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Showers and Possible Thunderstorms Today

Some scattered showers and a couple rumbles of thunder will be possible from late morning to early afternoon. Stronger storms may develop during the late afternoon through the evening. Some of these storms could become severe, with damaging winds and hail possible. Read More >

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FLUS43 KAPX 181444

Hazardous Weather Outlook
National Weather Service Gaylord MI
1044 AM EDT Sun Aug 18 2019

Straits of Mackinac within 5 nm of Mackinac Bridge including
Mackinac Island-St Ignace to False Detour Channel-
5NM East of Mackinac Bridge to Presque Isle Light MI including
Bois Blanc Island-
Presque Isle Light to Sturgeon Pt MI Including Thunder Bay
National Marine Sanctuary-Sturgeon Pt to Alabaster MI-
Grand Traverse Bay south of a line Grand Traverse Light to
Norwood MI-Seul Choix Point to 5NM West of Mackinac Bridge-
Norwood MI to 5NM West of Mackinac Bridge including Little
Traverse Bay-Sleeping Bear Point to Grand Traverse Light MI-
Point Betsie to Sleeping Bear Point MI-
Manistee to Point Betsie MI-
Whitefish Bay (U.S. Portion)/Whitefish Point to Point Iroquois MI-
St. Marys River Point Iroquois to E. Potagannissing Bay-Emmet-
Cheboygan-Presque Isle-Leelanau-Antrim-Otsego-Montmorency-Alpena-
Benzie-Grand Traverse-Kalkaska-Crawford-Oscoda-Alcona-Manistee-
Western Chippewa-Central Chippewa-Southeast Chippewa-
Western Mackinac-Eastern Mackinac-
Mackinac Island/Bois Blanc Island-Beaver Island-Charlevoix-
1044 AM EDT Sun Aug 18 2019

This hazardous weather outlook is for northern Lower Michigan...
eastern Upper Michigan...and adjacent nearshore waters of Lake
Michigan...Lake Huron and Lake Superior.

.DAY ONE...This afternoon and tonight.

Thunderstorms are possible this afternoon and evening across the
outlook area...with a low risk for a severe storm east of a
Manistee to Rogers City line. Large hail and damaging wind gusts
would be the main threat.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Thunderstorms are possible across the outlook area Tuesday night.


Spotter activation is not anticipated.


For more information visit


ACUS01 KWNS 181258
SPC AC 181256

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0756 AM CDT Sun Aug 18 2019

Valid 181300Z - 191200Z


The main severe-thunderstorm threat today will be damaging winds,
isolated hail and a few tornadoes are possible.

In mid/upper levels, a belt of zonal to gently cyclonic mean flow
will be observed through the period across the northern half of the
CONUS. As a cyclone moves slowly northeastward across northern MB,
the trailing shortwave trough should pivot from the Dakotas across
MN and Lake Superior to northeastern ON. As that occurs,
convectively aided/induced vorticity lobes should move eastward
across the upper Great Lakes. This includes a shortwave
perturbation associated with a pronounced MCV now located over
southern WI, and extending south-southwestward behind a band of
convection across southern WI and northwestern IL.

The 11Z surface chart showed a low near EAU, related to the MCV,
with wavy warm front extending across western/southern WI and
southern Lower MI. This front should drift northward before being
overtaken by an ongoing MCS and additional convection developing
farther east. A cold front was drawn from southeastern MN across
southeastern NE and northwestern KS. By 00Z this front should reach
eastern Upper MI, central WI, southern IA, central/southwestern KS,
and southeastern CO. By 12Z this front should extend from northern
Lower MI to northern IL, central/western MO, northwestern OK,
becoming quasistationary northwestward into southeastern CO.

...Great Lakes vicinity...
An intermittently organized band of convection, continuing eastward
from overnight activity across IA, has persisted across the
Mississippi River the past couple hours. Some of this activity may
strengthen across the remainder of the northern IL/southern WI/Lake
Michigan region eastward over northern IN and southern lower MI, as
the foregoing/inflow-layer air mass destabilizes from a combination
of warm advection and diabatic surface heating. Recovery behind
newer convection over northeastern IL is uncertain in magnitude and
northern extent. See SPC severe thunderstorm watch 597 and related
mesoscale discussions for near-term details.

