SPC MD 1708

MD 1708 CONCERNING SEVERE THUNDERSTORM WATCH 499… FOR NORTHEAST OK…SOUTHEAST KS

MD 1708 Image


Mesoscale Discussion 1708
NWS Storm Prediction Center Norman OK
0651 PM CDT Mon Oct 09 2017

Areas affected...Northeast OK...Southeast KS

Concerning...Severe Thunderstorm Watch 499...

Valid 092351Z - 100115Z

The severe weather threat for Severe Thunderstorm Watch 499
continues.

SUMMARY...Isolated hail will continue to be the primary threat with
storms this evening.

DISCUSSION...Scattered convection is beginning to mature along the
advancing wind shift over northeast OK with lightning now detected
with updrafts over Osage County. Frontal convection may gradually
increase across northeast OK over the next few hours but overall
intensity of this activity may struggle to produce more than
isolated large hail. Latest MRMS data at times exhibits hail
approaching 1" but mostly marginally severe. One reason may be that
large-scale forcing for ascent lags this region considerably. In
addition, the onset of boundary-layer cooling will result in
updrafts becoming increasingly elevated in nature. Even so, some
threat for isolated severe will continue for the next few hours.

..Darrow.. 10/09/2017

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

ATTN...WFO...SGF...EAX...TSA...TOP...ICT...OUN...

LAT...LON   35259672 38109726 38129487 35269441 35259672 

Read more

from SPC Mesoscale Discussions http://bit.ly/2y71A9U

SPC MD 1707

MD 1707 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR PORTIONS OF NORTHERN/CENTRAL TX

MD 1707 Image


Mesoscale Discussion 1707
NWS Storm Prediction Center Norman OK
0454 PM CDT Mon Oct 09 2017

Areas affected...Portions of northern/central TX

Concerning...Severe potential...Watch unlikely 

Valid 092154Z - 100030Z

Probability of Watch Issuance...5 percent

SUMMARY...Isolated to widely scattered thunderstorms should develop
late this afternoon and pose a very isolated risk for damaging winds
and hail into the evening. Watch issuance is not expected.

DISCUSSION...Low-level convergence along a southeastward-moving cold
front will likely provide a sufficient source of lift to initiate
isolated to widely scattered thunderstorms over the next several
hours across parts of northern/central TX. Recent visible satellite
imagery indicates convection is attempting to form along the length
of the front, but is still struggling to reach the LFC as of 2150Z,
possibly due to a weak residual inversion at the top of the boundary
layer present on the 12Z FTW sounding. Regardless, moderately to
locally strong instability has developed this afternoon ahead of the
front owing to strong diurnal heating and a moist low-level airmass.
Stronger mid-level flow lags to the west and northwest the front,
which is limiting effective bulk shear values to no more than 25-30
kt immediately along and just behind the front. This marginal shear
will likely preclude more robust updraft organization even with the
favorable thermodynamic environment. Still, steep low-level lapse
rates may encourage strong to perhaps damaging convective downdraft
winds within any thunderstorms that can form along the front, and
some marginally severe hail could also occur with initially discrete
development. This marginal/isolated severe threat should diminish by
mid-evening with the loss of daytime heating and related
instability.

..Gleason/Hart.. 10/09/2017

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

ATTN...WFO...FWD...EWX...SJT...

LAT...LON   31679922 31979850 32389788 33249723 33659715 33679636
            33619590 33159590 32579597 31409724 30949802 30749898
            31189950 31419952 31679922 

Read more

from SPC Mesoscale Discussions http://bit.ly/2kyGONe

SPC MD 1706

MD 1706 CONCERNING SEVERE POTENTIAL…WATCH LIKELY FOR PORTIONS OF EASTERN OKLAHOMA AND SOUTHEASTERN KANSAS

MD 1706 Image


Mesoscale Discussion 1706
NWS Storm Prediction Center Norman OK
0220 PM CDT Mon Oct 09 2017

Areas affected...Portions of eastern Oklahoma and southeastern
Kansas

Concerning...Severe potential...Watch likely 

Valid 091920Z - 092115Z

Probability of Watch Issuance...95 percent

SUMMARY...Isolated to scattered severe storms are expected to
develop over the next few hours. These storms will persist through
the mid/late evening hours, with an attendant threat of large hail,
damaging winds, and perhaps a tornado or two. Watch issuance is
likely within the next 1-2 hours.

