Severe Thunderstorm Warning 29, NWS Wilmington, OH

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
946 PM EDT Tue Apr 7 2020

.SYNOPSIS...
A warm front north of the area will keep an influx of more moist
and unstable air over the Ohio Valley tonight. Thunderstorms,
some severe, are forecast to sweep through the area overnight
with the passage of a cold front. A brief period of high
pressure and dry weather on Wednesday will be followed by
another more potent cold front Wednesday night containing
additional showers and thunderstorms.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Current surface analysis indicates that low pressure is moving
ESE across southern Michigan, with widespread strong to severe
convection running south of / ahead of the low from Port Huron
MI to Chicago IL. The warm sector in place to the south of this
low is currently free of storms or any signs of convective
development, capped by quite a bit of warm air located at about
750mb. Current conditions within the warm sector (across IN/OH)
are characterized by SW winds, temperatures in the upper 60s to
lower 70s, and dewpoints in the mid 50s to around 60.

The main focus for tonight is on the potential for severe
thunderstorms, as the aforementioned convection moves southwest
through Indiana and Ohio. There appears to be a well-defined
wind shift and theta-e boundary in the lower levels that will
move southwest, crossing through the ILN forecast area between
06Z-12Z, with storms generally focused ahead of it. Upper level
support for convection is not as impressive, with generally
broad ridging aloft, and no obvious signs of large-scale
vorticity advection. Thus, the forcing part of the equation for
tonight is mixed -- favorable in the low levels, and not so much
aloft. A westerly LLJ is expected to develop across Indiana in
the 00Z-06Z time frame, providing a surge of warmth and moisture
into the boundary layer, which should keep conditions favorable
for additional thunderstorm development as the evening turns
into the overnight.

The key factor for tonight is instability, with high confidence
(now supported by the 00Z KILN sounding) in very steep lapse
rates aloft. The evening sounding indicated 700mb-500mb lapse
rates of 7.4 degrees C/km, and several models are indicating
that these mid-level lapse rates may exceed 8.0 degrees C/km in
the next few hours across the northern / northwestern sections
of the ILN forecast area. When looking at projections of CAPE,
it is interesting to note that the CAPE from a lifted parcel is
arranged a little differently on the sounding than might be
normal -- the majority of the instability (and the greatest
separation from atmospheric temperature to parcel) is focused
high in the troposphere, within a zone where hail growth is
favored. Deep-layer wind shear is also impressive enough to
allow for storm organization (supercells / clusters) which will
further enhance the threat for hail. This forecast is in
agreement with the SPC D1 outlook, which indicates the potential
for significant hail.

There are also a couple of limiting factors that should be
discussed. First off, there are some concerns with storm
coverage, especially on the western periphery of the developing
convective system. The last few runs of the HRRR have been quite
meager with the western extent of convection. However, not too
much attention is being paid to this solution -- current
upstream radar imagery and the expected theta-e surge (mentioned
above) would suggest that convective development is more likely
than not to continue across much of the CWA -- especially the
northern half. Second off, there are some concerns with
boundary layer stability, which can be assessed to some degree
by looking at surface dewpoints. Most of the model projections
(sans the NAM which is well too moist) suggest that dewpoints
in the ILN CWA will increase from the mid 50s to the lower 60s
over the next few hours. It remains to be seen if dewpoint
advection will be strong enough to do this. The expected
vertical profile ahead of the storms will likely feature only
marginal lapse rates in the lowest few thousand feet, topped (as
mentioned) by very steep lapse rates further aloft. Any
marginal lapse rates near the surface, and any remnant of the
cap that sticks around, would work to significantly limit the
threat for convective wind. If these storms congeal into more of
a cold-pool driven MCS, the wind threat would obviously
increase. As a final note -- 0-1km shear orientation and
magnitude, combined with the issues of boundary layer stability,
would suggest that the tornado threat for this event is not
particularly high.

Severe Thunderstorm Watch 84 is now in effect for the northern
three ILN counties, and additional watch issuance further south
may be needed.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Cold pool stratus trailing the storms from earlier overnight
will break up in the morning from northwest to southeast as
drier air works in with high pressure to the north. Upper level
height fields drop off slightly and the more traditional cold
front with the tiniest of recoveries on Thursday or a
steady/slow drop in readings through the day is expected with
upper level support reinforcing the cold advection beyond this
period.

