Special Marine Warning 21, NWS Grand Rapids, MI

530 
FZUS73 KGRR 150335
MWSGRR

Marine Weather Statement
National Weather Service Grand Rapids MI
1135 PM EDT Wed Jul 14 2021

LMZ849-868-150400-
/O.CON.KGRR.MA.W.0021.000000T0000Z-210715T0400Z/
1135 PM EDT Wed Jul 14 2021

...A SPECIAL MARINE WARNING REMAINS IN EFFECT UNTIL MIDNIGHT EDT...

For the following areas...
  Nearshore and Open Waters from Pentwater to Manistee MI...

At 1135 PM EDT, a strong thunderstorm was located near Big Sable
Point Light, moving northeast at 35 knots.

HAZARD...Wind gusts 34 knots or greater.

SOURCE...Radar indicated.

IMPACT...Small craft could be damaged in briefly higher winds and 
         suddenly higher waves.

Locations impacted include...
Ludington Light.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent lightning is occurring with this storm. If caught on the
open water stay below deck if possible, keep away from ungrounded
metal objects.

&&

LAT...LON 4426 8634 4412 8643 4406 8652 4397 8646
      4381 8643 4387 8671 4404 8683 4415 8680
      4426 8663 4428 8644
TIME...MOT...LOC 0335Z 237DEG 37KT 4415 8647 

HAIL...0.00IN
WIND...>34KTS

$$

JC

321 
FZUS73 KGRR 150355
MWSGRR

Marine Weather Statement
National Weather Service Grand Rapids MI
1155 PM EDT Wed Jul 14 2021

LMZ849-868-150405-
/O.EXP.KGRR.MA.W.0021.000000T0000Z-210715T0400Z/
1155 PM EDT Wed Jul 14 2021

...THE SPECIAL MARINE WARNING WILL EXPIRE AT 1200 AM EDT...

The affected areas were... 
  Nearshore and Open Waters from Pentwater to Manistee MI...

The thunderstorm has moved out of the area and no longer poses a
significant threat to boaters.

LAT...LON 4426 8634 4412 8643 4406 8652 4397 8646
      4381 8643 4387 8671 4404 8683 4415 8680
      4426 8663 4428 8644
TIME...MOT...LOC 0355Z 237DEG 37KT 4425 8626 

$$

JC

Area Forecast Discussion
National Weather Service Grand Rapids MI
1015 PM EDT Wed Jul 14 2021

LATEST UPDATE...
Update/Marine

.SYNOPSIS...
Issued at 323 PM EDT Wed Jul 14 2021

- Periods of convection/mostly heavy rain threat into Friday

- Questionable dry period Saturday into Sunday

- Likely dry and warm early next week

&&

.UPDATE...
Issued at 956 PM EDT Wed Jul 14 2021

First round of showers and storms have moved through the primarily
the northwest of the lower peninsula, weakening as they passed
the lake. Another weakening round is currently moving onshore
north of Whitehall. The next round of showers and storms are
currently in Iowa and far western Wisconsin. These storms are
fairly strong but will weaken as they move eastward. The strong
jet support should remain in place as that system propagates
eastward which will allow for an unsettle overnight period. Strong
moisture advection and antecedent conditions near Ludington
indicates that will be the area of concern.

&&

.DISCUSSION...(This evening through next Wednesday)
Issued at 323 PM EDT Wed Jul 14 2021

- Periods of convection/mostly heavy rain threat into Friday

The question really is how much of the convection heading this way
can actually get into western Lower Michigan this evening? The
line seems to want to weaken north of the WI state line and
develop south of that as it heads eastward. There is some
instability head of the line for it to continue to march east
while continuing to develops to the south as the best surface
based cape is over central IL.

On the other hand there is decent shortwave clearly visible on the
water vapor loops over western MN heading east just behind the MCV
that is now heading this way. The shortwave trailing the
convective complex is a synoptic scale wave on the primary branch
of the polar jet. This is causing the convection to run into
upstream ridging which is causing it to weaken. Meanwhile the
better dynamics of the main shortwave will cause additional
convection to form behind the current convection. That second area
of convection will move into central and Michigan (mostly north of
M-20) toward midnight. That has better upper jet support, a 45 to
50 knot low level jet, impressive 1000/850 moisture transport and
over 1000 j/kg of most unstable cape to work with. Note to
that we have mid level warm advection tonight too. The instability
will be elevated so severe storms seem unlikely but with the
upper jet parallel to to surface boundary, we will get training
echos and hence heavy rain. Having nearly 2" of precipitable
water to work with will help the cause. Since the low level jet
axis will be north of I-96 that is where the storms will be.