DISCUSSION...Visible satellite this afternoon depicts two areas of
increasing convective potential -- one stretching across
east-central Oklahoma ahead of a cold front and another over
southeast Kansas ahead of a weak surface low. Large-scale mid/upper
ascent likely remains somewhat weak, with the primary shortwave
trough situated over the Four Corners region. However, ongoing
heating, modest warm-air advection ahead of the low, and convergence
along the cold front will likely be sufficient to overcome any
remaining inhibition across the region.

While mid-level lapse rates are not particularly steep (generally 7
C/km or less) across eastern OK and southeast KS, rich
boundary-layer moisture and sufficient heating have yielded around
1000-2000 J/kg of MLCAPE. Meanwhile, increasing 500mb
southwesterlies atop low-level south/southeasterly winds are
offering ample effective shear for updraft organization/rotation. In
turn, more robust cores will be capable of large hail and damaging
winds through this evening. A tornado or two may also be possible
early this evening, considering the backed surface flow across far
southeast KS and eastern OK. However, the advance of the cold front
and loss of favorable surface-based buoyancy with eastward extent
will likely keep the tornado threat rather confined in space/time.
Regardless, watch issuance is likely within the next 1-2 hours.

..Picca/Grams.. 10/09/2017

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

ATTN...WFO...SGF...TSA...TOP...ICT...OUN...

LAT...LON   34989651 35449696 36149708 37089705 37329717 37949676
            38099597 37919542 37289506 36149472 35079498 34759595
            34989651 

Read more

from SPC Mesoscale Discussions http://bit.ly/2yTtDsD

SPC MD 1695

MD 1695 CONCERNING SEVERE THUNDERSTORM WATCH 495… FOR SOUTHEAST NEBRASKA INTO PARTS OF NORTHEAST AND CENTRAL KANSAS

MD 1695 Image


Mesoscale Discussion 1695
NWS Storm Prediction Center Norman OK
0650 PM CDT Fri Oct 06 2017

Areas affected...southeast Nebraska into parts of northeast and
central Kansas

Concerning...Severe Thunderstorm Watch 495...

Valid 062350Z - 070115Z

The severe weather threat for Severe Thunderstorm Watch 495
continues.

SUMMARY...Severe storms over central Kansas will continue to track
east-northeast into the MCD area this evening. Hail and strong wind
gusts will be the main concern with these storms into tonight.

DISCUSSION...Radar trends over the last hour show a transition from
discrete supercell structures over western Kansas into clusters and
bowing line segments as storms track east across central Kansas.
This should result in a diminishing large hail threat into the
nighttime hours. MRMS MESH trends over the last hour seem to support
this notion as values have been decreasing even in semi-discrete
cells. Somewhat poorer lapse rates and instability across northeast
Kansas into southeast Nebraska also are likely contributing to a
downward trend in hail indicators. Regardless, the environment will
continue to support at least a marginal hail threat this evening. As
storms continue to grow upscale into a better organized line,
damaging winds will become the main concern with eastward extent.

..Leitman.. 10/06/2017

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

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

LAT...LON   40729503 37529705 37599890 40699733 40729626 40729503 

Read more

from SPC Mesoscale Discussions http://bit.ly/2z5eVQo

SPC MD 1692

MD 1692 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR PORTIONS OF SOUTHEAST NEBRASKA…SOUTHWEST IOWA…AND FAR NORTH CENTRAL KANSAS

MD 1692 Image


Mesoscale Discussion 1692
NWS Storm Prediction Center Norman OK
0314 PM CDT Fri Oct 06 2017

Areas affected...Portions of southeast Nebraska...southwest
Iowa...and far north central Kansas

Concerning...Severe potential...Watch possible 

Valid 062014Z - 062145Z

Probability of Watch Issuance...60 percent

SUMMARY...Thunderstorms are expected to develop in the next 60-90
minutes in the vicinity of the frontal zone.  Severe hail and brief
gusty winds are the main threat.  A watch may be needed by 21-22z.

