Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/05/21

AREA FORECAST DISCUSSION

National Weather Service Kansas City/Pleasant Hill MO

 533 PM CST Thu Feb 4 2021

.Discussion...
Issued at 316 PM CST THU FEB 4 2021

Key Messages...

1. Light snow is expected on Saturday, Amounts will range from one
to two inches across the northern half of Missouri. Snow will begin
in the morning and taper off West to East through the afternoon and
evening. Expect a dusting to an inch across the KC Metro.

2. A brief burst of snow may sweep across northern Missouri on
Sunday, with a dusting to a half inch possible, but better chances
will exist early Monday through the day. As of now, upwards of one
to two inches is possible Monday across the northern half of
Missouri, including the KC Metro. Up to three inches is possible in
north central Missouri.

3. Dangerously cold conditions are still expected to develop over
the weekend and continue through all of next week. Highs are not
expected to climb above freezing for most places across central and
northern Missouri, with cold really taking hold on Sunday and
persisting through next Friday. Morning lows will dip into the
single digits Tuesday morning through the end of the week, with lows
in northern missouri below zero.

Detailed Discussion...

Quite a bit to discuss this afternoon. The narrow swath of moderate
to dense snow has weakened, but continues to push into eastern
Missouri through 2 PM CDT. Behind this activity, breezy and much
colder conditions have settled in, with temperatures holding steady
in the lower 30s to upper 20s in northern Missouri. Overnight, the
500mb trough will continue to dig, pivoting northeastward towards
the Great Lakes through early Friday. Short range guidance continues
to suggest a weak short wave traversing across western Missouri
around midnight. Forecast soundings suggest a near saturated
dendritic growth zone. Any dendrites that develop will struggle
through drier boundary layer conditions, but if development persists
and enough support is present, as the HRRR and NAMnest suggest, I
cannot rule out some flurries across the KC Metro for a few hours
tonight. Morning lows, Friday, will dip into the mid 20s, for areas
that saw upwards of 2 inches of snow today in northern MO, temps
will dip into the teens. Afternoon highs will climb into the 40s
south of the Missouri River with temps dropping off quickly to the
north, with locations in northern MO not reaching above freezing.

The weekend forecast remains, for lack of a better phrase, a mess.
With a large scale troughing centered over Hudson Bay, the Plains
and Midwest are left open to subsequent short waves dropping from
the northwest. On Saturday, a stout short wave digging southeast
will bring ample moisture and support for a quick hit of modest
snowfall and rain. Expect light to moderate snowfall to develop into
northwest and northeastern Kansas through the Morning. Precipitation
will continue to spread eastward with time, with afternoon temps
in the mid 30s along the Ozark Plateau resulting in rain and or a
rain snow mix across the Lakes region, for a few hours. Expect one
to two inches of snow across northern Missouri, with a dusting to
an inch along the Missouri River Valley and KC Metro.

Sunday, a shallower short wave will bring a quick burst of light
snow across northern Missouri. This will proceed a more prominent
short wave that will cross the area on Monday. Early projections
are for one to two inches along the Missouri River valley to two
to three inches in north central Missouri.

The big impact this coming week is the cold. It cannot be stressed
enough the impact of multiple below freezing temperature days. As
discussed in the key messages above, the region is looking at
multiple days in a row next week of single digit low temperatures,
along with negative single digits across northern Missouri. Over the
next seven days, there`s no break in bitter cold temperatures on the
horizon.

&&

.Aviation...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 529 PM CST THU FEB 4 2021

VFR conditions will prevail for the rest of the TAF period with
cloud ceilings hanging around 10,000ft and 25,000ft overnight
through tomorrow. Notable mentions for our terminals include the
transition in winds overnight and into Friday morning. Winds are
expected to remain near 10kts, as winds switch from the NW this
evening, coming from the SW tomorrow morning, and gradually
switching back to a NW component by tomorrow afternoon.


