Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 181202
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
702 AM 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 12Z TAFS through 12Z Thursday morning)
Issued at 702 AM EST Wed Jan 18 2017

IFR rules for the short term with ceilings below 1000 ft and
visibility`s in the 2 to 4 mile range. It would seem to me that
with surface high pressure moving into the area today and
increasingly dry air moving into the area the low clouds should
break up by late afternoon. The fog (mist really) should be gone
before noon.

So the big glitch is what happens tonight. The latest run of the
RAP model shows dense fog developing off shore of MKG by 21z and
then spreading inland by 00z and covering the entire CWA by 07Z.
The NAM12 shows something similar. What seems odd to me is that
there is 20 knots of wind below 1000 ft between 21z today and 06z
tonight. However I have to admit the wind really lets up after
that. So, if the low clouds do clear by evening, it may well be we
will get fog tonight. I did put it in all of the TAF forecasts.

&&

.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 151 PM EST Tue Jan 17 2017

Monday to Tuesday rain totaled 0.5 to 1.25 inches across the area.
Runoff into already swollen rivers will be efficient due to frozen
and saturated soil. Fortunately, warmer temperatures the rest of
the week will allow ice to melt and should eventually alleviate
the flooding situation at Robinson Township. The Looking Glass
river near Eagle and the Maple River near Maple Rapids are being
monitored for rises to Minor Flood Stage. Several other rivers
above bankfull are expected to rise but should have less
significant impacts to property. The next chances for rain will be
Friday and early next week.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory from 10 AM this morning to 1 AM EST
     Thursday for LMZ844>849.

&&

$$

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


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