SPC MD 1664


MD 1664 Image

Mesoscale Discussion 1664
NWS Storm Prediction Center Norman OK
0654 PM CST Sun Nov 25 2018

Areas affected...Northern IL and adjacent portions of Eastern
IA/Southern WI


Valid 260054Z - 260700Z

SUMMARY...Heavy snow will spread into a larger portion of northern
IL this evening. As stronger winds move in from the west, blizzard
conditions will expand later tonight across the region.

DISCUSSION...00Z surface analysis depicts a 993 mb surface cyclone
just northeast of St. Louis. To the north and northwest of the low,
heavy snow is ongoing from northeast MO into northwest IL, with
stronger winds in the northwestern quadrant of the cyclone producing
blizzard conditions. Dual pol products from KILX/KLOT and recent
surface obs and mPing reports indicate that the rain/snow line is
moving eastward across northern IL, and this trend is expected to
continue as backing surface winds result in increasing low-level
cold advection to the north and northwest of the east-northeastward
moving surface low. Snow should continue spreading into most of the
Chicagoland area between now and 02Z, though areas in the immediate
vicinity of Lake Michigan may see a longer period of mixed
precipitation as northeasterly winds off of the lake maintain a
slightly warmer near-surface layer. 

Substantial convection has been noted near the surface low moving
into southern IL, with a convective character to the precip (and
some thundersnow reports) also noted within cooling cloud tops
across northern IL. Strong low/midlevel frontogenesis will continue
to favor moderate-to-heavy snow to the north of the midlevel low,
with some convective enhancement possible just north of the midlevel
dry slot, where relatively steep lapse rates (in excess of 7 C/km as
noted on ILX/DVN 00Z soundings) will be maintained. Snow rates of
1-3 inches per hour are expected within the primary snow band, which
should shift gradually eastward into northeast IL by late tonight. 

Strong winds (gusts in excess of 40 kt) are resulting in ongoing
blizzard conditions from northeast MO into northwest IL. These
stronger winds will expand eastward with time tonight in conjunction
with the movement of the surface low, resulting in an expansion of
blizzard conditions into northeast IL and perhaps far southeast WI
after 03Z tonight.

..Dean.. 11/26/2018

...Please see www.spc.noaa.gov for graphic product...


LAT...LON   41349111 42049035 42668896 42768779 42008763 41628760
            40978822 40948870 41228944 41369046 41349111 

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SPC MD 1659


MD 1659 Image

Mesoscale Discussion 1659
NWS Storm Prediction Center Norman OK
1059 AM CST Sun Nov 25 2018

Areas affected...Central/eastern Kansas...northwest Missouri...far
southeast Nebraska...southwest Iowa


Valid 251659Z - 252200Z

SUMMARY...1-2 inch/hr snowfall rates expected to continue for
several more hours across the area, with occasional blizzard
conditions likely northwest of the surface low.

DISCUSSION...A 998 mb surface low, currently located across
southwest Missouri, is expected to continue moving northeast in
tandem with a pronounced upper-level shortwave trough. The
upper-level trough will continue to deepen throughout the afternoon,
with 500-300 mb relative wind maxima expected to traverse the base
of the trough this afternoon. As a result, large scale ascent is
expected to increase across the area, where strong 925-700 mb WAA
and moisture advection ahead and to the north of the surface low are
currently underway. 

Increasing divergence aloft associated with the approaching
aforementioned upper-level wind maxima will encourage further
deepening of the surface low, with increases in surface wind speeds
likely. Blizzard conditions have already been reported across
several portions of central/northeast Kansas into far southeast
Nebraska, and these conditions are expected to continue across much
of the outlined area as the low continues eastward. Areas roughly
from Washington to Kingman County Kansas westward may continue to
experience near white-out conditions for a few more hours, but the
threat is expected to clear as snow moves out of the area. 

