Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 281759

Area Forecast Discussion
National Weather Service Grand Rapids MI
159 PM EDT Sat Mar 28 2020


Issued at 159 PM EDT Sat Mar 28 2020

- Locally heavy rain/thunderstorms/risk of severe tonight

- Wind Advisory with showers and colder Sunday

- Cool but quiet weather Tuesday and Wednesday


Issued at 159 PM EDT Sat Mar 28 2020

It would seem to this forecaster the risk for severe storms has
diminished since it now appears the triple point will track near
or south of I-94. This is supported by the NAM, RAP, HRRR and HREF
from the 12z runs. The HREF updraft helicity tracks (pinball`s)
are all south of the state of Michigan tonight. This would
diminish the significantly diminish the risk for tornadoes.

There is a risk for heavy rain tonight as the moisture transport
vectors (1000/850 mb) are aimed at southwest Lower Michigan and
the precipitable water values are over an inch. Not to mention
model sounding are saturate to 300 mb. Most of the rain will be
after 8 pm and it should be done by 6 am.


.DISCUSSION...(Today through next Friday)
Issued at 311 AM EDT Sat Mar 28 2020

- Today

Some elevated instability will continue to bring scattered
thunderstorms through this morning north of surface warm front.
Areas where these storms persist and train could see some rain
rates and amounts creating some flooding of low lying areas.

We do not expect any severe weather with these storms but some
small hail and cloud to ground lightning are possible.

- Tonight

Elevated instability continues to build and there could be some
sfc based instability as well across the far southwest forecast
area by early evening. Fast-moving supercells are depicted by the
NMM and ARW across northern Illinois and model soundings and
shear profiles would support this. Large hail is the primary
threat but a tornado threat is also present across the southwest

So we will have to watch for these storms moving into Van Buren
and Kalamazoo County as being sfc-based before they move east or
northeast and become more elevated to the north of the surface
warm front during the evening.

- Sunday

Sfc low is occluding and filling as it moves off to the northeast
Sunday morning but a strong sfc pressure gradient results in 40
to 50 knot winds in the lowest 3 to 5 kft. There is some
potential for mixing deep enough to bring down strong winds, but
at this point, indications are that it would be more like 35 to 40
knots rather than 45 to 50 knots.

So a Wind Advisory may be needed, especially along Lake Michigan.
Wave heights build to around 10 feet meaning coastal flooding and
beach erosion are also in the mix for Sunday and Sunday night.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 159 PM EDT Sat Mar 28 2020

Solid IFR is expected till the occluded front comes through around
08z Sunday morning. A few showers are expected this afternoon from
time to time but they should not last long or be strong enough to
lower visibility`s into below MVFR.

Tonight as the triple point of the system tracks near I-94 expect
showers and thunderstorms with very heavy rainfall. Also expect
low level shear since the warm front will not clear any of the TAF
sites. I put VCTS since I am not 100 pct on the TAF sites actually
having thunderstorms.

Once the front comes through around 08z or so there may be a brief
clearing of the clouds but that will be short lived. Very strong
southwest winds of 20 to 30 knots will move in by mid morning as
will MVFR/IFR with resistant rain showers.


Issued at 159 PM EDT Sat Mar 28 2020

We will likely issue a lake shore flood advisory due to the high
winds (gales) from the southwest building waves to as high as 10
feet. Likely this will result in shoreline erosion.


LM...Small Craft Advisory from 5 AM to 11 PM EDT Sunday for LMZ849.

     Gale Warning from 5 AM to 11 PM EDT Sunday for LMZ844>848.



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