LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0252 PM CDT Sat Aug 26 2023
Valid 262000Z - 271200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND
EVENING ACROSS THE SOUTHEAST MO/NORTHEAST AR VICINITY...
...SUMMARY...
Occasional damaging gusts will be possible this afternoon and
evening across southeast Missouri/northeast Arkansas and vicinity,
with more isolated strong winds possible into the southern
Appalachians and across parts of Idaho and Oregon.
...20Z Update...
Overall, no changes are needed to the previous outlook. More
forecast details provided below and in the appended outlook.
...Southeast MO/northeast AR area this afternoon/evening...
As mentioned in recently issued MCD #2054, thunderstorms capable of
producing isolated to scattered damaging winds will become
increasingly possible later this afternoon across parts of southern
MO/IL, northern AR, and western KY/TN. Strong heating and large PW
will support a threat of at least isolated wet microbursts as these
storms sag southward through the afternoon.
...Southern Appalachians into the Central Carolinas...
As discussed in MCD #2055, strong heating ahead of an
eastward-progressing MCV, along with typical diurnal terrain
circulations should support additional thunderstorm development
through this afternoon. Moderate buoyancy (1000-2000 J/kg of MLCAPE)
and fairly steep low-level lapse rates should support occasional
strong updrafts. As result, isolated strong to severe storms, with
the potential for a few damaging downburst gusts, will be possible
this afternoon and evening across the region.
...Southern ID/Eastern OR...
Thunderstorm development has already be observed across the region
ahead of the approaching speed max, with additional storm
development still possible this afternoon/evening. Modest vertical
shear could help organize updrafts, with high cloud bases and steep
low-level lapse rates contributing to the potential for isolated
strong/severe outflow.
..Mosier.. 08/26/2023
.PREV DISCUSSION... /ISSUED 1127 AM CDT Sat Aug 26 2023/
...Southeast MO/northeast AR area this afternoon/evening...
The persistent midlevel high continues to slowly weaken over the
southern Plains, while a series of MCVs rotate around the northern
and eastern periphery of the high, from KS to the southern
Appalachians. The most pronounced MCV is now moving southeastward
over northwest MO and will interact with the unstable warm sector
this afternoon in the vicinity of southeast MO, where additional
thunderstorm development is expected south of the ongoing convection
near Saint Louis. Daytime heating in cloud breaks and
boundary-layer dewpoints in the mid 70s will result in MLCAPE of
2500-3000 J/kg, and lapse rate profiles will also favor strong
downdrafts (DCAPE of 1000-1500 J/kg). Primarily multicell clusters
are expected as a result of weak vertical shear in the warm sector
ahead of the MCV. Damaging outflow winds will be the main severe
threat from mid-late afternoon into this evening.
...Southern ID/eastern OR this afternoon/evening...
A weak mid-upper speed max is translating northward around the
western periphery of the ridge from the southern Plains into the
Rockies. A band of ascent and midlevel moisture, coincident with
surface heating in cloud breaks, will support scattered thunderstorm
development this afternoon into this evening. Typical inverted-V
profiles and some modest enhancement to deep-layer vertical shear
will support somewhat organized cells (and perhaps a low-end
supercell) capable of producing isolated strong-severe outflow
gusts.
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