Storm Prediction Center Forecast

RSS Mesoscale Discussions from Storm Prediction Center

SPC - No watches are valid as of Sun Oct 20 07:09:01 UTC 2019

No watches are valid as of Sun Oct 20 07:09:01 UTC 2019.

SPC MD 2082

MD 2082 Image

Mesoscale Discussion 2082
NWS Storm Prediction Center Norman OK
0117 AM CDT Sun Oct 20 2019

Areas affected...Northeast SC...Southeast NC

Concerning...Severe potential...Watch unlikely 

Valid 200617Z - 200815Z

Probability of Watch Issuance...20 percent

SUMMARY...Threat for a tornado or two will gradually increase
through the overnight.

DISCUSSION...At 06Z, the remnant circulation of Nestor is
approaching southern SC from east-central GA. A warm front extends
northeastward into northeast SC and areas just offshore of coastal
NC. The LTX VWP, which is sampling the wind profile just north of
the warm front, shows an enlarged low-level hodograph, with 0-1 km
SRH in excess of 300 m2/s2. 

Lightning activity has recently increased offshore with cellular
convection near and just north of the warm front. Very limited
surface-based buoyancy has thus far limited the tornado threat, but
gradual airmass modification as the warm front advances slowly
northward will eventually support the potential for a tornado or two
across coastal northeast SC/southeast NC. 

At this time, buoyancy sufficient for a tornado threat is not
expected to advance very far inland, with the greatest potential
expected to remain across coastal regions and offshore, where
cellular convection may at least briefly overlap with the more
favorable tornado environment. Given the relatively limited
magnitude and spatial extent of the threat, watch issuance is
considered unlikely at this time.

..Dean/Edwards.. 10/20/2019

...Please see for graphic product...


LAT...LON   33697932 34287852 34637796 34797754 34397663 33967719
            33787760 33647792 33487852 33447889 33447925 33697932 

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SPC Oct 20, 2019 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0105 AM CDT Sun Oct 20 2019

Valid 201200Z - 211200Z


Severe storms capable of very large hail, a few tornadoes, and
damaging winds are expected over parts of eastern Oklahoma,
northeast Texas and western Arkansas during the evening and through
early Monday morning. Other isolated severe activity is possible
over central Texas and Missouri. Farther east, a severe storm or two
cannot be ruled out over eastern North Carolina during the morning.

An upper trough will amplify as it moves from the Rockies into the
Plains, with substantial height falls. Middle and upper-level winds
will strengthen throughout the period with a leading jet max
becoming better defined overnight from north TX into MO with 500 mb
speeds to 100 kt. In the low levels, 850 mb winds will increase to
50-60 kt ahead of a cold front, extending roughly from eastern KS
into northwest TX at 00Z. Ahead of this front, low-level moisture
will be in the process of surging north, with mid to upper 60s F
dewpoints into north TX by late afternoon. Moisture advection will
increase overnight as a surface low translates northeast across
eastern OK and into MO, leading to rapid destabilization over parts
of OK, AR, and southern MO.

To the east, a weakening shortwave trough and surface low associated
with the remnants of Nestor will enhance shear across the Mid
Atlantic, and may support a severe risk over eastern NC during the

...Northern TX...eastern OK...western Arkansas...
The region will likely be devoid of thunderstorms through late
afternoon as low-level moisture continues to spread north and lapse
rates steepen. By around 00Z, storms are expected to rapidly develop
near the surface trough near central OK, and perhaps into eastern KS
as well where instability will be weaker. Steep lapse rates along
with enlarging hodographs will favor supercells. Effective SRH
increasing to 300-400 m2/s2 over eastern OK and northeast TX during
the evening and deep-layer effective shear over 60 kt will favor
tornadoes and very large hail, assuming cellular storm mode. With
time, CAMs suggest storms merging into an MCS or a series of bows as
forcing become cold-front dominated. Damaging winds are likely, and
will likely spread east into AR.

If the boundary layer destabilizes sufficiently into southern MO,
strong shear will favor QLCS structures along the front with
damaging wind or brief tornado potential. Farther north into eastern
KS and northern MO, elevated instability may prove sufficient for
marginal hail during the evening as elevated moisture advection
interacts with cold temperatures aloft and strong deep-layer shear.

...Eastern NC - early day..
A surface low will move rapidly northeast across eastern NC through
midday, with mid 70s F dewpoints and strong low-level shear along
and east of the track. Warm advection and lift will be most
prominent during the 12-15Z time frame, with widespread rain and a
few thunderstorms ongoing early day. Although the time window of
opportunity is small, the very moist air mass may prove sufficient
for surface based storms near the surface low where SRH would then
become effective to the surface and over 500 m2/s2. If this occurs,
a tornado or damaging wind gust will be possible.

..Jewell/Squitieri.. 10/20/2019

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SPC Oct 20, 2019 0600 UTC Day 2 Convective Outlook

SPC 0600Z Day 2 Outlook
Day 2 Outlook Image
Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1157 PM CDT Sat Oct 19 2019

Valid 211200Z - 221200Z


Severe thunderstorms are possible Monday across the lower
Mississippi Valley, into portions of the lower Ohio Valley and
Southeast, accompanied by a risk for damaging wind gusts and perhaps
a few tornadoes.