In concert with seasonally steep low/middle-level lapse rates and
rich low-level moisture (60s to near 70 F surface dew points), areas
of 2000-3000 J/kg preconvective MLCAPE are expected to develop.
This will occur amidst difluent but generally westerly mid/upper
winds, enhanced on the mesoscale by height falls related to the MCV,
and a plume of large-scale DCVA/lift preceding the shortwave trough.
As the heating continues, MLCINH effectively will vanish over
northeastern IL and eastward through midday, potentially fostering
additional convective development and severe potential in and near
the watch area, regardless of the morphology of the initial MCS.
Subsequent aggregation and upscale growth should shift the primary
threat of damaging winds across lower MI and northern IN. In
addition, areas of relatively maximized effective SRH may support
localized tornado potential in QLCS circulations.

...Ozarks to portions of OK...
Isolated to scattered thunderstorms, with highly variable coverage
in space and time, are possible through the overnight period across
this region. Activity should be concentrated mainly near outflow/
differential-heating boundaries area-wide and near a weak
convergence zone over the southwestern OK/northwest TX region this
afternoon. Isolated severe gusts and hail may occur, with well-
mixed air below LFC developing this afternoon, and persisting into
tonight above a slowly stabilizing near-surface layer, aiding in
maintenance of hail/gusts to surface.

A relative concentration in severe potential also may become
apparent this afternoon over portions of this region, especially in
the Ozarks/eastern OK/southeastern KS area. Beneath steep midlevel
lapse rates, pockets of relatively convectively undisturbed
boundary-layer moisture and strong heating may support MLCAPE around
4000 J/kg. Uncertainties regarding location, orientation, and
strength of supportive mesoscale boundaries preclude a more-
concentrated area of unconditional probabilities at this time.

..Edwards/Marsh.. 08/18/2019


ACUS02 KWNS 180501
SPC AC 180500

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1200 AM CDT Sun Aug 18 2019

Valid 191200Z - 201200Z


Isolated severe storms are possible over parts of the northern
Plains Monday evening and overnight.

A negative-tilt shortwave trough will quickly eject northeast across
Quebec, resulting in rising heights over the Great Lakes during the
day. A brief period of lift will occur over northern parts of the
northeastern states, where weak instability will develop. Overnight
and to the west, subtle height falls will occur over the northern
Plains and Upper MS Valley, on the southern fringe of a shortwave
trough over MB. Here, a cold front will move into the central
Dakotas by 00Z, with mid 60s F dewpoints spreading northward ahead
of it aiding destabilization and supporting at least isolated

To the south, strong instability will once again develop over the
central Plains, but will be capped for most of the period.

...Northern Plains...
Strong heating will occur over ND, northern MN, and western SD along
and west of the wind shift. The air mass over the moist sector will
be capped for much of the day, but a narrow zone of uncapped air
should develop along the front. Isolated late afternoon and evening
storms are possible with marginal wind or hail. Overnight, elevated
instability will develop from NE/IA into MN, and sporadic storms
cannot be ruled out from northeast KS into IA. However, the
probability of severe in those areas appears low prior to 12Z

...Northern NY into ME...
Low-level winds will continue to veer during the day as the
shortwave trough ejects east/northeast over the region. Forecast
soundings show sufficient instability for thunderstorms during the
day, and modest deep shear, but midlevel subsidence will likely
mitigate overall storm coverage and intensity. As such, severe
weather is not currently forecast, but a few strong storms cannot be
ruled out with gusty winds and small hail.

Tornado: 2% - Marginal
Wind: 5% - Marginal
Hail: 5% - Marginal

..Jewell.. 08/18/2019


FXUS63 KAPX 181437

Area Forecast Discussion
National Weather Service Gaylord MI
1037 AM EDT Sun Aug 18 2019

Issued at 1014 AM EDT Sun Aug 18 2019

...Isolated severe storms possible this afternoon...

A complex and somewhat convoluted pattern this afternoon with a
convectively induced vorticity center moving across the upper
Great Lakes, with an MCS tracking along a warm frontal boundary
into southern Michigan. In addition, a trailing cold front over
southeast Minnesota is pushing toward the western Great Lakes.
Convective line over southern Lake Michigan will push
east/northeast through this afternoon, remaining strongest to the
south with a much weaker northern end moving into northern lower
Michigan (with some showers and possibly a thunderstorm). Despite
warming daytime temperatures and dewpoints in the 60s,
instability still not that impressive over much of northern lower
through mid-afternoon (500-750 j/kg). Convective vort center to
the north may bring additional shower/tstm chances to mainly upper
Michigan this afternoon.