Showers and possibly a few thunderstorms over the southern
portions of the CWA are possible overnight as the next front
crosses tomorrow night, beginning towards midnight in the
northwest and exiting by daybreak in the southeast.

Highs Wednesday will be in the upper 60s to lower 70s, with
overnight lows ranging from near 40 in the northwest to near 50
in the southeast.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
We could see a few lingering showers across our far southeast
Thursday morning but with the cold front moving off to our
southeast, expect mainly dry conditions through the day. In
decent CAA through the day, temperatures will likely not recover
too much with highs ranging from the mid 40s northwest to
possibly mid 50s across the southeast. The CAA and a fairly
tight pressure gradient will also lead to some gusty winds
through the day.

Surface high pressure will build east across the Ohio Valley
Thursday night through Friday night, leading to dry but
seasonably cool conditions. Lows Thursday night will be down
into the mid 30s but think winds may stay up enough to help
limit frost development. Highs on Friday will generally be in
the 40s. Lows Friday night will be in the low 30s and with
lighter winds, it looks like a better chance for some frost.
This will be somewhat dependent though on how fast clouds
possibly move in later Friday night/early Saturday morning.

Mid level short wave energy will lift out of the Southern
Plains and across the lower Ohio Valley Saturday into Sunday.
This will help carve out a broader trough across the central US
through early to mid next week. Models differ on their
timing/placement and strength of an associated surface low that
will lift northeast across the eastern US/possibly Great Lakes
region Sunday into Monday. This will lead to an increasing
chance of showers and perhaps a thunderstorm through the later
half of the weekend. Will allow for a gradual increase in pops
heading into Sunday/Sunday night, but mostly limit them to high
likely or chance given some of the uncertainty. For that same
reason, will linger some slight chance pops on into Tuesday.
Temperatures (and winds) through this time period will also be
dependent on the strength/track of the low. Have trended toward
the model blend for temps (and consall for winds).

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions will continue for the start of the TAF period,
with gusty WSW winds. Going into the overnight hours, the main
concern will be for thunderstorms to move in from the north.
Some of these storms may be severe, so strong winds and hail are
a possibility -- along with IFR conditions. The most likely
timing for storms will be in the 05Z-08Z time frame for
KDAY/KCMH/KLCK/KILN and a couple hours later for KCVG/KLUK.

After the storms depart, winds will shift to the northwest, and
a period of MVFR ceilings is expected for most locations.
However, confidence is not particularly high in the ceiling
forecast, and some areas may stay mainly VFR. At any rate, by
15Z, VFR conditions are expected again with clearing skies.

Very little weather of consequence is expected through the
daytime hours tomorrow, with NW winds at or below 10 knots, and
VFR conditions. The next chance for showers and storms will move
in after the end of the TAF period.

OUTLOOK...Thunderstorms are possible Wednesday night. MVFR
conditions are possible Wednesday night through Thursday
morning.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.

&&

SYNOPSIS...Franks
NEAR TERM...Hatzos
SHORT TERM...Franks
LONG TERM...Sites
AVIATION...Hatzos

Hazardous Weather Outlook
National Weather Service Wilmington OH
333 PM EDT Tue Apr 7 2020

INZ050-058-059-066-073>075-080-KYZ089>100-OHZ026-034-035-042>046-
051>056-060>065-070>074-077>082-088-081945-
Wayne-Fayette IN-Union IN-Franklin IN-Ripley-Dearborn-Ohio-
Switzerland-Carroll-Gallatin-Boone-Kenton-Campbell-Owen-Grant-
Pendleton-Bracken-Robertson-Mason-Lewis-Hardin-Mercer-Auglaize-Darke-
Shelby-Logan-Union OH-Delaware-Miami-Champaign-Clark-Madison-
Franklin OH-Licking-Preble-Montgomery-Greene-Fayette OH-Pickaway-
Fairfield-Butler-Warren-Clinton-Ross-Hocking-Hamilton-Clermont-Brown-
Highland-Adams-Pike-Scioto-
333 PM EDT Tue Apr 7 2020

This Hazardous Weather Outlook is for East Central Indiana,
Southeast Indiana, Northeast Kentucky, Northern Kentucky, Central
Ohio, South Central Ohio, Southwest Ohio and West Central Ohio.

.DAY ONE...This afternoon and tonight.

