Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/15/21

Area Forecast Discussion

National Weather Service La Crosse WI

 653 PM CDT Sun Mar 14 2021

.SHORT TERM...(This evening through Monday Night)
Issued at 252 PM CDT Sun Mar 14 2021

The 14.12z models are even a bit slower with the movement of the
snow into the area.  The meso models are showing that the
snow will move into northeast Iowa between 2 AM and 5 AM,
southeast Minnesota and southwest Wisconsin between 5 AM and 8 AM,
and west-central and central Wisconsin between 10 AM and 1 PM.
One new development in the RAP and HRRR is that this band is
weakening much faster and as a result the duration looks to be
shorter for the highest hourly snow rates, so there is concern
that the snow amounts might be trending lower. However, the
14.12z GFS did come in with higher snow amounts than it`s 14.06z
run.

Even though we are within 24 hours of the event, there continues
to be a decent spread in the model snowfall amounts. Much of this
has to due to with the precipitation amounts varying due to
uncertainty on how fast the forcing will weaken, uncertainty on
hourly rates, higher sun angle, compaction (from being a heavier,
wet snow), dry air advecting in from east, and a warmer ground.
The NBM 10th percentile has snow totals of up to 2 inches west of
the Mississippi River and up to 1" south of Interstate 94 in
western Wisconsin. Meanwhile, its 90th percentile is 4-7 inches
west of the Mississippi River (highest in northeast Iowa) and 2-5
inches south of I-94 in western Wisconsin. Due to the spread, will
trend the snow forecast toward the 25th to 75th percentile for
snow amounts.

The 14.12z HREF continues to show that the highest snow rates will
be across northeast Iowa shortly after sunrise Monday. There is over
an 80 percent probabilities of hourly snow rates between 7 AM and
9 AM but these probabilities decrease rapidly during the
remainder of the morning. Elsewhere, snow rates will be up to a
half inch per hour. However, there will be times that the hourly
snow rates could be in the half to three-quarters of an inch.

While the soundings continue to indicate that snow is the most
favored precipitation type with this band. However, as the forcing
weakens and we lose icing aloft, it still looks like the snow may
change to light rain/freezing rain. This will be highly dependent
upon on the surface temperatures and dew points. Due to the
higher sun angle and less ground frost, there is some uncertainty
in the day how much the icing from light freezing rain will occur
on the roads.

.LONG TERM...(Tuesday through Sunday)
Issued at 252 PM CDT Sun Mar 14 2021

Main forecast concerns from Tuesday into Sunday are precipitation
chances Wednesday into Thursday then temperatures Friday into
Sunday. The 14.12z GFS/ECMWF/GEM are in decent agreement in slowly
moving upper level closed low across the Central Plains States
Tuesday night into Thursday. Forecast area at this time will be on
the northern periphery of the upper level closed low. Southern half
of the forecast area will see the highest chances of precipitation.
As far as precipitation type...temperatures during the day will be
above freezing and be all rain...then at night temperatures will be
near or slightly below freezing and precipitation type will be all
snow. Upper level closed low weakens and tracks into the eastern
United States and upper level ridge amplifies over the central
United States. The upper level ridge will allow for warmer air to
advect into the region and 925mb temperatures are expected to warm
to plus 6 to plus 9 degrees celsius by 00z Monday. High temperatures
will rise into the 50s Friday through Sunday with the possibility of
temperatures in the 60s at some locations Sunday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 650 PM CDT Sun Mar 14 2021

VFR conditions through tonight will give way to MVFR/IFR on Monday
as low pressure brings a round of winter weather. Snow is
expected to begin at RST around 12-13Z, falling heaviest from late
morning through mid-afternoon, then likely transitioning to light
freezing drizzle late in the period. For LSE, snow should begin
around 16-18Z but will not fall as intense as RST. LSE could see
some drizzle mix in at times through the afternoon before a
transition to light freezing drizzle just after the current
period ends. Visibility at both sites will drop to IFR, perhaps
LIFR at times at RST. Ceilings will drop to low end MVFR, perhaps
IFR at RST.

Winds will generally remain out of the east through the period.
Gusts should briefly subside early this evening but will likely
return overnight 20 to 30 knots as a low level jet drifts
overhead. If gusts don`t materialize at the surface, expect a
period of LLWS overnight. Otherwise gusts around 20 to 25 knots
through the day Monday.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from 7 AM to 7 PM CDT Monday for WIZ032-
     033-041-053>055-061.

MN...Winter Weather Advisory from 4 AM to 4 PM CDT Monday for MNZ086-
     087-094-095.

     Winter Weather Advisory from 7 AM to 7 PM CDT Monday for MNZ079-
     088-096.

