SPC MD 119

MD 0119 CONCERNING FREEZING RAIN FOR PORTIONS OF THE MID-ATLANTIC INTO CENTRAL VIRGINIA AND NORTHERN NORTH CAROLINA

MD 0119 Image


Mesoscale Discussion 0119
NWS Storm Prediction Center Norman OK
0923 AM CST Thu Feb 18 2021

Areas affected...portions of the mid-Atlantic into central Virginia
and northern North Carolina

Concerning...Freezing rain 

Valid 181523Z - 181830Z

SUMMARY...Sleet and freezing rain continues from the mid-Atlantic
southward into northern North Carolina. The precipitation will
gradually come to an end from west to east through the morning and
early afternoon.

DISCUSSION...Persistent cold air damming in the lee of the
Appalachians has maintained upper 20s to low 30s temperatures as far
south as northern North Carolina. Surface observations in this area
have shown ice accretion as high as 0.1" per hour recently. The
greatest freezing rain accumulation has been across central and
southern Virginia where temperatures remain in the upper 20s to low
30s and precipitation is mostly falling as freezing rain. Farther
north, temperatures are cold enough at the top of the boundary layer
(as seen on IAD 12Z RAOB) to support mostly sleet. Isentropic ascent
will shift northeastward by early afternoon which should bring an
end to precipitation across much of this region by 19-20Z.

..Bentley.. 02/18/2021

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

ATTN...WFO...PHI...AKQ...LWX...RAH...RNK...GSP...

LAT...LON   35458016 35658059 36308008 37187919 37817878 38017871
            38937784 39717695 39717582 39607502 39337447 39197442
            38887455 38787508 38787552 38507580 38277584 37717674
            37347691 36487713 36127789 36017852 35757924 35497976
            35458016 

Read more

from SPC Mesoscale Discussions https://bit.ly/3asGnMt

SPC MD 50

MD 0050 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR NORTH FL

MD 0050 Image


Mesoscale Discussion 0050
NWS Storm Prediction Center Norman OK
0912 PM CST Sun Jan 31 2021

Areas affected...north FL

Concerning...Severe potential...Watch unlikely 

Valid 010312Z - 010515Z

Probability of Watch Issuance...20 percent

SUMMARY...An isolated risk for locally damaging winds may develop
with a line segment as it moves across north FL through 1230am EST.

DISCUSSION...Radar mosaic imagery as of 10pm EST shows a line
segment moving east from the eastern FL Panhandle into the northern
part of the FL Peninsula.  Surface analysis indicates temperatures
will likely hold steady in the upper 60s F with dewpoints in the
lower 60s F ahead of the line segment.  Recent radar trends have
shown a maintenance of higher echo tops as the band of storms
gradually organizes.  The 00z Tallahassee and Jacksonville raobs
showed a deep moist layer from the surface to 700 mb and a weak
inversion was noted above the moist layer around 700 mb per the
Jacksonville raob.  Lapse rates within the lowest 3 km will remain
modest with 500 J/kg MLCAPE objectively analyzed over north FL.  It
is possible a slow but slight intensification of the line segment
will occur over the next 1-2 hours as an upper vorticity maxima over
the central Gulf Coast approaches the region.  It is unclear whether
a threat for damaging gusts will develop but the environment will
conditionally support a risk dependent on storm-scale processes. 
The overall severe risk appears too isolated/marginal to warrant a
severe thunderstorm watch.

..Smith/Guyer.. 02/01/2021

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

ATTN...WFO...JAX...TAE...

LAT...LON   30358289 30718167 30008132 29658184 29798308 30358289 

Read more

from SPC Mesoscale Discussions https://bit.ly/3ra1Nn2

SPC MD 39

MD 0039 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR PORTIONS OF THE FL PANHANDLE INTO SOUTHERN GA

MD 0039 Image


Mesoscale Discussion 0039
NWS Storm Prediction Center Norman OK
1016 AM CST Wed Jan 27 2021

Areas affected...Portions of the FL Panhandle into southern GA

Concerning...Severe potential...Watch unlikely 

Valid 271616Z - 271815Z

Probability of Watch Issuance...20 percent

SUMMARY...The threat for isolated damaging wind and perhaps a brief
tornado will continue late this morning and potentially into this
afternoon. Watch issuance is unlikely.