Thunderstorms are expected to cross the region late this evening and
overnight. Some strong to severe storms are possible, with large
hail and damaging wind being the primary threats. A tornado cannot
be ruled out.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

There is a low probability for widespread hazardous weather.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed, while following all local, state
and CDC guidelines.

Special Weather Statement
National Weather Service Wilmington OH
1244 AM EDT Wed Apr 8 2020

OHZ034-035-080515-
Auglaize OH-Mercer OH-
1244 AM EDT Wed Apr 8 2020

...A STRONG THUNDERSTORM WILL AFFECT NORTHWESTERN AUGLAIZE AND
NORTHERN MERCER COUNTIES UNTIL 115 AM EDT...

At 1243 AM EDT, radar indicated a strong thunderstorm 7 miles west of
Rockford, moving east at 60 mph.

STORM HAZARDS INCLUDE...
Penny size hail...

Locations impacted include...
Celina, Wapakoneta, St. Marys, Fort Shawnee, Cridersville, Rockford,
New Knoxville, Moulton, Mendon, Buckland, Chattanooga, Kossuth, Tama,
Neptune, State Route 116 at State Route 197 and Bulkhead.

This includes I-75 in Ohio between mile markers 110 and 118.

To report hazardous weather conditions, go to our website at
weather.gov/iln and submit your report via social media, when you can
do so safely.

LAT...LON 4072 8446 4068 8445 4069 8422 4066 8422
      4066 8411 4064 8411 4050 8419 4048 8428
      4048 8434 4047 8434 4046 8438 4056 8480
      4073 8480
TIME...MOT...LOC 0443Z 280DEG 51KT 4066 8479

Hatzos

Special Weather Statement
National Weather Service Wilmington OH
110 AM EDT Wed Apr 8 2020

OHZ034-035-043-044-080545-
Auglaize OH-Logan OH-Shelby OH-Mercer OH-
110 AM EDT Wed Apr 8 2020

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN SHELBY...
NORTHWESTERN LOGAN...AUGLAIZE AND NORTHEASTERN MERCER COUNTIES UNTIL
145 AM EDT...

At 109 AM EDT, radar indicated a strong thunderstorm near St. Marys,
moving east at 50 mph.

STORM HAZARDS INCLUDE...
Winds to 45 mph...
One half inch diameter hail...

Locations impacted include...
Celina, Wapakoneta, St. Marys, Coldwater, Fort Shawnee, New Bremen,
Minster, Cridersville, Anna, Jackson Center, Russells Point, Botkins,
Lakeview, New Knoxville, Waynesfield, Chippewa Park, Moulton, Mendon,
Chickasaw and Buckland.

This includes I-75 in Ohio between mile markers 98 and 118.

To report hazardous weather conditions, go to our website at
weather.gov/iln and submit your report via social media, when you can
do so safely.

LAT...LON 4068 8445 4069 8422 4066 8422 4066 8411
      4064 8411 4064 8388 4042 8388 4036 8418
      4047 8467 4073 8460 4073 8446
TIME...MOT...LOC 0509Z 282DEG 43KT 4061 8435

Hatzos

Special Weather Statement
National Weather Service Wilmington OH
120 AM EDT Wed Apr 8 2020

OHZ034-042-080545-
Darke OH-Mercer OH-
120 AM EDT Wed Apr 8 2020

...A STRONG THUNDERSTORM WILL AFFECT NORTHERN DARKE AND SOUTHERN
MERCER COUNTIES UNTIL 145 AM EDT...

At 120 AM EDT, radar indicated a strong thunderstorm near Portland,
moving east at 50 mph.

STORM HAZARDS INCLUDE...
Winds to 45 mph...
One half inch diameter hail...

Locations impacted include...
Coldwater, Versailles, St. Henry, Fort Recovery, Osgood, Chickasaw,
Burkettsville, North Star, Rossburg, Montezuma, New Weston,
Yorkshire, North Dayton, Rose Hill, Maria Stein, Brock, Eldora
Speedway, Carthagena and Willowdell.

To report hazardous weather conditions, go to our website at
weather.gov/iln and submit your report via social media, when you can
do so safely.

LAT...LON 4050 8446 4020 8444 4030 8481 4055 8480
TIME...MOT...LOC 0520Z 282DEG 41KT 4044 8490

Hatzos

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