon and evening Monday.
GAH
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory until 11 AM MST Monday for Central and
Southeast Phillips...Central and Southern Valley...Daniels...
Dawson...Eastern Roosevelt...Garfield...McCone...Northern
Phillips...Northern Valley...Petroleum...Prairie...Richland...
Sheridan...Southwest Phillips...Western Roosevelt...Wibaux.
&&
$$
weather.gov/glasgow
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
625 PM CST Sun Feb 14 2021
.UPDATE...
Updated for 00Z aviation discussion
&&
.AVIATION...
00Z TAF discussion:
A mix of IFR/MVFR cigs wl prevail at all sites through the TAF
period. The initial round of -FZRAPL is moving through the ne.
Wl see increasing chances after 06Z from west to east of FZRA,
PL, and SN which will impact each TAF site to various degrees
through Monday. Combined with cold ground conditions, freezing
rain accumulations on airport runways and parked aircraft will
be a concern through the TAF period. /22/NF/
&&
.DISCUSSION...
This Evening through Monday Night:
A wave of sleet and freezing rain showers is currently moving across
the forecast area this afternoon, and it will continue to produce
sleet and ice across primarily areas of Mississippi north of
Interstate 20 through the evening. Elsewhere, light freezing drizzle
and the occasional light shower of freezing rain, sleet, or light
snow will still be possible. Persistently cold air temperatures and
ground temperatures mean that any precipitation through tonight will
cause impacts as it lands on roadways and bridges. Zooming out to
the bigger picture, the main shortwave trough to our west is
crossing the Southern Plains today. A deep swath of moisture being
advected north over our shallow Arctic air mass can be seen as
colder cloud tops on water vapor and infrared satellite imagery over
East Texas and Oklahoma this afternoon. As this greater lift and
moisture spreads east with the approaching trough overnight, the
forecast Winter Storm will develop across our area into tomorrow.
Threat impact areas are largely unchanged from the going forecast,
but we did decide to outline an area of "Extreme" threat from
freezing rain to the Hazardous Weather Outlook text and graphics.
Details are included in the precip type/amounts section. Extremely
dangerous temperatures are also expected Monday night (lows from 5
degrees in the Delta to 15 in the Pine Belt), and that threat
remains unchanged in the HWO text and graphics.
Winter Storm Timing: Temperatures will continue to drop tonight,
with even the Pine Belt waking up to temperatures around freezing in
the morning. Delta temperatures will be in the mid-teens range.
Short-term guidance is in good agreement that the onset of our next
round of precipitation will be around Midnight in northeast
Louisiana and southeastern Arkansas. By 2 or 3 a.m. Monday, wintry
precipitation will begin to overspread portions of western
Mississippi and extend across the eastern half of Mississippi by 6
a.m. The main wave of heavier precipitation looks like it should
move across the forecast area between 6 a.m. and around 3 p.m.
Monday. As the axis of the shortwave trough passes overhead through
the evening, colder and drier air will begin to undercut the
precipitation and subsidence aloft will bring and end to precip from
west to east. It would not be a surprise to seem some linger
freezing drizzle or flurries into the Monday night hours, but
accumulations should end by the evening.
Precipitation Types/Amounts: Given the Arctic air mass in place
heading into tonight and tomorrow, the biggest factor in determining
precip type will be the depth of warm air in the elevated warm layer
and the intensity of precipitation. For the sake of the forecast, it
has been assumed most accumulating precip will begin as snow aloft,
experience at least partial melting, and then refreeze as it falls
through the subfreezing boundary layer. In far southeast Arkansas,
far northeast Louisiana, and Delta counties of Mississippi, it`s
expected that precip type will be mostly snow after a brief period
of freezing rain and sleet. In those areas, colder boundary layer
temperatures and less warm air aloft should allow heavy
precipitation to overcome any partial melting. Snow and sleet
accumulations of up to 4 to 6 inches could occur in these areas.
Through more central portions of Louisiana and a southwest-northeast
corridor of central Mississippi, the depth of warm air aloft looks
to sustain primarily freezing rain and sleet through most of the
event. Precip totals will be tricky depending on type, but generally
expect up to 1 to 2 inches of sleet and snow, and between one
quarter to three quarters of an inch of ice from freezing rain. The
Extreme threat area lies where the consensus of guidance indicates
these greater ice accumulations. More widespread damage to trees and
power lines is expected through this corridor. Lastly, the far
southeastern and eastern portions of Mississippi will most likely
see either rain or freezing rain through most of the event, with
periods of sleet mixing in with heavier precipitation. Up to around
one half inch of sleet and up to around one quarter inch of freezing
rain is expected in those areas. Expect some possible errors in the
gradients between primary precip type areas. /NF/
Tuesday through Saturday:
After an extremely cold night, temperatures Tuesday will remain
quite cold despite the clearing skies. The shallow arctic airmass
and the frozen precipitation on the ground will prolong the cold
conditions as highs for most of the area remain in the 20s with
30s in the far southeast and lows Tuesday night dropping back into
the teens and 20s.