Otherwise, 1-2 inch/hr snowfall rates should pivot eastward across
far northeast Kansas into northwest Missouri and southwest Iowa,
along the axis of a moisture conveyer belt, where low-level warm
air/moisture advection should continue to saturate the
dentritic-growth layer.

..Squitieri.. 11/25/2018

...Please see www.spc.noaa.gov for graphic product...


LAT...LON   37389637 37379819 37539933 39149858 40259698 40729631
            41119438 41399290 41009233 40309223 39119280 38099510

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SPC MD 1658


MD 1658 Image

Mesoscale Discussion 1658
NWS Storm Prediction Center Norman OK
0354 AM CST Sun Nov 25 2018

Areas affected...Central...north-central and northeast
KS...southeast NE...southwest IA...and northwest MO

Concerning...Heavy snow 

Valid 250954Z - 251600Z

SUMMARY...Snowfall rates up to 1-2 inches per hour will increase
from west to east during the late overnight through this morning. 
In addition to heavy snow, strengthening northerly winds through the
morning will produce a blizzard with reduced visibilities in
whiteout conditions.

DISCUSSION...Short-term guidance remains consistent with the
forecast for a vigorous shortwave trough, now located over eastern
CO, to emerge eastward across KS overnight, with deepening of this
system between 12-18Z as it reaches eastern KS/western MO by late
morning.  Trends in mosaic radar imagery showed a band of
precipitation had developed from north-central KS to southeast NE. 
This corridor in the northern part of the discussion area is
expected to be the first southwest-northeast oriented zone to change
to snow and increase in rates as surface temperatures fall through
the lower 30s to upper 20s F by 11-12Z.  This same trend with snow
developing across the rest of the discussion area after daybreak
from central to northeast KS and far northwest MO to southwest IA
will occur as the surface low shifts east-northeast into MO.  This
will allow low-level winds on its north-northwest periphery to back
to northerly and strengthen, ushering in colder temperatures, and
supporting a high likelihood for reduced visibilities in whiteout

Meanwhile, an increase in upward vertical motion through the
dendritic-growth zone per forecast soundings is expected as, 1) the
shortwave trough deepens with eastward progression and 2) within the
exit region of a strengthening 500-mb 100-kt jet spreading across
northeast KS/northwest MO this morning.  This factor which is
expected to become stronger by 15-18Z suggests snowfall rates could
be up to 2 inches per hour, generally north of a line from KSLN to
KSTJ to 25 S KLWD, while the initial aforementioned band of snow
could have rates up to 1 inch per hour.  Forecast soundings also
indicated weak elevated instability rooted around 600 mb, given the
likelihood of steepening midlevel lapse rates (around 8 C/km) in the
exit region of the midlevel jet.  This could enhance snowfall rates.

..Peters.. 11/25/2018

...Please see www.spc.noaa.gov for graphic product...


LAT...LON   41259537 41359315 41159252 40309380 39249539 38409689
            38239774 38379854 38699916 38909976 39289995 39479979
            40099877 40489775 40979632 41259537 

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SPC MD 1648


MD 1648 Image

Mesoscale Discussion 1648
NWS Storm Prediction Center Norman OK
0856 AM CST Thu Nov 15 2018

Areas affected...Central Appalachians...Mid Atlantic

Concerning...Winter mixed precipitation 

Valid 151456Z - 152100Z

SUMMARY...Areas of heavy snow are likely to develop in the higher
elevations of the central Appalachian Mountains this morning. By
afternoon, a mixture of snow and sleet are likely in the lower
elevations from northern Virginia into northern New Jersey. This
corridor may changeover to freezing rain or rain this afternoon.

