SPC MD 1681

MD 1681 CONCERNING TORNADO WATCH 490…491… FOR CENTRAL NE AND NORTH-CENTRAL KS

MD 1681 Image


Mesoscale Discussion 1681
NWS Storm Prediction Center Norman OK
0814 PM CDT Sun Oct 01 2017

Areas affected...central NE and north-central KS

Concerning...Tornado Watch 490...491...

Valid 020114Z - 020315Z

The severe weather threat for Tornado Watch 490, 491 continues.

SUMMARY...Scattered thunderstorms continue to develop and move into
portions of central NE and north-central KS, posing a threat for
large hail. Although the threat for tornadoes is beginning to
decrease, tornado and severe thunderstorm watches remain in effect
across the region.

DISCUSSION...Storms across central NE have begun to grow upscale
into a linear system that should continue to move eastward for the
next few hours.  These storms will continue to pose a threat for
damaging winds and some isolated hail potential where the
environment out ahead remains marginally favorable, with MLCAPE
values remaining above 1000 J/kg.  Farther south across
north-central KS, an isolated supercell continues to move
east-northeastward, with large hail reported. The threat for a
tornado remains possible with this storm as low-level shear should
continue to strengthen over the next few hours as evident in the
Hastings VWP. However, increasing convective inhibition should lead
to the storm's demise.

..Karstens/Thompson.. 10/02/2017

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

ATTN...WFO...OAX...TOP...GID...LBF...GLD...

LAT...LON   39229914 39369992 39670070 40210115 40990102 41640002
            42079944 42489883 42609793 42369745 40609733 39639801
            39229914 

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SPC MD 1651

MD 1651 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR CENTRAL THROUGH NORTHEAST KANSAS INTO EXTREME NORTHWEST MISSOURI

MD 1651 Image


Mesoscale Discussion 1651
NWS Storm Prediction Center Norman OK
0732 PM CDT Sat Sep 16 2017

Areas affected...central through northeast Kansas into extreme
northwest Missouri

Concerning...Severe potential...Watch unlikely 

Valid 170032Z - 170230Z

Probability of Watch Issuance...20 percent

SUMMARY...Storms will pose a modest threat for isolated strong to
damaging wind gusts and hail through 02 or 03Z. A WW will probably
not be needed due to the expected limited duration of the threat.

DISCUSSION...Early this evening isolated storms are in the process
of developing along a southeast-advancing cold front that extends
from extreme northwest MO into south-central KS. Topeka 00Z RAOB
sampled the pre-frontal warm sector with moderate (2000 J/kg)
MLCAPE, modest (6.5-7 C/km) mid-level lapse rates and 30 kt surface
to 6 km shear. This environment will support primarily multicell
storms capable of a few downburst winds and some hail next couple
hours. However, increasing convective inhibition associated with a
stabilizing boundary layer suggests these storms will probably begin
a weakening trend by 02Z.

..Dial/Thompson.. 09/17/2017

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

ATTN...WFO...EAX...OAX...TOP...ICT...

LAT...LON   38219813 39449673 40459568 40319506 39579539 38779606
            37979741 38219813 

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SPC MD 1650

MD 1650 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR PORTIONS OF EASTERN KS…WESTERN MO…NORTHEAST OK

MD 1650 Image


Mesoscale Discussion 1650
NWS Storm Prediction Center Norman OK
0355 PM CDT Sat Sep 16 2017

Areas affected...Portions of eastern KS...western MO...northeast OK

Concerning...Severe potential...Watch unlikely 

Valid 162055Z - 162330Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated damaging wind gusts could accompany small
convective clusters into the early evening hours -- east of recently
issued Mesoscale Discussion 1649. Watch issuance is unlikely for
this eastern regime.

