Severe Thunderstorm Warning 55, NWS Grand Rapids, MI

Area Forecast Discussion
National Weather Service Grand Rapids MI
510 PM EDT Thu Aug 29 2019

LATEST UPDATE...
Mesoscale Discussion

.MESOSCALE DISCUSSION...
Issued at 511 PM EDT Thu Aug 29 2019

After talking with SPC a few moments ago it a severe thunderstorm
watch seems rather unlikely. The best instability (mix layer cape
in the 1500 to 2500 j/kg) stays over Lake Michigan as does the
best downdraft cape (800 to 1200 j/kg). The greatest surface dew
points are currently over southerns Wisconsin, and southern and
central Lake Michigan (in the mid 60s). There is fat cape in the
-10c to -30c range so hail is more than possible. There is also a
 fair amount of mid level dry air as well as inverted "V" look to
 the soundings (RAP model) near the Lake Shore. Winds between 1500
 ft and through 2000 ft area from the west around 40 knots so it
 would not take much to mix the gusts to the surface near the Lake
 Shore. The moisture transport and Low Level jet also suggest the
 greatest risk for severe storms in the next hour or two, west of
 US-131. There is a good chance for isolated severe storms over
 Oceana, Muskegon and Ottawa County as the line of storms moves
 southward but we do not expect the stronger storms to get far
 inland. So the bottom line is watch in unlikely but isolated
 severe storms are still possible west of US-131 for the next 2
 hours.

&&

.SYNOPSIS...
Issued at 257 PM EDT Thu Aug 29 2019

- Line of showers and thunderstorms this evening with potential
  for strong winds

- Fair weather for Friday

- Chance of showers southern Lower Michigan on Saturday and
  Sunday

&&

.DISCUSSION...(This evening through next Thursday)
Issued at 257 PM EDT Thu Aug 29 2019

The marginal risk of severe weather will be across southwest Lower
Michigan late this afternoon and into the evening as line of
storms currently extending from eastern Wisconsin to northwest
Illinois will continue rapidly propagating southeast, then slow as
it reaches southern Lower Michigan.

Main threat with the storms appears to be strong downdrafts as
indicated by the deep, dry adiabatic sub-cloud layer seen in
observed and forecast soundings. An isolated tornado is also
possible with deep layer shear values around 40 knots and low
level SRH values spiking around the time of the storms moving
through.

Fair weather to follow the storms tonight and Friday. An area of
warm advection showers breaks out across southern zones by
Saturday and spreads a bit further north on Sunday. Labor Day
looks dry at this point.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 145 PM EDT Thu Aug 29 2019

VFR conditions will prevail until late this afternoon when a line
of showers and thunderstorms will bring areas of MVFR and brief
IFR in some heavier downpours. The storms will move from northwest
to southeast, reaching MKG by 22Z and JXN about 2 or 3 hours
later.

Winds will be southwest gusting over 20 knots through the evening.
Some thunderstorms could have strong downdrafts with near surface
winds gusting over 40 knots.

&&

.MARINE...
Issued at 257 PM EDT Thu Aug 29 2019

No changes to the Small Craft Advisory. A line of thunderstorms
will move across Lake Michigan through late afternoon with the
potential for winds gusting over 40 knots in stronger storms.
Conditions will calm down quickly later this evening.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until 8 PM EDT this evening for MIZ037-
     043-050-056-064-071.

     Lakeshore Flood Advisory until 8 PM EDT this evening for MIZ037-
     043-050-056-064-071.

LM...Small Craft Advisory until 8 PM EDT this evening for LMZ844>849.

&&

MESOSCALE...WDM
SYNOPSIS...Ostuno
DISCUSSION...Ostuno
AVIATION...Ostuno
MARINE...Ostuno

Hazardous Weather Outlook
National Weather Service Grand Rapids MI
303 PM EDT Thu Aug 29 2019

MIZ037>040-043>046-050>052-056>059-064>067-071>074-301915-
Mason-Lake-Osceola-Clare-Oceana-Newaygo-Mecosta-Isabella-Muskegon-
Montcalm-Gratiot-Ottawa-Kent-Ionia-Clinton-Allegan-Barry-Eaton-
Ingham-Van Buren-Kalamazoo-Calhoun-Jackson-
303 PM EDT Thu Aug 29 2019

This hazardous weather outlook is for portions of southwest Lower
Michigan.

.DAY ONE...This Afternoon and Tonight

There is a marginal risk of severe storms through this evening.
The main threat is strong downburst winds. THere is also the
possibility of a tornado.

Lakeshore flooding and hazardous swim conditions are expected
into this evening.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening.

LMZ844>849-301915-
St Joseph to South Haven MI-South Haven to Holland MI-
Holland to Grand Haven MI-Grand Haven to Whitehall MI-
Whitehall to Pentwater MI-Pentwater to Manistee MI-
303 PM EDT Thu Aug 29 2019

This hazardous weather outlook is for portions of southwest Lower
Michigan.

.DAY ONE...This Afternoon and Tonight

Winds and waves will be hazardous to small craft through early
evening. There is also a threat of strong thunderstorms with winds
gusting over 40 knots through early evening.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

No hazardous weather is expected at this time.

Special Weather Statement
National Weather Service Grand Rapids MI
309 PM EDT Thu Aug 29 2019

MIZ037>040-043>046-050>052-056>059-292100-
Mason-Lake-Osceola-Clare-Oceana-Newaygo-Mecosta-Isabella-Muskegon-
Montcalm-Gratiot-Ottawa-Kent-Ionia-Clinton-
Including the cities of Ludington, Baldwin, Reed City, Clare, Hart,
Fremont, Big Rapids, Mount Pleasant, Muskegon, Greenville, Alma,
Grand Haven, Jenison, Grand Rapids, Ionia, and St. Johns
309 PM EDT Thu Aug 29 2019

...Thunderstorms approaching Southwest Lower Michigan...

At 300 PM EDT...a line of thunderstorms extending from northeast to
southwest across Manitowoc Wisconsin will move east at 45 mph,
reaching Ludington around 4 PM and a Muskegon to Mount Pleasant line
around 6 PM.

These storms will produce frequent lightning and strong gusty winds
that could produce localized damage and power outages. Stay alert to
approaching thunderstorms this afternoon and evening and be ready to
take shelter inside a sturdy building.

Special Weather Statement
National Weather Service Grand Rapids MI
456 PM EDT Thu Aug 29 2019

MIZ043-044-050-292200-
Oceana-Muskegon-Newaygo-
456 PM EDT Thu Aug 29 2019

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NEWAYGO...MUSKEGON AND
OCEANA COUNTIES...

At 455 PM EDT, National Weather Service meteorologists were tracking
strong thunderstorms located along a line extending from 7 miles
southwest of Silver Lake State Park to 30 miles west of Whitehall.
Movement was east at 50 mph.

Winds in excess of 40 mph and penny size hail are possible with
these storms. Winds could knock down tree limbs and create scattered
power outages.

Frequent cloud to ground lightning is occurring. Lightning can
strike 10 miles away from a thunderstorm. Seek a safe shelter inside
a building or vehicle.

LAT...LON 4366 8654 4375 8646 4382 8643 4382 8557
      4330 8556 4329 8579 4320 8579 4321 8591
      4312 8591 4312 8627 4332 8640 4350 8647
      4362 8654
TIME...MOT...LOC 2052Z 277DEG 43KT 4362 8664 4344 8709

CAS