DISCUSSION...The latest water vapor imagery shows an upper-level low
in the mid Mississippi Valley with southwest mid-level flow over
much of the eastern Seaboard. At the surface, a large area of high
pressure is in place across the Northeast. Surface temperatures are
below freezing in most of the central Appalachians with dewpoints
mostly in the teens. As a large area of precipitation moves across
the central Appalachians this morning, the temperature profile will
support the development of snow.  Areas of heavy snow will be
possible especially in the higher elevations of the central
Appalachian Mountains where 1 inch per hour snowfall rates may

Surface temperatures from northern Virginia northeastward to
northern Maryland are currently just below freezing. At this time,
light snow is being reported along this corridor. This snow will
likely develop northeastward into southeast Pennsylvania and
northern New Jersey late this morning. As warm advection continues
over the top of the cold airmass late this morning into early
afternoon, a changeover to sleet, freezing rain and rain will be
possible from northern Virginia to northern New Jersey.

..Broyles/Hart.. 11/15/2018

...Please see www.spc.noaa.gov for graphic product...


LAT...LON   38327873 38517974 39167986 40567961 41717904 42067799
            41907558 41547397 40537401 39307622 38597785 38327873 

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SPC MD 1580


MD 1580 Image

Mesoscale Discussion 1580
NWS Storm Prediction Center Norman OK
0741 PM CDT Sat Oct 13 2018

Areas affected...Part of central and eastern TX

Concerning...Tornado Watch 414...

Valid 140041Z - 140145Z

The severe weather threat for Tornado Watch 414 continues.

SUMMARY...Local extension (both spatial and temporal) may be needed
for the southwest part of WW 414 and extending southward several
counties, as a severe-weather threat persists beyond 01Z, including
the tornado potential.

DISCUSSION...Mosaic radar imagery showed storms continuing to
develop within the the southwest flank of a central and northeast TX
MCS, while GOES-16 IR imagery indicated ongoing cloud-top cooling
across this same area of the MCS.  Although the main band of storms
appears to be located along and near the primary southward-moving
outflow boundary, radar trends also indicated new storms developing
in the warm sector, immediately to the south, from Burleson to
Brazos to Madison Counties.  Objective analyses indicated
surface-based inhibition has been increasing, given time of day
across east TX into LA, though the environment in proximity to the
aforementioned storms remains unstable with surface-based storms.

Given the presence of a moisture-rich environment with moderate
instability and effective bulk shear of 40-45 kt, embedded bowing
structures and low-level rotation/tornado threat should persist
until the surface-based inhibition becomes too strong.

..Peters/Guyer.. 10/14/2018

...Please see www.spc.noaa.gov for graphic product...


LAT...LON   30769657 31099580 31579529 31779461 31809422 31299431
            31049470 30689489 30369556 30199614 30159656 30589670

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SPC MD 1570


MD 1570 Image

Mesoscale Discussion 1570
NWS Storm Prediction Center Norman OK
0244 PM CDT Fri Oct 12 2018

Areas affected...portions of far West Texas

Concerning...Severe potential...Watch unlikely 

Valid 121944Z - 122145Z

Probability of Watch Issuance...20 percent

SUMMARY...A couple of strong/locally severe storms could evolve this
afternoon near the higher terrain of west Texas.  WW issuance is not
anticipated for this potential/initial risk.

DISCUSSION...Latest visible satellite imagery indicated TCU
development over the higher terrain of far West Texas -- i.e.
portions of Jeff Davis, Brewster, and Pecos Counties, where clearing
of the cloud cover has allowed differential heating to occur over
the higher terrain.  With modest (low 60s) dewpoints indicated
across this region, the heating has contributed to gradual
destabilization (surface-based CAPE values in the 500 to 1500 J/kg
range per latest objective analyses).

The cu field remains suppressed away from the high terrain,
indicative of modest larger-scale ascent at best.  Even over the
higher terrain, TCU continue to shed any glaciated tops, again
suggestive of a larger-scale environment not yet supportive of
robust deep updrafts.

