SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0155 PM CST Sat Dec 12 2020

Valid 122000Z - 131200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms remain possible this afternoon over a small
part of the Ohio Valley, and late tonight into early Sunday across a
portion of Oklahoma and north Texas.

...20Z Update...
Occasional lightning flashes may still occur with low-topped
convection across parts of northern OH and far southeastern Lower MI
for the next couple of hours. While strong low-level flow has been
noted in the KCLE VWP, instability remains meager (MUCAPE 100-200
J/kg). Accordingly, the potential for strong/gusty winds with this
convection is expected to remain very isolated at best. Otherwise,
no changes have been made to the general thunderstorm area across
parts of north TX and OK for late tonight.

..Gleason.. 12/12/2020

.PREV DISCUSSION... /ISSUED 1046 AM CST Sat Dec 12 2020/

...Ohio Valley and Great Lakes region...

Surface low situated over lower MI will accompany a low amplitude,
but vigorous shortwave trough into the lower Great Lakes today. The
Trailing cold front will advance east through the OH and TN Valleys.
Due to limited low-level moisture and widespread clouds, the
pre-frontal warm sector is only weakly unstable with a narrow
corridor of 200-300 J/kg MUCAPE. As of late morning, a band of
showers and thunderstorms persists within zone of deeper forcing
along and just ahead of the front from IN into western OH. Activity
is embedded within 40-60 kt flow in the 1-5 km layer. A strong wind
gust or two cannot be ruled out, mainly from a portion of eastern IN
into west central OH. However, severe threat should remain limited
due to the very marginal thermodynamic environment and a tendency
for deeper forcing to shift northeast into the Great Lakes with
time.  

...Oklahoma and North Texas...

A shortwave trough now moving into the Great Basin will amplify as
it reaches the southern High Plains late tonight. Steepening 700-500
mb lapse rates and a strengthening southerly low-level jet, within a
zone of increasing forcing for ascent, might result in a convective
layer deep enough for a few lightning flashes late in the period
from a portion of northern TX into southern OK.

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