SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK
0744 AM CDT Sat Aug 01 2020 Valid 011300Z - 021200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS UPPER OH VALLEY TO
NORTHERN VA... ...SUMMARY...
Scattered damaging winds and a brief tornado are possible, centered
on portions of the Upper Ohio Valley into northern Virginia from
mid-afternoon through this evening. ...OH Valley to western/northern VA...
A broad mid-level trough over the Mid-MS Valley will slowly move
northeast across parts of the Midwest through early Sunday.
Attendant 1008-mb surface cyclone near the confluence of the MS/OH
rivers will evolve northeast, reaching western OH tonight. A broad
belt of 30-40 kt 700-mb southwesterlies should shift from the Deep
South and TN Valley northeast towards the central and southern
Appalachians. Scattered thunderstorm development is expected this afternoon near
and well east of the surface cyclone across the OH Valley, and
within a separate corridor off the central Appalachians/Blue Ridge
in western/northern VA and the eastern WV Panhandle. Although
mid-level lapse rates will remain poor (well sampled by regional 12Z
soundings), surface dew points around 70 should support modest
buoyancy with MLCAPE increasing to 500-1500 J/kg. Along the northern
periphery of the amplifying 850-700 mb flow regime, several small
clusters and a few transient supercells may develop to the northeast
with a primary risk of scattered damaging winds. A brief tornado is
possible as well, mainly during the evening when low-level shear
A belt of enhanced mid-level northerlies will lie across the
central/eastern portions of the state between an anticyclone
centered over the Lower CO Valley and a trough near the MS Valley.
While buoyancy is not expected to be as robust as yesterday, owing
to a drier boundary-layer, weak MLCAPE should contribute to a couple
updrafts with mid-level rotation off the Sangre de Cristo and
Sacramento Mountains with a risk for isolated severe hail.
Otherwise, the steep lapse rate environment will foster a
predominant risk for locally severe wind gusts with isolated to
scattered storms that should peak in the late afternoon to early
evening. ...East-central FL Coast...
T.C. Isaias continues moving steadily northwest toward the FL
Atlantic Coast. The eastern hemisphere of this tropical system is
forecast to remain offshore through the period, along with the more
favorable shear for potential tornadoes. Unless the track of Isaias
shifts farther west, the tornado threat over land should remain too
low to warrant probabilities. ..Grams/Jewell.. 08/01/2020