Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 191716

Area Forecast Discussion
National Weather Service Grand Rapids MI
116 PM EDT Mon Mar 19 2018


Issued at 329 AM EDT Mon Mar 19 2018

I expect mostly dry conditions with slightly cooler than normal
temperatures through most of this week. There remains at least a
chance a storm system coming out of the Central Plains late in the
week could bring snow or mixed rain and snow to the area Saturday
but at this points a more southern track seems likely to keep
Southwest Michigan dry into the following week.


.SHORT TERM...(Today through Wednesday)
Issued at 329 AM EDT Mon Mar 19 2018

There area a few issues of note with this forecast. In the very
short term we have an area of mid clouds trailing the surface cold
front. The question is how quickly do those clouds mix out if in
fact they do mix out? Then we have the issue of the daily high
temperature, over the past few days our high temperatures have
been running several degrees warmer than the MOS forecast has
suggested. That is a sunshine over dry ground issue. So do we
continue to push the high temperature forecast above MOS the next
3 days? Finally there is the issue of precipitation. While this
would not seem to be much of an issue, The way there is a northern
stream wave digging behind a departing southern stream wave, some
phasing of the two waves is not out of the question. This would
suggest precipitation would be possible Wednesday during the day
near and south of I-96.

In the "Big Picture" we continue to see split flow through this
week. The southern stream is firmly anchored over the southern 1/3
of the CONUS and it will more than likely remain there for some
time to come. Similarly, the northern branch of the polar jet is
locked north of 65N. What this means we do not get very warm or
very cold in the next week or so. Also it would seem the longwave
troughs over over eastern and western CONUS through the week. That
would for the most part mean we are in general Northwest upper
flow, which would be dry for us this time of year.

As for the cloudiness issue. The GOES-16 Night Time Microphysics
loops show an nearly solid deck of mid clouds over most of Lower
Michigan with only the extreme southern sections and northern
sections being in the clear. This is related to the jet lift in
the right entrance region (jet core is northeast of northern Lake
Huron today). That suggests to me these clouds will be hard to mix
out. So, I am going with mostly cloudy becoming partly cloudy
today. I do think skies should be able to clear tonight as the jet
core has moved east by then.

A northern stream shortwave is digging into the Dakotas by
Tuesday. Meanwhile the southern stream wave will be near Indiana
and Ohio Tuesday. That is just close enough that phasing is not
out of the question. If that would happen we would see some light
precipitation Wednesday. For now I am not going to play in our
grids but we will have to watch this none the less.

I increased the high temperature 3 to 5 degrees over MOS today
through Wednesday due to the dry ground and sunshine issue. This
may be a problem today through if the mid clouds hold on into the

.LONG TERM...(Wednesday night through Sunday)
Issued at 329 AM EDT Mon Mar 19 2018

As the Eastern U.S. trough drifts east and more northwesterly upper
flow develop into Thursday.  High pressure over Central Canada oozes
down into the Western Great Lakes, keeping the region dry, with the
exception of a few flurries near the lake.

A Western U.S. upper trough should cause cyclogenesis over the
Central Plains by late Friday.  How it phases with an upper wave
over the Great Lakes through the weekend will be key to how strong
the system gets and where it ultimately heads.  It does appear to
develop more slowly and the pcpn should not reach SW MI until late
Friday into Saturday.  The latest model runs have trended a bit
farther south with the track of the surface low.  However it still
appears there will be strengthening FGEN over MI, so it still looks
like pcpn reaches this far north.  Some rain may move in initially,
but it still appears to be mainly a snow maker.  The best chances of
accumulation will be south of I-96, with the bulk of that occurring
on Saturday. A daytime snow this late in the season frequently will
only result in accums on grassy areas, while roads stay wet.  The
snow should wind down Saturday night.

Temps will be fairly uniform from mid week into the weekend.  Daily
highs will attempt to reach 40, while lows should be in the 20s.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 116 PM EDT Mon Mar 19 2018

Only real impact to aviation operations over the next 24 hours
will be wind gusts during the daylight hours. We expect wind gusts
up to around 25 knots until about 00z tonight, and then after 14z
on Tue once diurnal mixing gets going. A wind of around 10-12
knots will likely remain up through the night, with no gusts

Conditions should remain VFR at all sites. We can not rule out a
little bit of lake stratocumulus cloud cover coming from Lake
Huron with the NE flow. The air is so dry though that the clouds
should remain quite limited, if it happens at all.


Issued at 329 AM EDT Mon Mar 19 2018

Winds will be 15 to 25 knots but since they will be from the
northeast, we will not get waves high enough to issue a small
craft advisory.


Issued at 322 PM EDT Sat Mar 17 2018

The Portage River near Vicksburg will remain just above flood stage
through Thursday and then remain near flood stage through the
weekend. Otherwise, dry weather is expected through Friday.




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