DISCUSSION...At 16Z, a band of convection is ongoing from
south-central GA into the FL Panhandle and northern Gulf of Mexico.
The southern portion of this band has intensified over the last
hour, as indicated cooling cloud tops noted in IR imagery and a
recent increase in lightning activity.  The primary large-scale
ascent remains displaced well to the northwest across the mid-MS
Valley in association with a shortwave midlevel trough, but weak
low-level warm advection will continue to focus convection near and
south of a weak surface boundary across northern FL/far southern GA.
While low-level flow is relatively weak and veered along/south of
the boundary, effective shear of 40-50 kt will continue to support
at least transient organization with the strongest storms, with a
primary threat of isolated damaging wind gusts, and perhaps a brief
tornado. 

The main limiting factor for the severe threat will continue to be
weak instability. The greatest relative threat may in the next 1-2
hours over the FL Panhandle, where MLCAPE is as high as 500 J/kg per
recent mesoanalyses. Widespread cloudiness downstream into the
northern FL Peninsula and far southern GA will continue to limit
destabilization, and the longevity of the severe threat into this
afternoon remains uncertain. As a result, watch issuance remains
unlikely.

..Dean/Hart.. 01/27/2021

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

ATTN...WFO...JAX...TAE...

LAT...LON   30058560 30718462 31118392 31258296 31178271 30848254
            30508300 30088385 29878433 29618490 29708538 29918553
            30058560 

Read more

from SPC Mesoscale Discussions https://bit.ly/3acxdCz

SPC MD 35

MD 0035 CONCERNING TORNADO WATCH 3… FOR CENTRAL MISSISSIPPI…NORTH-CENTRAL ALABAMA…EXTREME NORTHWEST GEORGIA

MD 0035 Image


Mesoscale Discussion 0035
NWS Storm Prediction Center Norman OK
1140 PM CST Mon Jan 25 2021

Areas affected...Central Mississippi...North-Central
Alabama...Extreme Northwest Georgia

Concerning...Tornado Watch 3...

Valid 260540Z - 260745Z

The severe weather threat for Tornado Watch 3 continues.

SUMMARY...Severe threat will focus along a corridor from central MS
to extreme northwest GA over the next few hours. The primary risk
will be locally damaging winds along with the threat for a tornado
or two.

DISCUSSION...While large-scale forcing is focused well north of the
central Gulf States, latest satellite imagery suggests deep
convection has intensified over the last hour or so. Cloud-top
evacuation has increased along with lightning flash rates,
indicative of strengthening updrafts. It's not entirely clear why
this activity has increased, but current trends suggest the greatest
focus for the next few hours will concentrate from central MS,
northeast into northwest GA. Supercells will continue to be a
threat, and at times a few of these may exhibit tornadic signatures.
One particular tornadic supercell that passed just north of BHM has
translated into St. Clair County where it has weakened a bit. This
type of updraft/meso cycling can be expected along the
aforementioned corridor for at least the next few hours.

..Darrow.. 01/26/2021

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

ATTN...WFO...FFC...BMX...HUN...JAN...

LAT...LON   32119019 33018887 33968719 34118521 33448508 33078663
            32138923 32119019 

Read more

from SPC Mesoscale Discussions https://bit.ly/3pe5aZH

SPC MD 30

MD 0030 CONCERNING HEAVY SNOW FOR NORTH-CENTRAL/NORTHEAST KS…SOUTHEAST/EAST-CENTRAL NE…SOUTHWEST/SOUTH-CENTRAL IA…FAR NORTHWEST MO

MD 0030 Image


Mesoscale Discussion 0030
NWS Storm Prediction Center Norman OK
1041 AM CST Mon Jan 25 2021

Areas affected...North-Central/Northeast KS...Southeast/East-Central
NE...Southwest/South-Central IA...Far Northwest MO

Concerning...Heavy snow 

Valid 251641Z - 252245Z

SUMMARY...Ongoing heavy snow across southeastern NE and
north-central/far northeast KS is expected to continue for next
several hours. Additionally, gradual eastward expansion of this
heavy snow into southwest IA and far northwest MO is anticipated.

