SPC AC 160600
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Thu Aug 16 2018
Valid 161200Z - 171200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SOUTHEAST KS AND NORTHEAST OK INTO FAR SOUTHWEST MO AND NORTHWEST
Severe thunderstorms will produce gusty, locally damaging winds
across parts of the central and southern Plains this afternoon and
evening. Additional strong thunderstorms are expected from the
middle Mississippi to the lower Ohio Valleys, as well as across
parts of central into northeast Oregon.
A midlevel trough across the Upper Midwest and Mid-MO Valley will
shift east across the Upper Great Lakes and Mid-MS/Lower-OH Valleys
today and tonight. At the surface, a warm and moist airmass, with
dewpoints in the mid 60s to mid 70s F will reside across eastern
portions of the central and southern Plains into the Mid-MS and OH
Valley regions. A somewhat diffuse and stalled frontal boundary
across northern OK into central MO and a southward-advancing cold
front across the Mid-MO Valley will be a focus for strong to severe
thunderstorms during the afternoon and evening. Additional strong
storms are possible in warm advection regime from southern IN/OH
into Middle TN.
Further west, a weak shortwave trough will move onshore the Pacific
Northwest coast after 00z. As the western upper ridge migrates
eastward, increasing southwesterly deep layer flow and modest
midlevel moisture across central into northeast OR could be
sufficient for isolated strong wind gusts with any storms that
...Portions of Central/Southern Plains Vicinity...
Forecast confidence is fairly low this morning as convective
evolution is uncertain and model guidance, both deterministic and
hi-res, is rather inconsistent. Storms may be ongoing at the
beginning of the period across parts of eastern KS. Additionally,
broken cloud cover may limit destabilization across parts of the
region initially. A stalled surface boundary was evident early this
morning across northern AR into northeast OK. This boundary may be a
focus of redevelopment later this afternoon. Furthermore, the
southward-advancing cold front also will be a potential candidate
for storm initiation and intensification. Given that one or both of
these boundaries may initiate storms today into this evening, it is
likely that the slight risk will need further refinement in
Uncertainty in convective initiation location aside, increasing
northwesterly shear on the southern periphery of the midlevel trough
will promote organized convection in a moderately to strongly
unstable airmass. Modest midlevel lapse rates will develop by
afternoon as midlevel cooling overspreads the region. Shear profiles
will be marginally favorable for supercells, but convection will
likely quickly become linear given the presence of the
aforementioned surface boundaries and likely downdraft-dominant
storms in the weak lapse rate/high PW environment. One or more
bowing segments is expected to track south/southeast across portions
of eastern KS into OK/southern MO/northern AR. Strong, locally
damaging wind gusts will be the main threat, though some hail is
possible with the strongest storms.
...Mid-MS/Lower OH Valley...
Several rounds of strong storms will be possible today in warm/moist
advection ahead of the approaching trough. Midlevel southwesterly
flow will increase to 25-35 kt and as moderate destabilization
occurs, some strong multicell clusters are possible. Isolated strong
wind gusts will be possible as weak low level winds and PW values
near 2 inches favor wet microbursts.
...Central into Northeast OR...
Isolated to scattered thunderstorms will develop during the late
afternoon into the evening hours as the upper ridge breaks down.
Strong mid-to-upper level southwesterly flow will result in fast
northeasterly storm motion. Furthermore, a deeply mixed and dry
sub-cloud layer will foster strong downburst wind potential.
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z