ACUS11 KWNS 292018
SWOMCD
SPC MCD 292017
ILZ000-WIZ000-IAZ000-300015-

Mesoscale Discussion 1885
NWS Storm Prediction Center Norman OK
0217 PM CST Tue Dec 29 2020

Areas affected...Central/eastern IA...Northern IL...Southern WI

Concerning...Heavy snow

Valid 292017Z - 300015Z

SUMMARY...Snow rates of 1 inch or greater per hour will spread
eastward through the afternoon into the early evening. Snow may
eventually transition to sleet and freezing rain from southern Iowa
into northwest Illinois, with the heaviest snow rates expected just
north of the transition zone.

DISCUSSION...At 20Z, moderate to occasionally heavy winter
precipitation is spreading eastward across IA into portions of
southwest WI and northwest IL. Precipitation is primarily snow
across IA, though a transition to sleet/freezing rain has been noted
across far southwest/south-central IA, based on surface observations
and radar. Low-level warm advection will continue to support strong
ascent and also result in a gradual northeastward shift of the snow/sleet/freezing rain transition zone with time.

Increasing frontogenesis within the 900-700 mb layer will continue
to support occasionally heavy precipitation rates, and possibly some
organized snow bands where rates may approach 2 inches/hour at
times. The heaviest snow rates are expected just north of the snow
to sleet/freezing rain transition zone, with several hours of
moderate-to-heavy snow possible from central/east-central IA into
northwest IL and far southwest WI by early evening. The southern
portion of the MCD area will likely transition to sleet/freezing
rain by 00Z.

..Dean.. 12/29/2020

ATTN...WFO...LOT...ILX...MKX...DVN...ARX...DMX...

LAT...LON 41739401 42239390 42489350 42789235 42919153 42969064
42978986 42778905 42238859 41758872 41448916 41288956
41168983 41039060 40979115 41019208 41149341 41369396
41739401
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ACUS11 KWNS 292152
SWOMCD
SPC MCD 292152
MIZ000-INZ000-ILZ000-WIZ000-300145-

Mesoscale Discussion 1886
NWS Storm Prediction Center Norman OK
0352 PM CST Tue Dec 29 2020

Areas affected...Northeast IL...Southeast WI...Far Northwest IN

Concerning...Heavy snow

Valid 292152Z - 300145Z

SUMMARY...Occasional snow rates of 1+ inch per hour will be likely
late this afternoon into the evening, as precipitation spreads in
from the west. A transition to sleet/freezing rain is expected
across much of this area later tonight.

DISCUSSION...At 2145Z, snow was increasing across northeast IL and
spreading into southeast WI, with rates approaching 1 inch per hour
likely ongoing across the southwest Chicago suburbs, where
saturation of an initially dry airmass has allowed for precipitation
to reach the ground. As a large area of precipitation continues to
spread in from the west, favorable ascent within the dendritic
growth zone will allow for heavier bands of snow with maximum rates
exceeding 1 inch per hour through 00Z. Moderate to locally heavy
precip rates will likely continue into the evening, though continued
low-level warm advection will result in an eventual changeover to
sleet or freezing rain later tonight across northeast IL into far
southeast WI.

..Dean.. 12/29/2020

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fjg!qoMNv8wggyniJN-9dtCYZe4nHSa5p1YxqZysGb_zL_0ezPBbMUlCdsYbtc-lGMLWcw9ZqHlc$
for graphic product...

ATTN...WFO...IWX...LOT...ILX...MKX...DVN...

LAT...LON 43078908 43388845 43348785 42488702 41798677 41268676
40818684 40798804 40958894 41278922 41428891 41558868
41838853 42498872 43078908
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ACUS11 KWNS 101015
SWOMCD
SPC MCD 101014
TXZ000-NMZ000-101415-

Mesoscale Discussion 0016
NWS Storm Prediction Center Norman OK
0414 AM CST Sun Jan 10 2021

Areas affected...Far Southeast NM...TX Permian Basin and Big Country

Concerning...Heavy snow

Valid 101014Z - 101415Z

SUMMARY...Occasionally heavy snowfall with rates around 1" per hour
are possible from the Permian Basin into the TX Big Country over the
next several hours.

DISCUSSION...A well-defined shortwave trough continues to dig
southeastward across the southern High Plains. Strong low to
mid-level flow ahead of this shortwave is contributing to an
expansive band of precipitation from far southeast NM southeastward
into the TX Hill Country. Surface observations are reporting snow
from HOB (into far southeast NM) to as far east as SNK (in the TX
Big Country). A low-level dry layer is likely preventing
precipitation from reaching the surface east/southeast of SNK.

