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Current Mesoscale Discussions

SPC - No watches are valid as of Fri Apr 19 19:01:01 UTC 2024

No watches are valid as of Fri Apr 19 19:01:01 UTC 2024.

SPC MD 494

MD 0494 Image

Mesoscale Discussion 0494
NWS Storm Prediction Center Norman OK
0133 PM CDT Fri Apr 19 2024

Areas affected...portions of the Tennessee Valley into the

Concerning...Severe potential...Watch unlikely 

Valid 191833Z - 192030Z

Probability of Watch Issuance...20 percent

SUMMARY...Thunderstorm development is anticipated in the next couple
of hours across parts of the southern Appalachians. These storms
should gradually intensify through the mid/late afternoon, and may
pose a severe hail/wind threat across parts of far eastern Tennessee
and adjacent portions of Virginia and the Carolinas. The coverage of
strong/severe storms should be sufficiently limited to preclude
watch issuance.

DISCUSSION...A gradually deepening cumulus field has been tracked in
GOES visible/IR imagery and regional radars over the past 60
minutes. Lingering inhibition has precluded deeper convection so
far, but continued daytime heating along with combined forcing for
ascent along an approaching cold front and orographic lift within
the southern Appalachians should foster more robust thunderstorms in
the coming hours. Despite weak low-level winds, 30-40 knot flow
aloft is supporting effective bulk shear values near 30-35 knots,
which should be sufficient for some organization of deeper cells
that may pose a large hail risk (most likely between 0.75 to 1.25
inch in diameter). Additionally, heating of a somewhat dry air mass
downstream across the Carolinas (where temperatures are climbing
into the low 80s under clearing skies) should steepen low-level
lapse rates by late afternoon to around 8 C/km. This may favor
outflow-driven storms with a tendency for upscale growth into
clusters and the potential for strong to severe gusts.

..Moore/Smith.. 04/19/2024

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


LAT...LON   36658012 36187981 35217999 34728071 34498146 34518259
            34618339 34908423 35268452 35668427 36978244 37068172
            36968086 36658012 

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SPC Apr 19, 2024 1630 UTC Day 1 Convective Outlook

SPC 1630Z Day 1 Outlook
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1126 AM CDT Fri Apr 19 2024

Valid 191630Z - 201200Z


Sporadic strong to marginally severe storms are possible over parts
of the Southeast this afternoon into the early evening.

...Southeast this afternoon/evening...
Late morning water-vapor imagery shows a mid-level shortwave trough
moving east across the southern Appalachians.  This feature will
reach the VA/NC coast early tonight.  Farther northwest, a closed
midlevel low will evolve into an open wave as it moves eastward over
the Great Lakes and OH Valley.  An associated surface cold front
will continue to move slowly southeastward from TX to the southern
Appalachians.  Isolated to widely scattered thunderstorms will be
possible with the disturbance over the Carolinas this afternoon. 
Other than the front pushing into portions of AL/GA, little
larger-scale forcing for ascent is expected farther southwest. 
Additional storm development will be associated with the front and
orographic lift along the spine of the Appalachians.  Overall
weak-moderate buoyancy, modest deep-layer shear and steepening
low-level lapse rates will support some potential semi-organized
storms capable of producing isolated wind damage and marginally
severe hail for a few hours this afternoon/evening.

...TX through tonight...
--No change needed to previous forecast discussion--
Weak upslope flow along a slow moving cold front will favor
thunderstorm development over the east slopes of the Sierra Madre
Oriental/Sierra del Burro this afternoon, with the potential for a
couple of supercells.  However, it is not clear that storm motions
will bring the convection across the Rio Grande, and lingering
convective inhibition suggests storms will likely weaken if they
manage to cross the border.  Later tonight in northwest TX, elevated
convection will likely develop atop the frontal surface, in a warm
advection regime downstream from a weak shortwave trough over AZ/NM.
Some small hail may occur given lingering steep midlevel lapse rates
and modest cloud-layer shear, but the potential for severe hail
appears too low to warrant an outlook area.

..Smith/Moore.. 04/19/2024

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SPC Apr 19, 2024 1730 UTC Day 2 Convective Outlook

SPC 1730Z Day 2 Outlook
Day 2 Outlook Image
Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1152 AM CDT Fri Apr 19 2024

Valid 201200Z - 211200Z


Marginally severe storms capable of strong wind gusts and hail will
be possible on Saturday across much of central Texas, and during the
afternoon from southern Alabama across parts of Georgia and into
southern South Carolina.

An upper trough will move east from the Great Lakes into the
Northeast, as the parent upper low deepens over Hudson Bay. Moderate
westerly flow aloft will remain from the central Plains to the East
Coast, with a low-latitude wave moving from AZ/NM across the
southern Plains through Saturday night.

At the surface, high pressure will extend south and eastward across
much of the central and eastern CONUS, with a front from the coastal
Carolinas to the northern Gulf Coast and into southern TX. A moist
air mass will remain south of this boundary in TX, where lift north
of the boundary will lead to increase rain and thunderstorms.

Primarily elevated thunderstorms are likely through much of the day
over parts of central and northern TX, with activity extending east
toward northern MS. This activity will be supported by modest warm
advection just above the cool post-frontal air mass. Instability may
still be substantial, especially just north of the surface front. As
such, a few hail reports will be possible over a relatively large
area, with a conditional risk of strong gusts closer to the front. 

...Coastal SC into southern GA and AL...
The surface boundary will extend roughly from coastal SC across GA
and into southern AL during the afternoon, with strong heating
expected. Although gradual drying will occur due to westerly flow,
strong heating and sufficient moisture will still result in an
unstable air mass, and eastward-moving storms producing outflow are
anticipated. Given the steep low-level lapse rates, 1000-1500 SBCAPE
and sufficient deep-layer mean winds, isolated damaging gusts will
be possible.

..Jewell.. 04/19/2024

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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
1022 AM CDT Fri Apr 19 2024

Valid 191700Z - 201200Z


The previous forecast (see below) remains on track, with no changes
or additions made.

..Squitieri.. 04/19/2024

.PREV DISCUSSION... /ISSUED 0123 AM CDT Fri Apr 19 2024/

A weak/low-amplitude southern-stream trough will track eastward
across the Southwest, encouraging breezy/gusty southwesterly winds
amid a dry/deeply mixed boundary layer across the region. While
elevated meteorological conditions are likely across portions of
eastern AZ and western NM during the afternoon, marginal fuels
should keep the fire-weather threat fairly localized -- precluding
highlights at this time. Elsewhere across the CONUS, a limited
overlap of warm/dry/breezy conditions will limit fire-weather

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

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