Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 301803
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
203 PM EDT FRI SEP 30 2016

LATEST UPDATE...
Long Term/Aviation

.SYNOPSIS...
Issued at 315 AM EDT Fri Sep 30 2016

Low pressure will slowly spin across Lower Michigan bringing wet
weather through the weekend. Fair weather will finally arrive
early next week as the low finally moves away.

&&

.UPDATE...
Issued at 1102 AM EDT Fri Sep 30 2016

We have cancelled the flood watch this morning. Rain amounts last
night we not all that impressive, and did not really cause any
additional issues, especially for the areas hit hardest the night
before. Additional rain showers are likely, with the next wave
moving through later this afternoon. Areas of rain showers should
be fairly progressive in nature with the short waves moving around
the center of the upper low.

We believe that the worst case scenario at this time is that an
areal flood advisory may be needed if rain showers become too much
of a problem. We do not believe that it would rise to the level
where an areal flood warning would be needed.

&&

.SHORT TERM...(Today through Sunday)
Issued at 315 AM EDT Fri Sep 30 2016

No changes to the Flood Watch. Current radar loop shows steadier
rain moving into the SE forecast area with long fetch of moisture
streaming in as the upper cutoff low spins across the Ohio Valley.
It is forecast to move north back into Lower Michigan by the end
of the period then finally get kicked east as longwave trough
moves into the western CONUS.

Expect rains to continue this afternoon and into tonight and
persist into Friday before beginning to taper off as the occluded
low moves into the forecast area. Marginally steep lapse rates
this afternoon makes diurnal enhancement of thunderstorms
possible. The persistent nature of the flow regime and the
presence of tropical moisture feeding in will mean that excessive
rains are possible and the Flood Watch will remain in effect.

.LONG TERM...(Monday through Friday)
Issued at 202 PM EDT Fri Sep 30 2016

Our next significant weather event will be Wednesday night into
Thursday as the next Pacific system moves across the CONUS. This
looks better today than in previous runs and I could see
thunderstorms on Thursday during the day. Otherwise clearing
slowly on Monday, very nice with sunshine Tue into Wed and
lingering showers Friday as the cold air moves in behind the
system.

We get two systems to impacted by the "Henry rule" yet. The first
one is the one currently over us, it finally gets booted east by
the first upstream Pacific system as it moves into the Rockies.
The creates what almost looks like an omega block over the CONUS
by Tuesday as the Pacific system majorly digs and closes off an
upper low over the central Rockies, building a large upstream
upper high over the Great Lakes. However the next Pacific system
gets to close and Henry Rules that east. The first Pacific system
seems to go nearly negative tilt as it comes into the Great Lakes.
This could bring thunderstorms Thursday. With such a deep trough
we will not see a quick clearly Friday, but cold air, lake
enhanced rain showers.

So, that this means for us in Southwest Michigan is a slow
clearing of the low clouds Monday, then mostly sunny / mostly
clear Tuesday into early evening Wednesday with warming high
temperatures. Highs near 80 are not out of the question (not
actually in the grids yet) Wednesday. Then the system moves
through Thursday with showers and scattered thunderstorms Thursday
but it will still be warmer than normal. The cold air moves back
in Friday with lake enhanced rain showers.


&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 202 PM EDT Fri Sep 30 2016

Our closed upper low will continue to brings periods of showers to
the area through most of Saturday. With extensive low ceilings I
do not see thunderstorms as threat even through we do get better
mid level instability later today into Saturday. Winds are
expected to slowly decrease into Saturday so that may encourage
lower ceiling and thicker fog Saturday morning that would not be
to quick to lift during the mid to late morning.

&&

.MARINE...
Issued at 315 AM EDT Fri Sep 30 2016

Winds and waves will continue to be hazardous to small craft
into this evening. Conditions will slowly improve tonight but the
small craft advisory may be needed to continue through tonight as
the pressure gradient continues to generate wind gusts to 25
knots. Waves will be highest further away from shore because of
the offshore component of the wind.


&&

.HYDROLOGY...
Issued at 1109 AM EDT Fri Sep 30 2016

The Sycamore Creek is nearing its crest over a foot above
bankfull, and will begin its slow recession which may modulated
by any additional rainfall Friday into Saturday. Other rivers
approaching bankfull the next few days include the Red Cedar above
Williamston, the Looking Glass near Eagle, and the Grand at Ionia.
The current forecasts are dependent on roughly another 0.75 inches
falling in those basins through Saturday morning. Will hold off
on flood advisories for those rivers until confidence is higher.

&&

.GRR Watches/Warnings/Advisories...
MI...None.
LM...Small Craft Advisory until 6 PM EDT this evening for LMZ844>849.

&&

$$

UPDATE...NJJ
SYNOPSIS...Ostuno
SHORT TERM...Ostuno
LONG TERM...WDM
AVIATION...WDM
HYDROLOGY...CAS
MARINE...Ostuno


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