Rather amplified neutral to negatively tilted large-scale mid/upper
troughing appears likely to shift east of the Plains through the
Mississippi Valley during this period, as a number of embedded
smaller-scale perturbations progress through the broader cyclonic
flow.  There has been and remains substantive spread among the
various models and their ensembles concerning these smaller-scale
developments.  However, it seems increasingly probable that the most
significant impulse will pivot northeast of the mid/lower Missouri
Valley through the Upper Midwest, accompanied by rapid deepening of
a lower/mid tropospheric cyclone Monday.  The cyclone may gradually
occlude late Monday into Monday night over the Upper Midwest/Great
Lakes region, with the trailing cold front surging toward the
Appalachians and into the northwest Gulf of Mexico by 12Z Tuesday.

...Lower Mississippi/Ohio Valleys and central Gulf coast...
Mid 60s to near 70F surface dewpoints may return northward along the
deepening surface trough axis across southeast Texas through the
Ozark Plateau, and as far north as southeast Missouri by 12Z Monday.
Models suggest that this moisture may initially still be
contributing to mixed-layer CAPE of 500-1000 J/kg, and inflow of
this air may be maintaining vigorous convective development along
the southeastward advancing cold front at the outset of the period,
in the presence of strong deep-layer shear.

Due to weakening lower/mid tropospheric lapse rates within the
moistening portion of the warm sector of the cyclone, coupled with
initially drier air lingering across much of the Southeast into the
Tennessee/Ohio Valleys, boundary-layer destabilization ahead of the
convective line may become increasingly modest to weak with eastward
extent, to the east of the Mississippi Valley.  As a result, there
remains uncertainty concerning how long instability will be able to
maintain convective intensity through the day Monday.

Furthermore, it still appears that there may be a tendency for the
strongest deep-layer mean wind fields to shift north of what remains
of the unstable warm sector early in the period.  Still, south to
southwesterly lower/mid tropospheric flow may initially include
50-70 kt at 850 mb, and 70-90+ kt at 500 mb.  Even with a gradual
weakening of this flow, the environment could remain supportive of
organized severe wind potential (and perhaps a risk for tornadoes)
across much of the lower Mississippi Valley, and perhaps as far
north as the lower Ohio Valley, spreading eastward toward the
southern Appalachians and eastern Gulf Coast states through Monday

Tornado:   5%     - Slight
Wind:     15%     - Slight
Hail:      5%     - Marginal

..Kerr.. 10/20/2019

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SPC Day 1 Fire Weather Outlook

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook Image
Day 1 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0132 AM CDT Sun Oct 20 2019

Valid 201200Z - 211200Z


A deepening upper-level trough will eject into the Plains, with a
belt of 60+ knot mid-level flow overspreading a dry and well-mixed
boundary layer across the Plains states, where a very strong
isallobaric component of westerly surface flow will also be in
place. As such, very windy, dry conditions are expected across the
western portions of the Plains, with wildfire-spread potential being
prevalent. Farther west, a surface high will continue to build into
the Great Basin, fortifying a pressure gradient across southern
California, where dry offshore flow will promote wildfire concerns
across the Transverse Ranges.

...Southern High Plains...
By early afternoon, widespread 20+ mph sustained westerly surface
winds and overlapping 15-20% RH are expected across the Colorado
Front Range, southward into northeast New Mexico and eastward into
southwest Kansas. A critical area has been refined from Day 2 to
reflect the best overlap of critical conditions in model guidance
with very dry finer fuels. An elevated area also delineates where
15-25 mph winds and 15-20% RH will be common, but with slightly
less-receptive fuels. 

...Southern California...
Offshore flow is expected to intensify during the late morning hours
in southern California according to the latest high resolution
guidance. Widespread 25+ mph sustained northeasterly winds will be
common along with 15-20% RH across the Transverse Ranges. A few
spots of briefly stronger winds/lower RH may occur in
terrain-favoring areas. A critical delineation has been maintained
where the greatest confidence exists in 25+ mph sustained winds
being observed.

..Squitieri.. 10/20/2019

...Please see for graphic product...

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SPC Day 2 Fire Weather Outlook

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook Image
Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0207 AM CDT Sun Oct 20 2019

Valid 211200Z - 221200Z


As a large-scale upper-level trough continues to move across the
central US, an upper-level ridge and associated surface high
pressure will begin to dominate the western CONUS during the Day
2/Monday period. As the upper trough departs, a band of 70+ knot
mid-level northwesterly flow will overspread portions of the
southern High Plains, providing upper-level support for very dry,
breezy westerly flow, mainly across central into eastern New Mexico.
Meanwhile, high pressure across the Great Basin will continue to
reinforce a pressure gradient across southern California, where very
dry offshore flow will persist.

...Southern High Plains...
By afternoon, downslope flow/deep mixing of the boundary layer, and
downward transport of the aforementioned very strong mid-level
winds, will encourage widespread 25+ mph sustained westerly surface
winds across portions of central into eastern New Mexico, coinciding
with 15-20% RH. These conditions, along with dry fuels receptive to
fire spread being prevalent, warrant a critical area, with an
elevated delineation in place for areas that may experience slightly
weaker winds.

...Southern California...
Widespread 15-20 mph sustained northeasterly surface winds and RH
dropping to at least 15-20% are expected during the afternoon hours 
across the Transverse Ranges as diurnal heating commences, with an
elevated area in place. While winds might weaken slightly in the
afternoon, there appears to be a window of overlap (based on latest
high-resolution model guidance) for 25+ mph winds, with higher
gusts, to occur across terrain-favoring portions of Santa Barbara,
Ventura, and Los Angeles counties, where a critical area was

..Squitieri.. 10/20/2019

...Please see for graphic product...

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