Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/07/21
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
431 PM MST Sat Feb 6 2021
00Z TAF CYCLE
The leading nose of a strong 80-100kt jet max skirts over northern NM
bringing another round strong winds near mountain top level. Mountain
wave activity will bring some of this energy to the surface in a
hit-and-miss fashion immediate lee of the Sangre de Cristo Mountains.
KLVS is the most favored TAF terminal, but confidence is low on when
exactly this starts, so started with TEMPO before higher confidence
of stronger winds during the early morning hours of Sunday. LLWS will
also be a concern at KLVS before these strong winds reach the
surface, and this LLWS impact could stretch eastward over the
northeastern plains as far as KTCC, but lower confidence of if this
reaches below 2k ft keeps this mention out of the TAF for now.
Elsewhere for most areas south of I-40 or west of U.S. 550 will see
winds decouple overnight with breezy to windy westerlies returning
.PREV DISCUSSION...300 PM MST Sat Feb 6 2021...
Strong west to northwest winds will continue through early Sunday
along and east of the central mountain chain, with occasional gusts
up to 60 mph. Daytime highs will edge 5-15 degrees above normal
across much of the state through Tuesday. However, a pattern change
is in store, as arctic air begins to settle into the eastern portion
of the state as early as Monday night. Widespread wintry
precipitation is possible by late week.
SHORT TERM...(TONIGHT THROUGH SUNDAY NIGHT)...
The short term is essentially a wind and temperature forecast
through Sunday night. The short term high resolution models continue
to indicate what would be a high wind event for the peaks and east
slopes of the Sangre de Cristo mountain later tonight, and the HRRR
spreads some of the stronger winds towards and into the I-25
corridor in spots, later tonight. Some of the guidance is hinting
the stronger winds will also spread farther south along the east
slopes, impacting the Clines Corners area. Went ahead and upgraded
the existing High Wind Watch to a Warning and added the Las Vegas to
Raton area as well. Also put the Central Highlands and Guadalupe
County in a Wind Advisory, and expect that may be extended or
expanded into Sunday afternoon, as guidance indicates the wind could
taper off a bit in the morning, then increase again Sunday afternoon
as the surface low over eastern NM deepens. Highs Sunday will be
about 5-15 degrees warmer than normal, and overnight lows will range
from about 5-10 degree warmer than average, despite the very dry
airmass across eastern and southern NM.
LONG TERM...(MONDAY THROUGH SATURDAY)...
The flow becomes a bit more westerly on Monday, although breezy to
windy conditions may still persist along and east of the central
mountain chain, where 700 mb winds are still reaching 45-50 kts.
Otherwise, temperatures will be 5-15 degrees above normal on Monday.
By as early as Monday night, an arctic air mass begins to creep into
northeastern New Mexico. The shallow mass seems to retreat slightly
on Tuesday, as it gets eroded by the westerly flow. With a strong
1050 mb high parked over Canada (almost 2-3 STD`s of normal), the
cold air once again tries to advance Wednesday and Thursday, with a
gap wind potential for the middle Rio Grande Valley Wednesday night.
From here, the 12z GFS run shows the arctic air making it to the
central mountain chain by Friday, with temperatures 25-30 degrees
below normal across the eastern plains. The ECMWF keeps the arctic
mass confined to the eastern portion of the state and snow mainly
confined to the northern mountains. Decided to make very little
changes to the max/min temperatures in the extended, given the low
confidence in recent model guidance trends.
Dry northwest flow aloft into Tuesday trends more westerly mid to
late next week. Another round of strong to possibly damaging winds
is expected along the Sangre de Cristo mountains again tonight.
At least localized critical fire weather conditions are likely
Sunday and again Monday in an area from near Las Vegas to Clines
Corners, Corona to Santa Rosa and back to Las Vegas. Fair to poor
overnight humidity recoveries will be followed by sub 15 percent
minimum humidities and warmer than normal high temperatures both
Sunday and Monday afternoons. However, only low to moderate
instability is forecast, and that was the deciding factor at this
time, for holding off on issuing a Fire Weather Watch.
A very cold airmass will progressively ooze westward over eastern NM
Tuesday through Friday, although forecast models differ whether or
not and when the cold air could make it into the Rio Grande Valley.
This may not happen until Friday night or Saturday.
Humidity values area wide will trend higher by mid to late next
week, as temperatures cool down. There will be chances for snow over
the north starting late Tuesday, then spreading into the east by
Thursday or Friday.
Wind Advisory from 10 PM this evening to 8 AM MST Sunday for the
following zones... NMZ212-223-233.
High Wind Warning from 10 PM this evening to 8 AM MST Sunday for
the following zones... NMZ213>215-227>229.
Area Forecast Discussion
National Weather Service Binghamton NY
931 PM EST Sat Feb 6 2021
After a mostly clear evening, a coastal storm system and a
weaker system moving through Central NY will bring snow to the
area on Sunday, especially during from the late morning to the
early afternoon. Lake effect snow showers then develop east of
Lake Ontario Sunday night into Monday. Colder weather is
expected next week with multiple passing disturbances and
resultant chances for snow.
.NEAR TERM /THROUGH SUNDAY NIGHT/...
With the evening updates, adjustments were made with
temperatures and dewpoints based on the radiational cooling and
amount of dry air in place. Dewpoints have been consistently
several degrees below model guidance and this concern extends
into the snowfall expected tomorrow. A look at mesoscale model
guidance this evening shows a considerable amount of mid level
dry air to overcome before snow can even reach the ground. The
one exception is the new 00Z NAM. For now, we did account for
the latest HRRR and RGEM trends as well in addition to the NAM
and lowered snowfall totals slightly in the advisory area
tomorrow. Previous discussion below.
Temperatures begin to level off a bit after midnight as clouds
increase ahead of the next system. Lows will likely be in the
teens, with some single digit readings across the higher
elevations of Central NY and northern Oneida County.
On Sunday, a strengthening coastal low pressure system will
quickly track from off the North Carolina coast to off the
southern New England coast. Meanwhile, a separate shortwave will
swing from the Great Lakes through Central NY. While the
expected track of the coastal low has shifted slightly further
north and west the last few days, the greatest impacts from snow
still look to be south and east of our forecast area (closer to
the coast). That being said, our two eastern-most counties
(Pike and Sullivan counties) will likely be close enough to see
3-5 inches of snow, especially across the eastern half of these
counties. Snowfall rates there may approach 1 inch per hour at
times late Sunday morning into the early afternoon. Expected
snowfall amounts decrease further west. Generally 2-4 inches of
snow is expected for the rest of the Poconos. Should this
coastal low track a bit further north and west than expected,
snowfall amounts may end up being a bit higher, especially for
Pike and Sullivan counties. With this forecast package, we have
issued a Winter Weather Advisory for Pike, southern Wayne,
Lackawanna, and Luzerne counties in PA; Sullivan County in NY.
At the same time, a shortwave will be moving through Central NY.
This will bring a round of light snow to much of the rest of the
region with generally 1-3 inches of snow expected. Otherwise,
snow from these two systems gradually tapers off by the late
afternoon, before lake effect snow showers in portions of
Central NY begin. Highs on Sunday will be mainly in the upper
20s to lower 30s.
While the majority of the area dries out Sunday night, a west-
northwesterly flow will bring some scattered lake effect snow
showers for the Finger Lakes Region to the NY Thruway corridor.
An additional inch or two of snow will be possible. Aside from
the associated lake effect clouds for these regions, a general
clearing trend is expected overnight. Lows will likely be in the
single digits to lower teens.
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Some lake-effect snow will remain possible Monday across areas east
of Lake Ontario in wake of Sunday`s quick-moving storm system. The
greatest odds of seeing additional accumulations will likely occur
during the morning, before a weak surface high moves east of the
region Monday night. Additional snowfall amounts of an inch or less
Southerly winds should return Monday night as the surface high moves
to the east. Low-level moisture will increase and isentropic
upglide will approach from the south/west ahead of the next in a
series of fast-moving weather systems. The result will be another
possibility of snow (especially) from late Monday night and continue
through most of Tuesday as the storm system moves across the
Weak perturbations, embedded in the upper-level, flow will interact
with any remaining moisture as they continue traversing the region.
So even though the storm system is expected move offshore, we`ll
still see some lingering lake-effect snow probabilities continue
into Tuesday night.
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
A relatively low-amplitudinal weather pattern is expected to remain
across the forecast area for the end of the week, as an upper low
spins around in the Canadian Prairies. This will allow an unsettled
weather pattern to continue during the Day 4-7 period with at least
a small possibility of snow just about every day.
There`s some indication that the upper-level flow will amplify
across Mid-America as a couple of disturbances rotate around the
upper low. The first piece of energy will likely aid in the
development of low pressure near the spine of the Appalachians,
probably somewhere around the Tennessee Valley. Meanwhile, a
second, possibly stronger piece of energy may dive into the Northern
Plains toward the end of the week. This could lead to the storm
system strengthening as the surface low heads northeastward and
starts to interact with the (possibly) stronger upper-level support.
Honestly, there`s lots of uncertainty in the timing/evolution of
this end-of-the week storm system. For now, it looks like the odds
of seeing snow will likely increase Thursday and continue through
most of Friday as the storm system moves across the forecast area.
By next Saturday, the snow machine will likely transition to more of
a lake-effect setup. Given the uncertainty, I don`t plan on
straying too far from the model blend. Time will tell, though. Stay
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
Mostly VFR conditions through the first half of the forecast,
but conditions will start to deteriorate tomorrow morning. A
storm off the Mid- Atlantic coast along with a separate weaker
system swinging into Central NY will bring snow to the region
starting somewhere between 12 - 15Z tomorrow. Associated IFR
visibility restrictions can be expected in snow. With the snow
moving in from the south, KAVP will be the first terminal to
see restrictions, shortly followed by the remainder of the
terminals. Conditions will start to improve by mid to late
Sunday afternoon with the snow completely out of the region
before 0Z Monday.
Sunday night through Monday...Scattered lake effect snow showers
may bring some occasional restrictions to the Central NY
terminals, mainly KSYR and KRME.
Monday night through Thursday...Scattered snow showers and
associated restrictions from a couple of clipper systems
passing through, and lake effect snow showers.
PA...Winter Weather Advisory from 6 AM to 7 PM EST Sunday for
NY...Winter Weather Advisory from 6 AM to 7 PM EST Sunday for
Area Forecast Discussion
National Weather Service Cheyenne WY
414 PM MST Sat Feb 6 2021
.SHORT TERM...(Late this afternoon through Sunday night)
Issued at 315 PM MST Sat Feb 6 2021
Broad upper trough spans coast to coast across the Lower 48 with
its center axis from the Upper Midwest to the southern Great Plains.