With continued daytime heating, expect showers/storms to re-
solidify and strengthen over east/southeast parts of the area
by later afternoon/early evening. This is the best chance of an
isolated severe storm for our area today, with damaging winds and
large hail being the main threats. All in all, confidence just not
that high in this forecast given the number of mesoscale
convective features.

Temperatures also a challenge this afternoon given increasing
cirrus shield and possible showers/storms. Likely warmest toward
Lake Huron with the greatest amount of sunshine.


.NEAR TERM...(Today through Tonight)
Issued at 433 AM EDT Sun Aug 18 2019

...Trend should be wetter as the day progresses...

High Impact Weather Potential: Marginal severe thunderstorm risk but
threat currently looks small.

Pattern Synopsis/Forecast: 04z surface/composite analysis shows a
cold front extending roughly north-south from far northwest
Ontario/western MN/northeast NE...with a 1003mb frontal wave over
southwest MN. Another boundary extends east from this frontal wave
into southern Lower. Cold front was associated with a strong short
wave trough digging through the prairie provinces and into MT/ND. A
couple areas of convection tied to the cold front
moving across southern MN/northern IA is a nice bowing line with a
well-defined convectively induced vorticity center spinning across
southern MN. To the east of this complex is a broken area of
convection tied to strong low level isentropic ascent along the
Mississippi River from southeast MN into eastern IA/northwest IL.
Additional convection developed along the southern Lower boundary now
tracking northeast through the Thumb. Weather across the forecast
area fairly benign early this morning with some scattered cloud
cover...and areas of fog developing across both eastern Upper and
northern Lower. 00z APX sounding was fairly dry with dew point
depressions greater than 10C in the layer from roughly 900-320mb.

Convective MCV should continue on its eastward track and into Lower
Michigan perhaps by late morning. Synoptic scale short wave trough
digging into Manitoba and the northern high Plains will push the
upstream cold front east into western Upper/WI/eastern IA later this
afternoon...with increasing dynamic forcing and cold front pushing
across the forecast area tonight...may clear most of northeast Lower
around daybreak Monday as high pressure builds into the upper
Mississippi Valley.

Primary Forecast Concerns: Precipitation evolution is the main
problem for today...with the first issue being timing/tracking
upstream MCV and associated MCS. Guidance seems to pick up on some
semblance of this feature but seem to be lagging in its location by
a fair bit. Current trends suggest MCV could reach southwest Lower
in the 15z addition to the more scattered activity
ahead of the MCS which will likely move into northwest Lower by mid
morning. Have not changed precip timing much from earlier
forecast...despite guidance not much interested in spreading precip
east of the I-75 corridor until mid afternoon...believe that there
is some chance of precip getting into northeast Lower toward midday.
Will be mostly on the "stratiform" side of approaching MCS...which
begs the question as to how much destabilization we may see
throughout the day. Day 1 marginal severe risk has been lifted into
the southeast half of the forecast area...but going to reserve
judgment on this until we see how MCS evolves (but not very
optimistic about this). Will keeps some threat for precipitation
going until cold front passage tonight. High temperatures today
will be tricky...lots of guidance suggestions for highs in the lower-
mid 80s especially northeast Lower but if we cloud up and/or
precipitate sooner that may end up being a stretch so have trended
highs a little bit cooler for now.


.SHORT TERM...(Monday through Tuesday)
Issued at 433 AM EDT Sun Aug 18 2019

Short term (Monday through Wednesday):

High impact weather potential: Thunderstorms possible Tuesday
evening and again Wednesday afternoon (maybe?)...none expected to
become severe.

