SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0259 PM CDT Fri Jul 30 2021

Valid 302000Z - 311200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CENTRAL/EASTERN NE
TO SOUTHWEST IA AND NORTHWEST MO...

...SUMMARY...
A couple tornadoes along with scattered damaging winds and large
hail are possible across portions of the central Great Plains to the
Lower Missouri Valley from late afternoon into tonight.

...Discussion...
No change was made to the previous convective outlook.

..Smith.. 07/30/2021

.PREV DISCUSSION... /ISSUED 1128 AM CDT Fri Jul 30 2021/

...Central Great Plains and Lower MO Valley...
Late afternoon to evening thunderstorm development will be focused
along and north of a quasi-stationary front arcing from northeast CO
to central NE to southwest MO. The temperature and dew point
gradient will be largest in the NE portion of the baroclinic zone.
Here, organized severe storms should initiate along a corridor of
moderate to large buoyancy supported by upper 60s to mid 70s
boundary-layer dew points. Initial storms in the central NE vicinity
will be on the fringe of modest deep-layer westerlies (with stronger
flow east; weaker west). This should tend to foster mainly
outflow-dominated cells. However, convection will likely intensify
as it spreads towards eastern NE this evening with effective shear
around 40 kts. Although lower-level lapse rates should progressively
weaken with northern extent from the surface boundary, enlargement
to the low-level hodograph may yield a couple tornadic storms prior
to broader clustering of convection that spreads east-southeast.
Regenerative warm-advection-driven storms should persist across the
Mid to Lower MO Valley through much of the night, although the
overall severe threat will gradually subside during late evening to
early morning as instability diminishes. 

...Southeast VA and central/eastern NC...
A southeast-sagging cold front should be the focus for at least
isolated thunderstorms later this afternoon. In the mid-levels,
relatively warm temperatures and weak lapse rates will be limiting
factors, as well as drier air spreading from west to east. A
moderate buoyancy plume should still develop along the coastal plain
where boundary-layer dew points will be largest. With
west-southwesterly low-level flow, moderate speed shear through the
cloud-bearing layer should foster mainly cellular convection capable
of small hail. This should augment downdraft strength and yield a
threat for locally damaging winds from sporadic downbursts.

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