Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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702
FXUS63 KGRR 220818
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
318 AM EST Mon Jan 22 2018

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

.SYNOPSIS...
Issued at 304 AM EST Mon Jan 22 2018

A storm system will track through the region today and into
tonight...bringing rain and even a few thunderstorms to the area.
As the storm pulls away on Tuesday...any remaining rain will
change to snow...especially in the afternoon. An area of high
pressure will move in for the middle part of the week leading to
mostly dry weather.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 304 AM EST Mon Jan 22 2018

Models are in reasonable agreement in showing a deepening area of
low pressure tracking northeastward through the Great Lakes Region
Today and into Tonight. This system will be rather dynamic with a
favorable coupled upper level jet. The combination of strong lift
and a very moist airmass with pwat values well over 200 percent
above normal will support widespread rain...especially this
morning. There could even be a few thunderstorms as elevated
instability will advect in from the southwest this morning and is
then forecasted to persist for the afternoon. Will maintain the
high pops and show a northeastward progression of the thunderstorm
risk today. Will keep the dense fog advisory going til 7 am...and
may need to extend it depending on how the showers moving in
impacts the thicker fog.

A mid level dry slot moves in from the southwest this afternoon
and evening. Will lower the pops into the evening as a result.
There is still some uncertainty as to how quickly we transition
over to snow and how much precipitation will be around. The latest
trend supports a slower transition. Will trend the forecast this
way. There is still a risk for snow related impacts on
Tuesday...with the High Res Euro trying to lower surface
temperatures below freezing in the afternoon.

.LONG TERM...(Wednesday night through Sunday)
Issued at 304 AM EST Mon Jan 22 2018

There may be a few snow showers along the lake shore at the start of
the long term, but they won`t last long. H8 temps are marginal at
best and will begin to warm Wednesday night. A upper ridge will
quickly build into the Great Lakes and we`ll see a couple of dry
days.

A cold front will move across the state Friday night. Dynamics with
this front are fairly weak as the supporting sfc low is well north
in Ontario and the trailing upper trough if mostly diffuse. Moisture
pooling along the front may lead to some rain showers Friday night
and Saturday and a few rain showers associated with the upper trough
Saturday night into Sunday will mix with and then turn to light snow
showers as colder air flows in behind the departing cold front. This
system doesn`t look like a big pcpn producer.

Friday and Saturday will be the warmest days when temperatures climb
into the 40s. Otherwise, highs will be in the mid 30s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1153 PM EST Sun Jan 21 2018

IFR conditions will persist through at least 20z for the southern
taf sites and much of the period for the northern sites. There
will be some wind shear below 2k ft from 18-22z, but likely not
greater than 30 knots so it was not included in the tafs. We could
see a thunderstorm toward morning near I-94 so a vcts was retained
at those taf sites.


&&

.HYDROLOGY...
Issued at 214 PM EST Sun Jan 21 2018

A complete melting of the natural snowpack is expected by Monday
in the Grand, Kalamazoo, and Muskegon river basins. This will
release a quarter to perhaps half inch of water. Rain totals on
Monday will mostly range between 0.6 and 1.2 inches (ECMWF and
ensemble have been consistently lower than GFS and ensemble).
Depth of frozen soil varies but overall expect the ground to
remain frozen enough to allow efficient runoff.

A number of river forecast points will likely rise above bankfull
in the upcoming week. There is a chance of minor flood stage being
reached at a few sites (of earliest concern are Holt and Eagle),
particularly if higher rainfall totals verify. A breakup of river
ice is expected, and any ice jams that form can cause
unpredictable fluctuations in water levels. Road closures are
possible in low spots near river banks. Water could also approach
buildings in flood prone areas.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Dense Fog Advisory until 7 AM EST this morning for MIZ064>067-
     071>074.

LM...None.
&&

$$

SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...04
AVIATION...04
HYDROLOGY...CAS



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