- día tres
acus01 kwns 231631
Storm Prediction Center ac 231630
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
1130 am CDT sun Apr 23 2017
Valid 231630z - 241200z
..there is a slight risk of severe thunderstorms over
..there is a slight risk of severe thunderstorms over South
..there is a marginal risk of severe thunderstorms from northern
Florida into Georgia and South Carolina...
Areas of strong-severe thunderstorms are expected over the southeast
today and overnight. The main threats appear to be damaging gusts
over parts of western/central Georgia and central South Carolina
this afternoon, followed by potential for a few tornadoes and
isolated wind damage overnight in parts of South Carolina.
..Georgia and South Carolina...
Satellite imagery indicates an upper low has formed over western
Tennessee, and this feature is forecast to move southeastward
reaching the Alabama/Georgia border by the end of the period. A
band of stronger mid/upper level winds curving cyclonically around
the southern periphery of the circulation is expected to spread
across parts of Georgia and northern Florida into tonight.
At the surface, a low over extreme northwest Georgia will move
mainly eastward along a quasi-stationary front extending across
east-central Georgia to the central South Carolina coast. The low
is forecast to reach east-central Georgia this evening and cross
into South Carolina by 24/12z. A cold front trailing southward from
the low will progress eastward to the Atlantic coast from Georgia to
northeast Florida by the end of the period. The frontal boundaries
are expected to focus the stronger thunderstorm activity through
Initial storm development is expected along the advancing cold front
by early afternoon from west central Georgia into the Florida
Panhandle as it moves into an axis of slightly greater moisture.
Although mid-level lapse rates are generally weak, visible satellite
imagery indicates stronger diabatic heating will occur in the warm
sector where fewer clouds are present. This will enhance low-level
lapse rates and contribute to modest destabilization with MLCAPE of
500-1000 j/kg this afternoon. With some cam guidance indicating
development of qlcs structures along/slightly ahead of the front,
stronger cells within the line segments will have potential to
produce damaging downbursts as they move through the focused
moisture/instability axis. See mesoscale discussion 550 for more
Other storms are expected to develop over parts of central/southern
South Carolina this afternoon near the aforementioned east-west
front. The lack of clouds south of the boundary is promoting a
strong differential heating zone where attendant mesoscale
circulations will support storm potential this afternoon. Isolated
severe storms will be possible as vertical shear increases over the
area, especially along and immediately north of the boundary where
backed surface flow will enhance low-level shear.
The severe threat over South Carolina is expected to increase
somewhat tonight as a south-southeasterly low-level jet strengthens
in response to the approaching upper low. This will result in
increasing moisture advection from the Atlantic and be associated
with stronger low-level shear with an attendant risk for supercells
to develop. Low local levels and moderate-strong srh indicate
potential for a few tornadoes to occur with any persistent discrete
supercells that develop.
Isolated weak thunderstorms may develop this afternoon and evening
in association with an upper short wave trough that will move
eastward across the Great Basin. Column moisture/total precipitable
water values are quite minimal /approximately 0.25 inch/ which will
limit the coverage and intensity of any convection. However, a dry
sub-cloud layer will enhance evaporative cooling and promote
Transfer of stronger mid-level horizontal momentum to the surface,
suggesting potential for convectively-enhanced surface wind gusts.
Given the aforementioned limiting factors, we will maintain a
sub-severe outlook at this time over the area.
acus11 kwns 231602
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 231602
Mesoscale discussion 0550
National Weather Service Storm Prediction Center Norman OK
1102 am CDT sun Apr 23 2017
Areas affected...portions of western/central Georgia...far southeastern
Alabama...and a small part of the Florida Panhandle
Concerning...severe potential...watch possible
Valid 231602z - 231800z
Probability of watch issuance...40 percent
Summary...thunderstorms should strengthen along a cold front by
early afternoon, posing mainly a strong to locally damaging wind
threat. Watch issuance is possible.
Discussion...as of 16z, a surface low was located over far
northeastern Alabama/northwestern Georgia. A cold front extends southward from
this low generally along the Alabama/Georgia border into far southeastern Alabama
and the western Florida Panhandle, moving eastward with time. Visible
satellite imagery shows partly to mostly sunny skies ahead of the
front across parts of west-central Georgia into the central Florida Panhandle.
A narrow corridor of greater low-level moisture was analyzed along a
line from Atlanta to Macon to Albany GA, continuing southward to
Tallahassee Florida and vicinity. A residual pocket of somewhat lower
Theta-E air was located across central Georgia into northern Florida per
latest surface observations.
As large-scale ascent associated with a mid-level low over western
Tennessee overtakes the surface cold front, an increase in convective
coverage is expected along the length of the front over the next
several hours. Mid-level lapse rates remain generally poor across
this region per various 12z soundings and should remain so through
the afternoon per rap forecast soundings. Even with some diurnal
heating ahead of the front coincident with the narrow corridor of
greater low-level moisture, these poor mid-level lapse rates will
likely act to limit the amount of instability that can develop ahead
of the front. Most short-term guidance suggests MLCAPE should range
between 250-750 j/kg. Mid-level winds are forecast to strengthen
slightly, although only modest veering with height will likely limit
effective bulk shear values to 30-35 kt.
Multicells and line segments along the front should pose an isolated
threat for strong to locally damaging winds through the afternoon,
with perhaps marginally severe hail in a transient supercell
structure also possible. The eastward extent of this isolated threat
will likely be limited by the previously mentioned pocket of
slightly drier low-level air across central Georgia/northern Florida. Radar
trends will be monitored for an increase in convective
coverage/intensity that may necessitate watch issuance.
..please see www.Spc.NOAA.Gov for graphic product...
Latitude...Lon 33258455 33428414 33398360 33098332 32768321 32058330
31178373 30708406 30438488 30568532 30928562 31778510