SPC AC 141245
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0745 AM CDT Fri Aug 14 2020
Valid 141300Z - 151200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS TODAY FROM
EASTERN ND INTO MN...
Severe thunderstorms with damaging wind and hail, and perhaps a
couple of tornadoes, will be possible from eastern North Dakota this
morning into Minnesota this afternoon. Additional severe storm
development is expected this afternoon and evening from western Iowa
into northwestern Kansas.
...MN to KS through early tonight...
A midlevel shortwave trough over the western Dakotas will progress
eastward to the upper MS Valley by tonight. A surface cyclone near
the SD/ND border will develop northeastward across northwestern MN
in advance of the midlevel trough, as a trailing surface cold front
moves southeastward across MN/northwestern IA/eastern NE/and
northern KS by late evening. Low-level ascent along the front will
provide a focus for strong-severe thunderstorm development from mid
afternoon through late evening. The situation will be a little more
complex farther north into eastern ND this morning and northern MN
today, in response to ongoing convection.
Storms across southeastern ND are expected to persist through the
day across eastern ND/northwestern MN, near the path of the surface
cyclone and midlevel jet. Separate convection from central MN into
southeastern ND has produced a cold pool/outflow boundary that will
tend to demarcate the northern extent of the more substantial severe
threat. This boundary may try to retreat northward some today near
the ND/MN border, though the cluster over south central ND will
likely reach east central ND by mid morning, effectively limiting
the time for air mass recovery farther north. This morning cluster
will move along the synoptic front/buoyancy gradient across ND, up
to the northern extent of the outflow from the morning storms in MN.
Damaging winds and large hail can be expected with this morning
cluster. The tornado threat will be modulated by the location of
the outflow boundary, and appears more probable across parts of west
central/northwestern MN as the low levels destabilize near and south
of the outflow by early afternoon, and as vertical shear increases
with the approach of the midlevel trough.
By mid afternoon, convective inhibition should weaken in a narrow
zone along the cold front from southwestern MN across eastern
NE/northwestern IA into northwestern KS. MLCAPE in excess of 3000
J/kg and effective bulk shear of 30-35 kt, in combination with steep
midlevel lapse rates and DCAPE at or above 1000 J/kg, will favor a
mix of multicell clusters/line segments and some splitting
supercells capable of producing damaging winds and large hail.
High-based storms farther south into the TX Panhandle may produce
isolated severe outflow gusts this evening.
...Southern AR into parts of LA/MS today...
An ongoing cluster of storms in southern AR, that originated in a
warm advection zone in advance of a weak midlevel trough, should
continue to spread southeastward on convective outflow today.
Moderate buoyancy/little convective inhibition, and a modest
increase in vertical shear with the southeastward-moving midlevel
trough, could maintain somewhat organized multicell clusters with an
attendant threat for isolated wind damage through this afternoon.
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z