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789
FXUS63 KGRR 220703
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
303 AM EDT Tue Aug 22 2017

LATEST UPDATE...
Synopsis/Short Term/Long Term/Marine

.SYNOPSIS...
Issued at 303 AM EDT Tue Aug 22 2017

A cold front will be passing through the area today. Along and ahead
of this cold front, a few showers and storms will be possible this
morning before coming to an end this afternoon. Severe weather is
not expected. Clearing will take place this afternoon, and cooler
air will come in on gusty Northwest winds.

Most of the rest of this week and the weekend will be mostly dry and
cooler. There is a chance of a few showers on Thursday as a strong
upper wave drops down through the area.

&&

.SHORT TERM...(Today through Thursday)
Issued at 303 AM EDT Tue Aug 22 2017

Rain amounts thus far with this event have been unimpressive in SW
Lower. The organized convection ongoing over IA, IL, and now IN
continue to limit the low level inflow ahead of the sfc cold front
that is now approaching Nrn Lake Michigan and extends down to the
Quad Cities area. SPC meso-analysis page indicates we are still
looking at 1000 j/kg of MU CAPE in place over the area ahead of the
front. A few showers have been forming, and these will continue to
be be possible until the front moves through today. The best chance
of rain will be across the far south where some of the better
convection could clip those areas.

We will clear out this afternoon as the dry slot moves over the
area. This also means we will see some gusty winds develop.

We will see upper troughing hold in over the area on Wed and
continue through Thu. Wed the flow is fairly laminar with a weak
short wave moving through just north of the area. We will see
diurnal cu develop inland, however it should be rather shallow with
the upper jet just north. The limited potential vertical development
will keep us from putting any rain chances in for Wed for now.

We are keeping rain chances in for Thu. The models are in fairly
decent agreement in dropping down a fairly significant short wave
through the area. This coming through around peak heating will allow
for better vertical development of the cu field, and allow for some
showers.

.LONG TERM...(Thursday night through Monday)
Issued at 303 AM EDT Tue Aug 22 2017

The latest runs of the ecmwf and gfs have thrown a huge wrench into
a generally straight forward forecast. Both models now develop a
tropical system in the northwest Gulf and move it inland and then
northeast toward either the Great Lakes (GFS) or the Ohio Valley
(ECMWF) late in the period.

Canadian high pressure will bring down chilly air Thursday night.
Most rural locations will see lows in the 40s and it`s possible the
colder locations over the northern cwa may see some 30s. As high
pressure drifts east, a slow warming trend will occur and temps will
climb into the lower to mid 70s, but lows will remain mainly in the
50s.

Chances for rain from Thursday night through Monday are fairly low,
A lot will depend on what, if anything, occurs with the potential
system in the Gulf, but even if it does develop, it`s probably not
going to impact southwest Lower until Tuesday at the earliest.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1246 AM EDT Tue Aug 22 2017

A strong cold front will move through the state mid morning. Prior
that that, showers and thunderstorms will be possible, especially
along the I-94 TAF sites. Skies will begin to clear from west to
east later in the morning as drier air works into the state.


&&

.MARINE...
Issued at 303 AM EDT Tue Aug 22 2017

We are still in line for a fairly decent wind/wave event for today,
that could last into Wednesday before subsiding. Good cold air
advection moving in over the relatively warm waters of Lake Michigan
will allow for waves to build efficiently today. Winds are expected
to come down slightly for Wed, but could still poise a hazard to
mariners and swimmers.

&&

.HYDROLOGY...
Issued at 305 PM EDT Mon Aug 21 2017

Area rivers are around normal levels for the time of the year and
well below bankfull. Though we are going to get localized heavy rain
of up to an inch tonight into Tuesday morning, most areas will not
see even minor river flooding. Some water covered roads are
possible. No significant precipitation is expected Wednesday through
Sunday, so any rises on rivers will have time to recover.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from 6 AM EDT this morning through this
     evening for MIZ037-043-050-056-064-071.

LM...Small Craft Advisory from 6 AM this morning to 6 PM EDT
     Wednesday for LMZ844>849.

&&

$$

SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...04
AVIATION...04
HYDROLOGY...63
MARINE...NJJ