DISCUSSION...A mostly stationary frontal zone stretching from
northwest Kansas into west-central Iowa will be the focus for
thunderstorm development in the next 60-90 minutes.  The most likely
area for first initiation will be along the intersection of a weak
surface trough and a differential heating boundary stretching
between Concordia and Russell where GOES-16 1-min imagery shows
cumulus steadily deepening. Shortly after the first CI in
north-central Kansas, thunderstorms are expected to rapidly develop
along the front into southeast Nebraska and southwest Iowa.  

Although extensive cloud cover south of the front has persisted, a
very moist boundary layer and temperatures in the low 70s is still
contributing to MLCAPE values of 500-1000 J/kg over southwest Iowa,
and 1000-1500 J/kg over Nebraska and north-central Kansas. These
values could increase somewhat as a steady northeastward advancement
of the clearing should continue through the period. Deep-layer shear
profiles are favorable for organized storms, including a few line
segments and supercells capable of severe hail and brief severe wind
gusts. While the low clouds have limited the magnitude of the
low-level lapse rates -- and thus the potential for low-level
stretching and a brief tornado -- wind speeds in the 500-1000 m
layer are forecast to increase with time to produce fairly large
low-level hodograph curvature in the unstable air. Based on RAP/HRRR
model soundings, temperatures that warm into the upper 70s to near
80F could produce low-level lapse rates steep enough to increase the
tornado threat.  Otherwise, the severe threat will be mainly severe
hail and brief severe wind gusts with any of the organized storms. 
Given the above expected evolution of storms, a severe weather watch
may be needed in the next hour or two.

..Coniglio/Grams.. 10/06/2017

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

ATTN...WFO...DMX...EAX...FSD...OAX...TOP...ICT...GID...

LAT...LON   41159475 40469559 40209605 40039644 39679700 39439747
            39209795 39129822 39099840 39159851 39349850 39839836
            40329825 40879787 41229730 41569684 41869629 42119576
            42339517 42429455 42209436 41889441 41159475 

Read more

from SPC Mesoscale Discussions http://bit.ly/2z4x80j

SPC MD 1691

MD 1691 CONCERNING SEVERE POTENTIAL…WATCH LIKELY FOR MUCH OF SOUTHWEST INTO CENTRAL KANSAS AND SOUTHEAST COLORADO

MD 1691 Image


Mesoscale Discussion 1691
NWS Storm Prediction Center Norman OK
0255 PM CDT Fri Oct 06 2017

Areas affected...Much of southwest into central Kansas and southeast
Colorado

Concerning...Severe potential...Watch likely 

Valid 061955Z - 062200Z

Probability of Watch Issuance...95 percent

SUMMARY...Severe thunderstorms are likely to form across southwest
Kansas and perhaps extreme southeast Colorado by around 21Z. Very
large hail is likely, with an increasing threat of damaging winds
through evening across central Kansas.

DISCUSSION...Surface observations show southwesterly winds have
increased across the High Plains in response to heating and mixing;
east of a developing cold front across CO and NM, and south of a
stationary front from west-central KS into southeast NE. Increasing
CU fields can now be seen on high-res GOES 16 one-minute imagery
from southeast CO into southwest KS as CIN erodes near the surface
low. Although this area is ahead of the main boundaries, low-level
speed convergence exists on the nose of the steeper low-level lapse
rates which is aiding lift.

The 18Z DDC sounding indicated a capping inversion, with mid 80s
temperatures needed to reduce inhibition to zero. Continued heating
as well as the rapidly approaching shortwave trough should allow for
cells to form ahead of the cold front by late afternoon.

The veered southwesterly winds beneath increasing southwesterlies
aloft are resulting in a long, primarily straight hodograph, with
marginal low-level SRH values. This may temper tornado potential
with expected supercells, with the best chance of a brief tornado
during early development and with storms traveling along the
stationary front. Ample instability and favorably increasing speed
shear aloft will favor very large hail with the initial cells. With
time, activity will merge, with cells possibly bowing northeastward
along the front. Damaging winds are expected, along with the
potential for wind-driven hail.

..Jewell/Grams.. 10/06/2017

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

ATTN...WFO...TOP...ICT...GID...DDC...GLD...PUB...BOU...

LAT...LON   37520329 37950353 38990297 39150249 39130175 39030080
            39060004 39439881 39389809 38949748 38499746 38129795
            37560014 37200216 37250259 37520329 

Read more

from SPC Mesoscale Discussions http://bit.ly/2z36zbH