With time, continued heating and the gradual approach of Sergio from
the west may support isolated CB development over the mountains
through diurnal peak heating.  With moderately strong
west-southwesterly mid-level flow, updraft organization -- and
possible, attendant risk for hail -- could occur locally.  This risk
however should remain isolated at best into the evening hours.

Later this evening, as Sergio continues to approach, more
substantial convective development/coverage is expected, which could
result in the need for WW issuance consideration at that time.

..Goss/Grams.. 10/12/2018

...Please see www.spc.noaa.gov for graphic product...


LAT...LON   30640426 31030401 31340319 31260272 31220254 30950208
            30530199 29960268 29370339 29890403 30640426 

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SPC MD 1552


MD 1552 Image

Mesoscale Discussion 1552
NWS Storm Prediction Center Norman OK
0306 PM CDT Tue Oct 09 2018

Areas affected...Eastern Kansas...western Missouri and northwestern

Concerning...Tornado Watch 403...404...

Valid 092006Z - 092130Z

The severe weather threat for Tornado Watch 403, 404 continues.

SUMMARY...Thunderstorms developing across the region may pose a risk
for tornadoes and localized strong wind gusts through 6-7 PM CDT

DISCUSSION...The slowly deepening surface low center appears in the
process of developing to the east/northeast of Salina KS, and likely
to continue northeastward toward the Falls City NE area through
23-00Z.  Large clockwise curved low-level hodographs are focused
within the warm sector in close proximity to the low, and along/to
the immediate east of the arcing convective band now advancing into
the Kansas City metro area.  

A number of cells within the convective band, as well as along a
remnant convective boundary extending northeastward (roughly along
the Interstate 35 corridor) are slowly organizing and intensifying
in the presence of high boundary layer moisture content (surface dew
points now near 70f) and weak to modest CAPE (up to 1000 J/kg).  
This environment appears conducive to occasional continuing
development of low-level mesocyclones, accompanied by a risk for
tornadoes and/or locally damaging wind gusts, and will gradually
shift northeast of the Kansas City area toward the Missouri/Iowa
border area through early evening.

..Kerr.. 10/09/2018

...Please see www.spc.noaa.gov for graphic product...


LAT...LON   40739347 40489299 40109259 38639401 37829350 37169349
            37469440 38229510 38959583 39549525 40489442 40739347 

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SPC MD 1549


MD 1549 Image

Mesoscale Discussion 1549
NWS Storm Prediction Center Norman OK
1131 AM CDT Tue Oct 09 2018

Areas affected...Eastern Kansas...western Missouri...northeast
Oklahoma and adjacent northwest Arkansas

Concerning...Tornado Watch 402...

Valid 091631Z - 091800Z

The severe weather threat for Tornado Watch 402 continues.

SUMMARY...Increasing thunderstorm development expected through 2-4
PM CDT, accompanied by a risk for tornadoes and localized damaging
wind gusts.  A new watch may become necessary within the next hour
or two.

DISCUSSION...A narrow line of convection with embedded
thunderstorms, within the warm sector of the developing surface low,
continues to advance northeastward around 30-35 kt.  Activity will
spread northeast of the watch within the next hour or two.  

The surface low, currently near the Kansas/Oklahoma border to the
south of Wichita, continues to slowly deepen, and is forecast to
migrate north/northeastward toward the Salina KS vicinity through
19-21Z.  As it does, strongest southerly 850 mb flow (in excess of
40 kt) appears likely to develop northward across much of eastern
Kansas and adjacent western Missouri.  

This will be accompanied by enlargement of low-level hodographs,
particularly along a remnant convectively generated boundary that
appears roughly aligned with the Interstate 35 corridor.  Although
cloud cover and rain is slowing destabilization along this corridor,
breaks in overcast coupled with further gradual boundary layer
moistening should allow for increasing boundary layer instability
through mid to late afternoon.  As it does, the environment may
become increasingly conducive to the development of low-level
mesocyclones within strengthening convection, accompanied by a risk
for tornadoes and localized damaging wind gusts.