DISCUSSION...Recent surface observations show numerous locations
across southeast NE and adjacent north-central KS reporting moderate
to heavy snow. Satellite and radar imagery show the dry slot is
currently moving through central KS, suggesting much of southeast NE
will remain within the band of heavy snow for at least the next
several hours. Additionally, with the shortwave trough approaching
the region, lift will likely intensify, resulting in increased
snowfall rates and the potential for up to 2" per hour (particularly
across far southeast NE). 

As the overall system moves northeastward, the area of heavy snow is
expected to do likewise, bringing snowfall rates over 1" per hour in
southwest/south-central IA and far northwest MO during the next
several hours. Once established, these high snowfall rates are
expected to last for 3+ hours.

..Mosier.. 01/25/2021

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

ATTN...WFO...DMX...EAX...OAX...TOP...ICT...GID...DDC...GLD...

LAT...LON   40759933 41589813 42089667 42219426 41979312 41359273
            40409310 39999373 39669519 39359650 39129769 39119913
            39450003 40759933 

Read more

from SPC Mesoscale Discussions https://bit.ly/3iLhH4f

SPC MD 28

MD 0028 CONCERNING HEAVY SNOW FOR PORTIONS OF KS AND SOUTHERN NE

MD 0028 Image


Mesoscale Discussion 0028
NWS Storm Prediction Center Norman OK
0458 AM CST Mon Jan 25 2021

Areas affected...Portions of KS and southern NE

Concerning...Heavy snow 

Valid 251058Z - 251700Z

SUMMARY...Heavy snow, with rates of 1-2 inches per hour, will likely
develop northeastward across Kansas and southern Nebraska this
morning.

DISCUSSION...Strong forcing for ascent and frontogenetic lift in the
low levels, associated with a northeastward-ejecting shortwave
trough, will aid in the development of a heavy snow band across
parts of KS into southern NE this morning. An initial mix of wintry
precipitation across parts of southwestern into central KS is
expected to quickly transition to snow as low/mid-level temperatures
cool with the approaching shortwave trough. Pronounced lift through
the saturated dendritic growth zone will likely favor heavy snow
with rates of at least 1 inch per hour for several hours in a
southwest to northeast oriented band across KS. Higher rates,
perhaps up to 2 inches per hour, appear possible on a localized
basis. This heavy snow band should shift into parts of southern NE
by mid to late morning. A very narrow corridor of freezing
rain/sleet may occur on the southeastern fringe of the band, where a
modest low-level warm nose should remain.

..Gleason.. 01/25/2021

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

ATTN...WFO...OAX...TOP...ICT...GID...DDC...GLD...

LAT...LON   37660004 37430072 38230133 39080121 39970021 40839872
            41169726 40999629 40509581 40059572 39659589 39149680
            37660004 

Read more

from SPC Mesoscale Discussions https://bit.ly/3c3hc4q

SPC MD 6

MD 0006 CONCERNING FREEZING RAIN FOR EASTERN KS…CENTRAL/NORTHERN MO…WEST-CENTRAL IL

MD 0006 Image


Mesoscale Discussion 0006
NWS Storm Prediction Center Norman OK
0233 AM CST Fri Jan 01 2021

Areas affected...eastern KS...central/northern MO...west-central IL

Concerning...Freezing rain 

Valid 010833Z - 011330Z

SUMMARY...Moderate to heavy freezing rain is expected to shift
northward across eastern KS into central/northern MO and
west-central IL through the early morning hours.