&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&

$$

Discussion...Kurtz
Aviation...Klaus



AREA FORECAST DISCUSSION...UPDATED

National Weather Service Sioux Falls SD

 531 PM CST Thu Feb 4 2021

.SHORT TERM...(This Evening through Friday)
Issued at 318 PM CST Thu Feb 4 2021

Have been seeing occasional northwest-southeast oriented cloud
streets on satellite, most apparent on GOES-16 Day Snow-Fog RGB.
Scattered reports of associated light snow/flurries as well, mainly
near/east of US Highway 81. This activity likely in response to
steep lapse rates within the lowest 0.5km per RAP soundings, which
is also aiding in persistence of occasional gusts of 35-40 mph this
mid-afternoon. Soundings project this layer should stabilize over
the next 2-3 hours, which should allow the residual thin cloud
cover, spotty snow showers, and stronger wind gusts to subside.

The rest of the night may still be on the breezy side, especially in
our higher elevations from east central SD to southwest MN, with a
focus on the much cooler temperatures. The modest breezes should
help temperatures from fully bottoming out, but did shave a few
degrees from previous forecast in areas where we received the higher
snowfall amounts earlier today.

Friday should be on the quiet side, though remaining breezy with
northwest wind gusts of 20-30mph again developing. Models indicate
some increase in at least mid-level clouds associated with a weak
wave sliding through the Missouri River Valley, but for now, looks
like best chances of any light snow accumulations will be across our
far southwest, in south central South Dakota. Similar to tonight,
shaved a degree or two from previous forecast highs in our central
to northeast areas.

.LONG TERM...(Friday Night through Thursday)
Issued at 318 PM CST Thu Feb 4 2021

Cold with quick shots of mainly light snow are the highlights for
this first weekend of February. Pattern becomes rather stagnant,
with upper low spinning over Ontario/James Bay, while multiple waves
rotate through the base of the trough across the northern Plains and
Upper Midwest. Some model disagreement on precise location of the
lower level thermal boundary, though modest consensus that 850mb
front will be well southwest across southwest Nebraska, with mid
level boundary closer to the SD/NE border and Missouri River Valley.
This will be a focus for a couple of quick-moving light snow chances
through the weekend as the aforementioned multiple waves move along
the mid level boundary. Best chances remain south of I-90, perhaps a
bit better even south of the state line, per latest GEFS and ECMWF
ensembles. At this time, neither event looks to approach advisory
levels on their own, but could be a quick inch or two in some areas
with each shot, first focused during the morning hours Saturday, and
the second nearly 24 hours later on Sunday morning.

Otherwise focus will be on the coldest air of the season settling
into the region. Looks like several sub-zero nights ahead, with a
few locations possibly not warming back up above zero Sunday and/or
Monday. Could be marginal in our northeast for wind chills reaching
advisory criteria of -25F Friday night/early Saturday, with
chances looking better for Saturday night/early Sunday, and again
Sunday night/early Monday, at least for areas north and east of
Sioux Falls.

No relief from the cold in sight through next week, as the upper low
continues to spin over Ontario/eastern Canada, allowing reinforcing
pushes of cold air to spill into the north central US. Cannot rule
out additional chances for light snow in this pattern, but at this
time, enough variance in the model timing of a continued stream of
weak waves that difficult to pinpoint which period may have better
chances.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 527 PM CST Thu Feb 4 2021

VFR conditions will prevail overall through the period. Some
sites across southwest MN and northwest IA may see lofted blowing
snow in the 1-3kft range, tapering off early this evening. May see
occasional gusts up to 20 kts overnight, but overall expect
northwest winds to weaken to 10-15 kts. Gust up to 25 kts will
redevelop Friday morning, persisting through the daylight hours.
Expect mid level ceilings to spread in early Friday as well.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&

$$

SHORT TERM...JH
LONG TERM...JH
AVIATION...BP



Area Forecast Discussion

National Weather Service Lincoln IL

 757 PM CST Thu Feb 4 2021

.SYNOPSIS...
Issued at 757 PM CST Thu Feb 4 2021

Windy conditions are on tap overnight, in the wake of a strong
cold front. This will result in areas of blowing and drifting snow
overnight, primarily near and north of I-74, where there was a
little more snow accumulation from earlier on Thursday. Lingering
light snow should move out by late evening, though a weak
disturbance may bring a few sprinkles or flurries south of I-72 on
Friday. While Friday will be much colder in many areas, the
weekend will see the brunt of a cold air pattern arrive,
persisting through much of next week.

