Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 162333
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
733 PM EDT Mon Apr 16 2018

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 320 PM EDT Mon Apr 16 2018

Low pressure that dumped sleet and freezing rain on southwest Lower
Michigan will slowly move away from the region tonight and Tuesday.
A brief period of dry weather will develop before another round of
rain and snow moves into the picture late Wednesday into Thursday.

Temperatures will remain cold for this time of year but begin warming
by the end of the week. We`ll be in the 50s over the weekend.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 320 PM EDT Mon Apr 16 2018

Forecast concerns deal with lingering light snow tonight and then
the approach of the next system Wednesday.

Regional radar shows light snow falling over the state and this
should continue off and on tonight. The surface low that produced
the strong winds and sleet/ice has moved to Ontario. However, the
upper low will linger for another day or so and snow showers can be
expected tonight before diminishing Tuesday.

A narrow ridge between the departing low and the next system will
move across the state Tuesday night. A low in Kansas will move
across the cwa Wednesday. Some warmer air will move north into the
state and light rain will develop late in the day.

Temperatures will remain cold through Tuesday as highs tomorrow will
struggle to reach the mid 30s. However, temperatures will warm into
the mid 40s Wednesday.

.LONG TERM...(Wednesday night through Monday)
Issued at 320 PM EDT Mon Apr 16 2018

Fairly high confidence with the track and timing and even QPF
amounts for the sfc low that tracks just south of Lower Michigan on
Wednesday night. The only issue to be determined is precip type. We
went for rain mixing with then changing to snow but accums are
forecast to be less than an inch.

The warmer GFS was eschewed for the cooler NAM, and Superblend temps
and dew points were lowered accordingly. NAM forecast soundings show
rain changing to snow from north to south during the night, with
snow expected to be the dominant precip type across the forecast
area by 12Z Thursday as low level cold advection and diurnal cooling
occurs overnight. Even so, thermal profiles are marginal as is the
saturation of the DGZ, so snow rates should not be heavy enough to
produce travel impacts.

This is a quick moving, progressive low which moves east and gets
absorbed into a larger scaler upper low across eastern Canada by
Thursday afternoon. So we expect the precip to wind down during the
morning and sfc ridging to build in with fair weather into early
next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 729 PM EDT Mon Apr 16 2018

Overall the pattern is still looking like continued MVFR
conditions for the period. Local snow showers could temporarily
lower conditions. A few patches of VFR weather existed...mostly
north of KGRR. Given the NW flow...these could drop down through
the TAF sites over the next couple of hours. Later in the day on
Tuesday...after 21z...there is some potential for the lower clouds
to scatter out. I was not confident enough to feature that in the
forecast at this time.

&&

.MARINE...
Issued at 320 PM EDT Mon Apr 16 2018

No changes to the marine headlines. Winds will gust to 30 knots
tonight before diminishing Tuesday. Waves will remain in the 5 to 10
foot range tonight before decreasing Tuesday.


&&

.HYDROLOGY...
Issued at 1138 AM EDT Mon Apr 16 2018

River levels are above normal in Southern Lower Michigan and around
normal in Central Lower Michigan. The significant precipitation over
the weekend has led to rising river levels across the area.
Continued rises are expected for the next several days. Minor
flooding near river banks is possible.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 8 PM EDT Tuesday for LMZ844>849.

&&

$$

SYNOPSIS...04
SHORT TERM...04
LONG TERM...Ostuno
AVIATION...MJS
HYDROLOGY...63
MARINE...04



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