The shortwave trough is expected to continue southeastward over the
next few hours, with the strong low to mid-level
southerly/southeasterly flow ahead of it persisting. This will
result in continued warm-air advection with resulting
maintenance/expansion of the precipitation band. Additionally,
ascent attendant to the approaching shortwave is expected to augment
the warm-air advection, resulting in a deep layer of ascent through
the cold and moist mid-levels/dendritic growth layer. Consequently,
instances of heavy snow (i.e., snowfall rates around of 1" per hour)
are possible, particularly from between MAF and LBB eastward towards
ABI around 12-13Z.

..Mosier.. 01/10/2021

ATTN...WFO...FWD...SJT...LUB...MAF...

LAT...LON 32380289 32730363 33260342 33390128 32299905 31319942
31960125 32230204 32380289
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ACUS11 KWNS 161747
SWOMCD
SPC MCD 161747
MEZ000-162345-

Mesoscale Discussion 0022
NWS Storm Prediction Center Norman OK
1147 AM CST Sat Jan 16 2021

Areas affected...portions of northern/western Maine

Concerning...Heavy snow

Valid 161747Z - 162345Z

SUMMARY...Heavy snow will continue to develop northeast across the
discussion area through this afternoon. Snowfall rates of around
one inch/hour will be possible.

DISCUSSION...Strong low-level southeasterly flow and resultant
warm/moist advection continue to support a large area of
precipitation north/east of a surface low over eastern MA at 17z.
Forcing for ascent associated with the warm advection will continue
to shift northeast through this afternoon, supporting a mix of
precipitation types across northern New England.

Across the discussion area, the higher elevations will generally
support snow as the dominant precipitation type, although periods of
mixed precipitation will be possible. Forecast soundings from the
16z RAP and 12z NAM guidance show below freezing thermal profiles
and saturation/lift developing within the dendritic growth zone this
afternoon, and several hours of 1 to locally 2 inch/hour snowfall
rates will be possible. This trend is supported by recent guidance
from the HRRR and HREF ensemble.

..Bunting.. 01/16/2021

ATTN...WFO...CAR...GYX...

LAT...LON 45277083 45787035 46187020 46467002 46536932 46026907
45486947 45007024 44667073 44707091 44737097 44847099
44987101 45097100 45257097 45277083
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ACUS11 KWNS 252127
SWOMCD
SPC MCD 252126
IAZ000-ILZ000-MOZ000-NEZ000-260130-

Mesoscale Discussion 0032
NWS Storm Prediction Center Norman OK
0326 PM CST Mon Jan 25 2021

Areas affected...Southeast NE...Central/Southern IA...Far Northern
MO

Concerning...Heavy snow

Valid 252126Z - 260130Z

SUMMARY...Moderate to heavy snowfall is expected to persist from
southeast NE across central/southern IA into the evening. Snowfall
rates may occasionally exceed 2"/hr, particularly across far
southeast NE and southern IA.

DISCUSSION...Band of moderate to heavy snow is in place from
southeast NE northeastward across central/southern IA and far
northern MO. Heaviest snow is currently occurring along the southern
NE/IA border, where several sites are reporting +SN and low
visibility.

Expectation is for moderate to heavy snowfall to persist throughout
the region into the evening, with a higher probability of 1-2"/hr
snowfall rates along a corridor from LNK (in southeast NE) to OOA
(in south-central IA). In this corridor, ascent strength and depth
is expected to increase as the shortwave trough moves into the
region.

..Mosier.. 01/25/2021

ATTN...WFO...DVN...DMX...EAX...OAX...

LAT...LON 41369735 42069602 42509316 42539142 42069040 40449150
40099645 41369735
#
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ACUS11 KWNS 310023
SWOMCD
SPC MCD 310023
MIZ000-INZ000-ILZ000-IAZ000-310430-

Mesoscale Discussion 0047
NWS Storm Prediction Center Norman OK
0623 PM CST Sat Jan 30 2021

Areas affected...far eastern IA...northern IL...northwest IN

Concerning...Heavy snow

Valid 310023Z - 310430Z

SUMMARY...Heavy snowfall will gradually develop this evening with
rates generally in the 1.0-1.5 inches per hour range. Localized
heavier bursts briefly exceeding 1.5 inches per hour are possible.

DISCUSSION...Radar mosaic early this evening shows a broad
precipitation shield across the middle MS Valley spreading
northeastward into the southern Great Lakes. Water-vapor imagery
shows a potent mid-level shortwave trough migrating east-northeast
from the Ozarks and this feature will reach east-central IL by
midnight.

Strong isentropic lift is contributing to increasing precipitation
rates across central IL early this evening. As this zone of ascent
strengthens during the next 1-2 hours and heavier precipitation
moves northeast from central IL, the onset of heavier snowfall rates
will likely occur from near the MS River east into the south and
west suburbs of Chicago. Initially, a mixed precipitation type may
occur on the southern fringe of the MCD area (south of Chicago)
before changing to all snow later this evening. By mid evening,
model guidance indicates the heaviest snow will extend from northern
IL east into northwest IN. The heaviest rates (1.0-1.5 inches per
hour) will probably overspread Chicago and south suburbia during the
8pm-12am CST period.