IA...Winter Weather Advisory from 4 AM to 4 PM CDT Monday for IAZ009-
     010-019-029-030.

     Winter Storm Warning from 4 AM to 4 PM CDT Monday for IAZ008-018.

     Winter Weather Advisory from 7 AM to 7 PM CDT Monday for IAZ011.

&&

$$

SHORT TERM...Boyne
LONG TERM...DTJ
AVIATION...Kurz



AREA FORECAST DISCUSSION

National Weather Service Hastings NE

 657 PM CDT Sun Mar 14 2021

.DISCUSSION...(This evening through Sunday)
Issued at 424 PM CDT Sun Mar 14 2021

Biggest concerns include severe weather potential through mid
evening in our southern CWA as well as any ongoing minor flooding
issues from the consistent rain that we have had over weekend. Later
on into the night, attention turns to fog potential, especially
north.

Enhanced 50+ KT 925-850 mb are that were mixing down along with a
very tight surface pressure gradient this morning giving 50+ mph
wind gusts These enhanced elevated winds will continue to rotate
north of the cold core low to the west and we will experience a
noticeable decrease in wind speeds as the afternoon wears on. The
overall precipitation shield will shift north as well, with folks in
the far north being the last to see it go this evening. Perhaps a
dusting of snow in our far north.

Another focus for today will be areas of north central Kansas along
the surface occlusion to the east of the surface low located in
northwest Kansas. Hi-res models indicate the potential of some
surface based CAPE this afternoon (conditional with breaks of clouds
and sun allowing the surface to warm) with plenty of shear/deep
layer shear in this vicinity. With the nearly stationary occluded
front being a focus of increase storm relative helicity, and some
moisture pooling occurring just north of the boundary with dewpoints
perhaps getting to near 50 degrees this afternoon, all it would take
is a little sun to help get convection going. The chance of a weak
tornado is non-zero, so we will keep an eye out for this. Also, with
such low freezing levels, some hail approaching severe limits would
not be out of the question as well. Best chance for severe should
remain west southwest of the CWA, however, closer to the surface
low and closer to being underneath the cold core low aloft.

We turn to fog potential tonight. With large quantities of rainfall
recently and positive moisture flux within the east component to the
wind tonight, the chance for reduced visibility is increasing. I
have beefed up wording/grids significantly, and the HRRR surely
backs this up.

The upper level low will continue to give us additional rain chances
and keep us on the cool side until we can finally get it out of here
by mid-week, but unfortunately another trough moving through the
southern/central Plains on Wednesday gives us yet another shot at
some precipitation and perhaps a shot at a dusting of snow. We
finally dry out by Thursday afternoon and beyond as upper level
ridging works in and gives us a break with dry conditions and
warmer weather.



&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Tuesday)
Issued at 651 PM CDT Sun Mar 14 2021

We are expecting pretty poor aviation weather conditions the next
24 hours with the biggest problems being the low clouds and
possible fog. Confidence is not real great on the fog, but
confidence is high that we will see at least IFR or LIFR ceiling
conditions through most of the TAF valid period. Most of the rain
has ended, but we can`t rule out a few passing showers. The most
likely time frame for the fog will be from late evening through 3
or 4 hours after sunrise.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&

$$

DISCUSSION...Heinlein
AVIATION...Wesely



Area Forecast Discussion

National Weather Service Lincoln IL

 801 PM CDT Sun Mar 14 2021

.SYNOPSIS...
Issued at 307 PM CDT Sun Mar 14 2021

Scattered very light rain showers will continue across central
Illinois this evening, before a band of heavier rain arrives late
tonight into Monday morning. The atmosphere will become cold
enough to support a mix of freezing rain and sleet along and north
of I-74. However, little or no ice accumulation is expected.

&&

.UPDATE...
Issued at 802 PM CDT Sun Mar 14 2021

Impressive dew point gradient noted just south of I-74 early this
evening, with teens/20s north of it and 35-40 from I-72 south.
This has done a number on the northeast movement of the rain, with
our evening balloon sounding showing the dry layer about 8,000
feet thick. Upstream dew points across northern Indiana are as low
as 10-15 degrees, but as winds in our area develop more of an
easterly component late this evening, the precip should start to
make some decent eastward progress. Precip type should mainly
remain rain through the night, but a mix with some sleet and
perhaps freezing rain will be possible from I-74 north by sunrise.

Main concern for mixed precip will be in the 7-11 am time frame on
Monday, with NBM showing >90% chance of sleet along the I-74
corridor and accumulations potentially a half inch or more. Signal
on the forecast soundings continues to be favorable for some
freezing rain in this area as well, but 4 inch soil temperatures
are currently in the 40-45 degree range, so any accumulations
would likely be more on elevated surfaces and not last long with
temperatures rising into the mid 30s.