What to expect tonight is the lead band of convection will likely
reach our western shores between 7 pm and 8 pm then dissipate is
it moves inland. I expect little if any severe storms with this,
maybe special marine warnings as it crosses our near shore waters.
Then the trailing area of convection, which should develop by
sunset will move into our area by midnight. That will be mostly
north of Muskegon (I-96). I expect several hours of storm there.
Eventually the storms will redevelop southward on their outflow
and that will bring some showers and maybe a thunderstorm to areas
south of I-96. That will be toward sunrise.

The trailing part of the shortwave, in combination with surface
heating will redevelop storms near I-69 midday. Those will head
toward southeast Michigan during the mid to late afternoon. Some
of these may have damaging winds with them.

- Questionable dry period Saturday into Sunday

So then we have a rainy glitch! Yet another shortwave on the
polar jet will be heading this way for Friday. However yet another
shortwave rotating around the deeply wrapped up, centered off the
west coast will build the western ridge once again and that will
deepen the downstream trough. So, as our next shortwave moves into
our area it may be best place to deepen and close off. If that
happens the next wave on the front will head northeast into our
area and we would get another period of thunderstorms with soaking
rain Friday night into Saturday. It would not be out of the
question for yet another such event Sunday morning too. Now we
will go with the idea those two waves on the front will stay south
of here but there is a real chance they will not. At least a 1/3
of the ensembles of the ECMWF bring the systems into this area.

- Likely dry and warm early next week

Finally by Monday a system on the northern stream will have gone
over the top the western ridge in central Canada and be heading
southeast toward the northern Great Lakes. That will push the
upper wave or closed upper low east and give us at least 2 days of
warm /hot weather with no rain. After that the upper trough may
have deepened enough over the eastern CONUS to bring us back into
a more active northern stream pattern. This would not be all that
warm either.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 716 PM EDT Wed Jul 14 2021

Showers should exit KMKG after an hour or so with the remainder of
the terminal locations maybe seeing a brief light rain shower in
the first few hours of the TAF period. Otherwise...looking at
storms currently moving through Iowa and Illinois to potentially
impact SW Lower Michigan after 06z through 18z. Low Level wind
shear is expected for a few hours as well around and after 06z.

&&

.MARINE...
Issued at 956 PM EDT Wed Jul 14 2021

Convection overnight, especially in the northern zones is
possible, especially with strong low level flow. Southwest winds,
along with gusty westerly flow overnight will build waves 3 to 5
feet into Thursday. So we will continue our marine headlines and also the
beach hazard headlines

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from 2 AM EDT Thursday through Thursday
     evening for MIZ037-043-050-056-064-071.

LM...Small Craft Advisory from 2 AM to 8 PM EDT Thursday for
     LMZ844>849.

&&

UPDATE...Ceru
SYNOPSIS...WDM
DISCUSSION...WDM
AVIATION...Maczko
MARINE...Ceru

Hazardous Weather Outlook
National Weather Service Grand Rapids MI
713 PM EDT Wed Jul 14 2021

MIZ037>040-043>046-050>052-056>059-064>067-071>074-152315-
Mason-Lake-Osceola-Clare-Oceana-Newaygo-Mecosta-Isabella-Muskegon-
Montcalm-Gratiot-Ottawa-Kent-Ionia-Clinton-Allegan-Barry-Eaton-
Ingham-Van Buren-Kalamazoo-Calhoun-Jackson-
713 PM EDT Wed Jul 14 2021

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

.DAY ONE...Tonight

Overnight thunderstorms will be possible tonight. Dangerous
lightning, heavy downpours and gusty winds will be possible in any
storm. There is some risk for localized minor flooding in areas
where thunderstorms persist overnight.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

There is a low risk for severe thunderstorms Thursday. Dangerous
lightning, gusty winds and heavy rainfall can be expected with any
thunderstorms.

Additional rain may occur Friday and Saturday that could bring
some localized minor flooding to areas that see rain multiple days
this week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed.

LMZ844>849-152315-
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-
713 PM EDT Wed Jul 14 2021

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

.DAY ONE...Tonight

Hazardous conditions for small craft and swimmers will develop
tonight.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Strong winds and thunderstorms will bring hazardous conditions for
small craft and swimmers Thursday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed.