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acus01 kwns 281636
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Storm Prediction Center ac 281635
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
1135 am CDT Fri Apr 28 2017
Valid 281630z - 291200z
..there is an enhanced risk of severe thunderstorms OK to Tennessee
Valley...
..there is a slight risk of severe thunderstorms surrounding the
enhanced risk...
..there is a marginal risk of severe thunderstorms southern Great
Plains to central Appalachians...
...
Numerous severe storms are expected today, initially across parts of
the Ohio and Tennessee valleys this afternoon, and across the
southern Great Plains and Ozarks by tonight. Very large hail,
tornadoes, and damaging winds are anticipated.
...
Potential exists for multiple severe episodes this afternoon into
tonight across the enhanced risk characterized by increasing
moisture, moderate to strong buoyancy, and ample vertical shear.
However, some of this risk is conditional and confidence is below
average in mesoscale details regarding severe coverage.
..TN/Ohio valleys...
A mid-level impulse over eastern NE should decay during the period
as an upstream shortwave trough pivots over The Four Corners into
AZ/nm. This will effectively yield rising heights over a large
portion of a poleward-advecting warm sector emanating from the Gulf.
This warm sector will remain characterized by rather rich mean
mixing ratios with upper 60s to middle 70s surface dew points
becoming established from the Ohio Valley on south as a warm front
passes north through this evening.
Within the low-level warm-advection regime, elevated convection is
ongoing from NE/Iowa into MO/IL. Additional activity may develop
farther south/east closer to the advancing warm front towards late
afternoon. Low-level hodographs will be comparatively large within
this corridor in conjunction with 40-50 kt 850-mb flow. This setup
could support mixed modes of discrete supercells and upscale-growing
bows capable of tornadoes, large hail, and damaging winds. These
threats will probably remain along and north of the warm front, with
capping increasingly pronounced with southern extent in the warm
sector.
..southern Great Plains to the Ozarks...
Similar to areas farther east, an increasingly rich low-level air
mass is steadily returning, but beneath a more substantial 700-mb
cap. This should inhibit sustained storm development until about
03z. Along the northwest periphery of the warm sector, a
consolidating surface cyclone over northwest Texas amid near-neutral
mid-level height change should result in strengthening frontal
convergence and yield storm development over OK into far northwest
OK. Storm coverage should become widespread overnight along and
north of the quasi-stationary front eastward across the Ozarks.
Supercell-favorable wind profiles and steep mid-level lapse rates
should support several rotating storms with large hail (some
significant) as the primary hazard. Damaging winds and a couple
tornadoes will also be possible, particularly with cells that can be
sustained along the quasi-stationary front. The overall evolution
into a broad clustering band with embedded line segments amid an
anafrontal setup should yield a predominant hail and some wind risk,
continuing on an increasingly isolated basis into the overnight.
.Grams/Mosier.. 04/28/2017
$$
Mesoscale Discussion
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Storm Prediction Center mesoscale discussion 272326
gaz000-alz000-280030-
Mesoscale discussion 0576
National Weather Service Storm Prediction Center Norman OK
0626 PM CDT Thu Apr 27 2017
Areas affected...southeastern Alabama into central Georgia
Concerning...Tornado Watch 169...
Valid 272326z - 280030z
The severe weather threat for Tornado Watch 169 continues.
Summary...severe weather potential is expected to become
increasingly negligible through 8-11 PM EDT . A new severe weather
watch is not anticipated, and Tornado Watch 169 may be allowed to
expire as previously scheduled at 8 PM EDT.
Discussion...thunderstorm development persists from near Troy Alabama
through the Columbus Georgia area into areas south of Peach Tree city GA.
This is occurring within a lingering corridor of moderate boundary
layer instability, east southeast of a stalling/weakening frontal
zone. Localized enhanced surface convergence and weak lower/mid
tropospheric warm advection may be contributing to forcing for this
activity, and vertical shear near a 30 kt southwesterly 850 mb jet
axis (beneath 40-50 kt westerly/cyclonic 500 mb flow) remains
strong. However, diurnal boundary layer cooling coupled with a
warming mid-level environment is expected to result in diminishing
convective trends across the region through 00-03z.
.Kerr.. 04/27/2017
..please see www.Spc.NOAA.Gov for graphic product...
Attention...WFO...cae...ffc...tae...bmx...mob...
Latitude...Lon 32168591 33188449 33648383 33488240 32468383 31528580
31398641 31838642 32168591
