Special Weather Statement, NWS Grand Rapids, MI

Area Forecast Discussion
National Weather Service Grand Rapids MI
207 PM EDT Sun Apr 24 2022

LATEST UPDATE...
Aviation

.UPDATE...
Issued at 1130 AM EDT Sun Apr 24 2022

A cold front is moving east at 1100am from a position across
Central Wisconsin and Western Illinois. Surface dew points are
pooled along and ahead of the front...with 60F dew points surging
through Northeast Illinois into Southeast Wisconsin. 60F dew
points should overspread the Grand Rapids forecast area this
afternoon. Partial sunshine is occuring in our area east of a line
from Mt Pleasant to Grand Rapids to Kalamazoo. At this time, per
the SPC Mesoanalysis page instability remains low...with MUCAPE
values less than 500 j/kg and LI's around -1C. Mid level lapse
rates are not overly steep with 7.0 C/KM being about the max at
this time. We are going to have to destabilize from below as mid
level temperatures largely do not change this afternoon. So, this
will occur via the low level moisture advection and heating in the
breaks occurring to the east.

The 12Z HREF has shown an increase in thunderstorm activity for this
afternoon and evening over the last 3 runs (including this
morning's run). We see this in the MAX 4hr and 24hr reflectivity
swaths. The 50dbz echo that is painted across our CWA has
increased. It is centered in the 400pm to 800pm time frame.
Updraft helicity swaths remain higher than yesterday's 12Z run
which suggest there will be more storm organization. This is due
to 40-50 knots of wind at 850mb and 65 knots of wind at 500mb.
This equates to deep layer shear values on the order of 50 knots.

The strength of the wind fields and lack of directional shear
produce straight line hodographs which suggest damaging winds are
the main threat. The lack of significant instability (1000-1500
j/kg of MUCAPE at max heating) make hail a lesser threat. Cannot
rule out a tornado (very low chance) given the strength of the
wind fields, but do not see this as much of a threat. Expecting
broken lines of storms with the potential of some damaging wind
gusts to around 60 mph. Main time frame is 300pm to 1000pm, but
especially between 400pm and 800pm. Zone of biggest threat will be
south and east of Grand Rapids and Big Rapids. Radar interrogation
this afternoon and evening will focus on monitoring bowing
segments for strong winds and any storms that can acquire rotation
for wind and hail.

&&

.DISCUSSION...(Today through next Saturday)
Issued at 336 AM EDT Sun Apr 24 2022

-- Severe weather remains possible this afternoon/evening --

Our biggest potential impact weather over the next seven days looks
to be the severe threat this afternoon/evening across portions of
the area.

There has not been a lot of change generally speaking over the last
few model runs regarding this potential event this afternoon. The
biggest potential looks to occur over the SE portion of the area,
roughly east of a South Haven-GR-Mt. Pleasant line. East of this
line is where there is good agreement that there will be less in the
way of pcpn and cloud cover, and better heating will take place.

These favored areas could see temps approaching 80 degrees with dew
points up around 60F once again, which would increase ML CAPE values
over 1,000 J/kg. This is not ideal, but could be enough for some
severe weather given favorable shear values. Effective shear values
off of forecast soundings indicate up around 50 knots of deep layer
effective shear with the mid level jet being close by. These shear
values will give storms that develop a chance to become strong to
severe.

All hazards do look to be in play for the area with this potential
event. We expect a scattered to broken line of convection orientated
from SW to NE to develop or strengthen near the differential heating
boundary that separates the better instability from lesser amounts.
Low level 0-3km shear vectors indicate they will be fairly parallel
to the line. The wind fields would support a wind threat where the
shear vectors are more perpendicular to the storms. Mid level lapse
rates are around 6.5 C/km or so, with somewhat thinner CAPE
profiles. Finally, a tornado threat does exist as there is enough 0-
3km shear with the low level jet overhead. Also, forecast hodographs
show some decently curved profiles with veering winds.

We believe the best time for severe weather will be from around 3-7
pm before the line would move east of the area.

Additional showers and embedded storms will be possible after the
line ahead of the cold front. SE areas would be favored for
additional rain.

-- Colder early this week with rain/snow chances --

We will see a secondary cold front and upper trough move through
during the daylight hours of Monday. This scenario will keep temps
from warming much as the colder air floods in at that point. There
is not really expected to be any rain with the secondary front as
the atmosphere is quite dry at that time.

