SPC AC 160513
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1213 AM CDT Tue Jul 16 2019
Valid 171200Z - 181200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE UPPER
Strong/severe thunderstorms are possible across portions of the
upper Mississippi Valley. Isolated strong storms may also be noted
across parts of the Plains and over portions of the northeastern US.
...Upper MS Valley...
Seasonally strong mid-level short-wave trough is forecast to eject
across the northern inter-mountain region during the day1 period
which should aid organized convection across the northern High
Plains Tuesday night. Latest guidance suggests an MCS may evolve
ahead of this feature late day1 that should propagate across central
SD by sunrise Wednesday. While late-evening guidance differs a bit
regarding the timing of the affiliated short wave, there is reason
to believe the Plains MCS may continue east into southern MN as LLJ
shifts downstream ahead of the disturbance. It's not entirely clear
how much convection, if any, will root into the boundary layer where
more buoyant parcels will exist. However a strong signal does exist
for organized elevated convection propagating east across southern
MN along the nose of aforementioned LLJ. Wind and some hail are the
Farther southwest along surface boundary, strong low-level heating
will contribute to parcels reaching their convective temperatures
and isolated high-based convection should evolve across eastern NE
into western KS. This activity could produce isolated severe wind
gusts as sub-cloud temp/dew point spreads may approach 40F at peak
Isolated strong/severe thunderstorms may also develop across eastern
WY within post-frontal easterly flow regime. Forecast soundings
suggest a few supercells may form after 22z and this activity should
spread toward the Black Hills after sunset.
Isolated strong storms may also develop across eastern ND into
northwest MN if sufficient instability develops in the wake of
early-MCS that tracks across SD into southern MN. Large-scale
forcing for ascent will be stronger across this region as exit
region of 500mb speed max is forecast to translate across southeast
ND into northwest MN during the early evening hours.
...Delmarva to southern New England...
Remnants of Barry are forecast to eject across the OH Valley into
western NY/PA by 18z. Somewhat stronger mid-level flow will evolve
ahead of this feature along a corridor into southern New England
where boundary-layer heating is expected to be maximized. Forecast
soundings exhibit mean cloud-layer flow on the order of 25kt. With
surface temperatures expected to rise into the 90s, steepening
surface-3km lapse rates should enhance downdraft potential with
convection across this region.
...MAXIMUM RISK BY HAZARD...
Tornado: 2% - Marginal
Wind: 15% - Slight
Hail: 5% - Marginal
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z