DISCUSSION...Moderate to heavy freezing rain has been noted recently
across southeast KS toward the I-44 corridor in southwest and
central MO. Freezing rain rates have been as high as 0.05 in/hr in
these locations. A more pronounced/stronger deformation region has
developed northward toward the I-70 corridor from eastern KS into
central MO as the upper low continues to shift northward from north
Texas into southern OK, and is evident in water vapor loops over the
past hour. As midlevel moistening continues, freezing rain will
develop northward and increase in intensity through early morning.
Forecast soundings suggest precipitation type should predominantly
be freezing rain. However, some sleet or snow could mix in at times
as modest midlevel cooling occurs on the back side of the mid/upper
low, resulting in a deepening isothermal layer around 900-750 mb.
Once freezing rain begins, rates greater than 0.05 inches per 3
hours are expected for several hours.

..Leitman.. 01/01/2021

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

ATTN...WFO...ILX...LSX...DVN...SGF...EAX...TOP...ICT...

LAT...LON   38299632 38719617 39179535 39379493 39859363 40269171
            40329089 40209034 39958996 39638990 38829040 38279114
            37739213 37269334 37159455 37329560 37629611 37989626
            38299632 

Read more

from SPC Mesoscale Discussions https://bit.ly/3hzfAAf

SPC MD 1896

MD 1896 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR FAR EASTERN SOUTH CAROLINA INTO SOUTHERN NORTH CAROLINA

MD 1896 Image


Mesoscale Discussion 1896
NWS Storm Prediction Center Norman OK
0226 PM CST Thu Dec 31 2020

Areas affected...far eastern South Carolina into southern North
Carolina

Concerning...Severe potential...Watch unlikely 

Valid 312026Z - 312230Z

Probability of Watch Issuance...5 percent

SUMMARY...Recent convective development in eastern South Carolina
may pose an isolated wind/tornado risk this afternoon.  A WW
issuance is not anticipated due to the isolated nature of the
threat.

DISCUSSION...A small cluster of lightning-producing convection has
evolved near Horry County, SC over the past hour or so, with modest
but increasing organization noted on local radar.  The increase in
intensity is likely aided by an advancing, low-amplitude mid-level
wave evident on water vapor imagery and objective analysis.  The
storms are in a marginally unstable environment (with over 500 J/kg
MUCAPE in the pre-storm environment).  However, the presence of
strong updrafts (and nearly 40kft echo tops) suggests that the
storms may be taking advantage of the 40-50 kts of environmental
deep shear, fostering organization.  Additionally, the presence of
150-200 m2/s2 0-3km SRH may foster rotation in a few of the storms,
enhancing any localized risk of a damaging wind gust or perhaps a
tornado.  The overall risk should be localized and isolated given
the marginal nature of the instability, however, precluding the need
for a WW.

..Cook/Grams.. 12/31/2020

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

ATTN...WFO...MHX...RAH...ILM...

LAT...LON   34407946 34787873 34977786 34947720 34617697 33757764
            33297857 33267927 33777969 34177955 34407946 

Read more

from SPC Mesoscale Discussions https://bit.ly/3o3upgR

SPC MD 1884

MD 1884 CONCERNING WINTER MIXED PRECIPITATION FOR NORTHEAST KS…EASTERN NE…SOUTHWEST/CENTRAL IA…NORTHERN MO

MD 1884 Image


Mesoscale Discussion 1884
NWS Storm Prediction Center Norman OK
1002 AM CST Tue Dec 29 2020

Areas affected...Northeast KS...Eastern NE...Southwest/central
IA...Northern MO

Concerning...Winter mixed precipitation 

Valid 291602Z - 292100Z

SUMMARY...Moderate to occasionally heavy winter precipitation will
continue into this afternoon. The snow/freezing rain and freezing
rain/rain lines should gradually shift northward with time, with
some sleet possible within the snow/freezing rain transition zone.

