Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 181739
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1239 PM EST Wed Jan 18 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 329 AM EST Wed Jan 18 2017

The system that brought all the rain yesterday is moving out of
the area today. That will lead to decreasing clouds by afternoon
and warmer afternoon temperatures. Skies should clear tonight as
high pressure builds into the area. The surface high will bring
mostly sunny skies to the area Thursday. A system from the western
Gulf of Mexico will head our way for Friday morning bringing rain
with it. That moves out of the way by Saturday morning only to
have yet another system to follow it for late in the weekend into
early next week. Temperatures will be well above normal into the
middle of next week.

&&

.SHORT TERM...(Today through Friday)
Issued at 329 AM EST Wed Jan 18 2017

I see to major issues with this forecast. For today the issue when
does the sky clear off, given all the dry air at all levels and
surface ridging moving in, it seems nearly assured we will be
seeing sunshine before the sun sets this afternoon, at least over
the western and central CWA. The other issue is the storm on
Friday, that seems like a near for sure rain event too.

We have one of those East Asian Jet cores crossing the Dateline
today (180 to 200 knots 35N). This will boot the closed upper low
over the Southwest CONUS northeast into the western Great Lakes by
early Friday. The system goes negative tilt as it shears out ahead
of that system which by then will be coming on shore into
California. The negative tilt will nearly assure us of strong deep
lift with Gulf moisture. If it can`t rain from that set up, it
will never rain here.  Precipitable water values are more than 2
standard deviations from normal Friday morning in our area. So I am
99.9% sure we will see significant rainfall here Friday morning
(likely more than we are forecasting). With all that southerly
flow no question this will all be rain!

.LONG TERM...(Friday night through Tuesday)
Issued at 329 AM EST Wed Jan 18 2017

Daytime temperatures will be about 20 degrees above normal for the
weekend, with highs in the upper 40s to lower 50s both Saturday and
Sunday.  This will all be courtesy of a stacked upper low that will
be over the Northern Plains, causing deep southerly flow over the
Great Lakes.  Can`t rule out a few random rain showers Friday night
and Saturday, but it should largely be dry.  Then as another low
develops over the Gulf Coast states and moves closer, shower chances
should increase Saturday night.

The Gulf low is progged to drift slowly north, to OH by Monday
night.  This should lead to a persistent rain that should peak Monday
into Monday evening.  As this system approaches it should also
slowly drag in slight cooler air.  Monday/Tuesday should still be
well above normal, but highs should slip into the low and mid 40s.

It appears snow lovers will need to wait until at least the middle
of next week to see any flakes.  At this point it appears most areas
should see some snow return around or about Wednesday night.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1239 PM EST Wed Jan 18 2017

We are looking at another forecast period with IFR and lower
conditions expected most of the time. There is some good hope that
the IFR will finally diminish later Thu morning.

LIFR conditions prevail across most of the terminals early this
afternoon. There has been some slight improvement with temps
warming a couple of degrees, but additional improvement looks to
be limited. We can not rule out a couple of sites going MVFR for a
short time this afternoon. This is due to the low level moisture
remaining in place, and also upstream of the area across Illinois.
Cigs are expected to lower a bit a few hours after sunset as
temps cool a little.

Conditions will likely go down to VLIFR late tonight and
tomorrow morning as winds become a bit lighter. We should be able
to mix out/push out the shallow low level moisture on Thu morning.
We expect all sites to be VFR by 18z Thu.

&&

.MARINE...
Issued at 329 AM EST Wed Jan 18 2017

There is just enough pressure gradient to give us 15 to 25 knot
winds this afternoon and evening in the near shore waters so I
issued a SCA for that time period.


&&

.HYDROLOGY...
Issued at 1210 PM EST Wed Jan 18 2017

The Grand River at Robinson Twp is rising after Mon/Tue`s inch of
rain and a continued restriction of waterflow due to ice. Most
other rivers are rising due to the recent rain but seem to have
less notable ice impacts now. Temperatures (and dew points) will
be above 32 degrees for much of the next 7 days, with highs around
50 possible Sat/Sun. Melting river ice should eventually break
up, at which time flooding at Robinson Twp would likely alleviate.
Nonetheless, rivers across the area, especially in the greater
Grand basin and lower Kalamazoo basin, continue to run high due to
above- normal liquid precipitation this month. A quarter to half
inch of rain on Friday won`t make matters much worse, but it won`t
help either. Low-land flooding near riverbanks is occurring at
multiple forecast points, but impacts to property are not too out
of the ordinary. The Maple River near Maple Rapids will approach
Minor Flood Stage this weekend.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 1 AM EST Thursday for LMZ844>849.

&&

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...JK
AVIATION...NJJ
HYDROLOGY...CAS
MARINE...WDM



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