Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 231929

Area Forecast Discussion
National Weather Service Grand Rapids MI
329 PM EDT Mon Oct 23 2017

Synopsis/Short Term/Long Term/Marine

Issued at 328 PM EDT Mon Oct 23 2017

Low pressure moving north across Lower Michigan will continue to
bring heavy rain with some flooding expected through Tuesday. The
low will deepen on Tuesday and winds will be ramping up with some
strong wind gusts Tuesday and Tuesday night.


.SHORT TERM...(This evening through Wednesday night)
Issued at 328 PM EDT Mon Oct 23 2017

Heavy rain tonight into Tuesday and high winds Tuesday into
Tuesday night are the main forecast issues in the near term.

The Flood Watch was replaced with areal Flood Warning across the
western third of the forecast area and an areal Flood Advisory to
its east. The southeast zones are not expected to see flooding and
the watch was dropped there.

Surface low was centered just south of AZO at 330 PM and is moving
north with strong area of f-gen expected to continue producing
inch an hour rain rates across the warning area through the
evening. We have been fortunate that the bulk of the heaviest rain
has remained over Lake Michigan so far today, but amounts over 2
inches have occurred across parts of Ottawa, Muskegon, Oceana
Counties with a report of nearly 2.25 inches near Holland at 320
PM. The heavier rain is moving onshore and the HRRR has the f-gen
area pivoting across our northwest zones tonight.

So 3 to 5 inches of rain is possible in the warning area with
amounts of an inch or less across the southeast zones by Tuesday

The other issue we will have to deal with high winds on Tuesday as
the low rapidly deepens across northern Lower Michigan.
Tightening pressure gradient and strong cold advection will
combine to bring gusts to wind advisory criteria during the
morning across the northern coastal zones and by afternoon across
central and southern zones. We have issued a wind advisory for
this area. The winds will subside after midnight as the low pulls

.LONG TERM...(Thursday through Monday)
Issued at 328 PM EDT Mon Oct 23 2017

Main weather highlights in the long term period are a period of
milder and quieter weather Thursday into Friday, followed by more
cold air for the weekend through Halloween.

Quiet weather day expected for Thursday due to shortwave ridging in
between the exiting upper trough and the next one dropping into the
north central U.S.. Also milder temperatures expected on Thursday
with high temps 55 to 60 as warm advection strengthens in advance of
next approaching system. Friday may also be a mild day if the slower
ECMWF timing of the next cold front is correct.

Deep longwave trough is progged to impact the Great Lakes Region
next weekend, resulting in scattered showers with highs only in the
mid 40s. Some snow showers will be possible at night and in the
early morning when temperatures cool, especially inland from Lake MI
and in higher elevation areas. Any clearing at night could lead to
sub freezing temperatures.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1241 PM EDT Mon Oct 23 2017

Rain will continue to develop ahead of and along a frontal
boundary that was positioned roughly over Lake Michigan at 16Z.
Deteriorating conditions to IFR or low-end MVFR are expected for
west Michigan terminals as the frontal boundary slides east
during the afternoon and early evening, and as a low pressure
system rides northward along this feature. Rain will be fairly
steady through about the 00-02Z timeframe, then turn more showery
as the low lifts into northern Michigan. Northerly winds will also
turn westerly late this afternoon/early this evening as the low
lifts north, and becoming gusty. A showery pattern will continue
overnight, with additional moisture and energy giving a boost to
coverage and lowering ceilings once again early Tuesday morning.
Stronger winds look to develop late in the TAF period as daytime
mixing ensues, and look to become windier beyond the TAF period.


Issued at 328 PM EDT Mon Oct 23 2017

No significant changes to the previous forecast. Winds and waves
will be increasing tonight and gales are still expected to develop
on Tuesday. Northwest gales will probably begin during the
morning across areas north of Whitehall and during the afternoon
south of there.


Issued at 1211 PM EDT Mon Oct 23 2017

River levels are rising across the area. Rainfall of up to two
inches has fallen through this morning and another two to three
inches are possible through Tuesday. More rain is also possible
through the week. Warnings have been issued for Croton on the
Muskegon River, Rockford on the Rogue River, and Vicksburg on the
Portage River. More river warnings could be issued depending on the
amount of rain that falls and where it falls. Areal flood warnings
and watches are also in effect though Tuesday.


MI...Wind Advisory from 2 PM Tuesday to 3 AM EDT Wednesday for MIZ050-

     Wind Advisory from 8 AM Tuesday to 3 AM EDT Wednesday for MIZ037-

LM...Gale Watch from Tuesday morning through Wednesday morning for

     Small Craft Advisory until 10 AM EDT Tuesday for LMZ844>849.



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