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fxus63 kgrr 151112 
afdgrr

Area forecast discussion
National Weather Service Grand Rapids Michigan
712 am EDT sun Sep 15 2019

Latest update...
aviation

Synopsis...
issued at 310 am EDT sun Sep 15 2019

- showers and a few storms especially this morning.

- Hazardous swim/boating conditions today.

- Warming trend this week.

&&

Discussion...(today through next saturday)
issued at 310 am EDT sun Sep 15 2019

An area of showers and thunderstorms will cross the County Warning Area this
morning. Radar shows them in WI and Illinois headed east. So many areas
will see rain this morning. The low level jet responsible for the
precipitation does pull east of the County Warning Area this morning...which
should result in a decreasing trend to the precipitation for the
afternoon. Still...recent guidance does show an axis of
instability hanging back over the County Warning Area for the afternoon. The
surface wave will still be west of the area as of 18z this
afternoon. So...there is some potential for showers to redevelop
this afternoon with a low risk for a storm or two...perhaps into
the evening. We did increase this risk for a storm accordingly.

Low level moisture persists through the night and even into
Monday. At the same time the surface wave and 850/700 mb trough
tracks through. We could see some showers/drizzle depending on how
the setup evolves. Some pops were added/increased to account for
this.

A mainly dry period will be forecasted into Thursday along with
moderating temperatures. At this time not much forcing will be
around to support precipitation as temperatures moderate. By
Friday though some instability is shown to advect in from the
west. There is some uncertainty as to whether this axis of
instability will arrive as much of the forcing remains well west
of the County Warning Area. We will hold off on featuring the risk for storms
until Saturday when most of the guidance suggests an eastward push
of the low level jet.

&&

Aviation...(for the 12z tafs through 12z Monday morning)
issued at 708 am EDT sun Sep 15 2019

With some instability around to start the forecast period and a
wave of low pressure moving in from the west...showers and a few
storms were around the taf sites. These storms could persist for a
few hours this morning. This system is slow moving and that could
keep the showers going into the afternoon. Then as the moisture
increases...it appears the ceilings and eventually the
visibilities will be lowering. As we near midnight and beyond...it
is now looking like IFR clouds/fog and possibly lower conditions
will be developing. We therefore have added it to the forecast.




&&

Marine...
issued at 310 am EDT sun Sep 15 2019

Winds were increasing ahead of the approaching wave of low
pressure. Waves were building as well. Not much change planned for
The Hazards as the scenario has not changed much. Some gusty winds
may accompany the storms over the waters. Much less wind is
expected for Monday as the pressure gradient weakens.



&&

GRR watches/warnings/advisories...
Michigan...Beach hazards statement until 5 PM EDT this afternoon for miz037-
043-050-056-064-071.

Lm...Small Craft Advisory until 5 PM EDT this afternoon for
lmz844>849.

&&

$$

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