..Smith.. 01/31/2021

ATTN...WFO...IWX...LOT...ILX...DVN...

LAT...LON 40928868 40818701 41378651 41788669 42119020 41869056
41479050 40928868
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ACUS11 KWNS 011843
SWOMCD
SPC MCD 011843 MAZ000-RIZ000-NHZ000-CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-020045-

Mesoscale Discussion 0052
NWS Storm Prediction Center Norman OK
1243 PM CST Mon Feb 01 2021

Areas affected...portions of far eastern Pennsylvania...central and
northern New Jersey...far southeast New York...Long Island...Connecticut...Rhode Island...Massachusetts

Concerning...Heavy snow

Valid 011843Z - 020045Z

SUMMARY...Up to 2-4 inch/hr snowfall rates will be possible across
portions of the lower Hudson Valley and southern New England this
afternoon, with occasional blizzard conditions possible across Long
Island. Portions of far eastern Pennsylvania into central New Jersey
will continue to experience a heavy sleet/snow mix.

DISCUSSION...A surface low continues to gradually deepen while
tracking slowly north-northeastward just off the Jersey shoreline as
a 110+ knot 300 mb jet traverses the Mid Atlantic/New England
Coastline. Strong 925-700 mb warm-air advection ahead/north of the
surface low continues to support ample mixed wintry
precipitation/heavy snowfall potential amidst a sub-freezing
tropospheric vertical profile and deep-layer ascent provided by
coupled low-level convergence with the surface low and upper-level
divergence by the strong 300 mb jet (per latest Mesoanalysis).
Latest KDIX/KOKX dual-polarimetric radar depicts a an east to west
snow/sleet transition zone roughly from KLOM to KISP. Latest METAR
observations also show 1-3 inch/hr snowfall rates ongoing just north
of this transition zone, and the heavier snow/sleet are expected to
gradually translate northward through the afternoon. METAR sites
also show 25 knot sustained northeasterly winds prevailing across
Long Island, along with heavy snow and higher gusts noted. As such,
brief and localized blizzard conditions are expected to persist.

Latest HREF, SREF, and last few runs of the HRRR suggest that
relatively lighter snowfall rates mixed with sleet will be the
predominant mode of precipitation from far eastern PA/central NJ
southward this afternoon, with a transition of sleet likely across
portions of Long Island and brief/localized blizzard conditions
still possible. Farther north across parts of southern New England,
the heavier band of wintry precipitation will progress northward,
with strong 700 mb warm-air advection and a near-saturated dendritic
growth zone supporting 1-3 inch/hr snowfall rates this afternoon, as
suggested by high-resolution model guidance. A few brief instances
of 4 inch/hr rates also cannot be ruled out.

..Squitieri.. 02/01/2021

ATTN...WFO...GYX...BOX...OKX...ALY...PHI...BGM...CTP...LWX...

LAT...LON 39747651 40457586 41297484 42247351 42687247 42767149
42507095 42067041 41917017 41727018 41367087 40977188
40567253 40237347 39957418 39767492 39637561 39747651
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ACUS11 KWNS 070925
SWOMCD
SPC MCD 070924
MDZ000-VAZ000-WVZ000-071530-

Mesoscale Discussion 0063
NWS Storm Prediction Center Norman OK
0324 AM CST Sun Feb 07 2021

Areas affected...Virginia...Southeast West Virginia

Concerning...Heavy snow

Valid 070924Z - 071530Z

SUMMARY...Moderate to heavy snow is expected to develop from
southeast West Virginia into western, central and northern Virginia
early this morning. Snowfall rates of 1 inch per hour will be
possible.

DISCUSSION...The latest mosaic radar imagery shows a large area of precipitation from the central Appalachians eastward to the
Mid-Atlantic. At this time, temperatures are below freezing at the
higher elevations across the central Appalachian Mountains, where
heavy snow was reported last hour in southeastern West Virginia.
This band of snow is forming ahead of a shortwave trough evident on
water vapor imagery. As the shortwave trough moves northeastward
across the central Appalachians early this morning, isentropic
ascent will increase markedly across much of western and central
Virginia. In response, moderate to heavy snow is forecast to develop
with the band across western and central Virginia. The band will
develop northeastward with time, reaching northern Virginia toward
daybreak. Snowfall rates are expected to peak near 1 inch per hour
in the heaviest part of the band. Snow accumulation rates will not
be maximized in areas where surface temperatures remain slightly
above freezing. The potential for this limitation appears greatest
across parts of east-central and northeast Virginia.

..Broyles.. 02/07/2021

ATTN...WFO...AKQ...LWX...RNK...RLX...

LAT...LON 36758145 37198147 37738115 38238006 38697904 38977836
39017761 38717711 38307704 37847737 37217850 36627966
36568085 36758145
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