&&

.UPDATE...
Issued at 757 PM CST Thu Feb 4 2021

Wind Advisory has been issued for areas east of US-51 the
remainder of the evening. Have seen winds gusting over 50 mph at
Decatur and Champaign the last couple hours, and close to 50 near
Bloomington. RAP 3-hour pressure changes of 4-6 mb in the wake of
the cold front are contributing to the high winds, and the evening
sounding from our office as well as the radar VAD wind profile are
sampling 40+ knot winds a couple thousand feet off the surface.
Core of the stronger pressure change will shift east into the
Tennessee Valley over the next few hours, and will allow the winds
to drop off a bit, so the advisory only runs until midnight.

Aside from a lingering band of snow that currently extends from
near Lacon to Champaign, much of the snow has exited the forecast
area this evening. Surface visibilities are indicating a fair
amount of blowing snow back past the Iowa border, and traffic maps
show widespread slowdowns north of a Macomb to Bloomington line, a
combination of the blowing snow, earlier snow, and some freezing
of wet pavement from earlier. Will continue with the Winter
Weather Advisory in this area, emphasizing more of the blowing
snow aspect.

&&

.SHORT TERM...(This evening through Friday)
ISSUED AT 332 PM CST Thu Feb 4 2021

A strong weather system continues to bring rain or snow to central
Illinois this afternoon. As of 230pm, the cold front had cleared
Macomb and Galesburg and was knocking on the door of Peoria. Temps
drop quickly behind the front, decreasing from 36 to 28 degF in
Macomb in just over an hour. Just ahead of the cold front, rain has
begun transitioning to snow, with mPING reports of snow as far east
as I-55 as of 3pm. An observer in Knoxville reported near white-out
conditions at 215pm. Galesburg was reporting 3/4 mile visibility
at 3pm. Further upstream, numerous surface stations in Iowa
reported 1/4 to 1/2 mile visibility and gusts of 40 mph winds as
the snow moved through earlier this afternoon. While total snow
amounts across the area are still expected to be less than two
inches, expanded the winter weather advisory further south and
east to highlight the potential for difficult travel during the
evening commute. Snow and gusty winds will combine to
significantly reduce visibility, creating near white-out
conditions at times.

Precip will end from east to west as the cold front progresses
across the area, with much of the forecast area dry by 00z. Strong,
gusty northwest winds will continue into the evening, with
widespread gusts to 40mph behind the cold front. Low temps overnight
will range from the low teens to low 20s, and given the gusty winds,
sub-zero wind chills are expected along the I-74 corridor, with
single digit wind chills further south.

Winds will remain fairly blustery on Friday. There will be a fairly
wide range in high temps across the area (low 20s north to upper 30s
south). Blowing snow will remain a concern through the morning for
any locations that receive accumulations this afternoon/evening. A
weak shortwave is expected to translate trough the larger scale
trough Friday afternoon and evening, bringing the potential for
flurries or light snow to locations mainly along and south of the I-
70 corridor. Little to no accumulation is expected. Air temps will
be cooler Friday night into Saturday, but weaker winds will result
in wind chill values similar to Thursday night.

.LONG TERM...(Friday night through Thursday)
ISSUED AT 332 PM CST Thu Feb 4 2021

An arctic air mass will arrive in central IL Saturday, with an upper
level disturbance providing a period of snow arriving Saturday
afternoon from around Taylorville to Champaign northwestward, and
Saturday evening to the southeast. While snowfall amounts continue
to have some uncertainty, an inch or two looks to be the general
range by Saturday night. Behind this feature, the coldest portion of
the airmass arrives, with lows expected to reach single digits or
possibly below zero north of I-70, and wind chill values -10 to -20
in this area. Highs on Sunday appear to be exhibiting better
predictability with ensemble model clustering better than the
previous few days. Forecast highs range from 6 in Galesburg to 26 in
Lawrenceville as a result, still well below normal, but fortunately
not as cold as some of the potential scenarios from a few days ago.
Nevertheless, longer range models showing a decent agreement for a
prolonged period of significant cold weather with a continued flow
of arctic air into the region. Forecast features a brief, marginal,
respite from severe cold on Monday as highs range from 11 at
Galesburg to 34 at Lawrenceville, then plummet back to teens most
areas Tuesday through Thursday.

