Thunderstorms forecast to develop this afternoon…severe risk continues.
Latest updates from the Storm Prediction Center continue to highlight the entire Chicago metro area for a risk of scattered severe thunderstorm development this afternoon.
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1104 AM CDT Sat Jun 01 2019
Valid 011630Z – 021200Z
…THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PORTIONS
OF MO AND IL….
Widely scattered severe thunderstorms are expected mainly this
afternoon and evening from Lake Michigan vicinity southwestward to
the central/southern High Plains. Large hail and damaging winds will
be the primary threats.
Water vapor imagery shows a well-defined shortwave trough over IA.
This feature will track east-southeastward into parts of IL/IN this
afternoon and evening, providing large-scale ascent and aiding in
the development of scattered thunderstorms. Multiple clusters of
storms are expected today, with each holding some risk of severe
Thunderstorms currently over southwest Lower MI are expected to
track eastward and intensify later today as they approach western
Lake Erie. These storms will then continue eastward across
southeast Lower MI and northern OH, with the potential for damaging
winds and hail. Refer to MCD #919 for further details.
Other strong storms are expected to form this afternoon near the
surface low over southern WI and northern IL. Forecast soundings in
this area suggest large CAPE values and sufficient vertical shear
for a few organized multicell or occasional supercell structures,
capable of large hail and damaging winds.
By mid afternoon, thunderstorms are expected to form along a cold
front sagging across northwest IL and northern MO. These storms
will be near the core of stronger midlevel winds associated with the
shortwave trough, and in region where model guidance provides
highest confidence of longer-lived storms and possible supercells.
This activity should spread southeastward across the ENH risk area
through the evening with a threat of damaging wind gusts and large
hail. Very large hail is possible with initial supercells.
Surface observations at noon, CDT showed the area to be in the warm sector of a low pressure center located over SW Wisconsin. Temperatures have warmed to around 80 degrees, with dew points in the low-mid 60s, helping to make the atmosphere increasingly unstable. The low center will track eastward, while a trailing cold front presses southeast into northern and central Illinois.
Thunderstorms are expected to erupt by mid-afternoon, especially in the vicinity of the low and cold front.
Satellite imagery shows one storm cluster moving across southern lower MI, but new storms appear ready to develop over southern WI, at the intersection of the low and an outflow boundary left by the MI storm cluster. More cloud growth was noted over eastern IA as well.
The prime time for storms in the Chicago metro area looks like the 4-7 PM period. Some storms may be capable of hail and damaging wind gusts in addition to heavy downpours. The storms are expected to be fairly progressive, so excessive rainfall amounts (1-2 inches or more) appear unlikely.