The persistent mid level southwest flow will bring the next system
into the area Wednesday with another round of wintry weather
possible. The track of the surface low looks to be further north
with this system as it hugs the northern Gulf coast. While the surge
of warm air in advance of the system will be strong, the leftover
ice will serve to hang onto the cold air at least until the heavier
precipitation begins. Thus, northwest portions of the area will
remain cold enough for long duration, accumulating winter weather
again Wednesday into Thursday.
Another surge of cold air will follow this system, but high pressure
shifting quickly east by the weekend will turn the wind to the south
and allow for a warmup to begin Saturday as 40s and 50s are expected
with values near 60 over the far southeast. /GG/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 23 25 11 29 / 72 100 3 0
Meridian 28 32 13 35 / 37 100 7 0
Vicksburg 20 22 10 28 / 85 100 2 0
Hattiesburg 32 35 15 38 / 50 99 5 0
Natchez 21 24 11 33 / 85 99 0 0
Greenville 16 18 6 23 / 88 100 2 0
Greenwood 18 21 7 25 / 83 100 3 0
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...Winter Storm Warning until 6 AM CST Tuesday for MSZ018-019-
025>066-072>074.
LA...Winter Storm Warning until 6 AM CST Tuesday for LAZ007>009-015-
016-023>026.
AR...Winter Storm Warning until 6 AM CST Tuesday for ARZ074-075.
&&
$$
NF/22/GG
Area Forecast Discussion
National Weather Service Louisville KY
932 PM EST Sun Feb 14 2021
.Forecast Update...
Issued at 930 PM EST Sun Feb 14 2021
First wave of precip is on our doorstep, and multiple reports of
accumulating sleet have been noted out of Middle TN. AMDAR soundings
in and out of BNA have shown a warm layer around 2-3 C, but a deeper
low level cold layer. BWG fcst soundings show a shallow 1-2 C warm
nose centered at 5 kft AGL - classic sleet profile. So the main
concern with the moderate precip spreading northeast toward south-
central KY is significant accumulations of sleet. Expect sleet to
cover roadways. Sleet is likely to be the dominant p-type south of a
Russellville KY to Lexington KY line between now and 12z Mon. After
about 10 pm CST, travel is not recommended in south-central KY
including Russellville, Bowling Green, Scottsville, Glasgow, etc.
By 09-12z Mon, a stronger warm nose over the Lake Cumberland region
will support greater freezing rain chances as opposed to sleet being
the primary p-type.
Issued at 702 PM EST Sun Feb 14 2021
Increased wintry precip chances a couple hours early and introduced
freezing drizzle for the next few hours generally east of I-65
and south of the BG Parkway. We received a report of a freezing
mist in Berea. A multi-car crash was also reported on I-75 in
Rockcastle Co, near the Madison Co line. Very light wintry precip
could very well cause additional issues on the roads this evening
before widespread heavier wintry precip moves in after midnight.
Light icing will be possible from this evening through tomorrow
morning in the first phase of the winter storm, mainly along and
east of a Bowling Green to Lexington line. Freezing rain totals
could reach a tenth of an inch in Monroe, Cumberland, and Clinton
counties.
&&
.Short Term...(This evening through Monday)
Issued at 250 PM EST Sun Feb 14 2021
...Major Winter Storm Set to Come in Two Waves Tonight and Monday...
...Monday Morning Travel Disruptions Likely...
...Significant Travel Disruptions Monday Afternoon/Evening Very
Likely...
Main focus in the short term is on the significant winter storm that
will impact the region in two separate waves. The first wave will
arrive tonight and continue into tomorrow morning. The second, more
potent wave will arrive tomorrow afternoon and continue into the
overnight hours.
The first wave is currently near the ArkLaTex region at this hour
and will steadily approach the region overnight. Modest isentropic
lift and other upper level forcing mechanisms will support
widespread precipitation developing by midnight over much of central
Kentucky and southern Indiana. Temperature profiles across southern
Indiana will support snow, while south of the river but northwest of
the Bluegrass/Western Kentucky Parkways we`re likely to see a
sleet/snow mix, and more freezing rain southeast of the Parkways.
Snow amounts will range from one to three inches, with most
accumulations generally across southern Indiana and portions of
north-central and western Kentucky. Ice accumulations will generally
be under a quarter inch with this first wave across the southeast.
We are likely to see a decline in coverage and precipitation
intensity by mid morning, and that could continue into the
afternoon. During this timeframe, we lose some saturation aloft
where ice crystal growth is favored, so precip types may favor
freezing rain/drizzle briefly in places as far north as the Ohio
River. This could put down a thin layer of ice on snow/sleet that
has already fallen.
The 2nd, more potent wave will begin arriving across south-central
Kentucky shortly after noon CST/1pm EST, and work its way into the
rest of Kentucky and southern Indiana by mid to late afternoon.
Colder air will wrap around this 2nd wave a bit more than the first,
so we`ll gradually see that transition zone of snow/sleet/freezing
rain shift eastward through the day into the overnight hours.