Pattern synopsis and forecast:

Surface high pressure anchored over the Great Lakes will dominate
Monday and Tuesday`s weather, with mostly clear skies, light winds,
and warm temperatures. A weak cold front associated with a low
pressure system over the James Bay region will sweep into the
forecast area late Tuesday night into Wednesday. Cloud cover will be
on the increase ahead of the boundary Tuesday afternoon with rain
and thunder chances arriving during the evening hours. This slow
moving boundary may trigger some more shower and thunderstorm
activity Wednesday afternoon, mainly closer to the Saginaw Bay
region where diurnal heating and possible lake breezes may aid in
the development. Winds will remain fairly light as high pressure
remains overhead and then become southwesterly ahead of the
aforementioned cold front Tuesday afternoon and veer to the
northwest during the afternoon hours Wednesday. With the CAA winds
could become gusty Wednesday afternoon, especially over the lakes
and eastern upper. Temperatures will be in the upper 70s to low 80s
Monday, while Tuesday will reach into the low to mid 80s, possibly
even see some upper 80s, as southwesterly winds advect warmer and
moisture air into the forecast area. Wednesday will be cooler once
again with the CAA behind the said boundary, reaching into the mid
to upper 70s.

.LONG TERM...(Tuesday night through Saturday)
Issued at 433 AM EDT Sun Aug 18 2019

High Impact Weather...None is expected.

The long term models are in agreement with this period mostly being
under surface high pressure with the exception of yet another weak
cold front and attendant upper level wave dropping down from central
Canada during the weekend timeframe. This will most likely be the
only precipitation chances during this forecast period. Temperatures
will continue to be cool Thursday, with some locations possibly not
even reaching 70. Temperatures are expected to moderate a bit each
day after.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 751 AM EDT Sun Aug 18 2019

Brief period of LIFR fog this morning at PLN/APN which should lift
quickly. Watching for thunderstorm potential today ahead of an
approaching cold front...mostly likely during the afternoon hours.
Winds should be gusty from the south/southwest this afternoon.


Issued at 433 AM EDT Sun Aug 18 2019

Increasing southerly winds today may bring low end small craft
criteria to Lake Michigan nearshore zones. Cold front passage
tonight and a period of cold advection/mixing could also bring small
craft conditions to Whitefish Bay/St. Mary`s River and far northern
portions of Lakes Michigan and Huron.


LM...SMALL CRAFT ADVISORY until 10 PM EDT this evening for LMZ344>346.



ACUS11 KWNS 181240
SPC MCD 181240

Mesoscale Discussion 1787
NWS Storm Prediction Center Norman OK
0740 AM CDT Sun Aug 18 2019

Areas affected...southeast Wisconsin...northeast
Illinois...northwest Indiana...and southwest Michigan

Concerning...Severe Thunderstorm Watch 597...

Valid 181240Z - 181445Z

The severe weather threat for Severe Thunderstorm Watch 597

SUMMARY...Thunderstorms continue this morning across the region.
Moderate instability and sufficient shear should continue to support
a severe threat this morning.

DISCUSSION...Initial line of thunderstorms has weakened considerably
this morning as increasing precipitation ahead of the line --
stemming from thunderstorms that developed south-southwest of
Chicago -- has acted to stabilize the airmass across north-central
Illinois and southern Wisconsin. The strongest thunderstorm cluster
from this original band of storms is currently located across
southeast Wisconsin and will have the potential to pose a severe
threat for another couple hours before moving east over Lake

As previously mentioned, additional thunderstorms developed to the
south-southwest of Chicago, ahead of the original line of storms.
These thunderstorms are within a better severe thunderstorm
environment than those to the north given less convective coverage
allowing most-unstable CAPE values to approach 2000 J/kg, and thus
have a greater potential to pose a severe wind or hail threat. At
present, these storms will move across the greater Chicago metro
over the next 1-2 hours, with hail and wind threats likely. These
storms will continue east-northeast through the morning, eventually
moving over Lake Michigan.

..Marsh.. 08/18/2019

...Please see for graphic product...


LAT...LON 41049091 41209108 41419104 41449078 41599076 41599087
42029080 42069013 42489062 42508982 43228976 43318965
43308901 43208900 43188789 43358783 43408645 43468638
43458608 43288607 43298559 43408553 43438437 42808436
42778417 42068412 42058483 41528482 41538517 40998536
40968558 41048583 40928619 40908692 40738713 40728752
40988754 40998824 41098827 41088891 40908890 40928904
41078907 41098930 41138931 41128957 41228965 41228981
41118988 41149040 41049043 41049091