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fxus63 kgrr 211148 
afdgrr

Area forecast discussion
National Weather Service Grand Rapids Michigan
748 am EDT Mon Oct 21 2019

Latest update...
aviation

Synopsis...
issued at 330 am EDT Mon Oct 21 2019

- gales expected on Lake Michigan as well as another damaging
Lakeshore flood/erosion event (see marine section for details).

- Band of rain showers to work through the area today with isolated
thunderstorms possible.

- Windy conditions today through Tuesday Night.

- Lake effect rain Tuesday through Tuesday night.

- Additional small chances for precipitation through the period.

&&

Discussion...(today through next sunday)
issued at 330 am EDT Mon Oct 21 2019

Another Fall storm system will affect the region over the course of
the next 36 to 48 hours. We finally have some consensus with the
depth of the low, in the 980's mb's, over Wisconsin. Yesterday a run
of the European model (ecmwf) deterministic had a 975mb low over Wisconsin. Now both
the GFS and European model (ecmwf) are in the low 980's. Still a formidable low by
Great Lakes fall standards. A reason why this will be a bit more
impactful in terms of winds along the Lakeshore is that the low in
Wisconsin pinwheels towards US late tonight into Tuesday morning.
This will place the tightest pressure gradient right over Lake
Michigan. See details in the marine section on the Gale Warning and
Lakeshore Flood Warning that are now in place. We may need to
consider a Wind Advisory on the land in the Lakeshore counties for
especially on Tuesday. At this point holding off on that, but the
day shift may need to consider it.

A band of rain showers will work through the area today along and
ahead of the occluded/cold fronts. Still only weak instability, but
not out of the realm of possibilities to see a few isolated
thunderstorms. We will be watching this as there is significant wind
aloft on the order of 60 knots at 3000ft today. Also considered a
Wind Advisory today on the land in the warm air advection, but
thought the stable conditions of clouds and rain should keep US just
under advisory criteria on the "warm" side of the system.

A dry slot will work through tonight with lake effect rain showers
kicking in late tonight into Tuesday as instability increases over
Lake Michigan. The lake is around +13c right now, or 55f. We need
temps around 0c at 850mb's to generate lake precip which swings in
tonight. A raw day on Tuesday with lake effect rain and brisk winds.

Conditions improve Tuesday night with the wind beginning to ease up
slightly and the lake precipitation starting to wind down.

Much of the remainder of the period will feature fairly quiet
weather with ridging in place at the surface late in the week. We do
have a surface trough moving through Wednesday into Wednesday night
which will bring some scattered rain showers.

Into next weekend there is some disparity between the GFS and European model (ecmwf)
in regard to a system moving into the southern Great Lakes. The ec
has a system the GFS does not. At this point we have small pops, 20
pct out on Saturday night into Sunday.

&&

Aviation...(for the 12z tafs through 12z Tuesday morning)
issued at 748 am EDT Mon Oct 21 2019

A band of showers will work through the area today along and ahead
of an occluded/cold front. The showers will move in between 15z
and 18z and this will also result in a lowering of ceilings. After
18z, most sites will dip into the MVFR category for both ceilings
and visibilities as the rain moves through. There is an outside
chance at an isolated thunderstorm towards evening (22z-02z), but
the threat was too marginal to include at this time.

Winds will increase significantly this morning out of the
southeast, rising into the 15-30 knot range. Some gusts will push
towards 35 knots. Winds will shift to the south this evening and
decrease in speed (10-20 knots). Low level wind shear will be
present today with 60 knot winds out of the south-southeast at 3000ft.

Conditions will improve this evening in all areas as the rain
moves east and conditions trend quickly to VFR. There is the
potential late tonight for MVFR ceilings to be moving back into
far western lower toward mkg.

&&

Marine...
issued at 330 am EDT Mon Oct 21 2019

Another impactful marine/Lakeshore event is looming from today
through Tuesday night. A strong fall low pressure system will move
across Wisconsin placing our Lakeshore under a tight pressure
gradient for several forecast periods. We will leave the Gale
Warning as is from late this morning all the way through 800am on
Wednesday. The wind today will be of a warm air advection variety
with precipitation ongoing, so we may not realize all the wind that
is in the profile aloft. 60 knots is forecast at 3000ft, so plenty
of wind available.

The main event will occur from around 800pm this evening lasting
through tonight, Tuesday and into Tuesday night. The event looks
similar to the one last week in terms of wind speeds, so solid 40
knot gales. The difference will be wind direction. Last week was a
northwest to north-northwest wind event. This one is a southwest flow event. We often
think of our shoreline as a north/South Coast, but we indeed have an
irregular shore in spots. So, the portions of the shoreline that
faces southwest will be most in the line of fire. Those locations
are essentially areas north of Port Sheldon, but especially the
south sides of big and little Sable points. Ludington State Park
south through Epworth and Ludington will see an almost directly
onshore flow as will areas from the Little Sable Point light south
through Whitehall. Waves will build tonight and peak on Tuesday into
Tuesday evening in the 10-13 foot range.

This event has the potential to be a bit more impactful than the
last event which saw damage along our Lakeshore with debris strewn
on the beach in many areas. This event is a more onshore and of
longer duration. We are looking at likely dune and beach erosion,
flooding of low lying areas near the Lakeshore and waves that will
completely sweep across pier decks. Lake levels in terms of flooding
are only about 5 inches or so off the peak that occurred this
Summer. So we are still well above normal in regard to lake levels
at 581.58 feet as of a couple of days ago. The all time monthly mean
record is 582.35 feet. The High Lake levels combined with a storm
rise of probably 1 to 2 feet and battering waves on top of that in
an onshore flow leads to impactful conditions with loss of
dune/property likely.



&&

GRR watches/warnings/advisories...
Michigan...Lakeshore Flood Warning from 8 PM this evening to 8 am EDT
Wednesday for miz037-043-050-056-064-071.

Lm...Gale Warning from 11 am this morning to 8 am EDT Wednesday for
lmz844>849.

&&

$$

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