Short wave energy tracking southeast from southwest Canada into the
central Rockies was producing areas of accumulating snow. The arctic
front extended from western MT through southeast WY and northeast
CO. Temperatures east of the front remained in the teens, while 20s
and lower 30s prevailed to the west. A tight pressure gradient was
generating strong winds west of the front with gusts of 50 to 60 mph
at Arlington and Elk Mountain.
Forecast challenges during the short term will be snow accumulations
with the next short wave trough and strong winds impacting portions
of south-central and southeast WY.
The aforementioned short wave trough will move southeast along the
arctic boundary tonight and Sunday morning. After receiving over
three feet of snow from the last two short waves, lift from the
left front quadrant of 130-kt upper jet and orographics will produce
more snow for the Snowy and Sierra Madre mountains, with up to a
foot expected. A Winter Weather Advisory remains in effect from 5
PM this afternoon until noon Sunday. Areas from east-central WY into
the NE Panhandle can expect one to three inches of snow through
Sunday morning. Snow tapers off Sunday afternoon as the upper jet
shifts east and orographic lift wanes.
With the arctic front retreating slowly east into the high plains
during the next 12 to 18 hours, strong westerly surface winds will
become more prevalent, with a belt of 50-60 kt 700mb winds spreading
east along the I-80 corridor from early this evening through Sunday.
CAG-CPR 700/850mb heights exceed 60 meters through 00Z Monday. CAG-
BRX gradients are lower and local high wind probabilities peak near
45 percent between 03Z and 09Z Sunday, then sharply decline. GFS/MET
sustained winds range between 30 and 35 kt at Rawlins beginning
shortly after 00Z, and at Laramie after 06Z. Went ahead an issued
High Wind Warnings for Central Carbon County including Rawlins,
Upper North Platte River Basin including Saratoga and Laramie Valley
including Laramie from 5 PM this afternoon through 5 PM Sunday.
The High Wind Warning for Arlington/Elk Mountain continues through
5 PM Sunday. Also extended the Winter Weather Advisory for snow and
blowing snow for Arlington/Elk Mountain through 5 PM Sunday with
an additional one to three inches of snow. Areas outside the High
Wind Warnings like Cheyenne and Bordeaux may experience wind gusts
up to 50 mph Sunday.
A weaker short wave trough quickly passes through Sunday night and
early Monday with another inch or two of snow from east-central WY
into the northern NE Panhandle, as well as the Snowy and Sierra
.LONG TERM...(Monday through Saturday)
Issued at 315 PM MST Sat Feb 6 2021
The extended forecast period will be dominated by broad upper
trough, with the central Canada polar vortex rotating south and
east into the northern CONUS during the mid to latter part of the
week. The arctic front will lie over the high plains early in the
week, then sink south through WY and NE mid to late week with
unseasonably cold temperatures (25 to 35 degrees below normal) and
700mb temperatures plummeting to -30 to -35 Celsius. Not expecting
any strong wind episodes, but gusty winds will make it feel bitterly
cold with wind chills lowering to -15 to -30 degrees. Several pieces
of short wave energy rotating through the base of the upper trough
will keep weather conditions unsettled with daily chances for light
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 411 PM MST Sat Feb 6 2021
Used latest HRRR and LAMP guidance for the 00Z TAFS. Band of snow
and low conditions east of the Laramie Range this evening that
slowly lifts northeast across the northern Panhandle...creating
IFR/LIFR conditions. Increasing winds for southeast Wyoming
airports with high wind warnings in effect for KLAR and KRWL.
Obscured mountains in snow...overall poor flying conditions for
the evening and overnight.
Issued at 317 AM MST Sat Feb 6 2021
With cold temperatures, several chances for snow, and an arctic
cold front across the high plains through this weekend and early
next week, no fire weather concerns are expected. The coldest air
of the season will make it into interior Wyoming by later this
week as a strong arctic cold front moves south and west. Chances
for accumulating snow are expected to continue through next week.
WY...Winter Weather Advisory until noon MST Sunday for WYZ112-114.
High Wind Warning until 5 PM MST Sunday for WYZ109-113-115>117.
High Wind Warning until 5 PM MST Sunday for WYZ110.
Winter Weather Advisory until 5 PM MST Sunday for WYZ110.
Area Forecast Discussion
National Weather Service Dodge City KS
455 PM CST Sat Feb 6 2021
.SHORT TERM...(This evening through Sunday)
Issued at 357 PM CST Sat Feb 6 2021
The first little taste of what is going to end up being a very long
period of well-below normal temperatures pushed into southwest
Kansas earlier today. The temperature at DDC has been slowly falling
through the day from the upper 20s mid morning to 22F at 2115Z. The
temperature at Hays was 19F. Low stratus was certainly mitigating
any slight warmup we would have otherwise seen amidst the cold air
advection out of the northeast.
The first shortwave trough continued to push quickly east away from
the Central Plains, and the next disturbance was moving into
Montana, which will continue its trek southeast tonight. Winds in
the low levels will respond to this next wave, as they veer in
direction from northeast to southeast and eventually due south --
that is, the low level winds except right at the surface. Now that
the shallow arctic airmass was making its way south across Kansas,
it will be very difficult to dislodge now that it`s in here. That
said, even the surface winds will veer around to a strong southerly
component as pressure continues to fall across eastern Colorado. A
west-northwesterly downslope momentum surge will develop during the
day Sunday across eastern Colorado, greeting the shallow arctic
airmass. It will be a classic "battle" between the downslope warming
and the stubborn shallow arctic airmass. Usually the shallow arctic
airmass wins these battles, especially when low stratus clouds are
involved with low sun angle of early February.
There is quite the contrast in afternoon temperature among the
various models for tomorrow afternoon. Valid 21Z Sunday, the WRF-ARW
and HRRR are by far the warmest, with west-northwest surface winds
surging all the way east to Dodge City, effectively scouring out the
stratus and warming DDC to the mid to upper 50s. On the other side
of the coin, we have the Canadian RDPS model that keeps the surface
winds east-southeasterly all day, stratus in check, resulting in a
21Z temperature at DDC of 32F. The official forecast will have an
afternoon temperature at DDC topping out around 40F, and I believe
that this is optimistic, as experience has shown that the colder
solutions tend to win out in these situations. So, the range across
our forecast area for Highs tomorrow will be 55F at Elkhart on the
warm end and 24F at Hays on the cool end. It is entirely possible
Hays will not escape the teens again.
The second surface wave will pass by to our south Sunday Night, with
easterly low level winds reinforced. very light precipitation in the
form of mainly flurries will likely develop north of the surface
feature. We have added flurries to the forecast for Sunday Night
across all of the forecast area, however accumulating snow is
currently not anticipated.
.LONG TERM...(Sunday night through Saturday)
Issued at 357 PM CST Sat Feb 6 2021
The next push of arctic air on Monday will be stronger into western
Kansas, and this will really mark the beginning of our extended cold
wave which will last this entire forecast period through the next
weekend (13-14 Feb). This will likely be one of the longest lasting
cold waves in several winters at least. Official high temperatures
each day from Monday through Saturday will be teens to 20s across
much of the forecast area. Elkhart area will be traditionally
warmer, but even Elkhart will not escape a significant chunk of
this arctic cold wave, especially as we head deeper into the week.
On the larger hemispheric scale, the long wave gyre (or polar
vortex) will hold firm across southern Canada, with influence from
Hudson Bay all the way west across the southern Canadian Prairie of
Saskatchewan and Manitoba. Over the course of the upcoming week, the
gyre will slowly shift west, which will keep the larger polar jet
shape broadly cyclonic across the northern CONUS. This pattern will
keep MSLP anomalously high east of the Canadian and Northern
Rockies, effectively keeping the core of the arctic airmass
unchanged both in magnitude and location, outside of daily
oscillations due to the synoptic/subsynoptic features rippling
through the cyclonically curved pattern. Each of these waves through
the end of the week will bring a round of light snow to portions of
the Great Plains, only adding to the ever-increasing snowpack. An
ever-increasing snowpack just to our north (and perhaps including
portions of western Kansas later in the period) will only help to
keep this cold wave going. There is the suggestion in today`s model
runs that by the end of the week and/or weekend that a southern
stream storm system entering the West may interact with the northern
branch jet, carving out a big storm with a substantial amount of
deep tropospheric baroclinicity to work with. This is getting ahead
of ourselves, though, with plenty of time to watch how this
component of the forecast evolves going forward. Regardless, this is
shaping up to be one of the longest duration cold waves we have seen
in quite some time, when all is said and done.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 455 PM CST Sat Feb 6 2021
Widespread MVFR stratus prevailed as of 2255z, with the exception
of SKC from EHA to LBL. After sunset, stratus will reestablish
and migrate westward, with ceilings lowering to IFR at all
airports. Winds will trend SE over the next few hours, with a
tight pressure gradient keeping SE winds elevated at 12-14 kts
overnight into Sunday morning. Stratus will attempt to clear from
west to east daylight Sunday, but there is high uncertainty on how
successful this process will be. This TAF package will show SKC
at GCK/LBL by 18z Sun, but there is high confidence that IFR/MVFR
stratus will hold at HYS all of Sunday. In between at DDC, allowed
the stratus to break by 21z Sun. Another cold front Sunday night
and Monday will bring a return to NE winds and more widespread
stratus, along with light snow potential 06-12z Monday.
.PRELIMINARY POINT TEMPS/POPS...
DDC 15 40 13 24 / 0 0 10 0
GCK 16 44 13 28 / 0 0 10 0
EHA 24 55 24 39 / 0 0 10 0
LBL 20 51 19 32 / 0 0 10 0
HYS 10 24 6 17 / 0 0 10 10
P28 16 32 17 26 / 0 0 10 0
Area Forecast Discussion
National Weather Service Quad Cities IA IL
917 PM CST Sat Feb 6 2021
Issued at 917 PM CST Sat Feb 6 2021
Watching trends tonight decided to adjust lows for the area. CAMs,
especially the HRRR have gone a lot more aggressive on low temps
tonight. Have reduced lows a couple of degrees. With this small
change, wind chills in the QCA metro are now below -30 for a
decent time. As such, have extended the warning into our area. The
urban areas in these counties may be sheltered from the worst
wind chills, but rural open areas will feel the full brunt of
these wind chills in the AM on Sunday.
Issued at 312 PM CST Sat Feb 6 2021
An arctic airmass was entrenched across the area this afternoon
with temperatures mostly in the single digits. Lift ahead of a an
upper level shortwave moving into NW Iowa was producing widespread
snow, with the heaviest axis reducing visibilities to 1/4 to 1/2
miles in places across southeast Iowa into west central Illinois.