DISCUSSION...Persistent elevated convection within a band of
isentropic ascent from north-central OK to the lower Missouri Valley
is becoming near-surface based in response to continued diurnal
surface heating. This activity may produce isolated severe wind
gusts within a fairly narrow spatial window -- the eastern extent of
which is marked by drier/more stable air emanating from an
anticyclone farther east. Nevertheless, 1000-2000 J/kg of MLCAPE
with upwards of around 1000 J/kg of DCAPE may support a few bouts of
intense convection with isolated severe wind gusts. Relatively weak
deep shear/ascent will mitigate the overall severe risk, as this
activity tracks eastward/northeastward into early evening.

..Cohen/Guyer.. 09/16/2017

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

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

LAT...LON   36609626 37869544 39199441 38809383 37119440 36469558
            36609626 

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SPC MD 1649

MD 1649 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR PORTIONS OF CENTRAL AND EASTERN KS

MD 1649 Image


Mesoscale Discussion 1649
NWS Storm Prediction Center Norman OK
0347 PM CDT Sat Sep 16 2017

Areas affected...Portions of central and eastern KS

Concerning...Severe potential...Watch possible 

Valid 162047Z - 162315Z

Probability of Watch Issuance...40 percent

SUMMARY...A risk for severe thunderstorms may increase across parts
of central and eastern KS through the late afternoon hours and
continue into the evening. There is some possibility that Severe
Thunderstorm Watch issuance could become necessary during the next
few hours.

DISCUSSION...Visible satellite imagery indicates a shallow, dense,
swelling field of boundary-layer cumulus within the general apex
region of a pre-frontal thermal ridge permeating the western flank
of Gulf return moisture -- i.e. from Stafford and Rice Counties to
Ottawa County. The front enters northeast KS near Nemaha County and
extends southwestward, and mesoscale ascent is being bolstered near
a diffuse triple point in proximity to Comanche County. Deeper
convection may initiate from these zones of ascent in the 2130-2300Z
time frame -- initially being delayed by ample antecedent capping
associated within a moist-boundary-layer-overlying EML. Steep lapse
rates of 8.5-9 C/km in the mid levels, accompanying the EML, are
supporting 1500-2500 J/kg of MLCAPE in the warm/moist air mass. This
may yield a few robust updrafts, probably following the repeated
development and decay shallow convective plumes amidst only modest
frontal ascent.

A few sustained convective elements should be more likely by early
evening, with 25-30 kt of effective shear supporting small
forward-propagating clusters with isolated to widely scattered
severe wind/hail. This activity will spread eastward/northeastward,
reaching a corridor from Topeka and Lawrence toward Wichita by
evening. This activity will eventually ingest convectively processed
air from ongoing convection from the KC area to northeast OK. The
anticipated severe storm coverage is presently questionable with
stronger deep shear/ascent lagging behind the surface front, though
environmental and convective trends will be monitored for possible
Severe Thunderstorm Watch issuance.

..Cohen/Guyer.. 09/16/2017

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

ATTN...WFO...EAX...TOP...ICT...

LAT...LON   38219826 39149754 39579681 39789588 39399539 37639672
            37309790 37469838 38219826 

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SPC MD 1597

MD 1597 CONCERNING SEVERE POTENTIAL…WATCH UNLIKELY FOR SOUTHERN LOUISIANA

MD 1597 Image


Mesoscale Discussion 1597
NWS Storm Prediction Center Norman OK
0209 PM CDT Tue Aug 29 2017

Areas affected...Southern Louisiana

Concerning...Severe potential...Watch unlikely 

Valid 291909Z - 292145Z

Probability of Watch Issuance...20 percent

SUMMARY...A sporadic storm or two may briefly become severe with
wind or brief tornado threat through late afternoon.

DISCUSSION...Visible satellite imagery and surface observations show
heating across far southern LA, along and south of an east-west
oriented stationary front. South of this front, a tropical air mass
exists with dewpoints in the mid to upper 70s contributing to around
1000 J/kg MLCAPE.

