SPC AC 201958
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 PM CDT Fri May 20 2022
Valid 202000Z - 211200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR A SMALL
PART OF EASTERN PENNSYLVANIA INTO NEW JERSEY...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
LOWER MICHIGAN...AND OKLAHOMA INTO NORTH TEXAS...
Severe thunderstorms are expected to be most concentrated over
portions of the northern Mid-Atlantic states, Lower Michigan, and a
small part of the southern Plains this afternoon and evening.
Have trimmed severe probabilities behind a small cluster of
thunderstorms over eastern PA. Damaging winds should continue to be
the main threat with this activity as it spreads into NJ over the
next couple of hours, but a tornado or two also remain possible. See
Mesoscale Discussion 842 and 843 for more information on the
near-term severe threat across this area.
An intense supercell producing a tornado is ongoing at 1958Z over
northern Lower MI. The 19Z sounding from APX shows a favorable
environment for continued thunderstorm organization, and it appears
plausible that this supercell will persist across the rest of
northern Lower MI over the next hour or so. A threat for tornadoes,
large to very large hail, and damaging winds should persist with
this supercell in the short term, and with any other intense
thunderstorms that can develop. Still, weak large-scale ascent will
probably tend to limit overall coverage through the rest of the
afternoon, with the overall severe threat probably remaining fairly
isolated. See Mesoscale Discussion 844 for additional details on the
near-term severe threat across northern Lower MI.
Elsewhere, little to no changes were made to the outlook.
.PREV DISCUSSION... /ISSUED 1126 AM CDT Fri May 20 2022/
...Mid Atlantic Region...
A well-defined MCV is noted on satellite imagery over southwest PA.
This feature will track eastward today across PA, northern MD, and
into NJ, fostering the development of severe thunderstorms.
Destabilization ahead of the MCV, combined with strong low and
mid-level wind fields near the circulation will promote the
development of supercell and bowing structures capable of damaging
winds, large hail, and a few tornadoes. Given the rapid eastward
motion of the activity, it should move off the NJ coast well before
dark, ending the severe threat.
A strong surface cold front currently extends from southern WI
northward into upper MI. This front will cross Lake Michigan this
afternoon and move into lower MI by early evening. Thunderstorms
are expected to form in vicinity of the front and move across parts
of the northern Lower MI. Forecast soundings suggest favorable
parameters for large hail in the stronger storms, along with the
possibility of isolated tornadoes.
A cold front is sagging southward across OK today, and should stall
for awhile this evening before progressing into TX overnight. A
strengthening southerly low-level jet atop the boundary will lead to
scattered thunderstorms in a very unstable air mass. Storms may be
supercellular with large hail and damaging winds. A tornado or two
cannot be ruled out before activity becomes more linear after dark.
A moist boundary layer is present today across the FL peninsula,
along with pockets of strong heating. Scattered thunderstorms have
begun to form over south FL, and this activity is expected to build
northward through the day. Relatively cool temperatures and modest
westerly flow aloft will promote a few organized multicell storm
clusters capable of gusty/damaging winds or perhaps hail.
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