&&

.SHORT TERM...(This evening through Monday)
ISSUED AT 307 PM CDT Sun Mar 14 2021

19z/2pm water vapor imagery shows a deep upper low spinning over
eastern Colorado, with downstream short-wave ridging across the
Midwest. Despite the ridging, weak mid-level forcing has
triggered bands of very light rain showers across the KILX CWA
this afternoon. Latest radar trends suggest the bands will remain
south of I-74 and will eventually erode due to dry advection from
the northeast. HRRR and other CAMs indicate the initial band will
dissipate over the next couple of hours: however, a second band
will likely form across the same area later this evening. Any
precipitation that occurs this afternoon and evening will be quite
light, only amounting to a couple hundredths of an inch at best.

The stronger forcing associated with the Colorado low will slowly
pivot into the region overnight, resulting in a heavier band of
precip spreading into central Illinois from the southwest toward
dawn. Model timing has been very consistent...showing rain
increasing along/southwest of a Macomb to Taylorville line
between 06z/1am and 09z/4am...then spreading across the remainder
of the area shortly after daybreak. While most of central Illinois
will see rain, locations along/north of I-74 will cool sufficiently
to support a period of sleet and perhaps freezing rain late
tonight into Monday morning. While surface temps will drop into
the lower to middle 30s across this area, the ground is no longer
frozen, so any freezing rain that occurs will produce little in
the way of icing. May see a light accumulation of sleet across the
north before the precip band quickly lifts E/NE of the area
toward midday. Once the band departs, Monday afternoon will be
overcast and largely dry with high temperatures ranging from the
upper 30s north of I-74 to around 50 degrees south of I-70.

.LONG TERM...(Monday night through Sunday)
ISSUED AT 307 PM CDT Sun Mar 14 2021

As the Colorado low slowly tracks into Illinois, showers will
re-develop Monday evening. In fact, NAM/GFS MUCAPE values of
200-500J/kg suggest the potential for a few rumbles of thunder as
well. Have bumped PoPs to likely across much of the CWA and
mentioned a slight chance of thunder accordingly.

After the low exits, mild and dry weather will be on tap for Tuesday
before another storm system comes into the picture by the middle
of the week. Models tend to track this particular system just to
the south from the Southern Plains into the Ohio River Valley Wednesday
through Friday, keeping central Illinois on the cool side of
things. Have introduced PoPs as early as Wednesday morning, but
based on the highly amplified nature of the upper wave, think the
primary focus for rain will be Wednesday night into Thursday.
After that, dry weather will return for next weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 618 PM CDT Sun Mar 14 2021

Main issue in the short term will be with east winds increasing
this evening, as gusts approach 30 knots before 05Z and may be as
high as 35 knots between 09-14Z. A strong low level around 2,000
feet will help to amplify these gusts, and a mention of LLWS
continues. Steadier rain should begin moving in after 06Z, and
ceilings and visibilities will deteriorate overnight and past 12Z.
A rain/sleet mix will be possible near KPIA/KBMI between 12-16Z.
As the rain moves out around midday and winds diminish a bit,
ceilings are expected to lower to below 1,000 feet for the
afternoon.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Geelhart
SYNOPSIS...Barnes
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Geelhart



Area Forecast Discussion

National Weather Service Chicago/Romeoville, IL

 928 PM CDT Sun Mar 14 2021

.UPDATE...

928 PM...Evening update...No changes for tonight or Monday. Some
of the recent HRRR/RAP runs are changing the precipitation over to
snow faster on Monday and as a result have some higher snow
totals across the western and northwestern parts of the area.
Latest 00z NAM is coming in and generally in-line with our current
forecast. While some locally higher snowfall amounts are
possible, will hand off that potential to the incoming mid shift
with review of the entire 00z suite of guidance. Current two
segment SPS remains in effect until 08z and covers the current
expected amounts and impacts well. cms

&&

.SHORT TERM...
339 PM CDT

Through Monday night...

We may be in meteorological spring, but winter is not quite done
with us yet! We had been spared from any wintry precipitation so far
this month, but as is always the case in the month of March, we will
not escape this month snow-free due to a deep low pressure system
currently sitting over eastern Colorado. National radar mosaic
nicely depicts an expansive precipitation footprint associated
with this low stretching from the Rockies to the Appalachians with
a swath of rain also extending down southward to the Texas Coast
along a healthy moist conveyor belt. The northernmost flank of
precipitation sits draped across central Illinois this afternoon,
just south of our forecast area, which remains firmly rooted in a
very dry air mass. There is a chance that some of the light rain
farther downstate creeps into the far southern part of the CWA
later today, but with the dry air mass still in place, any of this
would likely remain as virga.