Excellent upper level forcing and lift combined with deep moisture
will favor some heavy snow rates at times, some of which could
exceed 1"/hour. The heavy snow potential is most likely along and
northwest of the Parkways Monday afternoon into the overnight hours.
Precipitation will gradually end from southwest to northeast Monday
night, with all precipitation clearing the region before dawn
Tuesday.
While models continue to shift where the transition zone will set up
across the region, there is fairly high confidence that locations
along and west of the I-65 corridor will see a period of heavy snow
Monday afternoon and night that will have significant impacts on
travel. Travel will likely become treacherous, if not near
impossible, for a time in those areas.
The accumulation portion of the forecast continues to be tricky, and
largely depends on where the transition zones set up. What we can
say is that in areas that see all or mostly snow (generally west of
I-65), snowfall accumulations by Tuesday morning will likely range
from 6 to 9 inches with some locally higher amounts. If the
transition zones end up being much farther east (colder model
solutions), then that 6 to 9 inch swath of snow could extend as far
east along a line from Lexington (KY) to Bowling Green (KY). East of
those areas, it appears the warm nose aloft will be too strong to
support snow for most of the event, though they are still likely to
see 1" to 3" on the backside of the system as it departs (in
addition to all of the sleet and freezing rain). The Lake Cumberland
region could see ice accumulations exceed 0.25" by the time
everything is wrapped up Tuesday morning.
.Long Term...(Monday night through Sunday)
Issued at 250 PM EST Sun Feb 14 2021
...Another Winter Storm Possible Wed Night - Thu...
In the wake of the exiting system, expect a brief period of some
quieter weather through the first part of Wednesday as surface high
pressure moves across the Great Lakes region. May just see some
flurries linger during the day on Tuesday as we remain saturated in
the lower levels through the DGZ. Under steady CAA, temperatures
will be rather chilly with highs in the lower to mid 20s and wind
chills in the teens. Overnight lows into Wednesday morning are
progged to be in the lower to mid teens, with some areas dipping
into single digits. As we move back into southwesterly flow during
the day Wednesday, highs will be a bit warmer in the upper 20s to
mid 30s for most.
Attention will then turn to our next potential winter storm that
will move through the area Wednesday night and Thursday. The
synoptic pattern will feature a large upper trough digging across
the Plains and moving eastward towards the region, placing the OH
Valley in deep SW flow. A strengthening 850 mb jet will pump ample
moisture into the region as the trough approaches. At the surface, a
low pressure system will develop over the western Gulf and progress
northeast towards the Mid-Atlantic. As this system moves through,
another prolonged period of winter weather will be possible across
central KY and southern IN.
Precipitation chances will begin to increase across the area
Wednesday afternoon with the heaviest precipitation expected then
overnight into Thursday. Continue to see a decent amount of
variability among model guidance regarding the track of the storm
and temperature profiles over the area which will have a large
impact on p-type with snow, sleet, freezing rain and cold rain all
possible at this point. It appears a significant amount of snow and
sleet will be possible across the area and perhaps another swath of
significant ice accumulations, although location remains very
uncertain at this point. In general, better snow/sleet chances will
be across southern IN and northern KY with better freezing rain/rain
chances across southeast KY. Will continue to monitor how this
trends in coming days.
As this system exits to the east on Friday, drier conditions are
then expected for the end of the week and into the weekend as
surface high pressure centered over the Deep South builds in across
the area. Temperatures on Friday will remain well below
climatological normals with highs in the mid to upper 20s. As the
high begins to move off to the east on Saturday, temperatures should
begin to moderate closer to normals with highs in the 30s.
&&
.Aviation...(00Z TAF Issuance)
Issued at 655 PM EST Sun Feb 14 2021
MVFR conditions across the region this evening with an OVC deck
around 1300-2800 ft. HNB is currently at VFR, but expect them to
drop to MVFR tonight as snow chances move into the region. Expect to
see wintry precip begin late tonight at at all terminals. SDF and
HNB will likely see all snow, while BWG and LEX will likely see a
snow/sleet mix. Wintry precip will continue overnight and into
Monday morning. Cats should drop from MVFR to IFR overnight with
the incoming snow. We could see a bit of a break in precip between
12-18z Monday, evident by slightly improving vis guidance, but
still expect cats to be MVFR.
Second wave of precip comes Monday afternoon and into the end of
this forecast period. This second wave poses a better chance of at
least moderate snowfall, with LIFR cats possible. There also is
potential of some heavy snow Monday afternoon, which could drop
visibilities to VLIFR cats at times.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...Winter Storm Warning until 1 PM EST /noon CST/ Tuesday for
INZ076>079-083-084-089>092.
KY...Winter Storm Warning until 1 PM EST /noon CST/ Tuesday for
KYZ023>043-045>049-053>057-061>067-070>078-081-082.
&&
$$
Update...EBW
Short Term...DM
Long Term...JML
Aviation...CJP