Scattered showers and storms are generally forming near the front as
warm air streams northward. Recently, there have been indications of
better low-level buoyancy which is helping a few cells to exhibit
weak low-level rotation, and higher echo tops in general. The
strongest storms are most likely near the boundary where lift and
shear are maximized and supportive of a supercell. An isolated storm
or two may produce a brief/weak tornado and/or strong wind gust in
association with mesocylonic rotation.

..Jewell/Grams.. 08/29/2017

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

ATTN...WFO...LIX...LCH...

LAT...LON   29649333 29769364 30099375 30319333 30479237 30339136
            30189041 29968977 29628928 29258902 28948904 28868950
            28989068 29399194 29509267 29649333 

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SPC MD 1595

MD 1595 CONCERNING TORNADO WATCH 474… FOR FAR SOUTHEAST TX…COASTAL LA

MD 1595 Image


Mesoscale Discussion 1595
NWS Storm Prediction Center Norman OK
1132 PM CDT Mon Aug 28 2017

Areas affected...Far Southeast TX...Coastal LA

Concerning...Tornado Watch 474...

Valid 290432Z - 290630Z

The severe weather threat for Tornado Watch 474 continues.

SUMMARY...Tornado Watch 474 will be allowed to expire at 05Z and a
replacement Watch is not anticipated.

DISCUSSION...Banded structure noted over the past several hours has
waned with a much more cellular structure to much of the convection
associated with Tropical Storm Harvey. The center of Harvey appears
to have shifted slightly north-northeastward. Some strengthening may
also be occurring. The buoy to the southwest of the center (KBQX)
recently reported a gust to 49 kt. This modest increase in winds is
likely contributing to increased WAA and the cooling of cloud tops
within the deformation band over southeast TX and within the
cellular convection off the LA coast. Some small northward movement
of the front off the coast has also been noted. However, the front
currently remains offshore and consensus amongst the guidance is for
the front to remain offshore until the system begins moving
northeastward a bit quicker late Tuesday morning.

Given these expectations, observational trends over the past hour,
and coordination with the WFOs LCH and LIX, Tornado Watch 474 will
be allowed to expire at 05Z. A replacement watch is not anticipated
at this time. Convective trends will be monitored closely throughout
the night for signs of increased tornado potential.

..Mosier.. 08/29/2017

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

ATTN...WFO...LIX...LCH...

LAT...LON   30329421 30608971 29018969 28749421 30329421 

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SPC MD 1581

MD 1581 CONCERNING TORNADO WATCH 468… FOR UPPER TX COAST…FAR SOUTHWEST LA

MD 1581 Image


Mesoscale Discussion 1581
NWS Storm Prediction Center Norman OK
0937 PM CDT Sat Aug 26 2017

Areas affected...Upper TX Coast...Far Southwest LA

Concerning...Tornado Watch 468...

Valid 270237Z - 270430Z

The severe weather threat for Tornado Watch 468 continues.

SUMMARY...Enhanced tornado threat from League City to Brenham
appears to be waning. Even so, the threat for tornadoes will persist
throughout the night, particularly if another convective band
develops.

DISCUSSION...Convective band associated with Tropical Storm Harvey
has intensified over the past two hours with recent GOES-16 clean IR
window sampling cloud tops around -80 deg C and recent radar imagery
sampling 40 dBZ on the 9km CAPPI. This intensification occurred
within an area of greater daytime heating, resulting in slightly
stronger instability and low-level lapse rates. Easterly motion of
this band has slowed a bit compared to earlier this evening but
gradual eastward progress is still expected over the next several
hour. Cells within this band will continue to move northward or
north-northeastward at around 20-30 kt.

The gradual eastward progression of this band will take it into an
environment characterized by less surface convergence and weaker
low-level (i.e. 850 mb) flow, which results in less storm-relative
helicity. Consequently, the tornado threat posed by this band
appears to be lessening with time. However, additional banding is
possible and the tornado threat will persist throughout the night
across much of the upper TX coast. More cellular development farther
east could also pose an isolated and brief tornado threat.

..Mosier.. 08/27/2017

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

ATTN...WFO...LCH...HGX...CRP...EWX...