Occasional disturbances embedded within a broad upper trough
stationed over the area in the extended period are likely to keep
bringing occasional light snowfall to central and southeast
Illinois. While timing and impacts are subject to considerable
uncertainty at this point, it appears Sunday into Monday should have
a decent chance of snow beginning in northern IL and spreading into
southern IL by Monday. Beyond that, specific timing and impacts
highly uncertain.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 514 PM CST Thu Feb 4 2021

Strong cold front is expected to pass through KCMI before 00Z,
transitioning the rain over to snow. Back edge of the
precipitation is moving through west central Illinois this hour,
and should exit the TAF sites by about 02Z. Some potential for
blowing snow to reduce visibility at KPIA this evening as west
winds gust close to 40 knots at times, but snow accumulation in
other areas has been more minimal. While winds subside a bit later
this evening, gusts 20-30 knots are likely to linger well into
Friday.

Satellite imagery shows the back edge of the clouds in central
Missouri, and MVFR ceilings in central Illinois are likely to
linger until about 06-09Z in most areas until some of this
clearing arrives. Skies are not expected to fully clear in our
area though, and there is some potential for brief MVFR periods
during the day on Friday.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM CST Friday for ILZ027>031-
036>038.

Wind Advisory until midnight CST tonight for ILZ043>046-053>057-
061>063.

&&

$$

UPDATE...Geelhart
SYNOPSIS...Geelhart
SHORT TERM...37/Erwin
LONG TERM...37
AVIATION...Geelhart



Area Forecast Discussion

National Weather Service Louisville KY

 923 PM EST Thu Feb 4 2021

.Forecast Update...
Issued at 921 PM EST Thu Feb 4 2021

Regional observations show the wind shift associated with frontal
boundary extending NNE-SSW between HNB and SDF while current radar
shows widespread rain across most of the CWA with back edge of the
rain just past HNB. Wind gusts will increase within the dry air
behind the front with upstream observations reporting gusts in the
30-35 mph range. Gusty winds will continue for several hours, slowly
subsiding into the pre-dawn hours. Colder air lags behind the
actual wind shift, but we`re still expecting temperatures to drop
into the mid 20s by early Friday morning. Have updated wind grids
for the next several hours as well as refreshed near-term grids.
Otherwise, the going forecast remains on track. Updated products
forthcoming.

&&

.Short Term...(This evening through Friday)
Issued at 310 PM EST Thu Feb 4 2021

Latest sfc analysis shows the primary sfc low located over Ontario,
with a secondary sfc low tracking NE out of MO and into IL. To our
east, sfc high pressure and upper level ridging are located over
Niagara Falls. KLVX has shown light radar returns across the region,
but based on Kentucky Mesonet and ASOS obs, precip has been making
it to the ground for areas along and west of the I-65 corridor so
far. To the east, mostly virga has occurred due to a deep dry layer
in the low levels. We have received a few reports of very light
sleet or a rain/sleet mix this afternoon, which suggests partial wet
bulb cooling taking place as the column cools. We have even seen a
very light sleet here at WFO LMK.

As time goes on and the front approaches, widespread rain will take
over across the entire region. Widespread rain will be across the
CWA by 00z this evening. Precip will exit from west to east,
beginning in our western CWA by 03z. The precip shield should be
east of the I-65 corridor by 04-05z tonight, and completely out of
the eastern portion of the CWA by 06z or so. Total precip for this
event still looks to be between 0.25-0.50 inches, with the higher
QPF expected for areas west of I-65.

While precip will quickly exit the region, cold air will rapidly
fill in behind the front. Cold air may catch up to the back edge of
the precip shield and create a very brief window for wintry weather
or mix. Best chance of seeing this possibility appears to be along
and north of the I-64 corridor. If cold air does catch up, could see
a very light accumulation, but not confident enough to include snow
amounts in the grids. One thing that is certain is the cold air
filtering in behind. Temps have risen to the mid 40s for most across
the region, and even upper 40s in south-central Kentucky. With deep
SSW flow advecting WAA in, could see a few spots hit 50 this
afternoon/evening. Behind the front, CAA rushes in and drops our
temps to lows into the 20s by tomorrow morning.