The upper low will pick up its pace later tonight as a longwave
trough digs towards the southwestern U.S. and nudges the low
northeastward. An east-southeasterly low-level jet currently
stretching from northern Missouri into eastern Nebraska will move
over our south overnight with roughly 50 kt flow progged at 925
mb (~2000 km AGL) between about 9 and 15Z. Guidance remains mixed
on the degree of boundary layer decoupling overnight and thus the
extent to which we may be able to tap into this jet. Think
guidance like the HRRR and the RAP may be a little too aggressive
with the mixing of ~50 mph gusts to the surface south of I-80
tomorrow morning, but nevertheless, it should still be a fairly
blustery morning with the tight surface pressure gradient across
the region.

As has been alluded to in previous discussions, the low will have a
lot of work to do to saturate the bone dry air mass that is
currently in place. While these saturation efforts are already
underway to some extent, they will be mostly futile for the time
being with a broad area of high pressure tracking southeastward
across Ontario providing a healthy replenishment of dry air into
the region to offset any moistening. As the low tracks closer,
the combination of moist advection, isentropic ascent, and dynamic
cooling induced by lift provided by favorable jet dynamics will
eventually achieve its goal of saturating the column sufficiently
for precipitation to start reaching the ground, but that likely
won`t happen until tomorrow morning for our southern and western
counties and possibly not until early tomorrow afternoon farther
northeast. It`s entirely possible, if not likely, that at least
part of the Chicago metro stays dry the entire morning, especially
as you head farther north.

The precipitation type forecast remains challenging and convoluted
even as we are within 24 hours of the event now, and our forecast
grids reflect that as they seem to resemble a child`s finger
painting with all of the various colors representing different
precipitation types and mixes splattered across the area. This is
primarily due to the combination of the presence of a 850-700 mb
warm (above freezing) nose, which will melt some amount of snow
aloft; sub-700 mb temperature profiles generally hugging the
freezing line, meaning that even a 1-2F degree difference
somewhere in the temperature profile could swing precipitation
type from one mode to another; and the continuing feed of dry air
that will keep wet-bulb temperature profiles mainly below freezing
in the lower levels, allowing for evaporative cooling to offset
much of the ongoing low-level warm air advection.

That being said, based on our current forecast, the general
precipitation type evolution looks to feature a wintry mix including
sleet and possibly freezing rain across the southern two-thirds
of the forecast area during the morning and early afternoon with
the main bout of precipitation likely ending as rain or a
rain/snow mix by late afternoon. Across our northern counties, we
look to have a more homogeneous precip type forecast of mainly
snow during the morning and early afternoon. Although, it is
likely that some other precip types will at least briefly mix in
somewhere here before most of the precipitation ends (a rain/snow
mix seems to be the favored solution, but a mix including sleet is
not entirely out of the question either).

Moderate to briefly heavy precipitation rates would be favored to
occur shortly after precipitation onset and will generally diminish
as the precip shield marches northeastward with time as the upper
low starts shearing out more and the associated sources of lift
weaken. The majority of any precipitation looks to end by the early
evening as a mid-level dry slot slides through the area, but some
patches of drizzle and/or snizzle could hang around into the
overnight hours. Additionally, as the occluded surface low tracks
across central Illinois, a wave tracking overhead should induce a
more concentrated area of rain showers across mainly the southern
half of the forecast area Monday night, although some of this
activity will likely sneak into the Chicago metro. Some of these
showers would be convectively-driven, and it`s not entirely out of
the realm of possibility that we get an isolated lightning strike
or two somewhere in the forecast area. All precipitation should
be out of the area by daybreak Tuesday.

The going precipitation accumulation forecasts of up to 0.5" of
sleet, up to 0.1" of ice accumulation generally south of I-80, and 1-
3" of very wet 5:1 to 8:1 SLR snow generally north of I-80 (highest
accumulations towards the Rockford metro and northwest Illinois
where better forcing with the right entrance region of an easterly
upper jet streak will be present) with 1" or less generally south
of I-80 seem adequate. However, with surface temperatures expected
to mainly be at or above freezing by the afternoon, any ice
accumulations from freezing rain would likely not last long, and
the wet snow may have difficulty accumulating on relatively warm
roadways, which should limit the overall impacts that we see with
this system. We opted to not issue any Winter Weather Advisories
for both this reason and because of the persisting uncertainty
with exact precipitation types and rates. Nevertheless, the potential
for slushy snow accumulations on colder roadways and the brief
potential for freezing rain to impact travel will be messaged via
SPSs and graphics.