..Kerr.. 10/09/2018

...Please see www.spc.noaa.gov for graphic product...


LAT...LON   38059651 39229565 40399395 38819342 37569306 35559390
            35169520 36379581 37419638 38059651 

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SPC MD 1541


MD 1541 Image

Mesoscale Discussion 1541
NWS Storm Prediction Center Norman OK
0149 PM CDT Mon Oct 08 2018

Areas affected...Parts of south central through northeast Kansas and
adjacent southeast Nebraska/northwest Missouri

Concerning...Severe potential...Watch unlikely 

Valid 081849Z - 082045Z

Probability of Watch Issuance...5 percent

SUMMARY...Scattered thunderstorms are expected to continue
developing across the region through 4-5 PM CDT, perhaps accompanied
by some risk for a tornado or two, or localized damaging wind gusts.
 This threat currently appears low enough that a watch probably is
not necessary, but trends will continue to be monitored.

DISCUSSION...The bulk of the ongoing convective development appears
largely supported by forcing for ascent due to low/mid-level warm
advection, to the cool side of a convectively generated pre-frontal
surface boundary.  This boundary generally extends along or just
south of the Interstate 35 corridor of eastern Kansas, southwestward
into northwestern Oklahoma.

However, along and ahead of the leading edge of the more widespread
rain, insolation appears to be contributing to a corridor of
boundary layer destabilization (CAPE increasing up to 1000 J/kg. 
This may support increasing/intensifying thunderstorm activity
during the next few hours, as far north as a weak low on the front,
now northwest of Fort Riley.  

Through 21-22Z, models suggest that this low/frontal wave may slowly
migrate northeastward into southeastern Nebraska.  Near and in close
proximity to the southeast of this feature, beneath 30-40 kt
south/southwesterly 850 mb flow, southeasterly near surface winds
likely will maintain sizable low-level hodographs.  With further
boundary layer warming and moistening, it appears possible that the
environment may become marginally conducive to the development of
occasional low-level mesocyclones, accompanied by at least some risk
for a relatively short-lived tornado or two, in additional to
localized straight-line wind gusts.

..Kerr/Grams.. 10/08/2018

...Please see www.spc.noaa.gov for graphic product...


LAT...LON   38959683 39659670 40109623 40519499 39799451 38839523
            37869646 37999693 38959683 

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SPC MD 1529


MD 1529 Image

Mesoscale Discussion 1529
NWS Storm Prediction Center Norman OK
0744 PM CDT Fri Oct 05 2018

Areas affected...Portions of southwest/central Kansas

Concerning...Severe potential...Watch unlikely 

Valid 060044Z - 060215Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated severe storms will continue to pose a primary
threat of large hail this evening, although strong gusty winds will
be possible too. Still, the severe threat is not expected to be
organized enough to necessitate a watch.

DISCUSSION...Aided by enhanced convergence/isentropic ascent along a
composite cold front/outflow boundary, a cluster of strong to severe
storms has expanded across central Kansas this evening. As the
low-level jet further intensifies this evening, a few more cells may
develop to the southwest, generally in the direction of Dodge City. 

The 00Z DDC sounding sampled around 50 kt of west/southwest 500mb
flow, which is supporting some initial supercellular evolution.
Combined with MLCAPE upwards of 2000 J/kg, instances of large hail
appear possible. However, south/southeastward advance of the front,
combined with some dry air and nocturnal inhibition slowing parcel
ascent slightly, should lead to cells becoming progressively
elevated atop the frontal surface. Therefore, the overall severe
threat should be limited enough to preclude watch issuance.

..Picca/Thompson.. 10/06/2018

...Please see www.spc.noaa.gov for graphic product...


LAT...LON   37839907 37729982 37740033 37880034 38050014 38319984
            38789927 39499852 39709812 39739783 39719731 39529701
            39189688 38269760 37839907 

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