SPC May 11, 2019 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook
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Day 1 Convective Outlook NWS Storm Prediction Center Norman OK
Scattered thunderstorms with severe wind gusts and hail, are
expected on Saturday and Saturday night from southeast Texas across
much of the Southeast into the Carolinas. Isolated severe hail/wind
are also possible across portions of South Dakota and Nebraska. ...Synopsis...
A couple of synoptic-scale waves will dominate the mid-level pattern
across the CONUS today - one amplifying southeastward across the
Dakotas and Nebraska and another cut-off low over northwestern
Mexico. Downstream of the Mexico cutoff low, a belt of enhanced
mid-level flow will persist from Texas east-northeastward to the
Mid-Atlantic. Another cyclonically curved mid-level jet will
migrate southward from the northern High Plains into Nebraska during
the afternoon before shifting into Kansas ahead of the amplifying
trough. A complicated surface pattern will exist across the southern/eastern
CONUS. A weak synoptic front will stretch from the Mid-Atlantic
southwestward to southeast Texas. This front will move little
throughout the forecast period as weak cyclogenesis occurs in the
Tennessee Valley. Meanwhile, one or more outflow boundaries will
likely reside along the Lower Mississippi River Valley in response
to ongoing convection in southern Mississippi/Louisiana. Another
surface low will shift southeastward across the Dakotas today, with
another cold front migrating southeastward across South Dakota and
Nebraska. ...Southeast Texas through the Carolinas...
Scattered, mostly elevated convection should be ongoing at the
beginning of the period across south Texas, with far more isolated
convection expected farther east from Mississippi toward the
southern Appalachians. Through mid-morning, models depict
convection in Texas potentially growing upscale while migrating
eastward into Louisiana and Mississippi during peak heating hours. Meanwhile, 20-kt southerly 850 mb flow will aid in recovery of a
very moist airmass from the northern Gulf of Mexico, and insolation
should result in areas of moderate to strong instability and minimal
inhibition - especially south of any surface boundaries. Storm mode
and modestly strong mid-level flow (approaching 50 knots in some
areas) lends enough confidence in a relatively focused area of
wind-damage potential from far southeast Texas into southern
Mississippi, and a Slight risk has been introduced for those areas. Isolated instances of large hail and perhaps a tornado or two cannot
be completely ruled out. Farther downstream, moderate instability and sufficient deep shear
will exist for convection to develop over the course of the
afternoon. Storms should eventually evolve into a mix of cells and
linear bands with time, with damaging winds possible as mid-level
flow strengthens across the area. A lack of focused lifting
mechanism suggests that storms should be less focused compared to
areas farther west. A Slight risk may be needed in later updates if
a more focused damaging-wind threat becomes apparent. ...Eastern Nebraska and vicinity...
The combination of surface heating and rapid cooling aloft with
approach of the mid-level wave will contribute to enough instability
to support scattered convection - primarily before sunset. Models/CAMs suggest that these storms should organize along a cold
front migrating southeastward across the region, with an attendant
risk for isolated damaging wind gusts and hail. ..Cook/Leitman.. 05/11/2019 

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