We will see precipitation chances increase some for Tuesday. Favored
areas will be across the north where the upper trough diving over
the region will be more centered on. 850 mb temperatures are
forecast to drop to -5 to -10C by late Tuesday afternoon.
Instability/cold pool showers will develop with the next upper wave
moving overhead. The air will be cold enough to support some snow
showers on Tuesday.

-- Moderating temps with small rain chances mid-late week --

The upper trough and associated showers will move out of the area by
Wednesday morning, and high pressure will build in. There is a
fairly decent upper ridge slowly building in. At the sfc, high
pressure centered near Hudson Bay will drive cool and dry air down
from the NE. This ridging at the sfc and aloft will still around,
and help to dry things out a bit. Temperatures will slowly moderate
as return flow gradually sets up. The air will be dry enough that a
couple of week systems that try to move in will not be able to
sustain pcpn for a bit, maybe until next weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 207 PM EDT Sun Apr 24 2022

Showers and thunderstorms will be possible this afternoon and
evening at all TAF sites between 300pm and 1000pm. The
precipitation will occur ahead of a cold front that will lag
behind the showers/storms by a few hours. There may be a few hour
period of MVFR ceilings with the precipitation at any TAF site
with the best chance occurring at KMKG and KGRR. Overnight,
conditions should primarily be VFR in the wake of the front.
Another chance for rain occurs Monday morning towards KJXN.

Winds will be gusty from the south-southwest this afternoon at
14-30 knots. Winds will subside considerably after sunset and
certainly by midnight.

&&

.MARINE...
Issued at 336 AM EDT Sun Apr 24 2022

We will be holding on to the Small Craft Advisory that is in effect
until early Monday. Winds will be holding up through early Monday,
but will stay limited with the warmer air moving in over the colder
waters of Lake Michigan. Conditions may flirt with Gales at times,
but it stays marginal enough for now to hold off on the upgrade.

There is a brief break late Sunday night/Monday morning. As quick as
it comes down, the winds, and eventually the waves will come back
up. This looks like another solid Small Craft Advisory.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 2 AM EDT Monday for LMZ844>849.

&&

UPDATE...Duke
DISCUSSION...NJJ
AVIATION...Duke
MARINE...NJJ

Hazardous Weather Outlook
National Weather Service Grand Rapids MI
511 AM EDT Sun Apr 24 2022

MIZ037>040-043>046-050>052-056>059-064>067-071>074-250915-
Mason-Lake-Osceola-Clare-Oceana-Newaygo-Mecosta-Isabella-Muskegon-
Montcalm-Gratiot-Ottawa-Kent-Ionia-Clinton-Allegan-Barry-Eaton-
Ingham-Van Buren-Kalamazoo-Calhoun-Jackson-
511 AM EDT Sun Apr 24 2022

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

.DAY ONE...Today and Tonight

Strong to locally severe thunderstorms will be possible this
afternoon and evening. The highest chance of severe weather will
be between 3 pm and 10 pm this evening. The highest threat will be
strong winds, with large hail, locally heavy rainfall, and isolated
tornadoes also possible. Areas east of a line from Mt. Pleasant to
GR to South Haven will have the highest chance for severe weather.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening.

LMZ844>849-250915-
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-
511 AM EDT Sun Apr 24 2022

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

.DAY ONE...Today and Tonight

Winds and waves will continue to produce hazardous conditions for
Small Craft. This threat will taper off overnight.

There will be a chance of a few thunderstorms through today.
Severe weather is not likely over the lakeshore, however some
cloud to water lightning, gusty winds, small hail, and locally
heavy downpours are possible.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening.

Special Weather Statement
National Weather Service Grand Rapids MI
308 PM EDT Sun Apr 24 2022

MIZ051-242015-
Montcalm MI-
308 PM EDT Sun Apr 24 2022

...A strong thunderstorm will impact portions of northeastern
Montcalm County through 415 PM EDT...

At 308 PM EDT, Doppler radar was tracking a strong thunderstorm near
Stanton, moving northeast at 60 mph.

HAZARD...Wind gusts up to 50 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Stanton...             Edmore...              Lakeview...
Sidney...              McBride...             Langston...
Westville...           Cedar Lake...          Entrican...
Six Lakes...           Vestaburg...           Turk Lake...
Wyman...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4333 8485 4321 8524 4331 8533 4347 8532
      4346 8485 4344 8484
TIME...MOT...LOC 1908Z 224DEG 52KT 4331 8517

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH

LAURENS