Northwest winds were mainly in a 10 to 20 mph range, producing
some drifting of the powdery snow, but more importantly, lowering
wind chills to a range of around 5 below to 15 below zero and
slick roads. Very cold temperatures and wind chills and periodic
rounds of light snow will remain the theme this weekend going into
.SHORT TERM...(This Evening through Sunday)
ISSUED AT 312 PM CST Sat Feb 6 2021
Winter Weather Advisory:
The current round of light snow will end from west to east late
this afternoon west of the Mississippi River, then early this
evening to the east. The Winter Weather Advisory, for the forecast
area mostly along and south of the I-80 corridor in Iowa is set to
expire at 7 pm. In Illinois, the advisory covers areas along and
south of the I-88 corridor and is set to expire at 9 pm. Based on
current timing from radar and short term hi res models, this may
be on the generous side and it may be cancelled earlier. Snowfall
rates suggest an additoinal 1, to possibly 2 inches of powdery
snow possible, mainly in the heavier band over southeast IA into
west central IL in the advisory area.
Wind Chill Warning and Advisory tonight/Sunday:
Looking at Wind Chill headlines overnight: Just how cold it gets
will depend on cloud trends as a weak high moves in to decrease
winds some. Current satellite imagery shows the back edge of cloud
cover behind the shortwave over eastern SD, SE MN into NW IA, but
there is some high thin cloud cover streaming into the northern
plains in the NW flow aloft. Even without total clearing,
temperatures in this airmass should easily get into the negative
10 to 20 degree range over east central Iowa into NW IL and have
gone with lows in this range over all but the far south, where
mins are held in the single digits. Even with light NW winds, wind
chills will get into the vicinity of our -30 degree Warning
criteria over the north late tonight into early Sunday morning.
Have thus kept the warning going over east central Iowa into far
NW IL from 00Z til 18Z Sunday, although the main window of -30 or
lower will be mainly from roughly 08Z til 13z. The rest of the
forecast area has a Wind Chill Advisory going for the same
Sunday will see another upper level shortwave spreading light
snow across mainly the southern half of area from late morning
through afternoon. However the upper level forcing looks weaker
and takes a more southerly path, compared to the current event,
suggesting lighter amounts. The arctic air remains in place, thus
temperatures are progged to recover to afternoon highs only from
around zero to 5 above.
.LONG TERM...(Sunday Night through Saturday)
ISSUED AT 312 PM CST Sat Feb 6 2021
An active northwest flow pattern will remain across the area with
several chances for snow and a prolonged period of below normal
temperatures. Refer to the climate section regarding the temperature
Sunday night into Monday evening
Assessment...high confidence on two snow events occurring.
Medium on snowfall amounts
The first system will exit the area Sunday evening followed by a
brief lull before the next system arrives close to sunrise Monday.
Snowfall Sunday evening looks to be the heaviest south of I-80 where
up to an additional inch of accumulation is expected. North of I-80
snowfall amounts look to be one half inch or less.
On Monday the second system moves through the area. The potential is
there for headlines for this event.
The snow Monday into Monday evening will be a fluffy powder so
snow/rain ratios will be quite high; potentially 14-18 to one.
Snowfall should be heaviest during the afternoon with the snow
ending from west to east during the evening.
Right now the heaviest snowfall looks to be south of a Sterling, IL
to Sigourney, IA line with 2-3 inches expected. If snow/rain ratios
are higher than forecast I cannot rule out a narrow band of 4 inch
snowfall. North of a Sigourney, IA to Sterling, IL line snowfall
amounts of 1-2 inches are expected.
Late Monday night through Tuesday
Dry but cold conditions will be seen as high pressure moves through
the area. Given the forecast temperatures and wind the possibility
does exist for wind chill headlines for parts of the area late
Monday night into Tuesday morning.
Tuesday night into Wednesday night
Assessment...low to medium confidence
Currently the model consensus has dry conditions. However there will
be a weak upper level disturbance moving through the area. If
sufficient moisture is present this disturbance will have the
potential to produce minimally flurries if not some light snow given
the arctic air in place. Additionally wind chills may approach 20
below zero for parts of the area both Tuesday night and Wednesday
Thursday and Thursday night
The model consensus has slight chance pops for snow on Thursday.
However all the global models have a respectable upper level
disturbance moving through the area. This disturbance is associated
with a storm system that moves up the Ohio Valley.
Digging deeper into the model consensus there are some timing and
track differences that are causing the overall pops to be lower. The
overall synoptic set up would support minimally likely pops Thursday
afternoon/evening. Snow/rain ratios will be at least climatology
(13:1) and may be higher. Thus another round of accumulating snow
looks on tap that may require headlines at some point in the future.
Friday into Saturday
Assessment...high confidence on much below normal temperatures. Low
confidence on dry conditions.
The model consensus has dry conditions as yet another arctic high
builds into the Midwest. Headlines for the cold will likely be
needed for next weekend.
However it is not clear whether or not dry conditions will be seen.
An upper level disturbance associated with the arctic front will
move through the area Friday and Friday evening. The forcing from
this front may be enough to generate some light snow during its
Saturday should be dry given the arctic airmass over the area.
.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
ISSUED AT 542 PM CST Sat Feb 6 2021
Snow is moving out of the area and vsbys and cigs are starting to
improve. Expect VFR about 2 to 4 hours after snow ends. Overnight
into tomorrow AM expect VFR conditions. Sn will move back into the
area around 18z across the far south. Vsbys could be 1sm in
heaviest snow after 18z.
Issued at 312 PM CST Sat Feb 6 2021
The longwave pattern across the northern hemisphere consists of 3
waves in the high latitudes and 4 waves in the low to mid latitudes;
a fairly stable pattern. The anchoring wave is a deep trof over
Siberia which creates a ridge over the eastern Pacific and a deep
trof over the eastern part of North America.
The high amplitude flow pattern is progged to de-amplify around the
middle of February as it transitions to 4 waves in the high
latitudes. As a result the AO pulls out of the current deep negative
readings but most ensemble members remain negative through late
February. A majority of the ensemble members keep the PNA slightly
positive through late February as well. The NAO trends toward
neutral by mid-February but a few ensemble members trend negative
again after mid-February.
The MJO has strengthened and propagated across the Indian Ocean
during the past week. However there is considerable spread and
uncertainty over the next two weeks regarding further eastward
propagation of the MJO across the Maritime Continent and into the
western Pacific. This uncertainty and ensemble spread is due to
destructive interference from La Nina. La Nina conditions persist
across the Pacific but have weakened slightly since mid-January.
Week 2...February 13-19
Taking all this into consideration indicates a very high probability
of below normal temperatures through the middle of February across
The Climate Prediction Center week 2 outlook has a 70-80 percent
chance of below normal temperatures through February 19th with a
high risk of well below normal low temperatures February 13-15.
Precipitation should average below normal through the middle of
February based on outgoing longwave radiation (OLR) anomalies.
Week 3-4...February 20 through March 5
Looking further out the experimental week 3 and 4 outlook from the
Climate Prediction Center has a 50-55 percent chance of below normal
temperatures across the Midwest. If correct, the potential exists
for below normal temperatures to continue through the end of
February and into early March.
IA...Wind Chill Warning until noon CST Sunday for Benton-Buchanan-
Wind Chill Advisory until noon CST Sunday for Des Moines-Henry
IL...Wind Chill Warning until noon CST Sunday for Carroll-Jo Daviess-
Wind Chill Advisory until noon CST Sunday for Bureau-Hancock-
MO...Wind Chill Advisory until noon CST Sunday for Clark-Scotland.
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
647 PM CST Sat Feb 6 2021
Issued at 642 PM CST Sat Feb 6 2021
Updated to add one more tier of counties on the south side of the
existing winter weather advisory due to southward shift in recent
UPDATE Issued at 543 PM CST Sat Feb 6 2021
We plan to slide our heavier snow band for tonight a bit further
south based on the 18Z NAM and the most recent runs of the HRRR
and RAP. We will mainly be increasing snow amounts in the
Hastings, Grand Island, Kearney area and on the south side of the
current forecast snow band. Generally now expecting another 3-5
inches in the Tri-Cities tonight into Sunday morning. The best
frontogenesis will be over our area around 3-6 AM Sunday morning and
we will see most of the snow falling through a large dendritic
growth zone given the very cold temperatures. Therefore, expect a
nice 20:1 ratio making a light and fluffy snow.
.DISCUSSION...(This evening through Saturday)
Issued at 422 PM CST Sat Feb 6 2021
Outside of a few flurries here or there, seeing a lull in
precipitation across the area this afternoon...and satellite
imagery is even showing peeks of sunshine out there. Aloft,
upper air obs and satellite imagery shows the disturbance
responsible for the snowfall last night/this morning continuing to
push east, roughly sitting along the MO river. Snowfall amounts
portions of our Neb counties were a fairly uniform 3-5", a few
embedded higher amounts not out of the question. At the surface,
winds remain NNErly across the area, gradually diminishing in
speed through the day thanks to an area of high pressure settling
south through the Nrn/Central Plains. With a colder airmass
building into the area, temps haven`t really gone anywhere today,
even with the bit of sun...3PM obs ranged from the upper single
digits (above zero) in the far north/east, to mid teens across our
Tonight into the daytime hours on Sunday...
Those folks who are fan of snow will be happy to hear more is in
the forecast for tonight/Sunday! Increasing lift via another
upper level shortwave disturbance embedded in the overall
northwesterly flow and jet streak placement is expected to shift
into/through the area tonight, with the timing of the
precipitation pretty similar to last night`s event. In the grand
scheme of things, there hasn`t been any significant changes in the
models/forecast. A WNW-ESE orientated swath of moderate/at times
heavier snow is expected to mainly affect our south central NE
counties, with most models and the current forecast favoring the
higher amounts of 3-5" roughly along an Arcadia (Valley County) to
York line...lowering around an inch by the NE/KS state line.
However, am a little concerned about the potential for a slight
southward shift...something the incoming crew will have to watch
closely and things start to develop, and adjust accordingly.
Decided to issue a Winter Weather Advisory for a good chunk of our
Nebraska, all counties along/north of I-80 and Kearney- Fillmore
Counties along HWY 6. This area would catch most of a slight
southward shift in snow totals, but can`t totally rule out a few
counties being added...will just have to see how things
As far as timing goes, if anything the forecast is a touch slower
with the onset of precip, with mid-evening in the far west, to
around 06-09Z for the HWY 81 area. Decided to segment the
advisory, with a 03Z start time for counties west of HWY 281, 06Z
for counties along/east of HWY 281. Current thinking is the ending
will be similar to today...with not much going on in the
afternoon...and have an 18Z end time for the advisory.
Thankfully, with sfc high pressure building into the area, winds
won`t be a significant concern with this round of snow. Current
NNE winds will gradually turn more ESErly tonight/tomorrow, but
speeds look to top out around 15 MPH, and that`d be toward the end
of the event during the morning hours tomorrow.
Along with the potential for accumulating snow, forecast wind
chill values late tonight into tomorrow morning are expected to
drop below zero. In the Winter Weather Advisory, wind chills of
-15 to -20 are forecast, with -5 to -15 possible further south.
Forecast lows tonight are single digits (above and below zero),
with highs for tomorrow only forecast to reach around 7 in the far
N/E, around 10 in the Tri-Cities, and around 20 in the SW.
Sunday night into Monday...
Yet another disturbance/jet streak forcing brings another round of
snow to the area, though overall lift is a bit weaker. After a
brief lull in activity late in the day Sunday/Sunday evening, snow
will again spread from west to east through the overnight hours
into Monday morning...but overall looks to be fairly light in
nature. Current forecast additional accumulation peak in the 1-2
inch range, again over portions of south central Nebraska (similar
orientation/area to tonight`s event)...with around 0.5" in the
SW. Activity is again expected to taper off/end by midday Monday.
Wind continues to not be a significant issue with this snow
event...remaining easterly in nature with speeds around 10-15 MPH.
Overnight lows Sunday night-Monday morning are forecast to again
be in the single digits, with more spots expected to be below
zero...and even with the lighter winds, wind chill values of -10
to -20 are expected. Overall there is little change for highs on
Monday, with plenty of single digits above zero across our
Nebraska counties, lower-mid teens across our KS counties.
Tuesday through Saturday...
With the primary concern focused on tonight-Monday, felt no
changes to the blended grids were warranted. The main story will
continue to lie with the bitterly cold temperatures, which look
to continue right on through at least the end of this official
forecast period. Forecast highs see no improvement through the
week, topping out in the single digits-near 10 deg across most of
our Neb counties, more teens possible across KS. Dangerously cold
wind chill values will be possible each day...and even have values
further into the -20 to -30 degree range as we get into Fri AM
and Sat AM.
As far as precipitation chances go, models suggesting a bit more
of a break in the action through Tuesday. The current forecast
is also dry into Wednesday, but confidence in that is not high.
The overall upper level pattern remains zonal/progressive, with
the potential for periodic disturbances ramping back up mid-late
week, associated with a large area of low pressure looking to set
up over the central US/Can border.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Monday)
Issued at 543 PM CST Sat Feb 6 2021
The big story will be the snow that we expect again tonight,
generally 3-5 inches at our TAF sites with most of the snow
falling between midnight and 10 AM. Visibility will be IFR through
much of the snow event and even after the snow ends we can expect
at least MVFR ceilings through the rest of the day on Sunday. The
wind should not be overly strong and generally 10 to 15 mph out of
NE...Winter Weather Advisory from midnight tonight to noon CST Sunday
Winter Weather Advisory until noon CST Sunday for NEZ039-046-060-
Area Forecast Discussion
National Weather Service Goodland KS
545 PM MST Sat Feb 6 2021
Issued at 545 PM MST Sat Feb 6 2021
Current forecast for tonight generally on track with only minor
At the surface low pressure is currently extending from New Mexico
north into southeast Colorado and central Wyoming with a 1028mb
surface high in northeast Nebraska. For tonight the surface winds
become more southerly with the highest sustained speeds of 15 to
20 mph along and west of the CO/KS border. Surface dewpoints
slowly rise along and west of the CO/KS border as well as surface
temperatures. So for those along the CO/KS border low temperatures
will be occuring now through early this evening before becoming
steady or even slowly rising overnight. Further east in the deeper
arctic air little change in temperature is expected from current
readings. So in summary low temperatures are expected to range
from the 5-10F range from McCook to Hill City and points east to
the mid and upper teens along and west of the CO/KS border.
Regarding snowfall potential...another weather disturbance is
forecast to move southeast through the area tonight with support
from a 120kt 300mb jet moving over the area. These jet dynamics
along with following better 850-500mb relative humidity and
favorable dendritic layer temperatures in the 600mb layer supports
the current forecast of a mention of snow flurries or chances of
light snow mainly north of a line from Flagler to Goodland and
Oakley. Snow ratios are a little higher compared to previous shift
but given the very light QPF snow amounts of a few tenths of an
inch dont change much. The highest chances for any accumulating
snowfall are generally north of a line from Yuma to Hill City.
Will take another look at any potential forecast changes in about
an hour as 00z NAM and short term RUC/HRRR data comes in.
.SHORT TERM...(This evening through Sunday night)
Issued at 238 PM MST Sat Feb 6 2021
Satellite imagery and 500 mb RAP analysis showed northwest flow
persisting above the High Plains early this afternoon. A series of
shortwaves embedded in the flow above the central Rockies, paired
with a cold front lingering in the southwestern part of the region,
generated cloud cover and occasional light snow/flurries today for
our area. Fog was also observed across much of the region behind
the cold front. At 2:00 PM MST, temperatures were in the teens and
20s across the region, with east to southeast winds at 10 to 15
Little change is expected in the large scale pattern this weekend,
with continued northwest flow aloft and cold air in the low to mid
levels. Areas of fog may linger this evening along and west of the
Colorado border. Winds turn to the south and increase tonight as a
surface trough strengthens along the Rockies and the pressure
gradient tightens. With low temperatures largely in the single
digits and teens, a disturbance looks to bring another round of
light snow to areas along and north of Interstate 70 this evening
through the overnight hours. Only light accumulations (less than
0.5") are currently expected.
On Sunday, the surface trough along the Rockies nudges the
aforementioned cold front back into the region as a warm front. This
causes a difficult temperature forecast and a tight temperature
gradient across the region. Temperatures rise into the low 40s to
low 50s west of a line from Wray Colorado to Leoti, Kansas while
east of this line, highs will only reach into the 20s and 30s.
Otherwise, dry conditions are forecast, with southerly winds
shifting towards the north.
Guidance suggests that another wave will push through the northwest
flow Sunday night, leading to the potential for some light snow east
of a Trenton, NE to Hill City, KS line. West of this line, flurries
will be possible for the remainder of the region. Low temperatures
will be a bit colder than previous nights, in the single digits and
.LONG TERM...(Monday through Friday)
Issued at 224 PM MST Sat Feb 6 2021
Next week continues to look cold with a few chances for light snow.
Wind chills are likely to get colder as the week goes on and could
reach advisory criteria, especially later in the week though some
The extended period will largely be dominated by two prevailing
patterns. Aloft, a broad 500mb trough will be situated over the
CONUS and put the Tri-State area under northwest flow for much of
the time period. At the surface, model guidance continues to suggest
a battle between high and low pressure over the area. Higher
pressure will set up over the Central Plains and favor our eastern
locales. Lower pressure will set up over the desert southwest with
the potential for lows to come off the Front Range. This would put
the pressure gradient over the area with lower pressure and warmer
temperatures in Eastern Colorado and higher pressure with cool
temperatures further east. Guidance has been fairly consistent at
placing the steeper portions of the gradient along the Colorado
border. However, where exactly the warmer temperatures and cooler
temperatures divide has not been consistent. However, below normal
temperatures with well below normal temperatures further east has
been consistent. With these cooler temperatures, wind chills will be
in the negatives during the night across much of the area.
Monday through Wednesday are currently forecasted to be the warmer
and drier days though intermittent cloud cover is likely across this
time period. Precipitation looks to be unlikely due to the
relatively dry air that will be set up over the area and the
relatively high pressure moving in. However, with moisture possibly
moving in aloft, can not rule out some flurries or light snow. High
temperatures are forecasted to be in the mid 20s to lower 30`s near
the Colorado border and in the upper teens closer to McCook & Hill
City. Lows are forecasted to be in the single digits with wind
chills in the negative single digits.
Thursday & Friday are uncertain at the moment as model guidance
currently has diverging solutions for how the pattern will evolve.
The GFS is colder and drier as it has the trough circulating back to
the center of the country and digging south before pushing off to
the east. This would bring in even colder air from the north and
increase our surface pressure. The ECMWF also has the trough
circulating back to the center of the country but moving off to the
east without digging much further south. The ECMWF then also hints
at a surface low forming off the front range and moving close to the
Eastern Colorado border. This would increase our temperatures from
where they were and bring some snow to the area as some synoptic
ascent is provided. In spite of the differences, below normal
temperatures to finish the week remain likely in either scenario and
the trough should push off to the east to finish the week. However,
Situational Awareness tables still have the area under a Min
percentile anomaly for temperatures to finish the week. So the
potential for even colder weather with wind chills reaching -20
degrees F or less remains. Will have to continue to monitor how the
pattern will evolve and which solution emerges.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 346 PM MST Sat Feb 6 2021
Low ceilings prevail at KGLD and KMCK terminals tonight, as light
southeast winds turn to the south and increase. Similar to last
night, light snow is forecast for areas north of Interstate 70
this evening into the overnight hours. Have inserted a mention at
KMCK as a result, but anticipate snow to remain north of KGLD at
this time. On Sunday, a warm front backs into the region,
decreasing cloud cover from the southwest. KMCK looks to remain
socked in through the TAF period, but KGLD should see clearing by
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
922 PM EST Sat Feb 6 2021
Low pressure will spread moisture north across our region through
tonight then move off the East Coast on Sunday. Dry high pressure
builds back into the area on Monday. Unsettled weather is
possible through the rest of the week.
.NEAR TERM /THROUGH SUNDAY/...
As of 900 PM: Well, for everyone hoping to see snow across the I-85
corridor from the Gaffney area to Carnesville, GA, you`re happy
right now! A Winter Weather Advisory has been issued for those
areas, including the Greenville and Spartanburg areas, until 4 am
tomorrow morning. The 700 mb frontogenesis is quite strong and right
in the dendritic growth zone. This is further aided by strong DPVA
with an approaching upper trough over the Mid-South. Snow rates are
so heavy, that despite warm ground temps, accums are on roads and
are adding up fast. The HRRR keeps this band roughly in place thru
06z tonight, but rates should gradually weaken. Given the latest
snow reports, some locations from Seneca to Easley to Traveler`s
Rest and north may get warning criteria snow of 3"+. Slippery roads
will be the main concern overnight, but should improve early Sunday
morning, as precip changes back to rain and temps hover around 33-34
degrees. But in the meantime, roads are slippery across the Upstate
along and north of I-85!
Later tonight, still expect a warm nose to punch in and the
frontogeneis will weaken. there may be a lull in precip east of the
mountains, while additional precip moves in from the west associated
with the approaching upper wave. So no changes to the Winter Storm
Warning or other Advisory at this time.
Previous Discussion... As of 230 PM: A well defined shortwave is
moving toward Arkansas, on track to reach the southern Appalachians
by around daybreak Sunday. A relatively weak but dry sfc high is
present across the upper OH Valley and Eastern Seaboard; on the
southern fringe of this high is a stalled front. The shortwave
will pull the front northward as a warm front over the high,
with cyclogenesis occurring along the GA/SC coasts. In-situ CAD
is expected to develop as precip develops, with precip expected
throughout the CWA at some point tonight. The morning passage of
the shortwave axis will erode the CAD, end precip, and lead to
scattering clouds east of the mountains by midday Sunday. A minor
NW-flow snow event will occur along the NC/TN border in the early to
mid-morning timeframe. However, the main story for the period will
be the wintry precip developing within the CAD, mainly overnight.
Dewpoints being what they are in the teens and lower 20s on obs
from across the CWA, there appears a lot of dry air to overcome
before precip can accumulate at all. Thus, seems reasonable to
expect reasonably strong evaporative cooling at the onset of
precip. The midday HRRR runs seemed to have initialized the dry
air better than other models, and indeed the HRRR reflects the
wet-bulbing concurrent with its precip depiction. Still thinking
snow will predominate as p-type where temps are cold enough this
aftn/evening. That said, special 18z sounding from KFFC shows a
stronger warm nose than what any of the models depict, but the NAM
is closest. How far this warm nose works north and west, into the
area where temps are closest to or below freezing, will determine
the extent of the wintry precip. The models in general are closer
than they were yesterday at this time, though the NAM remains most
bullish in terms of WAA over the wedge. Thinking sfc temps however
are more likely to remain just above freezing in the area where
the warm layer is most in play. Thus, the transition zone between
rain and snow remains pretty sharp across the upper Piedmont and
Foothills, with sleet and eventually FZRA replacing snow in the
colder areas later tonight, after the best forcing has shifted
north and east. The loss of better upper level moisture, following
continuing northward motion of the warm front, also suggests FZRA
overtaking sleet/snow at some point, but by that time the remaining
chances will be mostly associated with the developing NW flow,
which would tend to be rime icing if not snow. Overall, thinking the
hazards are good as-is: Winter Storm Warning for the mountains of
GA/SC/NC as well as the northern NC foothills zones, and a Winter
Wx Advisory for the adjacent part of the NW NC Piedmont.
Gusty winds will occur in high elevations overnight and tomorrow
morning, at least, though the 850mb flow is not especially strong
and impacts from these winds are not expected to be enough for
any wind headlines. The aforementioned NW Flow snowfall in the
morning likely won`t amount to much particularly in light of
the overnight precip, but a few flurries could continue into
early afternoon. 850mb winds continue to be unimpressive in this
regard, which is another reason not to get that excited about
the NW flow. Temps will rebound into the 50s by afternoon across
the Piedmont, although if the clouds hang on a bit longer than
expected (which wouldn`t be that surprising, coming out of CAD),
that may be a little optimistic. The higher mountains will remain
near freezing, but the valleys should warm back into the 40s.
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 245 PM EST Saturday: The short-term forecast picks up at 00z
on Monday with heights recovering across the region as very broad
upper trofing lifts NE and flattened upper ridging builds to our
south. Our area will remain under nearly zonal upper flow thru the
short-term period and into the extended as upper ridging remains
centered to our south. At the surface, broad high pressure will be
spreading over our region as another robust Nor`easter moves farther
off the New England coast. The high will be fairly transitory and
will slide eastward and over the Atlantic Coast by late Mon/early
Tues. On Tues, another weak low develops along a moist frontal bndy
just to our west and pushes a weak cold front thru the CWFA Tues
aftn/evening as the period ends. Monday will be dry with solid chance
PoPs over most of the CWFA on Tues with the fropa. Any QPF that does
fall should be minimal (ie, no more than 0.1 inches for most zones).
Most of the precip that does fall should be rain, however temps do
appear to support light snow showers over the mtns and northern NC
Foothills early Tues. Any accums should be 0.1 inches or less.
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 220 PM EST Saturday: the extended fcst picks up at 00z on
Wednesday with flattened upper ridging to our south and very broad
upper trofing moving east of the Great Lakes. Over the next couple
of days, the sub-tropical upper ridge is expected to amplify to our
southeast as another upper trof begins to dig down across the Central
CONUS. For the remainder of the period, the long-range models remain
quite different with respect to the large-scale pattern evolution.
The GFS develops a much broader and deeper upper trof from Friday
onward while the ECMWF (and to a lesser extent the CMC), are much
more muted with respect to the trof`s amplification. At the sfc,
broad but relatively moist and transitory high pressure will be
spreading over the area from the NW as the period begins late Tues/
early Wednesday. Over the next 24 to 48 hrs, the high will shift
eastward and move over New England setting up a weak wedge/CAD over
the Carolinas. By late Thursday, another low will develop over the
ArkLaTex region and lift NE towards the Ohio River Valley by early
Friday. This will bring widespread precip to the fcst area for
Thursday and at least part of Friday. By the end of the period on
Saturday, robust-looking Canadian high pressure pushes its way
into the region with drier and much cooler air.
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
At KCLT, The latest forecast still looks like mostly rain, with
some sleet mixing in at times in the 03-07z time frame. As precip
intensifies, cigs and vsby should lower to IFR, with cigs getting
into the 300-400 ft range for the pre-dawn hours. Precip will taper
off to the east by daybreak, and cigs should start improving to MVFR
by late morning, and VFR by midday. Winds are starting out SE, but
should toggle to NE as some in-situ wedge forms, then gradually back
to N then NW, and increase slightly to around 8-10 kts in the aftn.
Elsewhere...Latest hi-res guidance is initializing a banding
feature better, and this looks to set up right along and north of
the KAND-KGMU-KGSP line, and over KHKY later this evening. If rates
are intense enough, could see periods of SN and PL mixing in and/or
changing over, but otherwise, expect predominately RA. At KAVL,
conditions support mostly SN, until after midnight, could start
see a changeover to PL. The banding feature will dissipate after
6z, but additional light precip will continue till around 12-14z
time frame. The precip will bring cigs and vsby down to IFR at
all sites (and LIFR where SN/PL), with improvement after daybreak
Sunday. VFR conditions expected after 16z, as low pressure system
exits to the east. Winds will favor a NE direction (except SE at
KAVL) with some cold air damming, but then toggle to N/NW at all
sites as low shifts east overnight.
02-08Z 08-14Z 14-20Z 20-00Z
KCLT Med 62% High 90% Med 76% High 100%
KGSP Low 46% High 83% High 84% High 100%
KAVL Med 75% High 98% Med 72% High 100%
KHKY Low 49% Med 79% High 85% High 100%
KGMU Low 53% Med 70% High 84% High 100%
KAND Low 57% High 84% Med 73% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables are available at
the following link:
GA...Winter Storm Warning until noon EST Sunday for GAZ010-017.
Winter Weather Advisory until 4 AM EST Sunday for GAZ018-026.
NC...Winter Storm Warning until noon EST Sunday for NCZ033-048>053-
Winter Weather Advisory until noon EST Sunday for NCZ035>037-
SC...Winter Storm Warning until noon EST Sunday for SCZ001>003.
Winter Weather Advisory until 4 AM EST Sunday for SCZ004>008.
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
714 PM EST Sat Feb 6 2021
Two weather systems, one moving east across the Great Lakes, and
the another moving east across the Tennessee Valley, will bring
a chance of snow to the region tonight. High pressure will then
establish itself across the area for Sunday and Monday.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Initial adjustment to guidance would have had a slightly warmer
min temp tonight, and given the snow that my still be a
possibility. However, did not feel that this trend was the way
to go given the origin of the upstream airmass. Adjusted temps
towards the HRRR and RAP which gave a very minimal drop, more in
the east than anywhere else. Remainder of the forecast seems to
capture this snow that will be falling tonight and winding down
in the east by daybreak. Earlier discussion:
For tonight, two main weather features will affect the Great
Lakes and Ohio Valley. An embedded disturbance is forecast to
move east/northeast across the Great Lakes. A band of snow is
expected to develop to our west and then move into the area.
Models indicate that frontogenetic forcing with this system will
weaken as the band of snow moves into our area. Thus, the best
chance for measurable snow will be across the Whitewater,
Miami, and west central Ohio locations. Farther south, another
embedded disturbance will move east across the Tennessee
Valley. Its precipitation shield may clip northeast Kentucky and
south central Ohio. Overall, an inch or less of snow is expected
with the northern and southern systems. Colder air will filter
back into the area by Sunday morning. The combination of the
cold temperatures and wind will lower wind chill temperatures
into the -5 to -10 range across the Whitewater, Miami, and west
central Ohio locations. Due to the combination of snow and wind
chill temperatures, have issued a Special Weather Statement for
that region. Lows tonight will range from near 5 in our
northwest to the lower 20s in the southeast.
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
There will be a chance of snow early on across our east Sunday
morning, then skies will gradually become partly cloudy as high
pressure moves back into the region. Again, wind chill
temperatures will range between -5 and -10 across our northwest
through at least mid morning. Some embedded disturbances within
the mid level flow aloft will bring an increase in mid level
cloudiness late. Highs will range from 10 to 15 in the northwest
to near 30 in the southeast.
It will be mostly cloudy Sunday night despite surface high
pressure. There will be a low chance for snow in the northwest
due to continuing weak disturbances rippling within the mid
level flow. Lows will range from near 5 northwest to the upper
.LONG TERM /MONDAY THROUGH SATURDAY/...
The extended period begins Monday with surface high pressure slowly
exiting east from eastern Ohio into the northeast states. As this
occurs, easterly flow develops at the surface with increasing warm
and moist southwesterly flow aloft. By Monday night, weak shortwave
energy will be lifting out of a digging upper level trough whose
axis extends from the upper Mississippi Valley through the Central
Though fine details differ, model guidance develops a chance of
light precipitation via weak isentropic lift Monday night, while
also suggesting temperatures near to slightly above freezing at
850mb -- especially along and south of Interstate 71. Using top-down
methodology, the warm air aloft provides some light freezing rain
and sleet potential to go along with light snow. In addition to the
uncertainty in the vertical temperature profile, there is also
uncertainty in how much QPF to expect in the weak forcing
environment. Forecast soundings display a relatively short time of
vertical saturation in a period otherwise dominated by cold and dry
surface air. For now, have included very light freezing rain mixed
with snow, with ice amounts less than a tenth of an inch Monday
For Tuesday and Tuesday night, the shortwave will exit to the
northeast as surface high pressure builds in to the Great Lakes. A
significant temperature gradient remains behind across the Ohio
Valley as colder air slowly sinks southeast. High temperatures will
range from the low 20s northwest to near 40 in the southeast during
the day, with lows bottoming out from near 10 in the northwest to
the low 20s in the southeast.
For the mid-late week period, a low amplitude upper trough sinks
into the Central Plains and ridging builds from the Gulf of Mexico
into the Mid-Atlantic states. Once again, this places the forecast
area in southwesterly flow aloft with stubborn cold air at the
surface. Though the pattern suggests the potential for light ice and
sleet mixing in, have held precipitation type to light snow at this
extended range due to uncertainty in many of the details.
Behind this shortwave, there continues to be the potential for
arctic air to nose into the region heading into the weekend. Decided
to stick with the blend at this time, suggesting temperatures on
Friday night and Saturday in the single digits to lower teens.
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
High clouds will continue to stream in from the southwest and
lower through the evening. Upper level energy crossing the lower
Great Lakes region this evening will continue to spark snow
shower activity later this evening and overnight. This will
primarily affect KDAY when the snow reduces vsbys and cigs to
MVFR category. Otherwise, other TAF sites will see MVFR cigs on
the higher end (above 2kft). Sky cover will remain MVFR through
at least daybreak and then mix out and lift in the morning to
OUTLOOK...MVFR/IFR ceilings and visibilities possible Monday
night into Tuesday. MVFR ceilings may persist into Tuesday
night. MVFR/IFR ceilings and visibilities possible Wednesday and
Area Forecast Discussion
National Weather Service North Platte NE
550 PM CST Sat Feb 6 2021
Issued at 516 PM CST Sat Feb 6 2021
Expanded the winter weather advisory west to include Lincoln
county and the southern Sandhills. Hi-Res model guidance indicates
a very efficient snow sounding late this evening at North Platte
with a NAM cross section indicating deep/strong lift around that
same time as well. Likely supportive of 1" per hour snowfall rates
for a few hours late this evening.
.SHORT TERM...(This evening through Sunday night)
Issued at 403 PM CST Sat Feb 6 2021
The main forecast challenges through the early week revolve around
more snow and even colder temperatures. A series of shortwaves will
bring at least two more rounds of accumulating snow, while subzero
temps across north central Neb present wind chill concerns.
Surface winds transition to south/southeast as the northern Plains
high drops into Iowa and a lee side low meanders over the Colorado
plains. Along with extra moisture advection, upslope flow will add a
boost in forcing for an incoming shortwave. Isentropic upglide
strengthens across all of western Neb with notable lift and moisture
shown from 275 to 290K. Expect precipitation to overspread the
forecast area steadily after 03z (perhaps earlier). Forecast
soundings and cross sections indicate very strong lift around 06z
with omega approaching -30ubar. In addition, a period of negative
EPV may lead to upright convection and quick snow rates around 1
in/hr. The most likely location for more banded structures exists in
the central Sandhills to north central Nebraska, where a new Winter
Weather Advisory was issued. Used a general blend for QPF as the
NAMnest is on the more aggressive end and later runs of the HRRR
suggest less moisture. Either way, SLR`s will be seasonably high
around 15-17:1 as nearly the entire cloud layer and sfc temps will
be near or below -10C. As such, the DGZ will be rather deep and will
encompass the strongest fgen and lift. Most of the snow accumulation
will occur 06-12z as the wave appears to be progressive and drier
air entrains into the area tomorrow afternoon. Overall, initial snow
forecast centers around 3-4" in the advisory with locally higher
amounts around Custer Co. Have a wide swath of 1-3" stretching
southwest toward I-80. A couple considerations... Amounts may still
be underforecast in the central Sandhills should the fgen band
really tighten and rates increase. Another is a shift to the
southwest for higher amounts if the band materializes earlier than
forecast. The former would possibly lead to Winter Storm criteria
for a few spots, while the latter could necessitate an Advisory for
another tier or two of counties south/west, including I-80 corridor.
Temperature-wise, lowered min temps tonight slightly to where the 0F
isotherm almost lines up with the WW.Y. Surface winds will not be
overly strong, but occasional gusts to 20 mph will still result in
wind chill values around -20. Included wind chill wording in the
WW.Y. Also went with the cooler end of guidance for max temps
tomorrow as the snowpack and persistent clouds will limit diurnal
heating. Forecast ranges from single digits north central to around
30F far southwest where some peeks of sun are possible and snowpack
After tonight`s event, attention turns toward yet another wave
progged to cross the forecast area tomorrow night into early Monday
morning. At this time, dynamics don`t appear as strong and moisture
content more limited with dew points near or below 0F. Upslope will
be more enhanced in the panhandle, however, and H5-7 fgen more
broad. SLR`s should remain nearly the same as tonight`s event. Went
with a broadbrushed 1 to 1.5" for new snow accumulation. While an
extension of the WW.Y is up in the air (or perhaps a new issuance)
for this wave, wind chills will be a concern again.
.LONG TERM...(Monday through Saturday)
Issued at 403 PM CST Sat Feb 6 2021
Winter is here to stay next week with the large upper trough
dominating the northern Plains. The embedded closed low deepens,
especially with the GFS solutions, with H5 heights dipping to
around 495dm near the Boundary Waters of MN. Primarily northerly
flow at H85 will help push temps well into the -20s C, which when
combined with a fresh deep snowpack, should translate to highs in
the single digits or teens and lows around -10F late week. Another
wave (or two) rotate around the trough and bring more snow
chances Thursday and Friday. Details aren`t too clear regarding
amounts, but imagine they would be light given the depth of cold
air and squandering of moisture.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 548 PM CST Sat Feb 6 2021
Another round of snow and MVFR ceilings are expected tonight. A
few areas could see IFR but MVFR should dominate. Winds will
increase from the east-southeast around 10-15 kts. Conditions
should remain MVFR much of the day Sunday.
Winter Weather Advisory from 9 PM CST /8 PM MST/ this evening to
noon CST /11 AM MST/ Sunday for NEZ005-006-008>010-023>029-
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
1025 PM EST Sat Feb 6 2021
Downsloping SE flow has kept most of the region dry this evening
with most of the precip falling as virga. There has been
occasional light rain observed in the far S Valley with snow and
sleet at times in SW NC. Latest RAP soundings have further backed
off on the warm nose except for along the E TN mountains into
extreme SE TN and SW NC where some warming occurs around 850 mb
before 08Z, but due to all the virga, expect sleet and ice amounts
to be very light on the order of a trace to 0.04 inches. We are
essentially running out of time to see much mixed precip before
the colder air arrives. The mid/upper shortwave responsible for
bringing the colder air will cross the region from 06-10Z with an
associated cold front pushing across the region. As this occurs,
the region will get under a coupled upper jet structure between
the right entrance of a 130-140 kt 300 mb jet streak over the
central Appalachians and the left exit of a 120-130 kt 300 mb jet
streak over GA/SC. This will lead to strong Q vector convergence
and frontogenetic forcing as the shortwave/cold front crosses the
region, so expect any rain/mix to quickly change to snow in the
post frontal CAA, first on the Plateau through SW VA after 05Z,
then across the valley through the rest of the area from W to E.
Despite the dynamics, HREF guidance shows this band of moderate to
heavy snow moving through pretty rapidly. This fast movement
combined with the limited precip earlier this evening has led to
decreased snowfall accumulations forecasted across SW NC, the E TN
mountains, and the valley. However, HREF guidance points to the
band pivoting across the N Plateau through SW VA the longest, so
slightly increased snowfall forecast amounts up there overnight.
The current warnings and advisories remain unchanged for tonight.
00Z TAF DISCUSSION.
Low confidence TAF forecast from a messy winter storm affecting
our region tonight and Sunday morning. Flight conditions will
deteriorate this evening at CHA and TYS with rain spreading south
to north. This will lead to MVFR first developing at CHA around
01Z then at TYS in the 02-05Z timeframe. Downsloping winds will
keep TRI mainly dry and VFR until after 06Z. Periods of IFR or
lower will occur from late tonight into mid morning Sunday, and
TYS and TRI will begin to mix with snow after 10Z with a
changeover to all snow near or shortly after 12Z. Light
accumulations are possible with further reduced cigs and vis.
Conditions will improve at CHA after 13Z and by mid to late
morning at TYS and TRI as the precipitation ends, with VFR
eventually returning later in the afternoon.
/ISSUED 359 PM EST Sat Feb 6 2021/
SHORT TERM...(Tonight through Sunday)...
A very messy forecast so I will do my best to break it down in the
easiest way possible.
General Overview Section I: Winter Weather Advisory pushed back to
start at 03z instead of 00z for plateau, valley, and VA counties.
Start time remains the same for southwest NC and the warning for
the mountains remains the same as well. 00Z to 03Z, initial onset
of precip this evening across the southern/central TN Valley and
southwest NC could result in a few reports of mixed precip. Mostly
rain is expected though. Then, 03Z through 06Z, downsloping winds
keep most areas east of I-75 mostly dry, especially toward the
foothills of the eastern TN mountains. Believe the HRRR and RAP
are handling this pretty well and even the NAM to some degree.
Between 06Z and 09Z rain begins to transition back to some form of
frozen precip, mainly snow, at most locations as the warm nose
exits to the east. The best chance for accumulating snow across
valley locations appears to be from 09Z through 12Z. Then, snow
tapering off through 15Z.
Overview Section II: The most difficult part of the forecast is
determining strength and location of the warm nose. A quick glance
at a four panel display comparing 850mb temps between the HRRR, RAP,
NAM, and SREF reveals that the models are actually in fairly good
agreement on the timing and location of the warm nose. By location I
mean the location of the 0 deg C line, which lines up fairly well
with where the current winter weather advisory starts/stops. Models
generally show this 0 deg C line running across the I-40 and up
along the I-81 corridor. Again, there is some model variation but
this is a pretty close approximation. Honestly though, if the HRRR,
RAP, and Nam are correct, the warm nose won`t affect wintry
accumulations across valley locations too much because there is very
little precip during this time. Tend to lean more toward these Hi-
Res solutions as they typically handle the southeast flow across the
mountains and its downsloping effects much better than the courser
resolution models. As mentioned in section I, models generally agree
that between 06Z and 09Z is when the warm nose exits and profiles
are cold enough for mostly snow. So during this time is when we will
see the bulk of our snow accumulation. This coincides with some of
the higher QPF amounts as well. This occurs as the trough axis
swings in and lift is maximized as a strong vort max swings through
the base of the trough. Boiling it down to a smaller scale, there
are many timing and PTYPE differences depending on location within
our CWA so I will break that down in the next section.
PTYPE By Region:
Southern TN Valley/Cumberland Plateau (Knoxville southward to
A few reports of mixed precip are possible this evening as precip
begins. Precip should mostly be rain though as a warm nose begins to
nose into the area. A dry period may occur later tonight as
downsloping begins, especially closer to the foothills of the east TN
mountains. Then, light snow accumulations, mainly on grassy
surfaces, are expected between 09Z and 12Z. Trace amounts up to 0.5"
are possible in some locations. Up to 1" possible across the higher
Models are now hinting at the possibility of freezing rain. Precip
may start out as a mix of sleet/snow/rain, then turn to rain. Then
at some point between 03z and 09Z (during the warm nose) precip may
transition to freezing rain. This could occur where surface
temperatures fall and remain below freezing, most likely in valley
locations. However, some freezing rain is also possible in the high
terrain as well where snow dendrite production is poor. Light ice
accrual of up to a few hundredths of an inch is possible, which
could cause some travel issues. Then, light snow accumulations from
0.5 inches to 1.5 inches are possible between 09Z and 12Z when the
warm nose exits and a transition back to snow is expected.
