SPC MD 129

MD 0129 Image

Mesoscale Discussion 0129
NWS Storm Prediction Center Norman OK
0526 PM CST Sat Feb 23 2019

Areas affected...Far eastern NE...western/central IA...southern MN

Concerning...Heavy snow 

Valid 232326Z - 240430Z

SUMMARY...Heavy snow rates of 1-2"/hour (locally greater) are
expected into this evening, with localized blizzard conditions
possible later this evening as winds increase from west to east.

DISCUSSION...Latest surface analysis depicts a deepening cyclone
centered near Kansas City at 23Z. WV imagery shows a well-developed
dry slot moving into southern IA, with thunderstorms noted on its
leading edge. Very strong deep-layer ascent to the northwest of the
low track is resulting in heavy snowfall rates in excess of 1"/hour
across eastern NE, with occasional blizzard conditions. The
rain/snow line has advanced through the Omaha area within the last
1-2 hours, with portions of northwest IA beginning to transition to

As the cyclone moves northeastward this evening and thermal profiles
cool due to strong ascent and increasing cold advection, heavy snow
will spread into a larger portion of central/northern IA and
southern MN. Snowfall rates of 1-2"/hour (locally higher) will
continue through the evening, with some thundersnow possible as
convective elements that develop on the apex of the dry slot feed
into the primary snow band. 

Blizzard conditions may also develop from west to east across this
region later this evening as low-level northwesterly flow increases
in response to the deepening surface low. While the increase in
winds may tend to coincide with decreasing snowfall rates on the
backside of the precipitation shield, increasing cold advection will
result in less water content with the remaining snowfall, resulting
in a greater tendency for reduced visibility due to blowing snow.

..Dean.. 02/23/2019

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


LAT...LON   41669637 43019591 43879552 44499424 44619302 44329224
            43819214 43319242 42629283 41949356 41489425 41259476
            41169521 41089563 41169618 41669637 

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SPC MD 128

MD 0128 Image

Mesoscale Discussion 0128
NWS Storm Prediction Center Norman OK
0501 PM CST Sat Feb 23 2019

Areas affected...far eastern MS into west-central and northwest AL
and south-central TN

Concerning...Tornado Watch 5...6...

Valid 232301Z - 240100Z

The severe weather threat for Tornado Watch 5, 6 continues.

SUMMARY...Corridor of greatest tornado potential the next few hours
will extend from far east-central MS into northwest/west-central AL
and far south-central TN.

DISCUSSION...Radar trends over the last 30 minutes or so have
indicated some strengthening in mid and low level storm rotation
both in semi-discrete convection to the northwest of Meridian MS and
further north associated with bowing line segment in Monroe County
MS. Additional semi-discrete storms moving into far south-central TN
also continue to show signs of rotation. Overall, storms appear to
be struggling due to a weakness in storm relative flow in the low to
mid levels. Additionally, stronger forcing for ascent remains well
west/northwest of the region and height falls have generally been
rather weak. All of these factors have impacted organization and
longevity of intense convection. 

Convection currently moving out of eastern MS into western AL and
south-central TN will encounter the best environment of the day,
with regional VWP data indicating increased flow through the lowest
3km over over the last 30-60 min. Weak backed low level flow has
also been noted in this narrow corridor as well. This should help to
maximize low level shear in axis of greatest heating and
instability. As such, the greatest severe threat, and tornado
potential, will exit the next few hours, mainly across west-central
into northwest AL and adjacent south-central TN.  In fact, recent
LSR from MEM confirmed a tornado had been sighted in Alcorn County.

..Leitman.. 02/23/2019

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


LAT...LON   33198866 34158835 35378802 35618778 35668748 35578708
            35358686 34768679 33238704 32818728 32618765 32558832
            32668864 32808881 33198866 

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SPC MD 125

MD 0125 Image

Mesoscale Discussion 0125
NWS Storm Prediction Center Norman OK
0152 PM CST Sat Feb 23 2019

Areas affected...Southeastern Nebraska

Concerning...Heavy snow 

Valid 231952Z - 240045Z

SUMMARY...Heavy snow rates of 1-2 inches/hour are possible in
portions of southeastern Nebraska this afternoon/early evening. Snow
rates should generally taper off by 6-7 pm CST. An intensifying
surface pressure gradient is also expected and may yield blizzard
conditions in some areas later tonight.

DISCUSSION...A band of heavy snow has developed along a line from
Hastings to York in response to strong mid- and upper-level ascent
from a vigorous shortwave trough now over western Kansas. This
ascent should continue to progress to the northeast through the rest
of the afternoon, coincident with saturated DGZs in RAP forecast
soundings. Heavy snow rates of 1 inch/hour, with some areas locally
higher, will be possible through about 6-7 pm CST. A deepening
surface cyclone now in south-central Kansas will also move off to
the northeast this evening. As this occurs, a strengthening surface
pressure gradient may yield blizzard conditions even as heavier snow
rates wane.

..Wendt.. 02/23/2019

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


LAT...LON   40729883 41219832 41589747 41849687 41909639 41779621
            41069628 40519686 40189712 40059775 40089830 40179865
            40419889 40729883 

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