DISCUSSION...At 16Z, a broad plume of winter precipitation is
ongoing from central KS into portions of IA/NE and northern MO, with
embedded convective elements noted across KS and moving into
southeast NE/southwest IA/northwest MO. This precipitation will be
sustained into this afternoon, as strong low-level warm advection
maintains ascent in advance of a complex mid/upper-level trough
moving into the central/northern Plains. The warm advection will
also result in a northward transition of the snow/freezing rain and
freezing rain/rain lines with time. Some sleet will be possible
within the snow/freezing rain transition zone, though surface
observations and forecast soundings indicate that freezing rain and
snow will remain the predominant precip types for at least the
remainder of the morning. 

While widespread and occasionally moderate/heavy, precipitation has
thus far been somewhat disorganized, with heavier rates being
relatively transient at any given location. However, heavier
precipitation over KS is expected to spread northeastward at a
faster rate than the precip type transition zones, resulting in more
widespread snow rates of 1+ inch per hour across far eastern NE into
western/central IA by early afternoon, and freezing rain rates of
0.05+ inches/hour from southeast NE/far northeast KS into northern
MO. Increasing frontogenesis within the 900-700 mb layer will
support the potential for more organized banding and even greater
snowfall rates by mid afternoon, primarily across portions of
southern/central IA.

..Dean.. 12/29/2020

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

ATTN...WFO...LSX...DVN...DMX...EAX...OAX...TOP...GID...

LAT...LON   41009151 40089230 39149383 38629549 39019681 39389772
            40649732 41559684 42059483 42249371 42239259 41909176
            41009151 

Read more

from SPC Mesoscale Discussions https://bit.ly/3rANlpl

SPC MD 1883

MD 1883 CONCERNING WINTER MIXED PRECIPITATION FOR MUCH OF KS AND FAR NORTHWESTERN OK

MD 1883 Image


Mesoscale Discussion 1883
NWS Storm Prediction Center Norman OK
0400 AM CST Tue Dec 29 2020

Areas affected...Much of KS and far northwestern OK

Concerning...Winter mixed precipitation 

Valid 291000Z - 291600Z

SUMMARY...Freezing rain should occur this morning before gradually
turning to rain from south to north. Freezing rain rates may exceed
0.05 inch per 3 hours. Some snow/sleet may also mix with the
freezing rain, mainly across parts of northern Kansas.

DISCUSSION...A 40-50+ kt southerly low-level jet will continue to
transport moisture northward across the southern/central Plains this
morning. Strong forcing for ascent associated with this low-level
jet has encouraged the development of scattered to numerous showers
across northern OK and much of central/eastern KS. An initially dry
sub-cloud layer across these areas is gradually becoming saturated
as precipitation continues. Evaporative cooling to the surface wet
bulb temperature should result in a period of freezing rain for at
least a few hours this morning across far northwestern OK and much
of KS, where surface air temperatures are or will soon fall below
freezing. The light to moderate and showery precipitation should
support freezing rain rates around 0.05 inch per 3 hours, with
locally higher rates possible with convection that may produce
isolated lightning flashes with very weak elevated instability.
Still, ice accretion may remain limited to elevated surfaces for
most locations due to the marginal surface temperatures. The best
potential for ice accretion appears to be across parts of
north-central into northeastern KS, where surface temperatures
should generally remain below freezing this morning.

Continued robust low-level warm advection is expected to gradually
erode the near-surface sub-freezing layer from south to north across
this region through the morning, as surface winds veer from easterly
to southeasterly. Accordingly, a transition from freezing rain to
rain should occur across far northwestern OK and parts of
southern/central KS by 16Z (10 AM CST). A mix of freezing rain,
sleet, and/or snow also appears possible across mainly northern KS,
where the low-level warm nose will not be as pronounced compared to
locations farther south.

..Gleason.. 12/29/2020

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

ATTN...WFO...EAX...TOP...ICT...OUN...GID...DDC...GLD...AMA...

LAT...LON   37899794 37419871 36699916 36439964 36670051 37430083
            38250072 39129999 39889814 39959681 39879573 39489508
            38759494 38309587 38109708 37899794 

Read more

from SPC Mesoscale Discussions https://bit.ly/2Mh5Qio