Central TN Valley/Cumberland Plateau (along I-40 and I-81
A few reports of mixed precip may occur as precip begins this
evening. Precip should mostly be rain though as a warm nose begins
to push into the area. A dry period may occur later tonight as
downsloping begins, especially closer to the foothills of the east TN
mountains. Light snow accumulations, mainly on grassy surfaces, are
expected between 09Z and 12Z. Anywhere from 0.5" up to 1" of snow is
Northern Cumberland Plateau/Far northern TN Valley:
Models indicate that the northern Cumberland Plateau has a very good
chance to stay snow through the whole event. This would allow higher
snow accumulations to occur. Accumulations are likely between 06Z
and 12Z. Widespread amounts of 1" to 3" seems reasonable at this
time. The far northern TN Valley (Union, Grainger, Claiborne,
Hancock) may also stay snow through the duration but less confidence
than the northern plateau. Areas closer to the TN/KY state line have
the highest chances to stay all snow. 1" to 2" for these areas from
06Z to 12Z are expected.
Northeast TN/southwest VA:
The warm nose looks like it will extend up into TRI and portions of
southwest VA. Again though, there may be little to no precip
occurring during this time due to downsloping. Precip moves into
southwest VA between 06Z and 09Z in the form of snow with
accumulating snow ending by 12Z. 1" to 2" of snow is expected with
isolated amounts from 2" to 4" across the highest terrain.
Downsloping can still be seen along the foothills, from Greene
County up through TRI area, as late as 09Z. If the Hi-Res models are
correct precip doesn`t move into these areas until between 09Z and
12Z. This would leave the window for accumulating snow to be quite
narrow. These locations will be very tricky to forecast amounts for
because of this. Anywhere from 0.5" to 1" seems reasonable at the
current time with isolated amounts up to 2" possible across the
East TN Mountains:
Snow amounts for the mountains are tricky as well. I`m not sure how
much if any snow accumulation occurs prior to the downsloping winds
developing. It appears that most of the precip early this evening
will be on the other side of the mountains, Carolina side. While the
downsloping winds are occurring we may see little precip. Prior to
the onset of snow, light freezing rain is possible as snow dendrite
production will be poor. A few hundredths of an inch of ice are
possible. Once the warm nose exits, snow will begin to fall between
09Z and 15Z as southeast flow ends and northwest flow takes over. 2"
to 4" are possible across the higher elevations with locally higher
Precip quickly exits tomorrow morning with the trough exiting.
Clouds will linger though, especially across the eastern
mountains. Some sunshine is possible by late afternoon across
some valley locations. Max temps tomorrow will be in the low to
LONG TERM...(Sunday Night through Saturday)...
A cold start to the week on Monday behind departing system Sunday.
Lows may be influenced by snow cover northern areas and higher
elevations. Lows in the 20s with a few locations in the teens.
A warming trend will commence Monday as flow becomes zonal and winds
become light as high pressure builds in from the west. A weak front
just to the north will keep colder airmass to the north. The
forecast area will under high pressure which will shift quickly to
the east coast and a southerly flow across the Tennessee Valley and
southern Appalachians. Highs should be near to above normal in the
lower to mid 50s. The weak front will move through Monday night and
Tuesday with mostly light rain but could start with a little snow
early on Tuesday before changing to rain. Only very light amounts of
Wednesday the front will be over the southern states with a possible
surface low over AL. Shortwave energy will track from west to east
as upper level trough digs south over the Rockies. Upper flow
becomes more southwest Wednesday. There will be a good chance of
mostly rain due to warmer temperatures Wednesday night through
Thursday with shortwave energy passing through. Highs Tuesday and
Wednesday should reach the 50s then cool a few degrees Thursday.
Surface low moves up from the Gulf Coast along the front toward the
Carolinas Friday. At the same time a large upper low will be
spinning over the northern plains into the western Great Lakes which
will bring some very cold air south and southeast into the Tennessee
Valley by Thursday night, and Friday into Saturday. This will bring
much colder temperatures into the region early Friday into Saturday
behind the system with lingering snow showers/or flurries across
northeast parts of the area. Some accumulating snowfall possible
late Thursday night and Friday across the northern Cumberland
Plateau, southwest Virginia and the higher elevations of the eastern
Tennessee mountains. High temperatures Friday expected to be only in
the 40s with 30s on Saturday. Lows Friday drop to the upper 20s and
teens and 20s Saturday morning. Confidence with the timing of the
cold temperatures is not real high as models have been delaying the
progression of the colder airmass the past several days. The
heaviest precipitation this week will be late Wednesday night into
Thursday night with 1.5 to about 2 inches possible Wednesday night
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 36 48 29 56 42 / 80 20 0 0 10
Knoxville McGhee Tyson Airport, TN 33 43 26 51 36 / 90 50 0 0 10
Oak Ridge, TN 33 43 26 52 37 / 90 40 0 0 10
Tri Cities Airport, TN 31 41 22 50 32 / 80 60 0 0 10
NC...Winter Weather Advisory until 10 AM EST Sunday for Cherokee-Clay.
TN...Winter Weather Advisory until 10 AM EST Sunday for Anderson-
Winter Storm Warning until noon EST Sunday for Blount Smoky
Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky
Mountains-Southeast Carter-Southeast Greene-Southeast
VA...Winter Weather Advisory until 10 AM EST Sunday for Lee-Russell-
Area Forecast Discussion
National Weather Service Nashville TN
850 PM CST Sat Feb 6 2021
FOR EVENING DISCUSSION.
Radar imagery this evening shows light rain has spread across the
southwestern half of the forecast area, with reports of flurries
in the higher elevations on the leading edge of the precip.
Temperatures remain in the in the upper 30s to mid 40s west of
the Plateau, with surface wet bulb temperatures in the mid to
upper 30s, so most of this precip should stay as rain the next few
hours before mixing with and changing over to snow towards/after
midnight. Models such as the HRRR appear to be too aggressive with
the changeover to snow occurring sooner in our southern counties
based on current obs and trends, but will be something to keep an
eye on. On the Plateau where temperatures are already in the mid
to upper 30s and surface wet bulb temps are near freezing, precip
will likely begin as snow this evening and remain such through
the event. Have updated temperatures, dewpoints, and other grids
to match latest obs and short term guidance.
Back edge of the precipitation shield is already near Memphis and
moving quickly eastward. Because of the relatively short duration
of the precip tonight, not confident enough in the more aggressive
model solutions to change inherited snow totals much - and 1 to 3
inches still appears most reasonable for the advisory area, which
is near the 50th percentile of all model guidance. Highest snow
totals still appear most likely in the typically favored Monterey
to Jamestown corridor. I did bump up snow amounts slightly in our
northwest counties where temps will cool down more quickly, as
well as in Coffee County where up to 1 inch is possible. Also
added Coffee County to the Winter Weather Advisory accordingly.
All products and grids have been updated and sent out.
00Z TAF DISCUSSION.
Tafs will start VFR, but cigs/vsbys will drop quickly starting
around 03Z as light rain develops. The rain will change over to
light snow with cigs dropping to IFR/LIFR all sites by 07Z.
Light snow will taper off 09Z-12Z with all sites improving to
MVFR. Winds will start light and variable, mainly NE, then winds
will become north around 10KT overnight after passage of a cold
Winter Weather Advisory until 6 AM CST Sunday for Cannon-Clay-
Area Forecast Discussion
National Weather Service Paducah KY
652 PM CST Sat Feb 6 2021
Issued at 652 PM CST Sat Feb 6 2021
ARW, NAM and GFS performed better than the NBM average and HRRR up
to this point. Forecast adjusted accordingly toward those better
performing models. This should result in lower snow totals over
southern IL into southwest IN, with a band of up to 1 inch
possible near the Ohio River in more of a deformation region,
associated with the upper air system moving east across AR. All
the activity should taper off after midnight. Generally looking at
up to 1 inch of snow possible depending on location, and of course
the affects of marginal air and pavement temperatures. With it
being dark now for a bit, chances for some added accumulation
start to increase. Echo trends over east MO into southern IL on
the down trend. Still cold for Sunday morning.
.SHORT TERM...(Rest of today and tonight)
Issued at 225 PM CST Sat Feb 6 2021
The short-term/high res models continued to show a mid level
shortwave moving through the PAH forecast area this afternoon and
tonight. Radar echoes were showing up this afternoon near the
AR/TN state lines, but measurable pcpn was not yet occurring.
Surface dewpoint depressions continue to be fairly substantial
across the region, and representative of the dry air below 700 mb
currently. Low level moisture fetch will increase this afternoon
ahead of the mid level feature, which was currently entering
northern AR at this time. Lift through the column is expected to
increase over the next few hours, enabling ice nucleation to
occur and lower levels to moisten up.
Latest WPC QPF has backed off some, which appears to agree with many
current model solutions, especially in the northern half of the
region, and the onset of pcpn from the west has been slightly
delayed in the forecast to take into account the initially dry
lower layers. By around sunset though, the best guess is that
measurable pcpn will be occurring over at least the western half
of our region, followed quickly by the eastern half in the evening
Model thermal profiles indicate rain over most of the region
throughout the daylight hours, with some flakes in the air
generally north of IL Route 13 and in northernmost parts of
southeastern MO, where more cold air will be present (highs mid
30s at the surface). After nightfall, much colder air will be on
its way into our region from the northwest, resulting in a rapid
changeover to snow, which will be likely everywhere at some point
during the evening hours. This event will be of rather short
duration, and pcpn is expected to end before daybreak, even in the
southern Pennyrile region of KY. Brisk northerly winds overnight
are expected to drive wind chill readings down into the single
digits north/teens south by daybreak.
Forecast storm total snow amounts are now mostly 1-1/2 inches
across most of southern IL, with pockets of as much as 2 inches
possible in Perry County MO and adjacent parts of southwestern IL.
Elsewhere, less than an inch of snow is forecast. The vast
majority of this should occur in the evening hours (except for the
southern Pennyrile region of KY). At this time, it is believed
that road surfaces will be warm enough through the evening to
limit the impact of the snow to travel, although flash-freezing of
residual moisture on the roads is possible especially in southern
IL, southwestern IN, and adjacent parts of southeastern MO as the
cold air surges in after midnight. At this time, we will continue
the Special Weather Statement in lieu of a Winter Weather
Advisory, which fits the current collaborative picture well. A WSW
headline cannot be ruled out in the evening, however, for a burst
of heavier accumulating snow that could occur.
.LONG TERM...(Sunday through Saturday)
Issued at 225 PM CST Sat Feb 6 2021
Sunday appears to be a transition day as high pressure spills into
the area. As this occurs, much colder air will filter into the
region with Sunday`s highs some 10 to 15 degrees colder than today,
ranging from the lower 20s far northwest to mid 30s far southeast
across the CWA. In fact, with the strong northerly winds in place at
the start of the day, it will be a rather frigid morning for many
locations. Wind chills will be down into the single digits across a
good chunk of the area with readings around zero in the
far northwestern sections of the area.