Lastly, easterly winds gusting to around 35 mph out over Lake
Michigan will lead to the potential for minor lakeshore flooding
along the Illinois lakeshore. With the lake levels trending
downwards over the past few months and only a marginal wind and wave
forecast for lakeshore flooding potential, have opted to continue
holding off on any Lakeshore Flood Advisory issuance.

Ogorek

&&

.LONG TERM...
302 PM CDT

Tuesday through Sunday...

The main focus during the long term period will be the next
potential precipitation and wind maker for the area Wednesday
night and Thursday. Otherwise, relatively quiet weather is
anticipated.

Low-level cloud cover is likely to linger across much of the area
into Tuesday, but dry weather is expected. Seasonal high
temperatures are forecast for inland areas on Tuesday, with
readings generally in the 40s. Cooler conditions are expected
along the shores of Lake Michigan due to continued onshore flow.
Slightly warmer temperatures are forecast for Wednesday as we
await the approach of our next storm system taking shape over the
southern Plains. Similar to Tuesdays weather, the coolest
temperatures (lower 40s) will be near the lake, with inland areas
likely to climb to around 50.

Forecast guidance continues to merge towards a slower solution
with the Wednesday night and Thursday storm system. Basically this
means much of the daylight hours of Wednesday will likely end up
precipitation free across the area. Rain then looks to develop
northeastward over the area Wednesday night and continue on
Thursday as the center of the storm system tracks eastward across
the central Mississippi Valley towards the Ohio Valley.
Thermal profiles across the area from non-GFS guidance all
continue to favor all rain, but its possible some wet snowflakes
could mix in along the northwestern periphery of the precipitation
shield late Thursday.

Northeasterly winds are expected to become gusty with this system
on Thursday, and this does add some concern for the possibility
of lakeshore flooding. Overall, the surface gradient along the
northern periphery of the surface low should become favorable for
some stronger north-northeasterly winds down the lake due to the
presence of a fairly stout area of high pressure to the north over
western Ontario. Wind gusts of 35 to 40 mph are certainly
possible with such a setup, and the onshore component adds some
concern for large waves and an associated water level surge
occurring across the southern shores of the lake. For this reason,
we will to keep an eye on the possibility for at least minor
lakeshore flooding with this storm system.

Quiet weather returns to the area from Friday and into next
weekend as a large surface high shifts southeastward across the
Great Lakes. Temperatures in this pattern should moderate from
around 50 on Friday to potentially up around 60 by Sunday.
However, cooler temperatures are likely near the lake for Friday
and Saturday due to continued onshore flow.

KJB

&&

.AVIATION...
For the 00Z TAFs...

Forecast Concerns:
 * Messy wintry system Monday (SN,PL,FZRA,RA) and associated IFR
   conditions
 * Potential for LIFR/VLIFR vis under any heavier snow bands
 * Gusty ENE/E winds through the period

The Central Plains closed low will approach the area Monday
morning with precipitation expected to arrive at the terminals
mid to late morning. Latest guidance has trended a little bit
earlier with the onset of the heaviest precipitation and have
adjusted the timing of the TEMPO groups accordingly, but suspect
the previous concerns with the impact of dry air out ahead of the
precip shield remain a factor.

A wintry mix of precipitation is expected, ranging from mostly
snow and some sleet out toward RFD, and more of a mix of PL and SN
at the Chicago area terminals. Precipitation type and timing will
continue to be refined as we get closer to the event. If snow
becomes the more predominant precip type for a period, the steep
lapse rates would support visibility reductions potentially
nearing LIFR to even VLIFR. Have maintained IFR vis and cigs for
now due to lower confidence. As the primary band of precipitation
lifts to the northeast a mix of light rain/drizzle and a few
flurries will remain possible into the evening hours.

Winds remain gusty into this evening before easing slightly
tonight. Heading into early Monday morning, expect gusts to ramp
back up into the upper 20 kt range ahead of the approaching
system. A few higher gusts into the lower 30kt range are certainly
possible with a strong low-level jet overhead. Surface winds
remain elevated enough to preclude a formal low-level wind shear
(LLWS) mention. Gusts then remain elevated through the TAF period
but begin to ease with the passing of the band of precip.

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...IL nearshore waters until 4 AM Tuesday.

     Small Craft Advisory...IN nearshore waters until 10 PM Monday.