LAT...LON   29319663 30259638 30949471 31019386 30359344 29669326
            29479439 28899531 28559633 29319663 

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SPC MD 1571

MD 1571 CONCERNING TORNADO WATCH 465… FOR UPPER TEXAS COAST

MD 1571 Image


Mesoscale Discussion 1571
NWS Storm Prediction Center Norman OK
0117 AM CDT Sat Aug 26 2017

Areas affected...Upper Texas Coast

Concerning...Tornado Watch 465...

Valid 260617Z - 260645Z

The severe weather threat for Tornado Watch 465 continues.

SUMMARY...The highest potential for tornadic supercells will likely
be within 2 corridors either side of Galveston Bay (Brazoria/Fort
Bend and Chambers Counties) for the next 1-2 hours.  A new tornado
watch will be issued before 0700 UTC.

DISCUSSION...Latest subjective surface mesoanalysis indicates the 80
degree F isotherm encompasses Brazoria county northeast into
Chambers county.  The northwest area of a plume of 78 degree F
dewpoints protrudes northwest from the northwest Gulf of Mexico into
the immediate coastal area of Brazoria county.  The latest RAP
forecast sounding appears to be representative of the surface and
around 1400 J/kg MLCAPE is noted.  When inputting storm motion (135
degrees at 35-kt), the KHGX VAD indicates around 200 m2/s2 0-1 km
SRH.  With robust updrafts implied by the convective structures
(echo tops 35-40k ft), the environment will continue to be favorable
for low-level mesocyclones and a tornado risk over the next 1-2
hours.

..Smith.. 08/26/2017

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

ATTN...WFO...LCH...HGX...

LAT...LON   28929522 29379547 29869426 29459397 28929522 

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SPC MD 1546

MD 1546 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR PORTIONS OF NORTHEASTERN KS INTO NORTHERN/CENTRAL MO

MD 1546 Image


Mesoscale Discussion 1546
NWS Storm Prediction Center Norman OK
0636 PM CDT Mon Aug 21 2017

Areas affected...Portions of northeastern KS into northern/central
MO

Concerning...Severe potential...Watch possible 

Valid 212336Z - 220130Z

Probability of Watch Issuance...40 percent

SUMMARY...An isolated severe threat, with large hail, damaging
winds, and perhaps a tornado or two, may be realized over the next
several hours. While a watch is not immediately imminent, convective
trends will be closely monitored for signs of increasing severe
potential which may increase watch issuance probabilities.

DISCUSSION...23Z surface observations and visible satellite imagery
show an outflow boundary from earlier convection draped generally
east-west across northeastern KS into parts of northern/central MO.
The airmass along and south of this boundary has become strongly
unstable owing to strong diurnal heating and a very moist low-level
airmass, with 23Z RAP Mesoanalysis depicting generally 2000-3000
J/kg of MLCAPE across this region. Although stronger mid-level winds
remain mostly displaced to the north of the surface boundary, there
is enough veering/strengthening of the wind field through 6-7 km AGL
to support 30 to locally 40 kt of effective bulk shear. This should
be sufficient to support multicell to marginal supercell structures,
with an isolated large hail/damaging wind threat. A tornado or two
may also not be out of the question with any supercell given locally
backed 0-1 km AGL winds near the outflow boundary enhancing
effective SRH. 

Convective coverage has recently increased in northeastern KS,
probably related to large-scale ascent associated with a weak
impulse moving eastward across central NE/KS. There may be some
potential for one or more small clusters of surface-based
thunderstorms to congeal along the surface boundary and move
east-southeastward this evening as a southwesterly low-level jet
strengthens across this region. While not immediately likely, radar
trends will closely monitored for possible watch issuance.

..Gleason/Goss.. 08/21/2017

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

ATTN...WFO...LSX...SGF...EAX...TOP...

LAT...LON   39949634 39889480 39289188 38249193 38229340 38289517
            38539634 39219691 39949634 

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