Chicago, IL...Columbus, OH...Nashville, TN...Kansas City, MO...Lexington-Fayette, KY...
Probabilistic Damaging Wind Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk
Area (sq. mi.)
Some Larger Population Centers in Risk Area
Indianapolis, IN...St. Louis, MO...Little Rock, AR...Springfield, MO...Springfield, IL...
Chicago, IL...Columbus, OH...Milwaukee, WI...Nashville, TN...Kansas City, MO...
SPC AC 280539
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1139 PM CST Mon Feb 27 2017
Valid 281200Z - 011200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM AR TO
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN OK TO
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
TX TO WESTERN PA...
Severe thunderstorms are expected to develop from portions of the
lower Mississippi Valley to the Ohio Valley Tuesday. Large hail,
damaging winds, and a few strong tornadoes are possible.
Ridging appears to be responsible for delaying meaningful convection
across the MS Valley late this evening. However, LLJ is beginning
to increase across MO/IL and isolated thunderstorms are evolving
within a corridor from the Bootheel of MO into central IL. This
activity should gradually expand in areal coverage as warm advection
lifts north toward the Great Lakes region. Given these trends,
there is increasing confidence that much of the southern
Plains/lower MS valley will remain convection-free into the
afternoon hours. As a result, significant boundary-layer recovery
is expected into the OH Valley prior to frontal passage.
Late evening model guidance continues to suggest a corridor of
strong southwesterly flow aloft will extend from the southern
Rockies, into the Great Lakes with 500mb flow expected to increase
in excess of 80kt by early afternoon across western portions of the
severe risk area. Large-scale height falls will overspread the
Mississippi Valley and several convective scenarios may ultimately
evolve within a broad moistening warm sector.
1. Warm-advection corridor (northern IL):
Strengthening LLJ over IL will aid northward advance of higher
quality air mass as surface dew points rise through the 40s into the
50s as far north as northern IL by late morning. Warm advection is
expected to induce scattered strong/severe thunderstorms early in
the period as warm front lifts northward in advance of the primary
surface wave. Convection may be aided by a weak mid-level
disturbance embedded within the stronger southwesterly flow.
Initial activity will be elevated in nature and hail is the primary
risk with these storms.
2. Warm sector (AR/MO/IL):
28/00z sounding from OUN exhibited a steep-lapse-rate environment
with substantial low-level moisture. Strong capping and
neutral-weak subsidence will allow this air mass to advect northeast
such that surface dew points should rise into the lower 60s across
much of the warm sector south of I-70. Breaks in cloud cover during
the day should allow surface parcels to approach their convective
temperatures from eastern OK into southwestern MO by mid-late
afternoon. Latest thinking is isolated supercells may evolve well
ahead of the cold front along nose of a secondary branch of LLJ that
will strengthening across AR during the day. It's not clear how
much storm coverage will be noted across this region but
environmental shear and increasing instability/buoyancy favor robust
supercells. Forecast soundings suggest very large hail could
accompany this activity and a few strong tornadoes are possible,
especially if discrete structures evolve as it appears they may.
3. Cold front:
Large-scale forcing will contribute to a convectively active cold
front by early evening as the wind shift surges into an increasingly
moist/unstable air mass from eastern IA into northern MO.
Thunderstorms are expected to mature into a strong squall line that
will surge east across the mid MS Valley into the OH valley as 500mb
flow increases to near 100kt by 01/12z. Damaging winds should be
noted with this frontal convection and tornadoes may also be
embedded along the line. Eastward momentum should easily allow this
activity to spread across much of OH by sunrise Wednesday morning.
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