&&

$$

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Area Forecast Discussion...Updated

National Weather Service Saint Louis MO

 926 PM CDT Sun Mar 14 2021

.UPDATE...
Issued at 922 PM CDT Sun Mar 14 2021

The current forecast is on target with a wet and windy night on
tap. Since late afternoon we have been seeing periodic west-east
oriented bands of light rain across central/eastern MO into west
central IL. These northward moving bands are associated with low-
level WAA and moisture convergence and low-mid level frontogenetic
forcing. Later this evening/overnight the more prominent NW-SE
arcing band of rain associated with synoptic scale forcing and
the warm conveyor belt will translate eastward across the CWA,
attendant with the slow eastward migration of the large
extratropical cyclone into the Plains. Weak elevated CAPE (< 200
j/kg) is progged across southeast MO as the band moves eastward
overnight, so a rumble or two of thunder remains possible.
Otherwise the band should produce an additional 0.50-1.00 inch of
rain, by the time it exits in the 15-16z time frame. A rather
tight surface pressure gradient resulting from the Plains cyclone
and surface high in the Great Lakes region will continue to
generate impressive easterly winds, gusting as high as 40 mph or
so the remainder of the evening and overnight.

We are still closely watching the potential for some vigorous
thunderstorms between 21-01z across parts of central MO, and
maybe east central MO, in the vicinity of the occluded front/warm
front. The RAP is suggesting the combination of heating after
skies clear in the afternoon and steep lapse rates aloft could
result in MLCAPE approaching 500 J/KG. This in combination with
strong deep layer shear could result in some organized low-topped
storms. Low freezing levels and low wet bulb zero heights would
suggest hail would be the primary threat.

Glass

&&

.SHORT TERM...  (Through Late Monday Night)
Issued at 249 PM CDT Sun Mar 14 2021

Currently, an upper-level low is slowly moving through the Plains,
and its associated surface low can be seen on visible satellite
spinning across eastern Colorado and western Kansas. Over the Middle
Mississippi Valley, a band of light rain associated with an area
frontogenesis is currently on the northeastern edge of the CWA and
is expected to continue drifting northward and weaken. The remainder
of the afternoon into the early evening will remain cloudy with a
chance of isolated showers thanks to low-level warm air advection
ahead of the approaching surface low.

The leading edge of the main swath of rain associated with the low
is currently pushing into western Missouri, and is expected to push
eastward into the CWA this evening. This rain will transition
through the area rather quickly this evening and overnight, limiting
the flooding potential. Rainfall totals by tomorrow morning when the
rain ends will top out around 0.50-0.75" area wide. Instability will
be limited with this rain, but there may be enough across far
southeastern Missouri and far southern Illinois to produce a rumble
of thunder or two overnight.

An item of concern is the low-level jet this evening into early
tomorrow morning. Guidance has a narrow swath of ~50 kt
easterly/southeasterly winds at 925 mb primarily over northeastern
Missouri this evening drifting into western Illinois during the
morning. If these winds are able to overcome the stable layer and
mix down to the surface, they may produce gusts of 40+ mph primarily
north of the I-70 corridor. If this were to happen, it would most
likely occur in pockets of heavier rainfall and be sporadic and
short lived. Confidence is higher in gusts topping out in the 30-40
mph range overnight into the morning over this portion of the CWA.

The band of rain will depart the CWA to the east tomorrow morning,
providing a brief lull in precipitation chances. An occluded front
will stall along the I-70 corridor, and the weakening surface low
will track along it through the day. Upper-level divergence and weak
differential vorticity advection from the upper-level low pivoting
northward over the Middle Mississippi Valley will spark showers
along and north of the front during the afternoon and evening, and
guidance depicts a couple hundred J/kg of MUCAPE across the CWA with
this activity. With steep lapse rates in place, I can`t rule a low-
top thunderstorm or accompanying the showers. These storms may be
capable of producing small hail thanks to the freezing level
hovering around 800 mb and 0-6 km bulk shear of at least 50 kts. The
rain/storm chances will diminish through the evening.


Elmore

.LONG TERM...  (Tuesday through Next Sunday)
Issued at 249 PM CDT Sun Mar 14 2021

On Tuesday, the upper-level low over the Midwest will be in the
process of decaying and becoming sheared apart as another upper-
level low moves out of the Desert Southwest and into the Southern
Plains. Upper-level flow over the Middle Mississippi Valley will
initially be zonal, but slowly transition to southwesterly through
the day. Low-level flow will follow suit, and begin advecting warm,
moist Gulf air over the CWA later on Tuesday ahead of the previously
mentioned upper-level low moving into the Plains. The surface low
associated with this feature is set to develop over the Southern
Plains and track northeastward toward the Middle Mississippi Valley.
While the consensus among ensemble guidance is that the CWA will see
another round of rain starting late Tuesday night into Thursday with
this system, there is still much spread on the speed and track of
the low. This has implications on storm potential, where a more
northerly low track would put at least the southern portion of the
CWA in the warm sector with a heightened shear and instability
parameter space. With this scenario, a severe weather threat would
be possible, and this is supported by the CIPS Severe Probability
Guidance, which has had placed a heightened probability of severe
weather across southeastern Missouri and southwest Illinois over the
last several runs. A more southerly track would keep the warm sector
south of the CWA and mitigate the threat. The spread among guidance
does not give me enough confidence to say which scenario is more
likely at the moment, and we`ll need to watch this closely in the
upcoming days.