During the day on Monday and into Monday night, an inverted surface
trough will develop across the area associated with low pressure in
Texas. Meanwhile, a very large expansive area of low pressure aloft
will be hovering over a good part of Canada, centered over Ontario.
Monday into Tuesday, an upper level trough associated with this
upper low will move across the central Plains into the Midwest.
While most of the substantial energy will pass by to our north, we
will have a small chance of precipitation developing as the
aforementioned surface trough slides southeast Monday night. Sure
does not look like much right now though even though we may see a
wintry mix if is does materialize. In addition, after a big drop in
temperatures on Sunday, we will see a pretty big jump the other way
on Monday, with highs rising into the 40s almost everywhere as that
inverted trough develops, with the warmest readings over the
southern Pennyrile region of west KY.
On Tuesday, the cold air starts infiltrating the area once again.
However, the Tuesday night through Thursday night time frame is
riddled with precipitation chances. Active zonal flow aloft
eventually become southwesterly with time, as an upper level trough
moves across the four corners region and into the southern Plains
states. This synoptic scenario will also cut down on exactly how
cold we get during this time frame, especially in across western KY.
While there will likely be enough warm air initially on Tuesday
night to see some rain across parts of west KY both Tuesday and
Wednesday afternoons (with frozen precip elsewhere), but as colder
air moves later Wednesday night and Thursday, the precipitation type
will be snow. Way to far out in time to get too exact with the when
and where and how much, but something we will need to keep an eye on
over the next few days, especially since the forecast has been flip
flopping many times over the past several shifts. Right now, the
highest PoPs will be on Wednesday night into Thursday as many of the
GEFS and ECMWF ensemble members support this.
What seems to be consistent is the cold air arriving by the end of
the week and into the weekend. In fact, looking at the GEFS
percentages of highs lower than 20 degrees is pretty high across our
northern half Friday and into the weekend. The Euro ensemble means
are warmer though and so is the Canadian. This will be something to
keep an eye on as the latest NAEFS temperature anomalies and
probabilities of extremes are definitely showing a signal of much
colder weather. The latest numbers we expect will be highs only
in the teens and 20s Friday through the weekend. Wind chills will
drop down below zero across parts of southeast MO and southern IL
Friday morning and across much of the area on Saturday morning.
Issued at 511 PM CST Sat Feb 6 2021
Conditions will continue to deteriorate this evening, with MVFR to
local IFR conditions anticipated as precipitation moving across
the region transitions relatively quickly from light rains to
snow. The way the bands are setting up, conditions may be most
inclement from southeast Missouri into far west Kentucky, where
some banding of heavier snows may occur and reduce visibilities
even more. After 06 UTC, the precipitation will end quickly, with
MVFR cigs improving into Sunday morning. North to northeast winds
6 to 12 kts will persist.
AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
910 PM EST Sat Feb 6 2021
Low pressure developing over the northeast Gulf of Mexico will move
northeast along the Southeast and Mid Atlantic coasts tonight and
Sunday. High pressure will build in from the northwest and north
Sunday evening through Monday, before it moves into New England
Monday night. A warm front to our south will then move northward
into the Carolinas then stall out, holding over the region through
.NEAR TERM /THROUGH TONIGHT/...
As of 910 PM Saturday...
...Winter weather advisory for Forsyth county continues for
Primary forecast adjustments this evening are to cut back on the
dusting of snow accum over the E and S Piedmont and nudge them up
slightly over W Forsyth (but still around 1 inch). The precip shield
is overspreading the area on schedule, with the initially high
dewpoint depressions dropping quickly with onset. Precip has changed
over to all snow over the higher terrain of NE GA and W SC and W NC,
where surface wet bulbs are roughly 35F and lower, with a dewpoint
depression under about 4F. The low levels over central NC are
moistening quickly across our S and W, but overall the wet bulbs are
38F+ over all but the far NW, with little opportunity to cool these
down much (with no good cold air source), even as precip rates
increase over the next few hours. This fits with latest model trends
which keep the near-ground air too warm over much of the Triangle
area for anything other than rain. As such, have trimmed away at the
already-sparse forecast snow accum across the E and S Piedmont.
Forsyth county should face similar challenges of limited cool air to
support much accumulation, but based on what we`re seeing upstream
with quick one half to one inch totals and our precip rates yet to
really ramp up, will keep accumulation forecasts in Forsyth around
an inch, slightly higher in the far NW part. Still expect lows from
32 NW to low 40s SE. -GIH
Earlier discussion from 300 PM: Latest trends and guidance support
ongoing forecast. Max amounts are likely to be no better than a wet
coating over all but the extreme NW, where a longer duration of
mostly snow should generate amounts closer to an inch.
The latest surface analysis shows the Arctic cold front still off to
our NW across the Ohio Valley, where it will hold through tonight.
As expected, the surface low in the NE Gulf along the warm front
continues to deepen, with secondary cyclogenesis already underway
off the NE FL coast. The surface high centered just off the NE NC
coast will shift further offshore this evening, and this combined
with the secondary low strengthening and pushing NE near the GA/SC
coast will quickly increase the low level moisture flux into central
NC. What are now quite dry low levels (evidenced by WV imagery, RAP
proximity soundings, and current 25-40 F surface dewpoint
depressions) should quickly moisten late this afternoon / early
evening from S/W to N/E with lowering cloud bases as the SE 925-850
mb flow ramps up, leading to increasing/deepening moist upglide, all
in tandem with increasing upper divergence in the RRQ of the jet
streak to our N. Will stay with increasing pops to categorical by
late evening, with both moisture and forcing for ascent peaking in
the early overnight hours before starting to trend down from the SW
toward daybreak. The column appears to be plenty cold and wet enough
aloft for ice in the cloud from late evening through the night, but
outside of the N and W Piedmont, surface temps will likely be too
warm for any appreciable snow accumulation, and this area will also
become increasingly influenced by the encroaching warm nose aloft.
The exception to this will be in the Triad which should see as much
as a couple of hours of mostly snow, and this is supported by recent
HRRR runs depicting a batch of enhanced simulated reflectivities
crossing the Triad in the 05z-07z time frame, suggesting the
potential for this focused lift to sufficiently cool the column to
flip the ptype to mostly snow. This mechanism may generate isolated
snow islands elsewhere over the Piedmont or far N Coastal Plain
overnight, however both the predictability of this and the
confidence in this occurring outside of the Triad is not high. The
official forecast will show a storm total snow nearing 1 inch in and
NW of INT with amounts generally a dusting to a half inch elsewhere
in the area NW of Hwy 64. Expect lows of 31-33 near and NW of I-85
and in the 35-42 range to the S and E. -GIH
.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
As of 400 PM Saturday...
The coastal low is expected to be just off the N Outer Banks of NC
by 12z Sun and moving NE, with the 850 mb cyclone center just to its
W and also poised to exit the area through the morning. Initial low
level winds from the NE will shift around to NW with the column
slowly drying, but we will see one last slug of forcing for ascent
as the mid level shortwave trough now shifting from OK into AR
crosses NC/VA Sun morning. While there could be a little wet snow
mixed in with this final batch of precip, we do start losing the ice
aloft in the -12C to -20C depth, plus surface temps will be warming
slowly, so most of this should be rain or a mix at most. Precip
should be ending from SW to NE as we get on the subsiding and drying
backside of the shortwave trough, although wraparound moisture may
keep low clouds and patchy drizzle over our N sections well into the
afternoon, so will be slow to clear things out. Highs in the low-mid
40 NE ranging to low 50s in the SW where there should be decent
sunshine for much of the afternoon. Expect clearing overall Sun
night, but the moist ground and the low level northeasterly flow as
chilly surface ridging starts to build in from the N may allow some
stratus to develop over our NE overnight. Lows from the mid 20s to
lower 30s. -GIH
.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 250 PM Saturday...
At the risk of sounding like a broken record from the last couple of
days, while parts of the extended forecast include higher
confidence, the majority of the forecast is a low confidence
All models point to high pressure building across the Mid-Atlantic
states on Monday, resulting in a dry day. By Tuesday morning, the
region will be pinched between two different systems, one moving
across the Ohio River Valley and a second moving along the Gulf
Coast. Have made little change to this part of the forecast, keeping
slight chance pops after midnight and chance pops for much of
Tuesday as the Ohio River Valley low`s cold front moves across the
state. As the cold front moves through, a slight chance of showers
will remain east of I-95 Tuesday evening, but the rest of Tuesday
night and all of Wednesday are expected to be dry.
By Wednesday night the next storm systems begin to move into the
region. By Thursday morning there should be one storm system over
the Gulf states, while a second surface low will be off the South
Carolina coast. However, both systems are expected to hold their own
and track to the northeast, so this is not a Miller B cyclogenesis
scenario. Confidence is high enough in widespread precipitation that
pops have been bumped up to likely on Thursday and Thursday evening.
While overnight lows Wednesday night will drop into the mid 30s, a
warm nose around 850 mb between 3 and 6 C (depending on the GFS or
ECMWF) should be warm enough to melt any snowflakes. The warm nose
should allow all precipitation to reach the surface as liquid, and
the above freezing surface temperatures should allow for rain
instead of a freezing rain threat.
Confidence in the forecast plummets Friday, because while both the
12Z ECMWF and GFS show the pair of lows well out of the region, the
GFS dries out conditions while the ECMWF brings another wave of low
pressure along a trailing cold front and has another low pressure
system sitting over the forecast area by Saturday morning. Have
stuck with the NBM forecast, which goes with slight chance pops
Friday night and is dry on Saturday.
Temperatures through the extended period do not appear to be too far
from climatology. The potential cold blast that has been advertised
for the last week continues to be pushed back, with long range
models not showing the arrival of colder air until at least the
second half of next weekend.
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 725 PM Saturday...
Initially VFR conditions will yield to a shield of precipitation and
lowering ceilings and visibility restrictions that will trend
through MVFR-IFR range over cntl NC during the next several hours,
as a coastal low strengthens and tracks up the Southeast coast.
After a brief period of rain at onset, that precipitation will be
primarily snow, possibly moderate to heavy for a several hours, at
INT/GSO. All or mostly rain is expected elsewhere. Snow will then
likely mix with or change to a cold rain even at INT/GSO by around
09Z Sun, with continued widespread LIFR-MVFR conditions and
lingering rain or drizzle otherwise and elsewhere through early Sun.
VFR conditions are generally expected to develop throughout cntl NC
by Sun afternoon, as the coastal low tracks up the middle Atlantic
coast. Low level wind shear may also briefly result at FAY between
05-10Z Sun and RWI between 07-14Z Sun.
Outlook: A band of wrap-around moisture behind the departing coastal
low may result in another episode of IFR conditions Sun night-Mon
morning. Another pair of frontal systems will result in a chance of
rain and IFR-MVFR conditions late Mon night-Tue and again late Wed-
Winter Weather Advisory until 10 AM EST Sunday for NCZ021.