Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 151128
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
628 AM EST Thu Feb 15 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 323 AM EST Thu Feb 15 2018

Fog and drizzle will persist this morning then rain showers will
move through this afternoon as low pressure tracks south of
Michigan. A cold front comes through tonight with rain showers
changing to snow showers. Colder weather with periods of snow
showers will continue into the weekend.

&&

.SHORT TERM...(Today through Saturday)
Issued at 323 AM EST Thu Feb 15 2018

Will keep the dense fog advisory as is for now, but we will watch
obs later this morning to see of it needs to be extended later.
Steadier showers moving in later this morning across the southern
half of the forecast area should help dissipate the dense fog.

Other forecast issue is timing change over as the steadier precip
ends tonight and transitions to lake effect snow showers Friday
morning. Not expecting much accums as inversion heights are around
5 kft then crash as sfc ridging builds in Friday afternoon.

Light snow with some lake enhancement expected Saturday afternoon
as northern stream shortwave trough approaches. Light accums are
possible.

.LONG TERM...(Saturday night through Wednesday)
Issued at 323 AM EST Thu Feb 15 2018

The models are coming into better agreement into the extended
periods, however there are still various timing issues.

A short wave crosses the CWA Saturday evening.  Once this passes the
snow will come to an end late Saturday night.  Accums will general
be under an inch, but localized two inches will be possible toward
the higher terrain in Central Lower.

A warming trend will begin Sunday night as a surface boundary moves
slowly into the Western Great Lakes.  Flow ahead of this system will
be southerly, bringing the warm air.  We should begin to see the
chance of pcpn late Sunday night or Monday morning.  If it arrives
early enough we could see light freezing rain at the onset,
otherwise rain should be the pcpn type.  Decent rains could occur
Monday afternoon and night as the surface boundary only sags through
slowly, being parallel to the upper flow, along with deep SW flow.

The timing differences really show up late into Tuesday/Wednesday as
to when the front finally moves through.  General consensus has it
pushing SE of the area on Tuesday, then turning colder Tuesday night
into Wednesday.  The steadiest rains should push off with the front,
then as the colder air returns the rain should switch to snow
Tuesday afternoon or Tuesday night.  Not an overly cold air mass, so
it looks doubtful we will see any lake enhancement to the snow, but
it should continue lightly into Wednesday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 628 AM EST Thu Feb 15 2018

IFR and LIFR conditions can be expected through 18Z across much of
southern Lower Michigan. Then IFR and MVFR will continue into the
evening and overnight. Winds will be southwest around 10 to 15
knots this morning and turn northwest around 10 knots tonight.

&&

.HYDROLOGY...
Issued at 1028 AM EST Wed Feb 14 2018

A warm up this week and up to a quarter inch of rain Thursday should
result in melting snow and ice, and rising river levels. This could
also result in shifting ice and additional ice jam formation.
Heavier rain and additional days with highs above freezing early
next week will lead to a greater concern for the possibility of
river flooding.

A flood advisory remains in effect for the Looking Glass River near
Eagle due to elevated levels of water/ice from an ice jam. River
levels in the vicinity of ice jams will continue to fluctuate by
several feet until the ice breaks free. An advisory has also been
issued for Sycamore Creek at Holt.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Dense Fog Advisory until 9 AM EST this morning for MIZ050-
     056>059-064>067-071>074.

LM...None.
&&

$$

SYNOPSIS...Ostuno
SHORT TERM...Ostuno
LONG TERM...JK
AVIATION...Ostuno
HYDROLOGY...63



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