The chance of rain diminishes through the day on Thursday as the
surface low continues eastward. In its wake, flow through the
atmosphere over the Middle Mississippi Valley will be
northerly/northwesterly, advecting cooler air into the CWA and
keeping temperatures 5-10 degrees below normal through the end of
the week. Temperatures will begin to rise as we enter the weekend in
response to upper level ridging building into the Middle Mississippi
Valley.


Elmore

&&

.AVIATION...  (For the 00z TAFs through 00z Monday Evening)
Issued at 638 PM CDT Sun Mar 14 2021

Strong and gusty east winds will persist much of the night. These
strong winds increase rather uniformly with height through the
lowest 3000 feet AGL.

Otherwise intermittent light rain is expected to impact the
terminals this evening, especially KCOU and KUIN. Flight conditions
at KCOU are expected to be predominately MVFR, and VFR at the
other terminals. A more solid and continuous band of rain will
then move west to east across the region overnight, impacting all
the terminals and accompanied by deteriorating flight conditions,
both cigs and visibilities. The rain should have exited the area
by 14z however IFR flight conditions are expected to persist in
it`s wake. By midday flight conditions are expected to improve
with KCOU and the St. Louis metro terminals VFR by early
afternoon. Scattered thunderstorms will be possible after 21z in
middle MO hence the inclusion of VCTS at KCOU.

SPECIFICS FOR KSTL:

Strong and gusty east winds will persist much of the night. These
strong winds increase rather uniformly with height through the
lowest 3000 feet AGL.

Intermittent light rain is expected to impact KSTL this evening
with flight conditions remaining VFR. A more solid and continuous
band of rain will then move into the terminal overnight
accompanied by deteriorating flight conditions, both cigs and
visibilities. The rain should have exited by 14z however IFR
flight conditions are expected to persist in it`s wake. Flight
conditions will improve by midday with VFR by early afternoon.

Glass

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX




Area Forecast Discussion

National Weather Service Pueblo CO

 929 PM MDT Sun Mar 14 2021

.UPDATE...
Issued at 919 PM MDT Sun Mar 14 2021

Will be ending Winter Storm Warnings for the Sangres/Wets and srn
El Paso County with this update, and taking down the advisory for
the San Juans/La Garitas as well. Will hold on to warnings for
the central mountains for at least a couple more hrs, and will
likely keep nrn El Paso and Teller county warnings going through
midnight as combination of light snow and blowing/drifting snow
will keep will visibility low for a few more hrs.

UPDATE Issued at 548 PM MDT Sun Mar 14 2021

Ended winter storm warnings for the Arkansas Valley from Canon
City up through Salida and Buena Vista, as obs and radar show only
a few snow showers these areas, and latest HRRR has only very
light precip for the remainder of the night. Will leave mountain
highlights up a couple more hrs, though suspect all but Teller and
nrn El Paso County can be dropped at some point this evening.

&&

.SHORT TERM...(This evening through Monday)
Issued at 316 PM MDT Sun Mar 14 2021

...Blizzard Conditions Continue for Northern El Paso County through
Midnight...

Upper low continues to spin over eastern CO with upper low center
around 20 miles northwest of Lamar.  Moderate to heavy
precipitation/snow continues within the TROWAL region wrapping
around the west side of the upper low across the I-25 corridor and
adjacent plains. There are embedded convective elements across the
southeast plains along its eastern edge extending towards the upper
low center. Heaviest snow continues to fall across El Paso county
where temperatures have been sufficiently cold for an all snow
precipitation type. And strong northerly winds around the back side
of the system has pulled 45 kt wind gusts down to the surface along
across northern El Paso county southward through Pueblo county and
eastern portions of Huerfano and Las Animas counties.  This has
resulted in blizzard conditions for northern El Paso county where
winds and snow have caused visibilities to drop to 1/4 mile or less.
Seeing 12 to 18 inch snowfall reports so far across northern El Paso
county and northern Teller Counties.  With wrap around precipitation
expected to continue for a few more hours some areas could see an
additional 2-6 inches before the storm pulls east and snowfall
diminishes around midnight.  Current headlines will come down from
06z and 12z. Considered changing the ending time to midnight for the
southeast mountains and eastern San Juans but given the persistence
of some snow bands around western side of upper low which have not
been resolved well by some high res models, decided to leave
highlights as is and later shifts can end them sooner if need be.
Winds also decrease across the plains after midnight so ending time
of midnight for the Blizzard warning still looks on track as well.
Also watching some intense snow bands across the southern I-25
corridor this afternoon as well.  So far impacts to roads have been
minimal with day time warmth keeping roads just wet, but visibility
has been low at times.