...Wind Gusts Continue this Afternoon and Evening...

With the high to our east and low to our west, a tightened sfc
pressure gradient is helping to increase SW sfc winds this
afternoon, and should continue this evening as a SSW low level jet
works into the region ahead of the actual frontal boundary. Kentucky
Mesonet peak wind gusts so far today are mostly in the 20-25 mph
range, with Simpson County as the outlier with a 34 mph peak gust.
Wind gusts will continue to increase this afternoon and evening.
Currently expect to see peak gusts of 30-35 mph between 22-03z as
the core of the low level jet passes overhead. It is not out of the
realm of possibilities to see an isolated 40 mph gusts down in our
southern CWA. The inversion that was in place earlier today has been
eroding. RAP model soundings continue to support the idea that it
should continue eroding and allow stronger winds to mix down.

For tomorrow, high pressure slides from west to east across our
south. Skies clear out starting around sunrise tomorrow and continue
to clear for most through the day. Highs will be in the upper 30s to
low 40s.

.Long Term...(Friday night through Thursday)
Issued at 320 PM EST Thu Feb 4 2021

The long-term continues to see poor consistency across models and
between model runs.

Friday night, a relatively weak cold front pushes south through the
Lower Ohio River Valley. The front has limited moisture to work
with, but multiple models are beginning to resolve a dusting of snow
most likely across southern Indiana and north central Kentucky.

Saturday night, the next round of Arctic air dives southeast behind
a cold front that slides east along the Ohio River. Most of the
moisture will remain in the warmer air, south of the front, but
limited moisture is expected behind the front in the cooler air
mass. There`s good agreement among guidance that the best moisture
will be held farther south in Tennessee, and the system will weaken
as it moves through central Kentucky. Precipitation in southern
Indiana will begin as snow, and with falling temperatures, a change
over towards snow will take place through central Kentucky.

Surface high pressure will advance over the region behind the cold
front, but skies are expected to have a hard time clearing. The best
shoot at seeing some sun will be on Sunday before clouds return
ahead of the next cold front.

Monday night`s cold front is expected to drop temperatures, but
limited moisture leaves a couple of questions about precipitation,
how much and when. Whatever precipitation does develop is expected
to fall as snow in the northern half of the CWA, while rain falls in
the southern half. Things could remain this way until enough cold
air pushes in to change everything over to all snow Tuesday night.
All this may not happen if the moisture isn`t there to materialize.

After Tuesday night, models really begin to diverge. There remains a
strong signal for a strong cold front to move through the region
Thursday night or so, but recent forecasts have been falling on
their face. This problem has been seen in temperatures as well.
Going out past a few days, ensembles have quite the spread. Sunday
and Monday morning still look to be cool, but the lower morning lows
have been pushed back to the end of the week. With time, the
current forecast lows could trend back towards climo.

&&

.Aviation...(00Z TAF Issuance)
Issued at 637 PM EST Thu Feb 4 2021

Expect MVFR/IFR flying conditions with gusty winds through the first
portion of this TAF cycle. Latest surface analysis places the
occluded frontal boundary NNE-SSW through southern IL and into
MO/AR. Regional observations have shown winds out of the S with
gusts into the upper teens to low 20kts. Winds will shift to WNW
behind the front with sustained speeds and gusts increasing. Gusts
are expected to increase up to 30-35kts for a few hours. Winds will
slowly subside by early Friday morning before picking up again mid
day out of the WSW with gusts in the 20-25kt range.

MVFR CIGs ahead of the front will drop to IFR just ahead of and
behind the front. VIS may also be reduced to IFR within moderate
rain. LEX could also see a brief changeover from light rain to light
snow early Friday morning. Clouds advect eastward leaving VFR
conditions for the remainder of Friday.


&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&

$$

Update...CG
Short Term...CJP
Long Term...KDW
Aviation...CG