Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 122020
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
320 PM EST Sun Nov 12 2017

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

.SYNOPSIS...
Issued at 320 PM EST Sun Nov 12 2017

Mixed light rain and snow will come to and end this evening as high
pressure moves across the lake. The next chance of precipitation
will come Tuesday night and Wednesday when a cold front moves
through. Highs will be mostly in the 40s this week.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 320 PM EST Sun Nov 12 2017

Forecast concerns deal with pcpn trends tonight and again Tuesday
night.

Regional radar shows a large area of light rain over Il/In/Mi moving
east. The back edge of the pcpn is starting to move toward the
northern CHI suburbs. This pcpn is associated with an upper trough
moving across the Great Lakes and will come to an end this evening.
The pcpn may mix with some wet snow before ending. Cloudy skies are
expected after the pcpn ends. Omega profiles reveal little in the
way of lift in the cloud layer so chances for drizzle are low.

Monday and Tuesday will be dry as high pressure moves across the
cwa. Another cold front approaches late Tuesday and rain is expected
Tuesday night. Temperatures may be cold enough over the eastern cwa
for some wet snow to mix in with the rain.

.LONG TERM...(Wednesday through Sunday)
Issued at 320 PM EST Sun Nov 12 2017

Two systems will impact Michigan in the long term: One on Wednesday
then a stronger storm for next weekend. The storm next weekend
should have a little of everything from rain to wind to snow and
perhaps even some thunderstorms.

Models are in great agreement on the timing of the cold front on
Wednesday afternoon and show a high probability for rain showers
ahead of it in the morning with around 0.10 to 0.25 inch of QPF. The
cold advection behind the front could lead to a few rain and snow
showers, especially north of I-96, but the system is a fast mover
and high pressure will be building in for late Wednesday night and
Thursday.

Confidence is high that a significant, rapidly deepening, low
pressure system will impact the Great Lakes Region next weekend.
However some timing differences exist with the GFS faster than the
ECMWF. Prefer the EC ensemble mean for now, which tracks the sfc low
through southeast Wisconsin on Friday night then deepens it rapidly
on Saturday as it crosses the Straits of Mackinac then heads into
Ontario.

This track and timing supports a round of warm advection showers and
possible tstms Friday afternoon through Saturday morning, followed
by rain showers changing to snow showers and increasing westerly
winds Saturday afternoon. Wouldn`t be surprised if we had some gusts
to 50 mph. Lake effect snow showers are expected Saturday night into
Sunday, although this system is progged to eject quickly northeast
into Quebec which implies they wouldn`t last too long.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 105 PM EST Sun Nov 12 2017

IFR conditions will become more widespread this afternoon as rain
mixed with snow continues. LIFR is possible as well, particularly
south and east of GRR.

There is also a risk of the mixed precipitation changing to
predominately snow after 21Z for a few hours before ending which
would result in reduced vsbys. Moderate icing in the clouds can
expected with freezing levels at, or falling to, around 1000-1500
ft.

Considerable IFR/LIFR will probably linger tonight after the
precipitation ends, especially south and east of GRR. Improvement
to MVFR is expected on Monday, with the slowest improvement
around JXN.

The exception to all of this will be at MKG where dry conditions
are prevailing, although MVFR cigs are still likely here.


&&

.MARINE...
Issued at 320 PM EST Sun Nov 12 2017

Wind will be relatively light during the next 24 hours as high
pressure moves over the lake.

&&

.HYDROLOGY...
Issued at 138 PM EST Sun Nov 12 2017

Precipitation totals of 0.2 inches or less Sunday will have little
effect on rivers, which are running near to above normal for mid-
November. Another quarter inch on Wednesday will keep the ground
soggy. A Fall storm system may produce rainfall totals between 0.5
and 1 inch Friday into Saturday, which would cause river levels to
rise again.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...Meade
AVIATION...Meade
HYDROLOGY...CAS
MARINE...04



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