Also watching some embedded convection across the far southeast
plains this evening.  So far have seem some CAPE up to 200 J/kg with
most of the lightning just clipping by northeast Kiowa county.  As
temperatures cool this evening, could see an inch or two of snowfall
across Kiowa county as the wrap around precipitation pulls eastward
into this area.  Given the warm road temperatures, do not think
advisories will be needed but this area will be monitored closely.

Southern Colorado will be in between systems on Monday as potent
storm system pulls away to the east and the next makes its way
through southern CA. Have cooled down high temperatures over snow
pack areas but all other areas should see a rebound in temperatures
and a day of melting. -KT

.LONG TERM...(Monday night through Sunday)
Issued at 316 PM MDT Sun Mar 14 2021

The operational models are in decent agreement through the extended
with the next upper system impacting the area early this week,
followed by drier weather mid to late week.  Ensemble spreads are
overall low, with modest confidence through the extended period.

Monday night...upper level shortwave ridging will be transiting the
region during the overnight hours ahead of the next upper storm
system. For much of the overnight period, it will remain dry.  A few
snow showers will likely move into the Continental Divide late and
increase in coverage by Tuesday morning.  Overnight lows will range
for the teens over the San Luis Valley, to 20s across the Plains.

Tuesday into Wednesday...a quick moving upper level low is forecast
to move across the Desert Southwest and into Oklahoma during this
period.  Given the current projected storm track across New Mexico,
a cold front will back west across the Plains on Tuesday, with
upslope flow wrapping around the system through 700 mb.  This will
lead to another round of snowfall for the Eastern Mountains, south
into the Raton Mesa region from Tuesday afternoon through Wednesday
morning.  Snow amounts remain in question with the onset looking
like rain for the lower elevations.  As we cool Tuesday night into
Wednesday, any rain should transition to snow, before coming to an
end Wednesday afternoon as the system quickly ejects into Oklahoma.
Mountain locations over the San Juans, Southern Sangre de Cristo and
Wet Mountains could see 3 to 7 inches, with locally higher amounts
possible.  For the lower elevations including the southern I-25
corridor, 1 to 4 inches may be possible, especially if this area
transitions to snow.  For the rest of the area, an inch or two may
be possible late Tuesday night and Wednesday morning.  Much will
depend on the exact storm track as slight shifts could mean more or
less snowfall.  It is also a very quick moving system, which will
likely limit snowfall potential to expected totals listed above.
Temperatures will be on the cooler side both Tuesday and Wednesday,
with 40s across the lower elevations.

Thursday through Saturday...upper level high pressure will slowly
shift east across the state with dry conditions expected.
Temperatures will also warm from the 50s on Thursday, to near 70 on
Saturday.  As the upper system shifts east, flow aloft will
transition southwesterly.  Breezy conditions are possible on
Saturday across the Plains.  Southwesterly flow will also favor a
few snow showers along the Continental Divide by the weekend.

Sunday...the next upper trough will begin to impact the region by
next Sunday.  Snow will likely increase along the Continental
Divide, and spread eastward to the Plains by late in the day. Given
that this is a week out, much is subject to change with this storm
system. Mozley

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 316 PM MDT Sun Mar 14 2021

IFR to LIFR conditions will continue at KCOS for a couple more hours
before the snow pulls back to northern El Paso county and cigs and
vis improve.  KPUB will remain VFR with brief drops into the MVFR
category with -SHRA/-SN.  Winds will gust to around 45 kts through
around 03z before decreasing at both KCOS and KPUB though gusts to
around 25 to 30 kts will be possible through much of the night.
Should see clearing skies Monday morning with VFR conditions and
winds becoming light and diurnally driven in the afternoon for both
terminals.

KALS will still see a chance for -SHSN for a couple hours this
evening before skies clear out towards morning.  Winds will become
light southerly with speeds under 15 kts for KALS Monday afternoon.
-KT


&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Blizzard Warning until midnight MDT tonight for COZ084.

Winter Storm Warning until 6 AM MDT Monday for COZ058>061-063-
081-082.

&&

$$

UPDATE...PETERSEN
SHORT TERM...KT
LONG TERM...MOZLEY
AVIATION...KT