SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CDT Wed Jul 20 2022
Valid 221200Z - 231200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL PLAINS INTO THE UPPER MIDWEST...AND THE MID-ATLANTIC
INTO SOUTHERN NEW ENGLAND...
...SUMMARY...
Isolated strong to severe thunderstorms may occur Friday from parts
of the central Plains into the Upper Midwest, and from portions of
the Mid-Atlantic into southern New England.
...Central Plains into the Upper Midwest...
An elongated upper trough/low with multiple centers should remain
over parts of central/eastern Canada on Friday. A belt of enhanced
mid-level west-northwesterly flow is forecast to remain over much of
the northern tier of the CONUS through the period. At the surface, a
weak low should develop generally eastward over south-central Canada
and ND through the day, with another area of low pressure
potentially centered over SD. Rich low-level moisture should remain
confined along/south of a weak front that is forecast to extend from
parts of the central Plains northeastward into the Upper Midwest.
Moderate to strong instability should develop across the warm sector
with daytime heating, but a cap may inhibit thunderstorm development
for much of the day.
Still, some guidance suggests that isolated to scattered convection
will develop from parts of NE into northern/central IA, southern MN,
and WI by late Friday afternoon. This region will have only
modest/nebulous large-scale ascent present aloft, but sufficient
veering/strengthening of the wind profile with height through
mid-levels should support convective organization with any
thunderstorms that can develop along/near the front. Have included
low severe probabilities for now given the uncertainty with overall
thunderstorm coverage and placement, but the overall environment
appears sufficient for multicells and perhaps a couple of supercells
posing a threat for both isolated large hail and severe wind gusts.
...Mid-Atlantic into Southern New England...
Mid-level heights are forecast to slowly rise across most of the
Mid-Atlantic into New England on Friday. Even with generally
subsident flow aloft, there is a signal in most guidance that
convection may develop ahead of a secondary cold front as a weak
mid-level perturbation traverses over these regions. Forecast
instability and shear appear adequate for an isolated severe threat
with any thunderstorms that can form. Have opted to include a
Marginal Risk for parts of southern NY into northern PA/NJ and far
southern New England where the best signal for robust convection
exists.
..Gleason.. 07/20/2022
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